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Eklöf K, Bishop K, Bertilsson S, Björn E, Buck M, Skyllberg U, Osman OA, Kronberg RM, Bravo AG. Formation of mercury methylation hotspots as a consequence of forestry operations. THE SCIENCE OF THE TOTAL ENVIRONMENT 2018; 613-614:1069-1078. [PMID: 28950669 DOI: 10.1016/j.scitotenv.2017.09.151] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Revised: 09/13/2017] [Accepted: 09/15/2017] [Indexed: 05/16/2023]
Abstract
Earlier studies have shown that boreal forest logging can increase the concentration and export of methylmercury (MeHg) in stream runoff. Here we test whether forestry operations create soil environments of high MeHg net formation associated with distinct microbial communities. Furthermore, we test the hypothesis that Hg methylation hotspots are more prone to form after stump harvest than stem-only harvest, because of more severe soil compaction and soil disturbance. Concentrations of MeHg, percent MeHg of total Hg (THg), and bacterial community composition were determined at 200 soil sampling positions distributed across eight catchments. Each catchment was either stem-only harvested (n=3), stem- and stump-harvested (n=2) or left undisturbed (n=3). In support of our hypothesis, higher MeHg to THg ratios was observed in one of the stump-harvested catchments. While the effects of natural variation could not be ruled out, we noted that most of the highest % MeHg was observed in water-filled cavities created by stump removal or driving damage. This catchment also featured the highest bacterial diversity and highest relative abundance of bacterial families known to include Hg methylators. We propose that water-logged and disturbed soil environments associated with stump harvest can favor methylating microorganisms, which also enhance MeHg formation.
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Affiliation(s)
- Karin Eklöf
- Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, SE-75007 Uppsala, Sweden.
| | - Kevin Bishop
- Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, SE-75007 Uppsala, Sweden
| | - Stefan Bertilsson
- Department of Ecology and Genetics, Limnology and Science for Life Laboratory, Uppsala University, SE-75236 Uppsala, Sweden
| | - Erik Björn
- Department of Chemistry, Umeå University, SE-901 87 Umeå, Sweden
| | - Moritz Buck
- Department of Chemistry, Umeå University, SE-901 87 Umeå, Sweden; National Bioinformatics Infrastructure Sweden, Uppsala SE-75236, Sweden
| | - Ulf Skyllberg
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, SE-901 83 Umeå, Sweden
| | - Omneya A Osman
- Department of Ecology and Genetics, Limnology and Science for Life Laboratory, Uppsala University, SE-75236 Uppsala, Sweden
| | - Rose-Marie Kronberg
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, SE-901 83 Umeå, Sweden
| | - Andrea G Bravo
- Department of Ecology and Genetics, Limnology and Science for Life Laboratory, Uppsala University, SE-75236 Uppsala, Sweden
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202
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Mechirackal Balan B, Shini S, Krishnan KP, Mohan M. Mercury tolerance and biosorption in bacteria isolated from Ny-Ålesund, Svalbard, Arctic. J Basic Microbiol 2018; 58:286-295. [DOI: 10.1002/jobm.201700496] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2017] [Revised: 11/23/2017] [Accepted: 01/12/2018] [Indexed: 01/01/2023]
Affiliation(s)
| | - Sruthy Shini
- School of Environmental Sciences; Mahatma Gandhi University; Kottayam Kerala India
| | | | - Mahesh Mohan
- School of Environmental Sciences; Mahatma Gandhi University; Kottayam Kerala India
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203
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Willis CE, Kirk JL, St Louis VL, Lehnherr I, Ariya PA, Rangel-Alvarado RB. Sources of Methylmercury to Snowpacks of the Alberta Oil Sands Region: A Study of In Situ Methylation and Particulates. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2018; 52:531-540. [PMID: 29198105 DOI: 10.1021/acs.est.7b04096] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Snowpacks in the Alberta Oil Sands Region (AOSR) of Canada contain elevated loadings of methylmercury (MeHg; a neurotoxin that biomagnifies through foodwebs) due to oil sands related activities. At sites ranging from 0 to 134 km from the major AOSR upgrading facilities, we examined sources of MeHg by quantifying potential rates of MeHg production in snowpacks and melted snow using mercury stable isotope tracer experiments, as well as quantifying concentrations of MeHg on particles in snowpacks (pMeHg). At four sites, methylation rate constants were low in snowpacks (km = 0.001-0.004 d-1) and nondetectable in melted snow, except at one site (km = 0.0007 d-1). The ratio of methylation to demethylation varied between 0.3 and 1.5, suggesting that the two processes are in balance and that in situ production is unlikely an important net source of MeHg to AOSR snowpacks. pMeHg concentrations increased linearly with distance from the upgraders (R2 = 0.71, p < 0.0001); however, snowpack total particle and pMeHg loadings decreased exponentially over this same distance (R2 = 0.49, p = 0.0002; R2 = 0.56, p < 0.0001). Thus, at near-field sites, total MeHg loadings in snowpacks were high due to high particle loadings, even though particles originating from industrial activities were not MeHg rich compared to those at remote sites. More research is required to identify the industrial sources of snowpack particles in the AOSR.
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Affiliation(s)
- Chelsea E Willis
- Department of Biological Sciences, University of Alberta , Edmonton, Alberta T6G 2E9, Canada
| | - Jane L Kirk
- Aquatic Contaminants Research Division , Environment and Climate Change Canada, Burlington, Ontario L7S 1A1, Canada
| | - Vincent L St Louis
- Department of Biological Sciences, University of Alberta , Edmonton, Alberta T6G 2E9, Canada
| | - Igor Lehnherr
- Department of Geography, University of Toronto Mississauga , Mississauga, Ontario L5L 1C6, Canada
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204
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LaVoie SP, Summers AO. Transcriptional responses of Escherichia coli during recovery from inorganic or organic mercury exposure. BMC Genomics 2018; 19:52. [PMID: 29338696 PMCID: PMC5769350 DOI: 10.1186/s12864-017-4413-z] [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] [Received: 11/02/2017] [Accepted: 12/22/2017] [Indexed: 12/22/2022] Open
Abstract
Background The protean chemical properties of mercury have long made it attractive for diverse applications, but its toxicity requires great care in its use, disposal, and recycling. Mercury occurs in multiple chemical forms, and the molecular basis for the distinct toxicity of its various forms is only partly understood. Global transcriptomics applied over time can reveal how a cell recognizes a toxicant and what cellular subsystems it marshals to repair and recover from the damage. The longitudinal effects on the transcriptome of exponential phase E. coli were compared during sub-acute exposure to mercuric chloride (HgCl2) or to phenylmercuric acetate (PMA) using RNA-Seq. Results Differential gene expression revealed common and distinct responses to the mercurials throughout recovery. Cultures exhibited growth stasis immediately after each mercurial exposure but returned to normal growth more quickly after PMA exposure than after HgCl2 exposure. Correspondingly, PMA rapidly elicited up-regulation of a large number of genes which continued for 30 min, whereas fewer genes were up-regulated early after HgCl2 exposure only some of which overlapped with PMA up-regulated genes. By 60 min gene expression in PMA-exposed cells was almost indistinguishable from unexposed cells, but HgCl2 exposed cells still had many differentially expressed genes. Relative expression of energy production and most metabolite uptake pathways declined with both compounds, but nearly all stress response systems were up-regulated by one or the other mercurial during recovery. Conclusions Sub-acute exposure influenced expression of ~45% of all genes with many distinct responses for each compound, reflecting differential biochemical damage by each mercurial and the corresponding resources available for repair. This study is the first global, high-resolution view of the transcriptional responses to any common toxicant in a prokaryotic model system from exposure to recovery of active growth. The responses provoked by these two mercurials in this model bacterium also provide insights about how higher organisms may respond to these ubiquitous metal toxicants. Electronic supplementary material The online version of this article (10.1186/s12864-017-4413-z) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Stephen P LaVoie
- Department of Microbiology, University of Georgia, Athens, GA, 30602, USA.
| | - Anne O Summers
- Department of Microbiology, University of Georgia, Athens, GA, 30602, USA.
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205
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Low-Molecular-Weight Thiols and Thioredoxins Are Important Players in Hg(II) Resistance in Thermus thermophilus HB27. Appl Environ Microbiol 2018; 84:AEM.01931-17. [PMID: 29150497 DOI: 10.1128/aem.01931-17] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2017] [Accepted: 10/24/2017] [Indexed: 12/31/2022] Open
Abstract
Mercury (Hg), one of the most toxic and widely distributed heavy metals, has a high affinity for thiol groups. Thiol groups reduce and sequester Hg. Therefore, low-molecular-weight (LMW) and protein thiols may be important cell components used in Hg resistance. To date, the role of low-molecular-weight thiols in Hg detoxification remains understudied. The mercury resistance (mer) operon of Thermus thermophilus suggests an evolutionary link between Hg(II) resistance and low-molecular-weight thiol metabolism. The mer operon encodes an enzyme involved in methionine biosynthesis, Oah. Challenge with Hg(II) resulted in increased expression of genes involved in the biosynthesis of multiple low-molecular-weight thiols (cysteine, homocysteine, and bacillithiol), as well as the thioredoxin system. Phenotypic analysis of gene replacement mutants indicated that Oah contributes to Hg resistance under sulfur-limiting conditions, and strains lacking bacillithiol and/or thioredoxins are more sensitive to Hg(II) than the wild type. Growth in the presence of either a thiol-oxidizing agent or a thiol-alkylating agent increased sensitivity to Hg(II). Furthermore, exposure to 3 μM Hg(II) consumed all intracellular reduced bacillithiol and cysteine. Database searches indicate that oah2 is present in all Thermus sp. mer operons. The presence of a thiol-related gene was also detected in some alphaproteobacterial mer operons, in which a glutathione reductase gene was present, supporting the role of thiols in Hg(II) detoxification. These results have led to a working model in which LMW thiols act as Hg(II)-buffering agents while Hg is reduced by MerA.IMPORTANCE The survival of microorganisms in the presence of toxic metals is central to life's sustainability. The affinity of thiol groups for toxic heavy metals drives microbe-metal interactions and modulates metal toxicity. Mercury detoxification (mer) genes likely originated early in microbial evolution in geothermal environments. Little is known about how mer systems interact with cellular thiol systems. Thermus spp. possess a simple mer operon in which a low-molecular-weight thiol biosynthesis gene is present, along with merR and merA In this study, we present experimental evidence for the role of thiol systems in mercury resistance. Our data suggest that, in T. thermophilus, thiolated compounds may function side by side with mer genes to detoxify mercury. Thus, thiol systems function in consort with mer-mediated resistance to mercury, suggesting exciting new questions for future research.
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206
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Solioz M. Copper Homeostasis in Gram-Positive Bacteria. SPRINGERBRIEFS IN MOLECULAR SCIENCE 2018. [DOI: 10.1007/978-3-319-94439-5_3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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207
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Guo G, Yumvihoze E, Poulain AJ, Man Chan H. Monomethylmercury degradation by the human gut microbiota is stimulated by protein amendments. J Toxicol Sci 2018; 43:717-725. [DOI: 10.2131/jts.43.717] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Affiliation(s)
- Galen Guo
- Department of Biology, Faculty of Science, University of Ottawa, Ottawa, Canada K1N 9B4
| | - Emmanuel Yumvihoze
- Department of Biology, Faculty of Science, University of Ottawa, Ottawa, Canada K1N 9B4
| | - Alexandre J. Poulain
- Department of Biology, Faculty of Science, University of Ottawa, Ottawa, Canada K1N 9B4
| | - Hing Man Chan
- Department of Biology, Faculty of Science, University of Ottawa, Ottawa, Canada K1N 9B4
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208
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da Penha Rhodes V, de Lena JC, Santolin CVA, da Silva Pinto T, Mendes LA, Windmöller CC. Speciation and quantification of Hg in sediments contaminated by artisanal gold mining in the Gualaxo do Norte River, Minas Gerais, SE, Brazil. ENVIRONMENTAL MONITORING AND ASSESSMENT 2017; 190:49. [PMID: 29285676 DOI: 10.1007/s10661-017-6394-4] [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: 06/13/2017] [Accepted: 12/05/2017] [Indexed: 06/07/2023]
Abstract
The Iron Quadrangle in SE Brazil was, in the eighteenth century, one of the most important Au producing regions of Brazil. In this region, gold is produced, even today, by artisanal methods that use Hg to increase the extraction efficiency with no control of Hg release to water systems and the atmosphere. In this context, the Gualaxo do Norte River is of particular interest; its springs are located in the Doce River basin, an important Brazilian basin that supplies water for 3.5 million people. The main goal of this work was to quantify and speciate the Hg in the sediments of the Gualaxo do Norte River using a direct mercury analyzer and gas chromatography-pyrolysis-atomic fluorescence detection system. Statistical analyses consisted of principal component analysis, aiming to assess interactions among elements and species and to group the variables in factors affecting the properties of sediment. The results show that total Hg (THg) and methylmercury (CH3Hg+) concentrations in samples ranged from 209 to 1207 μg kg-1 and from 0.07 to 1.00 μg kg-1, respectively (methylation percentages from 0.01 to 0.27%). Thermal desorption analysis showed that mercury is mainly present in the oxidized form, and correlation analyses pointed to a relationship between THg and MnO, indicating that manganese can oxidize and/or adsorb Hg. Together, MO and CH3Hg+ are important parameters in the third principal component, indicating the influence of OM on the methylation process. This first investigation on Hg methylation in this small-scale gold mining area points to the possibility of Hg bioaccumulation and to the need of better understanding the biogeochemical cycle of Hg in this area. Samples were collected in 2012, prior to the 2015 Fundão Dam disaster. The results are also a record of the characteristics of the sediment prior to that event.
