Nocardia aurea sp. nov., a novel actinobacterium isolated from a karstic subterranean environment.

A novel actinobacterium, designated strain SYSU K10002, 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 aerobic and Gram-stain-positive. On the basis of 16S rRNA gene sequence similarities and phylogenetic analysis, strain SYSU K10002 was most closely related to the type strains of Nocardiaaltamirensis NBRC 108246 (99.0 % sequence similarity) and Nocardiatenerifensis NBRC 101015 (98.8 %) and is therefore considered to represent a member of the genus Nocardia. DNA-DNA hybridization values between strain SYSU K10002 and the closely related type strains of the genus Nocardia were less than 70 %. In addition, meso-diaminopimelic acid was the diagnostic diamino acid in the cell-wall peptidoglycan. The whole-cell sugars were arabinose, ribose and galactose. The major isoprenoid quinone was MK-8(H4,ω-cycl), while the major fatty acids (>10 %) were C16 : 0, C18 : 1ω9c and C18 : 0 10-methyl. The polar lipids contained diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol, phosphatidylinositol mannoside and an unidentified glycolipid. Mycolic acids were present. The genomic DNA G+C content of strain SYSU K10002 was 67.4 mol%. On the basis of phenotypic, genotypic and phylogenetic data, strain SYSU K10002 represents a novel species of the genus Nocardia, for which the name Nocardiaaurea sp. nov. is proposed. The type strain is SYSU K10002 (=KCTC 39849=DSM 103986).