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Microbiology. 2018 Sep;164(9):1087-1097. doi: 10.1099/mic.0.000692. Epub 2018 Jul 12.

Cinnamaldehyde disrupts biofilm formation and swarming motility of Pseudomonas aeruginosa.

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1​Department of Chemistry and Biotechnology, School of Science, Swinburne University of Technology, Hawthorn, Victoria, Australia.
2​Singapore Centre for Environmental Life Sciences Engineering (SCELSE), Nanyang Technological University, Nanyang Avenue, Singapore.
3​The School of Biological Sciences, Nanyang Technological University, Nanyang Avenue, Singapore.
4​The ithree Institute, The University of Technology Sydney, Sydney, Australia.
5​School of BioSciences, The University of Melbourne, Parkville, Victoria, Australia.


Bacterial biofilms can cause serious health care complications associated with increased morbidity and mortality. There is an urge to discover and develop new biofilm inhibitors from natural products or by modifying natural compounds or understanding the modes of action of existing compounds. Cinnamaldehyde (CAD), one of the major components of cinnamon oil, has been demonstrated to act as an antimicrobial agent against a number of Gram-negative and Gram-positive pathogens, including Pseudomonas aeruginosa, Helicobacter pylori and Listeria monocytogenes. Despite the mechanism of action of CAD against the model organism P. aeruginosa being undefined, based on its antimicrobial properties, we hypothesized that it may disrupt preformed biofilms of P. aeruginosa. The minimum inhibitory concentration (MIC) of CAD for planktonic P. aeruginosa was determined to be 11.8 mM. Membrane depolarization assays demonstrated disruption of the transmembrane potential of P. aeruginosa. CAD at 5.9 mM (0.5 MIC) disrupted preformed biofilms by 75.6 % and 3 mM CAD (0.25 MIC) reduced the intracellular concentrations of the secondary messenger, bis-(3'-5')-cyclic dimeric guanosine monophosphate (c-di-GMP), which controls P. aeruginosa biofilm formation. The swarming motility of P. aeruginosa was also reduced by CAD in a concentration-dependent manner. Collectively, these findings show that sub-MICs of CAD can disrupt biofilms and other surface colonization phenotypes through the modulation of intracellular signalling processes.


Cinnamaldehyde; Pseudomonas aeruginosa; biofilm inhibition; c-di-GMP; natural products


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