FIG. 4.

ATP content of E. coli M2701 following a potassium downshift or an osmotic upshift. Cells were grown to exponential growth in K20 minimal medium and then transferred to K0 minimal medium (A) or shifted to higher osmolality by the addition of 0.4 M NaCl (B). At time points indicated, intracellular ATP was measured as described in Materials and Methods. As a control, ATP was also measured in control cells that were shifted into medium of the same composition (circles in panel A). Values were normalized to percentages of the initial value and subtracted from each other (panel A, ×). The ATP concentration (mM) was calculated on the basis of the ATP content in nmol/mg dry weight (DW) divided by the cytoplasmic (cyt.) volume in μl/mg dry weight (B).