产甲烷古菌与电子传递体相互作用机制研究进展

Research progress on the interaction mechanisms between methanogenic archaea and electron mediators

厌氧消化是实现有机废弃物资源化最有效的技术之一,实现形式是产生生物沼气.作为一种清洁能源,生物沼气可以有效减少化石燃料的使用,进而减少温室气体的排放.产甲烷古菌位于厌氧发酵链末端,是生物沼气主要成分甲烷的直接生产者.在厌氧消化系统中,产甲烷古菌与发酵链前端微生物以及各种天然和人工电子传递体存在着活跃的电子互营过程,对于维持厌氧消化系统的稳定性和改善生物沼气的生成效率具有重要作用.本文综述近年来报道的在强化厌氧消化过程中常用的铁基与碳基电子传递体与产甲烷古菌的相互作用机制,着重介绍两类电子传递体通过自身氧化还原反应或物理性质与产甲烷古菌细胞膜上的氢酶和细胞色素c进行电子互营的微观作用机理,分析两类电子传递体通过参与胞外电子传递过程与产甲烷古菌能量代谢可能存在的耦合机制,其中乙酸型产甲烷古菌基于电子歧化传递在进行胞外三价铁呼吸过程中存储能量,从而增强产甲烷代谢,改变了目前对甲烷生成的生化和生态学理解,极大推进了产甲烷古菌与胞外电子传递体相互作用的研究.产甲烷古菌胞外电子传递路径的不清晰和其细胞膜上蛋白功能的不确定是制约产甲烷古菌与电子传递体相互作用机制研究的重要因素.因此提出利用快速发展的分子生物学如基因敲除以及荧光标记等技术进一步深入研究产甲烷古菌与电子传递体相互作用机制的可能性和新思路.

Anaerobic digestion is one of the most effective technologies for recycling the organic waste in the form of biogas.Biogas is a clean energy that can effectively reduce the use of fossil fuels and thus reduce greenhouse gas emissions.Methanogenic archaea are located at the end of the anaerobic fermentation chain and are the direct producers of methane,the main component of biogas.In the anaerobic digestion system,there exists an active electronic interaction process between methanogen and microorganisms at the initial part of the fermentation chain,as well as various natural and artificial electron mediators,which play an important role in maintaining the stability of the anaerobic digestion system and improving the efficiency of biogas generation.We reviewed the interaction mechanisms between methanogenic archaea and iron-based and carbon-based electron mediators,which are two recently reported types of electron mediators commonly used in enhancing anaerobic digestion.We summarized the mechanisms of electron interaction between the two types of electron mediators and hydrogenase as well as cytochrome c on the cell membrane of methanogenic archaea through their redox reactions or physical properties and aimed to analyze the possible coupling mechanism between the two types of electron mediators and energy metabolism of methanogenic archaea through their participation in the extracellular electron transfer process.Among them,acetate-utilizing methanogens conserve energy through electron bifurcation by Fe(III)-dependent respiratory metabolism of acetate,augmenting production of methane.These results transform the ecological and biochemical understanding of methanogenesis.The unclear extracellular electron transfer pathway of methanogenic archaea and the uncertain function of proteins on their cell membrane are important factors that restrict the study of the interaction mechanism between methanogenic archaea and electron mediators.The review highlights the prospects of using rapidly developing molecular biology,such as gene knockout,and fluorescent labeling techniques to further study the interaction mechanism between methanogenic archaea and electron mediators.