微生物还原Se(Ⅵ)和Se(Ⅳ)合成SeNPs机理研究新进展

Advances in understanding the mechanisms underlying microbial reduction of Se(Ⅵ) and Se(Ⅳ) to SeNPs

硒(Se)是自然界中重要的元素之一,微生物在硒的生物地球化学循环中发挥着至关重要的作用.细菌、真菌及放线菌等多种微生物能够通过同化还原、异化还原等途径将Se(VI)和Se(IV)还原为硒纳米粒子(Se NPs).本文综述了目前已知的能够还原Se(VI)和Se(IV)的微生物资源及其还原机理,并总结了在硒化合物转运、Se NPs尺寸控制和稳定等过程中发挥重要作用的蛋白质和酶.微生物对Se(VI)的还原主要通过硒酸盐还原酶实现,而对Se(IV)的还原则通过包括亚硫酸盐还原酶、亚硝酸盐还原酶、谷胱甘肽和谷胱甘肽还原酶、硫氧还蛋白和硫氧还蛋白还原酶等多种酶促还原途径、非酶促还原途径以及作为电子受体参与的细胞呼吸过程来实现.多种不同的蛋白质和酶在Se(VI)和Se(IV)的跨膜转运、Se NPs的尺寸控制、稳定及外排等过程中发挥着重要的作用,它们不仅控制着硒化合物的还原过程,也会对Se NPs进行修饰从而改变Se NPs的物理化学性质,影响硒在环境中的归趋.今后仍需要不断开发新的能够代谢硒化合物的微生物资源,并结合基因组学、转录组学、蛋白组学等多种组学手段对微生物转化硒化合物的关键基因和调控系统等进行深入解析.

Selenium （Se） is one of the most important elements in nature. Microorganisms play a crucial role in its biogeochemical cycling. There have been several reports on Se （VI） and Se （IV） reduction to Se nanoparticles （SeNPs） via microbial assimilation reduction, alienation reduction, and others pathways in bacteria, fungi, and actinomycetes. This paper reviews the microorganisms that can reduce Se （VI） and Se （IV）, the mechanisms by which they reduce Se, and proteins that may play roles in transporting Se compounds, controlling their particles sizes, and stabilizing SeNPs. Reduction of Se （VI） is mediated by selenate reductase, whereas the reduction of Se （VI） is mediated by enzymatic pathways such as sulfite reductase, nitrite reductase, glutathione and glutathione reductase, thioredoxin and thioredoxin reductase, nonenzymatic pathways, and cellular respiration using Se （VI） as electron acceptors. Some microbes use several pathways simultaneously. Many different enzymes and other proteins play important roles in the transport of Se compounds, control of particle sizes, and stabilization and efflux of SeNPs, which may change the physical and chemical properties of SeNPs by controlling the process of reducing Se compounds, thereby affect the fate of Se in the environment. Therefore, identifying new microbial resources and using multiple omics tools, including genomics, transcriptomics, and proteomics to analyze key genes and regulate systems related to the transformation of Se compounds will be important future research directions.