一株革兰氏阳性铁还原菌的胞外电子传递机制研究

Iron respiration, driven by the dissimilatory Fe(III)-reducing bacteria (FeRB), is an important soil microbial respiration pathway. Extracellular electron transfer is the key part of iron respiration, which has been studied extensively for Gram-negative FeRB. Although Gram-positive FeRB play an important role in element cycles and pollutant decomposition in soil, few investigations have been carried out on the iron respiration characters and extracellular electron transfer mechanism of them presently. This project aims to set up an experimental system concerning a novel Gram-positive FeRB Bacillus thermophilus SgZ-10, analyze its iron respiration characters, quantify its electron transfer capacity, and then find outits channel of extracellular electron transfer. Furthermore, whole genomes of strain SgZ-10 will be sequenced, and part of the functional genes involved in extracellular electron transfer will be looked for, by which the molecular mechanism of extracellular electron transfer can be illustrated. By comparing the extracellular electron transfer process between Gram-negative and -positive FeRB, the results from this project are expected to provide more information on extracellular electron transfer in microbial iron respiration, which will be significantly helpful for understanding the role and function of Gram-positive FeRB in soil iron respiration.

铁还原菌驱动的铁呼吸是土壤中重要的微生物呼吸形式，胞外电子传递机制是铁呼吸研究的核心问题。革兰氏阳性铁还原菌对于土壤重要元素循环及污染物转化具有重要意义。然而，目前胞外电子传递机制的研究主要集中于革兰氏阴性菌，有关阳性铁还原菌的铁呼吸特性及胞外电子转移机制的报道非常少见。本项目拟以阳性铁还原菌新种Bacillus thermophilus SgZ-10为研究对象，系统研究其铁呼吸特性及胞外电子传递能力，重点探析其铁呼吸过程中可能存在的胞外电子传递途径，并进一步测定菌株的全基因组序列，明确参与胞外电子转移的部分功能基因，尝试在分子水平上对其胞外电子传递机制进行初步探索，深入探讨和比较阳性铁还原菌和阴性铁还原菌的胞外电子传递规律，为全面解析微生物驱动的铁呼吸作用提供依据，为理解阳性铁还原菌在土壤铁呼吸的角色与功能提供理论基础。

胞外呼吸是近年来发现的新型微生物厌氧能量代谢方式，主要包括铁呼吸、腐殖质呼吸和产电呼吸三种形式。革兰氏阳性铁呼吸菌是土壤胞外呼吸的重要参与者，然而有关阳性铁呼吸菌的胞外呼吸特性及胞外电子转移机制的报道非常少见。本项目分离并鉴定了一株高效革兰氏阳性铁呼吸菌新种Desulfotomaculum ferrireducens GSS09，为研究阳性铁呼吸菌的胞外呼吸过程及其电子传递机制提供基础。本项目以菌株GSS09为研究对象，分别评价了该菌以腐殖质、不溶性铁氧化物和电极为电子受体时的胞外电子转移能力，表明该菌具有多种胞外呼吸功能。在此基础上，进一步探讨了菌株GSS09可能的胞外电子传递途径，证明了其可以利用代谢中间产物作为电子穿梭体进行电子传递。为了从分子水平上探索其胞外电子传递机制，利用三代测序技术测定了GSS09的全基因组序列，预测了可以作为电子传递载体的氧化还原蛋白，探讨和比较了GSS09与传统的阴性铁呼吸菌的氧还蛋白差异，提出并详细阐述了硫循环介导的胞外电子传递机制。通过本项目的成果为理解革兰氏阳性铁呼吸菌驱动的胞外呼吸过程提供新线索，为完善发展土壤重要元素循环的胞外呼吸理论提供科学依据。