Streptomyces mahasarakhamensis sp. nov., an Endophytic Actinobacterium Isolated from Jasmine Rice and its Potential as plant Growth Promoter.

Abstract

Two endophytic actinobacteria, strains MK5T and MK7, were isolated from the surface-sterilized root ofJasmine rice(Oryza sativaKDML 105). These strains were aerobic actinobacteria with a well-developed substrate and aerial mycelia that formed spiral spore chains. The type strains that shared the high 16S rRNA gene sequence similarity with both strains wereStreptomyces naganishiiNBRC 12892T (99.4%),"Streptomyces griseicoloratus"TRM S81-3T (99.2%),andStreptomyces spiralisNBRC 14215T (98.9%).Strains MK5T and MK7 are the same species sharing a digital DNA-DNA hybridization (dDDH) value of 95.3% and a 16S rRNA gene sequence similarity of 100%. Chemotaxonomic data confirmed the affiliation of strains MK5T and MK7 to the genusStreptomyces.Strains MK5T and MK7 contained MK-9(H4) as amajormenaquinone; the whole-cell sugar of both strains was galactose and glucose. The strain MK5T shared 93.4% average nucleotide identity (ANI)-Blast, 95.5% ANI-MUMmer, 93% average amino acid identity, and 61.3% dDDH withS. spiralisNBRC 14215T. The polyphasic approach confirmed that strain MK5T represents a novel species, and the nameStreptomyces mahasarakhamensissp. nov. is proposed. The type strain is MK5T (= TBRC 17754 = NRRL B-65683). Genome mining, using an in silico approach and searching biosynthesis gene clusters of strains MK5T and MK7, revealed that the genomes contained genes encoding proteins relating to plant growth promotion, bioactive compounds, and beneficial enzymes. Strains MK5T and MK7 could produce indole acetic acid and solubilize phosphatein vitro.