The linear plasmid prophage Vp58.5 of Vibrio parahaemolyticus is closely related to the integrating phage VHML and constitutes a new incompatibility group of telomere phages.

Vibrio parahaemolyticus O3:K6 pandemic strains recovered in Chile frequently possess a 42-kb plasmid which is the prophage of a myovirus. We studied the prototype phage VP58.5 and show that it does not integrate into the host cell chromosome but replicates as a linear plasmid (Vp58.5) with covalently closed ends (telomeres). The Vp58.5 replicon coexists with other plasmid prophages (N15, PY54, and PhiKO2) in the same cell and thus belongs to a new incompatibility group of telomere phages. We determined the complete nucleotide sequence (42,612 nucleotides) of the VP58.5 phage DNA and compared it with that of the plasmid prophage. The two molecules share the same nucleotide sequence but are 35% circularly permuted to each other. In contrast to the hairpin ends of the plasmid, VP58.5 phage DNA contains 5'-protruding ends. The VP58.5 sequence is 92% identical to the sequence of phage VHML, which was reported to integrate into the host chromosome. However, the gene order and termini of the phage DNAs are different. The VHML genome exhibits the same gene order as does the Vp58.5 plasmid. VHML phage DNA has been reported to contain terminal inverted repeats. This repetitive sequence is similar to the telomere resolution site (telRL) of VP58.5 which, after processing by the phage protelomerase, forms the hairpin ends of the Vp58.5 prophage. It is discussed why these closely related phages may be so different in terms of their genome ends and their lifestyle.