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Regulation of enteropathogenic Escherichia coli envelope protein expression by the Cpx response and small RNAs

  • Author / Creator
    Vogt, Stefanie L.
  • Gram-negative bacteria are characterized by their complex cell envelope, which consists of the inner membrane, outer membrane, and intervening periplasmic space. Envelope-localized proteins play a critical role in many interactions of a bacterium with its environment, including uptake of nutrients, extrusion of waste, adhesion to surfaces, and motility. As such, regulation of envelope protein expression is crucial to the survival of Gram-negative organisms such as Escherichia coli. Two regulatory systems involved in controlling envelope protein expression are the Cpx envelope stress response and small non-coding RNAs (sRNAs). The Cpx response is believed to sense misfolding of inner membrane and periplasmic proteins; in response, Cpx increases the transcription of a suite of genes encoding envelope-localized protein folding and degrading factors. sRNAs, with assistance from the RNA chaperone protein Hfq, base-pair with target mRNAs to modulate their rate of translation and/or stability. The first goal of this thesis was to examine the regulatory effects of the Cpx response and sRNAs upon the expression of the bundle-forming pilus (BFP), an envelope-localized protein complex that mediates initial interaction of enteropathogenic E. coli (EPEC) with host cells. We found that the Cpx response affects BFP expression at multiple levels. Activation of the Cpx response represses transcription of the bfp gene cluster and prevents BFP expression, while inactivation of the Cpx response diminishes BFP expression at the post-translational level, as a result of decreased expression of periplasmic protein folding factors. The RNA chaperone Hfq also represses transcription of the bfp genes by destabilizing the perA transcript, which encodes the major regulator of bfp transcription. A second goal of this work was to characterize the interactions between the Cpx response and sRNAs. I demonstrated that the Cpx response regulates the expression of four sRNA-encoding genes. Conversely, Hfq and sRNAs also affect activity of the Cpx response, as deletion of hfq in EPEC activates the Cpx pathway, while overexpression of the sRNA RprA diminishes Cpx activity. These results deepen our understanding of how regulatory systems attune envelope protein expression to environmental and physiological conditions, thereby contributing to the pathogenesis of EPEC and related organisms.

  • Subjects / Keywords
  • Graduation date
    2013-11
  • Type of Item
    Thesis
  • Degree
    Doctor of Philosophy
  • DOI
    https://doi.org/10.7939/R35D8NR5Q
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.
  • Language
    English
  • Institution
    University of Alberta
  • Degree level
    Doctoral
  • Department
    • Department of Biological Sciences
  • Specialization
    • Microbiology & Biotechnology
  • Supervisor / co-supervisor and their department(s)
    • Raivio, Tracy (Biological Sciences)
  • Examining committee members and their departments
    • Raivio, Tracy (Biological Sciences)
    • Szymanski, Christine (Biological Sciences)
    • Mulvey, Matthew (University of Utah)
    • Owttrim, George (Biological Sciences)
    • Pukatzki, Stefan (Medical Microbiology and Immunology)