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Updated: Aug 1, 2026
Production and Visualization of Bacterial Spheroplasts and Protoplasts to Characterize Antimicrobial Peptide Localization
Published on: August 11, 2018
Atomic force microscopy study of the effect of antimicrobial peptides on the cell envelope of Escherichia coli
M Meincken1, D L Holroyd, M Rautenbach
1UNESCO Associated Centre for Macromolecules, Department of Chemistry, University of Stellenbosch, Matieland, South Africa.
Abstract:
The influences of the antibacterial magainin 2 and PGLa from the African clawed frog (Xenopus laevis) and the hemolytic bee venom melittin on Escherichia coli as the target cell were studied by atomic force microscopy (AFM). Nanometer-scale images of the effects of the peptides on this gram-negative bacterium's cell envelope were obtained in situ without the use of fixing agents. These high-resolution AFM images of the surviving and intact target cells before and after peptide treatment showed distinct changes in cell envelope morphology as a consequence of peptide action. Although all three peptides are lytic to E. coli, it is clear from this AFM study that each peptide causes distinct morphological changes in the outer membrane and in some cases the inner membrane, probably as a consequence of different mechanisms of action.
Insights
Antibacterial peptides magainin 2, PGLa, and melittin were studied using atomic force microscopy (AFM) on Escherichia coli. AFM revealed distinct morphological changes in the bacterial cell envelope, indicating varied mechanisms of action for these lytic peptides.
Area of Science:
- Microbiology
- Biophysics
- Biochemistry
Background:
- Antimicrobial peptides (AMPs) are crucial in innate immunity.
- Understanding AMPs' mechanisms against bacteria like Escherichia coli is vital.
- Atomic force microscopy (AFM) offers high-resolution, in situ imaging of cellular processes.
Purpose of the Study:
- To investigate the morphological effects of magainin 2, PGLa, and melittin on Escherichia coli using AFM.
- To compare the distinct mechanisms of action of these three lytic peptides at the nanometer scale.
Main Methods:
- Utilized atomic force microscopy (AFM) for in situ imaging of Escherichia coli.
- Observed nanometer-scale changes in the bacterial cell envelope before and after treatment with peptides.
- Analyzed high-resolution images of intact and surviving bacterial cells.
Main Results:
- All three peptides, magainin 2, PGLa, and melittin, demonstrated lytic activity against Escherichia coli.
- AFM imaging revealed distinct morphological alterations in the outer and inner membranes of E. coli.
- Each peptide induced unique changes, suggesting different modes of action.
Conclusions:
- Magainin 2, PGLa, and melittin exhibit distinct mechanisms for disrupting the Escherichia coli cell envelope.
- AFM is a powerful tool for visualizing the nanoscale effects of antimicrobial peptides on bacteria.
- The study provides nanometer-scale insights into peptide-bacterial interactions and potential antimicrobial strategies.
