A dynamic microbial sulfur cycle in a serpentinizing continental ophiolite.

Serpentinization transforms ultramafic rock through hydration and oxidation, creating unique fluid chemistries. These fluids contain hydrogen and hydroxyl ions, which influence the mobilization of reduced carbon compounds. Sulfur compounds are transported from the seafloor to continents via serpentinizing ophiolites. Prior research has shown that such environments host microbial life. However, the role of sulfur in sustaining these organisms remains unclear. This gap motivated a closer examination of sulfur cycling in serpentinizing groundwater. No prior work had resolved the full extent of microbial sulfur metabolism in these systems. Understanding this process is essential for mapping the biogeochemical connections between terrestrial and submarine environments. This study addresses the need to clarify sulfur's role in sustaining life in energy-limited systems.

The study aimed to investigate the role of sulfur compounds in supporting microbial life in a serpentinizing continental ophiolite. Hyperalkaline, sulfur-rich groundwater was selected as the study site. Researchers sought to determine which sulfur-cycling taxa are present in this extreme environment. They also aimed to assess the thermodynamic feasibility of sulfur-related redox reactions. The study focused on identifying the metabolic pathways active in the groundwater. Understanding these processes is crucial for evaluating how life persists in oxidant-limited systems. The researchers hypothesized that sulfur cycling is vital for sustaining microbial communities. This work contributes to the broader understanding of biogeochemical links between terrestrial and submarine serpentinizing systems.

The study analyzed hyperalkaline, sulfur-rich groundwater from a serpentinizing ophiolite. Researchers collected samples to assess microbial community composition and activity. Metagenomic and metatranscriptomic sequencing were used to identify active taxa and metabolic pathways. The team focused on sulfur-cycling organisms such as Dethiobacter, Desulfitispora, and 'Desulforudis'. They evaluated the thermodynamic favorability of redox reactions involving sulfate, sulfide, and intermediate sulfur compounds. The groundwater's chemical conditions were measured to determine energy availability. Researchers compared microbial activity with geochemical data to infer metabolic roles. This approach enabled a detailed characterization of the sulfur cycle in the ophiolite environment.

Key sulfur-cycling taxa, including Dethiobacter, Desulfitispora, and 'Desulforudis', were found throughout the ophiolite. These organisms persisted in the hyperalkaline, sulfur-rich groundwater. Biologically catalyzed redox reactions involving sulfate, sulfide, and intermediate sulfur compounds were thermodynamically favorable. Metagenomic and metatranscriptomic data revealed a complex network of sulfur metabolism. Sulfate reduction, sulfide oxidation, and thiosulfate reactions were all active in the groundwater. The sulfur cycle in this environment is complete and supports microbial life. These findings suggest that sulfur biogeochemistry is central to sustaining life in serpentinizing systems. The study highlights the importance of sulfur cycling in linking terrestrial and submarine serpentinizing ecosystems.

The study demonstrates that sulfur compounds play a key role in sustaining microbial life in serpentinizing ophiolites. The presence of Dethiobacter, Desulfitispora, and 'Desulforudis' indicates active sulfur cycling. Thermodynamically favorable redox reactions suggest that sulfur metabolism is vital in these systems. Metagenomic and metatranscriptomic data support the existence of a complex sulfur network. The sulfur cycle in this environment is complete and supports microbial activity. These findings align with the authors' claim that sulfur biogeochemistry connects terrestrial and submarine serpentinizing systems. The study provides evidence for the importance of sulfur in sustaining life in energy-limited environments. The authors propose that sulfur cycling is a key mechanism for life in serpentinizing fluids.