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

副溶血性弧菌是由进食生或未煮熟的贝类引起的胃肠炎的重要原因。副溶血性弧菌在双壳类无脊椎动物体内聚集，特别是牡蛎和贻贝。副溶血性弧菌分离株中存在大量的多样性，毒力所需的各种因子的重要性还不是很清楚。副溶血素在成年牡蛎中不会引起疾病，被认为是牡蛎正常菌群的一部分。副溶血性弧菌基因组编码两种III型分泌系统。III型分泌系统是革兰氏阴性细菌用来将蛋白质直接注入宿主细胞的多蛋白质复合体。它们普遍存在于动植物病原体中，被认为是重要的毒力因子。令人惊讶的是，来自我们实验室的数据表明，在疾病相关和环境分离株中都发现了一种III型分泌系统，CI-T3SS。这导致我们假设CI-T3SS与牡蛎内的定植和生存有关。在这项建议中，我们研究了副溶血性弧菌和牡蛎免疫系统之间的相互作用。与宿主密切相关的细菌需要避免被免疫系统识别为外来细菌。牡蛎的免疫系统由被称为血细胞的吞噬细胞组成。我们的数据表明，副溶血性弧菌可以逃避吞噬作用，这可能使它能够在牡蛎体内存活。因此，我们将研究CI-T3SS是否在避免吞噬方面发挥作用。第二个目标是确定CI-T3SS是否是牡蛎持续定居所必需的。总的来说，这些研究将使我们能够更好地了解副溶血性弧菌的海洋生活方式。由于副溶血性弧菌的毒力尚未明确，因此在牡蛎上市前消除副溶血性弧菌的方法是降低发病风险的重要策略。了解副溶血性弧菌是如何在牡蛎中存活的，将增强我们开发这些工具的能力。

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.