1. Mode of Action of a Bacteriocin (J46) Produced by Lactococcus lactis subsp. cremoris J46
C Barrena-Gonzalez, E Huot, H Petitdemange J Food Prot. 1996 Sep;59(9):955-962. doi: 10.4315/0362-028X-59.9.955.
The mode of antibacterial action of bacteriocin J46, a bacteriocin from Lactococcus lactis subsp. cremoris , was studied. Bacteriocin J46 specifically adsorbed on susceptible bacteria. Adsorption on gram-negative or gram-positive resistant strains was significantly lower. Bacteriocin J46 has been shown to be bactericidal towards log-phase indicator cells but ineffective against stationary cells. In addition energy-depleted log-phase cells were unaffected. It was shown that both a ΔpH and a Δ Ψ were required for bacteriocin J46 activity. Using a continuous fermentation procedure, we were able to confirm the crucial importance of the physiological state of the indicator on its sensitivity. Negligible antibacterial activity was detected against cells of the sensitive strain, L. lactis subsp. cremoris SC11 (μmax: 0.93) growing at dilution rates below about 0.6 h-1 even with high bacteriocin concentrations. When assays were conducted in a growth medium, there was a continuous decrease in bacterial viability as a function of time, suggesting that actively growing cells were sensitive to the bactericidal activity of bacteriocin J46. This antibacterial peptide caused an immediate loss of cellular K+ and a hydrolysis of internal ATP in L. lactis subsp. cremoris SC11. The initial rate of K+ efflux increased with increasing bacteriocin concentration, being saturated at approximately 10,000 AU/ml. Decreasing the ionic strength of the assay buffer did not result in a significant modification of the K+ efflux rate induced by J46 addition. Bacteriocin activity was pH dependent: at pH 7.0, no adsorption and no antibacterial activity were detected. These results suggest that the bactericidal activity of bacteriocin J46 was due to the formation of pores in the cytoplasmic membrane of log-phase cells, stationary cells remaining unaffected.
2. Comparative effectiveness of nisin and bacteriocin J46 at different pH values
E Huot, C Barrena-Gonzalez, H Petitdemange Lett Appl Microbiol. 1996 Jan;22(1):76-9. doi: 10.1111/j.1472-765x.1996.tb01112.x.
A comparative study of the inhibitory activity of nisin, the well-known lantibiotic produced by certain strains of Lactococcus lactis subsp. lactis, and of the bacteriocin produced by L. lactis subsp. cremoris J46, a strain previously isolated from fermented milk, was conducted. For both bacteriocins, the activity against L. lactis subsp. cremoris decreased with increasing pH. In addition, the bacteriocin preparations were more stable at 4 degrees than at 20 degrees C. The influence of the storage temperature was more crucial for nisin. Essentially the same activity was observed for bacteriocin J46 stored for 3 h at 4 degrees or 20 degrees C. More interesting was the observed stability of bacteriocin J46 at pH values between 5.8 and 6.8. For example, about 23% of nisin activity was lost at pH 6.4 whereas no loss of bacteriocin J46 activity was observed.
3. Chemical synthesis and characterization of J46 peptide, an atypical class IIa bacteriocin from Lactococcus lactis subsp. cremoris J46 Strain
Samar Lasta, Ziad Fajloun, Hervé Darbon, Pascal Mansuelle, Nicolas Andreotti, Jean-Marc Sabatier, Abdellatif Boudabous, François Sampieri J Antibiot (Tokyo). 2008 Feb;61(2):89-93. doi: 10.1038/ja.2008.116.
Bacteriocin J46 is a 27-residue polypeptide produced by Lactococcus lactis subsp. cremoris J46 in fermented milk. The natural form of J46 (nJ46) exhibits a broad antimicrobial spectrum. Herein, we produced the synthetic form of J46 (sJ46) by solid-phase chemical synthesis. The biochemical and physico-chemical properties of sJ46, as well as its antimicrobial activity, were found to be identical to those of its natural counterpart nJ46. It showed a potent antimicrobial activity against both lactic acid bacteria and other Gram-positive microorganisms. (1)H-NMR conformational analysis of sJ46 indicates that it adopts a flexible random coil structure.
