Genetic analysis of functions involved in adhesion of Pseudomonas putida to seeds

Many agricultural uses of bacteria require the establishment of efficient b acterial populations in the rhizosphere, for which colonization of plant se eds often constitutes a critical first step. Pseudomonas patina KT2440 is a strain that colonizes the rhizosphere of a number of agronomically importa nt plants at high population densities. To identify the functions involved in initial seed colonization by P. putida KT2440, me subjected this strain to transposon mutagenesis and screened for mutants defective in attachment to corn seeds. Eight different mutants were isolated and characterized. Whi le all of them showed reduced attachment to seeds, only two had strong defe cts in their adhesion to abiotic surfaces (glass and different plastics). S equences of the loci affected in all eight mutants were obtained. None of t he isolated genes had previously been described in P. putida, although four of them showed clear similarities with genes of known functions in other o rganisms. They corresponded to putative surface and membrane proteins, incl uding a calcium-binding protein, a hemolysin, a peptide transporter, and a potential multidrug efflux pump. One other showed limited similarities with surface proteins, while the remaining three presented no obvious similarit ies with known genes, indicating that this study has disclosed novel functi ons.