Membrane H+ conductance of Streptococcus lactis

Abstract

Membrane conductance to H+ was measured in the anaerobic bacterium S. lactis by a pulse technique employing a low driving force (0.1 pH unit; 6 mV). Over the pH range of 3.7-8.5, a constant value for passive H+ conductance was observed, corresponding to 0.2 .mu.mol of H+/s per pH unit per g, dry wt (1.6 .mu.S/cm2 of surface area). The pH insensitivity of this low basal H+ conductance supports the idea that a circulation of protons can mediate highly efficient energy transductions across the membranes of bacteria.