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Infect Immun, August 1998, p. 3810-3817, Vol. 66, No. 8
Laboratory of Genetics, University of
Wisconsin-Madison, Madison Wisconsin 537061;
Institute of Biochemistry, Biological Research Center, H-6701
Szeged, Hungary2; and
Center for Vaccine
Development3 and
Division of
Infectious Disease,4 University of Maryland
School of Medicine, Baltimore, Maryland 21201
Received 29 December 1997/Returned for modification 6 March
1998/Accepted 27 May 1998
We report the complete 43,359-bp sequence of the locus of
enterocyte effacement (LEE) from EDL933, an enterohemorrhagic
Escherichia coli O157:H7 serovar originally isolated from
contaminated hamburger implicated in an outbreak of hemorrhagic
colitis. The locus was isolated from the EDL933 chromosome with a
homologous-recombination-driven targeting vector. Recent completion of
the LEE sequence from enteropathogenic E. coli (EPEC)
E2348/69 afforded the opportunity for a comparative analysis of the
entire pathogenicity island. We have identified a total of 54 open
reading frames in the EDL933 LEE. Of these, 13 fall within a putative
P4 family prophage designated 933L. The prophage is not present in
E2348/69 but is found in a closely related EPEC O55:H7 serovar and
other O157:H7 isolates. The remaining 41 genes are shared by the two
complete LEEs, and we describe the nature and extent of variation among
the two strains for each gene. The rate of divergence is heterogeneous
along the locus. Most genes show greater than 95% identity between the
two strains, but other genes vary more than expected for clonal
divergence among E. coli strains. Several of these highly
divergent genes encode proteins that are known to be involved in
interactions with the host cell. This pattern suggests recombinational
divergence coupled with natural selection and has implications for our
understanding of the interaction of both pathogens with their host, for
the emergence of O157:H7, and for the evolutionary history of pathogens in general.
0019-9567/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Molecular Evolution of a Pathogenicity Island from
Enterohemorrhagic Escherichia coli O157:H7
*
Corresponding author. Mailing address: Laboratory of
Genetics, University of Wisconsin-Madison, 445 Henry Mall, Rm. B44,
Madison, WI 53706. Phone: (608) 262-2534. Fax: (608) 263-7459. E-mail: nicole{at}genetics.wisc.edu.
Laboratory of Genetics paper 3516.
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