ABSTRACT
Quorum sensing (QS)-mediated infections cause severe diseases in human beings. The control of infectious diseases by inhibiting QS using antipathogenic drugs is a promising approach as antibiotics are proving inefficient in treating these diseases. Marine fungal (Pestalotiopsis sydowiana PPR) extract was found to possess effective antipathogenic characteristics. The minimum inhibitory concentration (MIC) of the fungal extract against test pathogen Pseudomonas aeruginosa PAO1 was 1,000 µg/ml. Sub-MIC concentrations (250 and 500 µg/ml) of fungal extract reduced QS-regulated virulence phenotypes such as the production of pyocyanin, chitinase, protease, elastase, and staphylolytic activity in P. aeruginosa PAO1 by 84.15%, 73.15%, 67.37%, 62.37%, and 33.65%, respectively. Moreover, it also reduced the production of exopolysaccharides (74.99%), rhamnolipids (68.01%), and alginate (54.98%), and inhibited the biofilm formation of the bacteria by 90.54%. In silico analysis revealed that the metabolite of P. sydowiana PPR binds to the bacterial QS receptor proteins (LasR and RhlR) similar to their respective natural signaling molecules. Cyclo(-Leu-Pro) (CLP) and 4-Hydroxyphenylacetamide (4-HPA) were identified as potent bioactive compounds among the metabolites of P. sydowiana PPR using in silico approaches. The MIC values of CLP and 4-HPA against P. aeruginosa PAO1 were determined as 250 and 125 µg/ml, respectively. All the antivirulence assays were conducted at sub-MIC concentrations of CLP (125 µg/ml) and 4-HPA (62.5 µg/ml), which resulted in marked reduction in all the investigated virulence factors. This was further supported by gene expression studies. The findings suggest that the metabolites of P. sydowiana PPR can be employed as promising QS inhibitors that target pathogenic bacteria.
Subject(s)
Anti-Bacterial Agents/pharmacology , Pestalotiopsis/metabolism , Quorum Sensing/drug effects , Virulence Factors/metabolism , Anti-Bacterial Agents/chemistry , Anti-Bacterial Agents/metabolism , Bacterial Proteins/chemistry , Bacterial Proteins/genetics , Bacterial Proteins/metabolism , Biofilms/drug effects , Biofilms/growth & development , Gene Expression Regulation, Bacterial/drug effects , Microbial Sensitivity Tests , Molecular Docking Simulation , Molecular Dynamics Simulation , Pseudomonas aeruginosa/drug effects , Pseudomonas aeruginosa/pathogenicity , Pseudomonas aeruginosa/physiology , Virulence/drug effects , Virulence/genetics , Virulence Factors/geneticsABSTRACT
The bacterial cell communication also termed as Quorum sensing (QS) system was involved in the expression of several virulence traits during Pseudomonas infection. The attenuating of this bacterial cell communication system is an attractive approach for the management of bacterial infections without the complication of resistance development. In this respect, the marine environment has gained significant attention due to its biodiversity and as a source of novel bioactive compounds. The present study aimed to screening effective QS inhibitors from marine associated fungal species for QS inhibitors. Twelve morphologically distinct fungal isolates were isolated from the wood of Avicennia marina from marine ecosystem. The anti-QS potential of fungal crude extract from was investigated in biosensor strain and test bacterium, Chromobacterium violaceum and Pseudomonas aeruginosa PAO1, respectively. Promising anti-QS activity was observed in the crude extract of one of the fungal isolate and identified by molecular characterization using internal transcribed spacer (ITS) region as Blastobotrys parvus PPR3. The anti-virulence and antibiofilm effects of ethyl acetate fractions from PPR3 against P. aeruginosa PAO1 were evaluated. The fungal metabolites responsible for the anti-QS activity of fungal crude extract was identified using gas chromatography-mass spectrometry (GC-MS). Furthermore, molecular docking studies were performed to understand the interaction of bioactive compounds with as receptors of P. aeruginosa PAO1. The crude extract of PPR3 showed reduction in different virulence traits of P. aeruginosa PAO1 such as production of pyocyanin, elastase, protease, chitinase, swimming and swarming motility, biofilm formation, exopolysaccharide production and alginate production at different sub-MIC concentrations. Interaction of bioactive metabolites with LasR and RhlR receptors of P. aeruginosa PAO1 was reported. The findings of the present study suggested that metabolites of B. parvus PPR3 interfere with QS system of P. aeruginosa PAO1 and alters the production of virulence factors.
