Pseudomonas aeruginosa plays an important role in chronic lung infections among patients with cystic fibrosis (CF) through its ability to form antibiotic-resistant biofilms. In P. aeruginosa, biofilm development and the production of several virulence factors are mainly regulated by the rhl and las quorum-sensing (QS) systems, which are controlled by two N-acyl-homoserine lactone signal molecules. In a previous study, we discovered an original QS inhibitor, N-(2-pyrimidyl)butanamide, called C11, based on the structure of C 4 -homoserine lactone, and found that it is able to significantly inhibit P. aeruginosa biofilm formation. However, recent data indicate that P. aeruginosa grows under anaerobic conditions and forms biofilms in the lungs of CF patients that are denser and more robust than those formed under aerobic conditions. Our confocal microscopy observations of P. aeruginosa biofilms developed under aerobic and anaerobic conditions confirmed that the biofilms formed under these two conditions have radically different architectures. C11 showed significant dose-dependent antibiofilm activity on biofilms grown under both aerobic and anaerobic conditions, with a greater inhibitory effect being seen under conditions of anaerobiosis. Gene expression analyses performed by quantitative reverse transcriptase PCR showed that C11 led to the significant downregulation of rhl QS regulatory genes but also to the downregulation of both las QS regulatory genes and QS system-regulated virulence genes, rhlA and lasB. Furthermore, the activity of C11 in combination with antibiotics against P. aeruginosa biofilms was tested, and synergistic antibiofilm activity between C11 and ciprofloxacin, tobramycin, and colistin was obtained under both aerobic and anaerobic conditions. This study demonstrates that C11 may increase the efficacy of treatments for P. aeruginosa infections by increasing the susceptibility of biofilms to antibiotics and by attenuating the pathogenicity of the bacterium.

New insights into Legionella pneumophila biofilm regulation by c-di-GMP signaling.(2016) Biofouling, Open Archive TOULOUSE Archive Ouverte (OATAO) OATAO is an open access repository that collects the work of some Toulouse researchers and makes it freely available over the web where possible. This is an author's version published in : http://oatao.univ-toulouse.fr/19753Official URL : https://doi.org/10. 1080/08927014.2016.1212988 Any correspondence concerning this service should be sent to the repository administrator : tech-oatao@listes-diff.inp-toulouse.fr The waterborne pathogen Legionella pneumophila grows as a bio lm, freely or inside amoebae. Cyclic-di-GMP (c-di-GMP), a bacterial second messenger frequently implicated in bio lm formation, is synthesized and degraded by diguanylate cyclases (DGCs) and phosphodiesterases (PDEs), respectively. To characterize the c-di-GMP-metabolizing enzymes involved in L. pneumophila bio lm regulation, the consequences on bio lm formation and the c-di-GMP concentration of each corresponding gene inactivation were assessed in the Lens strain. The results showed that one DGC and two PDEs enhance di erent aspects of bio lm formation, while two proteins with dual activity (DGC/PDE) inhibit bio lm growth. Surprisingly, only two mutants exhibited a change in global c-di-GMP concentration. This study highlights that speci c c-di-GMP pathways control L. pneumophila bio lm formation, most likely via temporary and/or local modulation of c-di-GMP concentration. Furthermore, Lpl1054 DGC is required to enable the formation a dense bio lm in response to nitric oxide, a signal for bio lm dispersion in many other species. New insights into Legionella pneumophila bio lm regulation by c-di-GMP signaling