predominated infection therapy. Furanone derivatives from plants in South Florida and garlic as well as other dietary phytochemicals, such as Curcuma longa, caffeine and vanilla extract, are considered to be potent inhibitors of QS and its regulatory factors. This work aimed to investigate the potential of cinnamon oil, a dietary supplement used worldwide, to inhibit QS and the associated virulence factors of pathogenic P. aeruginosa PAO1. Cinnamon oil is a plant-derived oil, and its composition may vary depending on the bulk, the species of plant used, and the method of preparation. Cinnamon oil has been reported to exhibit potential antimicrobial activities against wide range of microorganisms. We used sub-lethal concentrations of cinnamon oil that are insufficient to neutralize microbes. No significant differences in growth patterns were observed between control and oil-treated P. 12 / 18 Cinnamon Oil 1702259-66-2 web Inhibits Pseudomonas aeruginosa Quorum-Sensing Fig PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/19722344 8. Quantification of PAO1 biofilms in the presence of various concentrations of cinnamon oil. The biofilms were quantified after 24 h of incubation and are represented as adhesion units. The error bars indicate the standard deviations of three measurements, and the data were normalized according to the OD600. , P<0.0001 compared with the control. , P<0.00001 compared with the control. doi:10.1371/journal.pone.0135495.g008 aeruginosa PAO1, C. violaceum CV026 or E coli pJN105LpSC11 at the lower tested concentrations, 0.1 PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/19723429 and 0.2 l/ml, in the growth curve analysis. The growth curve data showed that cinnamon oil at low concentrations inhibits QS, while the remaining concentrations tested in the study affect both QS and the growth rate. Our results are consistent with the findings of Kim et al., who reported decreases in biofilm formation and toxin production in the presence of different sub-lethal concentrations of cinnamaldehyde. Kim et al. also demonstrated a delay in reaching log phase in all treated samples. However, cinnamaldehyde, which has been reported to be the major component of cinnamon oil, has been cited for its anti-QS activity in the Vibrio harveyi system by Brackman et al.. These investigators reported that cinnamaldehyde and its derivatives are potentially useful anti-pathogenic compounds for the treatment of vibriosis and interfere with AI-2-based QS by decreasing the ability of LuxR to bind to its target promoter sequence. Similarly, Yap 13 / 18 Cinnamon Oil Inhibits Pseudomonas aeruginosa Quorum-Sensing Fig 9. Microscopy images of P. aeruginosa PAO1 biofilms that formed with 0.8 l/ml 
and without cinnamon oil. Scanning electron microscopy and light microscopy images. Inhibition of GFP-PAO1 biofilm formation. Significant reduction in the DNA content of the GFP-PAO1 biofilm. Overlay of images displaying the reduction in extracellular DNA associated with the GFP-PAO1 biofilm. In the image, extracellular DNA is indicated with an arrowhead. A reduction in EPS production was observed after staining P. aeruginosa PAO1 with FITC-conA. This effect is evident from the scattered appearance of the cells in the treated samples. doi:10.1371/journal.pone.0135495.g009 PS et al., 2014 reported the membrane-permeabilizing effects of Cinnamon verum oil on treated cultures of multi-drug-resistant Escherichia coli J53 R1, further demonstrating the antiQS activity of this oil. We showed that complete cinnamon oil is active against QS-based virulence factors in P. aeruginosa PAO1, in which the
