Abundant and diverse bacterial communities live inside the Prony hydrothermal chimneys connected with the anoxic, high pH and low salinity fluids. Some bacteria can be involved in the oxidation/consoumption of hydrogen released by the Prony springs, such as hydrogenotrophic deltaproteobacterial or betaproteobacterial species thriving in anoxic zones, or oxic/anoxic transition zones of the concretions, respectively). The low archaeal diversity was dominated by uncultured Methanosarcinales linked to methane production or oxidation, as observed in other serpentinization-driven submarine and subterrestrial ecosystems (e.g. Lost City, The Cedars). Hydrogen, methane and sulfur compounds appear as the energy driven forces of the microbial communities inhabiting the hyperalkaline Prony hydrothermal chimneys, indicating that serpentinization-related fluids can sustain chemosynthetic life in photic zone.