Streptomyces hokutonensis sp. nov., a novel actinomycete isolated from the strawberry root rhizosphere.

A polyphasic approach was used to determine the taxonomic position of actinomycete strain R1-NS-10(T), which was isolated from a sample of strawberry root rhizosphere obtained from Hokuto, Yamanashi, Japan. Strain R1-NS-10(T) was Gram-staining-positive and aerobic, and formed brownish-white aerial mycelia and grayish-brown substrate mycelia on ISP-2 medium. The strain grew in the presence of 0-5% (w/v) NaCl and optimally grew without NaCl. The strain grew at pH 5-8, and the optimum for growth was pH 7. The optimal growth temperature was 30 °C, but the strain grew at 5-37 °C. Whole-cell hydrolysates of strain R1-NS-10(T) contained A2pm, galactose, mannose and rhamnose. The predominant menaquinones were MK-9(H6) and MK-9(H8). The major cellular fatty acids were anteiso-C15:0 and iso-C16:0. Comparative 16S rRNA gene sequence analysis revealed that strain R1-NS-10(T) was most closely related to Streptomyces prunicolor NBRC 13075(T) (99.4%). The draft genome sequences of both strains were determined for characterization of genome sequence-related parameters such as average nucleotide identity (ANI) and the diversity of secondary metabolite biosynthetic gene clusters. DNA-DNA hybridization (DDH) and ANI values for both strains were below the species delineation cutoff, and differences in physiological and biochemical characteristics differentiated strain R1-NS-10(T) from its closest phylogenetic relative. On the basis of these data, we propose that strain R1-NS-10(T) (=NBRC 108812(T)=KCTC 29186(T)) should be classified as the type strain of a novel Streptomyces species named Streptomyces hokutonensis sp. nov.