Methylmercury uptake and degradation by methanotrophs

by Xia Lu, Linduo Zhao, Baohua Gu, et al.


An ORNL-led team along with University of Michigan and Iowa State University investigated many different methanotrophs to single out how and which ones take up and break down methylmercury. Image by Jeremy Semrau, University of Michigan.


Methylmercury (CH3Hg+) is a potent neurotoxin produced by certain anaerobic microorganisms in natural environments. Although numerous studies have characterized the basis of mercury (Hg) methylation, no studies have examined CH3Hg+ degradation by methanotrophs, despite their ubiquitous presence in the environment. We report that some methanotrophs, such as Methylosinus trichosporium OB3b, can take up and degrade CH3Hg+ rapidly, whereas others, such as Methylococcus capsulatus Bath, can take up but not degrade CH3Hg+. Demethylation by M. trichosporium OB3b increases with increasing CH3Hg+ concentrations but was abolished in mutants deficient in the synthesis of methanobactin, ametal-binding compound used by some methanotrophs, such as M. trichosporium OB3b. Furthermore, addition of methanol (>5 mM) as a competing one-carbon (C1) substrate inhibits demethylation, suggesting that CH3Hg+ degradation bymethanotrophs may involve an initial bonding of CH3Hg+ by methanobactin followed by cleavage of the C–Hg bond in CH3Hg+ by themethanol dehydrogenase. This new demethylation pathway bymethanotrophs indicates possible broader involvement of C1-metabolizing aerobes in the degradation and cycling of toxic CH3Hg+ in the environment.

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Publication Citation

Science Advances 2017 3, e1700041 (2017) May 31, 2017
DOI: 10.1126/sciadv.1700041