Dissertation
A tale of two regulators: expression of the virulence-associated Type IV pili and lipooligosaccharide sialyltransferase is controlled by CrgA and Rsp in Neisseria gonorrhoeae
Doctor of Philosophy (Ph.D.), Drexel University
Jul 2013
DOI:
https://doi.org/10.17918/00008792
Abstract
Responsible for an estimated 820,000 new infections and health care costs totaling $1.1 billion every year in the United States alone, Neisseria gonorrhoeae is a leading cause of microbial-associated morbidity and is the second most commonly sexually-transmitted bacterial pathogen worldwide. Although the bacterial niche is relegated solely to the human host, the local environment (e.g. presence or absence of normal flora, immune effectors, hormones, etc.) and the interaction of the bacteria with host cells function to activate expression of genes that are required for growth and survival. Type IV pili (Tfp), for example, are important factors in initial cell-adhesion and are required for infectivity in vivo. In contrast, expression of Lipooligosaccharide (LOS) sialyltransferase (Lst), a surface-expressed enzyme that catalyzes LOS sialylation, is important for bacterial survival in the bloodstream or during acute infection when the innate immune response is initiated to promote bacterial clearance. Gaining an understanding of the molecular mechanisms by which these factors are regulated is critical for evaluating their potential as therapeutic vaccine targets. In this study, we examined the effects of two transcriptional regulators, CrgA and Rsp, on expression of Tfp and Lst. Deletion of either crgA or rsp resulted in lack of full induction of the primary pilin gene, pilE, in a manner that was not dependent on cell-adhesion. Rsp, specifically, was demonstrated to promote transcriptional activation by binding to an upstream activator sequence in the pilE promoter. Deletion of crgA, but not rsp, also induced overexpression of Lst, which correlated with enhanced survival in serum killing assays, a protective effect suggestive of diminished complement deposition conveyed by LOS sialylation. Although cervical cell-adhesion promoted lst down-regulation in the wild type strain, these effects were CrgA-independent, suggesting the presence of multiple lst-specific regulators and indicating that, while cell-adhesion plays a large role in control of Tfp production, expression of Lst is predominantly important in planktonic bacteria.
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Details
- Title
- A tale of two regulators
- Creators
- Kathryn A. Matthias
- Contributors
- Richard F. Rest (Advisor) - Drexel University, Drexel University (1970-)
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- xv, 117 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- Microbiology and Immunology; College of Medicine; Drexel University
- Other Identifier
- 991021889076404721