Extracytoplasmic cellular stress responses induced by cationic polyethylenimines and known pore‐forming compounds

Abstract

The mechanisms of antimicrobial activity of a cationic polyethylenimine (PEI+) and a small molecule pore‐forming compound, vanillin, are thought to involve disruption of bacterial cell membranes. These proposed mechanisms were studied by measuring the induction of the three known extracytoplasmic stress responses (Cpx, σE and Bae) of the Gram‐negative bacterium Escherichia coli. PEI+ specifically induced the Cpx stress response approximately 2‐fold in a dose‐dependent manner at concentrations ranging from 80–320 μg/mL. Vanillin induced the σE stress response 4–12‐fold at concentrations ranging from 320–960 μg/mL. The implications of the observed differences in the induction of extracytoplasmic stress responses between PEI+ and vanillin on the antimicrobial mechanisms of these compounds will be discussed.