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)).

Automated summary

A new species of actinomycete, Micromonospora thermarum, was isolated from hot spring sediment in Ranong province, Thailand. The strain showed taxonomic characteristics consistent with members of the genus Micromonospora. The strain produced a single spore directly on the substrate mycelium and had unique physiological and biochemical characteristics compared to closely related strains.