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

An actinobacterium strain, PPF5-17T, was isolated from hot spring soil collected from Chiang Rai province, Thailand. The strain exhibited morphological and chemotaxonomic properties similar to those of members of the genus Micromonospora. Colonies of PPF5-17T were strong pinkish red and turned black after sporulation in ISP 2 agar medium. Cells formed single spores directly on the substrate mycelium. Growth was observed from 15 to 45 °C and at pH 5-8. Maximum NaCl concentration for growth was 3 % (w/v). PPF5-17T was found to have meso-diaminopimelic acid, xylose, mannose and glucose in the whole-cell hydrolysate. Diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylinositol and phosphatidylinositolmannosides were observed as the membrane phospholipids. MK-10(H6), MK-9(H6), MK-10(H4) and MK-9(H4) were the major menaquinones. The predominant cellular fatty acids were iso-C15 : 0, iso-C17 : 0, anteiso-C17 : 0 and iso-C16 : 0. PPF5-17T shared the highest 16S rRNA gene sequence similarity with Micromonospora fluminis LMG 30467T (99.3 %). A genome-based taxonomic study revealed that PPF5-17T was closely related to Micromonospora aurantinigra DSM 44815T in the phylogenomic tree with an average nucleotide identity by blast (ANIb) of 87.7 % and a digital DNA-DNA hybridization (dDDH) value of, 36.1 % which were below the threshold values for delineation of a novel species. Moreover, PPF5-17T could be distinguished from its closest neighbours, M. fluminis LMG 30467T and M. aurantinigra DSM 44815T, with respect to a broad range of phenotypic properties. Thus, PPF5-17T represents a novel species, for which the name Micromonospora solifontis sp. nov. is proposed. The type strain is PPF5-17T (= TBRC 8478T = NBRC 113441T).