Preliminary experiments employing the Mu<I>dlux</I> reporter system indicated that the <I>ahp</I> locus was osmotically sensitive in <I>S. typhimurium. </I>Studies on other bacteria supported this view. The affect of the osmotic environment of the cell upon the expression of <I>ahp</I> was therefore addressed in greater depth. The subsequent use of immunoblotting techniques conclusively demonstrated that chromosomal expression of the <I>ahp</I> locus was not affected by the osmotic environment surrounding the cell. Instead, the Mu<I>dlux</I> element was found to alter the natural behaviour of the <I>ahp</I> promoter in such a way that it adopted an osmotically-regulated status, and this mode of regulation appeared to override regulation via the normal hydrogen peroxide-inducible mechanism. <I>S. enterica </I>is an intracellular pathogen which is capable of surviving within macrophage cells. Macrophages are equipped with an arsenal of anti-microbial effector mechanisms, including a respiratory burst which generates reactive oxygen metabolites. Since <I>ahp</I> had previously been shown to respond to the respiratory burst of macrophages, this study also assessed the role of oxidative stress resistance genes in the virulence of <I>S. typhimurium. </I>Strains of the mouse pathogen Sl1344 were constructed in which the <I>ahp</I> and <I>oxyR</I> loci were disrupted and their virulence was assessed in LD<SUB>50</SUB> studies. Disruption of the <I>ahp </I>or <I>oxyR</I> loci was found to have no effect upon the gross virulence of SL1344 for mice, suggesting that these loci were not essential for survival within the macrophage. The ability to develop immunity against infection by <I>S. typhimurium </I>is thought to correlate with the development of immunity against bacterial antigens which are expressed <I>in vivo. </I>As a further part to this study, the immunological responses of mice to two <I>S. typhimurium-</I>derived polypeptides, AhpC and GroEL, following cloning and overexpression of these proteins, were examined. Mice previously infected with an attenuated strain of <I>S. typhimurium </I>were shown to elicit significant delayed-type hypersensitivity reactions following subcutaneous injection of these polypeptides 33 and 104 days post-infection. Moreover, AhpC-and GroEL-specific antibodies were detected during the course of infection of mice with <I>S. typhimurium. </I>
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:662778 |
| Date | January 1997 |
| Creators | Taylor, Patrick David |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/13083 |
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