Enterobacter oryzae sp. nov., a nitrogen-fixing bacterium isolated from the wild rice species Oryza latifolia

Twelve facultatively anaerobic, endophytic diazotrophs were isolated from surface-sterilized roots of the wild rice species Oryza latifolia and characterized by phenotypic and molecular methods. Six isolates were grouped together as group A by phenotypic characters, and this grouping was confirmed by SDS-PAGE whole-cell protein patterns and insertion sequence-based PCR (IS-PCR) methods. Phylogenetic analysis of the 16S rRNA gene sequence indicated that group A, represented by strain Ola 51(T), is closely related to Enterobacter radicincitans D5/23(T) (98.9 % similarity, except that E. radicincitans D5/23(T) has a 70 bp insertion) and Enterobacter cloacae (98.0 % similarity to the type strain). rpoB gene sequence analysis also showed strain Ola 51(T) has the highest sequence similarity to E. radicincitans DSM 16656(T) (98.3 %), but supported the distinct position. Biological and biochemical tests, protein patterns, genomic DNA fingerprinting, antibiotic resistance and comparison of cellular fatty acids showed differences among group A, E. radicincitans DSM 16656(T) and E. cloacae ATCC 13047(T). DNA-DNA hybridization distinguished strain Ola 51(T) from closely phylogenetically related Enterobacter species. Based on these data, the novel species Enterobacter oryzae sp. nov. is proposed, with strain Ola 51(T) (=LMG 24251(T) =CGMCC 1.7012(T)) as the type strain.