Isolation and Genomic Characterization of Desulfuromonas soudanensis WTL, a Metal- and Electrode-Reducing Bacterium from Anoxic Deep Subsurface Brine

摘要: Reaching a depth of 713 m below the surface, Soudan Underground Iron Mine (Soudan, Minnesota, USA) transects massive Archaean (2.7 Ga) banded iron formation, providing remarkably accessible window into terrestrial deep biosphere. Despite carbon limitation, metal-reducing microbial communities are present in potentially ancient anoxic brines continuously emanating from exploratory boreholes on Level 27. Using graphite electrodes deposited situ as bait, we enriched and isolated novel halophilic iron-reducing Deltaproteobacterium, Desulfuromonas soudanensis strain WTL, an acetate-fed three-electrode bioreactor poised at +0.24 V (vs. standard hydrogen electrode). Cyclic voltammetry revealed that D. releases electrons redox potentials approximately 100 mV more positive than model freshwater surface isolate Geobacter sulfurreducens, suggesting its extracellular respiration is tuned for higher potential electron acceptors. contains 3,958,620-bp circular genome, assembled to completion using single-molecule real-time (SMRT) sequencing reads, which encodes complete TCA cycle, 38 putative multiheme c-type cytochromes, one 69 heme-binding motifs, LuxI/LuxR quorum sensing cassette produces unidentified N-acyl homoserine lactone. Another cytochrome predicted lie within prophage, horizontal transfer respiratory proteins plays role flexibility among metal reducers. Isolation underscores utility electrode-based approaches enriching rare reducers wide range habitats.