Mercury Methylation by Novel Microorganisms from New Environments

Microbial mercury (Hg) methylation transforms a toxic trace metal into the highly bioaccumulated neurotoxin methylmercury (MeHg). The lack of a genetic marker for microbial MeHg production has prevented a clear understanding of Hg-methylating organism distribution in nature. Recently, a specific gen...

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Bibliographic Details
Published in:Environmental science & technology 2013-10, Vol.47 (20), p.11810-11820
Main Authors: Gilmour, Cynthia C, Podar, Mircea, Bullock, Allyson L, Graham, Andrew M, Brown, Steven D, Somenahally, Anil C, Johs, Alex, Hurt, Richard A, Bailey, Kathryn L, Elias, Dwayne A
Format: Article
Language:English
Subjects:
Bacteria
Bacteria - growth & development
Bacteria - metabolism
Bacteriology
Batch Cell Culture Techniques
Biodegradation, Environmental
Biodiversity
Biological and medical sciences
Biotechnology
Ecosystem
Environmental Microbiology
Firmicutes
Fundamental and applied biological sciences. Psychology
Genes, Bacterial
Genomes
Habitats
Hg
Hg SFA
Mercury
Mercury - metabolism
Methylation
Microbiology
Microorganisms
Miscellaneous
Multigene Family
Oryza sativa
Phylogenetics
Phylogeny
Salinity
Species Specificity
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Summary:Microbial mercury (Hg) methylation transforms a toxic trace metal into the highly bioaccumulated neurotoxin methylmercury (MeHg). The lack of a genetic marker for microbial MeHg production has prevented a clear understanding of Hg-methylating organism distribution in nature. Recently, a specific gene cluster (hgcAB) was linked to Hg methylation in two bacteria. Here we test if the presence of hgcAB orthologues is a reliable predictor of Hg methylation capability in microorganisms, a necessary confirmation for the development of molecular probes for Hg-methylation in nature. Although hgcAB orthologues are rare among all available microbial genomes, organisms are much more phylogenetically and environmentally diverse than previously thought. By directly measuring MeHg production in several bacterial and archaeal strains encoding hgcAB, we confirmed that possessing hgcAB predicts Hg methylation capability. For the first time, we demonstrated Hg methylation in a number of species other than sulfate- (SRB) and iron- (FeRB) reducing bacteria, including methanogens, and syntrophic, acetogenic, and fermentative Firmicutes. Several of these species occupy novel environmental niches for Hg methylation, including methanogenic habitats such as rice paddies, the animal gut, and extremes of pH and salinity. Identification of these organisms as Hg methylators now links methylation to discrete gene markers in microbial communities.
ISSN:0013-936X
1520-5851
DOI:10.1021/es403075t