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Affiliation(s)
- Valdilene da Penha Rhodes
- Departamento de Geologia, Escola de Minas, Campus Morro do Cruzeiro, Universidade Federal de Ouro Preto, Ouro Preto, MG, 35400-000, Brazil
| | - Jorge Carvalho de Lena
- Departamento de Geologia, Escola de Minas, Campus Morro do Cruzeiro, Universidade Federal de Ouro Preto, Ouro Preto, MG, 35400-000, Brazil.
| | - Camila Vidal Alves Santolin
- Departamento de Química, Instituto de Ciências Exatas, Universidade Federal de Minas Gerais, Av. Antônio Carlos, 6627, Belo Horizonte, MG, 31270-901, Brazil
| | - Thais da Silva Pinto
- Departamento de Química, Instituto de Ciências Exatas, Universidade Federal de Minas Gerais, Av. Antônio Carlos, 6627, Belo Horizonte, MG, 31270-901, Brazil
| | - Louise Aparecida Mendes
- Departamento de Química, Instituto de Ciências Exatas, Universidade Federal de Minas Gerais, Av. Antônio Carlos, 6627, Belo Horizonte, MG, 31270-901, Brazil
| | - Cláudia Carvalhinho Windmöller
- Departamento de Química, Instituto de Ciências Exatas, Universidade Federal de Minas Gerais, Av. Antônio Carlos, 6627, Belo Horizonte, MG, 31270-901, Brazil
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209
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Hellal J, Burnol A, Locatelli A, Battaglia-Brunet F. Experimental Column Setup for Studying Anaerobic Biogeochemical Interactions Between Iron (Oxy)Hydroxides, Trace Elements, and Bacteria. J Vis Exp 2017. [PMID: 29286400 DOI: 10.3791/56240] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Fate and speciation of trace elements (TEs), such as arsenic (As) and mercury (Hg), in aquifers are closely related to physio-chemical conditions, such as redox potential (Eh) and pH, but also to microbial activities that can play a direct or indirect role on speciation and/or mobility. Indeed, some bacteria can directly oxidize As(III) to As(V) or reduce As(V) to As(III). Likewise, bacteria are strongly involved in Hg cycling, either through its methylation, forming the neurotoxin monomethyl mercury, or through its reduction to elemental Hg°. The fates of both As and Hg are also strongly linked to soil or aquifer composition; indeed, As and Hg can bind to organic compounds or (oxy)hydroxides, which will influence their mobility. In turn, bacterial activities such as iron (oxy)hydroxide reduction or organic matter mineralization can indirectly influence As and Hg sequestration. The presence of sulfate/sulfide can also strongly impact these particular elements through the formation of complexes such as thio-arsenates with As or metacinnabar with Hg. Consequently, many important questions have been raised on the fate and speciation of As and Hg in the environment and how to limit their toxicity. However, due to their reactivity towards aquifer components, it is difficult to clearly dissociate the biogeochemical processes that occur and their different impacts on the fate of these TE. To do so, we developed an original, experimental, column setup that mimics an aquifer with As- or Hg-iron-oxide rich areas versus iron depleted areas, enabling a better understanding of TE biogeochemistry in anoxic conditions. The following protocol gives step by step instructions for the column set-up either for As or Hg, as well as an example with As under iron and sulfate reducing conditions.
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Affiliation(s)
| | | | - Aude Locatelli
- Environmental Biogeochemistry and Water Quality Unit, BRGM; Egg Safety & Quality Research
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210
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Ojuederie OB, Babalola OO. Microbial and Plant-Assisted Bioremediation of Heavy Metal Polluted Environments: A Review. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2017; 14:ijerph14121504. [PMID: 29207531 PMCID: PMC5750922 DOI: 10.3390/ijerph14121504] [Citation(s) in RCA: 303] [Impact Index Per Article: 43.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Revised: 11/27/2017] [Accepted: 11/30/2017] [Indexed: 11/26/2022]
Abstract
Environmental pollution from hazardous waste materials, organic pollutants and heavy metals, has adversely affected the natural ecosystem to the detriment of man. These pollutants arise from anthropogenic sources as well as natural disasters such as hurricanes and volcanic eruptions. Toxic metals could accumulate in agricultural soils and get into the food chain, thereby becoming a major threat to food security. Conventional and physical methods are expensive and not effective in areas with low metal toxicity. Bioremediation is therefore an eco-friendly and efficient method of reclaiming environments contaminated with heavy metals by making use of the inherent biological mechanisms of microorganisms and plants to eradicate hazardous contaminants. This review discusses the toxic effects of heavy metal pollution and the mechanisms used by microbes and plants for environmental remediation. It also emphasized the importance of modern biotechnological techniques and approaches in improving the ability of microbial enzymes to effectively degrade heavy metals at a faster rate, highlighting recent advances in microbial bioremediation and phytoremediation for the removal of heavy metals from the environment as well as future prospects and limitations. However, strict adherence to biosafety regulations must be followed in the use of biotechnological methods to ensure safety of the environment.
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Affiliation(s)
- Omena Bernard Ojuederie
- Food Security and Safety Niche Area, Faculty of Natural and Agricultural Sciences, North-West University, Private Mail Bag X2046, Mmabatho 2735, South Africa.
| | - Olubukola Oluranti Babalola
- Food Security and Safety Niche Area, Faculty of Natural and Agricultural Sciences, North-West University, Private Mail Bag X2046, Mmabatho 2735, South Africa.
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211
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Sequestosome1/p62 protects mouse embryonic fibroblasts against low-dose methylercury-induced cytotoxicity and is involved in clearance of ubiquitinated proteins. Sci Rep 2017; 7:16735. [PMID: 29196648 PMCID: PMC5711938 DOI: 10.1038/s41598-017-17112-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Accepted: 11/22/2017] [Indexed: 01/07/2023] Open
Abstract
Methylmercury (MeHg) is a widely distributed environmental pollutant that causes a series of cytotoxic effects. However, molecular mechanisms underlying MeHg toxicity are not fully understood. Here, we report that sequestosome1/p62 protects mouse embryonic fibroblasts (MEFs) against low-dose MeHg cytotoxicity via clearance of MeHg-induced ubiquitinated proteins. p62 mRNA and protein expression in MEFs were temporally induced by MeHg exposure p62-deficient MEFs exhibited higher sensitivity to MeHg exposure compared to their wild-type (WT) counterparts. An earlier and higher level of accumulation of ubiquitinated proteins was detected in p62-deficient cells compared with WT MEFs. Confocal microscopy revealed that p62 and ubiquitinated proteins co-localized in the perinuclear region of MEFs following MeHg treatment. Further analysis of MEFs revealed that ubiquitinated proteins co-localized with LC3-positive puncta upon co-treatment with MeHg and chloroquine, an autophagy inhibitor. In contrast, there was minimal co-localization in p62-deficient MEFs. The present study, for the first time, examined the expression and distribution of p62 and ubiquitinated proteins in cells exposed to low-dose MeHg. Our findings suggest that p62 is crucial for cytoprotection against MeHg-induced toxicity and is required for MeHg-induced ubiquitinated protein clearance.
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212
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Sone Y, Uraguchi S, Takanezawa Y, Nakamura R, Pan-Hou H, Kiyono M. Cysteine and histidine residues are involved in Escherichia coli Tn 21 MerE methylmercury transport. FEBS Open Bio 2017; 7:1994-1999. [PMID: 29226085 PMCID: PMC5715351 DOI: 10.1002/2211-5463.12341] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Revised: 10/05/2017] [Accepted: 10/24/2017] [Indexed: 11/29/2022] Open
Abstract
Bacterial resistance to mercury compounds (mercurials) is mediated by proteins encoded by mercury resistance (mer) operons. Six merE variants with site‐directed mutations were constructed to investigate the roles of the cysteine and histidine residues in MerE protein during mercurial transport. By comparison of mercurial uptake by the cell with intact and/or variant MerE, we showed that the cysteine pair in the first transmembrane domain was critical for the transport of both Hg(II) and CH3Hg(I). Also, the histidine residue located near to the cysteine pair was critical for Hg(II) transport, whereas the histidine residue located on the periplasmic side was critical for CH3Hg(I) transport. Thus, enhanced mercurial uptake mediated by MerE may be a promising strategy for the design of new biomass for use in the bioremediation of mercurials in the environment.
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Affiliation(s)
- Yuka Sone
- Department of Public Health School of Pharmacy Kitasato University Tokyo Japan
| | - Shimpei Uraguchi
- Department of Public Health School of Pharmacy Kitasato University Tokyo Japan
| | - Yasukazu Takanezawa
- Department of Public Health School of Pharmacy Kitasato University Tokyo Japan
| | - Ryosuke Nakamura
- Department of Public Health School of Pharmacy Kitasato University Tokyo Japan
| | | | - Masako Kiyono
- Department of Public Health School of Pharmacy Kitasato University Tokyo Japan
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213
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Sellés Vidal L, Kelly CL, Mordaka PM, Heap JT. Review of NAD(P)H-dependent oxidoreductases: Properties, engineering and application. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2017; 1866:327-347. [PMID: 29129662 DOI: 10.1016/j.bbapap.2017.11.005] [Citation(s) in RCA: 164] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 08/16/2017] [Revised: 10/27/2017] [Accepted: 11/08/2017] [Indexed: 11/27/2022]
Abstract
NAD(P)H-dependent oxidoreductases catalyze the reduction or oxidation of a substrate coupled to the oxidation or reduction, respectively, of a nicotinamide adenine dinucleotide cofactor NAD(P)H or NAD(P)+. NAD(P)H-dependent oxidoreductases catalyze a large variety of reactions and play a pivotal role in many central metabolic pathways. Due to the high activity, regiospecificity and stereospecificity with which they catalyze redox reactions, they have been used as key components in a wide range of applications, including substrate utilization, the synthesis of chemicals, biodegradation and detoxification. There is great interest in tailoring NAD(P)H-dependent oxidoreductases to make them more suitable for particular applications. Here, we review the main properties and classes of NAD(P)H-dependent oxidoreductases, the types of reactions they catalyze, some of the main protein engineering techniques used to modify their properties and some interesting examples of their modification and application.
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Affiliation(s)
- Lara Sellés Vidal
- Centre for Synthetic Biology and Innovation, Department of Life Sciences, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom
| | - Ciarán L Kelly
- Centre for Synthetic Biology and Innovation, Department of Life Sciences, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom
| | - Paweł M Mordaka
- Centre for Synthetic Biology and Innovation, Department of Life Sciences, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom
| | - John T Heap
- Centre for Synthetic Biology and Innovation, Department of Life Sciences, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom.
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214
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Hsueh YH, Lin KS, Wang YT, Chiang CL. Copper, nickel, and zinc cations biosorption properties of Gram-positive and Gram-negative MerP mercury-resistance proteins. J Taiwan Inst Chem Eng 2017. [DOI: 10.1016/j.jtice.2017.06.023] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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215
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Dash HR, Sahu M, Mallick B, Das S. Functional efficiency of MerA protein among diverse mercury resistant bacteria for efficient use in bioremediation of inorganic mercury. Biochimie 2017; 142:207-215. [DOI: 10.1016/j.biochi.2017.09.016] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Accepted: 09/26/2017] [Indexed: 10/18/2022]
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216
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Kuss J, Cordes F, Mohrholz V, Nausch G, Naumann M, Krüger S, Schulz-Bull DE. The Impact of the Major Baltic Inflow of December 2014 on the Mercury Species Distribution in the Baltic Sea. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:11692-11700. [PMID: 28885012 DOI: 10.1021/acs.est.7b03011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The Baltic Sea is a marginal sea characterized by stagnation periods of several years. Oxygen consumption in its deep waters leads to the buildup of sulfide from sulfate reduction. Some of the microorganisms responsible for these processes also transform reactive ionic mercury to neurotoxic methylmercury. Episodic inflows of oxygenated saline water from the North Sea temporally re-establish oxic life in deep waters of the Baltic Sea. Thus, this sea is an especially important region to better understand mercury species distributions in connection with variable redox conditions. Mercury species were measured on three Baltic Sea campaigns, during the preinflow, ongoing inflow, and subsiding inflow of water, respectively, to the central basin. The inflowing water caused the removal of total mercury by 600 nmol m-2 and of methylmercury by 214 nmol m-2 in the Gotland Deep, probably via attachment of the mercury compounds to sinking particles. It appears likely that the consequences of the oxygenation of Baltic Sea deep waters, which are the coprecipitation of mercury species and the resettlement of the oxic deep waters, could lead to the enhanced transfer of accumulated mercury and methylmercury to the planktonic food chain and finally to fish.
