A novel antimicrobial peptide FxCy2 against Helicobacter pylori: Isolation and purification from Lactobacillus...

Helicobacter pylori resistance to antibiotics is becoming increasingly prevalent, and the search for novel natural antimicrobial agents has become an urgent research focus. In this study, a novel antimicrobial peptide (AMP), FxCy2, was isolated and purified from the fermentation supernatant of Lactobacillus paracasei FX-6. FxCy2 exhibited clear inhibitory activity against H. pylori (MIC＝1.25 mg/mL) and demonstrated synergistic antibacterial effects when combined with the clinically used antibiotic clarithromycin. LC-MS/MS analysis identified FxCy2 as a 16-mer peptide with the amino acid sequence FGANALLGVSLAVKCG (1518.85 Da). Secondary structure analysis showed that FxCy2 contains both β-sheet and α-helical structures, with β-sheet being the dominant form in the solid state and α-helical structure becoming more prominent in aqueous solution. Flow cytometry analysis demonstrated that FxCy2 exhibited potent bactericidal activity against H. pylori. SEM, TEM and fluorescence microscopy further demonstrated that FxCy2 induces cell deformation, compromises membrane integrity and permeability, and ultimately leads to cytoplasmic vacuolization and leakage of intracellular contents. Furthermore, FxCy2 exhibited excellent stability at pH 3-9 and 37-80 °C, with minimal hemolysis and low cytotoxicity, confirming its biosafety. Overall, our findings position FxCy2 as a promising food-derived AMP that holds great potential for the treatment and prevention of H. pylori infections.