Systemic method to isolate large bacteriophages for use in biocontrol of a wide-range of pathogenic bacteria.

Large phages are characterized by genomes around 200 kbp or more. They can infect wide host ranges of bacteria and maintain long-lasting infection. There is no standard method for selective isolation of large phages. In this study, we developed a systemic method to isolate large phages and succeeded in isolating 11 large phages, named Escherichia phage E1∼E11. Electron microscopy observations revealed typical Myoviridae phages with big capsids and long contractile tails. Genome sizes of the isolated phages were determined by pulsed-field gel electrophoresis and found to be in two groups, those around 200 kbp for E1, E2, E5, E6, E7, E9 and E10 phages, and others of approximately 450 kbp for E3, E4, E8 and E11 phages. The isolated large phages had wide host ranges: for example, E9 was effective against Shigella sonnei SH05001, Shigella bydii SH00007, Shigella flexneri SH00006, Salmonella enterica serovar Enteritidis SAL01078 and Escherichia coli C3000 (K-12 derivative), as well as its original host E. coli BL21. Screening of these jumbo phages was performed with non-pathogenic E. coli strains as hosts. Therefore, this method opens a way to isolate jumbo phages infecting wide ranges of pathogenic bacteria in a typical laboratory with standard laboratory strains as the hosts. The isolated large phages will be good candidates for biocontrol of various pathogens.

Correction to: Full genome sequence of a polyvalent bacteriophage infecting strains of Shigella, Salmonella, and Escherichia.

The original version of this article unfortunately contained a mistake.

Full genome sequence of a polyvalent bacteriophage infecting strains of Shigella, Salmonella, and Escherichia.

A novel lytic bacteriophage, Escherichia phage EcS1, was isolated from sewage samples collected in Higashi-Hiroshima, Japan. The complete genome sequence of EcS1 was determined using the Illumina Miseq System. The whole genome of EcS1 was found to be 175,437 bp in length with a mean G+C content of 37.8%. A total of 295 genes were identified as structural, functional, and hypothetical genes. BLAST analysis of the EcS1 genomic sequence revealed the highest identity (79%; query cover of 73-74%) to three T4-related phages that infect Serratia sp. ATCC 39006. Host range experiments revealed that EcS1 has lytic effects on three pathogenic strains of Shigella spp. and a pathogenic strain of Salmonella enterica as well as on E. coli strains. However, two strains of Serratia marcescens showed resistance to this phage. Phylogenetic trees for phage tail fiber protein sequences revealed that EcS1 is closely related to Enterobacteriaceae-infecting phages. Thus, EcS1 is a novel phage that infects several pathogenic strains of the family Enterobacteriaceae.