Ultrastructure of the Interaction of Cells of Pseudomonas phaseolicola with Cell Walls of a Resistant and Susceptible Bean Cultivar

Cells of Pseudomonas phaseolicola were observed entrapped against plant cell walls in both susceptible (Red Kidney) and resistant (Red Mexican) cultivars of French bean (Phaseolus vulgaris). After staining of samples with ruthenium red for electron microscopy pectic polysaccharide within plant cell walls became particularly well contrasted as did fibrillar material connecting bacteria to the plant cell walls. In places this fibrillar material appeared to emanate from the pectic polysaccharide in the plant cell wall, and the plant cell wall surface was eroded at such points. Ruthenium red also stains acidic, bacterial extracellular polysaccharide (EPS) and some of the fibrillar material in intercellular spaces is probably from this source. It is possible that bacteria become attached through an interaction between EPS and Pectic polysaccharide in plant cell walls.