An actinobacterial strain designated MMS20-R1-14T was isolated from a riverside soil sample. Colonies on agar plates were orange to strong orange brown in colour, which later became black. The cells grew at 10-40 °C (optimum, 37 °C), pH 5.0-11.0 (pH 8.0) and in the presence of 0-4 % NaCl (1 %). The 16S rRNA gene sequence of strain MMS20-R1-14T showed highest similarities to Micromonospora wenchangensis CCTCC AA 2012002T (99.51 %) and Micromonospora rifamycinica AM105T (99.37 %). The orthoANI values between strain MMS20-R1-14T and the two type strains were 95.72 and 90.99 %, and the digital DNA-DNA hybridization values were 63.6 and 40.8 %, respectively, thus confirming the distinction of strain MMS20-R1-14T from its mostly related species. The DNA G+C content of strain MMS20-R1-14T was 72.9 mol%. The strain contained meso-diaminopimelic acid as the major cell-wall amino acid, and the characteristic whole-cell sugars were arabinose, xylose, glucose, ribose and rhamnose. The main cellular fatty acids were C18 : 1 ω9c, iso-C15 : 0 and iso-C16 : 0, the diagnostic polar lipids were diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine, and the predominant menaquinones were MK-10(H4) and MK-10(H6), all of which were consistent with those of Micromonospora. Strain MMS20-R1-14T showed antimicrobial activity against a range of bacterial and yeast species. The genome of the strain was found to contain 33 potential biosynthetic gene clusters for secondary metabolites, thus showing a high potential as a producer of bioactive compounds. On the basis of these phenotypic, genotypic and chemotaxonomic data, strain MMS20-R1-14T merits recognition as representing a novel species of the genus Micromonospora, for which the name Micromonospora humida sp. nov. (type strain=MMS20 R1-14T=KCTC 49541T=JCM 34494T) is proposed.
Keywords: Micromonospora humida sp. nov.; antimicrobial potential; biosynthetic gene cluster; riverside soil.