A novel ligninase-producing actinomycete, designated strain NEAU-G4T, was isolated from a soil sample and subjected to a polyphasic taxonomic study to establish its status. According to 16S rRNA gene sequence comparisons, the isolate was identified as a member of the genus Nocardia, with the highest sequence similarity to Nocardia ignorata DSM 44496T (99.2 %). The whole-cell sugars contained galactose and arabinose. The amino acid of the cell wall was determined to be meso-diaminopimelic acid. The major fatty acids (>10 %) were C16 : 0, C18 : 1 ω9c, C18 : 0 and C16 : 1 ω7c. The predominant menaquinone was identified as MK-8(H6, ω-cycl). The major polar lipids consisted of diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylinositol. Strain NEAU-G4T had a draft genome size of 6 405 167 bp, annotated with 5815 protein-coding genes. The DNA G+C content was 67.6 mol%. Phylogenetic analysis using the 16S rRNA gene and whole-genome sequences showed that strain NEAU-G4T formed a stable phyletic line with N. ignorata DSM 44496T. The digital DNA-DNA hybridization and average nucleotide identity values between them were 63.7 % (60.8-66.5 %) and 95.5 %, respectively. Moreover, genomic analysis indicated that strain NEAU-G4T had the potential to degrade lignin and produce bioactive compounds. On the basis of genotypic analysis, physiological data, as well as phenotypic and chemotaxonomic characterizations, it is concluded that the organism be classified as representing a novel species of the genus Nocardia, for which the name Nocardia rosealba sp. nov. is proposed. The type strain is NEAU-G4T (=CCTCC AA 2020038T=DSM 111936T).
Keywords: 16S rRNA gene sequence; Nocardia rosealba sp. nov.; polyphasic taxonomy; whole-genome analysis.