Enhancement of the Normal Reversion-rate of a Serineless Escherichia coli Mutant by Certain Organic Acids

Abstract

SOME mutant genes involving loss of function are known to be capable of reversion at the specific locus; this fact implies that in mutant organisms particular genes are not necessarily destroyed, but may be merely altered, or ‘inactivated’ with respect to the specific reaction they once controlled. The gene is, so to speak, in an inactive allelic state—but one which can revert or back-mutate to the active allelic state of the wild-type parent. Can environmental conditions other than general mutagenic agents enhance the reactivation of a mutated gene to its original allelic state ? It is conceivable that the presence of certain common metabolites, the configuration of which is related to the damaged enzyme – gene system, might, by some as yet unknown mechanism, have such an influence. In various connexions, ‘substrate-induced mutations’ have been previously discussed^1–3.