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

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.