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Journal of Bacteriology, June 2009, p. 3451-3461, Vol. 191, No. 11
0021-9193/09/$08.00+0 doi:10.1128/JB.01539-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
The Escherichia coli Common Pilus and the Bundle-Forming Pilus Act in Concert during the Formation of Localized Adherence by Enteropathogenic E. coli
,
Zeus Saldaña,1
Ay
en L. Erdem,1
Stephanie Schüller,2
Iruka N. Okeke,3
Mark Lucas,2
Arunon Sivananthan,2
Alan D. Phillips,2
James B. Kaper,4
José L. Puente,5 and
Jorge A. Girón1*
Department of Immunobiology, University of Arizona, 1501 N. Campbell Ave., Tucson, Arizona 85724,1 Centre for Paediatric Gastroenterology, Royal Free Hospital, London NW3 2QG, United Kingdom,2 Department of Biology, Haverford College, 370 Lancaster Ave., Haverford, Pennsylvania 19041,3 Department of Microbiology and Immunology, University of Maryland School of Medicine, 685 West Baltimore St., Baltimore, Maryland 21201,4 Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Mor 62210, México5
Received 30 October 2008/ Accepted 2 February 2009
Although the bundle-forming pilus (BFP) of enteropathogenic Escherichia coli (EPEC) mediates microcolony formation on epithelial cells, the adherence of BFP-deficient mutants is significantly abrogated, but the mutants are still adherent due to the presence of intimin and possibly other adhesins. In this study we investigated the contribution of the recently described E. coli common pilus (ECP) to the overall adherence properties of EPEC. We found that ECP and BFP structures can be simultaneously observed in the course (between zero time and 7 h during infection) of formation of localized adherence on cultured epithelial cells. These two pilus types colocalized at different levels of the microcolony topology, tethering the adhering bacteria. No evidence of BFP disappearance was found after prolonged infection. When expressed from a plasmid present in nonadherent E. coli HB101, ECP rendered this organism highly adherent at levels comparable to those of HB101 expressing the BFP. Purified ECP bound in a dose-dependent manner to epithelial cells, and the binding was blocked with anti-ECP antibodies, confirming that the pili possess adhesin properties. An ECP mutant showed only a modest reduction in adherence to cultured cells due to background expression levels of BFP and intimin. However, isogenic mutants not expressing EspA or BFP were significantly less adherent when the ecpA gene was also deleted. Furthermore, a 
espA ecpA double mutant (unable to translocate Tir and to establish intimate adhesion) was at least 10-fold less adherent than the espA and ecpA single mutants, even in the presence of BFP. A bfp espA ecpA triple mutant showed the least adherence compared to the wild type and all the isogenic mutant strains tested, suggesting that ECP plays a synergistic role in adherence. Our data indicate that ECP is an accessory factor that, in association with BFP and other adhesins, contributes to the multifactorial complex interaction of EPEC with host epithelial cells.
* Corresponding author. Present address: Department of Molecular Genetics and Microbiology, Emerging Pathogens Institute, 1600 SW Archer Rd., University of Florida, Gainesville, FL 32610. Phone: (352) 273-8892. Fax: (352) 846-2042. E-mail: jagiron{at}ufl.edu
Published ahead of print on 13 February 2009.
Supplemental material for this article may be found at http://jb.asm.org/.
Journal of Bacteriology, June 2009, p. 3451-3461, Vol. 191, No. 11
0021-9193/09/$08.00+0 doi:10.1128/JB.01539-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
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