Multiple Species of Bacteria Convert Elemental Mercury to Toxic Methylmercury

New insights could assist in cleanup of contaminated environments.

Image courtesy of Napat Chaichanasiri under a Creative Commons license.
Researchers are studying how bacteria transform mercury into a toxic form in the environment that can accumulate in the food web, posing a threat to wildlife and people.

The Science

Methylmercury is a known neurotoxin that poses a significant health risk to humans. A number of anaerobic bacterial species methylate oxidized mercury to methylmercury in the environment, but until now, only one species has been shown to methylate elemental mercury. Research by Oak Ridge National Laboratory scientists indicates that multiple bacterial species can methylate elemental mercury.

The Impact

This more complete understanding of the variety of microbial processes involved in mercury cycling clarifies the challenges associated with cleaning up mercury-contaminated water and sediments.


Because elemental mercury has been considered to be relatively inert and is volatile, remediation approaches have focused on converting toxic forms of mercury into elemental mercury that would then bubble out of surface water and dissipate. In this study, researchers found that some bacterial species can both oxidize and methylate elemental mercury, others require the presence of a specific amino acid to perform these conversions, and still others can only oxidize elemental mercury. These findings suggest that both methylating and nonmethylating bacteria can enhance the formation of toxic methylmercury in anaerobic environments.


Baohua Gu
Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830


This research was sponsored by the Office of Biological and Environmental Research within the U.S. Department of Energy’s (DOE) Office of Science as part of the Mercury Science Focus Area program at Oak Ridge National Laboratory, which is managed by UT-Battelle LLC for DOE under contract DE-AC05-00OR22725.


Hu, H., et al. “Oxidation and methylation of dissolved elemental mercury by anaerobic bacteria,” Nature Geosci. 6, 751–754 (2013). [DOI: 10.1038/NGEO1894].

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