Isolation and complete genome analysis of Staphylococcus aureus bacteriophage vB_SauH_IME522

Abstract

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.

Keywords

• staphylococcus aureus
• bacteriophage
• biological characteristics
• genomic analysis