Rhodococcus oryzae sp. nov., a novel actinobacterium isolated from rhizosphere soil of rice (Oryza sativa L.).

A Gram-stain-positive, non-motile, creamy-white actinobacterium, which has an elementary branching rod-coccus life cycle was isolated from the rhizosphere soil of rice (Oryza sativa L.) collected from Northeast Agricultural University in Harbin, Heilongjiang province, north-east PR China, and its taxonomic status was examined by using a polyphasic approach. Results from the 16S rRNA gene sequence study showed that the isolate, designated strain NEAU-CX67^T, belonged to the genus Rhodococcus and formed a cluster with Rhodococcus maanshanensis DSM 44675^T, Rhodococcus kronopolitis NEAU-ML12^T and Rhodococcus tukisamuensis JCM 11308^T (98.3, 98.1 and 97.7% gene sequence similarity, respectively). The major fatty acids were C_{16 : 0}, 10-methyl C_{18 : 0}, C_{18 : 1} ω9c and C_{16 : 1} ω7c. The polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol and phosphatidylinositol mannoside. The major isoprenoid quinone was MK-8(H₂). Whole-cell hydrolysates contained meso-diaminopimelic acid. Arabinose, galactose and ribose were detected as diagnostic sugars from whole-cell hydrolysates. Mycolic acids were detected. The genomic DNA G+C content of strain NEAU-CX67^T was 64.6 mol%. Strain NEAU-CX67^T exhibited low average nucleotide identity and digital DNA-DNA hybridization values with R. maanshanensis DSM 44675^T (92.1 and 45.4 %) and R. tukisamuensis JCM 11308^T (81.9 and 24.4 %). On the basis of results of phylogenetic, genotypic, physiological and chemotaxonomic analysis, strain NEAU-CX67^T is considered to represent a novel species of the genus Rhodococcus for which the name Rhodococcus oryzae sp. nov. is proposed. The type strain is NEAU-CX67^T (=DSM 107701^T=CCTCC AB 2018233^T).