Usitatibacter rugosus gen. nov., sp. nov. and Usitatibacter palustris sp. nov., novel members of Usitatibacteraceae fam. nov. within the order Nitrosomonadales isolated from soil

Members of the metabolically diverse order Nitrosomonadales inhabit a wide range of environments. Two strains affiliated with this order were isolated from soils in Germany and characterized by a polyphasic approach. Cells of strains 0125_3 T and Swamp67 T are Gram-negative rods, non-motile, non-spore-forming, non-capsulated and divide by binary fission. They tested catalase-negative, but positive for cytochrome c -oxidase. Both strains form small white colonies on agar plates and grow aerobically and chemoorganotrophically on SSE/HD 1 : 10 medium, preferably utilizing organic acids and proteinaceous substrates. Strains 0125_3 T and Swamp67 T are mesophilic and grow optimally without NaCl addition at slightly alkaline conditions. Major fatty acids are C 16 : 1 ω 7 c , C 16 : 0 and C 14 : 0 . The major polar lipids are diphosphatidylglycerol, phosphatidylethanolamine and phosphatidyglycerol. The predominant respiratory quinone is Q-8. The G+C content for 0125_3 T and Swamp67 T was 67 and 66.1 %, respectively. The 16S rRNA gene analysis indicated that the closest relatives (<91 % sequence similarity) of strain 0125_3 T were Nitrosospira multiformis ATCC 25196 T , Methyloversatilis universalis FAM5 T and Denitratisoma oestradiolicum AcBE2-1 T , while Nitrosospira multiformis ATCC 25196 T , Nitrosospira tenuis Nv1 T and Nitrosospira lacus APG3 T were closest to strain Swamp67 T . The two novel strains shared 97.4 % 16S rRNA gene sequence similarity with one another and show low average nucleotide identity of their genomes (83.8 %). Based on the phenotypic, chemotaxonomic, genomic and phylogenetic analysis, we propose the two novel species Usitatibacter rugosus sp. nov (type strain 0125_3 T =DSM 104443 T =LMG 29998 T =CECT 9241 T ) and Usitatibacter palustris sp. nov. (type strain Swamp67 T =DSM 104440 T =LMG 29997 T =CECT 9242 T ) of the novel genus Usitatibacter gen. nov., within the novel family Usitatibacteraceae fam. nov.