金黄色葡萄球菌噬菌体vB_SauH_IME522的分离鉴定及全基因组分析

Isolation and complete genome analysis of Staphylococcus aureus bacteriophage vB_SauH_IME522

目的从医院污水中分离到一株金黄色葡萄球菌噬菌体vB_SauH_IME522,对其进行分离鉴定、测序及进化和基因组学的分析。方法以一株从临床分离到的多重耐药的金黄色葡萄球菌为宿主菌分离噬菌体,应用双层琼脂平板法进行噬菌体最佳感染复数(optimal MOI)、一步生长曲线(one-step growth curve)实验,使用蔗糖密度梯度离心纯化病毒,并通过透射电镜观察噬菌体形态;应用SDS/蛋白酶裂解方案提取噬菌体全基因组,使用Illumina Miseq测序平台进行噬菌体全基因组测序,测序后对噬菌体全基因组序列进行组装、注释、进化和比较基因组学分析。结果分离到一株金黄色葡萄球菌噬菌体,命名为vB_SauH_IME522;其最佳感染复数为0.01,一步生长曲线结果显示,其感染宿主菌的潜伏期约为20 min,裂解期约为200 min,平均裂解量89 PFU/cell;电镜观察该噬菌体,噬菌体vB_SauH_IME522具有典型的二十面体结构和收缩的尾部,其头部直径为(70±1)nm,尾部长度为(135±2)nm。基因组测序结果表明,噬菌体基因组全长为140 246 bp,G+C含量为30.2%。基因组注释显示噬菌体vB_SauH_IME522含有223个蛋白编码基因、164个启动子、66个终止子、4个tRNAs及7个耐药相关位点。其中52个基因的编码产物有预测的功能,其余基因的编码产物均为功能未知的推定蛋白。系统发生分析表明,该噬菌体属于Twortvirinae亚科的Kayvirus属。结论烈性噬菌体vB_SauH_IME522为Twortvirinae亚科的新成员,具有较强的裂解能力和短的潜伏期。

Objective To isolate, sequence, and identify biological characterization and complete genome sequencing of a virulent Staphylococcus aureus(S. aureus) bacteriophage vB_SauH_IME522. Methods A phage was isolated from sewage of PLA Chinese General Hospital using a clinically isolated S. aureus strain as host bacteria. The double-layer agar plate was used to determine the optimal multiplicity of infection(optimal MOI) and one-step growth curve. Phage morphology was observed by transmission electron microscopy after purification using sucrose gradient separation. Phage DNA was sequenced using the Illumina Miseq sequencing platform. The complete genome sequence was annotated, then comparative genomics and evolutionary analyses were performed. Results A lytic phage of S. aureus was isolated from hospital sewage and named as vB_SauH_IME522. The optimal MOI of the phage was 0.01. One step growth curve showed that its latent period and burst period were 20 and 200 min, respectively. The burst size was about 89 PFU/cell. Electron microscopy displayed the phage having an icosahedral head(70±1) nm and a long contractile tail(135±2) nm. Genome sequencing results showed that the total length of the phage genome was 140 246 bp and the G+C content accounted for 30.2%. The genomic annotation revealed that the phage contained 223 genes coding proteins, 164 putative promoters, 66 terminators, 4 tRNAs, and 7 resistance-related regions. Phylogenetic analysis suggested that the phage was a member of the genus Kayvirus within the subfamily Twortvirinae. Conclusion A lytic phage of S. aureus vB_SauH_IME522 is identified as a new member of the Twortvirinae subfamily, with strong lytic ability and short latent period.