Studying organosulfonate metabolism in southern Russia chernozem soil microbial community: ubiquity of the desulfonation pathways and possible mixotrophy in common soil heterotrophs.

Microbial metabolism of organosulfonates (OS) have been researched for at least three decades. However, the studies conducted so far were heavily focused on marine ecosystems, while in terrestrial ecosystems microbial desulfonation pathways are poorly characterized. Here we describe culturable microbial community of chernozem soil from the perspective of OS-based metabolism. Using the metagenomic and culture-dependent approaches, we compare microbial isolates grown on OS to the isolates enriched using common media for soil bacteria and show that there is no substantial difference in terms of taxonomy and OS metabolism genes representation. Alkanesulfonates and taurine are the primary OS compounds metabolized by soil bacteria through ssuDE and tauD enzymatic systems, while other OS desulfonation pathways are rare or absent. Actinobacterial and alphaproteobacterial representatives were the dominant part of OS-utilization community. We show in vitro taurine desulfonation and subsequent re-utilization of produced sulfite by soil actinobacterial isolates of Streptomyces anulatus and Arthrobacter siccitolerans. We hypothesize that microbial desulfonation coupled to sulfite oxidation may be a strategy to generate energy from both organic and inorganic molecules oxidation in heterotrophs (that is, mixotrophy). Finally, it is that OS-metabolism represents a ubiquitous metabolic capability rather than a niche trait, interlinking key biogeochemical cycles, particularly sulfur, nitrogen, and carbon.