微生物铬转化和抗性机制与生物修复研究进展

Research progress in microbial chromium-transformation and resistance and bioremediation

摘要:

铬(Chromium，Cr)是过渡金属元素，在自然界中以六价[CrO42?，Cr2O72?，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。

Abstract:

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.