I am applying for this K08 award to help me fulfill my long-term career objective of become an independent investigator in the field of Infectious Disease. The K08 award will allow me the time to obtain, in a mentored environment, the knowledge base and experience I will need to realistically be able to make the difficult transition from clinician to physician-scientist. My interest in infectious diseases, pathophysiology, and biochemistry has lead me to the project I am proposing for this grant and my fellowship. Clostridium difficile is the major cause of nosocomial diarrhea in the United States. The disease appears to be the results of the action of one toxin animal models, toxin A. Toxin A's mechanisms of action are not entirely understood, but recent studies have identified the Rho family of small GTPases as intracellular targets of toxin A. Rho proteins are involved in regulation of the actin cytoskeleton and gene transcription. Toxin A glucosylates these proteins at a crucial threonine residue, thus inactivating them. The biochemistry of this reaction and the exact role it plays in the pathogenesis of the disease is unclear. We propose the following aims for this grant: 1) develop an in vitro assay for the toxin A-mediated Rho glucosylation; 2) characterize the biochemistry of the reaction; 3) develop inhibitors for the reaction. The inhibitors would then be used to probe the effect of blocking the glucosylation of the known sequella of toxin A exposure in culture cells and eventually could serve as a novel, non-antibiotic therapy for the disease. The environment at the University of Virginia and in the lab of my sponsor is ideal for my development as an independent researcher. My sponsor has expertise in small GTPases and toxin A research; there also are renowned researchers in diarrheal pathogenesis in the division, and through collaborations with outside researchers, from whom advice can be sought. There are numerous opportunities for course work to expand my knowledge base and excellent research facilities with all the necessary equipment needed to conduct my work. Most importantly, the division of Infectious Diseases and the university have a long tradition of fostering the environment necessary to develop competent academic physicians.