Microbacterium oryzae sp. nov., an actinobacterium isolated from rice field soil.

A novel aerobic soil actinobacterium (strain MB10(T)) belonging to the genus Microbacterium was isolated from rice field soil samples collected from Jagatpur, Orissa, India. Cells were Gram-stain positive, short rod-shaped and motile. The strain was oxidase-negative and catalase-positive. Heterotrophic growth was observed at pH 5.0-11.0 and at 16-37 °C; optimum growth was observed at 28 °C and pH 7.0-9.0. The DNA G+C content was 71.6 mol%. Predominant cellular fatty acids of strain MB10(T) were iso-C14 : 0, anteiso-C15 : 0, C16 : 0, iso-C16 : 0 and anteiso-C17 : 0. Cell wall sugars were galactose, glucose and rhamnose. The major isoprenoid quinones were MK-9 (10 %), MK-10 (43 %) and MK-11 (36 %). The peptidoglycan represents the peptidoglycan type B2β. The polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phospholipid and unknown glycolipids. 16S rRNA gene sequence identity revealed the strain MB10(T) clustered within the radiation of the genus Microbacterium and showed 99.2 % similarity with Microbacterium barkeri DSM 20145(T). However, DNA-DNA similarity study was 37.0 % with Microbacterium barkeri DSM 20145(T), the nearest phylogenetic relative. On the basis of phenotypic and chemotaxonomic properties, 16S rRNA gene sequence analysis and DNA-DNA reassociation studies, it is proposed that strain MB10(T) represents a novel species of the genus Microbacterium, for which the name Microbacterium oryzae sp. nov. is proposed; the type strain is MB10(T) ( = JCM 16837(T) = DSM 23396(T)).