Protective Effect of the Outer Membrane of Escherichia coli JE1011 and Its Mutants against the Antimicrobial Action of Cholate

The correlation among the sensitivity to sodium chloride or cholate, the variation of succinate dehydrogenase activity caused by cholate and the protective effect of the outer membrane against the antibacterial action of cholate was investigated using E. coli JE 1011 and its mutants.These bacteria were classified into cholate-sensitive and cholate-resistant strains. The cholate-sensitive strains had a high tolerance for sodium chloride, but the salt tolerance was markedly weakened by cholate. On the other hand, the salt tolerance of the cholate-resistant strains was relatively low, but was not weakened by cholate.Succinate dehydrogenase activities of the cholate-sensitive strains were inhibited by cholate, though the activities of the cholate-resistant strains were activated by it.The outer membrane of the cholate-resistant strains contained b-, c- and d-protein, regarded as major proteins in the membrane of E. coli, but the membrane of the cholatesensitive strains lacked one or more among these proteins. These results suggest that major proteins in the outer membrane exhibit a protective effect against the antibacterial action of cholate.