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.

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.