Thriving of hyperthermophilic microbial communities from a deep-sea sulfidic hydrothermal chimney under electrolithoautotrophic conditions with nitrate as electron acceptor.

Recent studies have shown the presence of an abiotic electrical current across the walls of deep-sea hydrothermal chimneys, allowing the growth of electroautotrophic microbial communities. To understand the role of the different phylogenetic groups and metabolisms involved, this study focused on an electrotrophic enrichment, with nitrate as electron acceptor. The biofilm density, the community composition, the organic products released, and the electrical consumption were monitored by FISH confocal microscopy, qPCR, Metabarcoding, MNR and potentiostat measurements. A statistic analysis by PCA showed the correlation between the different parameters in 3 distinct temporal phases. The Archaeoglobales have been shown to play a key role in the development of the community, as first colonizers and producing pyruvate, therefor used as organic source for heterotrophs. Some Thermococcales showed the ability to perform electrofermentation of this pyruvate into acetate and H2. Finally, through subcultures of the community, we showed the development of a larger biodiversity over time. This observed phenomenon could explain the biodiversity development in hydrothermal context where energy sources are transient and unstable.