微生物铬转化和抗性机制与生物修复研究进展

铬(Chromium,Cr)是过渡金属元素,在自然界中以六价CrO_4~(2-),Cr_2O_7~(2-),Cr(Ⅵ)]和三价Cr(OH)_3,Cr(Ⅲ)]为主。很多微生物在长期铬胁迫的条件下,进化出了一系列铬转化和抗性机制。微生物对铬的转化包括Cr(Ⅵ)的还原和Cr(Ⅲ)的氧化。微生物的Cr(Ⅵ)还原可以将毒性强的六价铬转化为毒性弱或无毒的三价铬,这类微生物有较强的土壤和水体铬污染治理潜力。Cr(Ⅲ)的氧化也在铬的生物地球化学循环过程中起着至关重要的作用。除了Cr(Ⅵ)的还原,微生物对铬的抗性机制还有:(1)减少摄入;(2)外排;(3)清除胞内氧化压力;(4)DNA修复。本文主要介绍微生物的铬转化和抗性机制,以及其在铬污染生物修复中应用的最新研究进展。

Research progress in microbial chromium-transformation and resistance and bioremediation

Chromium is a transitional metal mainly existing as hexavalent CrO42?, Cr2O72?, Cr(VI)] and trivalent Cr(OH)3, Cr(III)] forms in the natural environment. Several microorganisms have evolved various transformation and resistant mechanisms for chromium detoxification to resist the poisonous chromium. Microbial chromium-transformation contain Cr(VI) reduction and Cr(III) oxidation. Chromate-reducing microbes can transform high toxic Cr(VI) to low or non-toxic Cr(III). These microbes show a big potential to bioremediate chromium-contaminated soil and water. In addition, various microbes have been reported to participate in Cr(III) oxidation. These microorganisms play a key role in the chromium transformation and biogeochemical cycle. So far, four microbial chromium-resistant mechanisms have been found including: (1) reducing the uptake of Cr(VI); (2) Cr(VI) efflux; (3) removing intracellular oxidative stress; and (4) DNA repair. This review mainly focuses on summarizing the molecular mechanisms and new research progress in chromate transformation and bioremediation of chromium contamination by microorganisms.