Quadrisphaera oryzae sp. nov., an endophytic actinomycete isolated from leaves of rice plant (Oryza sativa L.)

Abstract

A novel endophytic actinobacterium, designated strain RL12-1S^T, was isolated from surface-sterilized leaves of Oryza sativa L. collected from Roi Et province, Thailand. Taxonomic position of strain RL12-1S^T was studied using the polyphasic approach. Phylogenetic analyses base on the 16S rRNA gene sequences showed that strain RL12-1S^T belonged to the genus Quadrisphaera and was closely related to Quadrisphaera granulorum AG019^T (99.0%). The colony of strain RL12-1S^T was vivid orange. Growth occurred at a temperature between 17-37 °C and pH between 6.0-8.0. The strain contained meso-diaminopimelic acid and galactose, glucose, mannose, ribose and rhamnose in whole-cell hydrolysates. The predominant menaquinone was MK-8(H₂). The major fatty acids were C_16:1ω7c/C_16:1ω6c, C_16:0 and C_18:1ω7c. The polar lipids of the strain were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol and phosphatidylinositol mannosides. The DNA G + C content of genomic DNA was 76.1 mol%. Based on comparative analysis of physiological, biochemical and chemotaxonomic data, including DNA-DNA hybridization, strain RL12-1S^T represents a novel species of the genus Quadrisphaera, for which the name Quadrisphaera oryzae sp. nov. is proposed. The type strain is RL12-1S^T ( = TBRC 8486^T = NBRC 113447^T).