Elucidation of colonization and virulence through a novel comparative approach

描述（由申请人提供）：紧急人类病原体副溶血性弧菌是世界范围内胃肠炎的主要原因。虽然已经确定了一些毒力机制，但这些机制并不能完全解释这种病原体引起疾病的能力。在这项研究中，我们将通过一种新的比较方法阐明有助于定植和毒力的机制。包括副溶血性弧菌在内的人类致病性弧菌的一个共同特征是，它们的许多毒力因子是水平获得的，但获得性毒力特征必须与其他定殖特征协调调节。彻底地针对所有独特的序列将是低效的，并且对连接毒力和定植的调控网络也没有什么帮助。我们建议将这种病原体与一种不能引起疾病的相关细菌（如表征良好的光器官共生体费氏弧菌）之间的定殖进行比较，将表明哪些定殖机制在该属中是古老且保守的。更重要的是，这种新颖的比较将揭示副溶血性弧菌致病生活方式的独特调控转录本。我们推测，副溶血性弧菌中不受gaca调控或在费氏弧菌中缺失的gaca调控基因有助于副溶血性弧菌的毒力和定植。我们的假设和预测基于以下事实：1)在包括霍乱毒素在内的致病性弧菌中水平获得的毒力因子是由整个属中保守的调节因子控制的，包括共生细菌，费氏弧菌；2)GacA调节费氏弧菌的共生因子和宿主定植，以及包括霍乱弧菌在内的许多病原体的毒力和定植。3)在所有弧菌（lux）中不保守的关键共生因子在费氏弧菌中受GacA调控，表明生活方式特异性性状与该调控有关。这项研究的具体目的是：

DESCRIPTION (provided by applicant): The emergent human pathogen Vibrio parahaemolyticus is a major cause of gastroenteritis worldwide. Although some virulence mechanisms have been identified, these do not fully explain the ability of this pathogen to cause disease. In this study we will elucidate mechanisms that contribute to colonization and virulence by a novel comparative approach. A common feature of human pathogenic Vibrios, including V. parahaemolyticus, is that many of their virulence factors are horizontally acquired, and yet acquired virulence traits must be coordinately regulated along with other colonization traits. Exhaustively targeting all unique sequences would be inefficient, and would provide little insight into regulatory networks that connect virulence and colonization. We propose that a comparison of colonization between this pathogen and a related bacterium that is incapable of causing disease, such as the well characterized light organ symbiont Vibrio fischeri, will indicate which mechanisms of colonization are ancient and conserved in the genera. More importantly, the novel comparison will reveal uniquely regulated transcripts that contribute specifically to the pathogenic lifestyle of V. parahaemolyticus. We hypothesize that GacA-regulated genes in V. parahaemolyticus that are not GacA-regulated or absent in V. fischeri contribute to the virulence and colonization by V. parahaemolyticus. We base our hypothesis and predictions on the fact that 1) horizontally acquired virulence factors in pathogenic Vibrios including cholera toxin are controlled by regulators conserved throughout the genus including the symbiotic bacterium, Vibrio fischeri, 2) GacA regulates symbiosis factors and host-colonization in V. fischeri and virulence and colonization in many pathogens including Vibrio cholerae, 3) key symbiotic factors that are not conserved in all Vibrios (lux) are regulated by GacA in V. fischeri indicating lifestyle-specific traits map to this regulon. The specific aims of the study are to: * Generate a global colonization-defective strain of V. parahaemolyticus through a mutation in GacA. * Use comparative DNA array analysis of GacA regulons in V. fischeri and V. parahaemolyticus to identify putative colonization and virulence traits. * Determine the role of targeted GacA-regulated genes in cytotoxicity. PUBLIC HEALTH RELEVANCE: The last decade marked the emergence of a pandemic strain of V. parahaemolyticus, which caused outbreaks in regions that were previously not considered to be at risk, foreshadowing the increasing threat to human health due to climate changes. A major obstacle to assessing risk of infection and developing preventative protocols is a lack of understanding of the pathogenicity of V. parahaemolyticus. Our findings will provide invaluable insight into the virulence mechanisms of this important emergent pathogen revealing host vulnerabilities and providing new opportunities to prevent and treat infections.