Complementation analysis of mutants of the associative bacteria Azospirillum brasilense Sp245 and S27, defective in mobility and flagellation

Three mutants of Azospirillum brasilense Sp245 incapable of both formation of the polar flagellum (Fla-phenotype) and swarming in semisolid media (Swa-phenotype) were characterized. These mutants were shown to have lost the 85-MDa plasmid and to carry the Tn5-Mob transposon and pSUP5011 vector in different regions of their genomes. With the use of A. brasilense Sp245 gene bank, the capacity for both polar flagellum formation and swarming was restored in the above mutants and in the previously generated transposon mutants A. brasilense Sp245 and S27. The transconjugants obtained were only slightly motile in the liquid culture. In the gene bank of Sp245, the recombinant plasmids carrying wild-type fla/swa loci were identified.