Disproportionation of elemental sulfur by <i>Exiguobacterium</i> 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 <i>Exiguobacterium</i> making up 99.45% of the total population. The results indicate that <i>Exiguobacterium</i> 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 <i>Exiguobacterium.</i> 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 <i>Exiguobacterium</i> across various environments, direct microbial transformations between elemental sulfur and thiosulfate are likely prevalent throughout ecological systems.