Methanolobus use unspecific methyltransferases to produce methane from dimethylsulfide

Abstract

Dimethylsulfide (DMS) is the most abundant biogenic organic sulfur compound and a methane precursor in anoxic sediments. However, understanding of the microbial diversity driving DMS-dependent methanogenesis is limited, and the metabolic pathways underlying this process in the environment remain unexplored. To address this, we used anoxic incubations, amplicon sequencing, genome-centric metagenomics and metatranscriptomics of brackish sediments of the Baltic Sea. We identified Methanolobus as the dominant methylotrophic methanogens in all our sediment samples. We also showed that Methanolobus use trimethylamine- and methanol-methyltransferases, not methyl-sulfide methyltransferases, when producing methane from DMS. This demonstrated that methylotrophic methanogenesis does not require a substrate-specific methyltransferase as was previously accepted and highlights the versatility of the key enzymes in methane production in anoxic sediments.