Evaluating evolutionary models of stress-induced mutagenesis in bacteria

In this Opinion article, the authors discuss models that could explain the evolution of stress-induced mutagenesis in bacteria. They include a new model that argues that genetic drift could have a role in the evolution of low-fidelity DNA polymerases. Increased mutation rates under stress allow bacterial populations to adapt rapidly to stressors, including antibiotics. Here we evaluate existing models for the evolution of stress-induced mutagenesis and present a new model arguing that it evolves as a result of a complex interplay between direct selection for increased stress tolerance, second-order selection for increased evolvability and genetic drift. Further progress in our understanding of the evolutionary biology of stress and mutagenesis will require a more detailed understanding both of the patterns of stress encountered by bacteria in nature and of the mutations that are produced under stress.