NISIN DISSIPATES THE PROTON MOTIVE FORCE OF THE OBLIGATE ANAEROBE CLOSTRIDIUM-SPOROGENES PA-3679

The influence of nisin on the proton motive force (DELTA-p) generated by glucose-energized cells of the obligate putrefactive anaerobe Clostridium sporogenes PA 3679 was determined. The components of DELTA-p, the transmembrane potential (DELTA-psi) and the pH gradient (DELTA-pH), were determined from the distributions of the lipophilic cation [H-3]RPP+ ([H-3]tetraphenylphosphonium bromide) and [C-14]salicylic acid, respectively. The cells maintained a constant DELTA-p of -111 mV, consisting of a DELTA-pH of 0.4 to 1.0 pH units at an external pH of 5 to 7 and a DELTA-psi of -60 to -88 mV. Nisin, carbonyl cyanide m-chlorophenylhydrazone (CCCP), and N,N'-dicyclo-hexylcarbodiimide (DCCD) at pH 6.0 elicited the complete release of preaccumulated [H-3]tetraphenylphosphonium bromide and [C-14]salicylic acid, with a concomitant depletion of DELTA-psi and DELTA-pH. Nisin and DCCD caused rapid drops in intracellular ATP levels from 1.2 to 0.01 and 0.06 nmol/mg of cells (dry weight), respectively. Cells exposed to nisin and DCCD lost the ability to form colonies, thus suggesting that DELTA-psi and DELTA-pH are necessary for cell viability. The data suggest that depletion of DELTA-p and exhaustion of cellular ATP reserves are the basis for nisin inhibition of C. sporogenes PA 3679.