Zhao Tong, Yang Bintong, Li Hongjin, Qian Aidong, Cong Wei, Sun Wuwen, Kang Yuanhuan
College of Veterinary Medicine/College of Animal Science and Technology, Jilin Agricultural University, Changchun, China.
Marine College, Shandong University, Weihai, China.
J Fish Dis. 2022 Oct;45(10):1477-1489. doi: 10.1111/jfd.13676. Epub 2022 Jun 24.
Aeromonas veronii is a significant pathogen that is capable of infecting humans, animals, and aquatic animals. The type III secretion system (T3SS) is intimately associated with bacterial pathogenicity. The ascO gene is an important core component of T3SS in A. veronii, but its function is still unclear. The ascO gene of A. veronii TH0426 was deleted by using the pRE112 suicide plasmid to study its function. The study results showed that the ability of ∆ascO to adhere and invade EPC cells was significantly reduced by 1.28 times. The toxicity of the mutant strain ΔascO to EPC cells was consistently significantly lower than wild-type strain TH0426 at 1, 2, and 4 h. The LD50 values of ∆ascO against zebrafish and Carassius auratus (C. auratus) were 53 and 15 times that of the wild-type strain. In addition, the bacterial load of the mutant strain ΔascO in blood, heart, liver, and spleen was lower than wild-type strain TH0426. The Hoechst staining showed that the apoptotic degree of EPC cells induced by the mutant strain ΔascO was lower than that of the wild-type strain TH0426. Furthermore, real-time quantitative PCR (RT-qPCR) analysis revealed lower expression levels of pro-apoptotic genes (including cytC, cas3, cas9, TNF-α, and IL-1β) in C. auratus tissues infected with the mutant strain ΔascO compared to the wild-type strain TH0426. The results of in vivo and in vitro experiments have shown that ascO gene mutation can reduce the adhesion and toxicity of A. veronii to EPC and reduce the level of apoptosis induced by A. veronii. As a result, these insights will help further elucidate the function of the ascO gene and thus contribute to understanding the pathogenesis of A. veronii.
维氏气单胞菌是一种重要的病原体，能够感染人类、动物和水生动物。III型分泌系统（T3SS）与细菌致病性密切相关。ascO基因是维氏气单胞菌T3SS的一个重要核心组成部分，但其功能仍不清楚。利用pRE112自杀质粒缺失维氏气单胞菌TH0426的ascO基因以研究其功能。研究结果表明，ΔascO黏附并侵袭EPC细胞的能力显著降低了1.28倍。在1、2和4小时时，突变株ΔascO对EPC细胞的毒性始终显著低于野生型菌株TH0426。ΔascO对斑马鱼和鲫鱼的半数致死剂量（LD50）值分别是野生型菌株的53倍和15倍。此外，突变株ΔascO在血液、心脏、肝脏和脾脏中的细菌载量低于野生型菌株TH0426。Hoechst染色显示，突变株ΔascO诱导的EPC细胞凋亡程度低于野生型菌株TH0426。此外，实时定量PCR（RT-qPCR）分析显示，与野生型菌株TH0426相比，感染突变株ΔascO的鲫鱼组织中促凋亡基因（包括cytC、cas3、cas9、TNF-α和IL-1β）的表达水平较低。体内和体外实验结果表明，ascO基因突变可降低维氏气单胞菌对EPC的黏附性和毒性，并降低维氏气单胞菌诱导的凋亡水平。因此，这些见解将有助于进一步阐明ascO基因的功能，从而有助于理解维氏气单胞菌的发病机制。
