微生物介导的铁氧化机制及应用研究进展

Advances in Microbial Iron Oxidation and Its Application

微生物介导的铁氧化过程是铁循环的重要组成部分。参与铁氧化过程的微生物主要是细菌和古菌,依据生长环境及电子受体情况可将其分为四类:嗜酸铁氧化菌、中性微氧铁氧化菌、中性厌氧光合铁氧化菌和中性厌氧硝酸盐还原铁氧化菌。铁氧化微生物驱动着环境中C、N、O、S等生源要素的元素地球化学循环。目前已经阐明的微生物铁氧化电子传递机制都有着一个共同范式,即亚铁都是在外膜细胞色素上被氧化,细胞从亚铁获得电子,由细胞外膜经周质电子传递蛋白,而后传递至细胞内膜各蛋白上,用于电子受体还原或固碳。现代环境中铁氧化微生物的研究已被广泛运用于地球早期生命演化研究、环境污染修复、新材料合成及生物浸矿等领域。铁氧化菌的分离鉴定、铁氧化代谢途径及其地球化学效应的详细解析及铁氧化在环境污染治理等方面还有大量的工作有待开展。

Iron ranks fourth in abundance among crustal elements and can be taken up by microbial assimilation as a biologically essential element or as an electron source in microbial metabolism.Microbially mediated iron oxidation is an important part of the iron cycle and thus drives the biogeochemical cycling of biogenic elements such as C,N,O and S in the environment,which is strongly associated with the emission or storage of carbon and nitrogen,the greenhouse effect,and fate of nutrients and toxic metals or metalloids.The microorganisms involved in Fe(Ⅱ)oxidation can be classified into four groups based on their growth environment and electron acceptor status:acidophilic Fe(Ⅱ)oxidizers,neutral microaerobic Fe(Ⅱ)oxidizers,neutral anaerobic photosynthetic Fe(Ⅱ)oxidizers and neutral anaerobic nitrate reducing Fe(Ⅱ)oxidizers.A summary of the proposed mechanisms of electron transport in microorganisms involved in iron oxidation shows that they all share a common paradigm,that is,ferrous iron is oxidised on outer membrane cytochromes and the electrons obtained from ferrous iron are transmitted from the extracellular membrane through the periplasmic electron transport proteins to various proteins in the inner cell membrane for carbon sequestration and/or reduction of electron acceptors.The study of microorganisms involved in iron oxidation in modern environments has been widely applied to the evolution of early life on Earth,the bioremediation of environmental pollution as well as the synthesis of new materials and bioleaching.This paper reviews the microbial phylogenetic types and electron transfer mechanisms that mediate iron oxidation processes and describes their applications in geology,environment,materials and metallurgy.A great deal of work remains to be done on the isolation and identification of iron-oxidizing bacteria,the detailed analysis of iron-oxidizing metabolic pathways and their geochemical effects,the establishment and improvement of the iron-oxidizing microbiome database,and the application of iron oxidation in environmental pollution.