TY - JOUR T1 - The P-SSP7 Cyanophage Has a Linear Genome with Direct Terminal Repeats A1 - Sabehi, Gazalah A1 - Lindell, Debbie Y1 - 2012/05/11 N2 - P-SSP7 is a T7-like phage that infects the cyanobacterium Prochlorococcus MED4. MED4 is a member of the high-light-adapted Prochlorococcus ecotypes that are abundant in the surface oceans and contribute significantly to primary production. P-SSP7 has become a model system for the investigation of T7-like phages that infect Prochlorococcus. It was classified as T7-like based on genome content and organization. However, because its genome assembled as a circular molecule, it was thought to be circularly permuted and to lack the direct terminal repeats found in other T7-like phages. Here we sequenced the ends of the P-SSP7 genome and found that the genome map is linear and contains a 206 bp repeat at both genome ends. Furthermore, we found that a 728 bp region of the genome originally placed downstream of the last ORF is actually located upstream of the first ORF on the genome map. These findings suggest that P-SSP7 is likely to use the direct terminal repeats for genome replication and packaging in a similar manner to other T7-like phages. Moreover, these results highlight the importance of experimentally verifying the ends of phage genomes, and will facilitate the use of P-SSP7 as a model for the correct assembly and end determination of the many T7-like phages isolated from the marine environment that are currently being sequenced. JF - PLOS ONE JA - PLOS ONE VL - 7 IS - 5 UR - https://doi.org/10.1371/journal.pone.0036710 SP - e36710 EP - PB - Public Library of Science M3 - doi:10.1371/journal.pone.0036710 ER -