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Wang YL, Ikuma K, Brown AMV, Deonarine A. Global survey of hgcA-carrying genomes in marine and freshwater sediments: Insights into mercury methylation processes. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2024; 352:124117. [PMID: 38714231 DOI: 10.1016/j.envpol.2024.124117] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2024] [Revised: 04/11/2024] [Accepted: 05/05/2024] [Indexed: 05/09/2024]
Abstract
Mercury (Hg) methylation is a microbially mediated process that produces methylmercury (MeHg), a bioaccumulative neurotoxin. A highly conserved gene pair, hgcAB, is required for Hg methylation, which provides a basis for identifying Hg methylators and evaluating their genomic composition. In this study, we conducted a large-scale omics analysis in which 281 metagenomic freshwater and marine sediment samples from 46 geographic locations across the globe were queried. Specific objectives were to examine the prevalence of Hg methylators, to identify horizontal gene transfer (HGT) events involving hgcAB within Hg methylator communities, and to identify associations between hgcAB and microbial biochemical functions/genes. Hg methylators from the phyla Desulfobacterota and Bacteroidota were dominant in both freshwater and marine sediments while Firmicutes and methanogens belonging to Euryarchaeota were identified only in freshwater sediments. Novel Hg methylators were found in the Phycisphaerae and Planctomycetia classes within the phylum Planctomycetota, including potential hgcA-carrying anammox metagenome-assembled genomes (MAGs) from Candidatus Brocadiia. HGT of hgcA and hgcB were identified in both freshwater and marine methylator communities. Spearman's correlation analysis of methylator genomes suggested that in addition to sulfide, thiosulfate, sulfite, and ammonia may be important parameters for Hg methylation processes in sediments. Overall, our results indicated that the biochemical drivers of Hg methylation vary between marine and freshwater sites, lending insight into the influence of environmental perturbances, such as a changing climate, on Hg methylation processes.
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Affiliation(s)
- Yong-Li Wang
- Department of Civil, Environmental & Construction Engineering, Texas Tech University, Lubbock, TX, United States
| | - Kaoru Ikuma
- Department of Civil, Construction and Environmental Engineering, Iowa State University, Ames, IA, United States
| | - Amanda M V Brown
- Department of Biological Sciences, Texas Tech University, Lubbock, TX, United States
| | - Amrika Deonarine
- Department of Civil, Environmental & Construction Engineering, Texas Tech University, Lubbock, TX, United States.
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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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Hu S, Zhang Y, Meng H, Yang Y, Chen G, Wang Q, Cheng K, Guo C, Li X, Liu T. Transformation and migration of Hg in a polluted alkaline paddy soil during flooding and drainage processes. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2024; 345:123471. [PMID: 38336140 DOI: 10.1016/j.envpol.2024.123471] [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: 11/08/2023] [Revised: 01/14/2024] [Accepted: 01/29/2024] [Indexed: 02/12/2024]
Abstract
Mercury (Hg) contamination in paddy soils poses a health risk to rice consumers and the environmental behavior of Hg determines its toxicity. Thus, the variations of Hg speciation are worthy of exploring. In this study, microcosm and pot experiments were conducted to elucidate Hg transformation, methylation, bioaccumulation, and risk coupled with biogeochemical cycling of key elements in a Hg-polluted alkaline paddy soil. In microcosm and pot experiments, organic- and sulfide-bound and residual Hg accounted for more than 98% of total Hg, and total contents of dissolved, exchangeable, specifically adsorbed, and fulvic acid-bound Hg were less than 2% of total Hg, indicating a low mobility and environmental risk of Hg. The decrease of pH aroused from Fe(III), SO42-, and NO3- reduction promoted Hg mobility, whereas the increase of pH caused by Fe(II), S2-, and NH4+ oxidation reduced available Hg contents. Moreover, Fe-bearing minerals reduction and organic matter consumption promoted Hg mobility, whereas the produced HgS and Fe(II) oxidation increased Hg stability. During flooding, a fraction of inorganic Hg (IHg) could be transported into methylmercury (MeHg), and during drainage, MeHg would be converted back into IHg. After planting rice in an alkaline paddy soil, available Hg was below 0.3 mg kg-1. During rice growth, a portion of available Hg transport from paddy soil to rice, promoting Hg accumulation in rice grains. After rice ripening, IHg levels in rice tissues followed the trend: root > leaf > stem > grain, and IHg content in rice grain exceed 0.02 mg kg-1, but MeHg content in rice grain meets daily intake limit (37.45 μg kg-1). These results provide a basis for assessing the environmental risks and developing remediation strategies for Hg-contaminated redox-changing paddy fields as well as guaranteeing the safe production of rice grains.
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Affiliation(s)
- Shiwen Hu
- National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-Environ. Pollut. Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, China
| | - Yufan Zhang
- National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-Environ. Pollut. Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, China
| | - Hanbing Meng
- National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-Environ. Pollut. Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, China
| | - Yang Yang
- National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-Environ. Pollut. Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, China
| | - Guojun Chen
- National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-Environ. Pollut. Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, China
| | - Qi Wang
- National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-Environ. Pollut. Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, China
| | - Kuan Cheng
- National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-Environ. Pollut. Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, China
| | - Chao Guo
- National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-Environ. Pollut. Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, China
| | - Xiaomin Li
- SCNU Environmental Research Institute, Guangdong Provincial Key Laboratory of Chemical Pollution and Environmental Safety & MOE Key Laboratory of Theoretical Chemistry of Environment, South China Normal University, Guangzhou, 510006, China
| | - Tongxu Liu
- National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-Environ. Pollut. Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, China.
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