A New Bacterial Agglutinin from Soybean: II. EVIDENCE AGAINST A ROLE IN DETERMINING PATHOGEN SPECIFICITY

The activity of a bacterial agglutinin from soybean seed [Glycine max (L.) Merrill cv. Clark] against two bacterial pathogens, Pseudomonas glycinea (causal agent of bacterial blight) and Xanthomonas phaseoli var. sojensis (causal agent of bacterial pustule) was determined. The agglutinin was active against several strains of X. phaseoli var. sojensis grown on nutrient agar, but there was no correlation between pathogenicity and agglutination. Agglutination was affected by the age of the bacterial cells and the growth medium used. None of seven strains of P. glycinea was agglutinated.Bacterial agglutination was inhibited by both purified lipopolysaccharide and extracellular polysaccharide from five strains of X. phaseoli var. sojensis. The lipopolysaccharides and extracellular polysaccharides from other species of bacteria were ineffective.Ultrastructural studies showed that an avirulent strain of X. phaseoli var. sojensis was attached to leaf mesophyll cell walls of the susceptible cultivar Clark by 34 hours after vacuum infiltration. Cells of this avirulent strain were enveloped by fibrillar and granular material at the mesophyll cell wall. In contrast, cells of a virulent strain were not attached or enveloped, and they remained free to multiply in the intercellular spaces.