Analysis Of Complete Genome Of A Lytic Bacteriophage Ec-ZZ2 Infecting Enterococcus Faecium

Enterococcus faecium,a member of Genus Enterococcus,is gram-positive bacterium that is found in the intestinal tract of humans and animals,and it may inhabit natural environment.Enterococci(E.faecium and E.faecalis)are regarded as one of opportunistic pathogens that cause nosocomial infections.Individuals with compromised immune systems,such as cancer patients undergoing chemotherapy,transplant recipients,traumatized patients,and the elderly in general,are particularly prone to develop Enterococcus infections.Infection caused by antibiotic-resistant Enterococci is a real challenge in public health.Moreover,the emergence of vancomycin-resistant Enterococci(VRE)has become a threat against global health.Recently,bacteriophages have been suggested as the promising alternative therapeutic agents against bacterial infections.In the current study,we have isolated and characterized a lytic phage of Enterococcus faecium.We then undertook genetic analysis of a newly isolated bacteriophage infecting Enterococcus faecium.This investigation may provided experimental evidence to validate the application of phage against Enterococcus infections.A lytic phage infecting Enterococcus faecium isolates was isolated from sewages using standard protocol,designated Ec-ZZ2.Transmission electron microscopy analysis revealed that Ec-ZZ2 had a isometric head and a non-contractile tail.The diameter of the head was about 50 nm and the tail length was 180 nm.According the morphological characteristics,Ec-ZZ2 was classified as belonging to the order Caudoviradles,family Siphoviridae.The complete genome sequence was determined by Illumina Hi Seq 2000 at Shenzhen Hua Da gene science and Technology Service Co.,Ltd(Shenzhen,China).The results showed that Phage Ec-ZZ2 contained a linear double-stranded DNA with a size of 41,170 bp and a G+C content of 34.59%.It has 59 predicted coding sequences(CDS),five Tandem repeats,and two Minisatellite DNAs.No t RNA genes were identified.Of the 59 predicted coding sequences,30 are hypothetical novel or conserved genes,and 29 were given a putative function.This genome contains phage structural genes(major capsid protein,major tail protein,head-tail joining protein and tail fiber protein),nonstructural genes(DNA polymerase,DNA helicase,DNA primase,and HNH endonuclease).Genes encoding functional proteins related to host lysis include holin and lysin that participate in destroying the peptidoglycan of host cells.The analysis of the complete sequence revealed that phage Ec-ZZ2 shows high homology to genomes of the previously reported Enterococcus phage IME-EF4(97% identity,Gen Bank accession no.KF733017.1),Enterococcus phage EF3(91% identity,Gen Bank accession no.KF728385.2),Enterococcus phage Efa CPTC(92% identity,Gen Bank accession no.JX193904.1)and Enterococcus phage AUEF3(96% identity,Gen Bank accession no.KJ127304.1),according to the results from the BLASTN program.The whole-genome sequence of phage Ec-ZZ2 was deposited in Gen Bank under accession no.KR131750.