'Restoration' of Escherichia coli strain B After Irradiation: its Dependence on Suboptimal Growth Conditions

SUMMARY: After irradiation of Escherichia coli strain B by ultraviolet or ionizing radiations, different plating media give rise to widely different viable counts; the surviving fractions are smallest on media which are optimal for the growth of unirradiated organisms. It is concluded that inhibition of colony formation after irradiation is due in part to an injury which leads to imbalance in the synthetic processes of the cell, so that ‘recovery’ or ‘restoration’ may be brought about by suboptimal conditions of growth. The proportion of cell deaths which may be ascribed to this particular injury is determined by the conditions obtaining in bacterial suspensions before and during irradiation, and also by the type of radiation used.