Evidence that bacteriophage λ lysogens may induce in response to the proton motive force uncoupler CCCP.

We describe a genetic β-galactoside reporter system using a disk diffusion assay on MacConkey Lactose agar petri plates to monitor maintenance of the bacteriophage λ prophage state and viral induction in Escherichia coli K-12. Evidence is presented that the phage λ major lytic promoters, pL and pR, are activated when cells containing the reporters are exposed to the energy poison carbonyl cyanide m-chlorophenyl hydrazine, CCCP. This uncoupler of oxidative phosphorylation inhibits ATP synthesis by collapsing the proton motive force. Expression of the λ lytic promoters in response to CCCP requires host RecA function and an autocleavable CI repressor, as does SOS induction of the λ prophage that occurs by a DNA damage-dependent pathway. λ Cro function is required for CCCP-mediated activation of the λ lytic promoters. CCCP does not induce an sfi-lacZ SOS reporter. Published by Oxford University Press on behalf of FEMS 2015. This work is written by (a) US Government employee(s) and is in the public domain in the US.