The aerobic to anaerobic transition of E. coli is accompanied with interrelated changes of the adenylate pool, energy charge, respiration rate, as well as the phospholipid content of the cell membranes and the activity of the polyamine synthesizing system. The role of the cellular energy status in the control of the relative content of membrane phospholipids is discussed. The control is based either on energy redistribution in phospholipid metabolism or on the effect on the activity of the polyamine synthesizing system.