The Influence of Bacteriocins on Resistance to Infection by Gram-negative Bacteria. I. The Effect of Colicin on Bactericidal Power of Blood*

Abstract

The intimate association of colicin with endo-toxin has interfered with the study of colicin in vivo. In order to examine the properties of colicin in vivo without the complicating effects of endotoxin, an attempt was made to separate them by growing Escherichia coli CF1 on the outside of cellophane dialysis tubing. Colicin V passed into the bag, but not out. The colicin in the cellophane bag was sterile, relatively heat resistant, active against E. coli strains in high dilution, and produced no fever or other signs of endo-toxin activity in rabbits. 50 to 120 minutes after subcutaneous inoculation of this nontoxic colicin, mouse blood and serum, which normally contain no bactericidal activity, became strongly bactericidal for the universal indicator E. coli W1895. Mixture of serum with colicin V in vitro greatly increased the bactericidal titer of the colicin and abolished the inhibitory effect of endotoxins on colicin. Antisera to the endotaxin of E. coli CF1 (from which colicin V was prepared) did not reduce the colicin V bactericidal activity. These findings suggest that colicin V can be separated from the toxic and antigenic fractions of endotaxin, and can contribute to the heat-resistant bactericidal property of normal blood. The possibility that colicin from intestinal bacteria can diffuse through the bowel wall into the blood stream is discussed.