Virulence Gene Expression by Bacillus anthracis

描述(申请人提供)：本提案侧重于炭疽芽孢杆菌毒力基因控制，重点是主要毒力基因调控因子AtxA的表达和功能。炭疽杆菌是一种发育细菌，以代谢活跃的营养细胞和休眠孢子两种不同的生理状态存在。孢子营养细胞周期在病程中起着重要的作用。孢子进入哺乳动物的宿主并萌发成为营养细胞。在感染期间，炭疽杆菌保持营养状态，并合成衣壳、炭疽毒素蛋白和其他促进致病的因素；不会产生孢子。然而，当寄主死亡时，营养细胞暴露在环境中，不会产生毒素和被膜，炭疽杆菌可以有效地萌发孢子。因此，毒力因子合成和产孢量之间的反向关系对炭疽病的发病具有重要的生理学意义。这两个过程之间的主要联系是Atxa。我们实验室和其他实验室的研究揭示了这种毒力基因表达的主要多效性调节因子与分批培养细胞的生理状态之间的关系。炭疽杆菌发育调节剂的同源物在非致病的枯草芽孢杆菌中已经被很好地描述了，它们与Atxa的转录有关。此外，Atxa的功能似乎受翻译后修饰和宿主相关信号的控制。在这项工作中，我们将(1)进行Atxa的功能分析，(2)确定控制Atxa表达的分子机制，以及(3)建立Atxa调节因子与Atxa蛋白在炭疽病中的特定功能修饰的生理相关性。炭疽杆菌是一种A类选择剂，开发更有效的炭疽病化疗药物、疫苗和诊断方法是国家的优先事项。明确和刻画炭疽杆菌控制毒力基因表达的分子机制，将有助于我们从根本上理解炭疽杆菌的致病机理，并为炭疽病防治措施的制定提供合理的途径。此外，有关新型调控因子AtxA的分子功能的信息将有助于我们全面了解基因调控机制。最后，本研究中获得的信息可以应用于其他感染源，因为炭疽杆菌是研究宿主-病原体相互作用、细菌中的环境信号和细菌生理的其他方面的多种特征的理想模型。 公共卫生相关性：炭疽杆菌是A类选择制剂，开发更有效的炭疽病化学疗法、疫苗和诊断方法是国家的优先事项。明确和刻画炭疽杆菌控制毒力基因表达的分子机制，将有助于我们从根本上理解炭疽杆菌的致病机理，并为炭疽病防治措施的制定提供合理的途径。探索炭疽杆菌毒素和衣壳基因表达的分子基础，结合动物研究评估关键调控因子的重要性，将填补关于炭疽杆菌发育的时空性质和宿主内毒力因子合成的关键知识空白。此外，本研究中获得的信息也可以应用于其他感染源，因为炭疽杆菌是研究宿主-病原体相互作用、细菌中的环境信号和细菌生理的其他方面的多种特征的理想模型。

DESCRIPTION (provided by applicant): This proposal focuses on Bacillus anthracis virulence gene control, with emphasis on the expression and function of the major virulence gene regulator AtxA. B. anthracis is a developmental bacterium existing in two distinct physiological states, metabolically active vegetative cells and dormant spores. The spore - vegetative cell cycle is of fundamental importance in pathogenesis. Spores enter a mammalian host and germinate to become vegetative cells. During infection, B. anthracis remains vegetative and synthesizes capsule, anthrax toxin proteins, and other factors that facilitate pathogenesis; sporulation does not occur. However, upon death of the host when vegetative cells are exposed to the environment, toxins and capsule are not produced and B. anthracis sporulates efficiently. Thus, the inverse relationship between virulence factor synthesis and sporulation is physiologically significant for anthrax pathogenesis. The major link between these two processes is AtxA. Investigations in our laboratory and others have revealed a relationship between this major pleiotropic regulator of virulence gene expression and the physiological state of cells grown in batch culture. B. anthracis homologues of developmental regulators that have been well-characterized in the non- pathogenic Bacillus species B. subtilis have been linked to transcription of atxA. Moreover, AtxA function appears to be controlled by post-translational modification and host-associated signals. In this work, we will (1) perform functional analyses of AtxA, (2) determine molecular mechanisms for control of atxA expression, and (3) establish the physiological relevance of atxA regulators and specific functional modifications of the AtxA protein in anthrax disease. B. anthracis is a Category A Select Agent and the development of more effective chemotherapeutics, vaccines, and diagnostics for anthrax disease is a national priority. Defining and characterizing the molecular mechanisms by which B. anthracis controls virulence gene expression will advance our fundamental understanding of B. anthracis pathogenesis and facilitate a rational approach for the development of anthrax countermeasures. Furthermore, information regarding the molecular function of the novel regulator AtxA will contribute to our overall understanding of mechanisms of gene regulation. Finally, information obtained in this study can be applied to other infectious agents because B. anthracis is an ideal model for multiple features of host-pathogen interactions, environmental signaling in bacteria, and other aspects of bacterial physiology. PUBLIC HEALTH RELEVANCE: B. anthracis is a Category A Select Agent and the development of more effective chemotherapeutics, vaccines, and diagnostics for anthrax disease is a national priority. Defining and characterizing the molecular mechanisms by which B. anthracis controls virulence gene expression will advance our fundamental understanding of B. anthracis pathogenesis and facilitate a rational approach for the development of anthrax countermeasures. Exploration of the molecular basis for toxin and capsule gene expression in B. anthracis in combination with animal studies assessing significance of key regulators will fill a critical gap in knowledge regarding the spatial and temporal nature of B. anthracis development and virulence factor synthesis within the host. Furthermore, information obtained in this study can be applied to other infectious agents because B. anthracis is an ideal model for multiple features of host-pathogen interactions, environmental signaling in bacteria, and other aspects of bacterial physiology.