Abstract
A novel Gram-stain positive, aerobic, non-motile bacterial strain, designated Z1T, 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 Z1T belongs to the genus Rhodococcus and clustered with Rhodococcus maanshanensis DSM 44675T (99.2%, sequence similarity) and Rhodococcus tukisamuensis JCM 11308T (97.9%), respectively. However, the DNA–DNA hybridizations between strain Z1T and R. maanshanensis DSM 44675T and R. tukisamuensis JCM 11308T were both less than 70%. The optimal growth temperature and pH for strain Z1T 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 C16:0, 10-methyl C18:0 and C18:1ω9c. 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 Z1T 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 Z1T (= CGMCC 1.13630T = DSM 107227T).
Highlights
The genus Rhodococcus of the family Nocardiaceae of the order Corynebacteriales (Jones and Goodfellow 2012), belonging to the phylum Actinobacteria, was first described by Zopf (1891), refined by Goodfellow and Alderson (1977) and emended subsequently by Goodfellow et al (1998)
Members of the genus Rhodococcus are characterised by the presence of MK-8(H2) and/or MK-8(H4) as the predominant menaquinones; straight-chain saturated, monounsaturated and branched-chain fatty acids as the major fatty acids; phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylinositol and phosphatidylinositol mannosides as major components of the polar lipids
Scanning electron micrographs of strain Z1T at different time intervals showed that the cells follow a distinct rod-coccus cycle during growth stages, which is consistent with its assignment to the genus Rhodococcus (Supplementary Fig. S1)
Summary
The genus Rhodococcus of the family Nocardiaceae of the order Corynebacteriales (Jones and Goodfellow 2012), belonging to the phylum Actinobacteria, was first described by Zopf (1891), refined by Goodfellow and Alderson (1977) and emended subsequently by Goodfellow et al (1998). The DNA–DNA hybridizations between strain Z1T and R. maanshanensis DSM 44675T and R. tukisamuensis JCM 11308T were both less than 70%. Based on a comparative analysis of phenotypic and genotypic characteristics, in combination with DNA–DNA hybridization results, strain Z1T 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.
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