Mutations conferring bacteriocin resistance in Pseudomonas syringae reduce virulence toward host plants.
K. HOCKETT (1), E. Carlson (2), D. Baltrus (3) (1) University of Arizona, School of Plant Sciences, U.S.A.; (2) University of Arizona, Dept. of Ecology and Evolutionary Biology, U.S.A.; (3) University of Arizona, School of Plant Sciences, U.S.A.

Plant-associated bacteria live in complex microbial communities, where they compete for limited nutrients. To combat competitors, many plant-associated bacteria produce bacteriocins, protein-based antibacterials. As bacteriocins are expected to influence microbial community structure, including selecting for resistant mutants, we wanted to determine whether such resistance mutations would result in altered plant-microbe interactions. Using Pseudomonas syringae as a model system, we recovered numerous mutants resistant to a bacteriophage-derived bacteriocin (tailocin), which we’ve recently described. We identified resistance mutations by whole-genome sequencing. All mutations occurred in genes with predicted function in lipopolysaccharide (LPS) biosynthesis. The majority of mutations occurred in genes putatively involved in the synthesis of the O-specific oligosaccharide subunit. We tested the effect of these mutations in two different strains, P. syringae pv. glycinea (pathogen of soybean) and P. syringae pv. phaseolicola (pathogen of green bean). In both pathosystems, the mutant strains exhibited 10-fold reductions in apoplastic populations compared to the wild type strains, 24 hours after infiltration into their respective host plants. This reduction was similar in magnitude to that of mutants disrupted in type III secretion. These results indicate that antagonistic microbial interactions influence subsequent plant-microbe interactions.

Abstract Number: C4-4, P3-86
Session Type: Concurrent