Streptomyces rhizoryzae sp. nov., isolated from paddy rhizosphere soil and formal proposal to reclassify Streptomyces albulus as a later heterotypic synonym of Streptomyces noursei.

Abstract

The taxonomic position of a novel actinomycete, designated strain RS10V-4T, was determined using a polyphasic approach. Strain RS10V-4T was isolated from paddy rhizosphere soil of rice plant (Oryzae sativa L.). The morphological, physiological and chemotaxonomic properties were consistent with its classification in the genus Streptomyces. On the basis of 16S rRNA gene sequence analysis, strain RS10V-4T belongs to the genus Streptomyces and had the highest sequence similarity to Streptomyces noursei NBRC 15452T (98.3 %). The G+C content of the genomic DNA was 73.8 %. Digital DNA-DNA hybridization and average nucleotide identity values between the genome sequences of strain RS10V-4T and S.noursei ATCC 11455T were lower than the recommendation threshold values for the recognition of species within the same genus. The whole-cell hydrolysates of strain RS10V-4 T contained ll -diaminopimelic acid as the diagnostic diamino acid and the whole-cell sugars were glucose and ribose. The predominant menaquinones were MK-9(H6) and MK-9(H8). The predominant cellular fatty acids (>10 %) were iso-C16 : 0, anteiso-C15 : 0, iso-C14 : 0 and iso-C15 : 0. The polar lipids of strain RS10V-4T contained diphosphatidylglycerol, hydroxyphosphatidylethanolamine, phosphatidylethanolamine, phosphatidylinositol, an unidentified aminolipid, two unidentified lipids and an unidentified phospholipid. On the basis of these phenotypic and genotypic characteristics, it is supported that strain RS10V-4T represents a novel species of the genus Streptomyces, for which the name Streptomyces rhizoryzae sp. nov. is proposed. The type strain is RS10V-4T (=TBRC 15167T=NBRC 115345T). In addition, the comparison of the whole genome sequences and phenotypic features suggested that S. noursei and S. albulus belong to the same species. Therefore, it is proposed that S. albulus is reclassified as a later heterotypic synonym of S. noursei.