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Infection and Immunity, November 2008, p. 5062-5071, Vol. 76, No. 11
0019-9567/08/$08.00+0     doi:10.1128/IAI.00654-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Contribution of the Ler- and H-NS-Regulated Long Polar Fimbriae of Escherichia coli O157:H7 during Binding to Tissue-Cultured Cells{triangledown}

Alfredo G. Torres,1,2,3* Terry M. Slater,1 Shilpa D. Patel,1 Vsevolod L. Popov,3 and Margarita M. P. Arenas-Hernández4

Department of Microbiology and Immunology,1 Department of Pathology,2 Sealy Center for Vaccine Development, University of Texas Medical Branch, Galveston, Texas 77555-1070,3 Centro de Investigaciones en Ciencias Microbiológicas, B. Universidad Autónoma de Puebla, Apartado Postal 1622, Puebla, Puebla, México4

Received 27 May 2008/ Returned for modification 1 July 2008/ Accepted 27 August 2008

The expression of the long polar fimbriae (LPF) of enterohemorrhagic Escherichia coli (EHEC) O157:H7 is controlled by a tightly regulated process, and, therefore, the role of these fimbriae during binding to epithelial cells has been difficult to establish. We recently found that histone-like nucleoid-structuring protein (H-NS) binds to the regulatory sequence of the E. coli O157:H7 lpf1 operon and "silences" its transcription, while Ler inhibits the action of the H-NS protein and allows lpf1 to be expressed. In the present study, we determined how the deregulated expression of LPF affects binding of EHEC O157:H7 to tissue-cultured cells, correlating the adherence phenotype with lpf1 expression. We tested the adherence properties of EHEC hns mutant and found that this strain adhered 2.8-fold better than the wild type. In contrast, the EHEC ler mutant adhered 2.1-fold less than the wild type. The EHEC hns ler mutant constitutively expressed the lpf genes, and, therefore, we observed that the double mutant adhered 5.6-fold times better than the wild type. Disruption of lpfA in the EHEC hns and hns ler mutants or the addition of anti-LpfA serum caused a reduction in adhesion, demonstrating that the increased adherence was due to the expression of LPF. Immunogold-labeling electron microscopy showed that LPF is present on the surface of EHEC lpfA+ strains. Furthermore, we showed that EHEC expressing LPF agglutinates red blood cells from different species and that the agglutination was blocked by the addition of anti-LpfA serum. Overall, our data confirmed that expression of LPF is a tightly regulated process and, for the first time, demonstrated that these fimbriae are associated with adherence and hemagglutination phenotypes in EHEC O157:H7.

* Corresponding author. Mailing address: Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX 77555-1070. Phone: (409) 747-0189. Fax: (409) 747-6869. E-mail: altorres{at}utmb.edu

{triangledown} Published ahead of print on 15 September 2008.

Editor: A. J. Bäumler

Infection and Immunity, November 2008, p. 5062-5071, Vol. 76, No. 11
0019-9567/08/$08.00+0     doi:10.1128/IAI.00654-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Torres, A. G., Blanco, M., Valenzuela, P., Slater, T. M., Patel, S. D., Dahbi, G., Lopez, C., Barriga, X. F., Blanco, J. E., Gomes, T. A. T., Vidal, R., Blanco, J. (2009). Genes Related to Long Polar Fimbriae of Pathogenic Escherichia coli Strains as Reliable Markers To Identify Virulent Isolates. J. Clin. Microbiol. 47: 2442-2451 [Abstract] [Full Text]  


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