Increased Rate of Plaque-type and Host-range Mutation following Treatment of Bacteriophage in vitro with Ethyl Methane Sulphonate

Abstract

ALTHOUGH bacteriophage undergoes ‘spontaneous mutation during the course of intracellular multiplication, it has proved difficult to increase the mutation-rate (that is, to ‘induce’ mutation) by artificial means. Latarjet¹ has presented evidence for an increased proportion of host-range mutants in the progeny of bacteria infected with phage T2 as a result of ultraviolet irradiation of the complex. The proportion of host-range mutants of T1 was found by Tessman² to be increased when both host cells and virus were irradiated with ultra-violet prior to infection, but not when either component alone was irradiated. De Mars³ found an increase in the yield of plaque-type mutants when euflavine was administered during intracellular growth, and Litman and Pardee⁴ achieved a similar result when phage was grown through a number of cycles in a medium containing bromouracil. No increase in the mutation-rate of phage has hitherto been reported which was the consequence of treatment of the phage alone prior to infection of the host cells. I have now been able to show that treatment of phage T2 in vitro with the ethylating agent ethyl methane sulphonate results in an increase in the number of mutations to the r and h genotype in the first cycle of infection of the (untreated) host organism Escherichia coli B.