Honors Theses


Yvonne Sun, Ph.D.



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Honors Thesis


Listeria monocytogenes is a facultative foodborne pathogen that can enter the bloodstream and invades the central nervous system to cause meningitis. As an intracellular pathogen, L. monocytogenes replicates inside the host cell cytosol and avoids extracellular immune defenses as it disseminates throughout the body. L. monocytogenes can also reach and cross the blood brain barrier, resulting in severe or fatal symptoms in immunocompromised and elderly patients. The overarching goal of my research project is to better understand how different environmental factors, anaerobicity and propionate, in the intestinal lumen alter the ability of L. monocytogenes to cause infections. In the first aim of my thesis research, I investigated how anaerobicity and propionate affected L. monocytogenes central metabolism by measuring acetoin production, which is a proxy for pyruvate metabolism, and culture pH, which is a proxy for lactic acid production. I also compared these measurements between different strains to identify the potential genetic regulations underlying L. monocytogenes responses to anaerobicity and propionate. In the second aim, I examined the effect of anaerobicity and propionate on L. monocytogenes infection and intracellular growth in a model host cell line for neuronal cells, the Neuro-2A cells. Additionally, I investigated the intracellular growth differences between different strains to identify strain-dependent variations. Through this project, further findings were discovered about how anaerobicity and propionate exposure influence L. monocytogenes metabolism and infections, allowing for better understanding of how this pathogen might behave during and after intestinal transit.

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Undergraduate research