CONTROL OF ENTEROTOXIN GENE EXPRESSION IN S AUREUS

描述(改编自申请人的摘要：金黄色葡萄球菌是一种 人类疾病的主要原因，尤其是医院感染。它也是世界上 美国确认的细菌性食源性疾病的第三大常见原因 各州。生物体产生一种或多种血清学上不同的肠毒素。 当生长在食物中并摄取预制毒素时 用于呕吐和腹泻症状，这是 葡萄球菌食物中毒。尽管它通常与食物联系在一起 中毒时，肠毒素也是该细菌的毒力因子。这个 毒素作为超抗原，可以诱导多克隆T细胞 感染者体内的激活。这种激活会降低容量 对细菌产生适当的免疫反应 感染。许多肠毒素的表达，就像其他 金黄色葡萄球菌的毒力相关外毒素在被激活时被增强 辅助基因调控(Agr)网络。AGR系统包括两个组成部分 在金黄色葡萄球菌中起法定感应器作用的调节系统。它是 认为这个系统在一段时间内最大限度地产生外毒素 宿主对病毒的炎症反应时的感染过程 感染和有机体必须做出反应才能击退吞噬细胞。 与此一致的是agr突变体的发现，它不能激活 外毒素的产生，其毒性明显低于野生型亲本 紧张。本项目利用肠毒素B和D基因作为模型系统 以确定AGR系统如何激活外毒素表达。短的 这些肠毒素基因启动子区域的DNA片段已经被 定位在氯霉素乙酰转移酶报告基因前面， 已经被证明包含与agr相关的激活所必需的序列。 表达的方式。在这个项目中，特定部位的突变将被引入到 负责AGR激活的序列和特定碱基如下 已确认身份。负责加强的管制物种的性质 表达将被识别。相互作用的分子本质 将确定效应物种类和肠毒素基因启动子。这个 RNAIII的特定作用，效应物种首先产生的初始 两组分系统的激活将根据以下方面进行评估 增强肠毒素基因的表达。

Description (Adapted from applicant's abstract: Staphylococcus aureus is a major cause of human disease, especially nosocomial infections. It is also the third most common cause of confirmed bacterial food borne disease in the United States. The organism produces one or more serologically distinct enterotoxins when growing in food and the ingestion of the preformed toxin is responsible for the vomiting and diarrhea symptomology which is the hallmark of staphylococcal food poisoning. Despite its usual association with food poisoning, the enterotoxins are also virulence factors for the bacterium. The toxins, by virtue of being superantigens, can elicit a polyclonal T-cell activation in an infected individual. This activation diminishes the capacity of the individual to mount an appropriate immune response against the bacterial infection. Expression of many of the enterotoxins, like that of other virulence-associated exotoxins of S. aureus, is enhanced when activated by the accessory gene regulator (agr) network. The agr system involves a two component regulatory system which functions as a quorum sensor in S. aureus. It is thought that this system maximizes exotoxin production at a time in the infectious process when the host is mounting an inflammatory-response to the infection and the organism must respond to fight off the phagocytic cells. Consistent with this are the findings that agr mutants, which cannot activate exotoxin production, are significantly less virulent than then wild-type parent strain. This project utilizes the enterotoxin B and D genes as a model system to determine how the agr system works to activate exotoxin expression. Short DNA fragments from the promoter region of these enterotoxin genes have been positioned in front of a chloramphenicol acetyltransferase reporter gene and have been shown to contain the sequences necessary for agr related activation of expression. In this project, site-specific mutations will be introduced into the sequence and the specific bases responsible for the agr activation will be identified. The nature of the regulatory species responsible for the enhanced expression will be identified. The molecular nature of the interaction between the effector species and the enterotoxin gene promoter will be defined. The specific role of RNAIII, the effector species first generated by the initial activation of the two component system, will be evaluated with regard to enhancement of enterotoxin gene expression.