Biotic formation of methylmercury A bio–physico–chemical conundrum

Mercury (Hg) is a natural and widespread trace metal, but is considered a priority pollutant, particularly its organic form methylmercury (MMHg), because of human’s exposure to MMHg through fish consumption. Pioneering studies showed the methylation of divalent Hg (HgII) to MMHg to occur under oxyge...

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Published inLimnology and oceanography Vol. 65; no. 5; pp. 1010 - 1027
Main Authors Bravo, Andrea G., Cosio, Claudia
Format Journal Article
LanguageEnglish
Published Hoboken, USA John Wiley and Sons, Inc 01.05.2020
John Wiley & Sons, Inc
Association for the Sciences of Limnology and Oceanography
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Summary:Mercury (Hg) is a natural and widespread trace metal, but is considered a priority pollutant, particularly its organic form methylmercury (MMHg), because of human’s exposure to MMHg through fish consumption. Pioneering studies showed the methylation of divalent Hg (HgII) to MMHg to occur under oxygen-limited conditions and to depend on the activity of anaerobic microorganisms. Recent studies identified the hgcAB gene cluster in microorganisms with the capacity to methylate HgII and unveiled a much wider range of species and environmental conditions producing MMHg than previously expected. Here, we review the recent knowledge and approaches used to understand HgII-methylation, microbial biodiversity and activity involved in these processes, and we highlight the current limits for predicting MMHg concentrations in the environment. The available data unveil the fact that HgII methylation is a bio-physico-chemical conundrum in which the efficiency of biological HgII methylation appears to depend chiefly on HgII and nutrients availability, the abundance of electron acceptors such as sulfate or iron, the abundance and composition of organic matter as well as the activity and structure of the microbial community. An increased knowledge of the relationship between microbial community composition, physico-chemical conditions, MMHg production, and demethylation is necessary to predict variability in MMHg concentrations across environments.
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Author Contribution Statement: The two authors have equally contributed to this work.
Associate editor: Vanessa Hatje
ISSN:0024-3590
1939-5590
DOI:10.1002/lno.11366