单增李斯特菌前噬菌体的分布及遗传特征分析

Distribution and genetic characterization of Listeria monocytogenes prophages

目的 了解单增李斯特菌基因组中前噬菌体分布状况和基因组特征。方法 自公共数据库GenBank获得275株单增李斯特菌的全基因组序列,运用前噬菌体在线预测软件(PHASTER)对其携带的前噬菌体进行预测。并对预测的完整前噬菌体进行聚类分析、插入位点识别、噬菌体整合酶多态性分析。此外,通过比对耐药基因和毒力基因数据库,搜寻前噬菌体可能携带的耐药基因和毒力基因。结果 本研究发现99.3%的单增李斯特菌基因组含有前噬菌体序列,155株(56.4%)单增李斯特菌基因组预测到229个完整前噬菌体序列。所有完整前噬菌体聚集成4个群,进一步划分为10个簇。前噬菌体分群与其宿主菌所属家系具有较强的相关性,但与宿主菌来源无关。本研究识别到10个前噬菌体插入位点,其中lmot17(tRNAArg),lmot11(tRNASer)和comK是3个最常见的插入位点,lmo1263为新发现的插入位点。相同插入位点前噬菌体所携带整合酶氨基酸序列高度相似。此外,研究发现部分家系Ⅲ菌株和1株家系Ⅰ菌株的噬菌体中携带毒力相关蛋白E编码基因(virE),所有完整前噬菌体中未发现耐药基因。结论 单增李斯特菌普遍携带前噬菌体,超过半数的菌株携带完整前噬菌体,其基因组具有多样性,且在宿主菌染色体中具有多个插入位点。这些插入位点与噬菌体所携带整合酶氨基酸序列密切相关。此外,未发现前噬菌体中携带耐药基因。

Objective This study aims to investigate the distribution and genomic characteristics of the prophages in Listeria monocytogenes.Methods 275 Listeria monocytogenes genomes were selected and used to predict prophages by prophage prediction software(PHASTER).The complete prophages were also subjected to clustering analysis,insertion site identification and prophage integrase polymorphism analysis.In addition,the prophages were searched for possible drug resistance genes and virulence genes carried by comparing the drug resistance gene and virulence gene database.Results In this study,99.3%of Listeria monocytogenes carried prophages,and 155 strains(56.4%)were predicted to have 229 complete prophages,which were divided into 4 groups and 10 clusters.Prophage groups were correlated with strain lineages,but not with strain origins.Ten prophage insertion sites were identified in this study,among which lmot17(tRNAArg),lmot11(tRNASer)and comK were the three most common insertion sites,and lmo1263 was a newly identified insertion site.The amino acid sequences of integrases carried by the prophages in same insertion site had high similarity.In addition,the gene coding for virulence-associated protein E(virE)was found in the prophage of some lineageⅢstrains and one lineageⅠstrain,and no drug resistance gene was found in all intact prophages.Conclusion Listeria monocytogenes commonly carried prophages,more than half of the strains carrying an intact prophage with a diverse genome and multiple insertion sites in the host bacterium chromosome.These insertion sites are associated with integrase amino acid sequences carried by the prophage.In addition,no antibiotic resistance genes were found in prophages in Listeria monocytogenes.