Affiliation:
1. Department of Microbiology, The University of Guelph, Guelph, Ontario, Canada N1G 2W1
Abstract
ABSTRACT
Group 1 capsules of
Escherichia coli
are similar to the capsules produced by strains of
Klebsiella
spp. in terms of structure, genetics, and patterns of expression. The striking similarities between the capsules of these organisms prompted a more detailed investigation of the
cps
loci encoding group 1 capsule synthesis. Six strains of
K. pneumoniae
and 12 strains of
E. coli
were examined. PCR analysis showed that the clusters in these strains are conserved in their chromosomal locations. A highly conserved block of four genes,
orfX-wza-wzb-wzc
, was identified in all of the strains. The
wza
and
wzc
genes are required for translocation and surface assembly of
E. coli
K30 antigen. The conservation of these genes points to a common pathway for capsule translocation. A characteristic JUMPstart sequence was identified upstream of each cluster which may function in conjunction with RfaH to inhibit transcriptional termination at a stem-loop structure found immediately downstream of the “translocation-surface assembly” region of the cluster. Interestingly, the sequence upstream of the
cps
clusters in five
E. coli
strains and one
Klebsiella
strain indicated the presence of IS elements. We propose that the IS elements were responsible for the transfer of the
cps
locus between organisms and that they may continue to mediate recombination between strains.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
108 articles.
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