1
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Regnell O, Tesson SM. Total mercury and methylmercury in lake water in years before and after removal of mercury-polluted pulp fiber sediment. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2024; 362:125011. [PMID: 39313123 DOI: 10.1016/j.envpol.2024.125011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2024] [Revised: 09/17/2024] [Accepted: 09/20/2024] [Indexed: 09/25/2024]
Abstract
There is an elevated presence of mercury (Hg) in the biosphere because of anthropogenic activities. The resulting damage to ecosystems and human health increases dramatically when microorganisms produce highly toxic methylmercury (MeHg). Total Hg (THg), MeHg and ancillary water chemistry were measured in two connected lakes, separated by a short stream stretch, before (1996, 1998 and 2003) and after (2007, 2009 and 2010) the removal of Hg-polluted pulp fiber sediment. Over the study period, there was a decrease in sulfate in the surface water of both lakes, presumably because of declining atmospheric sulfate deposition. Together, the reductions in OM, sulfate, and Hg, resulted in decreased MeHg concentrations as well as decreased MeHg:THg ratios in the bottom water overlying the sediment. There was also a reduction in zooplankton MeHg and fish total Hg in both lakes. Multiple regressions, using the bottom water data before and after remediation from both lakes, indicated that both the yearly maximum MeHg concentration [MeHgmax] and MeHgmax:THg correlated positively with the simultaneously measured sulfate deficit (a proxy for microbial sulfate reduction) and inorganic Hg concentration (IHg = THg - MeHg). This may suggest that the removal of Hg and the decreased sulfate reduction not only led to a decrease in available Hg substrate for methylation but also disfavored the Hg methylation process. As opposed to sulfate deficit, other measurements reflecting heterotrophic microbial activity such as inorganic carbon (IC), ammonium (NH4+), and iron (Fe) did not show significant correlations with MeHg or MeHg:THg when the data from both lakes were combined.
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Affiliation(s)
- Olof Regnell
- Department of Biology/Aquatic Ecology, Lund University, SE-223 62, Lund, Sweden.
| | - SylvieV M Tesson
- Department of Biology/Aquatic Ecology, Lund University, SE-223 62, Lund, Sweden
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2
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Boie F, Ducey TF, Xing Y, Wang J, Rinklebe J. Field-aged rice hull biochar stimulated the methylation of mercury and altered the microbial community in a paddy soil under controlled redox condition changes. JOURNAL OF HAZARDOUS MATERIALS 2024; 472:134446. [PMID: 38696958 DOI: 10.1016/j.jhazmat.2024.134446] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2024] [Revised: 03/25/2024] [Accepted: 04/25/2024] [Indexed: 05/04/2024]
Abstract
Mercury (Hg) contaminated paddy soils are hot spots for methylmercury (MeHg) which can enter the food chain via rice plants causing high risks for human health. Biochar can immobilize Hg and reduce plant uptake of MeHg. However, the effects of biochar on the microbial community and Hg (de)methylation under dynamic redox conditions in paddy soils are unclear. Therefore, we determined the microbial community in an Hg contaminated paddy soil non-treated and treated with rice hull biochar under controlled redox conditions (< 0 mV to 600 mV) using a biogeochemical microcosm system. Hg methylation exceeded demethylation in the biochar-treated soil. The aromatic hydrocarbon degraders Phenylobacterium and Novosphingobium provided electron donors stimulating Hg methylation. MeHg demethylation exceeded methylation in the non-treated soil and was associated with lower available organic matter. Actinobacteria were involved in MeHg demethylation and interlinked with nitrifying bacteria and nitrogen-fixing genus Hyphomicrobium. Microbial assemblages seem more important than single species in Hg transformation. For future directions, the demethylation potential of Hyphomicrobium assemblages and other nitrogen-fixing bacteria should be elucidated. Additionally, different organic matter inputs on paddy soils under constant and dynamic redox conditions could unravel the relationship between Hg (de)methylation, microbial carbon utilization and nitrogen cycling.
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Affiliation(s)
- Felizitas Boie
- University of Wuppertal, School of Architecture and Civil Engineering, Institute of Foundation Engineering, Water and Waste Management, Laboratory of Soil and Groundwater Management, Pauluskirchstraße 7, 42285 Wuppertal, Germany
| | - Thomas F Ducey
- US Department of Agriculture, Coastal Plains Soil, Water, Plant Research Center, 2611 West Lucas Street, Florence, SC, USA
| | - Ying Xing
- University of Wuppertal, School of Architecture and Civil Engineering, Institute of Foundation Engineering, Water and Waste Management, Laboratory of Soil and Groundwater Management, Pauluskirchstraße 7, 42285 Wuppertal, Germany; School of Chemistry and Materials Science, Guizhou Normal University, Guiyang 550002, PR China
| | - Jianxu Wang
- University of Wuppertal, School of Architecture and Civil Engineering, Institute of Foundation Engineering, Water and Waste Management, Laboratory of Soil and Groundwater Management, Pauluskirchstraße 7, 42285 Wuppertal, Germany; State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, 550082 Guiyang, P.R. China
| | - Jörg Rinklebe
- University of Wuppertal, School of Architecture and Civil Engineering, Institute of Foundation Engineering, Water and Waste Management, Laboratory of Soil and Groundwater Management, Pauluskirchstraße 7, 42285 Wuppertal, Germany.
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3
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Scuvée D, Goñi-Urriza M, Tessier E, Gassie C, Ranchou-Peyruse M, Amouroux D, Guyoneaud R, Khalfaoui-Hassani B. Molybdate inhibits mercury methylation capacity of Pseudodesulfovibrio hydrargyri BerOc1 regardless of the growth metabolism. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2024; 31:42686-42697. [PMID: 38878247 DOI: 10.1007/s11356-024-33901-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2024] [Accepted: 05/31/2024] [Indexed: 07/04/2024]
Abstract
Molybdate inhibits sulfate respiration in sulfate-reducing bacteria (SRB). It is used as an inhibitor to indirectly evaluate the role of SRB in mercury methylation in the environment. Here, the SRB Pseudodesulfovibrio hydrargyri BerOc1 was used to assess the effect of molybdate on cell growth and mercury methylation under various metabolic conditions. Geobacter sulfurreducens PCA was used as the non-SRB counterpart strain with the ability to methylate mercury. While PCA growth and methylation are not affected by molybdate, 1 mM of molybdate inhibits BerOc1 growth under sulfate respiration (50% inhibition) but also under fumarate respiration (complete inhibition). Even more surprising, mercury methylation of BerOc1 is totally inhibited at 0.1 mM of molybdate when grown under sulfate or fumarate respiration with pyruvate as the electron donor. As molybdate is expected to reduce cellular ATP level, the lower Hg methylation observed with pyruvate could be the consequence of lower energy production. Although molybdate alters the expression of hgcA (mercury methylation marker) and sat (involved in sulfate reduction and molybdate sensitivity) in a metabolism-dependent manner, no relationship with mercury methylation rates could be found. Our results show, for the first time, a specific mercury methylation inhibition by molybdate in SRB.
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Affiliation(s)
- Diva Scuvée
- Université de Pau et des Pays de l'Adour, E2S UPPA, CNRS, IPREM, Pau, France
| | - Marisol Goñi-Urriza
- Université de Pau et des Pays de l'Adour, E2S UPPA, CNRS, IPREM, Pau, France
| | - Emmanuel Tessier
- Université de Pau et des Pays de l'Adour, E2S UPPA, CNRS, IPREM, Pau, France
| | - Claire Gassie
- Université de Pau et des Pays de l'Adour, E2S UPPA, CNRS, IPREM, Pau, France
| | | | - David Amouroux
- Université de Pau et des Pays de l'Adour, E2S UPPA, CNRS, IPREM, Pau, France
| | - Rémy Guyoneaud
- Université de Pau et des Pays de l'Adour, E2S UPPA, CNRS, IPREM, Pau, France
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4
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Lawruk-Desjardins C, Storck V, Ponton DE, Amyot M, Walsh DA. A genome catalogue of mercury-methylating bacteria and archaea from sediments of a boreal river facing human disturbances. Environ Microbiol 2024; 26:e16669. [PMID: 38922750 DOI: 10.1111/1462-2920.16669] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Accepted: 05/23/2024] [Indexed: 06/28/2024]
Abstract
Methyl mercury, a toxic compound, is produced by anaerobic microbes and magnifies in aquatic food webs, affecting the health of animals and humans. The exploration of mercury methylators based on genomes is still limited, especially in the context of river ecosystems. To address this knowledge gap, we developed a genome catalogue of potential mercury-methylating microorganisms. This was based on the presence of hgcAB from the sediments of a river affected by two run-of-river hydroelectric dams, logging activities and a wildfire. Through the use of genome-resolved metagenomics, we discovered a unique and diverse group of mercury methylators. These were dominated by members of the metabolically versatile Bacteroidota and were particularly rich in microbes that ferment butyrate. By comparing the diversity and abundance of mercury methylators between sites subjected to different disturbances, we found that ongoing disturbances, such as the input of organic matter related to logging activities, were particularly conducive to the establishment of a mercury-methylating niche. Finally, to gain a deeper understanding of the environmental factors that shape the diversity of mercury methylators, we compared the mercury-methylating genome catalogue with the broader microbial community. The results suggest that mercury methylators respond to environmental conditions in a manner similar to the overall microbial community. Therefore, it is crucial to interpret the diversity and abundance of mercury methylators within their specific ecological context.
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Affiliation(s)
| | - Veronika Storck
- Department of Biology, Concordia University, Montreal, Quebec, Canada
- Département de sciences biologiques, Université de Montréal, Montreal, Quebec, Canada
| | - Dominic E Ponton
- Département de sciences biologiques, Université de Montréal, Montreal, Quebec, Canada
| | - Marc Amyot
- Département de sciences biologiques, Université de Montréal, Montreal, Quebec, Canada
| | - David A Walsh
- Department of Biology, Concordia University, Montreal, Quebec, Canada
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5
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Zhong H, Tang W, Li Z, Sonne C, Lam SS, Zhang X, Kwon SY, Rinklebe J, Nunes LM, Yu RQ, Gu B, Hintelmann H, Tsui MTK, Zhao J, Zhou XQ, Wu M, Liu B, Hao Y, Chen L, Zhang B, Tan W, Zhang XX, Ren H, Liu YR. Soil Geobacteraceae are the key predictors of neurotoxic methylmercury bioaccumulation in rice. NATURE FOOD 2024; 5:301-311. [PMID: 38605129 DOI: 10.1038/s43016-024-00954-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/29/2022] [Accepted: 03/05/2024] [Indexed: 04/13/2024]
Abstract
Contamination of rice by the potent neurotoxin methylmercury (MeHg) originates from microbe-mediated Hg methylation in soils. However, the high diversity of Hg methylating microorganisms in soils hinders the prediction of MeHg formation and challenges the mitigation of MeHg bioaccumulation via regulating soil microbiomes. Here we explored the roles of various cropland microbial communities in MeHg formation in the potentials leading to MeHg accumulation in rice and reveal that Geobacteraceae are the key predictors of MeHg bioaccumulation in paddy soil systems. We characterized Hg methylating microorganisms from 67 cropland ecosystems across 3,600 latitudinal kilometres. The simulations of a rice-paddy biogeochemical model show that MeHg accumulation in rice is 1.3-1.7-fold more sensitive to changes in the relative abundance of Geobacteraceae compared to Hg input, which is recognized as the primary parameter in controlling MeHg exposure. These findings open up a window to predict MeHg formation and accumulation in human food webs, enabling more efficient mitigation of risks to human health through regulations of key soil microbiomes.
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Affiliation(s)
- Huan Zhong
- School of the Environment, Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing, China.
- Environmental and Life Sciences Program (EnLS), Trent University, Peterborough, Ontario, Canada.
| | - Wenli Tang
- School of the Environment, Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing, China
| | - Zizhu Li
- School of the Environment, Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing, China
| | - Christian Sonne
- Department of Ecoscience, Aarhus University, Roskilde, Denmark.
- Sustainability Cluster, School of Engineering, University of Petroleum and Energy Studies, Dehradun, India.
| | - Su Shiung Lam
- Higher Institution Centre of Excellence (HICoE), Institute of Tropical Aquaculture and Fisheries (AKUATROP), Universiti Malaysia Terengganu, Kuala Nerus, Malaysia
- Center for Global Health Research (CGHR), Saveetha Medical College, Saveetha Institute of Medical and Technical Sciences (SIMATS), Saveetha University, Chennai, India
| | - Xiao Zhang
- School of the Environment, Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing, China
| | - Sae Yun Kwon
- Division of Environmental Science and Engineering, Pohang University of Science and Technology, Pohang, South Korea
| | - Jörg Rinklebe
- School of Architecture and Civil Engineering, Institute of Foundation Engineering, Water and Waste Management, Laboratory of Soil and Groundwater Management, University of Wuppertal, Wuppertal, Germany
| | - Luís M Nunes
- Faculty of Sciences and Technology, Civil Engineering Research and Innovation for Sustainability Center, University of Algarve, Faro, Portugal
| | - Ri-Qing Yu
- Department of Biology, Center for Environment, Biodiversity and Conservation, The University of Texas at Tyler, Tyler, TX, USA
| | - Baohua Gu
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - Holger Hintelmann
- Department of Chemistry, Trent University, Peterborough, Ontario, Canada
| | - Martin Tsz-Ki Tsui
- School of Life Sciences, Earth and Environmental Sciences Programme, Institute of Environment, Energy and Sustainability, The Chinese University of Hong Kong, Hong Kong SAR, China
- State Key Laboratory of Marine Pollution, City University of Hong Kong, Hong Kong SAR, China
| | - Jiating Zhao
- Department of Environmental Science, Zhejiang University, Hangzhou, China
| | - Xin-Quan Zhou
- National Key Laboratory of Agricultural Microbiology and College of Resources and Environment, Huazhong Agricultural University, Wuhan, China
| | - Mengjie Wu
- School of the Environment, Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing, China
| | - Beibei Liu
- School of the Environment, Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing, China
| | - Yunyun Hao
- National Key Laboratory of Agricultural Microbiology and College of Resources and Environment, Huazhong Agricultural University, Wuhan, China
| | - Long Chen
- Key Laboratory of Geographic Information Science (Ministry of Education), School of Geographic Sciences, East China Normal University, Shanghai, China.
| | - Baogang Zhang
- School of Water Resources and Environment, MOE Key Laboratory of Groundwater Circulation and Environmental Evolution, China University of Geosciences (Beijing), Beijing, China
| | - Wenfeng Tan
- National Key Laboratory of Agricultural Microbiology and College of Resources and Environment, Huazhong Agricultural University, Wuhan, China
| | - Xu-Xiang Zhang
- School of the Environment, Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing, China
| | - Hongqiang Ren
- School of the Environment, Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing, China
| | - Yu-Rong Liu
- National Key Laboratory of Agricultural Microbiology and College of Resources and Environment, Huazhong Agricultural University, Wuhan, China.
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6
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Peng X, Yang Y, Yang S, Li L, Song L. Recent advance of microbial mercury methylation in the environment. Appl Microbiol Biotechnol 2024; 108:235. [PMID: 38407657 PMCID: PMC10896945 DOI: 10.1007/s00253-023-12967-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Revised: 12/02/2023] [Accepted: 12/13/2023] [Indexed: 02/27/2024]
Abstract
Methylmercury formation is mainly driven by microbial-mediated process. The mechanism of microbial mercury methylation has become a crucial research topic for understanding methylation in the environment. Pioneering studies of microbial mercury methylation are focusing on functional strain isolation, microbial community composition characterization, and mechanism elucidation in various environments. Therefore, the functional genes of microbial mercury methylation, global isolations of Hg methylation strains, and their methylation potential were systematically analyzed, and methylators in typical environments were extensively reviewed. The main drivers (key physicochemical factors and microbiota) of microbial mercury methylation were summarized and discussed. Though significant progress on the mechanism of the Hg microbial methylation has been explored in recent decade, it is still limited in several aspects, including (1) molecular biology techniques for identifying methylators; (2) characterization methods for mercury methylation potential; and (3) complex environmental properties (environmental factors, complex communities, etc.). Accordingly, strategies for studying the Hg microbial methylation mechanism were proposed. These strategies include the following: (1) the development of new molecular biology methods to characterize methylation potential; (2) treating the environment as a micro-ecosystem and studying them from a holistic perspective to clearly understand mercury methylation; (3) a more reasonable and sensitive inhibition test needs to be considered. KEY POINTS: • Global Hg microbial methylation is phylogenetically and functionally discussed. • The main drivers of microbial methylation are compared in various condition. • Future study of Hg microbial methylation is proposed.
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Affiliation(s)
- Xuya Peng
- Key Laboratory of Three Gorges Reservoir Region's Eco-Environment, Ministry of Education, Chongqing University, No. 174, Shapingba Street, Chongqing, 400045, China
| | - Yan Yang
- Key Laboratory of Three Gorges Reservoir Region's Eco-Environment, Ministry of Education, Chongqing University, No. 174, Shapingba Street, Chongqing, 400045, China
| | - Shu Yang
- Key Laboratory of Three Gorges Reservoir Region's Eco-Environment, Ministry of Education, Chongqing University, No. 174, Shapingba Street, Chongqing, 400045, China.
- Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, 230026, China.
| | - Lei Li
- Key Laboratory of Three Gorges Reservoir Region's Eco-Environment, Ministry of Education, Chongqing University, No. 174, Shapingba Street, Chongqing, 400045, China
| | - Liyan Song
- School of resources and environmental engineering, Anhui University, No 111 Jiulong Road, Economic and Technology Development Zone, Hefei, 230601, People's Republic of China.
