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J. Bacteriol., 10 1995, 5784-5789, Vol 177, No. 20
U Bergthorsson and H Ochman
Comparisons of the genetic maps of Escherichia coli K-12 and Salmonella
typhimurium LT2 suggest that the size and organization of bacterial
chromosomes are highly conserved. Employing pulsed-field gel
electrophoresis, we have estimated the extent of variation in genome size
among 14 natural isolates of E. coli. The BlnI and NotI restriction
fragment patterns were highly variable among isolates, and genome sizes
ranged from 4,660 to 5,300 kb, which is several hundred kilobases larger
than the variation detected between enteric species. Genome size
differences increase with the evolutionary genetic distance between
lineages of E. coli, and there are differences in genome size among the
major subgroups of E. coli. In general, the genomes of natural isolates are
larger than those of laboratory strains, largely because of the fact that
laboratory strains were derived from the subgroup of E. coli with the
smallest genomes.
Copyright © 1995, American Society for Microbiology
Heterogeneity of genome sizes among natural isolates of Escherichia coli
Department of Biology, University of Rochester, New York 14627, USA.
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