Synergistic role of curli and cellulose in cell adherence and biofilm formation of attaching and effacing Escherichia coli and identification of Fis as a negative regulator of curli

Authors

  • Zeus Saldaña,

    1. Department of Immunobiology, University of Arizona, 1501 N. Tucson, AZ 85724, USA.
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  • Juan Xicohtencatl-Cortes,

    1. Department of Immunobiology, University of Arizona, 1501 N. Tucson, AZ 85724, USA.
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  • Fabiola Avelino,

    1. Instituto de Ciencias, Benemérita Universidad Autónoma de Puebla, Edificio 76, Ciudad Universitaria, Pue 72000, México.
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  • Alan D. Phillips,

    1. Centre for Paediatric Gastroenterology, Royal Free and University College Medical School, Rowland Hill Street, London NW3 2PF, UK.
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  • James B. Kaper,

    1. Department of Microbiology and Immunology, University of Maryland School of Medicine, 685 West Baltimore St., Baltimore, MD 21201, USA.
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  • José L. Puente,

    1. Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Mor 62210, México.
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  • Jorge A. Girón

    Corresponding author
    1. Department of Immunobiology, University of Arizona, 1501 N. Tucson, AZ 85724, USA.
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    • Present address: Department of Molecular Genetics and Microbiology Emerging Pathogens Institute, 1600 SW Archer Road, R2-231 ARB, PO Box 100266 Gainesville, FL 32610, USA.


*E-mail jagiron@yahoo.com; Tel. (+1) 352 3923136; Fax (+1) 352 8462042.

Summary

Curli are adhesive fimbriae of Escherichia coli and Salmonella enterica. Expression of curli (csgA) and cellulose (bcsA) is co-activated by the transcriptional activator CsgD. In this study, we investigated the contribution of curli and cellulose to the adhesive properties of enterohaemorragic (EHEC) O157:H7 and enteropathogenic E. coli (EPEC) O127:H6. While single mutations in csgA, csgD or bcsA in EPEC and EHEC had no dramatic effect on cell adherence, double csgAbcsA mutants were significantly less adherent than the single mutants or wild-type strains to human colonic HT-29 epithelial cells or to cow colon tissue in vitro. Overexpression of csgD (carried on plasmid pCP994) in a csgD mutant, but not in the single csgA or bscA mutants, led to significant increase in adherence and biofilm formation in EPEC and EHEC, suggesting that synchronized over-production of curli and cellulose enhances bacterial adherence. In line with this finding, csgD transcription was activated significantly in the presence of cultured epithelial cells as compared with growth in tissue culture medium. Analysis of the influence of virulence and global regulators in the production of curli in EPEC identified Fis (factor for inversion stimulation) as a, heretofore unrecognized, negative transcriptional regulator of csgA expression. An EPEC E2348/69Δfis produced abundant amounts of curli whereas a double fis/csgD mutant yielded no detectable curli production. Our data suggest that curli and cellulose act in concert to favour host colonization, biofilm formation and survival in different environments.

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