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7
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Johnson J, Jain KR, Patel A, Parmar N, Joshi C, Madamwar D. Chronic industrial perturbation and seasonal change induces shift in the bacterial community from gammaproteobacteria to betaproteobacteria having catabolic potential for aromatic compounds at Amlakhadi canal. World J Microbiol Biotechnol 2023; 40:52. [PMID: 38146029 DOI: 10.1007/s11274-023-03848-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2023] [Accepted: 11/19/2023] [Indexed: 12/27/2023]
Abstract
Escalating proportions of industrially contaminated sites are one of the major catastrophes faced at the present time due to the industrial revolution. The difficulties associated with culturing the microbes, has been circumvent by the direct use of metagenomic analysis of various complex niches. In this study, a metagenomic approach using next generation sequencing technologies was applied to exemplify the taxonomic abundance and metabolic potential of the microbial community residing in Amlakhadi canal, Ankleshwar at two different seasons. All the metagenomes revealed a predominance of Proteobacteria phylum. However, difference was observed within class level where Gammaproteobacteria was relatively high in polluted metagenome in Summer while in Monsoon the abundance shifted to Betaproteobacteria. Similarly, significant statistical differences were obtained while comparing the genera amongst contaminated sites where Serratia, Achromobacter, Stenotrophomonas and Pseudomonas were abundant in summer season and the dominance changed to Thiobacillus, Thauera, Acidovorax, Nitrosomonas, Sulfuricurvum, Novosphingobium, Hyphomonas and Geobacter in monsoon. Further upon functional characterization, the microbiomes revealed the diverse survival mechanisms, in response to the prevailing ecological conditions (such as degradation of aromatic compounds, heavy metal resistance, oxidative stress responses and multidrug resistance efflux pumps, etc.). The results have important implications in understanding and predicting the impacts of human-induced activities on microbial communities inhabiting natural niche and their responses in coping with the fluctuating pollution load.
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Affiliation(s)
- Jenny Johnson
- Post Graduate Department of Biosciences, Centre of Advanced Study, Sardar Patel University, Satellite Campus, Vadtal Road, Bakrol (Anand), Gujarat, 388 315, India
| | - Kunal R Jain
- Post Graduate Department of Biosciences, Centre of Advanced Study, Sardar Patel University, Satellite Campus, Vadtal Road, Bakrol (Anand), Gujarat, 388 315, India
| | - Anand Patel
- Department of Animal Biotechnology, College of Veterinary Science and Animal Husbandry, Anand Agricultural University, Anand, Gujarat, 388 001, India
| | - Nidhi Parmar
- Department of Animal Biotechnology, College of Veterinary Science and Animal Husbandry, Anand Agricultural University, Anand, Gujarat, 388 001, India
| | - Chaitanya Joshi
- Gujarat Biotechnology Research Centre, 6th Floor, M. S. Building, Sector 11, Gandhinagar, Gujarat, 382011, India
| | - Datta Madamwar
- P. D. Patel Institute of Applied Sciences, Charotar University of Science and Technology, CHARUSAT Campus, Changa (Anand), Gujarat, 388 421, India.
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8
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Li Z, Wang T, Yang X, Wen X, Chen W, He Y, Yu Z, Zhang C. Microbial community function and methylmercury production in oxygen-limited paddy soil. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2023; 266:115585. [PMID: 37856980 DOI: 10.1016/j.ecoenv.2023.115585] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2023] [Revised: 10/03/2023] [Accepted: 10/11/2023] [Indexed: 10/21/2023]
Abstract
Methylmercury is a neurotoxic compound that can enter rice fields through rainfall or irrigation with contaminated wastewater, and then contaminate the human food chain through the consumption of rice. Flooded paddy soil has a porous structure that facilitates air exchange with the atmosphere, but the presence of trace amounts of oxygen in flooded rice field soil and its impact on microbial-mediated formation of methylmercury is still unclear. We compared the microbial communities and their functions in oxygen-depleted and oxygen-limited paddy soil. We discovered that oxygen-limited paddy soil had higher methylmercury concentration, which was strongly correlated with soil properties and methylation potential. Compared with oxygen-depleted soil, oxygen-limited soil altered the microbial composition based on 16 S rRNA sequences, but not based on hgcA sequences. Moreover, oxygen-limited soil enhanced microbial activity significantly, increasing the abundance of more than half of the KEGG pathways, especially the metabolic pathways that might be involved in methylation. Our study unveils how microbial communities influence methylmercury formation in oxygen-limited paddy soil. ENVIRONMENTAL IMPLICATIONS: This study examined how low oxygen input affects microbial-induced MeHg formation in anaerobic paddy soil. We found that oxygen-limited soil produced more MeHg than oxygen-depleted soil. Oxygen input altered the microbial community structure of 16 S rRNA sequencing in anaerobic paddy soil, but had little impact on the hgcA sequencing community structure. Microbial activity and metabolic functions related to MeHg formation were also higher in oxygen-limited paddy soil. We suggest that oxygen may not be a limiting factor for Hg methylators, and that insufficient oxygen input in flooded paddy soil increases the risk of human exposure to MeHg from rice consumption.
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Affiliation(s)
- Zihao Li
- College of Environmental Science and Engineering, Hunan University, Changsha 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, China
| | - Tantan Wang
- College of Environmental Science and Engineering, Hunan University, Changsha 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, China
| | - Xu Yang
- College of Environmental Science and Engineering, Hunan University, Changsha 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, China
| | - Xin Wen
- College of Environmental Science and Engineering, Hunan University, Changsha 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, China
| | - Wenhao Chen
- College of Environmental Science and Engineering, Hunan University, Changsha 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, China
| | - Yubo He
- College of Environmental Science and Engineering, Hunan University, Changsha 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, China
| | - Zhigang Yu
- Australian Center for Water and Environmental Biotechnology, The University of Queensland, St. Lucia, Brisbane, QLD 4072, Australia
| | - Chang Zhang
- College of Environmental Science and Engineering, Hunan University, Changsha 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, China.
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9
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Zhang R, Aris-Brosou S, Storck V, Liu J, Abdelhafiz MA, Feng X, Meng B, Poulain AJ. Mining-impacted rice paddies select for Archaeal methylators and reveal a putative (Archaeal) regulator of mercury methylation. ISME COMMUNICATIONS 2023; 3:74. [PMID: 37454192 PMCID: PMC10349881 DOI: 10.1038/s43705-023-00277-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2023] [Revised: 06/19/2023] [Accepted: 06/22/2023] [Indexed: 07/18/2023]
Abstract
Methylmercury (MeHg) is a microbially produced neurotoxin derived from inorganic mercury (Hg), which accumulation in rice represents a major health concern to humans. However, the microbial control of MeHg dynamics in the environment remains elusive. Here, leveraging three rice paddy fields with distinct concentrations of Hg (Total Hg (THg): 0.21-513 mg kg-1 dry wt. soil; MeHg: 1.21-6.82 ng g-1 dry wt. soil), we resorted to metagenomics to determine the microbial determinants involved in MeHg production under contrasted contamination settings. We show that Hg methylating Archaea, along with methane-cycling genes, were enriched in severely contaminated paddy soils. Metagenome-resolved Genomes of novel putative Hg methylators belonging to Nitrospinota (UBA7883), with poorly resolved taxonomy despite high completeness, showed evidence of facultative anaerobic metabolism and adaptations to fluctuating redox potential. Furthermore, we found evidence of environmental filtering effects that influenced the phylogenies of not only hgcA genes under different THg concentrations, but also of two housekeeping genes, rpoB and glnA, highlighting the need for further experimental validation of whether THg drives the evolution of hgcAB. Finally, assessment of the genomic environment surrounding hgcAB suggests that this gene pair may be regulated by an archaeal toxin-antitoxin (TA) system, instead of the more frequently found arsR-like genes in bacterial methylators. This suggests the presence of distinct hgcAB regulation systems in bacteria and archaea. Our results support the emerging role of Archaea in MeHg cycling under mining-impacted environments and shed light on the differential control of the expression of genes involved in MeHg formation between Archaea and Bacteria.
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Affiliation(s)
- Rui Zhang
- Department of Biology, University of Ottawa, Ottawa, ON, K1N 6N5, Canada
| | - Stéphane Aris-Brosou
- Department of Biology, University of Ottawa, Ottawa, ON, K1N 6N5, Canada
- Department of Mathematics and Statistics, University of Ottawa, Ottawa, ON, K1N 6N5, Canada
| | - Veronika Storck
- Department of Civil Engineering, Polytechnique Montréal, Montréal, QC, H3C 3A7, Canada
| | - Jiang Liu
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550081, China
| | - Mahmoud A Abdelhafiz
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550081, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Xinbin Feng
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550081, China
| | - Bo Meng
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550081, China.
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10
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Scuvée D, Goñi-Urriza M, Gassie C, Khalfaoui-Hassani B, Guyoneaud R. Consortia cultivation of the Desulfobacterota from macrophyte periphyton: tool for increasing the cultivation of microorganisms involved in mercury methylation. Microbiol Res 2023; 273:127415. [PMID: 37247586 DOI: 10.1016/j.micres.2023.127415] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2023] [Revised: 05/02/2023] [Accepted: 05/17/2023] [Indexed: 05/31/2023]
Abstract
Invasive macrophytes are a persistent environmental problem in aquatic ecosystems. They also cause potential health issues, since periphyton colonizing their aquatic roots are hot spot of mercury methylation. Because periphytons are at the base of the trophic chain, the produced methylmercury is bioamplified through the food webs. In this work, a consortia cultivation approach was applied in order to investigate methylators in the periphyton of Ludwigia sp., an invasive macrophyte. Five growth conditions were used in order to favor the growth of different sulfate reducers, the major mercury methylators in this periphyton. A total of 33 consortia containing putative Hg methylators were obtained. Based on the amino acid sequences of HgcA (essential enzyme for Hg methylation), the obtained consortia could be subdivided into five main clusters, affiliated with Desulfovibrionaceae, Desulfobulbaceae and Syntrophobacteraceae. The main cluster, related to Desulfovibrionaceae, showed the highest sequence diversity; notwithstanding most of the sequences of this cluster showed no close representatives. Through the consortia approach, species thus far uncultivated were cultivated. The successful cultivation of these species was probably possible through the metabolites produced by other members of the consortium. The analysis of the microbial composition of the consortia uncover certain microbial interactions that may exist within this complex environment.
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Affiliation(s)
- Diva Scuvée
- Université de Pau et des Pays de l'Adour, E2S UPPA, CNRS, IPREM UMR5254, Environmental Microbiology and Chemistry, 64000 Pau, France
| | - Marisol Goñi-Urriza
- Université de Pau et des Pays de l'Adour, E2S UPPA, CNRS, IPREM UMR5254, Environmental Microbiology and Chemistry, 64000 Pau, France
| | - Claire Gassie
- Université de Pau et des Pays de l'Adour, E2S UPPA, CNRS, IPREM UMR5254, Environmental Microbiology and Chemistry, 64000 Pau, France
| | - Bahia Khalfaoui-Hassani
- Université de Pau et des Pays de l'Adour, E2S UPPA, CNRS, IPREM UMR5254, Environmental Microbiology and Chemistry, 64000 Pau, France
| | - Rémy Guyoneaud
- Université de Pau et des Pays de l'Adour, E2S UPPA, CNRS, IPREM UMR5254, Environmental Microbiology and Chemistry, 64000 Pau, France.
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11
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Gutensohn M, Schaefer JK, Yunda E, Skyllberg U, Björn E. The Combined Effect of Hg(II) Speciation, Thiol Metabolism, and Cell Physiology on Methylmercury Formation by Geobacter sulfurreducens. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2023; 57:7185-7195. [PMID: 37098211 PMCID: PMC10173453 DOI: 10.1021/acs.est.3c00226] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
The chemical and biological factors controlling microbial formation of methylmercury (MeHg) are widely studied separately, but the combined effects of these factors are largely unknown. We examined how the chemical speciation of divalent, inorganic mercury (Hg(II)), as controlled by low-molecular-mass thiols, and cell physiology govern MeHg formation by Geobacter sulfurreducens. We compared MeHg formation with and without addition of exogenous cysteine (Cys) to experimental assays with varying nutrient and bacterial metabolite concentrations. Cysteine additions initially (0-2 h) enhanced MeHg formation by two mechanisms: (i) altering the Hg(II) partitioning from the cellular to the dissolved phase and/or (ii) shifting the chemical speciation of dissolved Hg(II) in favor of the Hg(Cys)2 complex. Nutrient additions increased MeHg formation by enhancing cell metabolism. These two effects were, however, not additive since cysteine was largely metabolized to penicillamine (PEN) over time at a rate that increased with nutrient addition. These processes shifted the speciation of dissolved Hg(II) from complexes with relatively high availability, Hg(Cys)2, to complexes with lower availability, Hg(PEN)2, for methylation. This thiol conversion by the cells thereby contributed to stalled MeHg formation after 2-6 h Hg(II) exposure. Overall, our results showed a complex influence of thiol metabolism on microbial MeHg formation and suggest that the conversion of cysteine to penicillamine may partly suppress MeHg formation in cysteine-rich environments like natural biofilms.
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Affiliation(s)
| | - Jeffra K Schaefer
- Department of Environmental Sciences, Rutgers University, 14 College Farm Road, New Brunswick, New Jersey 08901, United States
| | - Elena Yunda
- Department of Chemistry, Umeå University, SE- 90187 Umeå, Sweden
| | - Ulf Skyllberg
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, SE-901 83 Umeå, Sweden
| | - Erik Björn
- Department of Chemistry, Umeå University, SE- 90187 Umeå, Sweden
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12
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Yunda E, Gutensohn M, Ramstedt M, Björn E. Methylmercury formation in biofilms of Geobacter sulfurreducens. Front Microbiol 2023; 14:1079000. [PMID: 36712188 PMCID: PMC9880215 DOI: 10.3389/fmicb.2023.1079000] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2022] [Accepted: 01/02/2023] [Indexed: 01/15/2023] Open
Abstract
Introduction Mercury (Hg) is a major environmental pollutant that accumulates in biota predominantly in the form of methylmercury (MeHg). Surface-associated microbial communities (biofilms) represent an important source of MeHg in natural aquatic systems. In this work, we report MeHg formation in biofilms of the iron-reducing bacterium Geobacter sulfurreducens. Methods Biofilms were prepared in media with varied nutrient load for 3, 5, or 7 days, and their structural properties were characterized using confocal laser scanning microscopy, cryo-scanning electron microscopy and Fourier-transform infrared spectroscopy. Results Biofilms cultivated for 3 days with vitamins in the medium had the highest surface coverage, and they also contained abundant extracellular matrix. Using 3 and 7-days-old biofilms, we demonstrate that G. sulfurreducens biofilms prepared in media with various nutrient load produce MeHg, of which a significant portion is released to the surrounding medium. The Hg methylation rate constant determined in 6-h assays in a low-nutrient assay medium with 3-days-old biofilms was 3.9 ± 2.0 ∙ 10-14 L ∙ cell-1 ∙ h-1, which is three to five times lower than the rates found in assays with planktonic cultures of G. sulfurreducens in this and previous studies. The fraction of MeHg of total Hg within the biofilms was, however, remarkably high (close to 50%), and medium/biofilm partitioning of inorganic Hg (Hg(II)) indicated low accumulation of Hg(II) in biofilms. Discussion These findings suggest a high Hg(II) methylation capacity of G. sulfurreducens biofilms and that Hg(II) transfer to the biofilm is the rate-limiting step for MeHg formation in this systems.
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13
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Barrouilhet S, Monperrus M, Tessier E, Khalfaoui-Hassani B, Guyoneaud R, Isaure MP, Goñi-Urriza M. Effect of exogenous and endogenous sulfide on the production and the export of methylmercury by sulfate-reducing bacteria. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2023; 30:3835-3846. [PMID: 35953752 DOI: 10.1007/s11356-022-22173-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2021] [Accepted: 07/19/2022] [Indexed: 06/15/2023]
Abstract
Mercury (Hg) is a global pollutant of environmental and health concern; its methylated form, methylmercury (MeHg), is a potent neurotoxin. Sulfur-containing molecules play a role in MeHg production by microorganisms. While sulfides are considered to limit Hg methylation, sulfate and cysteine were shown to favor this process. However, these two forms can be endogenously converted by microorganisms into sulfide. Here, we explore the effect of sulfide (produced by the cell or supplied exogenously) on Hg methylation. For this purpose, Pseudodesulfovibrio hydrargyri BerOc1 was cultivated in non-sulfidogenic conditions with addition of cysteine and sulfide as well as in sulfidogenic conditions. We report that Hg methylation depends on sulfide concentration in the culture and the sulfides produced by cysteine degradation or sulfate reduction could affect the Hg methylation pattern. Hg methylation was independent of hgcA expression. Interestingly, MeHg production was maximal at 0.1-0.5 mM of sulfides. Besides, a strong positive correlation between MeHg in the extracellular medium and the increase of sulfide concentrations was observed, suggesting a facilitated MeHg export with sulfide and/or higher desorption from the cell. We suggest that sulfides (exogenous or endogenous) play a key role in controlling mercury methylation and should be considered when investigating the impact of Hg in natural environments.
