Project Summary/Abstract The bacterium Vibrio parahaemolyticus (VP) is a leading cause of seafood-borne gastroenteritis on a pandemic scale. In the United States, it is a CDC-reportable emerging human pathogen with increasing annual morbidity and mortality rates. Diseases caused by pathogenic VP strains have important implications for global food safety and sustainability in relation to human health. Most commonly, human disease prevention has focused on the detection and reduction of VP in food sources. Despite this, human VP infection rates are still rising. Little is known about how VP interacts with its marine animal hosts. A better understanding of this relationship has the potential to lead to the development of methods to either prevent bacterial-animal host association and/or enhance bacterial removal from the host prior to human consumption, thereby mitigating the occurrence of human disease. We propose to use oysters, a natural host of VP and a common route of transmission to humans, as an animal model system to understand when and how VP interacts with them. It is hypothesized that A) VP will localize to specific tissues in the oyster and B) specific genes will be critical for the ability of VP to colonize oysters. The proposed work is strengthened by our collaborative research team, which is comprised of four scientists with expertise in molecular bacteriology, shellfish aquaculture, animal pathology and bioinformatics methods. The novel information gained from this research will lead to a more reliable laboratory-based oyster model system that will lay the foundation for future work to establish the roles environmental factors, including the resident microbiome, host genetics and specific bacterial gene products play in VP-oyster interactions. The refined oyster model will be applicable not only for VP but for other pathogenic Vibrio species, leading to improved methods to prevent human food-borne disease acquisition.