title: Evolution of high mutation rates in experimental populations of E. coli.
abstract: Most mutations are likely to be deleterious, and so the spontaneous mutation rate is generally held at a very low value. Nonetheless, evolutionary theory predicts that high mutation rates can evolve under certain circumstances. Empirical observations have previously been limited to short-term studies of the fates of mutator strains deliberately introduced into laboratory populations of Escherichia coli, and to the effects of intense selective events on mutator frequencies in E. coli. Here we report the rise of spontaneously originated mutators in populations of E. coli undergoing long-term adaptation to a new environment. Our results corroborate computer simulations of mutator evolution in adapting clonal populations, and may help to explain observations that associate high mutation rates with emerging pathogens and with certain cancers.
authors.affiliation: Department of Biology, University of Pennsylvania, Philadelphia 19104, USA. paulsnie@sas.upenn.edu
authors.forename: P D
authors.initials: PD
authors.lastname: Sniegowski
authors.forename: P J
authors.initials: PJ
authors.lastname: Gerrish
authors.forename: R E
authors.initials: RE
authors.lastname: Lenski
mesh_terms: D000222:Adaptation, Physiological; D000890:Anti-Infective Agents / Q000494:pharmacology; D019020:Directed Molecular Evolution; D004352:Drug Resistance, Microbial; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics*; D019143:Evolution, Molecular; D005816:Genetic Complementation Test; D009154:Mutation; D009268:Nalidixic Acid / Q000494:pharmacology; D010641:Phenotype; D014169:Transformation, Bacterial
chemical_list: D000890:Anti-Infective Agents; D009268:Nalidixic Acid