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Affiliation(s)
- Sophie Barrouilhet
- Universite de Pau Et Des Pays de L'Adour, E2S UPPA, CNRS, IPREM UMR 5254, Pau, France
| | - Mathilde Monperrus
- Universite de Pau Et Des Pays de L'Adour, E2S UPPA, CNRS, IPREM UMR 5254, Anglet, France
| | - Emmanuel Tessier
- Universite de Pau Et Des Pays de L'Adour, E2S UPPA, CNRS, IPREM UMR 5254, Pau, France
| | | | - Rémy Guyoneaud
- Universite de Pau Et Des Pays de L'Adour, E2S UPPA, CNRS, IPREM UMR 5254, Pau, France
| | - Marie-Pierre Isaure
- Universite de Pau Et Des Pays de L'Adour, E2S UPPA, CNRS, IPREM UMR 5254, Pau, France
| | - Marisol Goñi-Urriza
- Universite de Pau Et Des Pays de L'Adour, E2S UPPA, CNRS, IPREM UMR 5254, Pau, France.
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14
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Schwartz GE, Muller KA, Rathore SS, Wilpiszeski RL, Carrell AA, Cregger MA, Elias DA, Podar M, Painter SL, Brooks SC. Incorporating concentration-dependent sediment microbial activity into methylmercury production kinetics modeling. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2022; 24:1392-1405. [PMID: 34727150 DOI: 10.1039/d1em00287b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
In anoxic environments, anaerobic microorganisms carrying the hgcAB gene cluster can mediate the transformation of inorganic mercury (Hg(II)) to monomethylmercury (MMHg). The kinetics of Hg(II) transformation to MMHg in periphyton from East Fork Poplar Creek (EFPC) in Oak Ridge, TN have previously been modeled using a transient availability model (TAM). The TAM for Hg(II) methylation combines methylation/demethylation kinetics with kinetic expressions for processes that decrease Hg(II) and MMHg availability for methylation and demethylation (multisite sorption of Hg(II) and MMHg, Hg(II) reduction/Hg(0) oxidation). In this study, the TAM is used for the first time to describe MMHg production in sediment. We assessed MMHg production in sediment microcosms using two different sediment types from EFPC: a relatively anoxic, carbon-rich sediment with higher microbial activity (higher CO2 production from sediment) and a relatively oxic, sandy, carbon-poor sediment with lower microbial activity (lower CO2 production from sediment). Based on 16s rRNA sequencing, the overall microbial community structure in the two sediments was retained during the incubations. However, the hgcA containing methanogenic Euryarchaeota communities differed between sediment types and their growth followed different trajectories over the course of incubations, potentially contributing to the distinct patterns of MMHg production observed. The general TAM paradigm performed well in describing MMHg production in the sediments. However, the MMHg production and ancillary data suggested the need to revise the model structure to incorporate terms for concentration-dependent microbial activity over the course of the incubations. We modified the TAM to include Monod-type kinetics for methylation and demethylation and observed an improved fit for the carbon-rich, microbially active sediment. Overall our work shows that the TAM can be applied to describe Hg(II) methylation in sediments and that including expressions accounting for concentration-dependent microbial activity can improve the accuracy of the model description of the data in some cases.
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Affiliation(s)
- Grace E Schwartz
- Environmental Sciences Division, Oak Ridge National Laboratory, P. O. Box 2008, MS 6038, Oak Ridge, Tennessee 37831-6038, USA.
| | - Katherine A Muller
- Earth Systems Science Division, Pacific Northwest National Laboratory, Richland, WA, USA
| | - Saubhagya S Rathore
- Environmental Sciences Division, Oak Ridge National Laboratory, P. O. Box 2008, MS 6038, Oak Ridge, Tennessee 37831-6038, USA.
| | - Regina L Wilpiszeski
- Biosciences Division, Oak Ridge National Laboratory, P. O. Box 2008, MS 6038, Oak Ridge, Tennessee 37831-6038, USA
| | - Alyssa A Carrell
- Biosciences Division, Oak Ridge National Laboratory, P. O. Box 2008, MS 6038, Oak Ridge, Tennessee 37831-6038, USA
| | - Melissa A Cregger
- Biosciences Division, Oak Ridge National Laboratory, P. O. Box 2008, MS 6038, Oak Ridge, Tennessee 37831-6038, USA
| | - Dwayne A Elias
- Biosciences Division, Oak Ridge National Laboratory, P. O. Box 2008, MS 6038, Oak Ridge, Tennessee 37831-6038, USA
| | - Mircea Podar
- Biosciences Division, Oak Ridge National Laboratory, P. O. Box 2008, MS 6038, Oak Ridge, Tennessee 37831-6038, USA
| | - Scott L Painter
- Environmental Sciences Division, Oak Ridge National Laboratory, P. O. Box 2008, MS 6038, Oak Ridge, Tennessee 37831-6038, USA.
| | - Scott C Brooks
- Environmental Sciences Division, Oak Ridge National Laboratory, P. O. Box 2008, MS 6038, Oak Ridge, Tennessee 37831-6038, USA.
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15
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Monte CN, Rodrigues APC, Galvão PMA, Pontes GC, Malm O, Wasserman JC, Machado W. Mercury methylation upon coastal sediment resuspension: a worst-case approach under dark conditions. ENVIRONMENTAL MONITORING AND ASSESSMENT 2022; 194:805. [PMID: 36123414 DOI: 10.1007/s10661-022-10485-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2022] [Accepted: 09/10/2022] [Indexed: 06/15/2023]
Abstract
Mercury behavior upon resuspension of sediments from two impacted areas of Guanabara Bay was evaluated to assess worst-case methylmercury (MeHg) responses, under dark experimental conditions to prevent demethylation by photolysis. Study areas include the Rio de Janeiro Harbor (RJH) and the chlor-alkali plant-affected Meriti River (MR) estuary. Total mercury (THg) and MeHg concentrations were determined along 24-h experiments of sediment resuspension in the bay water in dark conditions. Fine-grained Meriti River (MR) estuary sediments had 8 times higher MeHg initial concentrations than sandy Rio de Janeiro Harbor (RJH) sediments (3.4 ± 0.29 vs. 0.41 ± 0.1 ng g-1, respectively). Though THg contents were uncorrelated with resuspension time, statistically significant correlations of MeHg (rs = 0.78) and %MeHg in relation to THg (rs = 0.86) with resuspension time were observed for RJH sediments, indicating net methylation only for this study site. These positive correlation trends correspond to a 2.8 times MeHg concentration increase (ΔMeHg = 0.75 ng g-1) and 4.4 times increase in %MeHg (Δ%MeHg = 1.0%), after 24 h of resuspension. This suggests that assessments of factors affecting the MeHg spatial-temporal variability and associated toxicity risks can be limited in some sites if concentration changes due to sediment resuspension-redeposition processes are not considered. Therefore, the inclusion of MeHg evaluation before and after sediment resuspension events is recommendable for the improvement of dredging licensing and monitoring activities.
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Affiliation(s)
- Christiane N Monte
- Geochemistry Program, Universidade Federal Fluminense, Niterói, RJ, Brazil.
- Geology Department, Universidade Federal Do Oeste Do Pará, Santarém, PA, Brazil.
| | - Ana Paula C Rodrigues
- Geochemistry Program, Universidade Federal Fluminense, Niterói, RJ, Brazil
- Marine Biology Department, Universidade Federal Do Rio de Janeiro, Ilha Do Fundão, RJ, Brazil
| | - Petrus M A Galvão
- Biophysics Institute, Universidade Federal Do Rio de Janeiro, Ilha Do Fundão, RJ, Brazil
| | - Gabriela C Pontes
- Geochemistry Program, Universidade Federal Fluminense, Niterói, RJ, Brazil
| | - Olaf Malm
- Biophysics Institute, Universidade Federal Do Rio de Janeiro, Ilha Do Fundão, RJ, Brazil
| | - Júlio C Wasserman
- Geochemistry Program, Universidade Federal Fluminense, Niterói, RJ, Brazil
- Geosciences Institute, Universidade Federal Fluminense, Niterói, RJ, Brazil
| | - Wilson Machado
- Geochemistry Program, Universidade Federal Fluminense, Niterói, RJ, Brazil
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16
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Capo E, Feng C, Bravo AG, Bertilsson S, Soerensen AL, Pinhassi J, Buck M, Karlsson C, Hawkes J, Björn E. Expression Levels of hgcAB Genes and Mercury Availability Jointly Explain Methylmercury Formation in Stratified Brackish Waters. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:13119-13130. [PMID: 36069707 PMCID: PMC9494745 DOI: 10.1021/acs.est.2c03784] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Neurotoxic methylmercury (MeHg) is formed by microbial methylation of inorganic divalent Hg (HgII) and constitutes severe environmental and human health risks. The methylation is enabled by hgcA and hgcB genes, but it is not known if the associated molecular-level processes are rate-limiting or enable accurate prediction of MeHg formation in nature. In this study, we investigated the relationships between hgc genes and MeHg across redox-stratified water columns in the brackish Baltic Sea. We showed, for the first time, that hgc transcript abundance and the concentration of dissolved HgII-sulfide species were strong predictors of both the HgII methylation rate and MeHg concentration, implying their roles as principal joint drivers of MeHg formation in these systems. Additionally, we characterized the metabolic capacities of hgc+ microorganisms by reconstructing their genomes from metagenomes (i.e., hgc+ MAGs), which highlighted the versatility of putative HgII methylators in the water column of the Baltic Sea. In establishing relationships between hgc transcripts and the HgII methylation rate, we advance the fundamental understanding of mechanistic principles governing MeHg formation in nature and enable refined predictions of MeHg levels in coastal seas in response to the accelerating spread of oxygen-deficient zones.
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Affiliation(s)
- Eric Capo
- Department
of Chemistry, Umeå University, Umeå 901 87, Sweden
- Department
of Aquatic Sciences and Assessment, Swedish
University of Agricultural Sciences, Uppsala 750 07, Sweden
| | - Caiyan Feng
- Department
of Chemistry, Umeå University, Umeå 901 87, Sweden
| | - Andrea G. Bravo
- Department
of Marine Biology and Oceanography, Institute of Marine Sciences, Spanish National Research Council (CSIC), Barcelona 08003, Spain
| | - Stefan Bertilsson
- Department
of Aquatic Sciences and Assessment, Swedish
University of Agricultural Sciences, Uppsala 750 07, Sweden
| | - Anne L. Soerensen
- Department
of Environmental Research and Monitoring, Swedish Museum of Natural History, Stockholm 104 05, Sweden
| | - Jarone Pinhassi
- Centre
for Ecology and Evolution in Microbial Model Systems—EEMiS, Linnaeus University, Kalmar 391 82, Sweden
| | - Moritz Buck
- Department
of Aquatic Sciences and Assessment, Swedish
University of Agricultural Sciences, Uppsala 750 07, Sweden
| | - Camilla Karlsson
- Centre
for Ecology and Evolution in Microbial Model Systems—EEMiS, Linnaeus University, Kalmar 391 82, Sweden
| | - Jeffrey Hawkes
- Department
of Chemistry, Uppsala University, Uppsala 751 23, Sweden
| | - Erik Björn
- Department
of Chemistry, Umeå University, Umeå 901 87, Sweden
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17
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Rodríguez J, Andersson A, Björn E, Timonen S, Brugel S, Skrobonja A, Rowe O. Inputs of Terrestrial Dissolved Organic Matter Enhance Bacterial Production and Methylmercury Formation in Oxic Coastal Water. Front Microbiol 2022; 13:809166. [PMID: 35966696 PMCID: PMC9363918 DOI: 10.3389/fmicb.2022.809166] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2021] [Accepted: 06/22/2022] [Indexed: 11/16/2022] Open
Abstract
Methylmercury (MeHg) is a potent neurotoxin commonly found in aquatic environments and primarily formed by microbial methylation of inorganic divalent mercury (Hg(II)) under anoxic conditions. Recent evidence, however, points to the production of MeHg also in oxic pelagic waters, but the magnitude and the drivers for this process remain unclear. Here, we performed a controlled experiment testing the hypothesis that inputs of terrestrial dissolved organic matter (tDOM) to coastal waters enhance MeHg formation via increased bacterial activity. Natural brackish seawater from a coastal area of the Baltic Sea was exposed to environmentally relevant levels of Hg(II) and additions of tDOM according to climate change scenarios. MeHg formation was observed to be coupled to elevated bacterial production rates, which, in turn, was linked to input levels of tDOM. The increased MeHg formation was, however, not coupled to any specific change in bacterial taxonomic composition nor to an increased abundance of known Hg(II) methylation genes. Instead, we found that the abundance of genes for the overall bacterial carbon metabolism was higher under increased tDOM additions. The findings of this study may have important ecological implications in a changing global climate by pointing to the risk of increased exposure of MeHg to pelagic biota.
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Affiliation(s)
- Juanjo Rodríguez
- Department of Ecology and Environmental Sciences, Umeå University, Umeå, Sweden
- Department of Microbiology, University of Helsinki, Helsinki, Finland
- *Correspondence: Juanjo Rodríguez,
| | - Agneta Andersson
- Department of Ecology and Environmental Sciences, Umeå University, Umeå, Sweden
- Umeå Marine Research Centre (UMF), Umeå University, Hörnefors, Sweden
| | - Erik Björn
- Department of Chemistry, Umeå University, Umeå, Sweden
| | - Sari Timonen
- Department of Microbiology, University of Helsinki, Helsinki, Finland
| | - Sonia Brugel
- Department of Ecology and Environmental Sciences, Umeå University, Umeå, Sweden
- Umeå Marine Research Centre (UMF), Umeå University, Hörnefors, Sweden
| | | | - Owen Rowe
- Helsinki Commission (HELCOM), Baltic Marine Environment Protection Commission, Helsinki, Finland
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18
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An Y, Zhang R, Yang S, Wang Y, Lei Y, Peng S, Song L. Microbial mercury methylation potential in a large-scale municipal solid waste landfill, China. WASTE MANAGEMENT (NEW YORK, N.Y.) 2022; 145:102-111. [PMID: 35526502 DOI: 10.1016/j.wasman.2022.04.038] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Revised: 04/23/2022] [Accepted: 04/27/2022] [Indexed: 06/14/2023]
Abstract
Landfills harbor ideal conditions for microbial mercury methylation. However, the levels and distribution of mercury (Hg) and methylmercury (MeHg), potential microbial Hg methylation, and their linkage within landfills are largely unknown. In the present study, total mercury (THg), MeHg, the Hg methylation gene (hgcA) and mer operon were quantified in 30 waste samples from different depths (0-30 m) at 5 locations within a large-scale landfill in China. The average concentrations of THg and MeHg in the solid waste samples were 1422.91 ng/g and 3.15 ng/g, respectively. THg (up to 14405.29 ng/g) and MeHg (up to 10.42 ng/g) have high concentrations in the middle part (10-15 m) along the depth profiles. The concentration of THg was strongly positively (both p < 0.05) correlated with the MeHg concentration and the relative abundance of hgcA, indicating that the THg concentration can play an important role in microbial Hg methylation. The hgcA genes were detected in most samples and mer operon were detected in all samples. Combined hgcA qPCR and metagenomics data showed that Archaea Methanofollis may mainly account for Hg methylation within landfills. These findings provide fundamental knowledge on Hg cycles in landfills.
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Affiliation(s)
- Yuwei An
- Chongqing Jiaotong University, Chongqing 400074, China; Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, China; Chongqing School, University of Chinese Academy of Sciences, Chongqing 400714, China
| | - Rui Zhang
- Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, China
| | - Shu Yang
- Key Laboratory of Three Gorges Reservoir Region's Eco-Environment, Ministry of Education, Chongqing University, Chongqing 400045, China.
| | - Yangqing Wang
- Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, China
| | - Yu Lei
- Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, China
| | - Shaohong Peng
- Guangdong Provincial Key Laboratory of Petrochemical Pollution Process and Control, Guangdong University of Petrochemical Technology, Maoming 525000, China
| | - Liyan Song
- Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, China; School of Resources and Environmental Engineering, Anhui University, Hefei 230601, China.
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19
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Transcriptomic evidence for versatile metabolic activities of mercury cycling microorganisms in brackish microbial mats. NPJ Biofilms Microbiomes 2021; 7:83. [PMID: 34799579 PMCID: PMC8605020 DOI: 10.1038/s41522-021-00255-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2021] [Accepted: 10/22/2021] [Indexed: 01/29/2023] Open
Abstract
Methylmercury, biomagnifying through food chains, is highly toxic for aquatic life. Its production and degradation are largely driven by microbial transformations; however, diversity and metabolic activity of mercury transformers, resulting in methylmercury concentrations in environments, remain poorly understood. Microbial mats are thick biofilms where oxic and anoxic metabolisms cooccur, providing opportunities to investigate the complexity of the microbial mercury transformations over contrasted redox conditions. Here, we conducted a genome-resolved metagenomic and metatranscriptomic analysis to identify putative activity of mercury reducers, methylators and demethylators in microbial mats strongly contaminated by mercury. Our transcriptomic results revealed the major role of rare microorganisms in mercury cycling. Mercury methylators, mainly related to Desulfobacterota, expressed a large panel of metabolic activities in sulfur, iron, nitrogen, and halogen compound transformations, extending known activities of mercury methylators under suboxic to anoxic conditions. Methylmercury detoxification processes were dissociated in the microbial mats with methylmercury cleavage being carried out by sulfide-oxidizing Thiotrichaceae and Rhodobacteraceae populations, whereas mercury reducers included members of the Verrucomicrobia, Bacteroidetes, Gammaproteobacteria, and different populations of Rhodobacteraceae. However most of the mercury reduction was potentially carried out anaerobically by sulfur- and iron-reducing Desulfuromonadaceae, revising our understanding of mercury transformers ecophysiology.
