Plesiomonas shigelloides is an important fish pathogen that causes significant losses in aquaculture. Phage therapy is a new approach to overcome the problem of multidrug-resistant bacteria. Herein, a virulent phage of P. shigelloides was isolated from the intestines of grass carp. This phage belongs to the Siphoviridae family and was designated PSP01. The optimal multiplicity of infection of PSP01 was 1 with a latent period of 30 min and a lytic period of 140 min. Good activity was observed over a wide range of temperatures (-20 °C–50 °C), pH values (3–12), and NaCl concentrations (0.1–3.5%). The phage PSP01 lysis cassette is composed of 3 genes, HolPSP, LysPSP-1 and LysPSP-2. Expression of HolPSP or LysPSP-2 in Escherichia coli resulted in bacterial lysis, and a synergistic effect was observed when the HolPSP and LysPSP-1 proteins were co-expressed. In-frame deletion uncovered an important role of the transmembrane domain (TMD) in HolPSP and the signal peptide (SP) in LysPSP-2 for bacterial lysis function. The protective effects of phage PSP01 were investigated by intraperitoneal injection into grass carp infected with P. shigelloides, showing a 33.3% increase in the survival rate of the infected grass carp. Pathological analysis of the spleens from the infected grass carp revealed alleviation of the pathological symptoms. In conclusion, isolation and bacterial lysis investigations of phage PSP01 provide a new tool for the control of fish pathogens and possesses potential for aquaculture applications.

Plesiomonas shigelloides是一种重要的鱼类病原体，在水产养殖中造成重大损失。噬菌体疗法是​​一种克服多重耐药菌问题的新方法。在此，从草鱼的肠道中分离出一种志贺氏假单胞菌的毒性噬菌体。该噬菌体属于Siphoviridae家族并被命名为 PSP01。PSP01的最佳感染复数为1，潜伏期为30分钟，溶解期为140分钟。在很宽的温度 (-20 °C–50 °C)、pH 值 (3–12) 和 NaCl 浓度 (0.1–3.5%) 范围内观察到良好的活性。噬菌体 PSP01 裂解盒由 3 个基因组成，HolPSP、LysPSP-1和LysPSP-2。HolPSP 或 LysPSP-2 在大肠杆菌导致细菌裂解，当 HolPSP 和 LysPSP-1 蛋白共表达时，观察到协同效应。框内删除揭示了 HolPSP 中的跨膜结构域 (TMD) 和 LysPSP-2 中的信号肽 (SP) 对细菌裂解功能的重要作用。噬菌体 PSP01 的保护作用通过腹腔注射到感染P. shigelloides 的草鱼中进行了研究，显示感染草鱼的存活率增加了 33.3%。对感染草鱼的脾脏进行病理分析，发现病理症状有所缓解。总之，噬菌体 PSP01 的分离和细菌裂解研究为控制鱼类病原体提供了一种新工具，并具有水产养殖应用的潜力。