Honors Theses


Yvonne Sun



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Honors Thesis


Listeria monocytogenes is a foodborne pathogen commonly found in ready-to-eat deli and dairy products. This foodborne pathogen is responsible for the disease listeriosis, which disproportionately impacts immunocompromised individuals. This research aims to evaluate how natural intestinal environments influence the pathogenesis of Listeria. One particular environmental condition that has a well-documented effect on Listeria is varying levels of oxygen. Specifically, anaerobic exposure during the growth of Listeria greatly impacts subsequent intracellular pathogenesis. When grown and adapted under anaerobic conditions, Listeria overall exhibits decreased intracellular survival and decreased cell to cell spread. However, the presence of propionate, a natural byproduct of fermentation in the gut, is able to recover some of the virulence Listeria loses in anaerobic conditions. Hemolytic assays and qPCR were used to confirm that combined anaerobic and propionate exposure results in upregulation of the hly gene and LLO protein product. It is known that SigB plays a role in the stress response of Listeria. Interestingly, these results further suggest that the sigB gene is important in helping Listeria respond quite quickly to an environmental stressor, such as anaerobicity. Only two hours of anaerobic exposure resulted in notable upregulation of hly transcript levels in wild-type Listeria. Further experiments are needed to identify the complex role varying levels of anaerobic exposure has on the sigB gene and Listeria infections.

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Undergraduate research



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