Abstract:

Forty-three strains of endophytic nitrogen-fixing bacteria were obtained from wild rice Oryza alta, and grown on nitrogen-free medium. Their potential nitrogen-fixing ability was determined with the acetylene reduction method and a PCR amplification of the nifH gene fragment. The obtained isolates were grouped into six groups (I, II, III, IV, V, VI) based on their DNA patterns of IS-PCR and protein patterns of SDS-PAGE. The 16S rRNA gene sequence analysis identified representative strains, suggesting that group I belonged to Raoultella terrigena, group II to Klebsiella quasipneumoniae subsp. quasipneumoniae, group III to Burkholderia vietnamiensis, group IV to genus Enterobacter, group V to Pseudomonas mendocina, and group VI to Phytobacter diazotrophicus. A Biolog plate test showed strains from differing groups had significant differences in carbon source utilization, often clustering consistently within IS-PCR and SDS-PAGE patterns. The diversity of endophytic nitrogen-fixing bacteria in wild rice indicates that endophytic bacteria is strongly adaptable in obtaining both carbon and nitrogen from varying environments.

Key words: endophytic diazotrophs, diversity, eletrophoresis of whole cell protein patterns, fingerprinting patterns, clustering analysis