Molecular evolution of the Escherichia coli chromosome. III. Clonal frames.
PCR fragments, 1500-bp, from 15 previously sequenced regions in the Escherichia coli chromosome have been compared by restriction analysis in a large set of wild (ECOR) strains. Prior published observations of segmental clonality are confirmed: each of several sequence types is shared by a number of strains. The rate of recombinational replacement and the average size of the replacements are estimated in a set of closely related strains in which a clonal frame is dotted with occasional stretches of DNA belonging to other clones. A clonal hierarchy is described. Some new comparative sequencing data are presented.
Milkman
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Department of Biology, University of Iowa, Iowa City 52242.
Bridges
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D001483:Base Sequence; D005075:Biological Evolution; D002876:Chromosomes, Bacterial; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics*; D009876:Operon; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D012689:Sequence Homology, Nucleic Acid