different methods for isolation and preliminary identification of azotobacter

plant growth promoting rhizobacteria (pgpr) are known to influence plant growth by various director indirect mechanisms. thirty–two strains were isolated from 15 soils sampled in central iran, byusing and comparing three different methods. the screening of soil samples by means of soil paste–plate method combined with isolation on mannitol agar proved to be the best strategy in terms ofreliability and selectivity. these test isolates were biochemically characterized. these isolates werescreened in vitro and identified by using bibi(bioinformatics bacterial identification tool). bibi wasdesigned to automate dna sequence analysis for bacterial identification in the different fields. bibirelies on the use of blast and clustal w programs applied to different subsets of sequencesextracted from genbank. these sequences are filtered and stored in a new database, which is adaptedto bacterial identification.