Adenosine 5'-triphosphate formation in Thiobacillus ferrooxidans vesicles by H+ ion gradients comparable to those of environmental conditions.

Vesicles prepared from iron-grown Thiobacillus ferrooxidans, and subsequently loaded with adenosine 5'-diphosphate and inorganic phosphate, produced adenosine 5'-triphosphate when subjected to H+ gradients comparable to those in the cells' normal environment (i.e., an internal pH in the range of 6.0 to 8.0 with an optimum of 7.0 to 7.8 and an external pH in the range of 2.1 to 4.1 with an optimum of 2.8). Nigericin, dicyclohexylcarbodiimide, and pentachlorophenol decreased adenosine 5'-triphosphate synthesis. Valinomycin at concentrations of 2.5 and 5.0 micrograms/ml increased adenosine 5'-triphosphate formation by 25 and 30%, respectively.