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20
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Hyun HR, Yoon H, Lyou ES, Kim JJ, Kwon SY, Lee TK. Short-Term Legacy Effects of Mercury Contamination on Plant Growth and nifH-Harboring Microbial Community in Rice Paddy Soil. MICROBIAL ECOLOGY 2021; 82:932-941. [PMID: 33624137 DOI: 10.1007/s00248-021-01722-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Accepted: 02/15/2021] [Indexed: 06/12/2023]
Abstract
Methylmercury (MeHg), which is formed in rice paddy soil, exhibits strong neurotoxicity through bioaccumulation in the food chain. A few groups of microorganisms drive both mercury methylation and nitrogen fixation in the rhizosphere. Little is known about how the shifted soil microbial community by Hg contamination affects nitrogen fixation rate and plant growth in paddy soil. Here, we examined how stimulated short-term Hg amendment affects the nitrogen fixing microbial community and influences plant-microbe interactions. Soil was treated with low (0.2 mg/kg) and high (1.1 mg/kg) concentrations of Hg for 4 weeks; then, rice (Oryza sativa) was planted and grown for 12 weeks. The nitrogen-fixation rate and rice growth were measured. The diversity and structure of the microbial community were analyzed by sequencing the nifH gene before and after rice cultivation. Hg treatments significantly decreased the nitrogen fixation rate and dry weight of the rice plants. The structure of the nifH-harboring community was remarkably changed after rice cultivation depending on Hg treatments. Iron- or sulfate-reducing bacteria, including Desulfobacca, Desulfoporosimus, and Geobacter, were observed as legacy response groups; their abundances increased in the soil after Hg treatment. The high abundance of those groups were maintained in control, but the abundance drastically decreased after rice cultivation in the soil treated with Hg, indicating that symbiotic behavior of rice plants changes according to the legacy effects on Hg contamination. These results suggested that Hg contamination can persist in soil microbial communities, affecting their nitrogen-fixation ability and symbiosis with rice plants in paddy soil.
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Affiliation(s)
- Hye Rim Hyun
- Department of Environmental Engineering, Yonsei University, Wonju, Republic of Korea
| | - Hakwon Yoon
- Division of Environmental Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Republic of Korea
| | - Eun Sun Lyou
- Department of Environmental Engineering, Yonsei University, Wonju, Republic of Korea
| | - Jin Ju Kim
- Department of Systems Biotechnology, Chun-Ang University, Anseong, Republic of Korea
| | - Sae Yun Kwon
- Division of Environmental Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Republic of Korea
| | - Tae Kwon Lee
- Department of Environmental Engineering, Yonsei University, Wonju, Republic of Korea.
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21
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Millera Ferriz L, Ponton DE, Storck V, Leclerc M, Bilodeau F, Walsh DA, Amyot M. Role of organic matter and microbial communities in mercury retention and methylation in sediments near run-of-river hydroelectric dams. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 774:145686. [PMID: 33609815 DOI: 10.1016/j.scitotenv.2021.145686] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2020] [Revised: 01/08/2021] [Accepted: 02/03/2021] [Indexed: 06/12/2023]
Abstract
Run-of-river power plants (RoRs) are expected to triple in number over the next decades in Canada. These structures are not anticipated to considerably promote the mobilization and transport of mercury (Hg) and its subsequent microbial transformation to methylmercury (MeHg), a neurotoxin able to biomagnify in food webs up to humans. To test whether construction of RoRs had an effect on Hg transport and transformation, we studied Hg and MeHg concentrations, organic matter contents and methylating microbial community abundance and composition in the sediments of a section of the St. Maurice River (Quebec, Canada). This river section has been affected by the construction of two RoR dams and its watershed has been disturbed by a forest fire, logging, and the construction of wetlands. Higher total Hg (THg) and MeHg concentrations were observed in the surface sediments of the flooded sites upstream of the RoRs. These peaks in THg and MeHg were correlated with organic matter proportions in the sediments (r2 = 0.87 and 0.82, respectively). In contrast, the proportion of MeHg, a proxy for methylation potential, was best explained by the carbon to nitrogen ratio suggesting the importance of terrigenous organic matter as labile substrate for Hg methylation in this system. Metagenomic analysis of Hg-methylating communities based on the hgcA functional gene marker indicated an abundance of methanogens, sulfate reducers and fermenters, suggesting that these metabolic guilds may be primary Hg methylators in these surface sediments. We propose that RoR pondages act as traps for sediments, organic matter and Hg, and that this retention can be amplified by other disturbances of the watershed such as forest fire and logging. RoR flooded sites can be conducive to Hg methylation in sediments and may act as gateways for bioaccumulation and biomagnification of MeHg along food webs, particularly in disturbed watersheds.
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Affiliation(s)
- L Millera Ferriz
- Département de sciences biologiques, Université de Montréal, Montreal H2V 2S9, QC, Canada; Biology Department, Concordia University, Montreal H4B 1R6, QC, Canada; GRIL, Groupe de Recherche Interuniversitaire en Limnologie, Département de sciences biologiques, Université de Montréal, Campus MIL, Montreal H3C 3J7, QC, Canada
| | - D E Ponton
- Département de sciences biologiques, Université de Montréal, Montreal H2V 2S9, QC, Canada; GRIL, Groupe de Recherche Interuniversitaire en Limnologie, Département de sciences biologiques, Université de Montréal, Campus MIL, Montreal H3C 3J7, QC, Canada
| | - V Storck
- Département de sciences biologiques, Université de Montréal, Montreal H2V 2S9, QC, Canada; Biology Department, Concordia University, Montreal H4B 1R6, QC, Canada
| | - M Leclerc
- Département de sciences biologiques, Université de Montréal, Montreal H2V 2S9, QC, Canada; GRIL, Groupe de Recherche Interuniversitaire en Limnologie, Département de sciences biologiques, Université de Montréal, Campus MIL, Montreal H3C 3J7, QC, Canada
| | - F Bilodeau
- Hydro-Québec Production, Environment Department, Montreal, QC, Canada
| | - D A Walsh
- Biology Department, Concordia University, Montreal H4B 1R6, QC, Canada; GRIL, Groupe de Recherche Interuniversitaire en Limnologie, Département de sciences biologiques, Université de Montréal, Campus MIL, Montreal H3C 3J7, QC, Canada
| | - M Amyot
- Département de sciences biologiques, Université de Montréal, Montreal H2V 2S9, QC, Canada; GRIL, Groupe de Recherche Interuniversitaire en Limnologie, Département de sciences biologiques, Université de Montréal, Campus MIL, Montreal H3C 3J7, QC, Canada.
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22
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Lin H, Ascher DB, Myung Y, Lamborg CH, Hallam SJ, Gionfriddo CM, Holt KE, Moreau JW. Mercury methylation by metabolically versatile and cosmopolitan marine bacteria. THE ISME JOURNAL 2021; 15:1810-1825. [PMID: 33504941 PMCID: PMC8163782 DOI: 10.1038/s41396-020-00889-4] [Citation(s) in RCA: 61] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Accepted: 12/17/2020] [Indexed: 01/30/2023]
Abstract
Microbes transform aqueous mercury (Hg) into methylmercury (MeHg), a potent neurotoxin that accumulates in terrestrial and marine food webs, with potential impacts on human health. This process requires the gene pair hgcAB, which encodes for proteins that actuate Hg methylation, and has been well described for anoxic environments. However, recent studies report potential MeHg formation in suboxic seawater, although the microorganisms involved remain poorly understood. In this study, we conducted large-scale multi-omic analyses to search for putative microbial Hg methylators along defined redox gradients in Saanich Inlet, British Columbia, a model natural ecosystem with previously measured Hg and MeHg concentration profiles. Analysis of gene expression profiles along the redoxcline identified several putative Hg methylating microbial groups, including Calditrichaeota, SAR324 and Marinimicrobia, with the last the most active based on hgc transcription levels. Marinimicrobia hgc genes were identified from multiple publicly available marine metagenomes, consistent with a potential key role in marine Hg methylation. Computational homology modelling predicts that Marinimicrobia HgcAB proteins contain the highly conserved amino acid sites and folding structures required for functional Hg methylation. Furthermore, a number of terminal oxidases from aerobic respiratory chains were associated with several putative novel Hg methylators. Our findings thus reveal potential novel marine Hg-methylating microorganisms with a greater oxygen tolerance and broader habitat range than previously recognized.
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Affiliation(s)
- Heyu Lin
- grid.1008.90000 0001 2179 088XSchool of Earth Sciences, The University of Melbourne, Parkville, VIC 3010 Australia
| | - David B. Ascher
- grid.1008.90000 0001 2179 088XStructural Biology and Bioinformatics, Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, VIC 3010 Australia ,grid.1051.50000 0000 9760 5620Computational Biology and Clinical Informatics, Baker Heart and Diabetes Institute, PO Box 6492, Melbourne, VIC 3004 Australia
| | - Yoochan Myung
- grid.1008.90000 0001 2179 088XStructural Biology and Bioinformatics, Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, VIC 3010 Australia ,grid.1051.50000 0000 9760 5620Computational Biology and Clinical Informatics, Baker Heart and Diabetes Institute, PO Box 6492, Melbourne, VIC 3004 Australia
| | - Carl H. Lamborg
- grid.205975.c0000 0001 0740 6917Department of Ocean Sciences, University of California, Santa Cruz, CA 95064 USA
| | - Steven J. Hallam
- grid.17091.3e0000 0001 2288 9830Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC V6T 1Z1 Canada ,grid.17091.3e0000 0001 2288 9830Genome Science and Technology Program, University of British Columbia, Vancouver, BC V6T 1Z4 Canada
| | - Caitlin M. Gionfriddo
- grid.135519.a0000 0004 0446 2659Biosciences Division, Oak Ridge National Laboratory, PO Box 2008, Oak Ridge, TN 37831 USA ,grid.419533.90000 0000 8612 0361Present Address: Smithsonian Environmental Research Center, Edgewater, MD 21037 USA
| | - Kathryn E. Holt
- grid.1002.30000 0004 1936 7857Department of Infectious Diseases, Central Clinical School, Monash University, Monash, VIC 3800 Australia ,grid.8991.90000 0004 0425 469XDepartment of Infection Biology, London School of Hygiene & Tropical Medicine, London, WC1E 7HT UK
| | - John W. Moreau
- grid.1008.90000 0001 2179 088XSchool of Earth Sciences, The University of Melbourne, Parkville, VIC 3010 Australia ,grid.8756.c0000 0001 2193 314XPresent Address: Currently at School of Geographical & Earth Sciences, University of Glasgow, Glasgow, G12 8QQ UK
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23
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Cao D, Chen W, Xiang Y, Mi Q, Liu H, Feng P, Shen H, Zhang C, Wang Y, Wang D. The efficiencies of inorganic mercury bio-methylation by aerobic bacteria under different oxygen concentrations. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2021; 207:111538. [PMID: 33254400 DOI: 10.1016/j.ecoenv.2020.111538] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2020] [Revised: 10/15/2020] [Accepted: 10/18/2020] [Indexed: 06/12/2023]
Abstract
Limited information is available about the bio-methylation of inorganic mercury (iHg) under aerobic conditions. In this study, two γ-proteobacteria strains (P. fluorescens TGR-B2 and P. putida TGR-B4) were obtained from the soil of The Three Gorges Reservoir (TGR), demonstrating effective aerobic transformation capacities of iHg into methylmercury (MeHg). Based on periodical changes in soil oxygen content of the TGR, a culture system was established, in which 300 ng Hg (II) L-1 and O2 were set at 7%, 14%, and 21%, respectively. Results indicated that the two strains differed significantly in bacterial growth rate and MeHg production. The kinetic model of MeHg showed typical characteristics of a "two-staged" process: The first stage was dominated by bio-methylation, which was shown by increasing of net MeHg content. Moreover, the second stage was dominated by bio-demethylation, which decreased net MeHg content. Thus, we hypothesized that the mechanism of aerobic bacterial iHg bio-methylation: (1) should inefficiency compared to anaerobic bacteria i.e.SRB, which were regulated by hgcA/B gene clusters, (2) might be regarded as a passive stress response and depended on the bacterial iHg intoxication threshold and MeHg tolerance threshold.
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Affiliation(s)
- Dan Cao
- College of Resources and Environment, Southwest University, Chongqing 400715, China
| | - Weihong Chen
- College of Resources and Environment, Southwest University, Chongqing 400715, China
| | - Yuping Xiang
- College of Resources and Environment, Southwest University, Chongqing 400715, China
| | - Qianfen Mi
- Biological Science Research Center of Southwest University, Chongqing 400715, China
| | - Hang Liu
- College of Resources and Environment, Southwest University, Chongqing 400715, China
| | - PengYu Feng
- College of Resources and Environment, Southwest University, Chongqing 400715, China
| | - Hong Shen
- College of Resources and Environment, Southwest University, Chongqing 400715, China; Biological Science Research Center of Southwest University, Chongqing 400715, China; Chongqing Engineering Research Center for Agricultural Non-point Source Pollution Control in the Three Gorges Reservoir Area, Chongqing 400715, China.
| | - Cheng Zhang
- College of Resources and Environment, Southwest University, Chongqing 400715, China; Biological Science Research Center of Southwest University, Chongqing 400715, China; Chongqing Key Laboratory of Agricultural Resources and Environment, Chongqing 400715, China
| | - Yongmin Wang
- College of Resources and Environment, Southwest University, Chongqing 400715, China; Biological Science Research Center of Southwest University, Chongqing 400715, China; Chongqing Key Laboratory of Agricultural Resources and Environment, Chongqing 400715, China
| | - Dingyong Wang
- College of Resources and Environment, Southwest University, Chongqing 400715, China; Biological Science Research Center of Southwest University, Chongqing 400715, China; Chongqing Key Laboratory of Agricultural Resources and Environment, Chongqing 400715, China.
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24
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Isaure MP, Albertelli M, Kieffer I, Tucoulou R, Petrel M, Gontier E, Tessier E, Monperrus M, Goñi-Urriza M. Relationship Between Hg Speciation and Hg Methylation/Demethylation Processes in the Sulfate-Reducing Bacterium Pseudodesulfovibrio hydrargyri: Evidences From HERFD-XANES and Nano-XRF. Front Microbiol 2020; 11:584715. [PMID: 33154741 PMCID: PMC7591507 DOI: 10.3389/fmicb.2020.584715] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2020] [Accepted: 09/17/2020] [Indexed: 01/09/2023] Open
Abstract
Microorganisms are key players in the transformation of mercury into neurotoxic methylmercury (MeHg). Nevertheless, this mechanism and the opposite MeHg demethylation remain poorly understood. Here, we explored the impact of inorganic mercury (IHg) and MeHg concentrations from 0.05 to 50 μM on the production and degradation of MeHg in two sulfate-reducing bacteria, Pseudodesulfovibrio hydrargyri BerOc1 able to methylate and demethylate mercury and Desulfovibrio desulfuricans G200 only able to demethylate MeHg. MeHg produced by BerOc1 increased with increasing IHg concentration with a maximum attained for 5 μM, and suggested a saturation of the process. MeHg was mainly found in the supernatant suggesting its export from the cell. Hg L3-edge High- Energy-Resolution-Fluorescence-Detected-X-ray-Absorption-Near-Edge-Structure spectroscopy (HERFD-XANES) identified MeHg produced by BerOc1 as MeHg-cysteine2 form. A dominant tetracoordinated βHgS form was detected for BerOc1 exposed to the lowest IHg concentrations where methylation was detected. In contrast, at the highest exposure (50 μM) where Hg methylation was abolished, Hg species drastically changed suggesting a role of Hg speciation in the production of MeHg. The tetracoordinated βHgS was likely present as nano-particles as suggested by transmission electron microscopy combined to X-ray energy dispersive spectroscopy (TEM-X-EDS) and nano-X ray fluorescence (nano-XRF). When exposed to MeHg, the production of IHg, on the contrary, increased with the increase of MeHg exposure until 50 μM for both BerOc1 and G200 strains, suggesting that demethylation did not require intact biological activity. The formed IHg species were identified as various tetracoordinated Hg-S forms. These results highlight the important role of thiol ligands and Hg coordination in Hg methylation and demethylation processes.
