Abstract
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 electrotrophic enrichment with nitrate as electron acceptor. The biofilm density, community composition, production of organic compounds, and electrical consumption were monitored by FISH confocal microscopy, qPCR, metabarcoding, NMR, and potentiostat measurements. A statistical analysis by PCA showed the correlation between the different parameters (qPCR, organic compounds, and electron acceptors) in three distinct temporal phases. In our conditions, the Archaeoglobales have been shown to play a key role in the development of the community as the first colonizers on the cathode and the first producers of organic compounds, which are then used as an organic source by heterotrophs. Finally, through subcultures of the community, we showed the development of a greater biodiversity over time. This observed phenomenon could explain the biodiversity development in hydrothermal contexts, where energy sources are transient and unstable.
Highlights
Deep-sea hydrothermal vents, discovered for the first time in 1977, harbor complex ecosystems sheltering extremophilic life forms [1,2]
An open circuit potential (OCP) control was performed in the same conditions as enrichments and inoculated with the hydrothermal chimney
In the microbial electrochemical system (MES) filled with the mineral medium, the cathode poised at −590 mV vs. SHE was the only potential energy source available for microbial growth [19]
Summary
Deep-sea hydrothermal vents, discovered for the first time in 1977, harbor complex ecosystems sheltering extremophilic life forms [1,2]. These hydrothermal chimneys result from the infiltration of seawater into the seabed, which is heated by an underlying magma chamber and reacts with surrounding minerals to produce a hot hydrothermal fluid 300–400 ◦ C) rich in minerals and reduced compounds (H2 , H2 S, CH4 ) This hot, reduced, pressurized fluid moves back to the sea floor to precipitate in contact with the cold The colonizers would use the oxidation of reduced compounds from the hydrothermal fluid as an energy source and CO2 as a
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