16S rRNA sequencing of Microbial Mdd pathways in four marine sediments
The Mdd pathways are universally existing in marine sediments when exposed to MeSH. The functional genes involved in Mdd pathways and DMS metabolic pathways were analyzed through metagenomic analyses. Although distinct MeSH-depended DMS producing bacteria existed in expansive marine sediments, published MeSH S-methylation gene mddH is more predominant than mddA in the global oceans. Homologs of MddH were found in Polyangia and needed to confirm its ability. Other DMS related processes are important in the western pacific, such as DMS dehydrogenase ddhA and DMSO reductase dorA. In addition to mddA- and mddH-containing bacteria, alternative DMS-producing bacteria and H2S S-methylation bacteria with unknown genes were identified in marine sediments. H2S is more abundant in some environments. Future research efforts should focus on assessing the contribution of microbial H2S S-methylation and MeSH S-methylation to global organosulfur cycling compared with DMSP cleavage process.