Transmission Electron Microscopic Observations of Membrane Effects of Antibiotic Cecropin B on Escherichia coli

Hueih Min Chen*, Shiu Chiu Chan, Jao Chang Lee, Chia-Ching Chang, Marudhamuthu Murugan, Ralph W. Jack

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

30 Scopus citations

Abstract

The pathway of cell membrane lysis by the peptide antibiotic cecropin B (CB), which contains both a hydrophobic and an amphipathic, α-helix, was analysed by assessing the morphological changes of Escherichia coli following treatment with the peptide. Exposure of green fluorescent protein (GFP)-expressing E. coli to CB does not lead to an efflux of GFP. Moreover, transmission electron microscopic (TEM) examination of cecropin B-treated cells showed that severe swelling precedes cell death and that the outer membrane becomes distended away from the plasma membrane. Using immuno-gold staining and TEM of E. coli expressing the maltose-binding protein in the cytoplasm, it was apparent that the protein remains restricted to the cytoplasmic compartment. These observations suggest that CB causes gross disruption of the outer membrane of Gram-negative bacteria. Circular dichroism measurements of CB in the presence of cell membrane-mimicking liposomes showed that CB forms secondary structure dependent on the ratio of [lipid]/[peptide]. These observations from this study are important for the future design of custom antimicrobial peptides.

Original languageEnglish
Pages (from-to)423-430
Number of pages8
JournalMicroscopy Research and Technique
Volume62
Issue number5
DOIs
StatePublished - 1 Dec 2003

Keywords

  • Cecropin B
  • Defence peptide
  • Escherichia coli
  • Peptide antibiotic
  • Peptide-membrane interaction
  • Transmission electron microscopy

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