Seven New Actinobacterial Species of the Genus Kribbella with Unique Cell Wall Glycopolymers, and Emended Description of the Genus Kribbella

Seven actinomycete strains assigned to seven new species of the genus Kribbella were isolated from soils of different regions in Russia. The strains exhibited 98.2–99.3% similarity of the 16S rRNA gene sequences to each other and 96.2–99.7% similarity to the type strains of the known Kribbella species. The evolutionary distances calculated on the basis of concatenated gene sequences (gyrB–rpoB–recA–relA–atpD, 4108 bp) for the studied organisms and type strains of the known species were within the range reported for Kribbella species (0.014–0.101). The dDDH and ANIb values for the strains studied and the type strains of validly described species with available genomes were below the threshold (49.8 and 92.6%, respectively) for prokaryote species delineation. Members of the putative new species possessed individual phenotypic profiles; some species were found (for the first time in Kribbella) to produce sporangium-like structures, up to 4 μm in diameter. The cell walls of the studied strains contained the teichuronic and/or teichulosonic acids specific for the species or species groups and not described previously for other prokaryotes. The unique branched α-mannan occurred in all studied strains of the genus. Based on the data obtained and the previously published data, the following new species are proposed: Kribbella orskensis sp. nov. (type strain VKM Ас-2538T), Kribbella rubisoli sp. nov. (type strain VKM Aс-2540T), Kribbella antiqua sp. nov. (type strain VKM Ас-2541T), Kribbella kalugense sp. nov. (type strain VKM Ас-2570T), Kribbella steрpae sp. nov. (type strain VKM Ас-2572T), Kribbella pratensis sp. nov. (type strain VKM Ас-2574T), and Kribbella voronezhensis sp. nov. (type strain VKM Ас-2575T) with emended description of the genus Kribbella.