Cultivating microbial communities from the serpentinite-hosted Prony Bay hydrothermal field on different carbon sources in hydrogen-fed bioreactors Popall, R. M. Roland, A. /Davidson, Sylvain /Combet-Blanc, Yannick Price, R. E. /Quéméneur, Marianne Postec, A. Erauso, G. Serpentinization Submarine alkaline vent Hydrothermal system Alkaliphile Hydrogenotroph Primary production Carbon fixation Origin of life Background The primary source of carbon is one of the most fundamental questions regarding the development of microbial communities in serpentinite-hosted systems. The hydration of ultramafic rock to serpentinites releases large amounts of hydrogen and creates hyperalkaline conditions that deplete the environment of dissolved inorganic carbon. Metagenomic studies suggest that serpentinite-hosted microbial communities depend on the local redissolution of bicarbonate and on small organic molecules produced by abiotic reactions associated with serpentinization. Methods To verify these bioinformatic predictions, microbial consortia collected from the Prony Bay hydrothermal field were enriched under anoxic conditions in hydrogen-fed bioreactors using bicarbonate, formate, acetate, or glycine as the sole carbon source. Conclusions With the exception of glycine, the chosen carbon substrates allowed the growth of microbial consortia characterized by significant enrichment of individual taxa. Surprisingly, these taxa were dominated by microbial genera characterized as aerobic rather than anaerobic as expected. Our results indicate the presence of both autotrophic and heterotrophic taxa that may function as foundation species in serpentinite-hosted shallow subsurface ecosystems. We propose that an intricate feedback loop between these autotrophic and heterotrophic foundation species facilitates ecosystem establishment. Bicarbonate-fixing Meiothermus and Hydrogenophaga, as well as formate-fixing Meiothermus, Thioalkalimicrobium, and possibly a novel genotype of Roseibaca might produce organic compounds for heterotrophs at the first trophic level. In addition, the base of the trophic network may include heterotrophic Roseibaca, Acetoanaerobium, and Meiothermus species producing CO2 from acetate for a more diverse community of autotrophs. The cultivated archaeal community is expected to recycle CH4 and CO2 between Methanomicrobiales and Methanosarcinales with putative Woesearchaeales symbionts. 2025 text https://www.documentation.ird.fr/hor/fdi:010095465 fdi:010095465 Popall R. M., Roland A., Davidson Sylvain, Combet-Blanc Yannick, Price R. E., Quéméneur Marianne, Postec A., Erauso G.. Cultivating microbial communities from the serpentinite-hosted Prony Bay hydrothermal field on different carbon sources in hydrogen-fed bioreactors. 2025, 20 (1), 135 [14 ] EN NOUVELLE CALEDONIE PACIFIQUE