Thiosulfativibrio zosterae gen. nov., sp. nov., and Thiosulfatimonas sediminis gen. nov., sp. nov.

Aerobic, Gram-stain-negative, obligately chemolithoautotrophic thiosulfate-oxidizing bacteria, strains AkT22 and aks77 were isolated from a brackish lake in Japan. Strains AkT22 and aks77 were isolated from samples of eelgrass and sediment, respectively. Growth on sulfide, tetrathionate, elemental sulfur, and organic substrates was not observed for both strains. Growth of the strains was observed at 5 °C or higher temperature, with optimum growth at 22 °C. Strain AkT22 grew at a pH range of 5.8-8.0, with optimum growth at pH 6.7-7.8. Strain aks77 grew at a pH range of 5.8-8.5, with optimum growth at pH 7.0-7.9. Major cellular fatty acids (> 10% of total) of strain AkT22 were C, C, and C. The sole respiratory quinone was ubiquinone-8 in both strains. The genome of strain AkT22 consisted of a circular chromosome, with size of approximately 2.6 Mbp and G + C content of 43.2%. Those values of the genome of strain aks77 were ca. 2.7 Mbp and 45.5%, respectively. Among cultured bacteria, Thiomicrorhabdus aquaedulcis HaS4 showed the highest sequence identities of the 16S rRNA gene, to strains AkT22 (94%) and aks77 (95%). On the basis of these results, Thiosulfativibrio zosterae gen. nov., sp. nov. and Thiosulfatimonas sediminis gen. nov., sp. nov. are proposed, with type strains of AkT22 (= BCRC 81184 = NBRC 114012 = DSM 109948) and aks77 (= BCRC 81183 = NBRC 114013), respectively.