Potential for microbial methanethiol-dependent dimethylsulfide production in different marine sediments

Dimethyl sulfide (DMS) plays a pivotal role in sulfur cycling and climate regulation. This study investigates microbial DMS production via the methylation of hydrogen sulfide (H₂S) and methanethiol (MeSH) in nearshore, pelagic deep-sea, and cold-seep sediments using culture-dependent and -independent methods. DMS production is detected in all sediments with exogenous MeSH addition. High mdd abundance is found in pelagic deep-sea sediments (24.55%-26.73%) from the Kuroshio-Oyashio Extension region, as well as in the nearshore sediments (25.78%). Metagenomic analyses reveal previously unrecognized Mdd-encoding taxa, such as Polyangia, and eight Bacteroidota and Bacillota isolates may possess unknown Mdd enzymes. Importantly, a widespread alternative pathway that converts H₂S to MeSH is identified, representing a significant source of MeSH. These findings reveal a prevalent and diverse microbial pathway for DMS production in marine sediments, underscoring the need for further investigation to discover Mdd⁺ microbial contributors.