Identification of Azospirillum strains at the genome level with total DNA restriction pattern analysis

Seventeen strains belonging to the genus Azospirillum were isolated from crop plant roots and characterized following routine morphological and physiological methods without obtaining a definite species assignment. DNA restriction pattern analysis was therefore performed on those strains and on 9 reference strains belonging to Azospirillum lipoferum, Azospirillum brasilense and Azospirillum amazonense. Fragments obtained with endonuclease Bg/II digestion were separated with PAGE and stained with silver nitrate. An internal standard was used to rescale the separation profiles, thereby permitting the comparison of samples from different gels. Each pattern was found to be unique, allowing the distinction of single strains. UPGMA analysis, yielding clusters of band patterns, was utilized to assign strains to a species. Restriction pattern analysis is therefore suggested for the routine identification of azospirilla.