First Evidence for Existence of an Uphill Electron Transfer through the bc 1 and NADH-Q Oxidoreductase Complexes of the Acidophilic Obligate Chemolithotrophic Ferrous Ion-Oxidizing Bacterium Thiobacillus ferrooxidans

Abstract

ABSTRACT The energy-dependent electron transfer pathway involved in the reduction of pyridine nucleotides which is required for CO 2 fixation to occur in the acidophilic chemolithotrophic organism Thiobacillus ferrooxidans was investigated using ferrocytochrome c as the electron donor. The experimental results show that this uphill pathway involves a bc 1 and an NADH-Q oxidoreductase complex functioning in reverse, using an electrochemical proton gradient generated by ATP hydrolysis. Based on these results, a model is presented to explain the balance of the reducing equivalent from ferrocytochrome c between the exergonic and endergonic electron transfer pathways.