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Antimicrob Agents Chemother. 2018 Apr 26;62(5). pii: e02318-17. doi: 10.1128/AAC.02318-17. Print 2018 May.

Alginate Oligosaccharide-Induced Modification of the lasI-lasR and rhlI-rhlR Quorum-Sensing Systems in Pseudomonas aeruginosa.

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Advanced Therapies Group, Cardiff University School of Dentistry, Cardiff, United Kingdom.
School of Pharmacy and Pharmaceutical Sciences, Cardiff University, Cardiff, United Kingdom.
Department of Biosciences, College of Life and Environmental Sciences, Exeter University, Exeter, United Kingdom.
AlgiPharma AS, Sandvika, Norway.
Advanced Therapies Group, Cardiff University School of Dentistry, Cardiff, United Kingdom


Pseudomonas aeruginosa plays a major role in many chronic infections. Its ability to readily form biofilms contributes to its success as an opportunistic pathogen and its resistance/tolerance to antimicrobial/antibiotic therapy. A low-molecular-weight alginate oligomer (OligoG CF-5/20) derived from marine algae has previously been shown to impair motility in P. aeruginosa biofilms and disrupt pseudomonal biofilm assembly. As these bacterial phenotypes are regulated by quorum sensing (QS), we hypothesized that OligoG CF-5/20 may induce alterations in QS signaling in P. aeruginosa QS regulation was studied by using Chromobacterium violaceum CV026 biosensor assays that showed a significant reduction in acyl homoserine lactone (AHL) production following OligoG CF-5/20 treatment (≥2%; P < 0.05). This effect was confirmed by liquid chromatography-mass spectrometry analysis of C4-AHL and 3-oxo-C12-AHL production (≥2%; P < 0.05). Moreover, quantitative PCR showed that reduced expression of both the las and rhl systems was induced following 24 h of treatment with OligoG CF-5/20 (≥0.2%; P < 0.05). Circular dichroism spectroscopy indicated that these alterations were not due to steric interaction between the AHL and OligoG CF-5/20. Confocal laser scanning microscopy (CLSM) and COMSTAT image analysis demonstrated that OligoG CF-5/20-treated biofilms had a dose-dependent decrease in biomass that was associated with inhibition of extracellular DNA synthesis (≥0.5%; P < 0.05). These changes correlated with alterations in the extracellular production of the pseudomonal virulence factors pyocyanin, rhamnolipids, elastase, and total protease (P < 0.05). The ability of OligoG CF-5/20 to modify QS signaling in P. aeruginosa PAO1 may influence critical downstream functions such as virulence factor production and biofilm formation.


OligoG CF-5/20; Pseudomonas aeruginosa; alginate; biofilms; homoserine lactone; natural antimicrobial products; quorum-sensing inhibitor

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