Complete genomic sequence of bacteriophage phiEcoM-GJ1, a novel phage that has myovirus morphology and a podovirus-like RNA polymerase

Abstract

The complete genome of phiEcoM-GJ1, a lytic phage that attacks porcine enterotoxigenic Escherichia coli of serotype O149:H10:F4, was sequenced and analyzed. The morphology of the phage and the identity of the structural proteins were also determined. The genome consisted of 52,975 bp with a G+C content of 44% and was terminally redundant and circularly permuted. Seventy-five potential open reading frames (ORFs) were identified and annotated, but only 29 possessed homologs. The proteins of five ORFs showed homology with proteins of phages of the family Myoviridae, nine with proteins of phages of the family Podoviridae, and six with proteins of phages of the family Siphoviridae. ORF 1 encoded a T7-like single-subunit RNA polymerase and was preceded by a putative E. coli sigma(70)-like promoter. Nine putative phage promoters were detected throughout the genome. The genome included a tRNA gene of 95 bp that had a putative 18-bp intron. The phage morphology was typical of phages of the family Myoviridae, with an icosahedral head, a neck, and a long contractile tail with tail fibers. The analysis shows that phiEcoM-GJ1 is unique, having the morphology of the Myoviridae, a gene for RNA polymerase, which is characteristic of phages of the T7 group of the Podoviridae, and several genes that encode proteins with homology to proteins of phages of the family Siphoviridae.

FIG. 1.

Electron microscopic appearance of phage φEcoM-GJ1 isolated from pig sewage. The phage has an icosahedral head, a neck, and a long tail. Bar, 50 nm.

FIG. 2.

Digestion of φEcoM-GJ1DNA with EcoRI reveals a fuzzy submolar band (S) probably due to the pac fragment.

FIG. 3.

Gene map for φEcoM-GJ1. Genes are color coded with respect to functionality.

FIG. 4.

SDS-polyacrylamide gel electrophoresis of φEcoM-GJ1. The phage was purified by a glycerol gradient procedure, as repeated attempts at purification with cesium chloride were unsuccessful. The 133-kDa and 35-kDa bands were identified by mass spectrometry as being consistent with the products of genes 62 and 53, respectively. Lane M, molecular weight markers.