Microbial interactions with natural hydrogen in ecosystems driven by serpentinization – HYDROGENOMIC

Hydrogen (H2)-rich fluids released by serpentinization-driven hyperalkaline springs represent a unique opportunity for exploration of natural H2, seen as a huge source of potentially exploitable natural and decarbonized energy. In the subsurface and more specifically in the ultramafic environment, H2 is the main energy source for microbial communities, whose activity could impact H2 fluxes and gas residence time in depth to the near-surface (at T < 100°C). Microorganisms that consume or produce H2 have been documented in a few serpentinizing systems worldwide. However, their interactions with and contributions to the fate of H2 in serpentinizing systems remain largely unknown.
The HYDROGENOMIC project will investigate and reveal the role of microorganisms in regulating H2 concentrations and its ultimate fate at several hyperalkaline serpentinizing springs (as windows into to subsurface biosphere). Our experimental research focuses on two hyperalkaline systems of variable H2 concentrations (Voltri massif, Italy; Prony bay, New Caledonia). We will decipher microbial metabolisms, adaptations and interspecies interactions, and link this to H2 biogeochemistry by carrying out in-field incubations and laboratory experiments combining state-of-the-art complementary cultural, flow cytometry cell sorting and omic approaches coupled with advanced bioinformatics, enabling, for the first time, the enrichment, isolation and characterization of indigenous and active microorganisms. These novel data will be compared with metagenomic and biogeochemical data already obtained by our consortium from two other sites (Ronda massif, Spain; Bulqizë, Albania) to clarify and model the H2 metabolism and interactions of key microbial taxa in serpentinizing ecosystems that we have identified in previous studies.
By linking the activity of (mostly uncultured) microorganisms native to serpentinizing systems with their role in H2 production and consumption, we will answer the major scientific questions currently holding back progress in geologic H2 exploration, namely: 1) why H2 concentration varies by orders of magnitude within the different springs in a single massif, and 2) Are there certain specific abiotic or biotic factors preventing H2-consumers from being active in some environments. The project will also provide crucial knowledge of subsurface hydrogenotrophs, necessary to optimize underground storage of H2 in natural reservoirs and address fundamental questions on one of the most primitive metabolisms of life on Earth.