The inhibition of bacteriophage DNA injection by dyes bound to the DNA.

A delay ( approximately 10 min) in the appearance of intracellular phage is caused by preincubating the infecting phage T4o(1) in proflavine, acridine orange, or ethidium, but not polyamines. No significant delay in attachment is observed. Apparently the presence of the dye is required inside the permeability barrier of the phage at the time of infection. The effect of proflavine is reduced in the presence of polyamines, suggesting that the active site is on DNA. The phage-host complex is sensitive to shear if the infecting phage have been incubated in proflavine or ethidium, indicating that the completion of DNA injection is delayed. Finally no partially injected complexes could be detected after shearing, which suggests that most of the delay occurs near the beginning of the injection process.