Mesentericin Y105, a bacteriocin produced by a Leuconostoc mesenteroides strain, dissipates the plasma membrane potential of Listeria monocytogenes and inhibits the transport of leucine and glutamic acid. It also induces an efflux of preaccumulated amino acids from cells. In addition, the bacteriocin uncouples mitochondria by increasing state 4 respiration and decreasing state 3 respiration. The bacteriocin inhibits ATP synthase and adenine nucleotide translocase of the organelle while the affinity of ADP for its carrier is not modified. The results suggest that mesentericin Y105 acts by inducing, directly or indirectly, pore formation in the energy-transducing membranes, especially those of its natural target.Bacteriocins are antibacterial peptides or proteins that are secreted by bacteria and act on target cells by various mechanisms, most of which are, as yet, unclear. In the group of colicins, two classes may be distinguished on the basis of their mode of action. The major class contains colicins (El, Ia, A, B, K, and N) which kill sensitive cells by forming ion channels in their cytoplasmic membranes (3). The second class contains those colicins displaying a nuclease action (D, E2, E3, M, and V). Nisin is the best known bacteriocin produced by lactic acid bacteria. It has a wide spectrum of activity on gram-positive bacteria (12) and various Salmonella species and other gram-negative organisms (23). The bacteriocin alters the permeability of the cytoplasmic membrane, leading to the efflux of amino acids and dissipating the membrane potential and ionic gradients (20). Another bacteriocin, lactostrepcin 5 (Lac 5), which disrupts the integrity of the cell membrane of Lactococcus lactis cells, leads to the leakage of ions and ATP (28). Lactococcin A, which acts preferentially on lactococci, increases the permeability of the cytoplasmic membrane of whole cells (26), inhibits amino acid transport into sensitive cells and causes efflux of preaccumulated amino acids.The bacteriocin mesentericin Y105 (mY105) produced by Leuconostoc mesenteroides Y105 exerts a bactericidal effect on Listeria monocytogenes E20 (6-8). It is a low-molecularmass peptide (composed of 36 amino acids) that is highly thermostable and acidostable. Its primary structure closely resembles that of other recently discovered bacteriocins: leucocin A-UAL187 (5), pediocin PA-1 (9), and sakacin P and curvacin A (25).In this report, we present some biochemical details of the mode of action of bacteriocin mY105. In particular, its effect on L. monocytogenes E20 membrane potential was determined by using the fluorescent probe rhodamine 123 (Rh 123) and flow cytometry. Amino acid transport into Listena monocytogenes has also been investigated, in addition to an analysis of the effects of the bacteriocin on various functions of isolated mammalian mitochondria.Action of the bacteriocin mY105 on the membrane potential According to these data, we could predict that the decrease in the membrane potential, in our experiments, would not be greater than 40%. A...
