Control of membrane potential by external H+ concentration in Bacillus subtilis as determined by an ion-selective electrode.
The membrane potential of intact bacteria was monitored by measuring the tetraphenylphosphonium ion distribution across the membrane using poly--(vinyl chloride) matrix-type electrode selective to tetraphenylphosphonimum ion. It was found that the tetraphenylphosphonium ion was not countertransported against H+ movement. The membrane potential of Bacillus subtilis was estimated to be 80-120 mV inside-negative at external pH 7. The effect of the external pH on the membrane potential was studied. It varied from 30 to 40 mV/decade change in the external [H+] in the pH region of greater than 6.5, increasing pH making it more inside-negative. The addition of carbonyl cyanide m-chlorophenylhydrazone depolarized the membrane, and the membrane potential approached the H+ equilibrium potential. The addition of N,N'-dicyclohexylcarbodiimide did not abolish the pH dependence of the membrane potential. Increasing the external [K+] did not affect the pH dependence. CN- partially depolarized the membrane. A parallel conductance model for membrane potential could explain the results qualitatively.
D001412:Bacillus subtilis / Q000502:physiology*; D001692:Biological Transport / Q000187:drug effects; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology*; D004024:Dicyclohexylcarbodiimide / Q000494:pharmacology; D004566:Electrodes; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008433:Mathematics; D008564:Membrane Potentials / Q000187:drug effects; D009861:Onium Compounds / Q000378:metabolism; D009943:Organophosphorus Compounds
D009861:Onium Compounds; D009943:Organophosphorus Compounds; D004024:Dicyclohexylcarbodiimide; C013289:tetraphenylphosphonium