Interaction with lectins and differential wheat germ agglutinin binding of pyocin 103-sensitive and -resistant Neisseria gonorrhoeae

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Abstract
Strains of N. gonorrhoeae were treated with pyocin 611 131 (pyocin 103) from Pseudomonas aeruginosa PA103, and isogenic resistant variants were isolated. Wheat germ agglutinin (WGA) agglutinated all pyocin-sensitive, but not pyocin-resistant, strains. Binding of WGA to 3 pyocin-sensitive strains and their isogenic pyocin-resistant variants was examined quantitatively by using fluorescein-conjugated lectin. Pyocin-resistant strains maximally bound 1/3-1/8 the quantity of WGA bound by isogenic-sensitive strains. Linear Scatchard plots revealed homogeneous WGA-binding sites on 3 pyocin-sensitive strains and on 1 pyocin-resistant strain. Biphasic Scatchard plots, obtained with 2 pyocin-resistant strains, show that WGA-binding sites in these strains are heterogeneous. The number of WGA-binding sites for pyocin-sensitive organisms ranged from 8 .times. 105 to 1 .times. 106 sites/coccus and from 1 .times. 105 to 3 .times. 105 sites/coccus for pyocin-resistant strains. The apparent association constant for WGA binding to pyocin-sensitive strains ranged from 3 .times. 106 to 6 .times. 106 l/mol and from 6 .times. 106 to 1 .times. 107 l/mol for pyocin-resistant strains. Gonococcal lipopolysaccharide was shown to serve as the pyocin 103 receptor by inhibition of pyocin activity. Lipopolysaccharide from a pyocin 103-resistant strain was not able to inhibit pyocin 103 activity. Pyocin 103 resistance was correlated with a structural alteration involving N-acetylglucosamine residues in gonococcal lipopolysaccharide. Based on interactions with wheat germ, soybean and ricin lectins, a model of lipopolysaccharide in N. gonorrhoeae is presented.