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Characterization of a novel Francisella tularensis Virulence Factor Involved in Cell Wall Repair

Zellner, Briana Collette
http://rave.ohiolink.edu/etdc/view?acc_num=mco1576256855120062

Abstract Details

2019, Doctor of Philosophy (PhD), University of Toledo, Biomedical Sciences (Medical Microbiology and Immunology).
Francisella tularensis, the causative agent of tularemia, is one of the most dangerous bacterial pathogens known. F. tularensis has a low infectious dose, is easily aerosolized, and induces high morbidity and mortality; thus, it has been designated as a Tier 1 Select Agent. Studies to identify and characterize F. tularensis envelope proteins are important to help understand the molecular mechanisms by which F. tularensis, and other intracellular pathogens cause disease, and may lead to the development of new therapeutics. In previous studies, we demonstrated that the F. tularensis disulfide bond formation protein ortholog, DsbA, is required for virulence and, more importantly, identified >50 DsbA substrates, half of which are annotated as hypothetical proteins or proteins with unknown functions. In the current study, we selected one of these unstudied DsbA substrates, FTL1678, for detailed analysis. Using bioinformatics, FTL1678 was found to contain a putative L,D-carboxypeptidase A (LdcA) domain, indicating a potential role in peptidoglycan (PG) remodeling, which likely is required for the intracellular lifestyle of F. tularensis. Unlike prototypic LdcA homologs, F. tularensis LdcA does not localize to the cytoplasm. An FTL1678 mutant was completely attenuated in a mouse pulmonary infection model, with decreased lung colonization and inability to disseminate to livers or spleens. Mutant attenuation was confirmed through complementation with wild-type (WT) FTL1678, as well as the Campylobacter jejuni LdcA homolog Pgp2, and both fully-restored virulence to WT levels. Importantly, immunization with this mutant provided significant protection against pulmonary challenge with fully-virulent F. tularensis strain SchuS4 (in the BSL3). Membrane integrity testing revealed differences in cell wall permeability between WT F. tularensis Live Vaccine Strain (LVS) and ΔFTL1678 and electron microscopy analysis of ΔFTL1678 showed increased outer membrane thickness. In addition, through enzymatic assays, FTL1678 was shown to have L,D-carboxypeptidase and L,D-endopeptidase activities, cleaving peptidoglycan pentapeptides to tetrapeptides and tripeptides. These studies have revealed a new F. tularensis virulence factor and have highlighted the importance of the F. tularensis envelope in protecting the bacterium during infection.
Jason Huntley, PhD (Advisor)
R. Mark Wooten, PhD (Committee Member)
R. Travis Taylor, PhD (Committee Member)
Jyl Matson, PhD (Committee Member)
Robert Blumenthal, PhD (Committee Member)
201 p.
Immunology; Microbiology

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Citations

  • Zellner, B. C. (2019). Characterization of a novel Francisella tularensis Virulence Factor Involved in Cell Wall Repair [Doctoral dissertation, University of Toledo]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=mco1576256855120062

    APA Style (7th edition)

  • Zellner, Briana. Characterization of a novel Francisella tularensis Virulence Factor Involved in Cell Wall Repair . 2019. University of Toledo, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=mco1576256855120062.

    MLA Style (8th edition)

  • Zellner, Briana. "Characterization of a novel Francisella tularensis Virulence Factor Involved in Cell Wall Repair ." Doctoral dissertation, University of Toledo, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=mco1576256855120062

    Chicago Manual of Style (17th edition)

mco1576256855120062
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© 2019, all rights reserved.
This open access ETD is published by University of Toledo Health Science Campus and OhioLINK.