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Affiliation(s)
- Marie-Pierre Isaure
- Université de Pau et des Pays de l'Adour, E2S UPPA, CNRS, MIRA, IPREM, Pau, France
| | - Marine Albertelli
- Université de Pau et des Pays de l'Adour, E2S UPPA, CNRS, MIRA, IPREM, Pau, France
| | - Isabelle Kieffer
- FAME-UHD, BM16 Beamline, European Synchrotron Radiation Facility (ESRF), BP220, Grenoble, France.,CNRS, IRD, Irstea, Météo France, OSUG, FAME, Université Grenoble Alpes, Grenoble, France
| | - Rémi Tucoulou
- ID16B Beamline, European Synchrotron Radiation Facility (ESRF), BP220, Grenoble, France
| | - Melina Petrel
- Bordeaux Imaging Center UMS 3420 CNRS - US4 INSERM, Université de Bordeaux, Pôle d'imagerie Électronique, Bordeaux, France
| | - Etienne Gontier
- Bordeaux Imaging Center UMS 3420 CNRS - US4 INSERM, Université de Bordeaux, Pôle d'imagerie Électronique, Bordeaux, France
| | - Emmanuel Tessier
- Université de Pau et des Pays de l'Adour, E2S UPPA, CNRS, MIRA, IPREM, Pau, France
| | - Mathilde Monperrus
- Université de Pau et des Pays de l'Adour, E2S UPPA, CNRS, MIRA, IPREM, Anglet, France
| | - Marisol Goñi-Urriza
- Université de Pau et des Pays de l'Adour, E2S UPPA, CNRS, MIRA, IPREM, Pau, France
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25
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Capo E, Bravo AG, Soerensen AL, Bertilsson S, Pinhassi J, Feng C, Andersson AF, Buck M, Björn E. Deltaproteobacteria and Spirochaetes-Like Bacteria Are Abundant Putative Mercury Methylators in Oxygen-Deficient Water and Marine Particles in the Baltic Sea. Front Microbiol 2020; 11:574080. [PMID: 33072037 PMCID: PMC7536318 DOI: 10.3389/fmicb.2020.574080] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Accepted: 08/25/2020] [Indexed: 11/13/2022] Open
Abstract
Methylmercury (MeHg), a neurotoxic compound biomagnifying in aquatic food webs, can be a threat to human health via fish consumption. However, the composition and distribution of the microbial communities mediating the methylation of mercury (Hg) to MeHg in marine systems remain largely unknown. In order to fill this knowledge gap, we used the Baltic Sea Reference Metagenome (BARM) dataset to study the abundance and distribution of the genes involved in Hg methylation (the hgcAB gene cluster). We determined the relative abundance of the hgcAB genes and their taxonomic identity in 81 brackish metagenomes that cover spatial, seasonal and redox variability in the Baltic Sea water column. The hgcAB genes were predominantly detected in anoxic water, but some hgcAB genes were also detected in hypoxic and normoxic waters. Phylogenetic analysis identified putative Hg methylators within Deltaproteobacteria, in oxygen-deficient water layers, but also Spirochaetes-like and Kiritimatiellaeota-like bacteria. Higher relative quantities of hgcAB genes were found in metagenomes from marine particles compared to free-living communities in anoxic water, suggesting that such particles are hotspot habitats for Hg methylators in oxygen-depleted seawater. Altogether, our work unveils the diversity of the microorganisms with the potential to mediate MeHg production in the Baltic Sea and pinpoint the important ecological niches for these microorganisms within the marine water column.
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Affiliation(s)
- Eric Capo
- Department of Chemistry, Umeå University, Umeå, Sweden.,Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden
| | - Andrea G Bravo
- Institut de Ciències del Mar (ICM-CSIC), Barcelona, Spain
| | - Anne L Soerensen
- Department of Environmental Research and Monitoring, Swedish Museum of Natural History, Stockholm, Sweden
| | - Stefan Bertilsson
- Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden
| | - Jarone Pinhassi
- Centre for Ecology and Evolution in Microbial Model Systems - EEMiS, Linnaeus University, Kalmar, Sweden
| | - Caiyan Feng
- Department of Chemistry, Umeå University, Umeå, Sweden
| | - Anders F Andersson
- Department of Gene Technology, Science for Life Laboratory, KTH Royal Institute of Technology, Solna, Sweden
| | - Moritz Buck
- Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden
| | - Erik Björn
- Department of Chemistry, Umeå University, Umeå, Sweden
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26
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McDaniel EA, Peterson BD, Stevens SLR, Tran PQ, Anantharaman K, McMahon KD. Expanded Phylogenetic Diversity and Metabolic Flexibility of Mercury-Methylating Microorganisms. mSystems 2020; 5:e00299-20. [PMID: 32817383 PMCID: PMC7438021 DOI: 10.1128/msystems.00299-20] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Accepted: 07/29/2020] [Indexed: 11/23/2022] Open
Abstract
Methylmercury is a potent bioaccumulating neurotoxin that is produced by specific microorganisms that methylate inorganic mercury. Methylmercury production in diverse anaerobic bacteria and archaea was recently linked to the hgcAB genes. However, the full phylogenetic and metabolic diversity of mercury-methylating microorganisms has not been fully unraveled due to the limited number of cultured experimentally verified methylators and the limitations of primer-based molecular methods. Here, we describe the phylogenetic diversity and metabolic flexibility of putative mercury-methylating microorganisms by hgcAB identification in publicly available isolate genomes and metagenome-assembled genomes (MAGs) as well as novel freshwater MAGs. We demonstrate that putative mercury methylators are much more phylogenetically diverse than previously known and that hgcAB distribution among genomes is most likely due to several independent horizontal gene transfer events. The microorganisms we identified possess diverse metabolic capabilities spanning carbon fixation, sulfate reduction, nitrogen fixation, and metal resistance pathways. We identified 111 putative mercury methylators in a set of previously published permafrost metatranscriptomes and demonstrated that different methylating taxa may contribute to hgcA expression at different depths. Overall, we provide a framework for illuminating the microbial basis of mercury methylation using genome-resolved metagenomics and metatranscriptomics to identify putative methylators based upon hgcAB presence and describe their putative functions in the environment.IMPORTANCE Accurately assessing the production of bioaccumulative neurotoxic methylmercury by characterizing the phylogenetic diversity, metabolic functions, and activity of methylators in the environment is crucial for understanding constraints on the mercury cycle. Much of our understanding of methylmercury production is based on cultured anaerobic microorganisms within the Deltaproteobacteria, Firmicutes, and Euryarchaeota. Advances in next-generation sequencing technologies have enabled large-scale cultivation-independent surveys of diverse and poorly characterized microorganisms from numerous ecosystems. We used genome-resolved metagenomics and metatranscriptomics to highlight the vast phylogenetic and metabolic diversity of putative mercury methylators and their depth-discrete activities in thawing permafrost. This work underscores the importance of using genome-resolved metagenomics to survey specific putative methylating populations of a given mercury-impacted ecosystem.
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Affiliation(s)
- Elizabeth A McDaniel
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Benjamin D Peterson
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Environmental Chemistry and Technology Program, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Sarah L R Stevens
- Wisconsin Institute for Discovery, University of Wisconsin-Madison, Madison, Wisconsin, USA
- American Family Insurance Data Science Institute, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Patricia Q Tran
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Department of Integrative Biology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Karthik Anantharaman
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Katherine D McMahon
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Department of Civil and Environmental Engineering, University of Wisconsin-Madison, Madison, Wisconsin, USA
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27
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Azaroff A, Goñi Urriza M, Gassie C, Monperrus M, Guyoneaud R. Marine mercury-methylating microbial communities from coastal to Capbreton Canyon sediments (North Atlantic Ocean). ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2020; 262:114333. [PMID: 32443198 DOI: 10.1016/j.envpol.2020.114333] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2019] [Revised: 03/01/2020] [Accepted: 03/04/2020] [Indexed: 06/11/2023]
Abstract
Microbial mercury (Hg) methylation transforms inorganic mercury to neurotoxic methylmercury (MeHg) mainly in aquatic anoxic environments. Sampling challenges in marine ecosystems, particularly in submarine canyons, leads to a lack of knowledge about the Hg methylating microbia in marine sediments. A previous study showed an enrichment of mercury species in sediments from the Capbreton Canyon where both geochemical parameters and microbial activities constrained the net MeHg production. In order to characterize Hg-methylating microbial communities from coastal to deeper sediments, we analysed the diversity of microorganisms' (16S rDNA-based sequencing) and Hg methylators (hgcA based cloning and sequencing). Both, 16S rDNA and hgcA gene analysis demonstrated that the putative Hg-methylating prokaryotes were likely within the Deltaproteobacteria, dominated by sulfur-compounds based reducing bacteria (mainly sulfate reducers). Additionally, others clades were also identified as carrying HgcA gene, such as, Chloroflexi, Spirochaetes, Elusimicrobia, PVC superphylum (Plantomycetes, Verrucomicrobia and Chlamydiae) and Euryarchaea. Nevertheless, 61% of the hgcA sequences were not assigned to specific clade, indicating that further studies are needed to understand the implication of new microorganisms carrying hgcA in the Hg methylation in marine environments. These first results suggest that sulfur cycle drives the Hg-methylation in marine ecosystem.
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Affiliation(s)
- Alyssa Azaroff
- Universite de Pau et des Pays de l'Adour, E2S UPPA, CNRS, IPREM-MIRA, UMR 5254, 64600 Anglet, France
| | - Marisol Goñi Urriza
- Universite de Pau et des Pays de l'Adour, E2S UPPA, CNRS, IPREM-MIRA Environmental Microbiology, UMR 5254, 64000, Pau, France
| | - Claire Gassie
- Universite de Pau et des Pays de l'Adour, E2S UPPA, CNRS, IPREM-MIRA Environmental Microbiology, UMR 5254, 64000, Pau, France
| | - Mathilde Monperrus
- Universite de Pau et des Pays de l'Adour, E2S UPPA, CNRS, IPREM-MIRA, UMR 5254, 64600 Anglet, France
| | - Rémy Guyoneaud
- Universite de Pau et des Pays de l'Adour, E2S UPPA, CNRS, IPREM-MIRA Environmental Microbiology, UMR 5254, 64000, Pau, France.
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28
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Villar E, Cabrol L, Heimbürger-Boavida LE. Widespread microbial mercury methylation genes in the global ocean. ENVIRONMENTAL MICROBIOLOGY REPORTS 2020. [PMID: 32090489 DOI: 10.1101/648329] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Methylmercury is a neurotoxin that bioaccumulates from seawater to high concentrations in marine fish, putting human and ecosystem health at risk. High methylmercury levels have been found in the oxic subsurface waters of all oceans, but only anaerobic microorganisms have been shown to efficiently produce methylmercury in anoxic environments. The microaerophilic nitrite-oxidizing bacteria Nitrospina have previously been suggested as possible mercury methylating bacteria in Antarctic sea ice. However, the microorganisms responsible for processing inorganic mercury into methylmercury in oxic seawater remain unknown. Here, we show metagenomic and metatranscriptomic evidence that the genetic potential for microbial methylmercury production is widespread in oxic seawater. We find high abundance and expression of the key mercury methylating genes hgcAB across all ocean basins, corresponding to the taxonomic relatives of known mercury methylating bacteria from Deltaproteobacteria, Firmicutes and Chloroflexi. Our results identify Nitrospina as the predominant and widespread microorganism carrying and actively expressing hgcAB. The highest hgcAB abundance and expression occurs in the oxic subsurface waters of the global ocean where the highest MeHg concentrations are typically observed.
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Affiliation(s)
- Emilie Villar
- Aix Marseille Université, Univ Toulon, CNRS, IRD, Mediterranean Institute of Oceanography (MIO) UM 110, 13288, Marseille, France
- Sorbonne Université, Université Pierre et Marie Curie - Paris 6, CNRS, UMR 7144 (AD2M), Station Biologique de Roscoff, Place Georges Teissier, CS90074, Roscoff, 29688, France
| | - Léa Cabrol
- Aix Marseille Université, Univ Toulon, CNRS, IRD, Mediterranean Institute of Oceanography (MIO) UM 110, 13288, Marseille, France
- Instituto de Ecologia y Biodiversidad, Departamento de Ciencias Ecologicas, Facultad de Ciencias, Universidad de Chile, Santiago de Chile, Chile
| | - Lars-Eric Heimbürger-Boavida
- Aix Marseille Université, Univ Toulon, CNRS, IRD, Mediterranean Institute of Oceanography (MIO) UM 110, 13288, Marseille, France
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Zhao L, Meng B, Feng X. Mercury methylation in rice paddy and accumulation in rice plant: A review. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2020; 195:110462. [PMID: 32179234 DOI: 10.1016/j.ecoenv.2020.110462] [Citation(s) in RCA: 56] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Revised: 03/07/2020] [Accepted: 03/08/2020] [Indexed: 06/10/2023]
Abstract
The bioavailability and toxicity of mercury (Hg) are dependent on its chemical speciation, in which methylmercury (MeHg) is the most toxic compound. Inorganic Hg can be transformed into MeHg in anaerobic conditions. Subsequent accumulation and biomagnification in the food chain pose a potential threat to human health. Previous studies have confirmed that paddy soil is an important site for MeHg production, and rice fields are an important source of MeHg in terrestrial ecosystems. Rice (Oryza sativa L.) is recently confirmed as a potential bioaccumulator plant of MeHg. Understanding the behaviour of Hg in rice paddies is important, particularly the mechanisms involved in Hg sources, uptake, toxicity, detoxification, and accumulation in crops. This review highlights the issue of MeHg-contaminated rice, and presents the current understanding of the Hg cycling in the rice paddy ecosystem, including the mechanism and processes of Hg species accumulation in rice plants and Hg methylation/demethylation processes in rice paddies and the primary controlling factors. The review also identified various research gaps in previous studies and proposes future research objectives to reduce the impact of Hg-contamination in rice crops.
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Affiliation(s)
- Lei Zhao
- School of Management Science, Guizhou University of Finance and Economics, Guiyang, 550025, PR China; State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550002, PR China
| | - Bo Meng
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550002, PR China.
| | - Xinbin Feng
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550002, PR China.
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30
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Villar E, Cabrol L, Heimbürger-Boavida LE. Widespread microbial mercury methylation genes in the global ocean. ENVIRONMENTAL MICROBIOLOGY REPORTS 2020; 12:277-287. [PMID: 32090489 DOI: 10.1111/1758-2229.12829] [Citation(s) in RCA: 57] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2019] [Revised: 02/04/2020] [Accepted: 02/07/2020] [Indexed: 05/16/2023]
Abstract
Methylmercury is a neurotoxin that bioaccumulates from seawater to high concentrations in marine fish, putting human and ecosystem health at risk. High methylmercury levels have been found in the oxic subsurface waters of all oceans, but only anaerobic microorganisms have been shown to efficiently produce methylmercury in anoxic environments. The microaerophilic nitrite-oxidizing bacteria Nitrospina have previously been suggested as possible mercury methylating bacteria in Antarctic sea ice. However, the microorganisms responsible for processing inorganic mercury into methylmercury in oxic seawater remain unknown. Here, we show metagenomic and metatranscriptomic evidence that the genetic potential for microbial methylmercury production is widespread in oxic seawater. We find high abundance and expression of the key mercury methylating genes hgcAB across all ocean basins, corresponding to the taxonomic relatives of known mercury methylating bacteria from Deltaproteobacteria, Firmicutes and Chloroflexi. Our results identify Nitrospina as the predominant and widespread microorganism carrying and actively expressing hgcAB. The highest hgcAB abundance and expression occurs in the oxic subsurface waters of the global ocean where the highest MeHg concentrations are typically observed.
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Affiliation(s)
- Emilie Villar
- Aix Marseille Université, Univ Toulon, CNRS, IRD, Mediterranean Institute of Oceanography (MIO) UM 110, 13288, Marseille, France
- Sorbonne Université, Université Pierre et Marie Curie - Paris 6, CNRS, UMR 7144 (AD2M), Station Biologique de Roscoff, Place Georges Teissier, CS90074, Roscoff, 29688, France
| | - Léa Cabrol
- Aix Marseille Université, Univ Toulon, CNRS, IRD, Mediterranean Institute of Oceanography (MIO) UM 110, 13288, Marseille, France
- Instituto de Ecologia y Biodiversidad, Departamento de Ciencias Ecologicas, Facultad de Ciencias, Universidad de Chile, Santiago de Chile, Chile
| | - Lars-Eric Heimbürger-Boavida
- Aix Marseille Université, Univ Toulon, CNRS, IRD, Mediterranean Institute of Oceanography (MIO) UM 110, 13288, Marseille, France
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31
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Bravo AG, Cosio C. Biotic formation of methylmercury: A bio-physico-chemical conundrum. LIMNOLOGY AND OCEANOGRAPHY 2020; 65:1010-1027. [PMID: 32612306 PMCID: PMC7319479 DOI: 10.1002/lno.11366] [Citation(s) in RCA: 64] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Revised: 09/17/2019] [Accepted: 10/02/2019] [Indexed: 05/11/2023]
Abstract
Mercury (Hg) is a natural and widespread trace metal, but is considered a priority pollutant, particularly its organic form methylmercury (MMHg), because of human's exposure to MMHg through fish consumption. Pioneering studies showed the methylation of divalent Hg (HgII) to MMHg to occur under oxygen-limited conditions and to depend on the activity of anaerobic microorganisms. Recent studies identified the hgcAB gene cluster in microorganisms with the capacity to methylate HgII and unveiled a much wider range of species and environmental conditions producing MMHg than previously expected. Here, we review the recent knowledge and approaches used to understand HgII-methylation, microbial biodiversity and activity involved in these processes, and we highlight the current limits for predicting MMHg concentrations in the environment. The available data unveil the fact that HgII methylation is a bio-physico-chemical conundrum in which the efficiency of biological HgII methylation appears to depend chiefly on HgII and nutrients availability, the abundance of electron acceptors such as sulfate or iron, the abundance and composition of organic matter as well as the activity and structure of the microbial community. An increased knowledge of the relationship between microbial community composition, physico-chemical conditions, MMHg production, and demethylation is necessary to predict variability in MMHg concentrations across environments.