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Affiliation(s)
- Joachim Kuss
- Department of Marine Chemistry, Leibniz Institute for Baltic Sea Research (IOW) , Seestrasse 15, D-18119 Rostock-Warnemünde, Germany
| | - Florian Cordes
- Department of Marine Chemistry, Leibniz Institute for Baltic Sea Research (IOW) , Seestrasse 15, D-18119 Rostock-Warnemünde, Germany
| | - Volker Mohrholz
- Department of Physical Oceanography and Measurement & Instrumentation, Leibniz Institute for Baltic Sea Research (IOW) , Seestrasse 15, D-18119 Rostock-Warnemünde, Germany
| | - Günther Nausch
- Department of Marine Chemistry, Leibniz Institute for Baltic Sea Research (IOW) , Seestrasse 15, D-18119 Rostock-Warnemünde, Germany
| | - Michael Naumann
- Department of Physical Oceanography and Measurement & Instrumentation, Leibniz Institute for Baltic Sea Research (IOW) , Seestrasse 15, D-18119 Rostock-Warnemünde, Germany
| | - Siegfried Krüger
- Department of Physical Oceanography and Measurement & Instrumentation, Leibniz Institute for Baltic Sea Research (IOW) , Seestrasse 15, D-18119 Rostock-Warnemünde, Germany
| | - Detlef E Schulz-Bull
- Department of Marine Chemistry, Leibniz Institute for Baltic Sea Research (IOW) , Seestrasse 15, D-18119 Rostock-Warnemünde, Germany
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217
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Banerjee M, Roy G. Cleavage of Hg–C Bonds of Organomercurials Induced by ImOHSe via Two Distinct Pathways. Inorg Chem 2017; 56:12739-12750. [DOI: 10.1021/acs.inorgchem.7b01301] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Mainak Banerjee
- Department of Chemistry, School of Natural
Sciences, Shiv Nadar University, NH91, Dadri, Gautam Buddha Nagar, Uttar Pradesh 201314, India
| | - Gouriprasanna Roy
- Department of Chemistry, School of Natural
Sciences, Shiv Nadar University, NH91, Dadri, Gautam Buddha Nagar, Uttar Pradesh 201314, India
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218
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Xue H, Wu Z, Qiao D, Tong C, Zhao X. Global acquisition of genetic material from different bacteria into the staphylococcal cassette chromosome elements of a Staphylococcus epidermidis isolate. Int J Antimicrob Agents 2017; 50:581-587. [DOI: 10.1016/j.ijantimicag.2017.06.015] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Accepted: 06/24/2017] [Indexed: 10/19/2022]
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219
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Karri R, Banerjee M, Chalana A, Jha KK, Roy G. Activation of the Hg–C Bond of Methylmercury by [S2]-Donor Ligands. Inorg Chem 2017; 56:12102-12115. [DOI: 10.1021/acs.inorgchem.7b01048] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- Ramesh Karri
- Department of Chemistry, School of Natural
Sciences, Shiv Nadar University, NH91, Dadri, Gautam Buddha Nagar, Uttar Pradesh 201314, India
| | - Mainak Banerjee
- Department of Chemistry, School of Natural
Sciences, Shiv Nadar University, NH91, Dadri, Gautam Buddha Nagar, Uttar Pradesh 201314, India
| | - Ashish Chalana
- Department of Chemistry, School of Natural
Sciences, Shiv Nadar University, NH91, Dadri, Gautam Buddha Nagar, Uttar Pradesh 201314, India
| | - Kunal Kumar Jha
- Department of Chemistry, School of Natural
Sciences, Shiv Nadar University, NH91, Dadri, Gautam Buddha Nagar, Uttar Pradesh 201314, India
| | - Gouriprasanna Roy
- Department of Chemistry, School of Natural
Sciences, Shiv Nadar University, NH91, Dadri, Gautam Buddha Nagar, Uttar Pradesh 201314, India
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220
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Zhou J, Smith MD, Cooper CJ, Cheng X, Smith JC, Parks JM. Modeling of the Passive Permeation of Mercury and Methylmercury Complexes Through a Bacterial Cytoplasmic Membrane. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:10595-10604. [PMID: 28806072 DOI: 10.1021/acs.est.7b02204] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Cellular uptake and export are important steps in the biotransformation of mercury (Hg) by microorganisms. However, the mechanisms of transport across biological membranes remain unclear. Membrane-bound transporters are known to be relevant, but passive permeation may also be involved. Inorganic HgII and methylmercury ([CH3HgII]+) are commonly complexed with thiolate ligands. Here, we have performed extensive molecular dynamics simulations of the passive permeation of HgII and [CH3HgII]+ complexes with thiolate ligands through a model bacterial cytoplasmic membrane. We find that the differences in free energy between the individual complexes in bulk water and at their most favorable position within the membrane are ∼2 kcal mol-1. We provide a detailed description of the molecular interactions that drive the membrane crossing process. Favorable interactions with carbonyl and tail groups of phospholipids stabilize Hg-containing solutes in the tail-head interface region of the membrane. The calculated permeability coefficients for the neutral compounds CH3S-HgII-SCH3 and CH3HgII-SCH3 are on the order of 10-5 cm s-1. We conclude that small, nonionized Hg-containing species can permeate readily through cytoplasmic membranes.
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Affiliation(s)
- Jing Zhou
- Graduate School of Genome Science and Technology, University of Tennessee , Knoxville, Tennessee 37996, United States
- UT/ORNL Center for Molecular Biophysics, Biosciences Division, Oak Ridge National Laboratory , 1 Bethel Valley Road, Oak Ridge, Tennessee 37831-6309, United States
| | - Micholas Dean Smith
- UT/ORNL Center for Molecular Biophysics, Biosciences Division, Oak Ridge National Laboratory , 1 Bethel Valley Road, Oak Ridge, Tennessee 37831-6309, United States
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee , Knoxville, Tennessee 37996, United States
| | - Connor J Cooper
- Graduate School of Genome Science and Technology, University of Tennessee , Knoxville, Tennessee 37996, United States
- UT/ORNL Center for Molecular Biophysics, Biosciences Division, Oak Ridge National Laboratory , 1 Bethel Valley Road, Oak Ridge, Tennessee 37831-6309, United States
| | - Xiaolin Cheng
- UT/ORNL Center for Molecular Biophysics, Biosciences Division, Oak Ridge National Laboratory , 1 Bethel Valley Road, Oak Ridge, Tennessee 37831-6309, United States
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee , Knoxville, Tennessee 37996, United States
| | - Jeremy C Smith
- UT/ORNL Center for Molecular Biophysics, Biosciences Division, Oak Ridge National Laboratory , 1 Bethel Valley Road, Oak Ridge, Tennessee 37831-6309, United States
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee , Knoxville, Tennessee 37996, United States
| | - Jerry M Parks
- Graduate School of Genome Science and Technology, University of Tennessee , Knoxville, Tennessee 37996, United States
- UT/ORNL Center for Molecular Biophysics, Biosciences Division, Oak Ridge National Laboratory , 1 Bethel Valley Road, Oak Ridge, Tennessee 37831-6309, United States
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221
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Cavoura O, Brombach CC, Cortis R, Davidson CM, Gajdosechova Z, Keenan HE, Krupp EM. Mercury alkylation in freshwater sediments from Scottish canals. CHEMOSPHERE 2017; 183:27-35. [PMID: 28531556 DOI: 10.1016/j.chemosphere.2017.05.077] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2016] [Revised: 05/11/2017] [Accepted: 05/12/2017] [Indexed: 06/07/2023]
Abstract
Mercury concentrations were investigated in freshwater sediment from two canals in Scotland, UK. High concentrations found in the Union Canal (35.3-1200 mg kg-1) likely originate from historical munitions manufacture, with lower levels in the Forth & Clyde Canal (0.591-9.14 mg kg-1). Concentrations of methylmercury (MeHg) were low - from 6.02 to 18.6 μg kg-1 (0.001-0.023% of total Hg) in the Union Canal and from 3.44 to 14.1 μg kg-1 (0.11-0.58% of total Hg) in the Forth & Clyde Canal - and there was a significant inverse relationship between total Hg concentration and %MeHg. Total Hg concentration was significantly negatively correlated with pH and positively correlated with Fe content (in the Union Canal only) but not with organic matter, S content or the proportion of clay present. The MeHg concentration was not correlated with any of the above sediment parameters. Ethylmercury was detected in the most highly contaminated sediments from the Union Canal.
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Affiliation(s)
- Olga Cavoura
- National School of Public Health, Dept. of Environmental and Public Health Engineering, Athens, Greece; University of Strathclyde, Dept. of Civil and Environmental Engineering, Glasgow, Scotland, UK.
| | - C C Brombach
- University of Aberdeen, Dept. of Chemistry, Aberdeen, Scotland, UK
| | - R Cortis
- University of Strathclyde, WestCHEM, Dept. of Pure and Applied Chemistry, Glasgow, Scotland, UK
| | - C M Davidson
- University of Strathclyde, WestCHEM, Dept. of Pure and Applied Chemistry, Glasgow, Scotland, UK.
| | - Z Gajdosechova
- University of Aberdeen, Dept. of Chemistry, Aberdeen, Scotland, UK
| | - H E Keenan
- University of Strathclyde, Dept. of Civil and Environmental Engineering, Glasgow, Scotland, UK.
| | - E M Krupp
- University of Aberdeen, Dept. of Chemistry, Aberdeen, Scotland, UK.
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222
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Calcium (II) - and dipicolinic acid mediated-biostimulation of oil-bioremediation under multiple stresses by heat, oil and heavy metals. Sci Rep 2017; 7:9534. [PMID: 28842661 PMCID: PMC5573387 DOI: 10.1038/s41598-017-10121-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2017] [Accepted: 08/04/2017] [Indexed: 11/08/2022] Open
Abstract
The oil-producing Arabian Gulf states have hot summer seasons of about 7-month in length. Therefore, environmental oil spills should be bioremediated by the activity of indigenous, hydrocarbonoclastic (hydrocarbon-degrading) microorganisms with optimum growth at about 50 °C. Soils in such arid countries harbor thermophilic bacteria, whose oil-consumption potential is enhanced by calcium (II) - and dipicolinic acid (DPA)-supplement. Those organisms are, however, subjected to additional stresses including toxic effects of heavy metals that may be associated with the spilled oil. Our study highlighted the resistance of indigenous, thermophilic isolates to the heavy metals, mercury (II), cadmium (II), arsenic (II) and lead (II) at 50 °C. We also detected the uptake of heavy metals by 15 isolates at 50 °C, and identified the merA genes coding for Hg2+-resistance in 4 of the studied Hg2+-resistant isolates. Hg2+ was the most toxic metal and the metal toxicity was commonly higher in the presence of oil. The addition of Ca2+ and DPA enhanced the Hg2+-resistance among most of the isolates at 50 °C. Crude oil consumption at 50 °C by 4 selected isolates was inhibited by the tested heavy metals. However, Ca2+ and DPA limited this inhibition and enhanced oil-consumption, which exceeded by far the values in the control cultures.
