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Journal of Bacteriology, April 1999, p. 2307-2313, Vol. 181, No. 7
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.

Conserved Organization in the cps Gene Clusters for Expression of Escherichia coli Group 1 K Antigens: Relationship to the Colanic Acid Biosynthesis Locus and the cps Genes from Klebsiella pneumoniae

Andrea Rahn, Jolyne Drummelsmith, and Chris Whitfield*

Department of Microbiology, The University of Guelph, Guelph, Ontario, Canada N1G 2W1

Received 29 September 1998/Accepted 16 January 1999

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.

* Corresponding author. Mailing address: Department of Microbiology, The University of Guelph, Guelph, ON, Canada N1G 2W1. Phone: (519) 824-4120, ext. 3478. Fax: (519) 837-1802. E-mail: cwhitfie{at}uoguelph.ca.

Journal of Bacteriology, April 1999, p. 2307-2313, Vol. 181, No. 7
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.


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