The role of putrescine and the cellular energy state of Escherichia coli in regulation of DNA topology during adaptation to oxidative stress

An exponential-phase culture of E. coli responded to the addition of H2O2 b y a decrease in DNA supercoiling induced by the lowering of the energy stat us of cells, potassium leakage, and breaking of polynucleotide chains. Exte nding the time of exposure of E. coli cells to hydrogen peroxide led to an increase in the intracellular pools of putrescine and potassium, promotion of cellular energy status, and the restoration of DNA supercoiling to value s much in excess of the prestress level. The subsequent stabilization of th e intracellular putrescine pool was accompanied by a release of this polyam ine from the cell. Based on these results and those available in the litera ture, a mechanism of E. coli adaptation to oxidative stress is suggested th at assigns roles to putrescine, potassium, and cellular energy status.