AbstractA novel, autotrophic, mesophilic bacterium, strain RS19-109T, was isolated from sulfidic stream sediments in the Frasassi Caves, Italy. The cells of this strain grew chemolithoautotrophically under anaerobic conditions while disproportionating elemental sulfur (S0) and thiosulfate, but not sulfite with bicarbonate/CO2as a carbon source. Autotrophic growth was also observed with molecular hydrogen as an electron donor, and S0, sulfate, thiosulfate, nitrate, and ferric iron as electron

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... eptors. Oxygen was not used as an electron acceptor and sulfide was not used as an electron donor. Weak growth was observed with sulfate as an electron acceptor and organic carbon as electron donors and carbon sources. The strain also showed weak growth by fermentation of tryptone. Strain RS19-109Twas found to be phylogenetically distinct based on 16S rRNA gene sequence similarity (89.2%) to its closest relative,Desulfurivibrio alkaliphilusAHT2T. The draft genome sequence for strain RS19-109Thad average nucleotide identity, average amino acid identity, andin silicoDNA-DNA hybridization values of 72.2%, 63.0%, and 18.3%, respectively, compared with the genome sequence ofD. alkaliphilusAHT2T. On the basis of its physiological and genomic properties, strain RS19-109Tis proposed as the type strain of a novel species of a novel genus,Thiovibrio frasassiensisgen. nov., sp. nov. A novel family,Thiovibrionaceaefam. nov., is proposed to accommodateThiovibriowithin the order Desulfobulbales.