Kalindamar Safak, Abdelhamed Hossam, Kordon Adef O, Pinchuk Lesya M, Karsi Attila
Department of Molecular Biology and Genetics, Faculty of Arts and Sciences, Ordu University, Ordu, Turkey.
Department of Comparative Biomedical Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, MS, United States.
Front Vet Sci. 2021 Jun 2;8:681609. doi: 10.3389/fvets.2021.681609. eCollection 2021.
is a Gram-negative facultative intracellular pathogen causing enteric septicemia of catfish (ESC), a devastating disease resulting in significant economic losses in the U.S. catfish industry. Bacterial secretion systems are involved in many bacteria's virulence, and Type VI Secretion System (T6SS) is a critical apparatus utilized by several pathogenic Gram-negative bacteria. strain 93-146 genome has a complete T6SS operon with 16 genes, but the roles of these genes are still not explored. In this research, we aimed to understand the roles of two hemolysin co-regulated family proteins, Hcp1 (EvpC) and Hcp2. To achieve this goal, single and double mutants (ΔΔ, and ΔΔ) were generated and characterized. Catfish peritoneal macrophages were able to kill Δ better than ΔΔΔ, and wild-type (WT). The attachment of Δ and ΔΔ to ovary cells significantly decreased compared to WT whereas the cell invasion rates of these mutants were the same as that of WT. Mutants exposed to normal catfish serum showed serum resistance. The fish challenges demonstrated that Δ and ΔΔ were attenuated completely and provided excellent protection against WT infection in catfish fingerlings. Interestingly, Δ caused higher mortality than that of WT in catfish fingerlings, and severe clinical signs were observed. Although fry were more susceptible to vaccination with Δ and ΔΔ, their attenuation and protection were significantly higher compared to WT and sham groups, respectively. Taken together, our data indicated that () is involved in virulence in catfish while is involved in adhesion to epithelial cells and survival inside catfish macrophages.
是一种革兰氏阴性兼性细胞内病原体，可引起鲶鱼肠败血症（ESC），这是一种毁灭性疾病，给美国鲶鱼产业造成重大经济损失。细菌分泌系统与许多细菌的毒力有关，VI型分泌系统（T6SS）是几种致病性革兰氏阴性细菌使用的关键装置。93 - 146菌株基因组有一个完整的T6SS操纵子，包含16个基因，但这些基因的作用仍未被探索。在本研究中，我们旨在了解两种溶血素共调节家族蛋白Hcp1（EvpC）和Hcp2的作用。为实现这一目标，构建并鉴定了单突变体和双突变体（ΔΔ、ΔΔ）。鲶鱼腹膜巨噬细胞对Δ的杀伤能力比对ΔΔΔ和野生型（WT）更强。与WT相比，Δ和ΔΔ对卵巢细胞的附着显著减少，而这些突变体的细胞侵袭率与WT相同。暴露于正常鲶鱼血清的突变体表现出血清抗性。鱼类攻毒试验表明，Δ和ΔΔ完全减毒，并为鲶鱼苗种提供了对WT感染的良好保护。有趣的是，Δ在鲶鱼苗种中导致的死亡率高于WT，并观察到严重的临床症状。虽然鱼苗对用Δ和ΔΔ进行疫苗接种更敏感，但它们的减毒和保护作用分别比WT和假手术组显著更高。综上所述，我们的数据表明（）参与鲶鱼的毒力，而参与对上皮细胞的粘附和在鲶鱼巨噬细胞内的存活。
