Conversion of lambda defective lysogens from the non-immune state to the immune state

Summary Escherichia coli cells lysogenic for a lambda prophage defective in the N and x region continually synthesize the (reversibly) thermolabile repressor at the non-permissive temperature, at which the cells are non-immune. The conversion of such an imm^- culture to the immune state can proceed in the absence of RNA or protein synthesis. However, it appears that more repressor molecules are present in cells grown at the permissive temperature. Our results do not support the flip-flop model for the regulation of repressor synthesis.