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Affiliation(s)
- Andrea G. Bravo
- Department of Marine Biology and Oceanography, Institute of Marine SciencesSpanish National Research Council (CSIC)BarcelonaSpain
| | - Claudia Cosio
- Université de Reims Champagne Ardennes, UMR‐I 02 INERIS‐URCA‐ULH SEBIO, Unité Stress Environnementaux et BIOsurveillance des milieux aquatiquesReimsFrance
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Thomas SA, Mishra B, Myneni SCB. Cellular Mercury Coordination Environment, and Not Cell Surface Ligands, Influence Bacterial Methylmercury Production. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2020; 54:3960-3968. [PMID: 32097551 DOI: 10.1021/acs.est.9b05915] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The conversion of inorganic mercury (Hg(II)) to methylmercury (MeHg) is central to the understanding of Hg toxicity in the environment. Hg methylation occurs in the cytosol of certain obligate anaerobic bacteria and archaea possessing the hgcAB gene cluster. However, the processes involved in Hg(II) biouptake and methylation are not well understood. Here, we examined the role of cell surface thiols, cellular ligands with the highest affinity for Hg(II) that are located at the interface between the outer membrane and external medium, on the sorption and methylation of Hg(II) by Geobacter sulfurreducens. The effect of added cysteine (Cys), which is known to greatly enhance Hg(II) biouptake and methylation, was also explored. By quantitatively blocking surface thiols with a thiol binding ligand (qBBr), we show that surface thiols have no significant effect on Hg(II) methylation, regardless of Cys addition. The results also identify a significant amount of cell-associated Hg-S3/S4 species, as studied by high energy-resolution X-ray absorption near edge structure (HR-XANES) spectroscopy, under conditions of high MeHg production (with Cys addition). In contrast, Hg-S2 are the predominant species during low MeHg production. Hg-S3/S4 species may be related to enhanced Hg(II) biouptake or the ability of Hg(II) to become methylated by HgcAB and should be further explored in this context.
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Affiliation(s)
- Sara A Thomas
- Department of Geosciences, Princeton University, Guyot Hall, Princeton, New Jersey 08544, United States
| | - Bhoopesh Mishra
- School of Chemical and Process Engineering, University of Leeds, Leeds LS2 9JT, U.K
| | - Satish C B Myneni
- Department of Geosciences, Princeton University, Guyot Hall, Princeton, New Jersey 08544, United States
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Influence of Macrophyte and Gut Microbiota on Mercury Contamination in Fish: A Microcosms Study. APPLIED SCIENCES-BASEL 2020. [DOI: 10.3390/app10041500] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The freshwater lakes of southwestern France are subject to the development of invasive macrophytes which are associated with mercury (Hg) contamination of the food web. The aim of this study was to determine the bioavailability of methylmercury (MeHg) produced by plant roots in aquatic ecosystems. A microcosm experiment was performed using isotopically enriched inorganic Hg at environmental concentrations (1 µg 199IHg·L−1). For all conditions, total Hg in fish as well as Hg species associated with different compartments (water, sediments, plant roots, fish) were analyzed by gas chromatography-inductively coupled plasma-mass spectrometry (GC-ICP-MS). In addition, sediment, plants, and fish gut microbiota were studied by MiSEQ sequencing. Some strains were isolated and tested for their ability to methylate Hg. The results revealed 199MeHg production in plant roots and the presence of this form in fish (tissues and gut), highlighting a MeHg trophic transfer. Moreover, methylator bacteria were identified from the gut contents of the fish when they were in the presence of plants. Some of them were related to bacteria found in the plant roots. On the basis of these results, the transfer of MeHg and bacteria from plants to fish is highlighted; in addition, Hg methylation is strongly suspected in the fish gut, potentially increasing the Hg bioaccumulation.
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Goñi-Urriza M, Klopp C, Ranchou-Peyruse M, Ranchou-Peyruse A, Monperrus M, Khalfaoui-Hassani B, Guyoneaud R. Genome insights of mercury methylation among Desulfovibrio and Pseudodesulfovibrio strains. Res Microbiol 2019; 171:3-12. [PMID: 31655199 DOI: 10.1016/j.resmic.2019.10.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2019] [Revised: 10/10/2019] [Accepted: 10/11/2019] [Indexed: 01/28/2023]
Abstract
Mercury methylation converts inorganic mercury into the toxic methylmercury, and the consequences of this transformation are worrisome for human health and the environment. This process is performed by anaerobic microorganisms, such as several strains related to Pseudodesulfovibrio and Desulfovibrio genera. In order to provide new insights into the molecular mechanisms of mercury methylation, we performed a comparative genomic analysis on mercury methylators and non-methylators from (Pseudo)Desulfovibrio strains. Our results showed that (Pseudo)Desulfovibrio species are phylogenetically and metabolically distant and consequently, these genera should be divided into various genera. Strains able to perform methylation are affiliated with one branch of the phylogenetic tree, but, except for hgcA and hgcB genes, no other specific genetic markers were found among methylating strains. hgcA and hgcB genes can be found adjacent or separated, but proximity between those genes does not promote higher mercury methylation. In addition, close examination of the non-methylator Pseudodesulfovibrio piezophilus C1TLV30 strain, showed a syntenic structure that suggests a recombination event and may have led to hgcB depletion. The genomic analyses identify also arsR gene coding for a putative regulator upstream hgcA. Both genes are cotranscribed suggesting a role of ArsR in hgcA expression and probably a role in mercury methylation.
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Affiliation(s)
- Marisol Goñi-Urriza
- Environmental Microbiology, CNRS/UNIV PAU & PAYS ADOUR/E2S UPPA, Institut des Sciences Analytiques et de Physicochimie pour l'Environnement et les Matériaux, IPREM, UMR5254, Pau, France.
| | - Christophe Klopp
- Plateforme Bioinformatique Genotoul, UR875 Biométrie et Intelligence Artificielle, INRA, Castanet-Tolosan, France.
| | - Magali Ranchou-Peyruse
- Environmental Microbiology, CNRS/UNIV PAU & PAYS ADOUR/E2S UPPA, Institut des Sciences Analytiques et de Physicochimie pour l'Environnement et les Matériaux, IPREM, UMR5254, Pau, France.
| | - Anthony Ranchou-Peyruse
- Environmental Microbiology, CNRS/UNIV PAU & PAYS ADOUR/E2S UPPA, Institut des Sciences Analytiques et de Physicochimie pour l'Environnement et les Matériaux, IPREM, UMR5254, Pau, France.
| | - Mathilde Monperrus
- CNRS/UNIV PAU & PAYS ADOUR/E2S UPPA, Institut des Sciences Analytiques et de Physicochimie pour l'Environnement et les Matériaux, IPREM, UMR5254, Anglet, France.
| | - Bahia Khalfaoui-Hassani
- Environmental Microbiology, CNRS/UNIV PAU & PAYS ADOUR/E2S UPPA, Institut des Sciences Analytiques et de Physicochimie pour l'Environnement et les Matériaux, IPREM, UMR5254, Pau, France.
| | - Rémy Guyoneaud
- Environmental Microbiology, CNRS/UNIV PAU & PAYS ADOUR/E2S UPPA, Institut des Sciences Analytiques et de Physicochimie pour l'Environnement et les Matériaux, IPREM, UMR5254, Pau, France.
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Christensen GA, Gionfriddo CM, King AJ, Moberly JG, Miller CL, Somenahally AC, Callister SJ, Brewer H, Podar M, Brown SD, Palumbo AV, Brandt CC, Wymore AM, Brooks SC, Hwang C, Fields MW, Wall JD, Gilmour CC, Elias DA. Determining the Reliability of Measuring Mercury Cycling Gene Abundance with Correlations with Mercury and Methylmercury Concentrations. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:8649-8663. [PMID: 31260289 DOI: 10.1021/acs.est.8b06389] [Citation(s) in RCA: 57] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Methylmercury (MeHg) is a bioaccumulative toxic contaminant in many ecosystems, but factors governing its production are poorly understood. Recent work has shown that the anaerobic microbial conversion of mercury (Hg) to MeHg requires the Hg-methylation genes hgcAB and that these genes can be used as biomarkers in PCR-based estimators of Hg-methylator abundance. In an effort to determine reliable methods for assessing hgcA abundance and diversity and linking them to MeHg concentrations, multiple approaches were compared including metagenomic shotgun sequencing, 16S rRNA gene pyrosequencing and cloning/sequencing hgcAB gene products. Hg-methylator abundance was also determined by quantitative hgcA qPCR amplification and metaproteomics for comparison to the above measurements. Samples from eight sites were examined covering a range of total Hg (HgT; 0.03-14 mg kg-1 dry wt. soil) and MeHg (0.05-27 μg kg-1 dry wt. soil) concentrations. In the metagenome and amplicon sequencing of hgcAB diversity, the Deltaproteobacteria were the dominant Hg-methylators while Firmicutes and methanogenic Archaea were typically ∼50% less abundant. This was consistent with metaproteomics estimates where the Deltaproteobacteria were steadily higher. The 16S rRNA gene pyrosequencing did not have sufficient resolution to identify hgcAB+ species. Metagenomic and hgcAB results were similar for Hg-methylator diversity and clade-specific qPCR-based approaches for hgcA are only appropriate when comparing the abundance of a particular clade across various samples. Weak correlations between Hg-methylating bacteria and soil Hg concentrations were observed for similar environmental samples, but overall total Hg and MeHg concentrations poorly correlated with Hg-cycling genes.
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Affiliation(s)
- Geoff A Christensen
- Biosciences Division , Oak Ridge National Laboratory , Oak Ridge , Tennessee 37831-6342 , United States
| | - Caitlin M Gionfriddo
- Biosciences Division , Oak Ridge National Laboratory , Oak Ridge , Tennessee 37831-6342 , United States
| | - Andrew J King
- Biosciences Division , Oak Ridge National Laboratory , Oak Ridge , Tennessee 37831-6342 , United States
| | - James G Moberly
- College of Engineering , University of Idaho , Moscow , Idaho 83844 , United States
| | - Carrie L Miller
- School of Theoretical and Applied Science , Ramapo College of New Jersey , Mahwah , New Jersey 07430 , United States
| | - Anil C Somenahally
- Department of Soil and Crop Sciences , Texas A&M University , Overton , Texas 77843-2474 , United States
| | - Stephen J Callister
- Biological Sciences Division , Pacific Northwest National Laboratory , Richland , Washington 99352 , United States
| | - Heather Brewer
- Biological Sciences Division , Pacific Northwest National Laboratory , Richland , Washington 99352 , United States
| | - Mircea Podar
- Biosciences Division , Oak Ridge National Laboratory , Oak Ridge , Tennessee 37831-6342 , United States
| | - Steven D Brown
- Biosciences Division , Oak Ridge National Laboratory , Oak Ridge , Tennessee 37831-6342 , United States
| | - Anthony V Palumbo
- Biosciences Division , Oak Ridge National Laboratory , Oak Ridge , Tennessee 37831-6342 , United States
| | - Craig C Brandt
- Biosciences Division , Oak Ridge National Laboratory , Oak Ridge , Tennessee 37831-6342 , United States
| | - Ann M Wymore
- Biosciences Division , Oak Ridge National Laboratory , Oak Ridge , Tennessee 37831-6342 , United States
| | - Scott C Brooks
- Environmental Sciences Division , Oak Ridge National Laboratory , Oak Ridge , Tennessee 37830 , United States
| | - Chiachi Hwang
- Center for Biofilm Engineering , Montana State University , Bozeman , Montana 59717 , United States
| | - Matthew W Fields
- Department of Microbiology and Immunology , Montana State University , Bozeman , Montana 59717 , United States
- Center for Biofilm Engineering , Montana State University , Bozeman , Montana 59717 , United States
| | - Judy D Wall
- Department of Biochemistry , University of Missouri , Columbia , Missouri 65211 , United States
| | - Cynthia C Gilmour
- Smithsonian Environmental Research Center , Edgewater , Maryland 21037 , United States
| | - Dwayne A Elias
- Biosciences Division , Oak Ridge National Laboratory , Oak Ridge , Tennessee 37831-6342 , United States
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36
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Adediran GA, Liem-Nguyen V, Song Y, Schaefer JK, Skyllberg U, Björn E. Microbial Biosynthesis of Thiol Compounds: Implications for Speciation, Cellular Uptake, and Methylation of Hg(II). ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:8187-8196. [PMID: 31257868 DOI: 10.1021/acs.est.9b01502] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Cellular uptake of inorganic divalent mercury (Hg(II)) is a key step in microbial formation of neurotoxic methylmercury (MeHg), but the mechanisms remain largely unidentified. We show that the iron reducing bacterium Geobacter sulfurreducens produces and exports appreciable amounts of low molecular mass thiol (LMM-RSH) compounds reaching concentrations of about 100 nM in the assay medium. These compounds largely control the chemical speciation and bioavailability of Hg(II) by the formation of Hg(LMM-RS)2 complexes (primarily with cysteine) in assays without added thiols. By characterizing these effects, we show that the thermodynamic stability of Hg(II)-complexes is a principal controlling factor for Hg(II) methylation by this bacterium such that less stable complexes with mixed ligation involving LMM-RSH, OH-, and Cl- are methylated at higher rates than the more stable Hg(LMM-RS)2 complexes. The Hg(II) methylation rate across different Hg(LMM-RS)2 compounds is also influenced by the chemical structure of the complexes. In contrast to the current perception of microbial uptake of Hg, our results adhere to generalized theories for metal biouptake based on metal complexation with cell surface ligands and refine the mechanistic understanding of Hg(II) availability for microbial methylation.
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Affiliation(s)
| | - Van Liem-Nguyen
- Department of Chemistry , Umeå University , SE- 90187 Umeå , Sweden
- School of Science and Technology , Örebro University , SE-70182 Örebro , Sweden
| | - Yu Song
- Department of Forest Ecology and Management , Swedish University of Agricultural Sciences , SE-901 83 Umeå , Sweden
| | - Jeffra K Schaefer
- Department of Environmental Sciences , Rutgers University , 14 College Farm Road , New Brunswick , New Jersey 08901 , United States
| | - Ulf Skyllberg
- Department of Forest Ecology and Management , Swedish University of Agricultural Sciences , SE-901 83 Umeå , Sweden
| | - Erik Björn
- Department of Chemistry , Umeå University , SE- 90187 Umeå , Sweden
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Regnell O, Watras CJ. Microbial Mercury Methylation in Aquatic Environments: A Critical Review of Published Field and Laboratory Studies. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:4-19. [PMID: 30525497 DOI: 10.1021/acs.est.8b02709] [Citation(s) in RCA: 112] [Impact Index Per Article: 22.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Methylmercury (MeHg) is an environmental contaminant of concern because it biomagnifies in aquatic food webs and poses a health hazard to aquatic biota, piscivorous wildlife and humans. The dominant source of MeHg to freshwater systems is the methylation of inorganic Hg (IHg) by anaerobic microorganisms; and it is widely agreed that in situ rates of Hg methylation depend on two general factors: the activity of Hg methylators and their uptake of IHg. A large body of research has focused on the biogeochemical processes that regulate these two factors in nature; and studies conducted within the past ten years have made substantial progress in identifying the genetic basis for intracellular methylation and defining the processes that govern the cellular uptake of IHg. Current evidence indicates that all Hg methylating anaerobes possess the gene pair hgcAB that encodes proteins essential for Hg methylation. These genes are found in a large variety of anaerobes, including iron reducers and methanogens; but sulfate reduction is the metabolic process most often reported to show strong links to MeHg production. The uptake of Hg substrate prior to methylation may occur by passive or active transport, or by a combination of both. Competitive inhibition of Hg uptake by Zn speaks in favor of active transport and suggests that essential metal transporters are involved. Shortly after its formation, MeHg is typically released from cells, but the efflux mechanisms are unknown. Although methylation facilitates Hg depuration from the cell, evidence suggests that the hgcAB genes are not induced or favored by Hg contamination. Instead, high MeHg production can be linked to high Hg bioavailability as a result of the formation of Hg(SH)2, HgS nanoparticles, and Hg-thiol complexes. It is also possible that sulfidic conditions require strong essential metal uptake systems that inadvertently bring Hg into the cytoplasm of Hg methylating microbes. In comparison with freshwaters, Hg methylation in open ocean waters appears less restricted to anoxic environments. It does seem to occur mainly in oxygen deficient zones (ODZs), and possibly within anaerobic microzones of settling organic matter, but MeHg (CH3Hg+) and Me2Hg ((CH3)2Hg) have been shown to form also in surface water samples from the euphotic zone. Future studies may disclose whether several different pathways lead to Hg methylation in marine waters and explain why Me2Hg is a significant Hg species in oceans but seemingly not in most freshwaters.
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Affiliation(s)
- Olof Regnell
- Department of Biology/Aquatic Ecology , Lund University , SE-223 62 Lund , Sweden
| | - Carl J Watras
- Bureau of Water Quality , Wisconsin Department of Natural Resources , Madison , Wisconsin 53703 , United States
- Center for Limnology , University of Wisconsin-Madison , 3110 Trout Lake Station Drive , Boulder Junction , Wisconsin 54512 , United States
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38
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Liu YR, Johs A, Bi L, Lu X, Hu HW, Sun D, He JZ, Gu B. Unraveling Microbial Communities Associated with Methylmercury Production in Paddy Soils. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2018; 52:13110-13118. [PMID: 30335986 DOI: 10.1021/acs.est.8b03052] [Citation(s) in RCA: 97] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Rice consumption is now recognized as an important pathway of human exposure to the neurotoxin methylmercury (MeHg), particularly in countries where rice is a staple food. Although the discovery of a two-gene cluster hgcAB has linked Hg methylation to several phylogenetically diverse groups of anaerobic microorganisms converting inorganic mercury (Hg) to MeHg, the prevalence and diversity of Hg methylators in microbial communities of rice paddy soils remain unclear. We characterized the abundance and distribution of hgcAB genes using third-generation PacBio long-read sequencing and Illumina short-read metagenomic sequencing, in combination with quantitative PCR analyses in several mine-impacted paddy soils from southwest China. Both Illumina and PacBio sequencing analyses revealed that Hg methylating communities were dominated by iron-reducing bacteria (i.e., Geobacter) and methanogens, with a relatively low abundance of hgcA + sulfate-reducing bacteria in the soil. A positive correlation was observed between the MeHg content in soil and the relative abundance of Geobacter carrying the hgcA gene. Phylogenetic analysis also uncovered some hgcAB sequences closely related to three novel Hg methylators, Geobacter anodireducens, Desulfuromonas sp. DDH964, and Desulfovibrio sp. J2, among which G. anodireducens was validated for its ability to methylate Hg. These findings shed new light on microbial community composition and major clades likely driving Hg methylation in rice paddy soils.
