CONTROL OF ENTEROTOXIN GENE EXPRESSION IN S AUREUS

金黄色葡萄球菌肠毒素基因表达的控制

• 批准号: 6170400
• 负责人: GEORGE C. STEWART
• 金额: $ 11.61万
• 依托单位: KANSAS STATE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-07-01 至 2004-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6170400
• 关键词: Staphylococcus aureus; bacterial genetics; enterotoxins; gene expression; gene mutation; genetic promoter element; protein purification; regulatory gene; site directed mutagenesis

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.

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，特别是医院感染的主要原因。这也是 美国确认的细菌性食源性疾病的第三大常见原因 国家。该生物体产生一种或多种血清学上不同的肠毒素 当在食物中生长并且摄入预先形成的毒素时 呕吐和腹泻症状是该病的标志 葡萄球菌食物中毒。尽管它通常与食物联系在一起 中毒时，肠毒素也是细菌的毒力因子。这 毒素作为超级抗原，可以引发多克隆 T 细胞 在受感染的个体中激活。这种激活会降低容量 个体对细菌产生适当的免疫反应 感染。许多肠毒素的表达，与其他肠毒素一样 金黄色葡萄球菌的毒力相关外毒素在被 辅助基因调节器（agr）网络。 agr 系统包括两个组成部分 调节系统，在金黄色葡萄球菌中充当群体传感器。这是 认为该系统在同一时间最大化外毒素的产生 当宿主对病毒产生炎症反应时的感染过程 感染和生物体必须作出反应以抵抗吞噬细胞。 与此一致的是 agr 突变体的发现，它不能激活 外毒素产生，毒性明显低于野生型亲本 拉紧。该项目利用肠毒素 B 和 D 基因作为模型系统 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 片段已被 位于氯霉素乙酰转移酶报告基因的前面并且 已被证明含有 agr 相关激活所需的序列 的表达。在这个项目中，位点特异性突变将被引入 负责 agr 激活的序列和特定碱基将是 确定。负责增强的监管物种的性质 表达式将被识别。相互作用的分子性质 将定义效应物种和肠毒素基因启动子。这 RNAIII 的特定作用，效应子种类首先由初始产生 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。