An actinobacterial strain designated MMS20-HV4-12T, displaying a high hydrolytic potential for various substrates, was isolated from a riverside soil sample and characterized by polyphasic taxonomic analysis. Growth occurred at 10-37 °C (optimum, 30°C), with NaCl concentrations of 0-4 % (optimum, 0 %) and at pH 7-9 (optimum, pH 8). MMS20-HV4-12T was catalase-positive, oxidase-negative, rod-shaped and formed creamy white-coloured colonies. Based on the results of 16S rRNA gene sequence analysis, MMS20-HV4-12T was found to be mostly related to the type strains of Nocardioides alpinus (98.3 % sequence similarity), Nocardioides furvisabuli (98.1 %) and Nocardioides zeicaulis (98.0 %). MMS20-HV4-12T showed optimal growth on Reaoner's 2A agar, forming white-coloured colonies. The diagnostic polar lipid profile consisted of diphosphatidylglycerol, phosphatidylglycerol and phosphatidylinositol, the major fatty acids were iso-C16 : 0, C17 : 1 ω8c and 10-methyl-C17 : 0, the major isoprenoid quinone was MK-8(H4), the diagnostic cell-wall sugar was galactose, and the cell-wall diamino acid was ll-diaminopimelic acid. The genome of MMS20-HV4-12T was 4.47 Mbp in size with a G+C content of 72.9 mol%. The genome based analysis indicated low relatedness between MMS20-HV4-12T and all compared species of Nocardioides, as the highest digital DNA-DNA hybridization and the orthologous average nucleotide identity values were 26.8 and 83.8% respectively. Based on genotypic, phenotypic and phylogenomic characterization, MMS20-HV4-12T evidently represents a novel species of genus Nocardioides, for which the name Nocardioides okcheonensis sp. nov. (type strain=MMS20-HV4-12T=KCTC 49651T=LMG 32360T) is proposed.
Keywords: Nocardioides okcheonensis; actinobacterium; hydrolytic potential; riverside soil.