Parviterribacter kavangonensis gen. nov., sp. nov. and Parviterribacter multiflagellatus sp. nov., novel members of Parviterribacteraceae fam. nov. within the order Solirubrobacterales, and emended descriptions of the classes Thermoleophilia and Rubrobacteria and their orders and families.

Abstract

Two Gram-type-positive, non-spore-forming bacteria, strains D16/0/H6T and A22/0/F9_1T, were isolated from Namibian semiarid savannah soils. 16S rRNA gene sequence analysis revealed 96.6 % identity between the two strains and placed them within the order Solirubrobacterales of the class Thermoleophilia. The closest phylogenetic relatives with validly published names were several strains of the genus Solirubrobacter and the species Conexibacter arvalis, with pairwise sequence similarities of ≤ 94.0 %. Cells of strain D16/0/H6T were ovoid to rod-shaped, whereas strain A22/0/F9_1T formed regular rods. Cells of both strains were motile and divided by binary fission. Colonies were pink and white to pale yellowish/brownish, respectively. Strains D16/0/H6T and A22/0/F9_1T were aerobic, chemoheterotrophic mesophiles with broad temperature (13-43 and 17-43 °C, respectively) and pH (pH 4.5-8.5 and 5.0-9.5) ranges for growth. Complex proteinaceous substrates and glucose were the preferred carbon and energy sources. Strain A22/0/F9_1T also grew on various carboxylic acids. For both strains, the peptidoglycan diamino acid was meso-2,6-diaminopimelic acid. The major quinone was MK-8. As a minor compound, MK-7 occurred in strain D16/0/H6T; strain A22/0F9_1T also contained MK-7, MK-7(H2) and MK-8(H2). Major fatty acids of strain D16/0/H6T were 10-methyl C17 : 0, iso-C16 : 0 and C18 : 1ω9c. Strain A22/0F9_1T contained C18 : 1ω9c, C17 : 1ω8c, C17 : 1ω6c and iso-C16 : 0 as major components. The DNA G+C contents of strains D16/0/H6T and A22/0/F9_1T were 72.8 and 74.0 mol%, respectively. Based on these characteristics, the two isolates are assigned to novel species of the new genus Parviterribacter gen. nov., the type species Parviterribacter kavangonensis sp. nov. (type strain D16/0/H6T = DSM 25205T = LMG 26950T) and a second species Parviterribacter multiflagellatus sp. nov. (type strain A22/0/F9_1T = DSM 25204T = LMG 26949T). As the novel genus and species cannot be clearly assigned to an established family within the order Solirubrobacterales, the novel family Parviterribacteraceae fam. nov. is proposed. Emended descriptions of the classes Thermoleophilia and Rubrobacteria and their orders and families are also provided.