Transcriptional Profile of Escherichia coli in Response to Novispirin G10

Abstract

Using a novel methodology, we have investigated the transcriptional response of Escherichia coli to novispirin G10, an α-helical cationic antimicrobial peptide. We show that novispirin G10 induces an exceptionally coherent transcriptional response in E. coli, resulting in upregulation of genes involved in response to osmotic stress, acid shock, phage shock, and antimicrobial peptides, and down-regulation of the heat shock response genes, e.g., dnaJK, GroES, and GroEL. This transcriptional pattern indicates that novispirin G10 acts by compromising the bacterial membrane and possibly also by targeting the heat shock response. The impact of novispirin G10 on E. coli cells was monitored directly using the fluorescent LIVE/DEAD assay verifying that the peptide, indeed, targets bacterial membranes. Furthermore, in agreement with the observed heat shock transcriptional response, we show that overexpression of the heat shock transcription factor in E. coli, σ32, leads to a significant decrease in sensitivity towards novispirin G10.