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

A novel endophytic actinobacterium, designated strain RL12-1ST, was isolated from surface-sterilized leaves of Oryza sativa L. collected from Roi Et province, Thailand. Taxonomic position of strain RL12-1ST was studied using the polyphasic approach. Phylogenetic analyses base on the 16S rRNA gene sequences showed that strain RL12-1ST belonged to the genus Quadrisphaera and was closely related to Quadrisphaera granulorum AG019T (99.0%). The colony of strain RL12-1ST 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 C16:1ω7c/C16:1ω6c, C16:0 and C18:1ω7c. 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 RL12-1ST represents a novel species of the genus Quadrisphaera, for which the name Quadrisphaera oryzae sp. nov. is proposed. The type strain is RL12-1ST ( = TBRC 8486T = NBRC 113447T).