Actions for Anaerobic Mercury Methylation and Demethylation by <i>Geobacter bemidjiensis<

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Anaerobic Mercury Methylation and Demethylation by <i>Geobacter bemidjiensis</i> Bem [electronic resource].

Published
Washington, D.C. : United States. Dept. of Energy. Office of Science, 2016.
Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy
Physical Description
pages 4,366-4,373 : digital, PDF file
Additional Creators
Oak Ridge National Laboratory, United States. Department of Energy. Office of Science, and United States. Department of Energy. Office of Scientific and Technical Information
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Summary
Two competing processes controlling the net production and bioaccumulation of neurotoxic methylmercury (MeHg) in natural ecosystems are microbial methylation and demethylation. Though mercury (Hg) methylation by anaerobic microorganisms and demethylation by aerobic Hg-resistant bacteria have both been extensively studied, little attention has been given to MeHg degradation by anaerobic bacteria, particularly the iron-reducing bacterium Geobacter bemidjensis Bem. Here we report, for the first time, that the strain G. bemidjensis Bem can methylate inorganic Hg and degrade MeHg concurrently under anoxic conditions. Our results suggest that G. bemidjensis cells utilize a reductive demethylation pathway to degrade MeHg, with elemental Hg(0) as the major reaction product, possibly due to the presence of homologs encoding both organo-mercurial lyase (MerB) and mercuric reductase (MerA) in this organism. In addition, the cells can mediate multiple reactions including Hg/MeHg sorption, Hg reduction and oxidation, resulting in both time and concentration dependent Hg species transformations. Moderate concentrations (10 500 M) of Hg-binding ligands such as cysteine enhance Hg(II) methylation but inhibit MeHg degradation. These findings indicate a cycle of methylation and demethylation among anaerobic bacteria and suggest that mer-mediated demethylation may play a role in the net balance of MeHg production in anoxic water and sediments.
Report Numbers
E 1.99:1319176
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Note
Published through SciTech Connect.
03/28/2016.
"KP1702030"
"ERKP723"
Environmental Science and Technology 50 8 ISSN 0013-936X AM
Xia Lu; Yurong Liu; Alexander Johs; Linduo Zhao; Tieshan Wang; Ziming Yang; Hui Lin; Dwayne A. Elias; Eric M. Pierce; Liyuan Liang; Tamar Barkay; Baohua Gu.
Funding Information
AC05-00OR22725
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