Antimicrobial Agents and Chemotherapy, January 2003, p. 1-6, Vol. 47, No. 1
0066-4804/03/$08.00+0 DOI: 10.1128/AAC.47.1.1-6.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.
Departments of Pharmacology and Microbiology, University of Pennsylvania, Philadelphia, Pennsylvania 19104
Received 27 June 2002/ Returned for modification 23 August 2002/ Accepted 7 October 2002
Cationic antimicrobial peptides are believed to exert their primary activities on anionic bacterial cell membranes; however, this model does not adequately account for several important structure-activity relationships. These relationships are likely to be influenced by the bacterial response to peptide challenge. In order to characterize the genomic aspect of this response, transcription profiles were examined for Escherichia coli isolates treated with sublethal and lethal concentrations of the cationic antimicrobial peptide cecropin A. Transcript levels for 26 genes changed significantly following treatment with sublethal peptide concentrations, and half of the transcripts corresponded to protein products with unknown function. The pattern of response is distinct from that following treatment with lethal concentrations and is also distinct from the bacterial response to nutritional, thermal, osmotic, or oxidative stress. These results demonstrate that cecropin A induces a genomic response in E. coli apart from any lethal effects on the membrane and suggest that a complete understanding of its mechanism of action may require a detailed examination of this response.
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