Virulence Gene Expression by Bacillus anthracis

描述（由申请人提供）：本课题主要研究炭疽芽孢杆菌毒力基因调控，重点研究主要毒力基因调控因子AtxA的表达和功能。炭疽芽胞杆菌是一种发育性细菌，存在于两种不同的生理状态，代谢活跃的营养细胞和休眠的孢子。孢子-营养细胞周期在发病机制中起着至关重要的作用。孢子进入哺乳动物宿主并发芽成为营养细胞。在感染过程中，炭疽芽胞杆菌保持营养状态，合成荚膜、炭疽毒素蛋白等促进发病的因子；不会产生孢子。然而，在宿主死亡后，当营养细胞暴露于环境中时，毒素和荚膜不能产生，而炭疽芽孢杆菌有效地繁殖。因此，毒力因子合成与产孢之间的反比关系对炭疽的发病具有重要的生理意义。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已经揭示了这种主要的多效性毒力基因表达调节剂与批量培养中生长的细胞的生理状态之间的关系。在非致病性芽孢杆菌种枯草芽孢杆菌中，炭疽芽孢杆菌发育调节因子的同源物已被很好地表征，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调节因子的生理相关性和AtxA蛋白在炭疽疾病中的特异性功能修饰。炭疽杆菌是一种a类选择性病原体，开发更有效的炭疽化疗药物、疫苗和诊断方法是国家的优先事项。明确和表征炭疽芽胞杆菌控制毒力基因表达的分子机制将促进我们对炭疽芽胞杆菌发病机制的基本认识，并为制定炭疽对策提供合理的方法。此外，关于新的调节因子AtxA的分子功能的信息将有助于我们对基因调控机制的全面理解。最后，本研究获得的信息可以应用于其他感染因子，因为炭疽芽胞杆菌是宿主-病原体相互作用、细菌环境信号传导和细菌生理学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.