Abstract
This study reported the efficacy of the metabolites of Plectosphaerella cucumerina, one phyllosphere fungus from Orychophragmus violaceus, against Pseudomonas aeruginosa quorum sensing (QS) and QS-regulated biofilms. The minimum inhibitory concentration (MIC) of the ethyl acetate (EtOAc) extract from P. cucumerina against P. aeruginosa PAO1 was 1.25 mg mL−1. At sub-MIC concentrations, P. cucumerina extract (0.25–1 mg mL−1) not only inhibited biofilm formation but also disrupted preformed biofilms of P. aeruginosa PAO1 without affecting its growth. Fluorescence and scanning electron microscope (SEM) showed architectural disruption of the biofilms when treated with P. cucumerina metabolites. Further investigation demonstrated that metabolites in P. cucumerina attenuated the QS-dependent virulence factors. LC-MS/MS spectra coupled with experimentally standard samples suggested that patulin and emodin might act as the principal components possessing anti-biofilm and antivirulence activities. This is the first report of (1) the isolation of P. cucumerina from the phyllosphere of O. violaceus and (2) anti-biofilm, antivirulence, and biofilm disruption activities of this fungus. Thus, this study provides fascinating new pathways for screening antipathogenic agents.
Highlights
Most pathogenic bacteria can form biofilms under diverse conditions (Hall-Stoodley and Stoodley, 2005)
The A. tumefaciens KYC55 generates the acylated L-homoserine lactones (AHLs) receptor TraR, which can sense exogenous AHLs. This anti-quorum sensing (QS) capacity was determined by comparing the competitive binding of the AHL molecules of A. tumefaciens and fungal extract to the AHL receptors
The results showed that emodin with the concentration of 50 μg mL−1 had no inhibitory effect on P. aeruginosa growth comparing with both the negative controls (Figure S7)
Summary
Most pathogenic bacteria can form biofilms under diverse conditions (Hall-Stoodley and Stoodley, 2005). Among biofilm forming microbial pathogens, Pseudomonas aeruginosa is the most notorious bacterium causing chronic diseases in nature (Morita et al, 2014). The pathogenicity of P. aeruginosa is mainly owing to the biofilms, which make this organism more resistant to physical and chemical treatment (Imperi et al, 2014; Pompilio et al, 2015). Biofilm formation is a highly regulated process that is closely associated with quorum sensing (QS) (Qin et al, 2014). QS is a bacterial communication phenomenon that relies on secreted signals for coordinating group behaviors (Kim et al, 2015). QS signals were directly employed by bacteria to control biofilm formation and production of virulence
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