Spirillospora tritici sp. nov., a Novel Actinomycete Isolated from Rhizosphere Soil of Triticum aestivum L.

A Gram-positive, aerobic actinomycetes, designated strain SJ 21T, was isolated from the rhizosphere soil of Triticum aestivum L. collected from Langfang, Hebei Province, Central China. Strain SJ 21T with weak antifungal activity also contained genes (involved in antibiotics biosynthesis) of the nonribosomal peptide synthetases (NRPS), ketosynthase (KS) and methyl malonyl transferase domains (PKS-I) as well as KSα and KSβ domains (PKS-II). A polyphasic taxonomic study was carried out to establish the status of strain SJ 21T. The strain formed spherical spore vesicles (7.0-8.9 µm) consisting of coiled and branched chains on aerial mycelia. 16S rRNA gene sequence similarity studies showed that strain SJ 21T belongs to the genus Spirillospora and formed a distinct branch with its closest neighbour Spirillospora albida IFO 12248T (98.7%). The morphological and chemotaxonomic properties of the strain are also consistent with those members of the genus Spirillospora. DNA-DNA hybridization experiments and phenotypic tests were carried out between strain SJ 21T and S. albida, which further clarified their relatedness and demonstrated that SJ 21T could be distinguished genomically from S. albida. Therefore, the strain is considered to represent a novel species of the genus Spirillospora, for which the name Spirillospora tritici sp. nov. is proposed. The type strain is SJ 21T (=CGMCC 4.7420T =JCM 32390T).