Inhibition Of Quorum Sensing System Research Articles

Inhibition of Pseudomonas aeruginosa Biofilm Formation and Quorum Sensing System by Extracts of Prunus avium Stalk

Recently, misuse or overuse of antibiotics has led to the antibiotic resistance problem, a global healthcare problem. Most virulence factors and biofilm formation in Pseudomonas aeruginosa are controlled by quorum sensing (QS). The inhibition of QS system by inhibitor molecules has been suggested as a novel alternative antivirulence approach in which no need to kill the bacteria. In the present study, QS and biofilm inhibitory potentials of the methanol and acetone extracts of Prunus avium stalk against P. aeruginosa were evaluated. The extracts were tested at the concentrations of 240, 120, and 60 μg/ml. lasB-gfp, rhlA-gfp, pqsA-gfp biosensor strains and P. aeruginosa PAO1 were used to monitor QS and biofilm inhibition, respectively. Fluorescence and absorbance measurements were performed on Cytation 3 multimode microplate reader. QS inhibition ratios for las, rhl, and pqs systems and biofilm inhibition ratios of the acetone extracts were recorded as 70.43%, 47.25%, 76.31%, and 47.76% (±6,60) and of the methanol extracts as 74.96%, 40.10%, 71.89%, and 38.54% (±3,56) at a certain concentration of 240 μg/ml, respectively. As a result, anti-QS and anti-biofilm properties of acetone extracts were better than that of methanol extracts. Further investigations are needed to discover inhibitor compounds of P. avium and also their effects on human cells and then these compounds may be used in new drug discoveries.

Soil phyllosilicate and iron oxide inhibit the quorum sensing of Chromobacterium violaceum

Microorganisms respond to various adverse environmental conditions and regulate different physiological functions by secreting and sensing signal molecules through quorum sensing (QS) systems. Phyllosilicates and iron oxides present in soils and sediments may have substantial impact on bacterial activity and QS due to their unique reactivity and close association with microorganisms. This research explored the effect of goethite, montmorillonite and kaolinite (0.05–2g L−1) on the growth and QS of a bacterial model, Chromobacterium violaceum. The results showed that kaolinite and goethite caused cellular damage at low mineral concentrations. The capacity for violacein production and biofilm formation of C. violaceum were inhibited by the minerals in the order of kaolinite > goethite > montmorillonite. The possible underlying mechanisms for QS inhibition by different minerals were investigated. Specifically, kaolinite repressed QS function through downregulation the expression of signal molecules synthesis gene cvil. Goethite and montmorillonite interfered with QS by adsorption of extracellular signal molecules. This work provides a better understanding of the interactions between bacteria and minerals and proposed that the inhibition of QS system is an ignored mechanism for bacterial toxicity by phyllosilicates and iron oxides.

Quorum Sensing Inhibition: Current Advances of the Natural Antimicrobial Agents

The misuses of antimicrobials in infectious diseases have led to the progress of extensive resistance in the infectious organisms. The failure of accessible antimicrobials to control infections makes it essential to discover alternatives to currently existing drugs. Their connection to infectious diseases and their natural ability to increase antimicrobial resistance in microbes, has led to platforms for research focused on new techniques to control them. Pathogenicity in many bacteria is regulated by quorum sensing (QS). Inhibition of QS system may cause reduction of virulence and protect against bacterial infections. These bacteria rely on chemical communication (or QS) to coordinate activities necessary for their survival in groups by some course of action. Their dependence on QS has made those signaling systems within bacteria an attractive target for the design of new anti-infective agents. Compounds that can interrupt these processes are known as QS inhibitors. The QS is the key regulator of virulence in various bacteria. Various plant extracts and their chemical constituents exhibited their effects on bacterial virulence factors by inhibiting QS genes and QS-controlled factors and effects on bacterial growth. The anti-QS approach is a promising one in the fight against infections pathogens, thereby making the bacteria more susceptible to traditional antimicrobials. The QS inhibitors (QSI) may provide the newest weapon against infections involving drug-resistant bacterial strains. These QSIs come from a variety of sources and have a wide array of structures.

Effect of non-thermal plasma on AHL-dependent QS systems and biofilm formation in Pseudomonas aeruginosa: Difference between non-hospital and clinical isolates

Non-thermal plasma (NTP), generated by DC cometary discharge with a metallic grid at atmospheric pressure, was used to eradicate biofilm of Pseudomonas aeruginosa from titanium alloy Ti-6Al-4V carriers. The NTP exposure may reduce the ability of signal molecules to cause quorum sensing (QS) response in P. aeruginosa and as a result, affect the production of virulence factors including biofilm formation. Two groups of P. aeruginosa were compared, namely strains isolated from the environment (non-hospital) and clinical isolates from hospital environment. For the non-hospital strains, the inhibition of QS systems, mediated mainly by N-acyl-homoserine lactone (AHL) signals, and decrease of total biofilm biomass were observed after the NTP treatment. After 60 minutes of exposure, almost complete eradication of biofilm (54 - 98%) was achieved. Compared to that, the NTP effect on the AHL levels was more pronounced in clinical isolates of P. aeruginosa, but eradication of the biofilm was not achieved. We conclude that NTP affected the AHL-dependent QS systems (las and rhl), which does not necessarily have to result in the regulation of virulence in clinical isolates.

Responses of bacterial strains isolated from drinking water environments to N-acyl-L-homoserine lactones and their analogs during biofilm formation

Often as a result of biofilm formation, drinking water distribution systems (DWDS) are regularly faced with the problem of microbial contamination. Quorum sensing (QS) systems play a marked role in the regulation of microbial biofilm formation; thus, inhibition of QS systems may provide a promising approach to biofilm formation control in DWDS. In the present study, 22 bacterial strains were isolated from drinking water-related environments. The following properties of the strains were investigated: bacterial biofilm formation capacity, QS signal molecule N-acyl-L-homoserine lactones (AHLs) production ability, and responses to AHLs and AHL analogs, 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)- furanone (MX) and 2(5H)-furanone. Four AHLs were added to developed biofilms at dosages ranging from 0.1 nmol$L -1 to 100 nmol$L -1 . As a result, the biofilm growth of more than 1/4 of the isolates, which included AHL producers and non-producers, were significantly promoted. Further, the biofilm biomasses were closely associated with respective AHLs concentrations. These results provided evidence to support the idea that AHLs play a definitive role in biofilm formation in many of the studied bacteria. Meanwhile, two AHLs analogs demon- strated unexpectedly minimal negative effects on biofilm formation. This suggested that, in order to find an applicable QS inhibition approach for biofilm control in DWDS, the testing and analysis of more analogs is needed.