Mystery of Mercury Methlyation Unlocked

Researchers reveal that microorganisms are responsible for transforming mercury into methylmercury, a highly toxic form of mercury, in streams.

Image courtesy of Dar et al. (2008) Applied Microbiology and Biotechnology 78: 1045-1055 DOI 10.1007/s00253-008-1391-8
Whole-cell hybridization fluorescent image of bacteria from an anaerobic bioreactor identified by probes specific for deltaproteobacteria (green) or genus Sporomusa (red).

The Science

Microbial communities were examined in surface stream sediments at five contaminated sites and one control site near Oak Ridge, Tennessee to identify bacteria that could be contributing to mercury (Hg) methylation.

The Impact

The results of the present study allowed for the identification of bacteria that may contribute to Hg methylation in stream sediments.


Mercury has become a global pollutant due to its release into the atmosphere during coal burning, and into freshwater systems as part of agricultural runoff and direct industrial discharge. Once in freshwater systems, specific types of microorganisms are known to transform mercury into methylmercury (MeHg), a highly toxic form of mercury. Scientists from Oak Ridge National Laboratory (ORNL) recently examined the microbial communities from the sediments of six different surface streams in Oak Ridge, Tennessee to identify bacteria that could be contributing to MeHg production. Using 16S rRNA pyrosequencing, the researchers correlated the presence of a group of known MeHg producers, the Deltaproteobacteria, with MeHg in all of the Hg contaminated streams. Within the Deltaproteobacteria group, Desulfobulbus species are considered to be prime candidates for being involved in Hg methylation in these streams.


Dr. Anthony Palumbo
Oak Ridge National Laboratory


Basic Research: DOE Office of Science, Office of Biological and Environmental Research


Mosher, J. J., T. A. Vishnivetskaya, D. A. Elias, M. Podar, S. C. Brooks, S. D. Brown, C. C. Brandt and A. V. Palumbo. In press. “Characterization of the Deltaproteobacteria in Contaminated and Uncontaminated Surface Stream Sediments and Identification of Potential Mercury Methylators.” Aquatic Microbial Ecology. Vol. 66: 271–282, 2012. doi: 10.3354/ame01563

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