Transmembrane pH of Clostridium acetobutylicum is inverted (more acidic inside) when the in vivo activity of hydrogenase is decreased

Evidence is reported here that alkalinization of Clostridium acetobutylicum cytoplasm involves hydrogenase activity. A decrease of in vivo hydrogenase activity is accompanied by intracellular accumulation of protons leading to a negative (interior acidic) pH gradient. However, the organism is able to maintain a constant proton motive force by interconverting chemical and electrical potentials.