Genome-Scale Data Call for a Taxonomic Rearrangement of Geodermatophilaceae

Abstract

<i>Geodermatophilaceae</i> (order <i>Geodermatophilales</i>, class <i>Actinobacteria</i>) form a comparatively isolated family within the phylum <i>Actinobacteria</i> and harbor many strains adapted to extreme ecological niches and tolerant against reactive oxygen species. Clarifying the evolutionary history of <i>Geodermatophilaceae</i> 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^T and phylogenetically located within the family, we here carried out a phylogenetic analysis of the genome sequences now available for the type strains of <i>Geodermatophilaceae</i> and re-analyzed the previously assembled phenotypic data. The results indicated that the largest genus, <i>Geodermatophilus</i>, is not monophyletic, hence the arrangement of the genera of <i>Geodermatophilaceae</i> must be reconsidered. Taxonomic markers such as polar lipids and fatty-acids profile, cellular features and temperature ranges are indeed heterogeneous within <i>Geodermatophilus</i>. 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, <i>Klenkia</i>, with the type species <i>Klenkia marina</i> sp. nov. and harboring four species formerly assigned to <i>Geodermatophilus, G. brasiliensis, G. soli, G. taihuensis</i>, and <i>G. terrae</i>. Emended descriptions of all species of <i>Geodermatophilaceae</i> 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.