Du Hongxia, Ma Ming, Igarashi Yasuo, Wang Dingyong
College of Resources and Environment, Southwest University, Chongqing, 400715, China.
Chongqing Key Laboratory of Bio-Resource for Bioenergy, Southwest University, Chongqing, 400715, China.
Bull Environ Contam Toxicol. 2019 May;102(5):605-611. doi: 10.1007/s00128-018-2530-2. Epub 2019 Jan 2.
Mercury (Hg) methylation and demethylation is supposed to simultaneously exist in the environment and form a cycle, which determines the net production of methylmercury (MeHg). Exploring the mechanisms of MeHg formation and degradation, and its final fate in the natural environment is essential to understanding the biogeochemical cycle of Hg. However, MeHg demethylation has been less studied in the past years comparing with Hg methylation, particularly in anaerobic microorganisms whose demethylation role has been under-evaluated. This review described the current state of knowledge on biotic (microorganisms) and abiotic demethylation (photodegradation, chemical degradation) of MeHg. The decomposition of MeHg performed by microorganisms has been identified as two different pathways, reductive demethylation (RD) and oxidative demethylation (OD). Anaerobic and aerobic microorganisms involved in the process of RD and OD, influencing factors as well as research background and histories are systematically described in this review. It is predicted that the photodegradation mechanism, as well as anaerobic microorganisms involved in MeHg formation and degradation cycle will be the focus of future research.
汞（Hg）的甲基化和去甲基化被认为在环境中同时存在并形成一个循环，这决定了甲基汞（MeHg）的净产量。探索甲基汞的形成和降解机制及其在自然环境中的最终归宿对于理解汞的生物地球化学循环至关重要。然而，与汞的甲基化相比，过去几年对甲基汞去甲基化的研究较少，特别是在厌氧微生物中，其去甲基化作用一直未得到充分评估。本综述描述了目前关于甲基汞生物（微生物）和非生物去甲基化（光降解、化学降解）的知识状态。微生物对甲基汞的分解已被确定为两种不同的途径，即还原去甲基化（RD）和氧化去甲基化（OD）。本综述系统地描述了参与RD和OD过程的厌氧和好氧微生物、影响因素以及研究背景和历史。预计光降解机制以及参与甲基汞形成和降解循环的厌氧微生物将成为未来研究的重点。
