Topological relationship of prophage lambda to the bacterial chromosome in lysogenic cells.

X irradiation converts bacterial sex factor DNA covalent circles to more slowly sedimenting forms according to first order kinetics. The rate of conversion is greater for sex factors carrying lambda prophage than it is for nonlysogenized sex factors. The magnitude of the difference and the absence of covalent circular DNA from the product show that the prophage DNA is linearly inserted into the sex factor, as predicted by Campbell's model for lysogenization.