Chickpea-derived antimicrobial peptides compromise Escherichia coli O157:H7 membrane biophysics through...

Antimicrobial peptides (AMPs) have attracted significant attention due to their potent antimicrobial activity. In our previous research, two functionalized chickpea-derived Leg2 antimicrobial peptides (FCLAPs) exhibited superb bactericidal effects against Escherichia coli O157:H7 (MIC, 2.5-4.7 μM). However, the quantitative interactions between FCLAPs and bacterial membrane lipids remain unclear. Here, optical tweezer-based nanomechanical measurements were employed to quantify the interaction forces between FCLAPs and model lipid membranes. The interaction force between FCLAPs and phospholipid membranes reached 2-6 pN, which was markedly higher than that measured for lipopolysaccharide (LPS)-incorporated membranes (0.5-0.7 pN). Experiments using LPS-deficient E. coli mutants further supported that LPS modulates peptide-membrane interactions. Complementary fluorescence assays indicated preferential partitioning of FCLAPs toward phospholipid membranes. Optical tweezer-based membrane tether pulling experiments further showed that FCLAPs altered membrane mechanical properties, including increased membrane tension (12-15 pN/μm) and bending rigidity (86-109 K_bT). Together, these results suggest that the LPS layer acts as a physical barrier that can sequester antimicrobial peptides, thereby reducing their effective access to membrane phospholipids and ultimately modulating antimicrobial activity. This study provides quantitative insights into AMPs-membrane interactions from a membrane biophysical perspective.