Nutrient Uptake during Anthrax Disease

项目摘要 病原菌需要获得必要的营养才能在其体内建立和维持感染 主持人。宿主限制获得这些营养物质，这一概念被称为营养免疫。因此， 细菌营养输入系统和管理它们的新陈代谢调节器代表着下一个- 新型抗菌剂的世代目标。致病原因是革兰氏阳性细菌炭疽杆菌 炭疽病病原体和生物恐怖主义武器。这种病原体有一种非凡的能力 在脊椎动物中复制，这一优点对于研究细菌如何克服营养 豁免权。众所周知， 支链氨基酸生物合成的倒数第二步， 是所有生命所必需的，需要一种活性依赖于铁-硫簇的酶。 我们的 已发表的研究和初步数据表明，炭疽杆菌和相关物种使用了一种聪明的 调节支链氨基酸摄入量与代谢平衡的代谢机制 在复杂的寄主环境中维持铁的稳态。在这样的前提下工作 当外部铁水平较低时，芽孢杆菌对缬氨酸具有营养缺乏性，因此不能分枝。 氨基酸，我们假设宿主从血液蛋白中释放的缬氨酸刺激铁的获取 通过革兰氏阳性细菌毒力的全球调节者科迪。这反过来又促进了进口 从而缓解营养缺乏症，促进宿主血液和组织的快速复制。在AIM 在本项目中，我们报道了一种新的支链氨基酸转运蛋白的发现，并对其进行了表征 它在Cody依赖的血红素铁获得刺激中的作用。在目标2中，我们调查了 细菌中两种新发现的血红素结合酶释放铁的机制。 最后，在目标3中，我们集成了中央模型的关键方面以确定这些方面的重要性 在炭疽病期间，细菌感染的每一步都有系统的影响。因为这个网络 营养摄取系统和调节剂在几个具有临床意义的物种中也有同源物， 这里的工作将提供病原菌如何在体内代谢的基础知识 致命性。

Project Summary Pathogenic bacteria need to acquire essential nutrients to establish and sustain an infection in their hosts. The host restricts access to such nutrients, a concept termed nutritional immunity. As such, bacterial nutrient import systems, and the metabolic regulators that govern them, represent next- generation targets for novel antimicrobials. The Gram-positive bacterium B. anthracis is the causative agent of anthrax disease and a weapon of bioterrorism. This pathogen has a remarkable ability to replicate in vertebrates, a virtue that is useful for the study of how bacteria overcome nutritional immunity. It is well known that the penultimate step in the biosynthesis of branched amino acids, which are necessary for all life, requires an enzyme whose activity is dependent on an iron-sulfur cluster. Our published work and preliminary data suggests that B. anthracis and related species employ a clever metabolic mechanism to govern the balance between the intake of branched amino acids and the maintenance of iron homeostasis in complex host environments. Working under the premise that bacillus is auxotrophic for valine when external iron levels are low, and thus cannot make branched amino acids, we hypothesize that host valine liberated from blood proteins stimulates iron acquisition via the global regulator of virulence in Gram-positive bacteria, CodY. This in turn promotes the import of iron, thereby relieving the auxotrophy and fueling rapid replication in host blood and tissues. In Aim 1 of this project, we report the discovery of a novel branched amino acid transporter and characterize its role in the CodY-dependent stimulation of heme-iron acquisition. In Aim 2, we investigate the mechanism of iron release from heme via two newly uncovered heme-binding enzymes in bacillus. Finally, in Aim 3, we integrate key aspects of the central model to determine the importance of these systems in every step of a developing bacillus infection during anthrax disease. Since this network of nutrient uptake systems and regulators also have homologs in several clinically significant species, the work here will provide fundamental knowledge of how pathogenic bacteria fuel their metabolism during virulence.