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 ).
(© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)