CONTRACTILE-TAILED BACTERIOPHAGES ADSORB TO ESCHERICHIA-COLI O128AB LIPOPOLYSACCHARIDE THAT IS ALTERED BY LARGE PLASMIDS TO PROVIDE RECEPTORS AND LIPOPOLYSACCHARIDE HETEROGENEITY WITHIN THE SEROGROUP

The verotoxigenic Escherichia coli strain H.I.8 (originally O128:B12, now not typeable) contained a ColB+M plasmid and two morphologically i dentical temperate bacteriophages (H18A and H18B). Both phages were O1 28ab specific, using the lipopolysaccharide O side chains of susceptib le clinical isolates as receptors. SDS polyacrylamide gel electrophore sis with silver staining of O128ab lipopolysaccharide revealed four di stinct types of ladder with different interband spacings. No specifici ty was found between ladder type and sensitivity to either phage. One of the numerous large plasmids present in O128ab isolates was found to modify the structure of the lipopolysaccharide O side chains to provi de phage receptors.