Multiple Species of Bacteria Convert Elemental Mercury to Toxic Methylmercury
Methylmercury is a known neurotoxin that poses a significant health risk to humans. A number of anaerobic bacterial species methylate oxidized mercury to methylmercury, but only one species has been shown to methylate elemental mercury. 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. Now, scientists from Oak Ridge National Laboratory report that multiple species of bacteria can methylate elemental mercury. Moreover, some 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 non-methylating bacteria can enhance the formation of methylmercury in anaerobic environments. A 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.
Hu, H., H. Lin, W. Zheng, S. J. Tomanicek, A. Johs, X. Feng, D. A. Elias, L. Liang, and B. Gu. 2013. “Oxidation and Methylation of Dissolved Elemental Mercury by Anaerobic Bacteria,” Nature Geoscience 6, 751–54. DOI: 10.1038/NGEO1894.