On the process of host-controlled modification of bacteriophage

Abstract

The modification of restricted phage T1 (rT1) to the unrestricted form (uT1), and the analogous modification of phage P2 (rP2 to uP2) can be brought about by the presence in the same nonlysogenic host cell, of the vegetative phase of the phage P1. In P1-lysogenic host cells, joint infection with P1 and rT1 increases only slightly the yield of uT1 as compared to infection with rT1 alone. It is postulated that the rare event that causes P1-lysogenic hosts to become yielders when infected with rT1 or rP2, is prophage activation and that a subsequent interaction between vegetative P1 and the restricted phage causes some of the latter to become modified.