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Title: Contrasting Effects of Dissolved Organic Matter on Mercury Methylation by G. sulfurreducens PCA and D. desulfuricans ND132

Natural dissolved organic matter (DOM) affects mercury (Hg) redox reactions and anaerobic microbial Hg methylation in the environment. Several studies have shown that DOM can enhance Hg methylation, especially under sulfidic conditions, whereas others show that DOM inhibits Hg methylation due to strong Hg-DOM complexation. Here, we investigated and compared the effects of DOM on Hg methylation by an iron-reducing bacterium Geobacter sulfurreducens PCA and a sulfate-reducing bacterium Desulfovibrio desulfuricans ND132 under non-sulfidic conditions. The methylation experiment was performed with washed cells either in the absence or presence of DOM or glutathione, both of which form strong complexes with Hg via thiol-functional groups. DOM was found to greatly inhibit Hg methylation by G. Sulfurreducens PCA but enhance Hg methylation by D. desulfuricans ND132 cells with increasing DOM concentration. Furthermore, these strain-dependent opposing effects of DOM were also observed with glutathione, suggesting that thiols in DOM likely played an essential role in affecting cell Hg uptake and methylation. Additionally, DOM and glutathione decreased Hg sorption by G. sulfurreducens PCA, but not by D. desulfuricans ND132 cells, demonstrating that ND132 has a higher affinity to sorb or take up Hg than the PCA strain. Finally, these observations indicate that DOM effects onmore » Hg methylation are bacterial strain specific, depend on the DOM:Hg ratio or site-specific conditions, and may thus offer new insights into the role of DOM in methylmercury production in the environment.« less
Authors:
ORCiD logo [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Grant/Contract Number:
AC05-00OR22725
Type:
Published Article
Journal Name:
Environmental Science and Technology
Additional Journal Information:
Journal Volume: 51; Journal Issue: 18; Journal ID: ISSN 0013-936X
Publisher:
American Chemical Society (ACS)
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES
OSTI Identifier:
1377645
Alternate Identifier(s):
OSTI ID: 1376646

Zhao, Linduo, Chen, Hongmei, Lu, Xia, Lin, Hui, Christensen, Geoff A., Pierce, Eric M., and Gu, Baohua. Contrasting Effects of Dissolved Organic Matter on Mercury Methylation by G. sulfurreducens PCA and D. desulfuricans ND132. United States: N. p., Web. doi:10.1021/acs.est.7b02518.
Zhao, Linduo, Chen, Hongmei, Lu, Xia, Lin, Hui, Christensen, Geoff A., Pierce, Eric M., & Gu, Baohua. Contrasting Effects of Dissolved Organic Matter on Mercury Methylation by G. sulfurreducens PCA and D. desulfuricans ND132. United States. doi:10.1021/acs.est.7b02518.
Zhao, Linduo, Chen, Hongmei, Lu, Xia, Lin, Hui, Christensen, Geoff A., Pierce, Eric M., and Gu, Baohua. 2017. "Contrasting Effects of Dissolved Organic Matter on Mercury Methylation by G. sulfurreducens PCA and D. desulfuricans ND132". United States. doi:10.1021/acs.est.7b02518.
@article{osti_1377645,
title = {Contrasting Effects of Dissolved Organic Matter on Mercury Methylation by G. sulfurreducens PCA and D. desulfuricans ND132},
author = {Zhao, Linduo and Chen, Hongmei and Lu, Xia and Lin, Hui and Christensen, Geoff A. and Pierce, Eric M. and Gu, Baohua},
abstractNote = {Natural dissolved organic matter (DOM) affects mercury (Hg) redox reactions and anaerobic microbial Hg methylation in the environment. Several studies have shown that DOM can enhance Hg methylation, especially under sulfidic conditions, whereas others show that DOM inhibits Hg methylation due to strong Hg-DOM complexation. Here, we investigated and compared the effects of DOM on Hg methylation by an iron-reducing bacterium Geobacter sulfurreducens PCA and a sulfate-reducing bacterium Desulfovibrio desulfuricans ND132 under non-sulfidic conditions. The methylation experiment was performed with washed cells either in the absence or presence of DOM or glutathione, both of which form strong complexes with Hg via thiol-functional groups. DOM was found to greatly inhibit Hg methylation by G. Sulfurreducens PCA but enhance Hg methylation by D. desulfuricans ND132 cells with increasing DOM concentration. Furthermore, these strain-dependent opposing effects of DOM were also observed with glutathione, suggesting that thiols in DOM likely played an essential role in affecting cell Hg uptake and methylation. Additionally, DOM and glutathione decreased Hg sorption by G. sulfurreducens PCA, but not by D. desulfuricans ND132 cells, demonstrating that ND132 has a higher affinity to sorb or take up Hg than the PCA strain. Finally, these observations indicate that DOM effects on Hg methylation are bacterial strain specific, depend on the DOM:Hg ratio or site-specific conditions, and may thus offer new insights into the role of DOM in methylmercury production in the environment.},
doi = {10.1021/acs.est.7b02518},
journal = {Environmental Science and Technology},
number = 18,
volume = 51,
place = {United States},
year = {2017},
month = {8}
}