The Wild Side of Adaptive Mutation

Abstract

The evidence for adaptive mutation in response to environmental stress has been obtained from laboratory strains of organisms that tend to be more homologous than the wild type. Bjedov et al. (see the Perspective by Rosenberg and Hastings) collected about 800 natural isolates of the bacterium Escherichia coli and found that the majority display stress-inducible (or stationary-phase) elevation of mutation in response to growth-limiting conditions. Their analysis shows that carbon starvation is the physiologically relevant trigger and that removing oxygen largely eliminated enhanced mutation in aging colonies. Genetic analysis of a single natural isolate revealed the roles of the carbon-sensing genetic regulators, the stationary-phase and stress-response regulon, the RecA protein, high-fidelity DNA polymerase II, and compromised mismatch repair. Computer simulations showed that the remarkably high frequency of aging colony mutators in natural isolates could be accounted for by the indirect selective advantage of increased genetic variability. I. Bjedov, O. Tenaillon, B. Gérard, V. Souza, E. Denamur, M. Radman, F. Taddei, I. Matic. Stress-induced mutagenesis in bacteria. Science 300, 1404-1409 (2003). [Abstract] [Full Text] S. M. Rosenberg, P. J. Hastings, Modulating mutation rates in the wild. Science 300, 1382-1383 (2003). [Summary] [Full Text]