Isolation, identification, and characterization of small bioactive peptides from Lactobacillus GG conditional media that exert both anti-Gram-negative and Gram-positive bactericidal activity.

ABSTRACT

OBJECTIVES: Diarrheal diseases remain a major human plague that still claim millions of lives every year. Probiotics, including Lactobacillus GG (LGG), are known to have a beneficial effect on diarrheal diseases, but their mechanism of action has not yet been completely established. Therefore, the main objective of this work was to identify and characterize moieties elaborated by LGG that exert antibacterial activity. MATERIALS AND METHODS: Lactobacillus GG conditional media was subjected to liquid chromatography/mass spectrometry. The identified peptides were synthesized by Symphony peptide synthesizer and purified by HPLC using Dynamax reverse-phase C18 column. Using A600 measurement and tested for their antibacterial activity. RESULTS: We identified 7 small peptides from LGG cultured media, 2 of which are NPSRQERR and PDENK, retained the antibacterial activity detected with LGG conditional media. The antibacterial activity was exerted against both Gram-negative (Escherichia coli EAEC 042 and Salmonella typhi) and, with less potency, Gram-positive (Staphylococcus aureus) bacteria. CONCLUSIONS: Lactobacillus GG elaborates small peptides showing various degrees of antibacterial activity. NPSRQERR showed the most potent antibacterial effect that was detected both in Gram-negative and Gram-positive microorganisms. These synthetic peptides may represent novel tools for the treatment of bacterial infectious diseases.