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Oxidation and methylation of dissolved elemental mercury by anaerobic bacteria

Nature Geoscience volume 6, pages 751–754 (2013)Cite this article

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Abstract

Methylmercury is a neurotoxin that poses significant health risks to humans. Some anaerobic sulphate- and iron-reducing bacteria can methylate oxidized forms of mercury, generating methylmercury1,2,3,4. One strain of sulphate-reducing bacteria (Desulfovibrio desulphuricans ND132) can also methylate elemental mercury5. The prevalence of this trait among different bacterial strains and species remains unclear, however. Here, we compare the ability of two strains of the sulphate-reducing bacterium Desulfovibrio and one strain of the iron-reducing bacterium Geobacter to oxidize and methylate elemental mercury in a series of laboratory incubations. Experiments were carried out under dark, anaerobic conditions, in the presence of environmentally relevant concentrations of elemental mercury. We report differences in the ability of these organisms to oxidize and methylate elemental mercury. In line with recent findings5, we show that D. desulphuricans ND132 can both oxidize and methylate elemental mercury. We find that the rate of methylation of elemental mercury is about one-third the rate of methylation of oxidized mercury. We also show that Desulfovibrio alaskensis G20 can oxidize, but not methylate, elemental mercury. Geobacter sulphurreducens PCA is able to oxidize and methylate elemental mercury in the presence of cysteine. We suggest that the activity of methylating and non-methylating bacteria may together enhance the formation of methylmercury in anaerobic environments.

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Figure 1: Anaerobic bacterial oxidation of dissolved elemental Hg(0) in PBS.
Figure 2: Hg(0) or Hg(II) as the sole source of Hg for bacterial methylation in PBS.

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Acknowledgements

We thank X. Yin, Y. Qian, R. Jr Hurt and M. Drake at Oak Ridge National Laboratory (ORNL) and H. Guo at the University of Tennessee for technical assistance and support. This research was sponsored by the Office of Biological and Environmental Research, Office of Science, US Department of Energy (DOE) as part of the Mercury Science Focus Area Program at ORNL, which is managed by UT-Battelle LLC for the DOE under contract DE-AC05-00OR22725.

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Authors and Affiliations

  1. Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA

    Haiyan Hu, Hui Lin, Wang Zheng, Stephen J. Tomanicek, Alexander Johs, Liyuan Liang & Baohua Gu

  2. State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China

    Haiyan Hu & Xinbin Feng

  3. Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA

    Dwayne A. Elias

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Contributions

H.H. and H.L. designed and carried out the experiments; B.G. conceived the study and supervised the research; W.Z., S.J.T. and X.F. contributed experiments and analytic tools; B.G., A.J., D.A.E. and L.L. contributed data analysis and wrote the paper.

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Correspondence to Baohua Gu.

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The authors declare no competing financial interests.

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Hu, H., Lin, H., Zheng, W. et al. Oxidation and methylation of dissolved elemental mercury by anaerobic bacteria. Nature Geosci 6, 751–754 (2013). https://doi.org/10.1038/ngeo1894

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