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Affiliation(s)
- Yu-Rong Liu
- State Key Laboratory of Urban and Regional Ecology , Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences , Beijing Shi 100085 , China
| | - Alexander Johs
- Environmental Sciences Division , Oak Ridge National Laboratory , Oak Ridge , Tennessee 37831 , United States
| | - Li Bi
- State Key Laboratory of Urban and Regional Ecology , Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences , Beijing Shi 100085 , China
| | - Xia Lu
- Environmental Sciences Division , Oak Ridge National Laboratory , Oak Ridge , Tennessee 37831 , United States
| | - Hang-Wei Hu
- Department of Veterinary and Agricultural Sciences , The University of Melbourne , Melbourne , Victoria 3004 , Australia
| | - Dan Sun
- Ocean College , Zhejiang University , Zhejiang , 310058 , China
| | - Ji-Zheng He
- State Key Laboratory of Urban and Regional Ecology , Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences , Beijing Shi 100085 , China
- Department of Veterinary and Agricultural Sciences , The University of Melbourne , Melbourne , Victoria 3004 , Australia
| | - Baohua Gu
- Environmental Sciences Division , Oak Ridge National Laboratory , Oak Ridge , Tennessee 37831 , United States
- Department of Biosystems Engineering and Soil Science , University of Tennessee , Knoxville , Tennessee 37996 , United States
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Bouchet S, Goñi-Urriza M, Monperrus M, Guyoneaud R, Fernandez P, Heredia C, Tessier E, Gassie C, Point D, Guédron S, Achá D, Amouroux D. Linking Microbial Activities and Low-Molecular-Weight Thiols to Hg Methylation in Biofilms and Periphyton from High-Altitude Tropical Lakes in the Bolivian Altiplano. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2018; 52:9758-9767. [PMID: 30037219 DOI: 10.1021/acs.est.8b01885] [Citation(s) in RCA: 54] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
The sources and factors controlling concentrations of monomethylmercury (MMHg) in aquatic ecosystems need to be better understood. Here, we investigated Hg transformations in sediments, periphyton associated with green algae's or aquatic plants, and benthic biofilms from the Lake Titicaca hydrosystem and compared them to the occurrence of active methylating microorganisms and extracellular Hg ligands. Intense Hg methylation was found in benthic biofilms and green algae's periphyton, while it remained low in sediments and aquatic plants' periphyton. Demethylation varied between compartments but remained overall in the same range. Hg methylation was mainly carried out by sulfate reducers, although methanogens also played a role. Its variability between compartments was first explained by the presence or absence of the hgcAB genes. Next, both benthic biofilm and green algae's periphyton exhibited a great diversity of extracellular low-molecular-weight (LMW) thiols (13 or 14 compounds) present at a range of a few nmol L-1 or μmol L-1 but clearly dominated by cysteine and 3-mercaptopropionic acid. Hg methylation was overall positively correlated to the total thiol concentrations, albeit to different extents according to the compartment and conditions. This work is the first examining the interplay between active methylating bacterial communities and extracellular ligands in heterotrophic biofilms and supports the involvement of LMW thiols in Hg methylation in real aquatic systems.
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Affiliation(s)
- Sylvain Bouchet
- CNRS/Univ Pau & Pays Adour , Institut des Sciences Analytiques et de Physico-Chimie pour l'Environnement et les Matériaux , UMR5254, 64000 , Pau , France
| | - Marisol Goñi-Urriza
- CNRS/Univ Pau & Pays Adour , Institut des Sciences Analytiques et de Physico-Chimie pour l'Environnement et les Matériaux , UMR5254, 64000 , Pau , France
| | - Mathilde Monperrus
- CNRS/Univ Pau & Pays Adour , Institut des Sciences Analytiques et de Physico-Chimie pour l'Environnement et les Matériaux , UMR5254, 64000 , Pau , France
| | - Rémy Guyoneaud
- CNRS/Univ Pau & Pays Adour , Institut des Sciences Analytiques et de Physico-Chimie pour l'Environnement et les Matériaux , UMR5254, 64000 , Pau , France
| | - Pablo Fernandez
- Unidad de Calidad Ambiental (UCA) , Instituto de Ecologia, Universidad Mayor de San Andres, Campus Universitario de Cota Cota , Calle 27 , 00000 La Paz , Bolivia
| | - Carlos Heredia
- Unidad de Calidad Ambiental (UCA) , Instituto de Ecologia, Universidad Mayor de San Andres, Campus Universitario de Cota Cota , Calle 27 , 00000 La Paz , Bolivia
| | - Emmanuel Tessier
- CNRS/Univ Pau & Pays Adour , Institut des Sciences Analytiques et de Physico-Chimie pour l'Environnement et les Matériaux , UMR5254, 64000 , Pau , France
| | - Claire Gassie
- CNRS/Univ Pau & Pays Adour , Institut des Sciences Analytiques et de Physico-Chimie pour l'Environnement et les Matériaux , UMR5254, 64000 , Pau , France
| | - David Point
- Unidad de Calidad Ambiental (UCA) , Instituto de Ecologia, Universidad Mayor de San Andres, Campus Universitario de Cota Cota , Calle 27 , 00000 La Paz , Bolivia
- Géosciences Environnement Toulouse, UMR5563, IRD UR 234 , Université Paul Sabatier , 14 Avenue Edouard Belin , 31400 Toulouse , France
| | - Stéphane Guédron
- Université Grenoble Alpes, Université Savoie Mont Blanc, CNRS, IRD, IFSTTAR, ISTerre , 38000 Grenoble , France
- Laboratorio de Hidroquímica , Instituto de Investigaciones Químicas, Universidad Mayor de San Andrés, Campus Universitario de Cota-Cota , casilla 3161 , 00000 La Paz , Bolivia
| | - Dario Achá
- Unidad de Calidad Ambiental (UCA) , Instituto de Ecologia, Universidad Mayor de San Andres, Campus Universitario de Cota Cota , Calle 27 , 00000 La Paz , Bolivia
| | - David Amouroux
- CNRS/Univ Pau & Pays Adour , Institut des Sciences Analytiques et de Physico-Chimie pour l'Environnement et les Matériaux , UMR5254, 64000 , Pau , France
- Unidad de Calidad Ambiental (UCA) , Instituto de Ecologia, Universidad Mayor de San Andres, Campus Universitario de Cota Cota , Calle 27 , 00000 La Paz , Bolivia
- Géosciences Environnement Toulouse, UMR5563, IRD UR 234 , Université Paul Sabatier , 14 Avenue Edouard Belin , 31400 Toulouse , France
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Qian C, Chen H, Johs A, Lu X, An J, Pierce EM, Parks JM, Elias DA, Hettich RL, Gu B. Quantitative Proteomic Analysis of Biological Processes and Responses of the Bacterium Desulfovibrio desulfuricans ND132 upon Deletion of Its Mercury Methylation Genes. Proteomics 2018; 18:e1700479. [PMID: 30009483 DOI: 10.1002/pmic.201700479] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2017] [Revised: 05/17/2018] [Indexed: 11/10/2022]
Abstract
Recent studies of microbial mercury (Hg) methylation revealed a key gene pair, hgcAB, which is essential for methylmercury (MeHg) production in the environment. However, many aspects of the mechanism and biological processes underlying Hg methylation, as well as any additional physiological functions of the hgcAB genes, remain unknown. Here, quantitative proteomics are used to identify changes in potential functional processes related to hgcAB gene deletion in the Hg-methylating bacterium Desulfovibrio desulfuricans ND132. Global proteomics analyses indicate that the wild type and ΔhgcAB strains are similar with respect to the whole proteome and the identified number of proteins, but differ significantly in the abundance of specific proteins. The authors observe changes in the abundance of proteins related to the glycolysis pathway and one-carbon metabolism, suggesting that the hgcAB gene pair is linked to carbon metabolism. Unexpectedly, the authors find that the deletion of hgcAB significantly impacts a range of metal transport proteins, specifically membrane efflux pumps such as those associated with heavy metal copper (Cu) export, leading to decreased Cu uptake in the ΔhgcAB mutant. This observation indicates possible linkages between this set of proteins and metal homeostasis in the cell. However, hgcAB gene expression is not induced by Hg, as evidenced by similarly low abundance of HgcA and HgcB proteins in the absence or presence of Hg (500 nm). Taken together, these results suggest an apparent link between HgcAB, one-carbon metabolism, and metal homeostasis, thereby providing insights for further exploration of biochemical mechanisms and biological functions of microbial Hg methylation.
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Affiliation(s)
- Chen Qian
- Chemical Sciences Division, Oak Ridge National Laboratory, 37831 Oak Ridge, TN, USA.,Graduate School of Genome Science and Technology, University of Tennessee, 37996 Knoxville, TN, USA
| | - Hongmei Chen
- Environmental Sciences Division, Oak Ridge National Laboratory, 37831 Oak Ridge, TN, USA
| | - Alexander Johs
- Environmental Sciences Division, Oak Ridge National Laboratory, 37831 Oak Ridge, TN, USA
| | - Xia Lu
- Environmental Sciences Division, Oak Ridge National Laboratory, 37831 Oak Ridge, TN, USA
| | - Jing An
- Environmental Sciences Division, Oak Ridge National Laboratory, 37831 Oak Ridge, TN, USA
| | - Eric M Pierce
- Environmental Sciences Division, Oak Ridge National Laboratory, 37831 Oak Ridge, TN, USA
| | - Jerry M Parks
- Biosciences Division, Oak Ridge National Laboratory, 37831 Oak Ridge, TN, USA
| | - Dwayne A Elias
- Biosciences Division, Oak Ridge National Laboratory, 37831 Oak Ridge, TN, USA
| | - Robert L Hettich
- Chemical Sciences Division, Oak Ridge National Laboratory, 37831 Oak Ridge, TN, USA.,Graduate School of Genome Science and Technology, University of Tennessee, 37996 Knoxville, TN, USA
| | - Baohua Gu
- Environmental Sciences Division, Oak Ridge National Laboratory, 37831 Oak Ridge, TN, USA
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Yang J, Takaoka M, Sano A, Matsuyama A, Yanase R. Vertical Distribution of Total Mercury and Mercury Methylation in a Landfill Site in Japan. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2018; 15:ijerph15061252. [PMID: 29899229 PMCID: PMC6025181 DOI: 10.3390/ijerph15061252] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Revised: 06/05/2018] [Accepted: 06/08/2018] [Indexed: 11/25/2022]
Abstract
Mercury is a neurotoxin, with certain organic forms of the element being particularly harmful to humans. The Minamata Convention was adopted to reduce the intentional use and emission of mercury. Because mercury is an element, it cannot be decomposed. Mercury-containing products and mercury used for various processes will eventually enter the waste stream, and landfill sites will become a mercury sink. While landfill sites can be a source of mercury pollution, the behavior of mercury in solid waste within a landfill site is still not fully understood. The purpose of this study was to determine the depth profile of mercury, the levels of methyl mercury (MeHg), and the factors controlling methylation in an old landfill site that received waste for over 30 years. Three sampling cores were selected, and boring sampling was conducted to a maximum depth of 18 m, which reached the bottom layer of the landfill. Total mercury (THg) and MeHg were measured in the samples to determine the characteristics of mercury at different depths. Bacterial species were identified by 16S rRNA amplification and sequencing, because the methylation process is promoted by a series of genes. It was found that the THg concentration was 19–975 ng/g, with a geometric mean of 298 ng/g, which was slightly less than the 400 ng/g concentration recorded 30 years previously. In some samples, MeHg accounted for up to 15–20% of THg, which is far greater than the general level in soils and sediments, although the source of MeHg was unclear. The genetic data indicated that hgcA was present mostly in the upper and lower layers of the three cores, merA was almost as much as hgcA, while the level of merB was hundreds of times less than those of the other two genes. A significant correlation was found between THg and MeHg, as well as between MeHg and MeHg/THg. In addition, a negative correlation was found between THg and merA. The coexistence of the three genes indicated that both methylation and demethylation processes could occur, but the lack of merB was a barrier for demethylation.
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Affiliation(s)
- Jing Yang
- Department of Environmental Engineering, Graduate School of Engineering, Kyoto University, C-kluster, Kyotodaigakukatsura, Nishikyo-ku, Kyoto 6158540, Japan.
| | - Masaki Takaoka
- Department of Environmental Engineering, Graduate School of Engineering, Kyoto University, C-kluster, Kyotodaigakukatsura, Nishikyo-ku, Kyoto 6158540, Japan.
- Graduate School of Global Environmental Studies, Kyoto University, C-kluster, Kyotodaigakukatsura, Nishikyo-ku, Kyoto 6158540, Japan.
| | - Akira Sano
- Graduate School of Global Environmental Studies, Kyoto University, C-kluster, Kyotodaigakukatsura, Nishikyo-ku, Kyoto 6158540, Japan.
| | - Akito Matsuyama
- National Institute for Minamata Disease, 4058-18 Hama, Minamata-City, Kumamoto 8670008, Japan.
| | - Ryuji Yanase
- Environmental Protection Center, Fukuoka University, 8-19-1 Nanakuma, Jonan-ku, Fukuoka 8140180, Japan.
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Ranchou-Peyruse M, Goñi-Urriza M, Guignard M, Goas M, Ranchou-Peyruse A, Guyoneaud R. Pseudodesulfovibrio hydrargyri sp. nov., a mercury-methylating bacterium isolated from a brackish sediment. Int J Syst Evol Microbiol 2018. [PMID: 29533171 DOI: 10.1099/ijsem.0.002173] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The strain BerOc1T was isolated from brackish sediments contaminated with hydrocarbons and heavy metals. This strain has been used as a model strain of sulfate-reducer to study the biomethylation of mercury. The cells are vibrio-shaped, motile and not sporulated. Phylogeny and physiological traits placed this strain within the genus Pseudodesulfovibrio. Optimal growth was obtained at 30 °C, 1.5 % NaCl and pH 6.0-7.4. The estimated G+C content of the genomic DNA was 62.6 mol%. BerOc1T used lactate, pyruvate, fumarate, ethanol and hydrogen. Terminal electron acceptors used were sulfate, sulfite, thiosulfate and DMSO. Only pyruvate could be used without a terminal electron acceptor. The major fatty acids were C18 : 0, anteiso-C15 : 0, C16 : 0 and C18 : 1ω7. The name Pseudodesulfovibrio hydrargyri sp. nov. is proposed for the type strain BerOc1T (DSM 10384T=JCM 31820T).
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Affiliation(s)
- Magali Ranchou-Peyruse
- Université de Pau et des Pays de l'Adour, CNRS, Institut des Sciences Analytiques et de Physico-Chimie pour l'Environnement et les Matériaux - MIRA, UMR 5254, 64000, Pau, France
| | - Marisol Goñi-Urriza
- Université de Pau et des Pays de l'Adour, CNRS, Institut des Sciences Analytiques et de Physico-Chimie pour l'Environnement et les Matériaux - MIRA, UMR 5254, 64000, Pau, France
| | - Marion Guignard
- Université de Pau et des Pays de l'Adour, CNRS, Institut des Sciences Analytiques et de Physico-Chimie pour l'Environnement et les Matériaux - MIRA, UMR 5254, 64000, Pau, France
| | - Marjorie Goas
- Université de Pau et des Pays de l'Adour, CNRS, Institut des Sciences Analytiques et de Physico-Chimie pour l'Environnement et les Matériaux - MIRA, UMR 5254, 64000, Pau, France
| | - Anthony Ranchou-Peyruse
- Université de Pau et des Pays de l'Adour, CNRS, Institut des Sciences Analytiques et de Physico-Chimie pour l'Environnement et les Matériaux - MIRA, UMR 5254, 64000, Pau, France
| | - Rémy Guyoneaud
- Université de Pau et des Pays de l'Adour, CNRS, Institut des Sciences Analytiques et de Physico-Chimie pour l'Environnement et les Matériaux - MIRA, UMR 5254, 64000, Pau, France
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43
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Liu X, Ma A, Zhuang G, Zhuang X. Diversity of microbial communities potentially involved in mercury methylation in rice paddies surrounding typical mercury mining areas in China. Microbiologyopen 2018. [PMID: 29527815 PMCID: PMC6079176 DOI: 10.1002/mbo3.577] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Mercury can be a serious hazard to human health, especially in paddy soils surrounding mining areas. In this study, mercury (Hg)‐methylating microbes with the potential biomarker gene hgcA were obtained from 45 paddy soil samples in mercury mining areas in Fenghuang, Wanshan, and Xunyang. In different areas, the abundance of the hgcA gene was affected by different environmental factors, including organic matter, pH, total carbon content, total nitrogen content, and total mercury content. Phylogenetic analysis showed that hgcA microbes in paddy soils were potentially members of the phyla Proteobacteria, Euryarchaeota, Chloroflexi, and two unnamed groups. Canonical correspondence analysis showed that pH and organic matter impacted the hgcA gene diversity and the microbial community structures in paddy soils. The identification of Hg‐methylating microbes may be crucial for understanding mercury methylation/demethylation processes, which would be helpful in assessing the risk of methylmercury contamination in the food chain.
