Contribution of the vibrio parahaemolyticus chromosome I type III secretion system to colonization of the Pacific oyster, crassostrea gigas

点击翻译按钮获取中文摘要

Vibrio parahaemolyticus is a significant cause of gastroenteritis resulting from the consumption of raw or undercooked shellfish. V. parahaemolyticus accumulates in bivalve invertebrates, particularly oysters and mussels. There is a large amount of diversity within V. parahaemolyticus isolates, and the aresenal of factors required for virulence is not well understood. V. parahaemolytics does not cause disease in adult oysters, and is thought to be part of the oyster normal flora. The V. parahaemolyticus genome encodes two type III secretion systems. Type III secretion systems are mult-protein complexes used by Gram negative bacteria to inject proteins directly into the host cell. They are commonly found in animal and plant pathogens, and are considered important virulence factors. Surprisingly, data from our lab indicates that one of the type III secretion systems, the CI-T3SS, is found in both disease-associated and environmental isolates. This led us to hypothesize that the CI-T3SS is involved in colonization and survival within oysters. In this proposal, we examine the interaction between V. parahaemolyticus and the oyster immune system. Bacteria that live in close association with a host need to avoid recognition as foreign by the immune system. The oyster immune system is comprised of phagocytic cells called hemocytes. Our data suggests that V. parahaemolyticus evades phagocytosis, which could enable it to survive within the oyser. We will therefore examine whether the CI-T3SS plays a role in avoiding phagocytosis. A second aim is to determine whether the CI-T3SS is required for persistent colonization of the oyster. Collectively, these studies will allow us to better understand the marine lifestyle of V. parahaemolyticus. As virulence in V. parahaemolyticus is not well defined, methods for eliminating V. parahaemolyticus from oysters before they go to market is an important strategy to decrease the risk of disease. Understanding how V. parahaemolyticus persists in oysters will enhance our ability to develop these tools.