A selenium-activated protein P catalyses a metabolic reaction that results in release of two H ⁺ ions. Expression of P is induced by lactose. In an experiment, cells were grown for 1 hour in selenium and lactose containing media resulting in a net concentration of 10^6 M H ⁺ per cell. Selenium and lactose were removed from the media and cells were grown for another 10 generations. Assuming that all other proteins are