Insertion and replication of the Pseudomonas aeruginosa mutator phage D3112

Summary

D3112 is a temperate bacteriophage of P. aeruginosa with heterogeneous sequences at one extremity of the virion DNA molecule. Infection of strain PAO1 with phage D3112 results in a 40- to 65-fold increase in the frequency of ami mutants resistant to fluoroacetamide. Nine ami::D3112 prophages have been mapped to distinct sites within the ami locus by Southern blotting experiments with a cloned ami ⁺ probe. All prophages have the same restriction map as the D3112 genome extracted from phage particles. The position of D3112 insertions correlates with the phenotype and reversion behavior of the ami mutants. Induction of D3112cts prophages results in amplification of internal prophage segments as discrete restriction fragments before the terminal viral fragments are visible as sharp hybridizing species. This indicates that D3112 replication is accompanied by recombination of prophage termini to numerous sites in the bacterial genome. Chromosomal junction fragments of an ami::D3112cts prophage are maintained through most of the replication cycle but are cleaved shortly before cell lysis, apparently by the viral encapsidation system.