GROWTH PHASE-DEPENDENT MODIFICATION OF RNA-POLYMERASE IN ESCHERICHIA-COLI

During the transition of Escherichia coli cultures from exponential growth to stationary phase, the pre-existing RNA polymerase was found to be converted into at least three different holoenzyme forms, which could be separated by phosphocellulose column chromatography. The relative levels of these three holoenzyme forms changed depending on the phase of cell growth. The altered stationary phase forms of RNA polymerase showed promoter recognition properties that were different from those of the holoenzyme from exponentially growing cells. Enzyme reconstitution experiments showed that the altered promoter selectivity was due to modification of the core enzyme. We propose that modulation of RNA polymerase plays a role in the global switch of gene expression during the transition from exponential growth to stationary phase.