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Environmental formation of methylmercury is controlled by synergy of inorganic mercury bioavailability and microbial mercury-methylation capacity |
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| Authors: | Benjamin D. Peterson David P. Krabbenhoft Katherine D. McMahon Jacob M. Ogorek Michael T. Tate William H. Orem Brett A. Poulin |
| Affiliation: | 1. Department of Bacteriology, University of Wisconsin–Madison, Madison, Wisconsin, USA;2. Upper Midwest Water Science Center, Mercury Research Laboratory, U.S. Geological Survey, Madison, Wisconsin, USA Contribution: Conceptualization (lead), Data curation (lead), Formal analysis (equal), Funding acquisition (lead), Investigation (equal), Methodology (lead), Resources (equal), Supervision (equal), Validation (equal), Writing - original draft (equal), Writing - review & editing (equal);3. Upper Midwest Water Science Center, Mercury Research Laboratory, U.S. Geological Survey, Madison, Wisconsin, USA Contribution: Data curation (equal), Formal analysis (equal), Methodology (equal), Resources (equal), Supervision (equal), Validation (equal);4. Upper Midwest Water Science Center, Mercury Research Laboratory, U.S. Geological Survey, Madison, Wisconsin, USA Contribution: Data curation (equal), Formal analysis (equal), Investigation (equal), Methodology (equal), Validation (equal);5. Geology Energy & Minerals Science Center, U.S. Geological Survey, Reston, Virginia, USA Contribution: Funding acquisition (supporting), Investigation (supporting), Methodology (supporting), Resources (supporting), Writing - review & editing (supporting);6. Department of Environmental Toxicology, University of California–Davis, Davis, California, USA |
| Abstract: | Methylmercury (MeHg) production is controlled by the bioavailability of inorganic divalent mercury (Hg(II)i) and Hg-methylation capacity of the microbial community (conferred by the hgcAB gene cluster). However, the relative importance of these factors and their interaction in the environment remain poorly understood. Here, metagenomic sequencing and a full-factorial MeHg formation experiment were conducted across a wetland sulfate gradient with different microbial communities and pore water chemistries. From this experiment, the relative importance of each factor on MeHg formation was isolated. Hg(II)i bioavailability correlated with the dissolved organic matter composition, while the microbial Hg-methylation capacity correlated with the abundance of hgcA genes. MeHg formation responded synergistically to both factors. Notably, hgcA sequences were from diverse taxonomic groups, none of which contained genes for dissimilatory sulfate reduction. This work expands our understanding of the geochemical and microbial constraints on MeHg formation in situ and provides an experimental framework for further mechanistic studies. |
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