Two New Species of Filamentous Sulfur Bacteria of the Genus , sp. nov. and ' Thiothrix sulfatifontis' sp. nov.

The metagenome of foulings from sulfidic spring "Serovodorodny" (Tatarstan, Russia), where members of the genus was observed, was sequenced. Representatives of the phyla , and dominated in the microbial community. The complete genome of sp. KT was assembled from the metagenome. It displayed 93.93-99.72% 16S rRNA gene sequence identity to other species. The average nucleotide identity (ANI) и digital DNA-DNA hybridization (dDDH) showed that the genome designated KT represents a new species within the genus , ' Thiothrix sulfatifontis' sp. nov. KT. The taxonomic status has been determined of the strain sp. CT3, isolated about 30 years ago and not assigned to any of species due to high 16S rRNA gene sequence identity with related species (i.e., 98.8-99.4%). The complete genome sequence of strain CT3 was determined. The ANI between CT3 and other species was below 82%, and the dDDH values were less than 40%, indicating that strain CT3 belongs to a novel species, sp. nov. A genome analysis showed that both strains are chemo-organoheterotrophs, chemolithotrophs (in the presence of hydrogen sulfide and thiosulfate) and chemoautotrophs. For the first time, representatives of showed anaerobic growth in the presence of thiosulfate.