Part of the lab focuses on why injured epithelium is particularly susceptible to colonization and damage by the opportunistic pathogen P. aeruginosa. Initially we carried out a novel genetic screen to identify mutants that are deficient in injuring epithelial cells in vitro. This analysis has revealed that pili and products of a novel secretion system (type III secretion), are required for host cell injury by P. aeruginosa and identified a new cytotoxin, ExoU. C urrently, our work focuses on several aspects of P. aeruginosa-host cell interactions. First, we are further characterizing the pathway(s) by which P. aeruginosa interacts with the apical and basolateral surfaces of polarized and non-polarized epithelial cells in both 2 dimensional and 3 dimensional cultures. Second, we have applied genome-wide RNAi-based screens to identify host genes required for binding, uptake, and type III secretion-mediated cytotoxicity. Third, we are dissecting the ability of the type III secreted toxin ExoT to inhibit wound healing and in doing so, have uncovered several unexpected aspects of ExoT biology. Fourth, we are continuing our studies on the regulation of type III secretion and of type IV pilin biogenesis and twitching motility. Together, these studies will expand our knowledge of bacterial pathogenesis, host cell injury, and pilin function and may identify new targets for drug and vaccine development.

C . trachomatis is the leading cause of venereal disease and preventable sterility in the United States and the most common cause of non-congenital blindness in third world countries. It replicates via a unique developmental cycle involving the serial alternation of two distinct forms sequestered within a membrane bound compartment (the "vacuole") in the cytoplasm of the infected epithelial cell. While this organism presents major experimental challenges, its importance as a human pathogen merits overcoming the difficulty in manipulating and growing the bacteria in the laboratory. Our recent studies have been aimed at studying the interactions between C. trachomatis and the host epithelial cell. We have applied genome-wide RNAi-based screens to identify host factors required for early steps in the infection process.