Chromosomally Coded Pili of Pseudomonas Syringae Pv. Phaseolicola Function as Adhesins in Early Steps of Halo Blight of Bean

Abstract

Pseudomonas syringae pv. phaseolicola is the causative agent of halo blight in the common bean (Phaseolus vulgaris L.). P. syringae pv. phaseolicola HB10Y is the original host of the lipid-containing bacteriophage 06 that initially attaches to the pili of the host cell. Bacteriophage resistant mutants of the bacterium were isolated and were in all cases found to have alterations in pilus expression. Efficiency of attachment of bacteria to the leaf surface of the non-cotyledon leaves of Phaseolus vulgaris L. cv. Prelude and Red Kidney was significantly higher for the super piliated phage resistant bacterial strain compared to the wild type phage sensitive parental strain whereas the nonpiliated variants did not attach to the leaf surface. In scanning electron microscopic studies, the piliated strains were found to attach to the stomata of the abaxial surface of the leaf. Nonpiliated strains showed a random distribution of cells at a much lower density than the piliated strains. When infecting young Red Kidney plants all the HBlOY strains caused symptoms if a bacterial suspension was injected in the leaf veins whereas only the piliated strains caused symptoms if infection was done by misting bacterial suspension followed by extensive misting of the plants with sterile M9 growth medium.KeywordsLeaf SurfaceCommon BeanBacterial SuspensionPlant Pathogenic BacteriumBean LeafThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.