Characterization of Op3, a lysis-defective mutant of bacteriophage f2.

We have isolated a conditional lethal mutant of bacteriophage 12 which makes plaques only on E. coli strains carrying a UGA suppressor. It grows normally in nonsuppressing hosts but does not lyse such strains. The mutation complements with amber mutations in each of the three known phage cistrons. These observations lead us to postulate the existence of a fourth gene in the RNA phage.