(p)ppGpp 介导的严谨反应是细菌应对环境或营养胁迫的多种策略之一，对逆境生存起到了重要作用。本实验室通过对胸膜肺炎放线杆菌(APP)S-8株全基因组测序，鉴定到与启动细菌严谨反应的信号素分子[(p)ppGpp]合成与分解相关的relA/spoT基因，其是否能够调控APP在肺部氨基酸饥饿状态下的宿主适应性及致病性，目前尚不清楚。本项目拟通过接合转移同源重组的方法，构建S-8株的relA/spoT双基因缺失株，通过比较野生株、缺失株及功能互补株在饥饿状态下生长曲线、生物被膜形成能力、糖代谢能力、菌体形态等生理适应性差异，分析ppGpp的生理功能；通过比较仔猪感染试验，确定ppGpp对APP致病性的影响；通过比较转录组及蛋白质组学差异，探讨其调控机制。通过对ppGpp的生理功能和调控机制的研究，增加对APP适应性及致病机制的认识，为猪传染性胸膜肺炎的防治及疫苗研究提供新的理论基础和思路。

Actinobacillus pleuropneumoniae （APP）is the etiologic agent of porcine contagious pleuropneumoniae, a lethal respiratory infectious disease leading to great economic losses to the global swine industry. The strigent response regulated by (p)ppGpp is one of the strategies adopted by bacteria when encounted enviromental and vegetative stress. (p)ppGpp is a well known intracellular signal that mediates bacterial stringent response to environment stresses through the change of its concentration level thus controls many important cellular processes for bacterial survival. S-8 strain was isolated from swine lung in China by our lab, RelA and SpoT, which encodes both (p)ppGpp synthetase and hydrolase, were identified from the draft genome sequence sequenced by our lab, ppGpp is thought to bind to and alter the affinity of RNA polymerase for various promoters, such as those associated with adaptation to adverse conditions. However, whether the ppGpp also could regulate the duration ability to hash environments and pathogenesis of Actinobacillus pleuropneumoniae under nutrient deprivation in lung was unknown. In this project, we constructed the mutants deficient in stringent response by homologous recombination, and then analyze the physiological function of ppGpp by comparing the growth character,the ability of forming biofilm, the carbohydrate metabolic ability,the morphology change of wild-type and mutant under different conditions, and analyze the regulatory mechanism by identifying the difference of proteome and transcriptome, and determined the influence to pathogenesis by infected piglets with wild-type and mutant. We hope that our work could shed new light to the pathogenesis of APP by investigating the physiological function and regulatory mechanism of ppGpp, and then providing new theoretical foundation and ideas for the control, drug discover, vaccine development of APP.