The genome of VP3, a T7-like phage used for the typing of Vibrio cholerae.

The bacteriophage VP3 is used in a phage-biotyping scheme as one of the typing phages of Vibrio cholerae O1 biotype El Tor strains. Here, we have sequenced and analyzed its genome. The genome consists of 39,481 bp with an overall G + C content of 42.6 %. Fifty-two open reading frames (ORFs) were predicted. Within the genome, 17 highly conserved phage promoters and 6 rho-independent terminators were predicted. When assessed with Rluc as a reporter gene, 12 of 16 cloned VP3 promoters showed activity in the host strain V. cholerae biotype El Tor. Based on the temporal expression pattern detected using reverse transcription PCR (RT-PCR), VP3 ORFs can be classed into four groups, arranged according to their order in the VP3 genome. Terminators T1 and T6 are presumed to work efficiently. Sequencing of the typing phage VP3 of V. cholerae reveals its evolutionary subdivisions from the members of T7-like phages of Escherichia coli. Knowledge of VP3 expands the known host range of T7-like phages and will promote understanding the different infection mechanisms used by members of this genus.