Biomineralizations induced by sulfur disproportionating bacteria from marine hydrothermal vents

International audienceSulfur is an important component of the marine hydrothermal vent ecosystem 1, 2. Sulfur species are abundant in the hydrothermal fluid (H2S), the surrounding seawater (SO4 2-) and the sulfide minerals (pyrite, chalcopyrite) that form a large part of the structure of mature hydrothermal vents 3. Due to its different oxidation states, sulfur species can be used as electron donors or terminal electron acceptor in in microbial catabolisms. Sulfur disproportionation, has been shown to accelerate the sulfide mineral formation up to 10 5-fold with marine and freshwater bacteria 4. In this work, we implemented an autecological approach to investigate the characteristics and kinetics of sulfide mineral formation in the presence of thermophilic sulfur-disproportionating bacteria from hydrothermal vents, grown under different culture conditions, in comparison with purely abiotic conditions. Incubations were carried out in batch and gas lift-reactors using a wide range of controls, and pH, temperature, cell density, catabolic end products, and minerals formed were monitored over time. In particular, we characterized the minerals formed by using X-ray diffraction, Raman spectroscopy and SEM-EDX and investigated the processes involved in microbially mediated mineral formation. Our results show that the rate of sulfide mineral formation is much faster in the presence of these thermophilic sulfur-disproportionating bacteria from hydrothermal vents than under abiotic conditions, and provide insights into the physiology of the sulfur-disproportionating bacteria studied