Interspecies electron transfer during microbial syntrophic methanogenesis

Abstract:

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.

Key words:microbial syntrophy;interspecies electron transfer;anaerobic methanogenesis;interspecies hydrogen/formate transfer;direct interspecies electron transfer