Stress-induced mutagenesis in bacteria

Abstract

Under stress, high mutation rates can be advantageous because they increase the probability of generation of the adaptive mutations. Mutation rates can be modulated by changing the proportion of constitutive mutator versus non-mutator bacteria at the population level, or by inducing stress responses, which increase mutation rates transiently in individual cells. Constitutive mutator alleles are selected because they hitchhike with the adaptive mutations they generate. There are two nonexclusive hypotheses concerning the nature of selective pressure acting on the molecular mechanisms controlling stress-induced mutagenesis: stress-induced mutagenesis could be an unavoidable by-product of mechanisms involved in survival under stress, or stress-induced mutator phenotypes could be selected for in the same way as constitutive mutator alleles; that is, via hitchhiking with the adaptive mutations they generate. However, regardless of the nature of selective pressure acting on stress-induced mutagenesis, it is very likely that the resulting increased genetic variability plays an important role in the bacterial evolution.