gen. nov. sp. nov., a novel bacterium of the order isolated from a cave and a proposal of fam. nov.

Two Gram-stain-positive, aerobic, non-spore-forming, non-motile, irregular rod-shaped actinobacteria, designated as D2-41 and D3-21, were isolated from soil samples collected in a natural cave in Jeju, Republic of Korea. Both of the isolates were shown to share 100 % 16S rRNA sequence identity. The cell wall contained -diaminopimelic acid, arabinose and galactose. The predominant menaquinone was MK-8(H). The polar lipids contained phosphatidylethanolamine, phosphatidylglycerol, phosphatidylinositol, phosphatidylinositol mannoside, an unidentified aminolipid, an unidentified aminoglycolipid, an unidentified phospholipid and two unidentified lipids. The predominant fatty acids were C and summed feature 3 (C 7 and/or iso-C 2-OH). Mycolic acids of C-C were present. The 16S rRNA gene trees showed that the organisms occupied a distinct position remotely located from recognized genera within the order , albeit with the 16S rRNA gene similarities of 97.0-97.1 % with , and . The genome sizes and DNA G+C contents of strains D2-41 and D3-21 were 4.77-4.88 Mbp and 69.8 mol%, respectively. Both of the isolates shared an average nucleotide identity of 99.4 % and digital DNA-DNA hybridization of 95.2 % to each other, revealing that strains D2-41 and D3-21 belonged to the same species. In the core genome-based phylogenomic tree, both of the isolates were found to be closely associated with members of the genus . However, strains D2-41 and D3-21 revealed the highest amino acid identity values (mean 66.5 %, range 66.2-67.0 % with the genus of the family , followed by the genus (mean 64.1 %, range 63.6-64.7 %) of the family . Based on the combined data obtained here, the novel isolates belong to a new genus of the new family for which the name gen. nov. sp. nov. is proposed, with aceae fam. nov. The type strain is strain D2-41 (=KACC 17930=DSM 101875).