The first cellular bioenergetic process: primitive generation of a proton-motive force.

It is proposed that the energy-transducing system of the first cellular organism and its precursor was fueled by the oxidation of hydrogen sulfide and ferric sulfide to iron pyrites and two [H+] on the outside surface of a vesicle (the cell membrane), with the concomitant reduction of CO or CO2 on the interior. The resulting proton gradient across the cell membrane provides a proton-motive force, so that a variety of kinds of work can be done. It is envisioned as providing a selective advantage for cells capable of harvesting this potential. The proposed reactants for these reactions are consistent with the predicted composition of the Earth's early environment. Modern-day homologs of the ancestral components of the energy-transducing system are thought to be membrane-associated ferredoxins for the extracellular redox reaction, carbon monoxide dehydrogenase for the carbon fixation reaction, and ATPase for the harvesting of the proton gradient. With a source of consumable energy, the cell could drive chemical reactions and transport events in such a way as to be exploited by Darwinian evolution.