title: Epistasis and allele specificity in the emergence of a stable polymorphism in Escherichia coli.
abstract: Ecological opportunities promote population divergence into coexisting lineages. However, the genetic mechanisms that enable new lineages to exploit these opportunities are poorly understood except in cases of single mutations. We examined how two Escherichia coli lineages diverged from their common ancestor at the outset of a long-term coexistence. By sequencing genomes and reconstructing the genetic history of one lineage, we showed that three mutations together were sufficient to produce the frequency-dependent fitness effects that allowed this lineage to invade and stably coexist with the other. These mutations all affected regulatory genes and collectively caused substantial metabolic changes. Moreover, the particular derived alleles were critical for the initial divergence and invasion, indicating that the establishment of this polymorphism depended on specific epistatic interactions.
authors.affiliation: Laboratoire Adaptation et Pathogénie des Microorganismes, Université Joseph Fourier, Institut Jean Roget, F-38041 Grenoble, France.
authors.forename: Jessica
authors.initials: J
authors.lastname: Plucain
authors.forename: Thomas
authors.initials: T
authors.lastname: Hindré
authors.forename: Mickaël
authors.initials: M
authors.lastname: Le Gac
authors.forename: Olivier
authors.initials: O
authors.lastname: Tenaillon
authors.forename: Stéphane
authors.initials: S
authors.lastname: Cruveiller
authors.forename: Claudine
authors.initials: C
authors.lastname: Médigue
authors.forename: Nicholas
authors.initials: N
authors.lastname: Leiby
authors.forename: William R
authors.initials: WR
authors.lastname: Harcombe
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Marx
authors.forename: Richard E
authors.initials: RE
authors.lastname: Lenski
authors.forename: Dominique
authors.initials: D
authors.lastname: Schneider
mesh_terms: D000483:Alleles; D004843:Epistasis, Genetic; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D019143:Evolution, Molecular; D005798:Genes, Bacterial; D005809:Genes, Regulator; D056084:Genetic Fitness; D005838:Genotype; D005947:Glucose / Q000378:metabolism; D056265:Microbial Interactions; D009154:Mutation; D011110:Polymorphism, Genetic
chemical_list: D005947:Glucose