Mineral-enhanced thiosulfate disproportionation by a novel Sulfuricella sp. from the continental deep subsurface
ABSTRACT Metal oxides play a significant role in continental subsurface habitability, locally enhancing biofilm biomass and supporting distinct microbial assemblages relative to planktonic communities. However, the mechanisms driving interactions between biofilms and minerals which promote this diversity and biomass growth are often unclear. Microbes can and do derive energy for growth via active electron exchange with metal oxides, with iron and manganese oxides serving as key electron acceptors in a range of environments. Alternatively, growth can also be enhanced via the passive removal of wastes, e.g. sulfide scavenging by metal oxides. Genome-informed cultivation experiments are useful for probing the metabolic interactions between microbes and metal oxides. We isolated a deep subsurface microbe using growth experiments with MnO2, a highly favorable electron acceptor at the Deep Mine Microbial Observatory (DeMMO), our continental subsurface study site. We then performed genome sequencing and analysis to inform the potential metabolic interactions between this organism and MnO2. Our findings suggest MnO2 passively enhances the growth of this novel bacterial species, Sulfuricella sp. D3-1, by scavenging sulfide produced during thiosulfate disproportionation. We posit that passive sulfide scavenging by metal oxides may be a common and important process at DeMMO, promoting habitability of this deep subsurface environment via sulfide detoxification and thermodynamic promotion of sulfide-producing metabolisms. We compare the genome of Sulfuricella sp. D3-1 to two other species within the Sulfuricella, revealing shared traits that confer resilience under hostile conditions. The Sulfuricella are globally distributed and occur across several deep subsurface settings, suggesting their ecological importance to deep subsurface sulfur cycling. iquity of iron in deep continental settings, we posit that iron-fueled life is pervasive in the deep continental biosphere.
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