Extracytoplasmic stress responses induced by antimicrobial cationic polyethylenimines.
The ability of an antimicrobial, cationic polyethylenimine (PEI+) to induce the three known extracytoplasmic stress responses of Escherichia coli was quantified. Exposure of E. coli to PEI+ in solution revealed specific, concentration-dependent induction of the Cpx extracytoplasmic cellular stress response, ~2.0-2.5-fold at 320 μg/mL after 1.5 h without significant induction of the σ(E) or Bae stress responses. In comparison, exposure of E. coli to a non-antimicrobial polymer, poly(ethylene oxide) (PEO), resulted in no induction of the three stress responses. The antimicrobial small molecule vanillin, a known membrane pore-forming compound, was observed to cause specific, concentration-dependent induction of the σ(E) stress response, ~6-fold at 640 μg/mL after 1.5 h, without significant induction of the Cpx or Bae stress responses. The different stress response induction profiles of PEI+ and vanillin suggest that although both are antimicrobial compounds, they interact with the bacterial membrane and extracytoplasmic area by unique mechanisms. EPR studies of liposomes containing spin-labeled lipids exposed to PEI+, vanillin, and PEO reveal that PEI+ and PEO increased membrane stability, whereas vanillin was found to have no effect.
Department of Chemistry, United States Naval Academy, 572 Holloway Rd., Annapolis, MD 21402, USA.
Blaine A
BA
Lander
Kyle D
KD
Checchi
Stephen A
SA
Koplin
Virginia F
VF
Smith
Tammy L
TL
Domanski
Daniel D
DD
Isaac
Shirley
S
Lin
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D011094:Polyethyleneimine / Q000494:pharmacology*
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D011094:Polyethyleneimine