Effect of O-acetylation of O antigen of Escherichia coli lipopolysaccharide on the nonspecific barrier function of the outer membrane

Comparison of the methods for determination of permeability of the outer membrane of Escherichia coli strain 4s and its mutants was carried out. The studied isogenic strains E. coli 4s were obtained by selection of spontaneous mutants according to their sensitivity to bacteriophages recognizing the surface O antigen of the outer membrane lipopolysaccharide as a primary receptor. The variants differed in the presence and (de)acetylation of the lipopolysaccharide O antigen. A peptide antibiotic polymyxin, plasmid DNA, and lysozyme were used as probes. The role of acetylation of the O antigen of the lipopolysaccaride of E. coli outer membrane in modification of its permeability (correlating with bacteriophage sensitivity of the cells) was confirmed. Kinetic analysis using lysozyme was shown to be the optimal method for determination of the barrier function of E. coli outer membrane.