Williamwhitmania taraxaci gen. nov., sp. nov., a proteolytic anaerobe with a novel type of cytology from Lake Untersee in Antarctica, description of Williamwhitmaniaceae fam. nov., and emendation of the order Bacteroidales Krieg 2012.

The proteolytic bacterium strain A7P-90m was isolated from Lake Untersee, Antarctica. The anoxic water was collected from a perennially sealed (~100 millennia) glacial ice lake. Gram-stain-negative cells were 0.18-0.3×8.0-25.0 µm in size, straight, slender rods with unusual gliding motility by external, not previously reported, organelles named here as antiae. At the end of stationary phase of growth, spheroplasts were terminally formed and the cells resembled dandelions. After death, cells were helical. The isolate was an athalassic, strictly anaerobic and catalase-negative proteolytic chemoorganotroph. It was moderately psychrophilic with a temperature range for growth of 3-26 °C and an optimum at 22-23 °C. The pH range for growth was 5.5-7.8 with an optimum at 6.9. Major cellular fatty acids were branched pentadecanoic and tridecanoic acids, and saturated tetradecanoic acids. The quinone system comprised menaquinone MK-7. The strain was sensitive to all checked antibiotics and ascorbic acid. The G+C content of the genomic DNA was 42.6 mol%. Based on average nucleotide identity, average amino acid identity and phylogenetic analyses, the novel isolate was placed within a unique phylogenetic cluster distant from all eight families in the order Bacteroidales and formed a novel family with the proposed name Williamwhitmaniaceae fam. nov. The description of the order Bacteroidales was emended accordingly. The name Williamwhitmania taraxaci gen. nov., sp. nov. is proposed for the new genus and novel species with the type strain A7P-90m (=DSM 100563=JCM 30888). The complete draft genome sequence was deposited at the Joint Genomes Institute (JGI) under number IMG OID 2654588148 and in SRA listed as SRP088197.