Genome-Scale Data Call for a Taxonomic Rearrangement of .

(order , class ) form a comparatively isolated family within the phylum and harbor many strains adapted to extreme ecological niches and tolerant against reactive oxygen species. Clarifying the evolutionary history of was so far mainly hampered by the insufficient resolution of the main phylogenetic marker in use, the 16S rRNA gene. In conjunction with the taxonomic characterisation of a motile and aerobic strain, designated YIM M13156 and phylogenetically located within the family, we here carried out a phylogenetic analysis of the genome sequences now available for the type strains of and re-analyzed the previously assembled phenotypic data. The results indicated that the largest genus, , is not monophyletic, hence the arrangement of the genera of must be reconsidered. Taxonomic markers such as polar lipids and fatty-acids profile, cellular features and temperature ranges are indeed heterogeneous within . In contrast to previous studies, we also address which of these features can be interpreted as apomorphies of which taxon, according to the principles of phylogenetic systematics. We thus propose a novel genus, , with the type species sp. nov. and harboring four species formerly assigned to , and . Emended descriptions of all species of are provided for which type-strain genome sequences are publicly available. Our study again demonstrates that the principles of phylogenetic systematics can and should guide the interpretation of both genomic and phenotypic data.