A model of the effects of irradiation on bacterial ability to support phage growth

Abstract

It is pointed out that within a phage-infected bacterium there may be several types of entities which can permit such a cell to produce plaques when plated before infection. From the equation giving the survival of the cell as a plaque-producing entity it is shown that actual survival curves will depend markedly on the relative radiosensitivity of the various entities. Survival curves in the literature are examined and interpreted as relealing the existence of several phage-reproducing factors, in unactivated form, in the cell before infection. The following model is shown to be consistent with all the data examined. After infection, the phage and bacterium undergo modifications lasting about onethird of the latent period. After this time replication begins with the aid of the phage-reproducing factors which are successively activated until all are in production; this takes until the end of the first half of the latent period. After this time the pattern of survival curves depends on the relative radiosensitivity of the phage-reproducing factors and the phages which begin to appear at about two-thirds of the latent period.