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

项目摘要/摘要 细菌控制自己的生长以应对环境挑战，有时会进入生长受阻的状态 州政府。生长受阻的细菌通常表现出在抗生素下存活的非凡能力，并已知 随着抗生素的持续存在。这些细菌持久者被认为有助于许多感染的复发和 令人担忧的抗菌素耐药性负担。对细菌如何建立这种生长的理解受阻 国家可以帮助开发更好的抗生素。毒素-抗毒素(TA)模块是一对广泛存在的基因 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 对诸如噬菌体或宿主免疫防御细胞的攻击等侮辱做出反应的生长。TA系统编码一个非 一种分泌毒素，通过抑制基本的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对毒素进行控制。 和直接中和。人们认为，在压力下，抗毒素会被降解，一方面会解除抑制 一方面表达操纵子，另一方面释放毒素。然而，尽管有许多关于 关于毒素的功能，关于应激如何导致TA系统激活的信息很少。 TA操纵子的抑制和毒素的释放对毒素活性的实际影响 细菌；而这些无处不在的元素的作用仍然存在争议。这项工作的基础是我们的前辈 证明巨噬细胞摄取鼠伤寒沙门氏菌是表达和 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，我们将利用这一强大的触发器来研究TA系统如何 TacAT组被激活(目标1解除抑制，目标2释放毒素)和生理 Tac毒素活性对环境对细菌攻击的影响 (目标3中的醉酒和目标4中的醉酒的影响)。所产生的知识无疑将提供 对Tac家族以外的其他TA系统的洞察。此外，它还有可能改变我们的 了解细菌生长的异质性和抗生素持久性和相关性现象 作为开发更好的抗生素的跳板。

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.