For the first time, we found that the strain Geobacter bemidjiensis Bem can methylate mercury and degrade methylmercury toxin concurrently under anoxic conditions. A reductive demethylation pathway is utilized by Bem to degrade methylmercury, possibly due to its genes encoding homologs of a organomercurial lyase (MerB) and a mercuric reductase (MerA).
Geobacter bemidjiensis bacteria widely occur in sediments and water, including permafrost soils, and may thus play an important role in controlling net methylmercury production and bioaccumulation in biota in natural aquatic environments.
Microbial methylation and demethylation are two competing processes controlling the net production and bioaccumulation of neurotoxic methylmercury in natural aquatic ecosystems. Although mercury methylation by anaerobic microorganisms and demethylation by aerobic Hg-resistant bacteria have both been extensively studied, little attention has been given to MeHg degradation by anaerobic bacteria, particularly the iron-reducing bacterium Geobacter bemidjiensis Bem.
Lu, Xia, Yurong Liu, Alexander Johs, Linduo Zhao, Tieshan Wang, Ziming Yang, Hui Lin, Dwayne A. Elias, Eric M. Pierce, Liyuan Liang, Tamar Barkay, and Baohua Gu. 2016. “Anaerobic Mercury Methylation and Demethylation by Geobacter bemidjiensis Bem.” Environmental Science & Technology. DOI: 10.1021/acs.est.6b00401