Novel Alkyl Thioether Cyclodextrin Derivatives Against Bacterial Quorum Sensing in Aliivibrio fischeri

Aliivibrio fischeri is a heterotrophic marine bacterium capable of bioluminescence which is controlled by quorum sensing. Quorum sensing is a population density dependent communication method for the bacteria to coordinate their activities by producing and detecting low-molecular-weight signal molecules. The effective infectivity of the bacteria is based on various virulence factors controlled by quorum sensing. Cyclodextrins, a family of toroidal-shaped oligosaccharides, reversibly encapsulate in their hydrophobic interior the fatty acid acyl chain of the signal molecules, thus preventing their binding to the receptors and interrupting the bacterial communication consequently the expression of various properties including different virulence factors.Short-term tests were performed to examine the potential quorum quenching ability of newly prepared cyclodextrin derivatives: α- and β-cyclodextrins monosubstituted with alkylthio moieties. In these derivatives one of the modifiable hydroxyl groups of the cyclodextrin molecule is substituted with an alkylthio group of six, ten, twelve or sixteen carbon atoms. Cyclodextrins at 1.563–12.5 mM concentrations were added to A. fischeri culture in exponential growth phase, then the bioluminescence intensity, the population growth and the cell viability were kept under systematic review.According to our results, the cyclodextrins have inhibitory effect on the quorum sensing system of A. fischeri, the alkylthio-substitution improves this effect compared to the native molecules and the length of the alkyl chain has significant influence on the quorum quenching efficiency.