Disproportionation of elemental sulfur by Exiguobacterium from marine sediment

Elemental sulfur disproportionation is an ancient microbial metabolic process, and the phylogenetic distribution of elemental sulfur disproportionators may be broader than previously thought. We enriched a bacterial community capable of this process, with Exiguobacterium making up 99.45% of the total population. The results indicate that Exiguobacterium facilitates the formation of thiosulfate and sulfide through elemental sulfur disproportionation. This study represents the first report documenting elemental sulfur disproportionation by Bacilli. Metagenomic analysis shows that rhodanese-like sulfur transferase genes are significantly more abundant in the experimental group than in the control group, suggesting that they are implicated in elemental sulfur disproportionation in Exiguobacterium. These findings support the idea that Bacilli and/or Firmicutes are the oldest extant bacterial phyla. Our research fills a critical gap in understanding sulfur biogeochemical cycles. Given the widespread occurrence of Exiguobacterium across various environments, direct microbial transformations between elemental sulfur and thiosulfate are likely prevalent throughout ecological systems.