The rate of adaptive mutagenesis in Escherichia coli is enhanced by oxygen (superoxide)

Adaptive mutagenesis is that which occurs in non-dividing cells and which allows growth under the selective conditions imposed. We now report that reversion of amino acid auxotrophies in E. coli fits that definition and is enhanced under conditions conducive to oxidative damage to DNA. Thus adaptive mutagenesis was similar to 4-fold more frequent in a sodA sodB strain than in the superoxide dismutase-replete parental str ain and this mutagenesis was suppressed under anaerobic conditions. Moreover, a cell permeant manganic porphyrin, capable of catalyzing the dismutation of O-2(-), diminished the rate of occurrence of these mutations. Repair of oxidative damage to DNA, in the non-dividing cells, appears to provide the opportunity for adaptive mutagenesis.