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223
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Chatziefthimiou AD, Deitch EJ, Glover WB, Powell JT, Banack SA, Richer RA, Cox PA, Metcalf JS. Analysis of Neurotoxic Amino Acids from Marine Waters, Microbial Mats, and Seafood Destined for Human Consumption in the Arabian Gulf. Neurotox Res 2017; 33:143-152. [DOI: 10.1007/s12640-017-9772-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2017] [Revised: 06/07/2017] [Accepted: 06/13/2017] [Indexed: 01/15/2023]
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224
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Wang W, Peng Z, Baloch Z, Hu Y, Xu J, Zhang W, Fanning S, Li F. Genomic characterization of an extensively-drug resistance Salmonella enterica serotype Indiana strain harboring bla NDM-1 gene isolated from a chicken carcass in China. Microbiol Res 2017; 204:48-54. [PMID: 28870291 DOI: 10.1016/j.micres.2017.07.006] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2017] [Revised: 06/13/2017] [Accepted: 07/15/2017] [Indexed: 10/19/2022]
Abstract
OBJECTIVES The objective of this study was to genetically characterize the antimicrobial resistance mechanisms of Salmonella enterica serotype Indiana C629 isolated from a chicken carcass in China in 2014. METHODS Antimicrobial susceptibility against a panel of 23 antimicrobial agents was carried out on Salmonella enterica serotype Indiana C629 and assessed according to CLSI standards. Whole-genome sequencing of this isolate was conducted to obtain the complete genome of S. Indiana. RESULTS Salmonella Indiana C629 expressed an XDR phenotype being resistant to more than 20 antimicrobial agents, including imipenem and meropenem. From the analysis of the resistance mechanisms, two mutations were identified in subunit A of DNA gyrase within the quinolone resistance determining region, in addition to the acquisition of mobile efflux pumps encoding oqxA/B/R. Additionally, four beta-lactamases resistance genes (blaCTX-M-65, blaTEM-1, blaOXA-1, and blaNDM-1), five aminoglycosides resistance genes (aac(3)-IV, aac(6')-Ib-cr, aadA2, aadA5, and aph(4)-Ia), two phenicol resistance genes (catB3 and floR), and five trimethoprim/sulfamethoxazole resistance genes (sul1/2/3 and dfrA12/17) were also identified. A total of 191 virulence genes were identified. Among them, 57 belonged to type-three secretion system (T3SS) encoding genes, 55 belonged to fimbrial adherence encoding genes, and 39 belonged to flagella-encoding genes CONCLUSIONS: This study demonstrated that multi-resistance mechanisms consistent with an XDR-phenotype, along with various virulence encoding genes of a S. Indiana strain in China These findings highlight the importance of cooperation among different sectors in order to monitor the spread of resistant pathogens among food animal, foods of animal origin and human beings that might further take measures to protect consumers' health.
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Affiliation(s)
- Wei Wang
- Key Laboratory of Food Safety Risk Assessment, Ministry of Health, China National Center for Food Safety Risk Assessment, Beijing, PR China
| | - Zixin Peng
- Key Laboratory of Food Safety Risk Assessment, Ministry of Health, China National Center for Food Safety Risk Assessment, Beijing, PR China
| | - Zulqarnain Baloch
- College of Veterinary Medicine, South China Agricultural University, Guangzhou 510642, PR China.
| | - Yujie Hu
- Key Laboratory of Food Safety Risk Assessment, Ministry of Health, China National Center for Food Safety Risk Assessment, Beijing, PR China
| | - Jin Xu
- Key Laboratory of Food Safety Risk Assessment, Ministry of Health, China National Center for Food Safety Risk Assessment, Beijing, PR China
| | - Wenhui Zhang
- College of Veterinary Medicine, South China Agricultural University, Guangzhou 510642, PR China
| | - Séamus Fanning
- Key Laboratory of Food Safety Risk Assessment, Ministry of Health, China National Center for Food Safety Risk Assessment, Beijing, PR China; UCD-Centre for Food Safety, School of Public Health, Physiotherapy and Sports Science, University College Dublin, Belfield, Dublin D04 N2E5, Ireland; Institute for Global Food Security, School of Biological Sciences, Queen's University Belfast, Stranmillis Road, Belfast BT9 5AG, Northern Ireland, UK
| | - Fengqin Li
- Key Laboratory of Food Safety Risk Assessment, Ministry of Health, China National Center for Food Safety Risk Assessment, Beijing, PR China.
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225
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Amin A, Latif Z. Cloning, Expression, Isotope Labeling, and Purification of Transmembrane Protein MerF from Mercury Resistant Enterobacter sp. AZ-15 for NMR Studies. Front Microbiol 2017; 8:1250. [PMID: 28736549 PMCID: PMC5500634 DOI: 10.3389/fmicb.2017.01250] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Accepted: 06/21/2017] [Indexed: 11/15/2022] Open
Abstract
Mercury resistant (HgR) Enterobacter sp. AZ-15 was isolated from heavy metal polluted industrial wastewater samples near to districts Kasur and Sheikhupura, Pakistan. 16S rDNA ribotyping and phylogentic analysis showed 98% homology with already reported Enterobacter species. The merF gene encoding transmembrane protein-MerF was amplified from genomic DNA and ligated into pET31b+ vector using restriction endonucleases, SphI and XhoI. The genetic codons of merF gene encoding cysteine residues were mutated into codons, translating into serine residues by site-directed mutagenesis. Ketosteroid isomerase (KSI), a fusion tag which is present in pET31b+ vector, was used in the expression of merFm gene. KSI was used to drive the target peptide (MerFm) into inclusion bodies so that the peptide yield and purity were increased. The stable plasmid pET31b+:merFm was transformed into C43(DE3) E.coli cells. The high expression of uniformly 15N isotopically labeled-MerFm protein was induced with 1 mM IPTG. The purification of 15N-MerFm recombinant protein by Ni-NTA and size exclusion chromatography involved an unfolding/refolding procedure. The two-dimensional HSQC NMR spectra of MerFm protein showed the purity and correct number of resonances for each amide. 1H-15N HSQC NMR experiment also confirmed that no modification of the tryptophan residue occurred during cyanogen bromide cleavage. A small scale reservoir of Luria Bertani (LB) medium supplemented with 20 μg/ml of HgCl2 showed 90% detoxification of Hg by Enterobacter sp. AZ-15. The accumulation of Hg on the cell surface of this strain was visualized by scanning electron microscopy (SEM) which confirmed its potential use in Hg-bioremediation.
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Affiliation(s)
- Aatif Amin
- Department of Microbiology and Molecular Genetics, University of the PunjabLahore, Pakistan
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226
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Wang W, Baloch Z, Peng Z, Hu Y, Xu J, Fanning S, Li F. Genomic characterization of a large plasmid containing a bla NDM-1 gene carried on Salmonella enterica serovar Indiana C629 isolate from China. BMC Infect Dis 2017; 17:479. [PMID: 28687066 PMCID: PMC5501952 DOI: 10.1186/s12879-017-2515-5] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2017] [Accepted: 06/01/2017] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The bla NDM-1 gene in Salmonella species is mostly reported in clinical cases, but is rarely isolated from red and white meat in China. METHODS A Salmonella Indiana (S. Indiana) isolate was cultured from a chicken carcass procured from a slaughterhouse in China. Antimicrobial susceptibility was tested against a panel of agents. Whole-genome sequencing of the isolate was carried out and data was analyzed. RESULTS A large plasmid, denoted as plasmid pC629 (210,106 bp), containing a composite cassette, consisting of IS26-bla NDM-1-ble MBL -△trpF-tat-cutA-ISCR1-sul1-qacE△1-aadA2-dfrA12-intI1-IS26 was identified. The latter locus was physically linked with bla OXA-1, bla CTX-M-65, bla TEM-1-encoding genes. A mercury resistance operon merACDEPTR was also identified; it was flanked on the proximal side, among IS26 element and the distally located on the bla NDM-1 gene. Plasmid pC629 also contained 21 other antimicrobial resistance-encoding genes, such as aac(6')-Ib-cr, aac(3)-VI, aadA5, aph(4)-Ia, arr-3, blmS, brp, catB3, dfrA17, floR, fosA, mph(A), mphR, mrx, nimC/nimA, oqxA, oqxB, oqxR, rmtB, sul1, sul2. Two virulence genes were also identified on plasmid pC629. CONCLUSION To the best of our knowledge, this is the first report of bla NDM-1 gene being identified from a plasmid in a S. Indiana isolate cultured from chicken carcass in China.
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Affiliation(s)
- Wei Wang
- Key Laboratory of Food Safety Risk Assessment, Ministry of Health, China National Center for food safety Risk Assessment, Beijing, People's Republic of China
| | - Zulqarnain Baloch
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, 510642, People's Republic of China
| | - Zixin Peng
- Key Laboratory of Food Safety Risk Assessment, Ministry of Health, China National Center for food safety Risk Assessment, Beijing, People's Republic of China
| | - Yujie Hu
- Key Laboratory of Food Safety Risk Assessment, Ministry of Health, China National Center for food safety Risk Assessment, Beijing, People's Republic of China
| | - Jin Xu
- Key Laboratory of Food Safety Risk Assessment, Ministry of Health, China National Center for food safety Risk Assessment, Beijing, People's Republic of China
| | - Séamus Fanning
- Key Laboratory of Food Safety Risk Assessment, Ministry of Health, China National Center for food safety Risk Assessment, Beijing, People's Republic of China. .,UCD-Centre for Food Safety, School of Public Health, Physiotherapy and Sports Science, University College Dublin, Belfield D04 N2E5, Dublin, Ireland. .,Institute for Global Food Security, School of Biological Sciences, Queen's University Belfast, Stranmillis Road, Belfast, BT9 5AG, Northern Ireland.
| | - Fengqin Li
- Key Laboratory of Food Safety Risk Assessment, Ministry of Health, China National Center for food safety Risk Assessment, Beijing, People's Republic of China. .,Microbiology Laboratory, China National Centre for Food Safety Risk Assessment, No.7 Panjiayuan Nanli, Chaoyang District, Beijing, 100021, People's Republic of China.
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227
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Cesário R, Hintelmann H, Mendes R, Eckey K, Dimock B, Araújo B, Mota AM, Canário J. Evaluation of mercury methylation and methylmercury demethylation rates in vegetated and non-vegetated saltmarsh sediments from two Portuguese estuaries. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2017; 226:297-307. [PMID: 28390703 DOI: 10.1016/j.envpol.2017.03.075] [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: 10/19/2016] [Revised: 02/23/2017] [Accepted: 03/31/2017] [Indexed: 06/07/2023]
Abstract
Neurotoxic methylmercury (MMHg) is formed from inorganic divalent mercury (Hg2+). However, it is poorly understood to what extent different mercury (Hg) pools contribute to existent MMHg levels. In this study, ambient concentrations of total Hg (THg) and MMHg as well as rates of methylation and demethylation were measured simultaneously in sediments with and without salt-marsh plant vegetation, which were collected in Guadiana and Tagus estuaries, Portugal. Concurrent processes of Hg methylation and MMHg demethylation were directly monitored and compared by spiking sediments cores with stable isotope tracers of 199Hg2+ and CH3201Hg+ followed by gas chromatographic separation and isotope-specific detection using inductively coupled plasma mass spectrometry. Compared to the Guadiana estuary, where concentrations were comparatively low, THg and MMHg levels varied between vegetated and non-vegetated sediments collected at the Rosário site (ROS) of the Tagus estuary. Methylation (KM) and demethylation rates (KD) were also different between estuaries being dependent on the presence of vegetation. In addition, the type of macrophyte species influenced KM and KD values. In fact, the highest KM value was found in Sarcocornia fruticosa vegetated sediments at the Castro Marim site in Guadiana (CM, 0.160 day-1) and the lowest KM was observed in non-vegetated sediments at the Alcochete site in Tagus (ALC, 0.009 day-1). KD varied by a factor of three among sites with highest rates of demethylation observed in non-vegetated sediments in Guadiana (12 ± 1.3 day-1, corresponding to a half-life of 1.4 ± 0.2 h). This study clearly shows that the presence of vegetation in sediments favors the formation of MMHg. Moreover, this effect might be site specific and further studies are needed to confirm the findings reported here.
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Affiliation(s)
- Rute Cesário
- Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, Lisboa 1, 1049-001 Lisboa, Portugal; IPMA-Instituto Português do Mar e Atmosfera, Av. Brasília, 1449-006 Lisboa, Portugal
| | - Holger Hintelmann
- Water Quality Centre, Trent University, 1600 West Bank Drive, Peterborough, ON K9J 0G2, Canada
| | - Ricardo Mendes
- IPMA-Instituto Português do Mar e Atmosfera, Av. Brasília, 1449-006 Lisboa, Portugal
| | - Kevin Eckey
- Institute of Inorganic and Analytical Chemistry, University of Muenster, Schlossplatz 2, 48149 Munster, Germany
| | - Brian Dimock
- Water Quality Centre, Trent University, 1600 West Bank Drive, Peterborough, ON K9J 0G2, Canada
| | - Beatriz Araújo
- Centro de Biociências e Biotecnologia, Universidade Estadual do Norte Fluminense, Av. Alberto Lamego, 2000, Horto, Campus dos Goytacazes, Rio de Janeiro, Brazil
| | - Ana Maria Mota
- Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, Lisboa 1, 1049-001 Lisboa, Portugal
| | - João Canário
- Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, Lisboa 1, 1049-001 Lisboa, Portugal.
