一株铅黄肠球菌噬菌体的生物学特性和全基因组分析

Characterization of a novel phage specifically infecting Enterococcus casseliflavus

摘要:

【目的】铅黄肠球菌是医源感染的机会致病菌，可引起危及生命的败血症、脑膜炎等，但针对其噬菌体的研究尚属空白。噬菌体作为细菌病毒，具有宿主特异性。本研究首次分离到可培养的铅黄肠球菌烈性噬菌体，对其基因组序列的分析和其他特征研究为进一步探讨噬菌体与宿主的作用机制及治疗应用提供参考。【方法】噬菌体Ecf_virus_SZ01以健康人粪便中分离的铅黄肠球菌(DO55)作为宿主菌，分离自深圳市南山区未经处理的生活污水样本，利用透射电镜观察噬菌体形态并对其生物学特征和基因组特点进行研究。【结果】透射电镜显示，噬菌体Ecf_virus_SZ01头部直径约为106 nm，尾部直径约为150 nm，尾长且无伸缩性尾鞘，属长尾噬菌体科；该噬菌体的最佳感染复数为0.01；一步生长曲线显示，潜伏期约为30 min，每个受感染细胞产生子代的平均数量为50 PFU/cell；抑菌曲线显示MOI=0.01时对宿主菌具有很好的抑制效果；宿主特异性强，不能实现跨属侵染；测序结果显示其基因组为dsDNA，长度为59 409 bp，GC含量为43.2%；该噬菌体共有102个开放阅读框，BLASTn比对显示该噬菌体与NCBI数据库中其他噬菌体相似性极低。【结论】首次分离到宿主为铅黄肠球菌的噬菌体，具有潜伏期短、裂解能力强、宿主专一的特征，基因组与数据库中现有噬菌体相比十分新颖，并对其生物学特性和基因组进行了分析。

Abstract:

Abstract: [Objective] Enterococcus casseliflavus,an opportunistic pathogen,could cause life-threatening sepsis and meningitis.Up to now,little has been known about the phage specifically infecting E.casseliflavus.The isolation,genomic analysis,and characterization of the E.casseliflavus phage can provide a reference for exploring the mechanism of interaction between phage and host and further applying the phage in therapy.[Methods] The phage Ecf_virus_SZ01 was isolated from untreated domestic sewage in Nanshan district,Shenzhen.We employed transmission electron microscopy (TEM) to observe the morphology of Ecf_virus_SZ01 and then studied its biological and genomic characteristics.[Results] Ecf_virus_SZ01 had a non-contractile tail with the length of 150 nm and a head with the diameter of 106 nm,belonging to the Siphoviridae family.The optimal multiplicity of infection (MOI) of the phage was 0.01.The one-step growth curve showed that the phage had an incubation period of about 30 min and the burst size of 50 PFU/cell.Ecf_virus_SZ01 inhibited the growth of host bacteria.Furthermore,the genome of Ecf_virus_SZ01 was 59 409 bp in length,which had the GC content of 43.2% and 102 open reading frames.Blastn comparison showed that this phage had low sequence similarity with other phages deposited in the NCBI database.[Conclusion] In this study,for the first time,we reported a phage that could specifically infect and lyse E.casseliflavus.Both the genomic and phylogenetic analyses indicated the novelty of this phage.