Functional Amyloids Keep Quorum Sensing Molecules in Check [Molecular Biophysics]

January 13th, 2015 by Seviour, T., Hansen, S. H., Yang, L., Yau, Y. H., Wang, V. B., Stenvang, M. R., Christiansen, G., Marsili, E., Givskov, M., Chen, Y., Otzen, D. E., Nielsen, P. H., Shochat, S. G., Kjelleberg, S., Dueholm, M. S.

The mechanism by which extracellular metabolites including redox mediators and quorum sensing signaling molecules, traffic through the extracellular matrix of biofilms is poorly explored. We hypothesize that functional amyloids, abundant in natural biofilms and possessing hydrophobic domains, retain these metabolites. Using surface plasmon resonance, we demonstrate that the quorum sensing (QS) molecules, 2-heptyl-3,4- dihydroxyquinoline (PQS) and N-(3- oxododecanoyl)-L-homoserine lactone (3-oxo- C12-HSL), and the redox mediator pyocyanin bind with transient affinity to functional amyloids from Pseudomonas (Fap). Their high hydrophobicity predisposes them to signal- amyloid interactions, but specific interactions also play a role. Transient interactions allow for rapid association and dissociation kinetics, which make the QS molecules bioavailable and at the same time secure within the extracellular matrix as a consequence of serial bindings. Retention of the QS molecules was confirmed using P. aeruginosa PAO1 based PQS and 3-oxo-C12-HSL reporter assays, showing that Fap fibrils pre-treated with the QS molecules activate the reporters even after sequential washes. Pyocyanin retention was validated by electrochemical analysis of pyocyanin pre-treated Fap fibrils subjected to the same washing process. Results suggest that QS molecules-amyloid interactions are probably important in turbulent environments commonly encountered in natural habitats.