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228
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Wang X, Wu F, Wang WX. In Vivo Mercury Demethylation in a Marine Fish (Acanthopagrus schlegeli). ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:6441-6451. [PMID: 28514845 DOI: 10.1021/acs.est.7b00923] [Citation(s) in RCA: 66] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Mercury (Hg) in fish has attracted public attention for decades, and methylmercury (MeHg) is the predominant form in fish. However, the in vivo MeHg demethylation and its influence on Hg level in fish have not been well-addressed. The present study investigated the in vivo demethylation process in a marine fish (black seabream, Acanthopagrus schlegeli) under dietary MeHg exposure and depuration and quantified the biotransformation and interorgan transportation of MeHg by developing a physiologically based pharmacokinetic (PBPK) model. After exposure, we observed a 2-fold increase of the whole-body inorganic Hg (IHg), indicating the existence of an in vivo demethylation process. The results strongly suggested that the intestine played a predominant role in MeHg demethylation with a significant rate (6.6 ± 1.7 day-1) during exposure, whereas the hepatic demethylation appeared to be an extremely slow (0.011 ± 0.001 day-1) process and could hardly affect the whole-fish Hg level. Moreover, demethylation in the intestine served as an important pathway for MeHg detoxification. Our study also pointed out that in vivo MeHg demethylation could influence Hg level and speciation in fish although food is the major pathway for Hg accumulation. Enhancing in vivo MeHg biotransformation (especially in the intestine) could be a potential key solution in minimizing Hg contamination in fish. The related factors involved in intestinal demethylation deserve more attention in the future.
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Affiliation(s)
- Xun Wang
- Division of Life Science, The Hong Kong University of Science and Technology (HKUST) , Clear Water Bay, Kowloon, Hong Kong, China
- Marine Environmental Laboratory, HKUST Shenzhen Research Institute , Shenzhen 518057, China
| | - Fengchang Wu
- State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences , Beijing 100012, China
| | - Wen-Xiong Wang
- Division of Life Science, The Hong Kong University of Science and Technology (HKUST) , Clear Water Bay, Kowloon, Hong Kong, China
- Marine Environmental Laboratory, HKUST Shenzhen Research Institute , Shenzhen 518057, China
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229
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Thomas SA, Gaillard JF. Cysteine Addition Promotes Sulfide Production and 4-Fold Hg(II)-S Coordination in Actively Metabolizing Escherichia coli. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:4642-4651. [PMID: 28353340 DOI: 10.1021/acs.est.6b06400] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The bacterial uptake of mercury(II), Hg(II), is believed to be energy-dependent and is enhanced by cysteine in diverse species of bacteria under aerobic and anaerobic conditions. To gain insight into this Hg(II) biouptake pathway, we have employed X-ray absorption spectroscopy (XAS) to investigate the relationship between exogenous cysteine, cellular metabolism, cellular localization, and Hg(II) coordination in aerobically respiring Escherichia coli (E. coli). We show that cells harvested in exponential growth phase consistently display mixtures of 2-fold and 4-fold Hg(II) coordination to sulfur (Hg-S2 and Hg-S4), with added cysteine enhancing Hg-S4 formation. In contrast, cells in stationary growth phase or cells treated with a protonophore causing a decrease in cellular ATP predominantly contain Hg-S2, regardless of cysteine addition. Our XAS results favor metacinnabar (β-HgS) as the Hg-S4 species, which we show is associated with both the cell envelope and cytoplasm. Additionally, we observe that added cysteine abiotically oxidizes to cystine and exponentially growing E. coli degrade high cysteine concentrations (100-1000 μM) into sulfide. Thermodynamic calculations confirm that cysteine-induced sulfide biosynthesis can promote the formation of dissolved and particulate Hg(II)-sulfide species. This report reveals new complexities arising in Hg(II) bioassays with cysteine and emphasizes the need for considering changes in chemical speciation as well as growth stage.
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Affiliation(s)
- Sara A Thomas
- Department of Civil and Environmental Engineering, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Jean-François Gaillard
- Department of Civil and Environmental Engineering, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States
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230
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Binding of Hg by bacterial extracellular polysaccharide: a possible role in Hg tolerance. Appl Microbiol Biotechnol 2017; 101:5493-5503. [DOI: 10.1007/s00253-017-8239-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Revised: 03/05/2017] [Accepted: 03/09/2017] [Indexed: 12/21/2022]
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231
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Pan S, Feng C, Lin J, Cheng L, Wang C, Zuo Y. Occurrence and photodegradation of methylmercury in surface water of Wen-Rui-Tang River network, Wenzhou, China. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2017; 24:11289-11298. [PMID: 28299570 DOI: 10.1007/s11356-017-8708-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2016] [Accepted: 02/27/2017] [Indexed: 06/06/2023]
Abstract
The spatial distribution and seasonal variations of methylmercury (MeHg) in Wen-Rui-Tang (WRT) River network were investigated by monitoring the MeHg concentrations in surface water samples collected from 30 sites across the river network over four seasons. Detection frequencies and concentrations of MeHg were generally higher in January, indicating that low sunlight irradiation, wind speed, and temperature conditions might enhance the persistence of MeHg in surface water. The MeHg levels varied with sampling locations, with the highest concentrations being observed in the industrial area especially around wastewater outfall, revealing that the mercury contamination in WRT River mainly comes from the industrial wastewater. Photodegradation of MeHg in WRT River surface water and the effects of natural constituents such as fulvic acid (FA), ferric ions (Fe3+), nitrate (NO3-), and dissolved oxygen on the MeHg photodegradation in aqueous solutions were studied under the simulated sunlight. The experimental data indicated that the indirect photodecomposition of MeHg occurred in WRT River surface water. Photodegradation of MeHg in FA solution was initiated by triplet 3FA* or MeHg-FA* via electron transfer interaction under light irradiations. The Fe3+ and NO3- can absorb light energy to produce ·OH and enhance the photochemical degradation of MeHg. The MeHg photodecompositions in FA, nitrate, and Fe3+ solutions were markedly accelerated after removing the dissolved oxygen.
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Affiliation(s)
- Shuihong Pan
- College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, 325035, China
| | - Chuchu Feng
- College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, 325035, China
| | - Jialu Lin
- College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, 325035, China
| | - Lidong Cheng
- College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, 325035, China
| | - Chengjun Wang
- College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, 325035, China.
| | - Yuegang Zuo
- Department of Chemistry and Biochemistry, University of Massachusetts Dartmouth, North Dartmouth, MA, 02747, USA.
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232
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Banerjee M, Karri R, Chalana A, Das R, Rai RK, Rawat KS, Pathak B, Roy G. Protection of Endogenous Thiols against Methylmercury with Benzimidazole-Based Thione by Unusual Ligand-Exchange Reactions. Chemistry 2017; 23:5696-5707. [DOI: 10.1002/chem.201605238] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2016] [Indexed: 12/27/2022]
Affiliation(s)
- Mainak Banerjee
- Department of Chemistry; School of Natural Sciences; Shiv Nadar University, NH91, Dadri; Gautam Buddha Nagar, UP 201314 India
| | - Ramesh Karri
- Department of Chemistry; School of Natural Sciences; Shiv Nadar University, NH91, Dadri; Gautam Buddha Nagar, UP 201314 India
| | - Ashish Chalana
- Department of Chemistry; School of Natural Sciences; Shiv Nadar University, NH91, Dadri; Gautam Buddha Nagar, UP 201314 India
| | - Ranajit Das
- Department of Chemistry; School of Natural Sciences; Shiv Nadar University, NH91, Dadri; Gautam Buddha Nagar, UP 201314 India
| | - Rakesh Kumar Rai
- Department of Chemistry; School of Natural Sciences; Shiv Nadar University, NH91, Dadri; Gautam Buddha Nagar, UP 201314 India
| | - Kuber Singh Rawat
- Discipline of Chemistry and Discipline of Metallurgy Engineering and Materials Science; Indian Institute of Technology (IIT) Indore; Indore, MP 453552 India
| | - Biswarup Pathak
- Discipline of Chemistry and Discipline of Metallurgy Engineering and Materials Science; Indian Institute of Technology (IIT) Indore; Indore, MP 453552 India
| | - Gouriprasanna Roy
- Department of Chemistry; School of Natural Sciences; Shiv Nadar University, NH91, Dadri; Gautam Buddha Nagar, UP 201314 India
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233
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Boyd ES, Yu RQ, Barkay T, Hamilton TL, Baxter BK, Naftz DL, Marvin-DiPasquale M. Effect of salinity on mercury methylating benthic microbes and their activities in Great Salt Lake, Utah. THE SCIENCE OF THE TOTAL ENVIRONMENT 2017; 581-582:495-506. [PMID: 28057343 DOI: 10.1016/j.scitotenv.2016.12.157] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2016] [Revised: 12/22/2016] [Accepted: 12/22/2016] [Indexed: 06/06/2023]
Abstract
Surface water and biota from Great Salt Lake (GSL) contain some of the highest documented concentrations of total mercury (THg) and methylmercury (MeHg) in the United States. In order to identify potential biological sources of MeHg and controls on its production in this ecosystem, THg and MeHg concentrations, rates of Hg(II)-methylation and MeHg degradation, and abundances and compositions of archaeal and bacterial 16 rRNA gene transcripts were determined in sediment along a salinity gradient in GSL. Rates of Hg(II)-methylation were inversely correlated with salinity and were at or below the limits of detection in sediment sampled from areas with hypersaline surface water. The highest rates of Hg(II)-methylation were measured in sediment with low porewater salinity, suggesting that benthic microbial communities inhabiting less saline environments are supplying the majority of MeHg in the GSL ecosystem. The abundance of 16S rRNA gene transcripts affiliated with the sulfate reducer Desulfobacterium sp. was positively correlated with MeHg concentrations and Hg(II)-methylation rates in sediment, indicating a potential role for this taxon in Hg(II)-methylation in low salinity areas of GSL. Reactive inorganic Hg(II) (a proxy used for Hg(II) available for methylation) and MeHg concentrations were inversely correlated with salinity. Thus, constraints imposed by salinity on Hg(II)-methylating populations and the availability of Hg(II) for methylation are inferred to result in higher MeHg production potentials in lower salinity environments. Benthic microbial MeHg degradation was also most active in lower salinity environments. Collectively, these results suggest an important role for sediment anoxia and microbial sulfate reducers in the production of MeHg in low salinity GSL sub-habitats and may indicate a role for salinity in constraining Hg(II)-methylation and MeHg degradation activities by influencing the availability of Hg(II) for methylation.
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Affiliation(s)
- Eric S Boyd
- Department of Microbiology and Immunology, Montana State University, Bozeman, MT 59717, United States.
| | - Ri-Qing Yu
- Department of Biochemistry and Microbiology, Rutgers University, New Brunswick, NJ 08901, United States
| | - Tamar Barkay
- Department of Biochemistry and Microbiology, Rutgers University, New Brunswick, NJ 08901, United States
| | - Trinity L Hamilton
- Department of Biological Sciences, University of Cincinnati, Cincinnati, OH 45221, United States
| | - Bonnie K Baxter
- Department of Biology, Westminster College, Salt Lake City, UT 84105, United States
| | - David L Naftz
- United States Geological Survey, Helena, MT 59601, United States
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234
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Undabarrena A, Ugalde JA, Seeger M, Cámara B. -Genomic data mining of the marine actinobacteria Streptomyces sp. H-KF8 unveils insights into multi-stress related genes and metabolic pathways involved in antimicrobial synthesis. PeerJ 2017; 5:e2912. [PMID: 28229018 PMCID: PMC5312570 DOI: 10.7717/peerj.2912] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2016] [Accepted: 12/14/2016] [Indexed: 12/25/2022] Open
Abstract
Streptomyces sp. H-KF8 is an actinobacterial strain isolated from marine sediments of a Chilean Patagonian fjord. Morphological characterization together with antibacterial activity was assessed in various culture media, revealing a carbon-source dependent activity mainly against Gram-positive bacteria (S. aureus and L. monocytogenes). Genome mining of this antibacterial-producing bacterium revealed the presence of 26 biosynthetic gene clusters (BGCs) for secondary metabolites, where among them, 81% have low similarities with known BGCs. In addition, a genomic search in Streptomyces sp. H-KF8 unveiled the presence of a wide variety of genetic determinants related to heavy metal resistance (49 genes), oxidative stress (69 genes) and antibiotic resistance (97 genes). This study revealed that the marine-derived Streptomyces sp. H-KF8 bacterium has the capability to tolerate a diverse set of heavy metals such as copper, cobalt, mercury, chromate and nickel; as well as the highly toxic tellurite, a feature first time described for Streptomyces. In addition, Streptomyces sp. H-KF8 possesses a major resistance towards oxidative stress, in comparison to the soil reference strain Streptomyces violaceoruber A3(2). Moreover, Streptomyces sp. H-KF8 showed resistance to 88% of the antibiotics tested, indicating overall, a strong response to several abiotic stressors. The combination of these biological traits confirms the metabolic versatility of Streptomyces sp. H-KF8, a genetically well-prepared microorganism with the ability to confront the dynamics of the fjord-unique marine environment.
