| Objective Quorum sensing system?QSS? is one of the important signaling intermediate systems in Pseudomonas aeruginosa?PA?. In P. aeruginosa, the production of several virulence factors?pyocyanin, protease activity,elastase and rhamnolipid? and biofilm development are mainly regulated by QSS, and the induced self-regulation systems Las/Rhl dominate in QSS. Whether a plausible mechanism by which cardamonin results in inhibition of virulence production and biofilm formation is mediated by las R/rhl R gene expression needs to be illustrated. This study was to investigate the inhibitory effect of cardamonin on the expression of PA virulence factors and biofilm formation and its possible mechanism.Methods1 Bacterial culture The single colony of PA was activated and isolated by dilution-plate method, and then subcultivated in LB, MH, PTSB liquid culture media. Cultivation of PAO1 is0.5 Maxwell concentration(1×108 cfu·m L-1).2 Protocol Blank control group, vehicle group, Car with 0.5 % DMSO diluted into 32, 16, 8?g·m L-1, respectively, in selection time were measured by the optical density? OD?values of each samples.3 Measurements and methodology3.1 The effect of Car on the production of pyocyanin, protease activity, elastase and rhamnolipid of PA was evaluated by photoelectric turbidimetry.3.2 The BF was measured by plystyrene microliter plate assay using crystal violet staining.3.3 Expression of las R/rhl R gene were performed by quantitative real-time PCR.Results1 The growth of PA was inhibited by Car(64 ?g·m L-1, P<0.05); Car(32, 16, 8?g·m L-1) had no effect on the growth of PA; Car(32, 16, 8 ?g·m L-1) were selected to be the drug concentration for the subsequent assays.2 The production of pyocyanin was significantly inhibited by Car(32, 16, 8 ?g·m L-1);and the activities of protease, elastase and rhamnolipid were also inhibited by Car? P<0.05?.3 Different concentrations of Car could inhibit the biofilm formation of PA in vitro.4 The gene expression of lasR and rhlR gene were decreased by Car in a dose-dependent manner.Conclusion Car(32, 16, 8 ?g·m L-1) inhibited the virulence production of PA and biofilm formation of PA, which might be associated with the down-regulation of QS-related gene lasR, rhlR. |
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