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METHYLMERCURY UPTAKE AND DEGRADATION BY METHANOTROPHS
Lu, X., W. Gu, L. Zhao, M.F. Ul Haque, A.A. DiSpirito, J.D. Semrau, and B. Gu.
Science Advances 3(5):Paper e1700041(2017)

Methylmercury (MeHg) is a potent neurotoxin produced by certain anaerobic microorganisms in natural environments. Although numerous studies have characterized the basis of Hg methylation, no studies have examined MeHg degradation by methanotrophs, despite their ubiquitous presence in the environment. Researchers found that some methanotrophs, such as Methylosinus trichosporium OB3b, can take up and degrade MeHg rapidly, whereas others, such as Methylococcus capsulatus Bath, can take up but not degrade MeHg. Demethylation by M. trichosporium OB3b increased with increasing MeHg concentrations but was abolished in mutants deficient in the synthesis of methanobactin, a metal-binding compound used by some methanotrophs, such as M. trichosporium OB3b. Furthermore, addition of methanol (>5 mM) as a competing one-carbon substrate inhibits demethylation, suggesting that MeHg degradation by methanotrophs might involve an initial bonding of MeHg by methanobactin, followed by cleavage of the C-Hg bond in MeHg by the methanol dehydrogenase. This new demethylation pathway by methanotrophs indicates possible broader involvement of C-metabolizing aerobes in the degradation and cycling of toxic MeHg in the environment. http://advances.sciencemag.org/content/advances/3/5/e1700041.full.pdf



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