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Effects of Antibacterial Peptide F1 on Bacterial Liposome Membrane Integrity
Qun Wang1, Bo Peng1,2, Mingyue Song1
1College of Food Science, South China Agricultural University, Guangzhou, China.
Abstract:
Previous studies from our lab have shown that the antimicrobial peptide F1 obtained from the milk fermentation by Lactobacillus paracasei FX-6 derived from Tibetan kefir was different from common antimicrobial peptides; specifically, F1 simultaneously inhibited the growth of Gram-negative and Gram-positive bacteria. Here, we present follow-on work demonstrating that after the antimicrobial peptide F1 acts on either Escherichia coli ATCC 25922 (E. coli) or Staphylococcus aureus ATCC 63589 (S. aureus), their respective bacterial membranes were severely deformed. This deformation allowed leakage of potassium and magnesium ions from the bacterial membrane. The interaction between the antimicrobial peptide F1 and the bacterial membrane was further explored by artificially simulating the bacterial phospholipid membranes and then extracting them. The study results indicated that after the antimicrobial peptide F1 interacted with the bacterial membranes caused significant calcein leakage that had been simulated by different liposomes. Furthermore, transmission electron microscopy observations revealed that the phospholipid membrane structure was destroyed and the liposomes presented aggregation and precipitation. Quartz Crystal Microbalance with Dissipation (QCM-D) results showed that the antimicrobial peptide F1 significantly reduced the quality of liposome membrane and increased their viscoelasticity. Based on the study's findings, the phospholipid membrane particle size was significantly increased, indicating that the antimicrobial peptide F1 had a direct effect on the phospholipid membrane. Conclusively, the antimicrobial peptide F1 destroyed the membrane structure of both Gram-negative and Gram-positive bacteria by destroying the shared components of their respective phospholipid membranes which resulted in leakage of cell contents and subsequently cell death.
Insights
Antimicrobial peptide F1 from Tibetan kefir disrupts bacterial membranes, causing ion leakage and cell death in both Gram-negative and Gram-positive bacteria. This peptide offers a novel approach to combating diverse bacterial infections.
Area of Science:
- Microbiology
- Biochemistry
- Materials Science
Background:
- Antimicrobial peptide F1, derived from Lactobacillus paracasei FX-6 in Tibetan kefir, exhibits broad-spectrum activity against Gram-negative and Gram-positive bacteria.
- Previous research indicated F1's unique ability to inhibit both bacterial types, necessitating further investigation into its mechanism of action.
Purpose of the Study:
- To elucidate the mechanism by which antimicrobial peptide F1 interacts with and damages bacterial membranes.
- To investigate the effects of F1 on the structural integrity and permeability of bacterial membranes.
Main Methods:
- Exposure of Escherichia coli and Staphylococcus aureus to antimicrobial peptide F1, followed by analysis of membrane deformation and ion leakage.
- Artificial simulation of bacterial phospholipid membranes using liposomes to study F1 interaction via calcein leakage assays.
- Transmission electron microscopy (TEM) to visualize membrane structural changes.
- Quartz Crystal Microbalance with Dissipation (QCM-D) to assess membrane viscoelasticity and quality.
Main Results:
- Antimicrobial peptide F1 caused severe deformation of bacterial membranes in E. coli and S. aureus, leading to potassium and magnesium ion leakage.
- F1 induced significant calcein leakage from liposomes, indicating disruption of artificial phospholipid membranes.
- TEM revealed destruction of liposome membrane structure, aggregation, and precipitation.
- QCM-D demonstrated that F1 reduced liposome membrane quality and increased viscoelasticity, with increased particle size.
Conclusions:
- Antimicrobial peptide F1 directly targets and destroys the phospholipid membrane structure common to both Gram-negative and Gram-positive bacteria.
- This membrane disruption results in the leakage of essential cellular contents, ultimately leading to bacterial cell death.
- F1's mechanism involves damaging shared phospholipid components, making it a potent broad-spectrum antimicrobial agent.
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