title: Evolution of mutation rates in hypermutable populations ofEscherichia colipropagated at very small effective population size.
abstract: Mutation is the ultimate source of the genetic variation-including variation for mutation rate itself-that fuels evolution. Natural selection can raise or lower the genomic mutation rate of a population by changing the frequencies of mutation rate modifier alleles associated with beneficial and deleterious mutations. Existing theory and observations suggest that where selection is minimized, rapid systematic evolution of mutation rate either up or down is unlikely. Here, we report systematic evolution of higher and lower mutation rates in replicate hypermutableEscherichia colipopulations experimentally propagated at very small effective size-a circumstance under which selection is greatly reduced. Several populations went extinct during this experiment, and these populations tended to evolve elevated mutation rates. In contrast, populations that survived to the end of the experiment tended to evolve decreased mutation rates. We discuss the relevance of our results to current ideas about the evolution, maintenance and consequences of high mutation rates.
authors.affiliation: Department of Biology, Leidy Laboratories, University of Pennsylvania, Philadelphia, PA 19104, USA tsingh@cvm.tamu.edu.
authors.forename: Tanya
authors.identifier: 0000-0001-7502-6561
authors.initials: T
authors.lastname: Singh
authors.affiliation: Department of Biology, Leidy Laboratories, University of Pennsylvania, Philadelphia, PA 19104, USA.
authors.forename: Meredith
authors.initials: M
authors.lastname: Hyun
authors.affiliation: Department of Biology, Leidy Laboratories, University of Pennsylvania, Philadelphia, PA 19104, USA.
authors.forename: Paul
authors.initials: P
authors.lastname: Sniegowski
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D004352:Drug Resistance, Microbial / Q000235:genetics; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics*; D019143:Evolution, Molecular; D056084:Genetic Fitness; D059645:Mutation Rate; D009268:Nalidixic Acid / Q000494:pharmacology; D012641:Selection, Genetic; D013307:Streptomycin / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D009268:Nalidixic Acid; D013307:Streptomycin
keywords: antimutators; asexual populations; evolution of mutation rates; indirect selection; mutation accumulation; mutators