Prophage inductive efficiency of alkylating agents and radiations.

The prophage inducing efficiency in E. coli K-12 (lambda) of a number of agents--alkylating agents and radiations--has been compared at a high survival of bacteria. The inducing effectiveness (per alkylation in DNA) and efficiency (compared with mutation frequency in E. coli Sd-4) was found to decrease in the order 2-hydroxyethylating agents (2-hydroxyethyl methanesulphonate and ethylene oxide) greater than isopropyl methanesulphonate approximately equal to methyl methanesulphonate greater than ethylating agents (diethyl sulphate, ethyl methanesulphonate). The low inducing activity of the ethylating agents could not be explained with respect to their reactivity towards targets of differing nucleophilicity, nor could the effectiveness in mutagenicity or the ability to break the chromosomes in the presence of metal ions be invoked. The high inducing efficiency of hydroxyalkylating agents may be related to their ability to break DNA strands.