PEPTIDES PRODUCED BY NATIVE Lactococcus lactis Ella8 IMPAIRS MEMBRANE INTEGRITY OF FOOD PATHOGENS

Previously, we have isolated a Lactococcus lactis UTNElla8, a native strain originated from wild-type fruits of humid mesothermal region of Esmeraldas province, Ecuador and demonstrated its antimicrobial activity. Nonetheless, its mode of action remain unknown. This study was aimed to elucidate the mode of action of peptides of Ella8 against foodborne pathogens. The addition of partial purified Ella8 peptides (PPElla8) at the final concentration 1 MIC to the E. coli suspension cells at exponential (OD605 = 0.7) growth phase resulted in a decrease with 1.2 (log) order of magnitude compared to the control in the absence of the peptide. PPElla8 has marginal activity (>1 log difference) against Salmonella cell culture (0.79 log difference). No effect on cell viability was observed when the peptides were combined with EDTA suggesting that the presence of a chelating agent does not interfered with the antimicrobial activity. The membrane of E. coli was disrupted by the PPElla8 causing the release of beta-galactosidase by the target cell. Moreover, we showed that the integrity of the target cell membrane was affected by PPElla8 leading to the leakage of DNA/RNA molecules and cellular death. The positive effect of PPElla8 towards the delay on rottenness and molds forming on tomato fruits stored at the room temperature demonstrated its bioprotective potential.