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Affiliation(s)
- Xin Liu
- University of Sciences and Technology of China, Hefei, China.,CAS, Research Center for Eco-Environmental Sciences, Key Laboratory of Environmental Biotechnology, Chinese Academy of Sciences, Beijing, China
| | - Anzhou Ma
- CAS, Research Center for Eco-Environmental Sciences, Key Laboratory of Environmental Biotechnology, Chinese Academy of Sciences, Beijing, China.,College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, China
| | - Guoqiang Zhuang
- CAS, Research Center for Eco-Environmental Sciences, Key Laboratory of Environmental Biotechnology, Chinese Academy of Sciences, Beijing, China.,College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, China
| | - Xuliang Zhuang
- CAS, Research Center for Eco-Environmental Sciences, Key Laboratory of Environmental Biotechnology, Chinese Academy of Sciences, Beijing, China.,College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, China
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Carbon Amendments Alter Microbial Community Structure and Net Mercury Methylation Potential in Sediments. Appl Environ Microbiol 2018; 84:AEM.01049-17. [PMID: 29150503 PMCID: PMC5772229 DOI: 10.1128/aem.01049-17] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Accepted: 09/28/2017] [Indexed: 01/08/2023] Open
Abstract
Neurotoxic methylmercury (MeHg) is produced by anaerobic Bacteria and Archaea possessing the genes hgcAB, but it is unknown how organic substrate and electron acceptor availability impacts the distribution and abundance of these organisms. We evaluated the impact of organic substrate amendments on mercury (Hg) methylation rates, microbial community structure, and the distribution of hgcAB+ microbes with sediments. Sediment slurries were amended with short-chain fatty acids, alcohols, or a polysaccharide. Minimal increases in MeHg were observed following lactate, ethanol, and methanol amendments, while a significant decrease (∼70%) was observed with cellobiose incubations. Postincubation, microbial diversity was assessed via 16S rRNA amplicon sequencing. The presence of hgcAB+ organisms was assessed with a broad-range degenerate PCR primer set for both genes, while the presence of microbes in each of the three dominant clades of methylators (Deltaproteobacteria, Firmicutes, and methanogenic Archaea) was measured with clade-specific degenerate hgcA quantitative PCR (qPCR) primer sets. The predominant microorganisms in unamended sediments consisted of Proteobacteria, Firmicutes, Bacteroidetes, and Actinobacteria Clade-specific qPCR identified hgcA+Deltaproteobacteria and Archaea in all sites but failed to detect hgcA+Firmicutes Cellobiose shifted the communities in all samples to ∼90% non-hgcAB-containing Firmicutes (mainly Bacillus spp. and Clostridium spp.). These results suggest that either expression of hgcAB is downregulated or, more likely given the lack of 16S rRNA gene presence after cellobiose incubation, Hg-methylating organisms are largely outcompeted by cellobiose degraders or degradation products of cellobiose. These results represent a step toward understanding and exploring simple methodologies for controlling MeHg production in the environment.IMPORTANCE Methylmercury (MeHg) is a neurotoxin produced by microorganisms that bioacummulates in the food web and poses a serious health risk to humans. Currently, the impact that organic substrate or electron acceptor availability has on the mercury (Hg)-methylating microorganisms is unclear. To study this, we set up microcosm experiments exposed to different organic substrates and electron acceptors and assayed for Hg methylation rates, for microbial community structure, and for distribution of Hg methylators. The sediment and groundwater was collected from East Fork Poplar Creek in Oak Ridge, TN. Amendment with cellobiose (a lignocellulosic degradation by-product) led to a drastic decrease in the Hg methylation rate compared to that in an unamended control, with an associated shift in the microbial community to mostly nonmethylating Firmicutes This, along with previous Hg-methylating microorganism identification methods, will be important for identifying strategies to control MeHg production and inform future remediation strategies.
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Gentès S, Taupiac J, Colin Y, André JM, Guyoneaud R. Bacterial periphytic communities related to mercury methylation within aquatic plant roots from a temperate freshwater lake (South-Western France). ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2017; 24:19223-19233. [PMID: 28664497 DOI: 10.1007/s11356-017-9597-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Accepted: 06/20/2017] [Indexed: 06/07/2023]
Abstract
Macrophyte floating roots are considered as hotspots for methylmercury (MeHg) production in aquatic ecosystems through microbial activity. Nevertheless, very little is known about periphyton bacterial communities and mercury (Hg) methylators in such ecological niches. The ability to methylate inorganic Hg is broadly distributed among prokaryotes; however, sulfate-reducers have been reported to be the most important MeHg producers in macrophyte floating roots. In the present work, the periphyton bacterial communities colonizing Ludwigia sp. floating roots were investigated through molecular methods. Among the 244 clones investigated, anaerobic microorganisms associated with the sulfur biogeochemical cycle were identified. Notably, members of the sulfur-oxidizing prokaryotes and the anoxygenic, purple non-sulfur bacteria (Rhodobacteraceae, Comamonadaceae, Rhodocyclaceae, Hyphomicrobiaceae) and the sulfate reducers (Desulfobacteraceae, Syntrophobacteraceae, and Desulfobulbaceae) were detected. In addition, 15 sulfate-reducing strains related to the Desulfovibrionaceae family were isolated and their Hg-methylation capacity was tested using a biosensor. The overall results confirmed that Hg methylation is a strain-specific process since the four strains identified as new Hg-methylators were closely related to non-methylating isolates. This study highlights the potential involvement of periphytic bacteria in Hg methylation when favorable environmental conditions are present in such ecological micro-niches.
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Affiliation(s)
- Sophie Gentès
- Equipe Environnement et Microbiologie, UMR IPREM5254 Université de Pau et des Pays de l'Adour, Bâtiment IBEAS, BP1153, 64013, Pau Cedex, France.
- Université de Bordeaux, EPOC, UMR CNRS 5805, 33120, Arcachon, France.
| | - Julie Taupiac
- Equipe Environnement et Microbiologie, UMR IPREM5254 Université de Pau et des Pays de l'Adour, Bâtiment IBEAS, BP1153, 64013, Pau Cedex, France
| | - Yannick Colin
- Equipe Environnement et Microbiologie, UMR IPREM5254 Université de Pau et des Pays de l'Adour, Bâtiment IBEAS, BP1153, 64013, Pau Cedex, France
| | - Jean-Marc André
- Equipe CIH, IMS UMR 5218, Ecole Nationale Supérieure de Cognitique, 109 Avenue Roul, 33400, Talence, France
| | - Rémy Guyoneaud
- Equipe Environnement et Microbiologie, UMR IPREM5254 Université de Pau et des Pays de l'Adour, Bâtiment IBEAS, BP1153, 64013, Pau Cedex, France
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46
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Paranjape AR, Hall BD. Recent advances in the study of mercury methylation in aquatic systems. Facets (Ott) 2017. [DOI: 10.1139/facets-2016-0027] [Citation(s) in RCA: 83] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
With increasing input of neurotoxic mercury to environments as a result of anthropogenic activity, it has become imperative to examine how mercury may enter biotic systems through its methylation to bioavailable forms in aquatic environments. Recent development of stable isotope-based methods in methylation studies has enabled a better understanding of the factors controlling methylation in aquatic systems. In addition, the identification and tracking of the hgcAB gene cluster, which is necessary for methylation, has broadened the range of known methylators and methylation-conducive environments. Study of abiotic factors in methylation with new molecular methods (the use of stable isotopes and genomic methods) has helped elucidate the confounding influences of many environmental factors, as these methods enable the examination of their direct effects instead of merely correlative observations. Such developments will be helpful in the finer characterization of mercury biogeochemical cycles, which will enable better predictions of the potential effects of climate change on mercury methylation in aquatic systems and, by extension, the threat this may pose to biota.
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Affiliation(s)
- Avnee R. Paranjape
- Department of Biology, University of Regina, 3737 Wascana Parkway, Regina, SK S4S 0A2, Canada
| | - Britt D. Hall
- Department of Biology, University of Regina, 3737 Wascana Parkway, Regina, SK S4S 0A2, Canada
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Zhang M, Huang F, Wang G, Liu X, Wen J, Zhang X, Huang Y, Xia Y. Geographic distribution of cadmium and its interaction with the microbial community in the Longjiang River: risk evaluation after a shocking pollution accident. Sci Rep 2017; 7:227. [PMID: 28331217 PMCID: PMC5427973 DOI: 10.1038/s41598-017-00280-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Accepted: 02/17/2017] [Indexed: 12/14/2022] Open
Abstract
A shocking Longjiang River cadmium pollution accident occurred in 2012, the effects of which on microbial communities remain unclear. Alkaline precipitation technology was applied for remediation, but concerns rose about the stability of this technology. To understand the geographic distribution of cadmium and its correlation with microbes, in this study, 39 water samples and 39 sludge samples from this river and 2 soil samples from the nearby farmland were collected for chemical and microbial analyses. The Cd concentrations of all water samples were lower than 0.005 mg/L and reached the quality standards for Chinese surface water. A ranking of sludge samples based on Cd contents showed sewage outfall > dosing sites > farmland, all of which were higher than the quality standard for soil. Alkaline precipitation technology was effective for Cd precipitation. Cd was unstable; it was constantly dissolving and being released from the sludge. The Cd content of each phase was mainly influenced by the total Cd content. Over 40,000 effective sequences were detected in each sample, and a total of 59,833 OTUs and 1,273 genera were found using Illumina MiSeq sequencing. Two phyla and 39 genera were notably positively correlated with the Cd distribution, while the cases of 10 phyla and 6 genera were the opposite.
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Affiliation(s)
- MingJiang Zhang
- National Engineering Laboratory of Biohydrometallurgy, General Research Institute for Nonferrous Metals, No. 2 Xinjiekouwai Street, Beijing, 100088, China
| | - FuKe Huang
- Institute of HeChi Scientific-Technical Information, No. 385 West Ring Road of HeChi City, GuangXi Zhuang Autonomous Region, 547000, China
| | - GuangYuan Wang
- National Engineering Laboratory of Biohydrometallurgy, General Research Institute for Nonferrous Metals, No. 2 Xinjiekouwai Street, Beijing, 100088, China
| | - XingYu Liu
- National Engineering Laboratory of Biohydrometallurgy, General Research Institute for Nonferrous Metals, No. 2 Xinjiekouwai Street, Beijing, 100088, China.
| | - JianKang Wen
- National Engineering Laboratory of Biohydrometallurgy, General Research Institute for Nonferrous Metals, No. 2 Xinjiekouwai Street, Beijing, 100088, China
| | - XiaoSheng Zhang
- Institute of HeChi Scientific-Technical Information, No. 385 West Ring Road of HeChi City, GuangXi Zhuang Autonomous Region, 547000, China
| | - YaoSi Huang
- Institute of HeChi Scientific-Technical Information, No. 385 West Ring Road of HeChi City, GuangXi Zhuang Autonomous Region, 547000, China
| | - Yu Xia
- National Engineering Laboratory of Biohydrometallurgy, General Research Institute for Nonferrous Metals, No. 2 Xinjiekouwai Street, Beijing, 100088, China
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48
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Draft Genome Sequence of Desulfovibrio BerOc1, a Mercury-Methylating Strain. GENOME ANNOUNCEMENTS 2017; 5:5/3/e01483-16. [PMID: 28104657 PMCID: PMC5255934 DOI: 10.1128/genomea.01483-16] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Desulfovibrio BerOc1 is a sulfate-reducing bacterium isolated from the Berre lagoon (French Mediterranean coast). BerOc1 is able to methylate and demethylate mercury. The genome size is 4,081,579 bp assembled into five contigs. We identified the hgcA and hgcB genes involved in mercury methylation, but not those responsible for mercury demethylation.
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49
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Schwartz GE, Redfern LK, Ikuma K, Gunsch CK, Ruhl LS, Vengosh A, Hsu-Kim H. Impacts of coal ash on methylmercury production and the methylating microbial community in anaerobic sediment slurries. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2016; 18:1427-1439. [PMID: 27722355 DOI: 10.1039/c6em00458j] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Mercury (Hg) associated with coal ash is an environmental concern, particularly if the release of coal ash to the environment is associated with the conversion of inorganic Hg to methylmercury (MeHg), a bioaccumulative form of Hg that is produced by anaerobic microorganisms. In this study, sediment slurry microcosm experiments were performed to understand how spilled coal ash might influence MeHg production in anaerobic sediments of an aquatic ecosystem. Two coal ash types were used: (1) a weathered coal ash; and (2) a freshly collected, unweathered fly ash that was relatively enriched in sulfate and Hg compared to the weathered ash. These ash samples were added to anaerobic sediment slurries constructed with a relatively pristine sediment (containing 0.03 mg kg-1 Hg) and a Hg-contaminated sediment (containing 0.29 mg kg-1 Hg). The results of these experiments showed negligible net production of MeHg in microcosms with no ash and in microcosms amended with the low sulfate/low Hg ash. In contrast, slurry microcosms amended with high sulfate/high Hg ash showed increases in total MeHg content that was 2 to 3 times greater than control microcosms without ash (p < 0.001). 16S amplicon sequencing of microbial communities in the slurries indicated that the coal ash addition generally increased the relative abundance of the methylating microbial community, including sulfate-reducing bacteria and iron-reducing bacteria species that are known to be efficient methylators of Hg. The stimulation of these microorganisms was likely caused by the release of substrates (sulfate and Fe) originating from the ash. Overall, the results highlight the need to incorporate both environmental parameters and coal ash characteristics into risk assessments that guide coal ash management and disposal.
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Affiliation(s)
- Grace E Schwartz
- Duke University, Department of Civil & Environmental Engineering, 121 Hudson Hall, Durham, North Carolina 27708, USA.
| | - Lauren K Redfern
- Duke University, Department of Civil & Environmental Engineering, 121 Hudson Hall, Durham, North Carolina 27708, USA.
| | - Kaoru Ikuma
- Iowa State University, Department of Civil, Construction, and Environmental Engineering, Ames, Iowa 50011, USA
| | - Claudia K Gunsch
- Duke University, Department of Civil & Environmental Engineering, 121 Hudson Hall, Durham, North Carolina 27708, USA.
| | - Laura S Ruhl
- University of Arkansas-Little Rock, Department of Earth Sciences, Little Rock, Arkansas 72204, USA
| | - Avner Vengosh
- Duke University, Division of Earth and Ocean Sciences, Nicholas School of the Environment, Durham, North Carolina, USA
| | - Heileen Hsu-Kim
- Duke University, Department of Civil & Environmental Engineering, 121 Hudson Hall, Durham, North Carolina 27708, USA.
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Bravo AG, Loizeau JL, Dranguet P, Makri S, Björn E, Ungureanu VG, Slaveykova VI, Cosio C. Persistent Hg contamination and occurrence of Hg-methylating transcript (hgcA) downstream of a chlor-alkali plant in the Olt River (Romania). ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2016; 23:10529-10541. [PMID: 26662302 DOI: 10.1007/s11356-015-5906-4] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Accepted: 11/30/2015] [Indexed: 05/16/2023]
Abstract
Chlor-alkali plants using mercury (Hg) cell technology are acute point sources of Hg pollution in the aquatic environment. While there have been recent efforts to reduce the use of Hg cells, some of the emitted Hg can be transformed to neurotoxic methylmercury (MeHg). Here, we aimed (i) to study the dispersion of Hg in four reservoirs located downstream of a chlor-alkali plant along the Olt River (Romania) and (ii) to track the activity of bacterial functional genes involved in Hg methylation. Total Hg (THg) concentrations in water and sediments decreased successively from the initial reservoir to downstream reservoirs. Suspended fine size particles and seston appeared to be responsible for the transport of THg into downstream reservoirs, while macrophytes reflected the local bioavailability of Hg. The concentration and proportion of MeHg were correlated with THg, but were not correlated with bacterial activity in sediments, while the abundance of hgcA transcript correlated with organic matter and Cl(-) concentration, indicating the importance of Hg bioavailability in sediments for Hg methylation. Our data clearly highlights the importance of considering Hg contamination as a legacy pollutant since there is a high risk of continued Hg accumulation in food webs long after Hg-cell phase out.
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Affiliation(s)
- Andrea G Bravo
- Limnology/Department of Ecology and Genetics, Uppsala University, Norbyvägen 18D, 75236, Uppsala, Sweden
| | - Jean-Luc Loizeau
- Institute F.-A. Forel, Earth and Environmental Sciences, University of Geneva, 10, Route de Suisse, 1290, Versoix, Switzerland
| | - Perrine Dranguet
- Institute F.-A. Forel, Earth and Environmental Sciences, University of Geneva, 10, Route de Suisse, 1290, Versoix, Switzerland
| | - Stamatina Makri
- Institute F.-A. Forel, Earth and Environmental Sciences, University of Geneva, 10, Route de Suisse, 1290, Versoix, Switzerland
| | - Erik Björn
- Department of Chemistry, Umeå University, SE-90187, Umeå, Sweden
| | - Viorel Gh Ungureanu
- Faculty of Geology and Geophysics, University of Bucharest, Bucharest, Romania
- GeoEcoMar, National Research and Development Institute for Marine Geology and Geoecology, Bucharest, Romania
| | - Vera I Slaveykova
- Institute F.-A. Forel, Earth and Environmental Sciences, University of Geneva, 10, Route de Suisse, 1290, Versoix, Switzerland
| | - Claudia Cosio
- Institute F.-A. Forel, Earth and Environmental Sciences, University of Geneva, 10, Route de Suisse, 1290, Versoix, Switzerland.
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