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Transmission electron microscopic observations of membrane effects of antibiotic cecropin B on Escherichia coli
Author(s) -
Chen Hueih Min,
Chan ShiuChiu,
Lee JaoChang,
Chang ChiaChing,
Murugan Marudhamuthu,
Jack Ralph W.
Publication year - 2003
Publication title -
microscopy research and technique
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.536
H-Index - 118
eISSN - 1097-0029
pISSN - 1059-910X
DOI - 10.1002/jemt.10406
Subject(s) - cecropin , spheroplast , escherichia coli , bacterial outer membrane , lysis , cytoplasm , membrane , peptide , circular dichroism , biochemistry , biology , cell membrane , green fluorescent protein , maltose binding protein , biophysics , chemistry , antimicrobial peptides , fusion protein , recombinant dna , gene
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. Microsc. Res. Tech. 62:423–430, 2003. © 2003 Wiley‐Liss, Inc.