Microlunatus speluncae sp. nov., a novel actinobacterium isolated from a Karstic subterranean environment sample

A novel actinobacterial strain, designated SYSU K12189^T, was isolated from a soil sample collected from a Karst cave in Xingyi county, Guizhou province, south-western China. The taxonomic position of the strain was investigated using a polyphasic approach. Cells of the strain were observed to be aerobic and Gram-stain positive. On the basis of 16S rRNA gene sequence similarities and phylogenetic analysis, strain SYSU K12189^T is closely related to the type strains of the genus Microlunatus, Microlunatus parietis 12-Be-011^T (98.5% sequence similarity), Microlunatus nigridraconis CPCC 203993^T (98.4%) and Microlunatus cavernae YIM C01117^T (96.6%), and is therefore considered to represent a member of the genus Microlunatus. DNA-DNA hybridization values between strain SYSU K12189^T and related type strains of the genus Microlunatus were < 70%. In addition, LL-diaminopimelic acid was found to be the diagnostic diamino acid in the cell wall peptidoglycan. The major isoprenoid quinone was identified as MK-9(H₄), while the major fatty acids (> 10%) were found to be anteiso-C_15:0, iso-C_15:0, iso-C_16:0 and iso-C_14:0. The polar lipids were found to contain diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol, three glycolipids and two unidentified lipids. The genomic DNA G+C content of strain SYSU K12189^T was determined to be 69.4 mol%. On the basis of phenotypic, genotypic and phylogenetic data, strain SYSU K12189^T is concluded to represent a novel species of the genus Microlunatus, for which the name Microlunatus speluncae sp. nov. is proposed. The type strain is SYSU K12189^T (= KCTC 39847^T = DSM 103947^T).