Brevitalea aridisoli, B-deliciosa and Arenimicrobium luteum, three novel species of Acidobacteria subdivision 4 (class Blastocatellia) isolated from savanna soil and description of the novel family Pyrinomonadaceae

Three novel strains of the phylum Acidobacteria (Ac_11_E3(T), Ac_12_G8(T) and Ac_16_C4(T)) were isolated from Namibian semiarid savanna soils by a high-throughput cultivation approach using low-nutrient growth media. 16S rRNA gene sequence analysis placed all three strains in the order Blastocatellales of the class Blastocatellia (Acidobacteria subdivision 4). However, 16S rRNA gene sequence similarities to their closest relative Pyrinomonas methylaliphatogenes K22(T) were <= 90 %. Cells of strains Ac_11_E3(T), Ac_12_G8(T) and Ac_16_C4(T) were Gram-staining-negative and non-motile and divided by binary fission. Ac_11_E3 T and Ac_16_C4(T) formed white colonies, while those of Ac_12_G8(T) were orange-yellowish. All three strains were aerobic chemoorganoheterotrophic mesophiles with a broad pH range for growth. All strains used a very limited spectrum of carbon and energy sources for growth, with a preference for complex proteinaceous substrates. The major respiratory quinone was MK-8. The major shared fatty acid was iso-C-15 : 0. The DNA G+C contents of strains Ac_11_E3(T), Ac_12_G8(T) and Ac_16_C4(T) were 55.9 mol%, 66.9 mol% and 54.7 mol%, respectively. Based on these characteristics, the two novel genera Brevitalea gen. nov. and Arenimicrobium gen. nov. are proposed, harboring the novel species Brevitaleaaridisoli sp. nov. (Ac_11_E3(T) = DSM 27934(T) = LMG 28618(T)), Brevitalea deliciosa sp. nov. (Ac_16_C4(T) = DSM 29892(T) = LMG 28995(T)) and Arenimicrobium luteum sp. nov. (Ac_12_G8(T) = DSM 26556(T) = LMG 29166(T)), respectively. Since these novel genera are only distantly related to established families, we propose the novel family Pyrinomonadaceae fam. nov. that accommodates the proposed genera and the genus Pyrinomonas (Crowe et al., 2014).