Resistance to the Bactericidal Effect of Ultraviolet Radiatic Conferred on Enterobacteria by the Colicine Factor coll

Abstract

SUMMARY Strains of Salmonella typhimurium and Escherichia coli which have acquired the colicine factor, colI, are less sensitive to the lethal effects of ultraviolet (u.v.) radiation than the non-colicinogenic parent strain. The dose of u.v. radiation required to kill 50% of the population of S. typhimurium strain LT2 colicinogenic for colicine I was greater by a factor of three than that required to kill 50% of the non-colicinogenic parent. The number of survivors of the non-colicinogenic strain decreased more or less exponentially with dose; the survival curve of the colicinogenic strain had a pronounced ‘shoulder’. Experiments with a strain of E. coli K 12 carrying lambda prophage indicated that the presence of colI decreased the incidence of phage induction following u.v. irradiation.