A bacteriophage T4 mutant defective in protection against superinfecting phage.

Abstract

When Escherichia coli is infected by bacteriophage T4 and after a few minutes superinfected by additional phage, the secondary phage genome is prevented from being expressed and from contributing genetic information to progeny phage. This phenomenon, known as superinfection inhibition, was first observed by Dulbecco (1952). Further work was carried out by Graham (1953) and has been reviewed by Adams (1959) and Campbell (1967). Several questions have arisen concerning the mechanism of this phenomenon. Is the DNA of the superinfecting phage broken down by the DNases present in the cell, and is this DNA degradation essential for the inhibition? Is there a barrier at the membrane level which prevents the superinfecting DNA from getting into the cell? Does superinfection inhibition depend on the expression of a function or functions by the primary phage which exclude the superinfecting phage? Graham (1953) using high streptomycin concentrations to inhibit nuclease action observed that superinfecting phage were nevertheless excluded.