汞在微生物中的跨膜运输机制研究进展

Transmembrane transport of inorganic mercury in microorganisms- A review

甲基汞是一种强亲脂性、高神经毒性的有机汞化合物,可以通过生物富集或生物放大造成人类甲基汞暴露。环境中甲基汞的产生主要是厌氧微生物所调控的无机汞的甲基化。主流观点认为厌氧微生物对汞的甲基化是一种细胞内反应,因此,甲基汞的产生速率不仅与环境中具有汞甲基化能力的厌氧微生物的存在与活性相关,同时也与无机汞在微生物细胞中的跨膜运输过程有着重要联系。要明确无机汞经微生物甲基化的机制,就必须了解无机汞被微生物细胞生物吸收的过程,即无机汞在微生物中的跨膜运输路径。目前研究认为该过程主要有Mer抗汞操纵子转运体系、被动扩散、促进扩散和主动运输4种路径。本综述主要围绕无机汞被微生物细胞生物吸收的这4种路径展开,将系统介绍科学界对这4种路径的最新研究进展,并对相关研究进行展望,指出无机汞经促进扩散或主动运输进入到微生物细胞内将是未来研究的重点。

Methylmercury( CH3Hg+,or MeHg) is the most poisonous form of mercury( Hg) because it can enter into human bodies through the consumption of Hg-contaminated fish and shellfish. A first step toward bioaccumulation of MeHg in aquatic foods is the methylation of inorganic mercury,a process that is predominantly mediated by anaerobic bacteria,such as sulfate reducing bacteria and iron reducing bacteria. Many researches have confirmed that microbial methylation of mercury is an intracellular reaction. Therefore,MeHg production rates are not only related to the presence and productivity of methylating bacteria and also the biouptake of Hg to these anaerobic bacteria. To understand the pathways of Hg biouptake is indispensable to elucidate the mechanisms of microbial methylation. In this review,we systematically evaluated the current state of knowledge regarding the four pathways of mercury biouptake,Mer-based transport system,passive diffusion,facilitated diffusion and active transport. In the future,facilitated diffusion and active transport of inorganic mercury to the cytoplasm of microbial cells should be emphasized.