| Abstract: | It was shown that the proton conductivity of Enterococcus hirae ATCC9790 membrane increases three times as pH of the growth medium decreases from 8.5 to 5.5. The changes in proton conductivity are interrelated to the values of membrane and redox potentials of the cell, which in turn vary depending on the pH value of growth medium. The energy-dependent H+ efflux for cells fermenting sugar (the glucose) decreases 1.5 times as pH decreases from 8.5 to 5.5; in this case, the N,N'-dicyclohexylcarbodiimide at lower pH values suppresses the H+ efflux more intensively than at higher pH values, the H+ efflux nonsensitive to N,N'-dicyclohexylcarbodiimide being practically unchanged. The H+ efflux in the ATPase mutant MS116 is significantly (approximately 3 times) lower than that in the precursor strain and does not depend on pH. The results show that the proton conductivity of the membrane of this bacterium depends on pH of the growth medium. It is possible that the energy-dependent H+ efflux through F1F0-ATPase is interrelated with membrane proton conductivity. |
