title: Evolution of transposable elements: an IS10 insertion increases fitness in Escherichia coli.
abstract: Strains of Escherichia coli carrying Tn10, a transposon consisting of two IS10 insertion sequences flanking a segment encoding for a tetracycline-resistance determinant, gain a competitive advantage in chemostat cultures. All Tn10-bearing strains that increase in frequency during competition have a new IS10 insertion that is found in the same location in the genome of those strains. We mapped, by a gradient of transmission, the position of the new IS10 insertion. We examined 11 isolates whose IS10 insertion was deleted by recombinational crossing-over, and in all cases the competitive fitness of the isolates was decreased. These results show that the IS10-generated insertion increases fitness in chemostat cultures. We named the insertion fit::IS10 and suggest that transposable elements may speed the rate of evolution by promoting nonhomologous recombination between preexisting variations within a genome and thereby generating adaptive variation.
authors.affiliation: Department of Ecology and Evolutionary Biology, Northwestern University, Evanston, Illinois 60201.
authors.forename: L
authors.initials: L
authors.lastname: Chao
authors.forename: S M
authors.initials: SM
authors.lastname: McBroom
mesh_terms: D005075:Biological Evolution; D002874:Chromosome Mapping; D004251:DNA Transposable Elements; D004926:Escherichia coli / Q000235:genetics; D014644:Genetic Variation; D009154:Mutation; D012641:Selection, Genetic
chemical_list: D004251:DNA Transposable Elements