The missing enzymatic link in syntrophic methane formation from fatty acids

Abstract

Significance The syntrophic interaction of fermenting bacteria with methanogenic archaea is crucial for the globally relevant conversion of biomass into methane. Fifty years after the discovery of syntrophy, it has remained enigmatic how the oxidation of saturated fatty acid fermentation intermediates can be coupled to the thermodynamically extremely unfavorable reduction of CO 2 to methane and how such a process can sustain growth of both syntrophic partners. Here, we provide biochemical evidence that heme b cofactors of a membrane-bound oxidoreductase and a modified quinone with perfectly fine-tuned redox potentials are the key players in this microbial process. Bioinformatics analyses suggest that the oxidoreductase plays a crucial role in lipid catabolism of the majority of prokaryotes.