The kinetics of the chemiosmotic proton circuit of the iron-oxidizing bacterium Thiobacillus ferrooxidans

The kinetics of the coupling of the redox reactions and oxidative phosphorylation in Thiobacillus ferrooxidans is analyzed by the methods of electrochemical kinetics. The chemiosmotic circuit operates in a manner analogous to the circuit of a fuel cell or a battery: anodic and cathodic reactions are connected in one half of the circuit by the electron-transport chain, and in the other half of the circuit by the solution and the adenosine triphosphate (ATP) synthase. It is shown that this model predicts that the rate of oxidation of ferrous ions at low concentrations is half order in the concentration of ferrous ions, and at high concentrations it is zero order. This electrochemical hypothesis is supported by the experimental results, including both the bioenergetic parameters and the measurement of the rate of bacterial growth. (C) 1997 Elsevier Science S.A.