微生物互营产甲烷过程中的种间电子传递

甲烷作为全球第二大温室气体，是典型的可再生清洁能源，也是碳循环中的重要物质组成。大气中约74%的甲烷由产甲烷古菌和其他微生物的互营产生，种间电子传递(interspecies electron transfer, IET)是微生物菌群降低热力学能垒、实现互营产甲烷的核心过程。IET可分为间接种间电子传递(mediated interspecies electron transfer,MIET)和直接种间电子传递(direct interspecies electron transfer, DIET)两种类型，其中MIET依赖氢气、甲酸等载体完成电子的远距离传输，而DIET则依赖导电菌毛、细胞色素c等膜蛋白，通过微生物的直接接触实现电子传递。本文将从IET的研究历程出发，从电子传递机制、微生物种类、生态多样性等方面对微生物互营产甲烷过程中的两种IET类型进行比较，最后对未来待探索的方向进行展望。本综述有助于加深对微生物互营产甲烷过程中IET的理解，为解决由甲烷引发的全球气候变暖等生态问题提供理论支撑。

Interspecies electron transfer during microbial syntrophic methanogenesis

As the second most abundant greenhouse gas in the world, methane is a typical renewable energy source and an important material component in the key link of the carbon cycle. About 74% of atmospheric methane is produced by syntrophy between methanogenic archaea and other microorganisms, and interspecies electron transfer (IET) is the core process of methanogenic microbial communities to overcome the thermodynamic energy barrier. IET can be sorted into mediated interspecies electron transfer (MIET) and direct interspecies electron transfer (DIET). During MIET, microorganisms rely on electron shuttles such as hydrogen and formate for long-distance electron transport. However, during DIET, microbial communities establish direct connections and transport electrons through electrically conductive pili, cytochrome c and other membrane-bound proteins. This review will start from the research history of IET and then compare MIET and DIET in terms of electron transfer mechanism, related microbial species, and ecological distribution. Finally, we will summarize the future research directions. This review is expected to help deepen the understanding of IET during microbial syntrophic methanogenesis and lay a theoretical basis for solving ecological problems such as global warming caused by methane.