Agglutination of Xanthomonas campestris pv. citri, a causal pathogen of citrus canker, by proteinaceous components from citrus leaves.

Proteinaceous components which agglutinated unwashed bacterial cells of Xanthomonas campestris pv. citri and its extracellular polysaccharides (EPS), but not washed cells and unwashed EPS-nonproducing mutant cells, were isolated from citrus leaves of Citrus unshiu, C. natsudaidai and C. reticulata, forming fibrous materials. The agglutinin was prepared by extraction with HCl-acidic water (pH 4.0) from homogenate of the leaves followed by precipitation with 50%-saturated ammonium sulfate. This agglutinin was heat and protease labile, insensitive to various salts except higher concentration than 100mM, and was inhibited at pH higher than 6.0. The Similar agglutination of unwashed cells and EPS of other xanthomonads (X. campestris pv. campestris and X. campestris pv. phaseoli), but not that of pseudomonads and erwiniae, was also demonstrated. Of 18 sugars tested, only D-glucosamine (25mM) showed a potential activity to inhibit the agglutination of X. campestris pv. citri, but not that of other xanthomonads.