FY 2026 Metabolic and population profiles of active subseafloor autotrophs in young oceanic crust at deep-sea hydrothermal vents Elkassas, S.M., C.S. Fortunato, S.L. Grim, D.A. Butterfield, J.F. Holden, J.J. Vallino, C.K. Algar, L. Zeigler Allen, B.T. Larson, G. Proskurowski, E. Reddington, L.C. Stewart, B. Topçuoğlu, and J.A. Huber Appl. Environ. Microbiol., 91(11), e01868-25, doi: 10.1128/aem.01868-25, View open access article at ASM Journals (external link) (2025) At deep-sea hydrothermal vents, magmatically driven rock-water reactions in the crust generate gases and other reduced compounds that subseafloor microorganisms use for chemolithoautotrophy. In this study, microbial autotrophs from three diffuse flow hydrothermal vents at Axial Seamount in 2013 and 2014 were isotopically labeled using RNA stable isotope probing, targeting subseafloor autotrophic mesophiles (30°C), thermophiles (55°C), and hyperthermophiles (80°C). We constructed taxonomic and functional profiles of active chemolithoautotrophs, examined population distributions across sites, and linked primary producers to their specific metabolic strategies within the subseafloor community. Dominant autotrophs exhibited hydrogen-dependent dissimilatory metabolisms, such as sulfur and nitrate reduction and methanogenesis, as well as microaerophilic sulfide oxidation even at 80°C, consistent with fluid chemistries at each site. While hydrogenotrophic methanogenic archaea (Methanothermococcus) were restricted in their distribution and activity, hydrogenotrophic sulfur and nitrate reducers from the Aquificota (Thermovibrio) and Campylobacterota (Nautiliaceae, Hydrogenimonas, and Desulfurobacteriaceae) were consistently active and present at all sites and years at both the population and community levels. Hydrogenase transcripts were significantly differentially expressed, and diverse hydrogenases were found in metagenome-assembled genomes of Aquificota members, highlighting the importance and versatility of their hydrogen utilization strategies, which likely contribute to their cosmopolitan distribution across geochemically disparate subseafloor sites. Together, this study provides new insights into the functional dynamics and distribution of key subseafloor autotrophic microbial communities in young oceanic crust at deep-sea hydrothermal vents. Feature Publications | Outstanding Scientific Publications Contact Sandra Bigley | Help
