Characterization of a novel phage specifically infecting Enterococcus casseliflavus

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.

Key words:Enterococcus casseliflavus;phage;biological characteristics;genomic analysis;comparative genomics;taxonomy