Energy conservation by a hydrogenase-dependent chemiosmotic mechanism in an ancient metabolic pathway

Significance Acetogenic bacteria are the most primordial living organisms. They can live solely on inorganic compounds by using carbon monoxide or molecular hydrogen as energy sources to fix carbon dioxide to acetate and rely on a chemiosmotic mechanism for energy conservation. Most microorganisms possess a complex respiratory chain that is composed of many different components to establish the chemiosmotic gradient. Here, we dissect the bioenergetics in a chemolithoautotrophic thermophilic acetogenic bacterium. This living fossil uses a simple respiration comprising only a hydrogenase and an ATP synthase for energy conservation. This two-module respiration system is sufficient to sustain primordial microbial life.