Growth-phase-dependent transcriptional regulation of the pcm and surE genes required for stationary-phase survival of Escherichia coli.

Two neighbouring genes, surE and pcm, at 59 min on the Escherichia coli chromosome are both required for stationary-phase survival. Operon fusions of the putative promoter regions in front of surE (P2) or pcm (P3) with the lacZ reporter gene were constructed to study the transcriptional regulation of pcm and surE. Both promoter regions were able to activate beta-galactosidase activity in a growth-phase-dependent way in either rich or minimal medium. Induction from both promoters reached the highest level in late stationary phase and was independent of the rpoS/katF gene. Spent medium from early as well as late stationary-phase cultures could induce the expression of either promoter even after dialysis or boiling. A high cell density could induce the promoters more rapidly but not to a greater extent. It is proposed that the induction might be correlated with the decline in growth rate of the cells. The induction patterns of either P2 or P3 were very similar. pcm can thus be transcribed from both the P2 and P3 promoters that are regulated in similar ways.