Complete Genome of the Broad-Host-Range Erwinia amylovora Phage ΦEa21-4 and Its Relationship to Salmonella Phage Felix O1

Abstract

The first complete genome sequence for a myoviridal bacteriophage, ΦEa21-4, infecting Erwinia amylovora, Erwinia pyrifoliae , and Pantoea agglomerans strains has been determined. The unique sequence of this terminally redundant, circularly permuted genome is 84,576 bp. The ΦEa21-4 genome has a GC content of 43.8% and contains 117 putative protein-coding genes and 26 tRNA genes. ΦEa21-4 is the first phage in which a precisely conserved rho-independent terminator has been found dispersed throughout the genome, with 24 copies in all. Also notable in the ΦEa21-4 genome are the presence of tRNAs with six- and nine-base anticodon loops, the absence of a small packaging terminase subunit, and the presence of nadV , a principle component of the NAD ⁺ salvage pathway, which has been found in only a few phage genomes to date. ΦEa21-4 is the first reported Felix O1-like phage genome; 56% of the predicted ΦEa21-4 proteins share homology with those of the Salmonella phage. Apart from this similarity to Felix O1, the ΦEa21-4 genome appears to be substantially different, both globally and locally, from previously reported sequences. A total of 43 of the 117 genes are unique to ΦEa21-4, and 32 of the Felix O1-like genes do not appear in any phage genome sequences other than ΦEa21-4 and Felix O1. N-terminal sequencing and matrix-assisted laser desorption ionization-time of flight analysis resulted in the identification of five ΦEa21-4 genes coding for virion structural proteins, including the major capsid protein.