Cyanophage Pf-WMP4, a T7-like phage infecting the freshwater cyanobacterium Phormidium foveolarum: complete genome sequence and DNA translocation.

We report the complete 40,938-bp genome sequence of a cyanophage, Pf-WMP4, which infects the freshwater cyanobacterium Phormidium foveolarum Gom. Nine of the forty-five potential open reading frames in the Pf-WMP4 genome share similarities with the genes found in T7-like phages. Using in vitro transcription, we found that seven promoters at the leftmost end of the genome can be recognized by the host RNA polymerase. By blocking transcriptional and translational inhibitors, we found that Pf-WMP4 DNA translocation, with an average translocation rate of 19.8+/-2.7 bp s(-1) at 28 degrees C, requires both host transcription and protein synthesis of an unknown factor. Therefore the mechanism of cyanophage Pf-WMP4 DNA injection may be driven both by a T7-like internalization mechanism as well as an additional unknown mechanism requiring de novo protein synthesis. Our analysis of the Pf-WMP4 genome sheds new light on the translocation strategies and evolutionary traces of phages belonging to the T7 supergroup.