Rapid degradation of bacteriophage lambda O protein by ClpP/ClpX protease influences the lysis-versus-lysogenization decision of the phage under certain growth conditions of the host cells.

The initiator of bacteriophage lambda DNA replication, the O protein, is rapidly degraded in Escherichia coli by the ClpP/ClpX protease encoded by the host. Although the biochemical mechanism of this degradation has been investigated intensively, a physiological role for this process remained unknown since little effect of dysfunction of clpP and clpX genes on the lytic development of the phage was observed. Here we demonstrate that activities of clpP and clpX genes influence the lysis-versus-lysogenization decision of bacteriophage lambda under certain growth conditions of the host cells. This decision is influenced specifically by ClpP/ClpX-mediated O degradation and resultant inhibition of early lambda DNA replication because mutations in clpP and clpX genes have little effect on stability of other lambda proteins involved in the regulation of the phage developmental switch.