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Published on: June 30, 2023
Qualitative and Quantitative Changes to Escherichia coli during Treatment with Magainin 2 Observed in Native
Kanesha Overton1, Helen M Greer1, Megan A Ferguson2
1Department of Biology , Cottey College , 1000 West Austin Boulevard , Nevada , Missouri 64772 , United States.
Abstract:
The bacterial membrane has been suggested as a good target for future antibiotics, so it is important to understand how naturally occurring antibiotics like antimicrobial peptides (AMPs) disrupt those membranes. The interaction of the AMP magainin 2 (MAG2) with the bacterial cell membrane has been well characterized using supported lipid substrates, unilamellar vesicles, and spheroplasts created from bacterial cells. However, to fully understand how MAG2 kills bacteria, we must consider its effect on the outer membrane found in Gram-negative bacteria. Here, we use atomic force microscopy (AFM) to directly investigate MAG2 interaction with the outer membrane of Escherichia coli and characterize the biophysical consequences of MAG2 treatment under native conditions. While propidium iodide penetration indicates that MAG2 permeabilizes cells within seconds, a corresponding decrease in cellular turgor pressure is not observed until minutes after MAG2 application, suggesting that cellular homeostasis machinery may be responsible for helping the cell maintain turgor pressure despite a loss of membrane integrity. AFM imaging and force measurement modes applied in tandem reveal that the outer membrane becomes pitted, more flexible, and more adhesive after MAG2 treatment. MAG2 appears to have a highly disruptive effect on the outer membrane, extending the known mechanism of MAG2 to the Gram-negative outer membrane.
Insights
Antimicrobial peptides like magainin 2 (MAG2) disrupt bacterial membranes. This study reveals MAG2
Area of Science:
- Microbiology
- Biophysics
- Biochemistry
Background:
- Bacterial membranes are crucial targets for novel antibiotics.
- Antimicrobial peptides (AMPs) are natural compounds that disrupt bacterial membranes.
- Magainin 2 (MAG2) is a well-studied AMP, but its effect on Gram-negative outer membranes needs further investigation.
Purpose of the Study:
- To investigate the interaction of MAG2 with the outer membrane of Gram-negative bacteria, specifically *Escherichia coli*.
- To characterize the biophysical consequences of MAG2 treatment on the bacterial outer membrane under native conditions.
Main Methods:
- Atomic force microscopy (AFM) was employed to directly visualize MAG2 interaction with the *E. coli* outer membrane.
- AFM imaging and force measurements were used in tandem to assess changes in membrane properties.
- Propidium iodide penetration and cellular turgor pressure were monitored to assess membrane integrity and cell viability.
Main Results:
- MAG2 rapidly permeabilizes *E. coli* cells within seconds.
- A delayed decrease in cellular turgor pressure suggests cellular homeostasis mechanisms counteract immediate pressure loss.
- AFM revealed that MAG2 treatment causes pitting, increased flexibility, and enhanced adhesion of the outer membrane.
Conclusions:
- MAG2 has a highly disruptive effect on the Gram-negative bacterial outer membrane.
- The findings extend the known mechanism of MAG2 action to the complex outer membrane environment of Gram-negative bacteria.
- Understanding MAG2's interaction with the outer membrane is vital for developing new antibiotic strategies.
