The 283,757 bp dsDNA genome of Pseudomonas fluorescens phage OBP shares a general genomic organization with Pseudomonas aeruginosa phage EL. Comparison of this genomic organization assembled in syntenic genomic blocks interspersed with hyperplastic regions of the ϕKZ-related phages, supports the proposed division in the "EL-like viruses", and the "phiKZ-like viruses" within a larger subfamily. Identification of putative early transcription promoters scattered throughout the hyperplastic regions, explains several features of the ϕKZ-related genome organization (existence of genomic islands) and evolution (multi-inversion in hyperplastic regions). Using Hidden Markov modeling typical conserved core genes could be identified including the portal protein, the injection needle, and two polypeptides with respective similarity to the 3' -5' exonuclease domain and the polymerase domain of the T4 DNA polymerase. While the N-terminal domains of the tail fiber module and peptidoglycan degrading proteins are conserved, the observation of C-terminal catalytic domains typical for the different genera supports the further subdivision of the ϕKZ-related phages.