Effect of Constitutive Expression of the rapA1 Gene on Formation of Bacterial Biofilms and Growth-Stimulating Activity of Rhizobia

In order to investigate the effect of the RapA1 protein on growth-stimulating activity, biofilm formation, and root colonization by rhizobia, strains Rhizobium leguminosarum Pvu5, VSy12, Thy2, TPr4 and R. galegae 0702 were transformed with the pJN105TurboRapA1GFP vector, providing for constitutive expression of the rapA1 and gfp genes. Constitutive expression of the rapA1 gene was shown to result in more efficient biofilm formation on inert surfaces and to promote microcolony formation on plant root surfaces. Analysis of auxin production by wild and transformed strains revealed decreased auxin synthesis in all transformed strains, except for R. leguminosarum Thy2. Growth-stimulating activity of the wild and transformed strains did not correlate with the amount of auxins produced in vitro.