Degradation studies on Escherichia coli capsular polysaccharides by bacteriophages.

The serologically and structurally related Eschrichia coli capsular polysaccharides (K antigens) K13, K20, and K23 were found to be depolymerized by the bacteriophages phi K13 and phi K20 to almost similar oligomer profiles as shown by polyacrylamide gel electrophoresis. The phage-polysaccharide interactions were followed by an increase of reducing 2-keto-3-deoxyoctulosonic acid due to a phage-associated glycanase that catalyzed the hydrolytic cleavage of common beta-ketopyranosidic 2-keto-3-deoxyoctulosonic acid linkages. The related E. coli K antigens K18, K22, and K100 as well as the Haemophilus influenzae type b capsular polysaccharide were degraded by bacteriophage phi K100 with different efficacy. It is suggested that phi K100 enzymatically cleaves ribitol-5-phosphate bonds as the only structural feature present in all the polysaccharides investigated.