Occallatibacter riparius gen. nov., sp.. nov and Occallatibacter savannae sp nov., acidobacteria isolated from Namibian soils, and emended description of the family Acidobacteriaceae

Three Gram-negative, non-spore-forming, encapsulated bacteria were isolated from a Namibian river-bank soil (strains 277(T) and 307) and a semiarid savannah soil (strain A2-1c(T)). 16S rRNA gene sequence analyses placed them within subdivision 1 of the Acidobacteria and revealed 100 % similarity between strains 277(T) and 307 and 98.2 % similarity between A2-1c(T) and the former two strains. The closest relatives with validly published names were Telmatobacter bradus, Acidicapsa borealis and Acidicapsa ligni (94.7-95.9 % similarity to the type strains). Cells of all three strains were rod-shaped and motile and divided by binary fission. Ultrastructural analyses revealed a thick cell envelope, resulting mainly from a thick periplasmic space. Colonies of strains 277(T) and 307 were white to cream and light pink, respectively, while strain A2-1c(T) displayed a bright pink colour. All three strains were aerobic, chemoheterotrophic mesophiles with a broad temperature range for growth and a moderately acidic pH optimum. Sugars and complex proteinaceous substrates were the preferred carbon and energy sources. A few polysaccharides were degraded. The major quinone in all three strains was MK-8; MK-7 occurred in strain A2-1c(T) as a minor compound. Major fatty acids were iso-C-15 (:) (0) and iso-C-17 :1 omega 7c. In addition, iso-C-17 : 0 occurred in significant amounts. The DNA G+C contents of strains 277(T), 307 and A2-1c(T) were 59.6, 59.9 and 58.5 mol%, respectively. Based on these characteristics, the three isolates are assigned to two novel species of the novel genus Occallatibacter gen. nov., Occallatibacter riparius sp. nov. [type strain 277(T) (=DSM 25168(T)=LMG 26948(T)) and reference strain 307 (=DSM 25169=LMG 26947)] and Occallatibacter savannae sp. nov. [type strain A2-1c(T) (=DSM 25170(T)=LMG 26946(T))]. Together with several other recently described taxa, the novel isolates provide the basis for an emended description of the established family Acidobacteriaceae.