Bacteria have a prodigious ability to reinvent themselves, speedily adapting to new hosts, new conditions, and new antibiotic countermeasures. A group of researchers report in this issue (p. 1208) that they have found one explanation for that versatility in E. coli and another pathogen, Salmonella enterica. In strains from outbreaks of food poisoning, they detected an exceptionally high percentage of "mutators"--microbes with a genetic flaw that makes them a prolific source of new variants.