Streptomyces gramineus sp. nov., an antibiotic-producing actinobacterium isolated from bamboo (Sasa borealis) rhizosphere soil.

Two actinobacterial strains, JR-43T and JR-4, were isolated from bamboo (Sasa borealis) rhizosphere soil. The isolates produced grey aerial mycelium and a yellow soluble pigment on ISP 4. Microscopic observation revealed that strains JR-43T and JR-4 produced rectiflexibiles spore chains with spiny surfaces. Both isolates had antibacterial activity against plant-pathogenic bacteria, such as Xanthomonas campestris LMG 568T and Xanthomonas axonopodis pv. vesicatoria LMG 905. The isolates contained iso-C14:0, iso-C15:0, anteiso-C15:0 and iso-C16:0 as the major fatty acids and MK-9(H6) and MK-9(H8) as the major isoprenoid quinones. Phylogenetic analysis of the 16S rRNA gene sequences of strains JR-43T and JR-4 showed that they grouped within Streptomyces cluster II and had highest sequence similarity to Streptomyces seoulensis NBRC 16668T and Streptomyces recifensis NBRC 12813T (both 98.2 % 16S rRNA gene sequence similarity). DNA-DNA relatedness between strain JR-43T and S. seoulensis NBRC 16668T and S. recifensis NBRC 12813T ranged from 31.42 to 42.92 %. Based on DNA-DNA relatedness and morphological and phenotypic data, strains JR-43T and JR-4 could be distinguished from the type strains of phylogenetically related species. They are therefore considered to represent a novel species of the genus Streptomyces, for which the name Streptomyces gramineus sp. nov. is proposed. The type strain is JR-43T (=KACC 15079T=NBRC 107863T). Strain JR-4 (=KACC 15078= NBRC 107864) is a reference strain [corrected].