Salmonella Pullorum is a pathogen specific to birds that can cause Pullorum disease in young chickens and lead to considerable economic losses in the poultry industry. During transmission and infection, S. Pullorum will encounter various environmental stresses and host defenses. The stringent response is an important adaptation response induced by (p)ppGpp, and in Salmonella, (p)ppGpp is synthesized by two (p)ppGpp synthetases, RelA and SpoT. To investigate the role of (p)ppGpp synthetases in the adaptation and pathogenicity of S. Pullorum, a (p)ppGpp synthetases mutant (ΔrelAΔspoT) was constructed, and its physiological phenotypes and pathogenicity, as well as transcription profiling, were compared with the parent strain. The ΔrelAΔspoT mutant showed decreased ability to form biofilms, and reduced resistance to acidic, alkaline, high osmolarity and H₂O₂ conditions. The internalization of the ΔrelAΔspoT mutant into host cells in vitro and its lethality and colonization abilities within young chickens were also significantly reduced. RNA sequencing showed that the (p)ppGpp synthetases did not only affect the classic stringent response, such as inhibition of DNA replication and protein synthesis, but also controlled the expression of many virulence factors, in particular, the Salmonella pathogenicity island 1 (SPI-1) and SPI-2 type III secretion systems (T3SSs), and adhesion factors. These results suggest that the (p)ppGpp synthetases are required for the pathogenicity of S. Pullorum by affecting its stress response and the expression of the virulence factors.

沙门氏菌是一种特定于鸟类的病原体，可导致幼鸡发生白癜风病，并导致家禽业的重大经济损失。在传播和感染过程中，S . Pullorum 会遇到各种环境压力和宿主防御。严格反应是由 (p)ppGpp 诱导的重要适应反应，在沙门氏菌中，(p)ppGpp 由两种 (p)ppGpp 合成酶 RelA 和 SpoT 合成。调查中的适应性和致病性（P）合成ppGpp的作用小号。Pullorum，一种 (p)ppGpp 合成酶突变体（Δ relA Δ spoT) 被构建，并将其生理表型和致病性，以及转录谱，与亲本菌株进行比较。Δ relA Δ spoT突变体表现出形成生物膜的能力降低，并且对酸性、碱性、高渗透压和H ₂ O ₂条件的抗性降低。Δ relA Δ spoT突变体在体外内化到宿主细胞中其在幼鸡体内的致死率和定殖能力也显着降低。RNA测序表明，(p)ppGpp合成酶不仅影响经典的严格反应，如抑制DNA复制和蛋白质合成，还控制了许多毒力因子的表达，特别是沙门氏菌致病岛1（SPI- 1) 和 SPI-2 III 型分泌系统 (T3SSs)，以及粘附因子。这些结果表明 (p)ppGpp 合成酶是S的致病性所必需的。Pullorum 通过影响其应激反应和毒力因子的表达。