Sulfur disproportionating microbial communities in a dynamic, microoxic‐sulfidic karst system

Abstract

Biogeochemical sulfur cycling in sulfidic karst systems is largely driven by abiotic and biological sulfide oxidation, but the fate of elemental sulfur (S0) that accumulates in these systems is not well understood. The Frasassi Cave system (Italy) is intersected by a sulfidic aquifer that mixes with small quantities of oxygen‐rich meteoric water, creating Proterozoic‐like conditions and supporting a prolific ecosystem driven by sulfur‐based chemolithoautotrophy. To better understand the cycling of S0 in this environment, we examined the geochemistry and microbiology of sediments underlying widespread sulfide‐oxidizing mats dominated by Beggiatoa. Sediment populations were dominated by uncultivated relatives of sulfur cycling chemolithoautotrophs related to Sulfurovum, Halothiobacillus, Thiofaba, Thiovirga, Thiobacillus, and Desulfocapsa, as well as diverse uncultivated anaerobic heterotrophs affiliated with Bacteroidota, Anaerolineaceae, Lentimicrobiaceae, and Prolixibacteraceae. Desulfocapsa and Sulfurovum populations accounted for 12%–26% of sediment 16S rRNA amplicon sequences and were closely related to isolates which carry out autotrophic S0 disproportionation in pure culture. Gibbs energy (∆Gr) calculations revealed that S0 disproportionation under in situ conditions is energy yielding. Microsensor profiles through the mat‐sediment interface showed that Beggiatoa mats consume dissolved sulfide and oxygen, but a net increase in acidity was only observed in the sediments below. Together, these findings suggest that disproportionation is an important sink for S0 generated by microbial sulfide oxidation in this oxygen‐limited system and may contribute to the weathering of carbonate rocks and sediments in sulfur‐rich environments.

Environmental processes and health implications potentially mediated by dust‐borne bacteria

“…Notably, such interactions appear to be prevalent within the core active microorganism communities of the sampled DEs (Figure 2C). The cycling of essential elements, such as carbon and nitrogen, plays a crucial role in the survival of microorganisms in unfavourable environments (Aasfar et al, 2021;Aronson et al, 2023;Bollmann et al, 2013;Jawaharraj et al, 2021;Sahoo et al, 2021;Yan et al, 2008). Our analysis revealed the presence of highly potentially active microorganisms engaged in carbon and nitrogen metabolism, suggesting a positive element cycle within the community.…”