We have isolated 576 endophytic bacteria from the leaves, stems, and roots of 10 rice cultivars and identi-
fied 12 ofthem as diazotrophic bacteria using a specific primer set of nif gene. Through 16S rDNAsequence
analysis, nifH genes were confirmed in the two species of Penibacillus, three species of Microbacterium,
three Bacillus species, and four species of Klebsiella. Rice seeds treated with these plant growth-promoting
bacteria (PGPB) showed improved plant growth, increased height and dry weight and antagonistic effects
against fungal pathogens. In addition, auxin and siderophore producing ability, and phosphate solubilizing
activity were studied for the possible mechanisms of plant growth promotion. Among 12 isolates
tested, 10 strains have shown higher auxin producing activity, 6 isolates were confirmed as strains with
high siderophore producing activity while 4 isolates turned out to have high phosphate-solubilizing
activity. These results strongly suggest that the endophytic diazotrophic bacteria characterized in this
study could be successfully used to promote plant growth and inducing fungal resistance in plants