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

Abstract

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-CX67T, belonged to the genus Rhodococcus and formed a cluster with Rhodococcus maanshanensis DSM 44675T, Rhodococcus kronopolitis NEAU-ML12T and Rhodococcus tukisamuensis JCM 11308T (98.3, 98.1 and 97.7% gene sequence similarity, respectively). The major fatty acids were C16 : 0, 10-methyl C18 : 0, C18 : 1 ω9c and C16 : 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-CX67T was 64.6 mol%. Strain NEAU-CX67T exhibited low average nucleotide identity and digital DNA–DNA hybridization values with R. maanshanensis DSM 44675T (92.1 and 45.4 %) and R. tukisamuensis JCM 11308T (81.9 and 24.4 %). On the basis of results of phylogenetic, genotypic, physiological and chemotaxonomic analysis, strain NEAU-CX67T 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-CX67T (=DSM 107701T=CCTCC AB 2018233T).