产志贺毒素多重耐药大肠杆菌噬菌体的生物学特性及全基因组分析

为探明大肠杆菌噬菌体的生物学特性和全基因组特征，本研究以在广西某猪场污水中分离得到的1株产志贺毒素且多重耐药的大肠杆菌GXEC010为宿主菌，同时在污水中分离到1株具有裂解作用的噬菌体，并通过透射电镜观察、最佳感染复数测定、一步生长曲线绘制、热敏感性与酸碱度稳定性评估、杀菌试验及全基因组测序等方法分析该噬菌体的生物学特性与基因组特征。结果表明，分离纯化得到能高效裂解大肠杆菌GXEC010的噬菌体，命名为vB_EcoM_BP10，其噬菌斑呈清晰透明，边缘光滑整齐；该噬菌体的最佳感染复数为1；一步生长曲线结果显示，感染宿主菌潜伏期为5 min，爆发期为65 min，爆发量为51；可耐受温度范围为30~60 ℃，在pH为5~8的环境中能维持稳定性；噬菌体杀菌试验结果显示，感染复数（MOI）为1时噬菌体vB_EcoM_BP10具有良好的杀菌效果。全基因组测序结果表明，噬菌体vB_EcoM_BP10基因组总片段长度为52 288 bp，GC含量为44.16%，含有71个阅读框（ORF）。GO功能注释表明，噬菌体vB_EcoM_BP10可参与小分子代谢、细胞氮化合物代谢等生物学过程中，具备核苷酸转移酶活性、离子结合、DNA结合等分子功能。与Escherichia phage ST32、 Enterobacteria phage phiEcoM-GJ1的亲缘关系较近。综上所述，噬菌体vB_EcoM_BP10具有清晰的宿主受体特异性，良好的热稳定性和酸碱稳定性，本研究结果能为有效防控产志贺毒素多重耐药大肠杆菌奠定一定的理论基础。

A Biological Characteristics and Genome Analysis of Shiga Toxin-producing and Multidrug-resistant Escherichia coli Phages

To explore the biological characteristics and genome characteristics of Escherichia coli phages,in this study,a Shiga toxin-producing multi-drug resistant Escherichia coli strain GXEC010 was isolated from the sewage of a swine farm in Guangxi,and a lytic phage strain was isolated from the sewage,and through the transmission electron microscope,determination of best multiplicity of infection in the plural,one-step growth curve drawing,thermal sensitivity and pH stability evaluation,sterilization experiment and whole genome sequencing methods to analyze the biological characteristics and genome characteristics of the phage.The results showed that the phage which could efficiently lyse Escherichia coli GXEC010 was isolated and purified,and named as vB_EcoM_BP10.The optimal multiplicity of infection this bacterium was 1.The results of one-step growth curve showed that the incubation period of infected host bacteria was 5 min,the outbreak period was 65 min,and the outbreak quantity was 51.The tolerable temperature range was 30 to 60 ℃,and it could be maintained stable in the pH of 5 to 8.The results of bacteriophage bactericidal experiment showed that the bacteriophage vB_EcoM_BP10 had a good bactericidal effect when MOI=1.Completed genome sequencing results showed that the total fragment length of phage vB_EcoM_BP10 was 52 288 bp,GC content was 44.16%,and included 71 ORF.The GO functional notes indicated that phage vB_EcoM_BP10 could participate in small molecule metabolism,cell nitrogen compound metabolism and other biological processes,and had molecular functions such as nucleotide transferase activity,ion binding and DNA binding.This bacterium was closely related to Escherichia phage ST32 and Enterobacteria phage phiEcoM-GJ1.In conclusion,the phage vB_EcoM_BP10 in this study had clear host receptor specificity,good thermal stability and acid-base stability,which could lay a theoretical foundation for the effective prevention and control of Shiga toxin-producing multidrug-resistant Escherichia coli.