Generation of a protonmotive force in anaerobic bacteria by end-product efflux

This chapter deals with the generation of a Protonmotive force in anaerobic bacteria by end-product efflux. The protonmotive force acts as a driving force or regulatory parameter in a large number of different metabolic processes. Until recently only three primary proton pumps have been described in bacteria: (1) membranebound electron transfer chains; (2) the proton-translocating adenosine triphosphatase (ATPase) complex; and (3) in halobacteria, the light-driven proton pump bacteriorhodopsin. A number of experimental approaches can supply information about the generation of metabolic energy by end-product efflux: (1) uptake experiments, to demonstrate carrier activity and to obtain information on the H+/end-product stoichiometry; (2) efflux experiments from preloaded membranes, to demonstrate end-product efflux driven Ap generation (and subsequent ATP synthesis); (3) simultaneous measurements of the end-product gradient and Ap in growing or actively metabolizing cells, to obtain information on the H+/ end-product stoichiometry and possible contributions of energy recycling to the overall production of metabolic energy; and (4) yield experiments under various conditions