Expression of gene 1.2 and gene 10 of bacteriophage T7 is lethal to F plasmid-containing Escherichia coli.

Plasmids expressing bacteriophage T7 gene 1.2 or gene 10 DNA transform F plasmid-containing strains of Escherichia coli only at low efficiency, though they transform plasmid-free strains normally. The gene products T7 gp1.2 and T7 gp10 appear to be the toxic agents, and their effects are directed towards the product of the F pifA gene, PifA. T7 gp1.2 and gp10 are also the two targets of the pif exclusion system of F, and their synthesis normally triggers the abortive infection of T7 in pifA+ hosts. The properties of plasmids containing T7 gene 1.2 or 10 suggest that they can be used to study the molecular mechanisms of phage exclusion in model systems that avoid the pleiotropic dysfunctions associated with an abortive infection.