Physiological properties of a T7-T3 recombinant bacteriophage that productively infects strains of Escherichia coli that harbor the F plasmid.

The T7-T3 recombinant phage BO2, whose isolation and physical properties are described in the accompanying paper (Molineux et al., J. Virol. 46:881-894, 1983), has been characterized by physiological means after infection of male (F plasmid-containing) and female strains of Escherichia coli. Single-step growth analyses have shown that the hybrid phage gives a burst about two-thirds that of T7 or T3 on females and about one-half that of T3 on males. This reduced burst size can be correlated with altered kinetics of macromolecular synthesis, probably at the level of transcription. The T3 insertions of BO2, designated M1 and M2, that are essential for growth of the hybrid phage on male strains, have been shown to be trans acting and can rescue T7 from F-mediated restriction. The nature of the gene products encoded by the M1 and M2 regions and their role in overcoming the abortive infection of males by T7 are discussed.