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Affiliation(s)
- Agustina Undabarrena
- Departmento de Química & Centro de Biotecnología, Universidad Técnica Federico Santa María , Valparaiso , Chile
| | - Juan A Ugalde
- Centro de Genética y Genómica, Facultad de Medicina Clinica Alemana, Universidad del Desarrollo , Santiago , Chile
| | - Michael Seeger
- Departmento de Química & Centro de Biotecnología, Universidad Técnica Federico Santa María , Valparaiso , Chile
| | - Beatriz Cámara
- Departmento de Química & Centro de Biotecnología, Universidad Técnica Federico Santa María , Valparaiso , Chile
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235
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Kim H, Soerensen AL, Hur J, Heimbürger LE, Hahm D, Rhee TS, Noh S, Han S. Methylmercury Mass Budgets and Distribution Characteristics in the Western Pacific Ocean. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:1186-1194. [PMID: 28013537 DOI: 10.1021/acs.est.6b04238] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Methylmercury (MeHg) accumulation in marine organisms poses serious ecosystem and human health risk, yet the sources of MeHg in the surface and subsurface ocean remain uncertain. Here, we report the first MeHg mass budgets for the Western Pacific Ocean estimated based on cruise observations. We found the major net source of MeHg in surface water to be vertical diffusion from the subsurface layer (1.8-12 nmol m-2 yr-1). A higher upward diffusion in the North Pacific (12 nmol m-2 yr-1) than in the Equatorial Pacific (1.8-5.7 nmol m-2 yr-1) caused elevated surface MeHg concentrations observed in the North Pacific. We furthermore found that the slope of the linear regression line for MeHg versus apparent oxygen utilization in the Equatorial Pacific was about 2-fold higher than that in the North Pacific. We suggest this could be explained by redistribution of surface water in the tropical convergence-divergence zone, supporting active organic carbon decomposition in the Equatorial Pacific Ocean. On the basis of this study, we predict oceanic regions with high organic carbon remineralization to have enhanced MeHg concentrations in both surface and subsurface waters.
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Affiliation(s)
- Hyunji Kim
- School of Earth Sciences and Environmental Engineering, Gwangju Institute of Science and Technology (GIST) , Gwangju 500-712, Republic of Korea
| | - Anne L Soerensen
- Department of Environmental Science and Analytical Chemistry, Stockholm University , Stockholm SE-11418, Sweden
| | - Jin Hur
- Department of Environment and Energy, Sejong University , Seoul 143-747, Republic of Korea
| | - Lars-Eric Heimbürger
- Aix Marseille Université, CNRS/INSU, Université de Toulon, IRD, Mediterranean Institute of Oceanography (MIO) UM 110, 13288 Marseille, France
| | - Doshik Hahm
- Department of Oceanography, Pusan National University , Busan 46241, Republic of Korea
| | - Tae Siek Rhee
- Korea Polar Research Institute , Incheon 406-840, Republic of Korea
| | - Seam Noh
- School of Earth Sciences and Environmental Engineering, Gwangju Institute of Science and Technology (GIST) , Gwangju 500-712, Republic of Korea
| | - Seunghee Han
- School of Earth Sciences and Environmental Engineering, Gwangju Institute of Science and Technology (GIST) , Gwangju 500-712, Republic of Korea
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236
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Dranguet P, Le Faucheur S, Cosio C, Slaveykova VI. Influence of chemical speciation and biofilm composition on mercury accumulation by freshwater biofilms. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2017; 19:38-49. [PMID: 27942649 DOI: 10.1039/c6em00493h] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Mercury (Hg) is a pollutant of high concern for aquatic systems due to the biomagnification of its methylated form along the food chain. However, in contrast to other metals, gaining knowledge of its bioavailable forms for aquatic microorganisms remains challenging, making Hg risk assessment difficult. Ubiquitous and sessile freshwater biofilms are well known to accumulate and to transform Hg present in their ambient environment. The present study thus aims to evaluate whether non-extractable (proxy of intracellular) Hg accumulated by biofilms could be a good indicator of Hg bioavailability for microorganisms in freshwater. To that end, the link between Hg concentration and speciation, as well as biofilm composition (percentage of abiotic, biotic, chlorophyll and phycocyanin-fractions and abundance of dsrA, gcs, merA and hgcA bacterial genes) and biofilm Hg accumulation was examined. The studied biofilms were grown on artificial substrata in four reservoirs along the Olt River (Romania), which was contaminated by Hg coming from chlor-alkali plant effluents. The 0.45 μm-filterable Hg concentrations in ambient waters were measured and inorganic IHg speciation was modelled. Biofilms were analyzed for their non-extractable IHg and methylmercury (MeHg) contents as well as for their composition. The non-extractable IHg content was related, but not significantly, to the concentration of total IHg (r2 = 0.88, p = 0.061) whereas a significant correlation was found with the predicted IHg concentration that is not bound to dissolved organic matter (r2 = 0.95, p = 0.027), despite its extremely low concentrations (10-25 M), showing a limitation of the thermodynamic Hg modelling to predict Hg bioavailability. The studied biofilms were different in biomass and composition and a principal component analysis showed that the non-extractable IHg content correlated with the abundance of the merA and hgcA genes, while MeHg accumulation was only linked with the abundance of the rRNA 16S gene. The present study suggests that non-extractable IHg concentrations in biofilms are a useful proxy of IHg bioavailable forms in waters whereas the hgcA and merA genes are good biomarkers of both biofilm IHg exposure and bioavailability.
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Affiliation(s)
- P Dranguet
- University of Geneva, Faculty of Science, Earth and Environmental Sciences, Department F.-A. Forel for Environmental and Aquatic Sciences, Uni Carl Vogt, 66 Bvd. Carl Vogt, CH-1211 Geneva, Switzerland.
| | - S Le Faucheur
- University of Geneva, Faculty of Science, Earth and Environmental Sciences, Department F.-A. Forel for Environmental and Aquatic Sciences, Uni Carl Vogt, 66 Bvd. Carl Vogt, CH-1211 Geneva, Switzerland.
| | - C Cosio
- University of Geneva, Faculty of Science, Earth and Environmental Sciences, Department F.-A. Forel for Environmental and Aquatic Sciences, Uni Carl Vogt, 66 Bvd. Carl Vogt, CH-1211 Geneva, Switzerland.
| | - V I Slaveykova
- University of Geneva, Faculty of Science, Earth and Environmental Sciences, Department F.-A. Forel for Environmental and Aquatic Sciences, Uni Carl Vogt, 66 Bvd. Carl Vogt, CH-1211 Geneva, Switzerland.
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237
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Wahba HM, Stevenson MJ, Mansour A, Sygusch J, Wilcox DE, Omichinski JG. Structural and Biochemical Characterization of Organotin and Organolead Compounds Binding to the Organomercurial Lyase MerB Provide New Insights into Its Mechanism of Carbon-Metal Bond Cleavage. J Am Chem Soc 2017; 139:910-921. [PMID: 27989130 DOI: 10.1021/jacs.6b11327] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The organomercurial lyase MerB has the unique ability to cleave carbon-Hg bonds, and structural studies indicate that three residues in the active site (C96, D99, and C159 in E. coli MerB) play important roles in the carbon-Hg bond cleavage. However, the role of each residue in carbon-metal bond cleavage has not been well-defined. To do so, we have structurally and biophysically characterized the interaction of MerB with a series of organotin and organolead compounds. Studies with two known inhibitors of MerB, dimethyltin (DMT) and triethyltin (TET), reveal that they inhibit by different mechanisms. In both cases the initial binding is to D99, but DMT subsequently binds to C96, which induces a conformation change in the active site. In contrast, diethyltin (DET) is a substrate for MerB and the SnIV product remains bound in the active site in a coordination similar to that of HgII following cleavage of organomercurial compounds. The results with analogous organolead compounds are similar in that trimethyllead (TML) is not cleaved and binds only to D99, whereas diethyllead (DEL) is a substrate and the PbIV product remains bound in the active site. Binding and cleavage is an exothermic reaction, while binding to D99 has negligible net heat flow. These results show that initial binding of organometallic compounds to MerB occurs at D99 followed, in some cases, by cleavage and loss of the organic moieties and binding of the metal ion product to C96, D99, and C159. The N-terminus of MerA is able to extract the bound PbVI but not the bound SnIV. These results suggest that MerB could be utilized for bioremediation applications, but certain organolead and organotin compounds may present an obstacle by inhibiting the enzyme.
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Affiliation(s)
- Haytham M Wahba
- Département de Biochimie et Médicine Moléculaire, Université de Montréal , Montréal, Quebec H3C 3J7 Canada.,Faculty of Pharmacy, Beni-suef University , Beni-suef, Egypt
| | - Michael J Stevenson
- Department of Chemistry, Dartmouth College , Hanover, New Hampshire 03755, United States
| | - Ahmed Mansour
- Département de Biochimie et Médicine Moléculaire, Université de Montréal , Montréal, Quebec H3C 3J7 Canada
| | - Jurgen Sygusch
- Département de Biochimie et Médicine Moléculaire, Université de Montréal , Montréal, Quebec H3C 3J7 Canada
| | - Dean E Wilcox
- Department of Chemistry, Dartmouth College , Hanover, New Hampshire 03755, United States
| | - James G Omichinski
- Département de Biochimie et Médicine Moléculaire, Université de Montréal , Montréal, Quebec H3C 3J7 Canada
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238
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Mahbub KR, Krishnan K, Naidu R, Megharaj M. Mercury remediation potential of a mercury resistant strain Sphingopyxis sp. SE2 isolated from contaminated soil. J Environ Sci (China) 2017; 51:128-137. [PMID: 28115122 DOI: 10.1016/j.jes.2016.06.032] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2016] [Revised: 06/08/2016] [Accepted: 06/27/2016] [Indexed: 06/06/2023]
Abstract
A mercury resistant bacterial strain SE2 was isolated from contaminated soil. The 16s rRNA gene sequencing confirms the strain as Sphingopyxis belongs to the Sphingomonadaceae family of the α-Proteobacteria group. The isolate showed high resistance to mercury with estimated concentrations of Hg that caused 50% reduction in growth (EC50) of 5.97 and 6.22mg/L and minimum inhibitory concentrations (MICs) of 32.19 and 34.95mg/L in minimal and rich media, respectively. The qualitative detection of volatilized mercury and the presence of mercuric reductase enzyme proved that the strain SE2 can potentially remediate mercury. ICP-QQQ-MS analysis of the remaining mercury in experimental broths indicated that a maximum of 44% mercury was volatilized within 6hr by live SE2 culture. Furthermore a small quantity (23%) of mercury was accumulated in live cell pellets. While no volatilization was caused by dead cells, sorption of mercury was confirmed. The mercuric reductase gene merA was amplified and sequenced. Homology was observed among the amino acid sequences of mercuric reductase enzyme of different organisms from α-Proteobacteria and ascomycota groups.
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Affiliation(s)
- Khandaker Rayhan Mahbub
- Global Centre for Environmental Remediation (GCER), Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC-CARE), Faculty of Science and Information Technology, The University of Newcastle, Callaghan, NSW 2308, Australia.
| | - Kannan Krishnan
- Global Centre for Environmental Remediation (GCER), Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC-CARE), Faculty of Science and Information Technology, The University of Newcastle, Callaghan, NSW 2308, Australia
| | - Ravi Naidu
- Global Centre for Environmental Remediation (GCER), Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC-CARE), Faculty of Science and Information Technology, The University of Newcastle, Callaghan, NSW 2308, Australia
| | - Mallavarapu Megharaj
- Global Centre for Environmental Remediation (GCER), Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC-CARE), Faculty of Science and Information Technology, The University of Newcastle, Callaghan, NSW 2308, Australia.
