Genetic Diversity of Endophytic Diazotrophs of the Wild Rice, Oryza alta and Identification of the New Diazotroph, Acinetobacter oryzae sp. nov.
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Thirty-three endophytic diazotrophs were isolated from surface-sterilized leaves, stem, and roots of wild rice Oryza alta. The SDS–PAGE profile of total protein and insertion sequence-based polymerase chain reaction (IS-PCR) fingerprinting grouped the isolates into four clusters (I–IV). The 16S rRNA gene sequence homology of the representative strains B21, B31, B1, and B23 of clusters I, II, III, and IV were assigned to Pseudomonas oleovorans (99.2% similarity), Burkholderia fungorum (99.4% similarity), Enterobacter cloacae (98.9% similarity), and Acinetobacter johnsonii (98.4% similarity), respectively. The results showed wide genetic diversity of the putative diazotrophic strains of the wild rice, O. alta, and the strains of cluster IV are the first report of nitrogen-fixing Acinetobacter species. The cell size, phenotypic characters, total protein profile, genomic DNA fingerprinting, DNA–DNA hybridization, and antibiotic resistance differentiated strain B23T from its closest relatives A. johnsonii LMG999T and Acinetobacter haemolyticus LMG996T. The DNA–DNA hybridization also distinguished the strain B23T from the closely related Acinetobacter species. Based on these data, a novel species, Acinetobacter oryzae sp. nov., and strain B23T (=LMG25575T = CGMCC1.10689T) as the type strain were proposed.