Diverse endophytic nitrogen-fixing bacteria isolated from wild rice Oryza rufipogon and description of Phytobacter diazotrophicus gen. nov. sp. nov.

Twenty-three nitrogen-fixing bacteria were isolated from surface-sterilized stems and roots of wild rice Oryza rufipogon. Four clusters were defined among these bacteria by SDS-PAGE protein patterns and further confirmed by IS-PCR finger-printing analysis. Phylogenetic analysis of 16S rRNA gene sequences showed that the representative strains LS 8 and LS 18 of cluster II formed a monophyletic group sharing 94.0–97.3% similarities with defined enterobacterial species within the genera Salmonella, Citrobacter, Pantoea, Klebsiella, and Enterobacter. DNA–DNA hybridization, physiological, biochemical tests, and cell morphology also revealed that these strains could be differentiated from the related enterobacterial species. Based upon these results, we propose Phytobacter diazotrophicus gen. nov., sp. nov. to the bacterial group represented by strains LS 8 and LS 18. The type strain is LS 8T (=DSM 17806T = LMG 23328T = CGMCC 1.5339T). The DNA G+C content of strain LS 8T is 58.6 ± 0.5 mol%.