The influence of radiomimetic substances on deoxyribonucleic acid synthesis and function studied in escherichia coli/phage systems - IV. Colony-forming ability and escherichia coli strain B and two of its mutants following alkylation

Abstract

Escherichia coli strain B, its mutant B/r and a new mutant, designated B/HN2, have been employed in a study of the effect of alkylating agents upon the survival of colony-forming ability and phage-synthetic capacity. This has been done against the background of our earlier work upon phage and that of other workers upon bacteria, employing both alkylating agents and radiations. The sensitivity of B toward all the compounds now studied was greater than that of the other two strains as regards colony-forming ability, whereas all three strains showed a similar sensitivity in regard to capacity. Survival curves of all strains treated with mono-functional agents were of a so-called "multi-hit" type, whereas those for bifunctional compounds were downwardly concave. The response to di(2-chloroethyl) methylamine (HN2) was complicated by the chemical change undergone by this substance in aqueous solution, as was shown by a comparison of fresh and aged solutions and of the effect of different cultural conditions prior to treatment. As with radiations, phage-synthetic capacity was considerably less sensitive to alkylation than colony-forming ability, whilst this sensitivity was essentially the same for the three strains. No significant difference was found between the effect of HN2 on the capacity of B for T2 and for T7. The capacity of B/r for T2 was more sensitive to treatment by a bifunctional agent than by a monofunctional agent of similar chemical reactivity. It is suggested that this may implicate ribonucleic acids as the reactive substrate essential to capacity.