Dr. Theriot's lab studies the interactions between infectious bacteria and the human host cell actin cytoskeleton. Listeria monocytogenes and Shigella flexneri are unrelated food-borne bacterial pathogens that share a common mechanism of invasion and actin-dependent intercellular spread in epithelial cells. Their studies fall into three broad areas: the biochemical basis of actin-based motility by these bacteria, the biophysical mechanism of force generation, and the evolutionary origin of pathogenesis.