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239
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Gutiérrez-Preciado A, Vargas-Chávez C, Reyes-Prieto M, Ordoñez OF, Santos-García D, Rosas-Pérez T, Valdivia-Anistro J, Rebollar EA, Saralegui A, Moya A, Merino E, Farías ME, Latorre A, Souza V. The genomic sequence of Exiguobacterium chiriqhucha str. N139 reveals a species that thrives in cold waters and extreme environmental conditions. PeerJ 2017; 5:e3162. [PMID: 28439458 PMCID: PMC5399880 DOI: 10.7717/peerj.3162] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Accepted: 03/08/2017] [Indexed: 02/05/2023] Open
Abstract
We report the genome sequence of Exiguobacterium chiriqhucha str. N139, isolated from a high-altitude Andean lake. Comparative genomic analyses of the Exiguobacterium genomes available suggest that our strain belongs to the same species as the previously reported E. pavilionensis str. RW-2 and Exiguobacterium str. GIC 31. We describe this species and propose the chiriqhucha name to group them. 'Chiri qhucha' in Quechua means 'cold lake', which is a common origin of these three cosmopolitan Exiguobacteria. The 2,952,588-bp E. chiriqhucha str. N139 genome contains one chromosome and three megaplasmids. The genome analysis of the Andean strain suggests the presence of enzymes that confer E. chiriqhucha str. N139 the ability to grow under multiple environmental extreme conditions, including high concentrations of different metals, high ultraviolet B radiation, scavenging for phosphorous and coping with high salinity. Moreover, the regulation of its tryptophan biosynthesis suggests that novel pathways remain to be discovered, and that these pathways might be fundamental in the amino acid metabolism of the microbial community from Laguna Negra, Argentina.
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Affiliation(s)
- Ana Gutiérrez-Preciado
- Unidad de Genética Evolutiva, Instituto Cavanilles de Biodiversidad y Biología Evolutiva, Universidad de Valencia, Calle Catedrático José Beltrán Martínez, Paterna, Valencia, Spain
- Current affiliation: Ecologie Systématique Evolution, CNRS, AgroParisTech, Université Paris Sud (Paris XI), Orsay, France
| | - Carlos Vargas-Chávez
- Unidad de Genética Evolutiva, Instituto Cavanilles de Biodiversidad y Biología Evolutiva, Universidad de Valencia, Calle Catedrático José Beltrán Martínez, Paterna, Valencia, Spain
| | - Mariana Reyes-Prieto
- Unidad de Genética Evolutiva, Instituto Cavanilles de Biodiversidad y Biología Evolutiva, Universidad de Valencia, Calle Catedrático José Beltrán Martínez, Paterna, Valencia, Spain
| | - Omar F. Ordoñez
- Laboratorio de Investigaciones Microbiológicas de Lagunas Andinas, Planta Piloto de Procesos Industriales Microbiológicos (PROIMI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Av. Belgrano y Pasaje Caseros, San Miguel de Tucumán, Argentina
| | - Diego Santos-García
- Unidad de Genética Evolutiva, Instituto Cavanilles de Biodiversidad y Biología Evolutiva, Universidad de Valencia, Calle Catedrático José Beltrán Martínez, Paterna, Valencia, Spain
- Current affiliation: Department of Entomology, Hebrew University of Jerusalem, Rehovot, Israel
| | - Tania Rosas-Pérez
- Unidad de Genética Evolutiva, Instituto Cavanilles de Biodiversidad y Biología Evolutiva, Universidad de Valencia, Calle Catedrático José Beltrán Martínez, Paterna, Valencia, Spain
| | - Jorge Valdivia-Anistro
- Carrera de Biología, Faculta de Estudios Superiores Zaragoza, UNAM, Mexico City, Mexico
- Departamento de Ecología Evolutiva, Instituto de Ecología, Universidad Nacional Autónoma de México coyoacan, Mexico City, México
| | - Eria A. Rebollar
- Department of Biology, James Madison University, Harrisonburg, VI, United States of America
| | - Andrés Saralegui
- Laboratorio Nacional de Microscopía Avanzada, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, México
| | - Andrés Moya
- Unidad de Genética Evolutiva, Instituto Cavanilles de Biodiversidad y Biología Evolutiva, Universidad de Valencia, Calle Catedrático José Beltrán Martínez, Paterna, Valencia, Spain
| | - Enrique Merino
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, México
| | - María Eugenia Farías
- Laboratorio de Investigaciones Microbiológicas de Lagunas Andinas, Planta Piloto de Procesos Industriales Microbiológicos (PROIMI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Av. Belgrano y Pasaje Caseros, San Miguel de Tucumán, Argentina
| | - Amparo Latorre
- Unidad de Genética Evolutiva, Instituto Cavanilles de Biodiversidad y Biología Evolutiva, Universidad de Valencia, Calle Catedrático José Beltrán Martínez, Paterna, Valencia, Spain
| | - Valeria Souza
- Departamento de Ecología Evolutiva, Instituto de Ecología, Universidad Nacional Autónoma de México coyoacan, Mexico City, México
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Mercury alters the bacterial community structure and diversity in soil even at concentrations lower than the guideline values. Appl Microbiol Biotechnol 2016; 101:2163-2175. [PMID: 27873000 DOI: 10.1007/s00253-016-7965-y] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Revised: 10/26/2016] [Accepted: 10/31/2016] [Indexed: 12/13/2022]
Abstract
This study evaluated the effect of inorganic mercury (Hg) on bacterial community and diversity in different soils. Three soils-neutral, alkaline and acidic-were spiked with six different concentrations of Hg ranging from 0 to 200 mg kg-1 and aged for 90 days. At the end of the ageing period, 18 samples from three different soils were investigated for bacterial community structure and soil physicochemical properties. Illumina MiSeq-based 16s ribosomal RNA (rRNA) amplicon sequencing revealed the alteration in the bacterial community between un-spiked control soils and Hg-spiked soils. Among the bacterial groups, Actinobacteria (22.65%) were the most abundant phyla in all samples followed by Proteobacteria (21.95%), Bacteroidetes (4.15%), Firmicutes (2.9%) and Acidobacteria (2.04%). However, the largest group showing increased abundance with higher Hg doses was the unclassified group (45.86%), followed by Proteobacteria. Mercury had a considerable negative impact on key soil functional bacteria such as ammonium oxidizers and nitrifiers. Canonical correspondence analysis (CCA) indicated that among the measured soil properties, Hg had a major influence on bacterial community structure. Furthermore, nonlinear regression analysis confirmed that Hg significantly decreased soil bacterial alpha diversity in lower organic carbon containing neutral and alkaline soils, whereas in acidic soil with higher organic carbon there was no significant correlation. EC20 values obtained by a nonlinear regression analysis indicated that Hg significantly decreased soil bacterial diversity in concentrations lower than several guideline values.
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241
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A broad mercury resistant strain of Pseudomonas putida secretes pyoverdine under limited iron conditions and high mercury concentrations. Biometals 2016; 29:1097-1106. [PMID: 27848043 DOI: 10.1007/s10534-016-9980-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Accepted: 10/28/2016] [Indexed: 10/20/2022]
Abstract
The Pseudomonas putida FB1, known as a broad-spectrum mercury resistant strain, becomes yellow-green due to the secretion of pyoverdine (PVDs) under limited iron conditions and high mercury concentrations. Different modified Nelson's media were obtained by adding mercury, iron, and the complexing agent nitrilotriacetic acid to demonstrate that the strain produces only the highest concentrations of PVDs due to the induction with 25 µM Hg2+. An amount of 250 mg PVDs was purified from the supernatant of 1 litre culture. The various forms of PVDs were characterized using different techniques such as fluorescence spectroscopy, high performance liquid chromatography coupled with high resolution mass spectrometry, and scanning electron microscope equipped with energy dispersive X-ray analyser. A set of "in vivo" experiments demonstrated that additions of Hg2+ to the cultures from 10 to 25 µM Hg2+ stimulate an over secretion of PVDs suggesting that the toxic cation strongly reduces the availability of apo-PVDs, because the complex mercuric-pyoverdine is very stable at neutral pH, and hinder the formation of PVDs-Fe(III).
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242
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Evidence of mercury trapping in biofilm-EPS and mer operon-based volatilization of inorganic mercury in a marine bacterium Bacillus cereus BW-201B. Arch Microbiol 2016; 199:445-455. [DOI: 10.1007/s00203-016-1317-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2016] [Revised: 08/23/2016] [Accepted: 10/25/2016] [Indexed: 01/17/2023]
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243
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Geesey GG, Barkay T, King S. Microbes in mercury-enriched geothermal springs in western North America. THE SCIENCE OF THE TOTAL ENVIRONMENT 2016; 569-570:321-331. [PMID: 27344121 DOI: 10.1016/j.scitotenv.2016.06.080] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Revised: 06/11/2016] [Accepted: 06/12/2016] [Indexed: 06/06/2023]
Abstract
Because geothermal environments contain mercury (Hg) from natural sources, microorganisms that evolved in these systems have likely adapted to this element. Knowledge of the interactions between microorganisms and Hg in geothermal systems may assist in understanding the long-term evolution of microbial adaptation to Hg with relevance to other environments where Hg is introduced from anthropogenic sources. A number of microbiological studies with supporting geochemistry have been conducted in geothermal systems across western North America. Approximately 1 in 5 study sites include measurements of Hg. Of all prokaryotic taxa reported across sites with microbiological and accompanying physicochemical data, 42% have been detected at sites in which Hg was measured. Genes specifying Hg reduction and detoxification by microorganisms were detected in a number of hot springs across the region. Archaeal-like sequences, representing two crenarchaeal orders and one order each of the Euryarchaeota and Thaumarchaeota, dominated in metagenomes' MerA (the mercuric reductase protein) inventories, while bacterial homologs were mostly found in one deeply sequenced metagenome. MerA homologs were more frequently found in metagenomes of microbial communities in acidic springs than in circumneutral or high pH geothermal systems, possibly reflecting higher bioavailability of Hg under acidic conditions. MerA homologs were found in hot springs prokaryotic isolates affiliated with Bacteria and Archaea taxa. Acidic sites with high Hg concentrations contain more of Archaea than Bacteria taxa, while the reverse appears to be the case in circumneutral and high pH sites with high Hg concentrations. However, MerA was detected in only a small fraction of the Archaea and Bacteria taxa inhabiting sites containing Hg. Nevertheless, the presence of MerA homologs and their distribution patterns in systems, in which Hg has yet to be measured, demonstrates the potential for detoxification by Hg reduction in these geothermal systems, particularly the low pH springs that are dominated by Archaea.
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Affiliation(s)
- Gill G Geesey
- Department of Microbiology and Immunology, Thermal Biology Institute, Montana State University, Bozeman, MT 59717-3520, USA.
| | - Tamar Barkay
- Department of Biochemistry and Microbiology, Graduate Program in Ecology and Evolution, Rutgers University, New Brunswick, NJ 08901-8525, USA.
| | - Sue King
- 2908 3rd Avenue North, Great Falls, MT 59401, USA.
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244
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Mangal V, Zhu Y, Shi YX, Guéguen C. Assessing cadmium and vanadium accumulation using diffusive gradient in thin-films (DGT) and phytoplankton in the Churchill River estuary, Manitoba. CHEMOSPHERE 2016; 163:90-98. [PMID: 27521643 DOI: 10.1016/j.chemosphere.2016.08.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2016] [Revised: 07/15/2016] [Accepted: 08/01/2016] [Indexed: 06/06/2023]
Abstract
Diffusive gradient in thin films (DGT) and phytoplankton communities were evaluated for the measurement of Cd and V at environmentally relevant concentrations in laboratory settings and in the Churchill River estuary (Manitoba, Canada) during an annual spring melt. Despite rapid changes in hydrology and water quality, DGT samplers and intracellular Cd and V concentrations were positively correlated (0.79 < r(2) < 0.99), suggesting comparable accumulation trends between both DGT-labile and intracellular monitoring techniques. The largest accumulated concentrations of both Cd and V by DGT and phytoplankton accumulation methods were found later into the river discharge period. In controlled settings, accumulated Cd and V concentrations by the diatom Attheya septentrionalis displayed a strong correlation with metals accumulated by DGTs (r(2) > 0.99). Principal component analysis (PCA) reinforced similarities between both metal monitoring techniques and assessed how changing environmental variables during the river discharge period influenced each monitoring technique. Cd accumulation was influenced by DOC concentrations and protein-like DOM whereas ionic strength (i.e. conductivity) and humic-like DOM influenced V accumulation. The present findings suggest that (1) DGT is a versatile tool for monitoring bioaccumulation of Cd and V in highly dynamic environmental systems and (2) DOC concentration, DOM composition, conductivity, pH, and river discharge influence the bioavailability of Cd and V in estuarine and riverine waters.
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Affiliation(s)
- V Mangal
- Environmental and Life Sciences Graduate Program, Trent University, ON, Canada
| | - Y Zhu
- Environmental and Life Sciences Graduate Program, Trent University, ON, Canada
| | - Y X Shi
- Environmental and Life Sciences Graduate Program, Trent University, ON, Canada
| | - C Guéguen
- Chemistry Department, Trent University, ON, Canada.
