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Quorum Sensing (QS) is a communication system used by numerous bacteria to synchronize their behavior according to the cell density. In this way, bacteria secrete and sense small mediating molecules, called autoinducers (AI), which concentration increases in the environment proportionally to bacterial cell number. QS induces major physiological and phenotypic changes such as virulence induction and biofilm formation. Biofilm represents a physical barrier which shelters bacteria poorly sensitive to antimicrobial treatments and favors the apparition of resistance mechanisms. Disturbing QS is referred to as quorum quenching (QQ). This strategy is used by microorganisms themselves to prevent the development of specific group behaviors. Two strategies are mainly employed: the use of quorum sensing inhibitors (QSI) and of quorum quenching enzymes (QQE) that degrades AI. Many studies have been dedicated to identifying QSI (natural or synthetic) as well as QQE and demonstrating their anti-virulence and anti-biofilm effects on numerous bacterial species. Synergistic effects between QQ and traditional treatments such as antibiotherapy or with reemerging phage therapy have been put forward. The efficiency of numerous QSI and QQE was thereby demonstrated either with in vitro or in vivo animal models leading to the development of medical devices containing QSI and QQE to improve already existing treatments.

Background: Pseudomonas aeruginosa orchestrates the expression of many genes by using quorum sensing (QS) communication process. QS relies on an intricate molecular network including two acyl-homoserine lactones (AHL), involved in the modulation of virulence factors production, biofilm formation or antimicrobial sensitivity. Disrupting QS is a promising approach to modulate virulence while not challenging bacterial survival and can be achieved with AHL-degrading lactonases. Methods: Here, we used two lactonases both targeting the signal molecules N-(3-oxododecanoyl)-L-Homoserine lactone (3-oxo-C12 HSL) and butyryl-homoserine lactone (C4 HSL) albeit with different efficacy on C4 HSL. We used phenotypic analyses to characterize the specific impact of each lactonases on P. aeruginosa virulence. We further used molecular approaches for finely determine the impact of lactonases on gene regulation and protein expressions of P. aeruginosa. Findings: Although, both lactonases similarly impacted AHL-based circuits, strong variations were however observed in Pseudomonas Quinolone Signal regulation yielding in different impacts on phenotypic traits related to virulence, biofilm, pathogenicity or antibiotic susceptibility. Proteomic analysis further allowed to identify the specific impacts of lactonases on P. aeruginosa behavior. Interpretation: This global analysis provides the first evidence that QQ enzyme specificity is crucial to modulate QS-associated behavior in P. aeruginosa PA14 and will help to develop efficient quorum quenching strategies. Funding Statement: This work was supported by a project RAPID (LACTO-TEX) from Direction Generale de l'Armement (DGA, France), "Investissements d'avenir" program (Mediterranee Infection 10-IAHU-03) of the French Agence Nationale de la Recherche (ANR), "Emplois Jeunes Doctorants" program of Region Provence-Alpes-Cote d'Azur (PACA, France) and MnDrive initiative. Declaration of Interests: ME and EC have a patent WO2014167140 A1 licensed to Gene&GreenTK. LP, DD, BR, ME and EC report personal fees from Gene&GreenTK during the conduct of the study. The other authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Ethics Approval Statement: Not required.