Micromonospora thermarum sp. nov., an actinobacterium isolated from hot spring soil

An actinomycete, designated strain HSS6-12(T), was isolated from hot spring sediment collected from Ranong province, Thailand. The strain showed taxonomic characteristics consistent with those of members of the genus Micromonospora. HSS6-12(T) produced a single spore directly on the substrate mycelium, and no aerial mycelium was detected. The isomer of diamino acid presented in cell wall peptidoglycan was meso-diaminopimelic acid. Arabinose, xylose, glucose, and ribose were detected in whole-cell hydrolysates. MK-10(H-4), MK-9(H-4), and MK-10(H-6) were major menaquinones. Major cellular fatty acids were iso-C-16:0, iso-C-15:0, and iso-C-17:0. Phospholipid profile was composed of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylinositol, and phosphatidylinositolmannosides. 16S rRNA gene analysis revealed that HSS6-12(T) shared the highest 16S rRNA gene sequence similarity with Micromonospora inositola DSM 43819(T) (99.3%). In contrast, the genome analysis showed that HSS6-12(T) formed a tight taxonomic position in a phylogenomic tree with Micromonospora endolithica DSM 44398(T). Moreover, the average nucleotide identity-blast, the digital DNA-DNA hybridization, and the average amino acid identity values between HSS6-12(T) and M. inositola DSM 43819(T) and M. endolithica DSM 44398(T) were 83.1-84.0%, 27.5-28.7%, and 80.4-82.2%, respectively, indicating that HSS6-12(T) was different species with both closely related Micromonospora-type strains. In addition, HSS6-12(T) could be discriminated from its closely related type strains by many physiological and biochemical characteristics. Thus, HSS6-12(T) could be considered a novel species of the genus Micromonospora, and the name Micromonospora thermarum is proposed for the strain. The type strain is HSS6-12(T) (= BCC 41915(T) = JCM 17127(T)).