Subinhibitory concentrations of cinnamaldehyde interfere with quorum sensing.
OBJECTIVE
To investigate the effect of cinnamaldehyde (CA) on transcription from selected quorum sensing (QS) promoters.


RESULTS
The action of CA on QS was assayed using three E. coli green fluorescent protein (GFP) based bioreporters (two inducible and the other constitutive) and two Vibrio harveyi bioluminescent reporter strains. LuxR-mediated transcription from the P(luxI) promoter, which is induced by 3-oxo-C6-homoserine lactone (HSL), was reduced by 70 per cent following exposure to 200 micromol l(-1) CA (26 ppm). The bioluminescence of Vibrio harveyi BB886, which is mediated by 3-hydroxy-C4-HSL, was reduced by 55 per cent after exposure to 60 micromol l(-1) CA (8 ppm), and 100 micromol l(-1) CA (13 ppm) inhibited the bioluminescence of the autoinducer-2 (AI-2) responsive reporter strain V. harveyi BB170 by nearly 60 per cent. CA did not inhibit the growth of the bioreporter strains at these concentrations. CA had a minimal effect on LasR promoter activity, induced by 3-oxo-C12-HSL.


CONCLUSIONS
Low concentrations of CA were effective at inhibiting two types of acyl homoserine lactone mediated QS, and also autoinducer-2 mediated QS.


CONCLUSIONS
Because CA is widely used in the food and flavour industries, its potential to affect bacterial QS regulated processes should be recognized.
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Department of Biology, Georgia State University, Atlanta, GA 30303 USA.
Afre
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Gilbert
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D000171:Acrolein / Q000031:analogs & derivatives* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004926:Escherichia coli / Q000187:drug effects; D053038:Quorum Sensing / Q000187:drug effects*; D012097:Repressor Proteins / Q000502:physiology; D015534:Trans-Activators / Q000502:physiology; D014158:Transcription, Genetic / Q000187:drug effects; D014733:Vibrio / Q000187:drug effects
D012097:Repressor Proteins; D015534:Trans-Activators; C064778:LuxR autoinducer binding proteins; D000171:Acrolein; C012843:cinnamaldehyde