Binding, inactivation, and adhesion forces between antimicrobial peptide cecropin P1 and pathogenic E. coli

Area of Science:

• Biochemistry
• Materials Science
• Microbiology

Background:

• The antimicrobial peptide cecropin P1 (CP1) shows broad-spectrum activity against planktonic bacteria like Escherichia coli (E. coli).
• The efficacy of immobilized CP1 against bacteria adhering to surfaces remains underexplored.
• Surface immobilization strategies can influence antimicrobial peptide performance.

Purpose of the Study:

• To investigate how different immobilization methods of CP1 on surfaces affect its interaction with and killing of E. coli.
• To characterize the binding of CP1 to gold and silicon nitride surfaces.
• To correlate bacterial lipopolysaccharide (LPS) structure with CP1 adhesion and antimicrobial activity.

Main Methods:

• Immobilization of CP1 and cysteine-terminated CP1 (CP1-cys) onto gold and silicon nitride surfaces.
• Quartz Crystal Microbalance with Dissipation monitoring (QCM-D) to characterize non-specific and covalent binding.
• Atomic Force Microscopy (AFM) to measure bacterial adhesion forces.
• Testing antimicrobial activity against twelve E. coli strains with varying LPS structures.

Main Results:

• CP1-cys immobilized on gold via thiol linkage showed higher density compared to CP1 on silicon nitride.
• Bacterial adhesion was strongest for E. coli strains with long O-antigens, suggesting interaction with the hydrophilic LPS portion.
• Antimicrobial activity against E. coli was highly dependent on the immobilization method; CP1 on silicon nitride was more effective than CP1-cys on gold.

Conclusions:

• Surface immobilization method is a critical factor determining the antimicrobial efficacy of CP1 against E. coli.
• Bacterial LPS structure influences CP1 binding, with longer O-antigens promoting stronger adhesion.
• Optimizing peptide-surface interactions is key to developing effective surface-bound antimicrobial agents.