Investigations of Essential Oils as Quorum Sensing Inhibitors of Vibrio fischeri
Published Apr 1, 2018 · Kallie Hinspeter, Amy M. Danowitz
The FASEB Journal
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Abstract
The misuse of traditional antibiotics has gradually caused a decrease in their efficacy. As bacterial resistance continues to spread, the need for the development of novel methodologies to prevent bacterial development has increased. One area of focus in this field is the inhibition of quorum sensing, a process by which bacteria are able to communicate and collectively regulate gene expression in a cell‐population density dependent manner through small molecules called autoinducers. By blocking cellular receptors which bind autoinducers, bacterial communication can be impeded. This can cause a decrease in community behavior including biofilm formation, production of virulence factors, and bioluminescence. Unlike traditional antibiotics, inhibiting quorum sensing obstructs virulence without preventing bacterial growth and is therefore thought to reduce the evolutionary drive for resistance development. Natural plant products, such as phytochemicals including phenolics, flavonoids, quinones, and alkaloids, have been shown to inhibit virulence factor production, quorum sensing, and microbial growth. This research initially aimed to examine the quorum sensing inhibition properties of select essential oils on Vibrio fischeri, a bioluminescent bacteria, through photometric assays. As the bioluminescent properties of Vibrio fischeri function through a quorum‐dependent pathway, the examination of this species allows for the easy detection of quorum sensing inhibition through the quantification of light production. Essential oils tested include caraway (Carum and Carvi oils), cistus or labdanum (Cistus ladaniferus), elemi (Canarium luzonicum), fir needle (Abies sibirica), and pine (Pinus sylvestris). Ongoing experimental results suggest that the essential oils originally selected for this research display antibacterial properties over quorum sensing inhibition. Due to this, future directions will likely move towards an examination of the antibiotic properties of these oils in Escherichia coli, a very common Gram‐negative pathogen that can be harmless in certain strains.