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245
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Wang Y, Schaefer JK, Mishra B, Yee N. Intracellular Hg(0) Oxidation in Desulfovibrio desulfuricans ND132. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2016; 50:11049-11056. [PMID: 27654630 DOI: 10.1021/acs.est.6b03299] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The disposal of elemental mercury (Hg(0)) wastes in mining and manufacturing areas has caused serious soil and groundwater contamination issues. Under anoxic conditions, certain anaerobic bacteria can oxidize dissolved elemental mercury and convert the oxidized Hg to neurotoxic methylmercury. In this study, we conducted experiments with the Hg-methylating bacterium Desulfovibrio desulfuricans ND132 to elucidate the role of cellular thiols in anaerobic Hg(0) oxidation. The concentrations of cell-surface and intracellular thiols were measured, and specific fractions of D. desulfuricans ND132 were examined for Hg(0) oxidation activity and analyzed with extended X-ray absorption fine structure (EXAFS) spectroscopy. The experimental data indicate that intracellular thiol concentrations are approximately six times higher than those of the cell wall. Cells reacted with a thiol-blocking reagent were severely impaired in Hg(0) oxidation activity. Spheroplasts lacking cell walls rapidly oxidized Hg(0) to Hg(II), while cell wall fragments exhibited low reactivity toward Hg(0). EXAFS analysis of spheroplast samples revealed that multiple different forms of Hg-thiols are produced by the Hg(0) oxidation reaction and that the local coordination environment of the oxidized Hg changes with reaction time. The results of this study indicate that Hg(0) oxidation in D. desulfuricans ND132 is an intracellular process that occurs by reaction with thiol-containing molecules.
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Affiliation(s)
- Yuwei Wang
- Department of Environmental Sciences, Rutgers University , New Brunswick, New Jersey 08901, United States
| | - Jeffra K Schaefer
- Department of Environmental Sciences, Rutgers University , New Brunswick, New Jersey 08901, United States
| | - Bhoopesh Mishra
- Department of Physics, Illinois Institute of Technology , Chicago, Illinois 60616, United States
| | - Nathan Yee
- Department of Environmental Sciences, Rutgers University , New Brunswick, New Jersey 08901, United States
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246
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Eckley CS, Tate MT, Lin CJ, Gustin M, Dent S, Eagles-Smith C, Lutz MA, Wickland KP, Wang B, Gray JE, Edwards GC, Krabbenhoft DP, Smith DB. Surface-air mercury fluxes across Western North America: A synthesis of spatial trends and controlling variables. THE SCIENCE OF THE TOTAL ENVIRONMENT 2016; 568:651-665. [PMID: 26936663 DOI: 10.1016/j.scitotenv.2016.02.121] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Revised: 02/04/2016] [Accepted: 02/17/2016] [Indexed: 06/05/2023]
Abstract
Mercury (Hg) emission and deposition can occur to and from soils, and are an important component of the global atmospheric Hg budget. This paper focuses on synthesizing existing surface-air Hg flux data collected throughout the Western North American region and is part of a series of geographically focused Hg synthesis projects. A database of existing Hg flux data collected using the dynamic flux chamber (DFC) approach from almost a thousand locations was created for the Western North America region. Statistical analysis was performed on the data to identify the important variables controlling Hg fluxes and to allow spatiotemporal scaling. The results indicated that most of the variability in soil-air Hg fluxes could be explained by variations in soil-Hg concentrations, solar radiation, and soil moisture. This analysis also identified that variations in DFC methodological approaches were detectable among the field studies, with the chamber material and sampling flushing flow rate influencing the magnitude of calculated emissions. The spatiotemporal scaling of soil-air Hg fluxes identified that the largest emissions occurred from irrigated agricultural landscapes in California. Vegetation was shown to have a large impact on surface-air Hg fluxes due to both a reduction in solar radiation reaching the soil as well as from direct uptake of Hg in foliage. Despite high soil Hg emissions from some forested and other heavily vegetated regions, the net ecosystem flux (soil flux+vegetation uptake) was low. Conversely, sparsely vegetated regions showed larger net ecosystem emissions, which were similar in magnitude to atmospheric Hg deposition (except for the Mediterranean California region where soil emissions were higher). The net ecosystem flux results highlight the important role of landscape characteristics in effecting the balance between Hg sequestration and (re-)emission to the atmosphere.
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Affiliation(s)
- Chris S Eckley
- US Environmental Protection Agency, Region-10, Seattle, WA 98101, USA.
| | - Mike T Tate
- US Geological Survey, Middleton, WI 53562, USA
| | - Che-Jen Lin
- Center for Advances on Water and Air quality, Lamar University, Beaumont, TX 77710, USA
| | - Mae Gustin
- Department of Natural Resources & Environmental Science, University of Nevada, Reno, NV 89557, USA
| | | | | | | | | | | | | | - Grant C Edwards
- Department of Environment and Geography, Macquarie University, North Ryde, NSW 2109, Australia
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247
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Resistance of Permafrost and Modern Acinetobacter lwoffii Strains to Heavy Metals and Arsenic Revealed by Genome Analysis. BIOMED RESEARCH INTERNATIONAL 2016; 2016:3970831. [PMID: 27795957 PMCID: PMC5067307 DOI: 10.1155/2016/3970831] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Revised: 07/14/2016] [Accepted: 09/07/2016] [Indexed: 12/23/2022]
Abstract
We performed whole-genome sequencing of five permafrost strains of Acinetobacter lwoffii (frozen for 15–3000 thousand years) and analyzed their resistance genes found in plasmids and chromosomes. Four strains contained multiple plasmids (8–12), which varied significantly in size (from 4,135 to 287,630 bp) and genetic structure; the fifth strain contained only two plasmids. All large plasmids and some medium-size and small plasmids contained genes encoding resistance to various heavy metals, including mercury, cobalt, zinc, cadmium, copper, chromium, and arsenic compounds. Most resistance genes found in the ancient strains of A. lwoffii had their closely related counterparts in modern clinical A. lwoffii strains that were also located on plasmids. The vast majority of the chromosomal resistance determinants did not possess complete sets of the resistance genes or contained truncated genes. Comparative analysis of various A. lwoffii and of A. baumannii strains discovered a number of differences between them: (i) chromosome sizes in A. baumannii exceeded those in A. lwoffii by about 20%; (ii) on the contrary, the number of plasmids in A. lwoffii and their total size were much higher than those in A. baumannii; (iii) heavy metal resistance genes in the environmental A. lwoffii strains surpassed those in A. baumannii strains in the number and diversity and were predominantly located on plasmids. Possible reasons for these differences are discussed.
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248
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Hoque E, Fritscher J. A new mercury-accumulating Mucor hiemalis strain EH8 from cold sulfidic spring water biofilms. Microbiologyopen 2016; 5:763-781. [PMID: 27177603 PMCID: PMC5061714 DOI: 10.1002/mbo3.368] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Revised: 03/17/2016] [Accepted: 03/25/2016] [Indexed: 11/24/2022] Open
Abstract
Here, we report about a unique aquatic fungus Mucor hiemalisEH8 that can remove toxic ionic mercury from water by intracellular accumulation and reduction into elemental mercury (Hg0 ). EH8 was isolated from a microbial biofilm grown in sulfidic-reducing spring water sourced at a Marching's site located downhill from hop cultivation areas with a history of mercury use. A thorough biodiversity survey and mercury-removal function analyses were undertaken in an area of about 200 km2 in Bavaria (Germany) to find the key biofilm and microbe for mercury removal. After a systematic search using metal removal assays we identified Marching spring's biofilm out of 18 different sulfidic springs' biofilms as the only one that was capable of removing ionic Hg from water. EH8 was selected, due to its molecular biological identification as the key microorganism of this biofilm with the capability of mercury removal, and cultivated as a pure culture on solid and in liquid media to produce germinating sporangiospores. They removed 99% of mercury from water within 10-48 h after initial exposure to Hg(II). Scanning electron microscopy demonstrated occurrence of intracellular mercury in germinating sporangiospores exposed to mercury. Not only associated with intracellular components, but mercury was also found to be released and deposited as metallic-shiny nanospheres. Electron-dispersive x-ray analysis of such a nanosphere confirmed presence of mercury by the HgMα peak at 2.195 keV. Thus, a first aquatic eukaryotic microbe has been found that is able to grow even at low temperature under sulfur-reducing conditions with promising performance in mercury removal to safeguard our environment from mercury pollution.
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Affiliation(s)
- Enamul Hoque
- Helmholtz Zentrum München - German Research Center for Environmental Health, Institute of Groundwater Ecology, Ingolstädter Landstr.1, Neuherberg, 85764, Germany.
| | - Johannes Fritscher
- Helmholtz Zentrum München - German Research Center for Environmental Health, Institute of Groundwater Ecology, Ingolstädter Landstr.1, Neuherberg, 85764, Germany
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249
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Buck KA, Varian-Ramos CW, Cristol DA, Swaddle JP. Blood Mercury Levels of Zebra Finches Are Heritable: Implications for the Evolution of Mercury Resistance. PLoS One 2016; 11:e0162440. [PMID: 27668745 PMCID: PMC5036838 DOI: 10.1371/journal.pone.0162440] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Accepted: 08/23/2016] [Indexed: 11/18/2022] Open
Abstract
Mercury is a ubiquitous metal contaminant that negatively impacts reproduction of wildlife and has many other sub-lethal effects. Songbirds are sensitive bioindicators of mercury toxicity and may suffer population declines as a result of mercury pollution. Current predictions of mercury accumulation and biomagnification often overlook possible genetic variation in mercury uptake and elimination within species and the potential for evolution in affected populations. We conducted a study of dietary mercury exposure in a model songbird species, maintaining a breeding population of zebra finches (Taeniopygia guttata) on standardized diets ranging from 0.0-2.4 μg/g methylmercury. We applied a quantitative genetics approach to examine patterns of variation and heritability of mercury accumulation within dietary treatments using a method of mixed effects modeling known as the 'animal model'. Significant variation in blood mercury accumulation existed within each treatment for birds exposed at the same dietary level; moreover, this variation was highly repeatable for individuals. We observed substantial genetic variation in blood mercury accumulation for birds exposed at intermediate dietary concentrations. Taken together, this is evidence that genetic variation for factors affecting blood mercury accumulation could be acted on by selection. If similar heritability for mercury accumulation exists in wild populations, selection could result in genetic differentiation for populations in contaminated locations, with possible consequences for mercury biomagnification in food webs.
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Affiliation(s)
- Kenton A. Buck
- Institute for Integrative Bird Behavior Studies, College of William and Mary, Williamsburg, Virginia, United States of America
| | - Claire W. Varian-Ramos
- Biology Department, Colorado State University – Pueblo, Pueblo, Colorado, United States of America
| | - Daniel A. Cristol
- Institute for Integrative Bird Behavior Studies, College of William and Mary, Williamsburg, Virginia, United States of America
| | - John P. Swaddle
- Institute for Integrative Bird Behavior Studies, College of William and Mary, Williamsburg, Virginia, United States of America
- * E-mail:
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250
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Structural Analysis of the Hg(II)-Regulatory Protein Tn501 MerR from Pseudomonas aeruginosa. Sci Rep 2016; 6:33391. [PMID: 27641146 PMCID: PMC5027573 DOI: 10.1038/srep33391] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2016] [Accepted: 08/24/2016] [Indexed: 01/07/2023] Open
Abstract
The metalloprotein MerR is a mercury(II)-dependent transcriptional repressor-activator that responds to mercury(II) with extraordinary sensitivity and selectivity. It's widely distributed in both Gram-negative and Gram-positive bacteria but with barely detectable sequence identities between the two sources. To provide structural basis for the considerable biochemical and biophysical experiments previously performed on Tn501 and Tn21 MerR from Gram-negative bacteria, we analyzed the crystal structure of mercury(II)-bound Tn501 MerR. The structure in the metal-binding domain provides Tn501 MerR with a high affinity for mercury(II) and the ability to distinguish mercury(II) from other metals with its unique planar trigonal coordination geometry, which is adopted by both Gram-negative and Gram-positive bacteria. The mercury(II) coordination state in the C-terminal metal-binding domain is transmitted through the allosteric network across the dimer interface to the N-terminal DNA-binding domain. Together with the previous mutagenesis analyses, the present data indicate that the residues in the allosteric pathway have a central role in maintaining the functions of Tn501 MerR. In addition, the complex structure exhibits significant differences in tertiary and quaternary structural arrangements compared to those of Bacillus MerR from Gram-positive bacteria, which probably enable them to function with specific promoter DNA with different spacers between -35 and -10 elements.
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