EFFLUX OF IONS AND ATP DEPLETION INDUCED BY PEDIOCIN PA-1 ARE CONCOMITANT WITH CELL-DEATH IN LISTERIA-MONOCYTOGENES SCOTT-A

The bacteriocin pediocin PA-1 (80 AU ml(-1)), which is produced by Pediococcus acidilactici PAC 1.0, reduced Listeria monocytogenes Scott A viability by 4.6 log. Concomitant with the cell death, pediocin PA-1 induced irreversible K+ and Pi efflux and ATP depletion in concentration-dependent and time-dependent fashions. The maximum amount of intracellular K+ and Pi loss was 520 and 44.6 nmol mg(-1) CDW, respectively. Intracellular ATP levels decreased from 2.8 to 0.029 nmol mg(-1) CDW, corresponding to 98.9% depletion. Less than 0.1% ATP efflux was found with pediocin concentrations up to 200 AU ml(-1). Approximately 10, 40 and 60 min were required for maximum K+ efflux, ATP depletion and Pi efflux, respectively. Moreover, pediocin PA-1 depleted 90% of cytoplasmic ATP when only 25% Pi efflux took place. These results suggest that loss of ATP is due to attempts by the cell to maintain proton-motive force rather than the inability of the cell to produce ATP due to the loss of Pi. Dithiothreitol-treated PA-1 no longer inhibited the growth of L. monocytogenes cells, and caused neither concentration-dependent ion efflux nor ATP depletion.