Rhodococcus daqingensis sp. nov., isolated from petroleum-contaminated soil

A novel Gram-stain positive, aerobic, non-motile bacterial strain, designated Z1^T, was isolated from a sample of petroleum-contaminated soil collected in Daqing, Heilongjiang province, China and characterised with a series of taxonomic approaches. The morphological and chemotaxonomic properties of the isolate were typical of those of members of the genus Rhodococcus. Phylogenetic analyses based on 16S rRNA gene sequences showed that strain Z1^T belongs to the genus Rhodococcus and clustered with Rhodococcus maanshanensis DSM 44675^T (99.2%, sequence similarity) and Rhodococcus tukisamuensis JCM 11308^T (97.9%), respectively. However, the DNA-DNA hybridizations between strain Z1^T and R. maanshanensis DSM 44675^T and R. tukisamuensis JCM 11308^T were both less than 70%. The optimal growth temperature and pH for strain Z1^T were found to be at 28 °C and at pH 7.0. The peptidoglycan was found to contain meso-diaminopimelic acid; arabinose, galactose and glucose were detected as diagnostic sugars. The main polar lipids were identified as diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol, phosphatidylinositol mannoside and an unidentified lipid; MK-8(H₂) was found as the major menaquinone. The major fatty acids were identified as C_16:0, 10-methyl C_18:0 and C_18:1ω9c. Mycolic acids were found to be present. The G + C content of the genomic DNA was determined to be 66.7 mol%. Based on a comparative analysis of phenotypic and genotypic characteristics, in combination with DNA-DNA hybridization results, strain Z1^T can be distinguished from the type strains of its two close neighbours as a novel species of the genus Rhodococcus, for which the name Rhodococcus daqingensis sp. nov. is proposed. The type strain is Z1^T (= CGMCC 1.13630^T = DSM 107227^T).