Energetics of glucose uptake in Salmonella typhimurium.

We have studied the energetics of glucose uptake in Salmonella typhimurium. Strain PP418 transports glucose via the phosphoenolpyruvate: glucose phosphotransferase system, while strain PP1705 lacks this system and can only use the galactose permease for glucose uptake. These two strains were cultured anaerobically in glucose-limited chemostats. Both strains produced ethanol and acetate in equimolar amounts but a significant difference was observed in the molar growth yield on glucose (YGlc). It is suggested that this difference is due to a difference in the energetics of the glucose uptake systems in the two strains. Assuming an equal YATP for both strains, we could calculate that uptake of 1 mole of glucose via the galactose permease consumes the equivalent of 0.5 mole of ATP. With the additional assumption that one proton is transported in symport with one glucose molecule, these results imply a stoichiometry of two protons per ATP hydrolysed.