[Proton-potassium exchange in Escherichia coli]

Energy-dependent proton--potassium exchange in E. coli is suppressed by both ionophores and the inhibitor of hydrogen pumps N,N'-dichlohexilcarbodimide (DCCD). The ratio of DCCD-sensitive fluxes of H+ and K+ is equal to 2:1 and does not depend upon the values of ionic fluxes, external pH, osmolarity and temperature. Bacteria can absorb synthetic cation tetraphenilphosphonium (TPP+) both in the absence of glucose and at addition of this source of energy. In the presence of glucose TPP+-ions are taken up by cells during the first 5-10 min and then they leave cells. Such glucose--dependent kinetics of TPP+ accumulation coincides with that for the first rapid phase of K+ uptake, but the process is observed, only if the glucose--independent absorption of TPP+ is small. The amount of accumulated TPP+ may be ascribed to the membrane potential of E . coli equalling--180mV. It is therefore considered that electrogenic proton-potassium pump sensitive to external osmolarity operates in E. coli cell membrane and exchanges 2H+ of the cell for 1K+ of external medium.