Chemiosmotic H + cycling across the plasma membrane of the thermoacidophilic archaebacterium Sulfolobus acidocaldarius

Abstract

Transitory H + ejection from Sulfolobus acidocaldarius cells induced by oxygen pulses, and anaerobic H + backflow were investigated. Aerobic proton extrusion is inhibited by protonophores, by nigericin and by inhibitors of respiratory electron transport; it is stimulated by DCCD. In contrast, DCCD inhibits the rate of anaerobic H + backflow. Aerobic proton extrusion is significantly enhanced by K +/valinomycin. Apparent H +/O ratios of 2.5–3 are measured. Proton extrusion generates large pH gradients (3–4 units) representing the major contribution to the total proton motive force across the plasma membrane of this thermoacidophilic archaebacterium.