Bravo Andrea G, Cosio Claudia
Department of Marine Biology and Oceanography, Institute of Marine Sciences Spanish National Research Council (CSIC) Barcelona Spain.
Université de Reims Champagne Ardennes, UMR-I 02 INERIS-URCA-ULH SEBIO, Unité Stress Environnementaux et BIOsurveillance des milieux aquatiques Reims France.
Limnol Oceanogr. 2020 May;65(5):1010-1027. doi: 10.1002/lno.11366. Epub 2019 Nov 12.
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 (Hg) to MMHg to occur under oxygen-limited conditions and to depend on the activity of anaerobic microorganisms. Recent studies identified the gene cluster in microorganisms with the capacity to methylate Hg 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 Hg-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 Hg methylation is a bio-physico-chemical conundrum in which the efficiency of biological Hg methylation appears to depend chiefly on Hg 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.
汞（Hg）是一种天然且广泛存在的痕量金属，但因其通过鱼类消费导致人类接触甲基汞（MMHg），故而被视为优先污染物，尤其是其有机形态甲基汞。开创性研究表明，二价汞（Hg）在缺氧条件下会甲基化为MMHg，且这一过程依赖于厌氧微生物的活性。近期研究确定了微生物中具有汞甲基化能力的基因簇，并揭示了产生MMHg的物种范围和环境条件比之前预期的要广泛得多。在此，我们回顾了用于理解汞甲基化、参与这些过程的微生物生物多样性和活性的最新知识与方法，并强调了当前预测环境中MMHg浓度的局限性。现有数据揭示了这样一个事实，即汞甲基化是一个生物物理化学难题，其中生物汞甲基化的效率似乎主要取决于汞和养分的可利用性、诸如硫酸盐或铁等电子受体的丰度、有机物质的丰度和组成以及微生物群落的活性和结构。为预测不同环境中MMHg浓度的变化，有必要进一步了解微生物群落组成、物理化学条件、MMHg产生与去甲基化之间的关系。
