The road not taken: Could stress-specific mutations lead to different evolutionary paths?

Organisms often encounter stressful conditions,some of which damage their dna. in response,some organisms show a high expression of error-prone dna repair machinery,causing a temporary increase in the genome-wide mutation rate. although we now have a detailed map of the molecular mechanisms underlying such stress-induced mutagenesis (sim),it has been hotly debated whether sim alters evolutionary dynamics. key to this controversy is our poor understanding about which stresses increase mutagenesis and their long-term consequences for adaptation. in a new study with escherichia coli,maharjan and ferenci show that while only some nutritional stresses (phosphorous and carbon limitation) increase total mutation rates,each stress generates a unique spectrum of mutations. their results suggest the potential for specific stresses to shape evolutionary dynamics and highlight the necessity for explicit tests of the long-term evolutionary impacts of sim. © 2017 deepa agashe.