Influence of the phosphate availability on glutathione efflux from Escherichia coli

Addition of phosphate- or sulfate anion into Escherichia coli cultures after prolonged starvation for the source of phosphorus or sulfur led to the resumption of growth and rapid export of glutathione (GSH) to the medium. The level of extracellular GSH (GSH out) was 11-fold and 20-fold higher than the basal value after the addition of phosphate and sulfate, respectively. Addition of sodium arsenate into culture after prolonged starvation for the source of phosphorus caused growth inhibition and irreversible output of glutathione to medium. Using the deletion mutants, it was shown that export of glutathione can be stimulated under input by any of the known phosphate transport systems. It is not revealed a strong correlation between the level of extracellular glutathione and speed of the phosphate input into cells. Export GSH, caused by the addition of phosphate, accompanied by transient elevated in membrane potential, increased production of superoxide anion and demanded the presence of the membrane electrochemical proton gradient (АцЬГ). The above data suggest the following sequence of events after the addition of phosphate to the starving culture of E. coli: the input of phosphate in the cytoplasm - change in membrane potential- superoxide increase in periplasm - stimulation of export of glutathione to the environment. The results suggest the existence of the relation between transmembrane ion fluxes and glutathione cycling.