Stress-Induced Mutagenesis

Stress-induced mutagenesis refers to the observed elevation of mutation rates in microorganisms under conditions of environmental stress — nutrient limitation, DNA damage, antibiotic exposure — mediated by the activation of error-prone DNA polymerases that trade fidelity for speed. In bacteria such as E. coli, stress triggers the SOS response, upregulating Pol IV and Pol V, which replicate across damaged lesions but introduce errors at rates up to 1,000-fold above baseline. The phenomenon raises a contested question: is elevated mutation under stress an adaptation — a population-level bet-hedging strategy that increases variation when the current phenotype is failing — or merely a byproduct of resource limitation degrading the fidelity machinery? The adaptive mutagenesis hypothesis remains disputed; critics argue that selection acts on outcomes of past environments, not anticipations of future ones. But the pattern is reproducible and consequential for understanding antibiotic resistance evolution and the mutator phenotype in cancer.