The physiological activation and consequences of Toxin-Antitoxin systems in Salmonella

项目总结/摘要 细菌控制其生长以应对环境挑战，有时会进入生长停滞期。 状态生长停滞的细菌通常显示出在暴露于抗生素的情况下存活的非凡能力， 作为抗生素坚持者。这些细菌持续存在被认为有助于许多感染的复发， 抗微生物药物耐药性带来的负担。了解细菌如何建立这种增长被逮捕 国家可以帮助开发更好的抗生素。毒素-抗毒素（TA）模块是广泛存在的基因对 参与细菌生长控制。它们是压力反应系统，使细菌能够适应它们的 生长响应于诸如噬菌体或宿主免疫防御细胞的攻击的损伤。TA系统编码非 一种分泌毒素，其抑制基本细胞功能，从而控制生长，以及一种抗毒素， 中和毒素抗毒素通过抑制表达在两个水平上控制毒素 和直接中和。据认为，在压力下，抗毒素被降解，一方面去抑制 操纵子的表达，另一方面释放毒素。然而，尽管有许多研究表明， 毒素的功能，很少有关于应激如何导致TA系统激活的信息，从“去- TA操纵子的“抑制”和毒素的释放对毒素对细胞的活性的实际结果起作用。 细菌;而这些无处不在的元素的作用仍然存在争议。工作的基础是我们的先验 证明巨噬细胞对鼠伤寒沙门氏菌的摄取是表达的自然触发， 细菌编码的每个TA模块的活性。利用基因，生化， 结构和成像方法，我们将利用这个强大的触发器来研究TA系统如何 TacAT基团被激活（目的1中的去阻遏和目的2中的毒素释放），并且生理上的 Tac毒素对环境对细菌的攻击做出反应的活性的后果 （目标3中的中毒和目标4中的中毒影响）。所产生的知识无疑将提供 深入了解Tac家族以外的其他TA系统。此外，它有可能改变我们的 了解细菌生长异质性和抗生素持久性的相关现象， 作为开发更好抗生素的跳板。

PROJECT SUMMARY/ABSTRACT Bacteria control their growth in response to environmental challenges and sometimes enter a growth arrested state. Growth-arrested bacteria often show remarkable abilities to survive exposure to antibiotics and are known as antibiotic persisters. These bacterial persisters are thought to contribute to the relapse of many infections and to the worrying burden of antimicrobial resistance. Understanding how bacteria establish this growth arrested state can help to develop better antibiotics. Toxin-Antitoxin (TA) modules are widespread pairs of genes involved in bacterial growth control. They are stress responsive systems that enable bacteria to adapt their growth in response to insults such as attack by phage or host immune defense cells. TA systems encode a non- secreted toxin which inhibits an essential cellular function thereby controlling growth, and an antitoxin that neutralizes the toxin. The antitoxin exerts control over the toxin at two levels, through repression of expression and direct neutralization. It is thought that upon stress, the antitoxin is degraded, on one hand de-repressing expression of the operon, and on the other hand liberating the toxin. However, despite numerous studies on toxin functions, very little information is available on how stresses lead to activation of TA systems, from “de- repression” of the TA operon and liberation of the toxin to actual consequences of the activity of the toxin on the bacteria; and the role of these ubiquitous elements remains disputed. The foundation of the work is our prior demonstration that uptake of Salmonella Typhimurium by macrophages is a natural trigger of expression and activity of each of the TA modules encoded by the bacteria. Using a combination of genetic, biochemical, structural and imaging approaches, we will take advantage of this powerful trigger to study how TA systems of the TacAT group are activated (de-repression in aim 1 and liberation of the toxin in aim 2) and the physiological consequences of the activity of Tac toxins in response to attacks inflicted on bacteria by their environment (intoxication in aim 3 and effects of intoxication in aim 4). The knowledge generated will undoubtedly provide insight on other TA systems beyond the Tac family. In addition, it has the potential to transform our understanding of bacterial growth heterogeneity and the associated phenomenon of antibiotic persistence and serve as a springboard to develop better antibiotics.