Transmembrane glutathione cycling in growing Escherichia coli cells

Glutathione (GSH) plays an important role in bacterial cells, participating in maintenance of redox balance in the cytoplasm and in defense against many toxic compounds and stresses. In this study we demonstrate that in aerobic, exponentially growing Escherichia coli culture endogenous reduced glutathione undergoes continuous transmembrane cycling between the cells and medium. As a result of an establishment of a dynamic balance between GSH efflux and uptake, a constant extracellular concentration of GSH counting per biomass unit is maintained. The magnitude of this concentration strictly depends on external pH. GSH cycling is carried out in respiring cells and disturbed by influences, which change the level of ΔμH+ and ATP. Export of GSH is modified by phosphate deficiency in the medium.