CONTROL OF PROTECTIVE ANTIGEN SYNTHESIS BY B ANTHRACIS

为了成为成功的病原体，细菌需要有感知病原体的机制。 宿主环境、处理环境更改以及 适当的调整。 在许多细菌中， 毒力因子由一个共同的调节因子协调控制， 系统 病原体炭疽芽孢杆菌的毒力表达 炭疽热，代表了一个独特的例子，监管反应， 环境信号。 已知的B.炭疽病 三重外毒素和D-谷氨酰多肽胶囊， 仅在二氧化碳水平升高的体外生长期间， 含有碳酸氢盐的培养基。 重碳酸盐对毒素和 胶囊生产是特定的，而不仅仅是由于其缓冲 在细菌生长过程中。 该CO2/碳酸氢盐信号为 病原体侵入哺乳动物宿主的生理意义 组织中 该项目的长期目标是阐明 B中毒力基因表达的分子基础。炭疽病 毒素和 荚膜合成可能受反式作用因子的共同调节， CO2/碳酸氢盐信号。 这里描述的实验将探测pag的调节，pag基因用于 免疫原性毒素蛋白，保护性抗原。 转录本 基因会增加10到40倍。 B。炭疽 质粒pX 01是刺激pag转录所必需的。 我们将 鉴定影响PAG表达反式作用调节基因， 使用转座子介导的插入诱变并通过筛选pX 01 激活PAG报告基因的克隆文库。 监管 在pX 01上pag上游至少3 kb的基因座已经涉及 如保护性抗原合成所必需的。 这个地方，和其他 在这里提出的实验中确定的调控基因座，将是 其特征在于定义结构限制、排序、识别开放 阅读框和构建无效突变体。 影响 CO2/碳酸氢盐信号对调节基因功能和表达的影响将 接受检查。 将详细分析pag启动子： 将鉴定对CO2依赖性转录重要的序列。 这些实验将阐明B的成分。炭疽信号- 转导系统负责识别和传输 CO2/碳酸氢盐信号和可能的毒力因子全局控制 由这种有机体合成。 这项研究的结果将提高认识 宿主-寄生虫关系和信号转导的研究， 有关炭疽病发病机理的资料。

To be successful pathogens, bacteria require mechanisms for sensing the host environment, processing environmental changes, and making appropriate adaptations. In many bacteria, expression of disparate virulence factors is coordinately controlled by a common regulatory system. Virulence expression by Bacillus anthracis, the causative agent of anthrax, represents a unique example of a regulatory response to an environmental signal. The known virulence factors of B. anthracis, a tripartite exotoxin and a D-glutamyl polypeptide capsule, are produced in vitro only during growth under elevated levels of carbon dioxide in media containing bicarbonate. The effect of bicarbonate on toxin and capsule production is specific, and not simply due to its buffering capacity during bacterial growth. This CO2/bicarbonate signal is of physiological significance for a pathogen which invades mammalian host tissues. the long-term goal of this project is to elucidate the molecular basis for virulence gene expression in B. anthracis. Toxin and capsule synthesis may be co-regulated by trans-acting factors in response to the CO2/bicarbonate signal. Experiments described here will probe the regulation of pag, the gene for the immunogenic toxin protein, protective antigen. Transcription of this gene increases 10 to 40-fold in response to bicarbonate. B. anthracis plasmid pX01 is required for stimulation of pag transcription. We will identify trans-acting regulatory genes that affect expression of pag by using transposon-mediated insertional mutagenesis and by screening a pX01 library for clones which activate a pag reporter gene. A regulatory locus at least 3 kb upstream from pag on pX01 has already been implicated as necessary for protective antigen synthesis. This locus, and other regulatory loci identified in experiments proposed here, will be characterized by defining structural limits, sequencing, identifying open reading frames, and constructing null mutants. Effects of the CO2/bicarbonate signal on regulatory gene function and expression will be examined. The pag promoter will be analyzed in detail: upstream sequences important for CO2-dependent transcription will be identified. These experiments will elucidate components of the B. anthracis signal- transduction system responsible for recognition and transmission of the CO2/bicarbonate signal and possibly global control of virulence factor synthesis by this organism. Results of this study will enhance awareness of host-parasite relationships and signal transduction and provide information relevant to the pathogenesis of anthrax disease.