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Production and Visualization of Bacterial Spheroplasts and Protoplasts to Characterize Antimicrobial Peptide Localization
10:13

Production and Visualization of Bacterial Spheroplasts and Protoplasts to Characterize Antimicrobial Peptide Localization

Published on: August 11, 2018

Functional interrelationships between cell membrane and cell wall in antimicrobial peptide-mediated killing of

Yan Q Xiong1, Kasturi Mukhopadhyay, Michael R Yeaman

  • 1LA Biomedical Research Institute at Harbor-UCLA St. John's Cardiovascular Research Center, RB-2, 1124 West Carson Street, Torrance, CA 90502, USA. yxiong@ucla.edu

Antimicrobial Agents and Chemotherapy
|July 29, 2005
PubMed

Insights

Antimicrobial peptides (APs) kill Staphylococcus aureus by disrupting its cell membrane, but membrane permeabilization alone isn't sufficient. The cell wall and intracellular factors also play roles in AP-induced bacterial death.

Area of Science:

  • Microbiology
  • Biochemistry
  • Cell Biology

Background:

  • Antimicrobial peptides (APs) are crucial for innate immunity.
  • Cytoplasmic membrane (CM) perturbation is a proposed mechanism for APs against Staphylococcus aureus.
  • The role of membrane permeabilization (MP) versus other factors in AP-induced lethality remains unclear.

Purpose of the Study:

  • To investigate the relationship between AP-induced MP and lethality in S. aureus.
  • To compare AP activity on whole cells, cell wall-free protoplasts, and model liposomes.
  • To determine if MP alone is sufficient for AP-induced killing.

Main Methods:

  • Studied four APs (tPMP-1, hNP-1, gramicidin D, polymyxin B) with varying structures.
  • Quantified MP using fluorometric calcein release assay.
  • Compared AP effects on S. aureus whole cells, protoplasts, and liposomes mimicking CM composition.

Main Results:

  • Most APs caused concentration-dependent MP and killing of whole cells, but not protoplasts.
  • Protoplasts showed reduced AP susceptibility due to altered CM lipid composition and fluidity.
  • Liposomal MP by certain APs correlated with whole cell MP, suggesting model validity.

Conclusions:

  • Structurally distinct APs likely employ different killing mechanisms.
  • Membrane permeabilization is necessary but not sufficient for AP-induced S. aureus killing.
  • A complex interplay between the CM and cell wall is critical for AP efficacy.

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