Agglutination of Pseudomonas phaseolicola by pectic polysaccharide from leaves of Phaseolus vulgaris

Abstract

A component of the acidic pectic polysaccharide fraction from leaves of Phaseolus vulgaris agglutinated cells of Race 1 isolates of Pseudomonas phaseolicola to a greater degree than cells of Race 2 isolates. Agglutinating activity was sensitive to endopolygalacturonase and periodate, but not to pectin methyl esterase or protease. In spite of the differential activity in vitro, the active pectic polysaccharide was obtained both from Phaseolus vulgaris cv. Red Mexican, resistant to Race 1, and cv. Canadian Wonder, susceptible to both races. Also, analysis showed that the uronic acid and neutral sugar content of the polysaccharides from the two cultivars were similar. This indicates that differential attachment of cells of the two races to pectic polysaccharides in plant cell walls in intercellular spaces of leaves was not responsible for the specific resistance of cv. Red Mexican to Race 1 isolates of Pseudomonas phaseolicola.