Rachel Shi

Date of Award


First Advisor

Erin McMullin

Second Advisor

David Myers


Of the many mutualistic symbioses across the Eukarya domain, perhaps the symbiotic relationship between the host and intestinal bacteria, in particular, is one of the most dynamic, complex, and vigorously studied. Bacterial populations exist on all surfaces and within every orifice of the human body and vastly outnumber human cells. Humans and their inhabiting microorganisms, collectively known as the microbiota, have co-evolved and adapted to engage in a balanced exchange that produces pronounced biological benefits. For instance, enteric bacteria receive nourishment, protection, and a warm, suitable habitat for development while humans obtain additional nutrients, protection from harmful pathogens, and immunological modulation. My thesis investigates the biochemical and cellular interactions within the gut microbiota in both healthy and disease states of the digestive, immune, and nervous systems. Enteric bacteria intercept and contribute to many pathways involving digestion, immunity, and neuroendocrine function through a bidirectional crosstalk involving metabolites and other bioactive molecules. Certain microbial compositions and metabolic patterns have been associated with particular illnesses, and the concept of an ideal and healthy microbiome is gaining increasing medical and popular attention. While microbiome-related therapies are only recently surfacing in the landscape of accepted clinical treatments, there is under-recognized value in understanding the undeniable role of the microbiota in human health and illness.

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