Proton translocation associated with nitrite respiration in Desulfovibrio desulfuricans

Proton translocation by Desulfovibrio desulfuricans cells, cultured anaerobically with nitrate as terminal oxidant, was studied by the oxidant-pulse method. Nitrate-grown D. desulfuricans translocated protons rapidly and reproducibly with hydrogen as reductant and nitrite as electron acceptor. H+/2e- ratios were typically in the range 1.8-2.2. Proton translocation following pulses of nitrite was also observed with endogenous substrate in freshly harvested cells and with lactate or formate as electron donors in starved cells. Problems in the determination of H+/2e- ratios when endogenous substrate, formate, or lactate was the electron donor are discussed. Evidence is presented for the location of formate dehydrogenase, hydrogenase, and nitrite reductase on the periplasmic and for lactate dehydrogenase on the cytoplasmic side of the cytoplasmic membrane.