The quorum sensing SinI/SinR-TraI/TraR systems promote Pb stabilization by Ensifer adhaerens S24 in the Pb-polluted aquatic environment.

In this study, the Pb-resistant Ensifer adhaerens strain S24, which contains quorum sensing (QS) systems responsible for N-acyl homoserine lactone (AHL) production, was investigated for QS system-mediated Pb stabilization and the underlying mechanisms. Whole-genome sequence analysis revealed the QS SinI/R and TraI/R systems in strain S24. Subsequently, strains S24 and the S24∆sinI/R, S24∆traI/R, S24∆traI/R/sinR, and S24∆sinI/R-traI/R/sinR mutants were constructed and compared for QS SinI/SinR-TraI/TraR system-mediated Pb stabilization in the solution and the mechanisms involved. After 5 days of incubation, strain S24 significantly decreased the Pb concentration in the Pb-contaminated solution compared with the mutants. The S24∆sinI/R-traI/R/sinR mutant exhibited reduced Pb stabilization and AHL activity than the other mutants. The S24∆sinI/R-traI/R/sinR mutant had significantly greater Pb concentrations in the solution and lower cell surface-adsorbed and extracellular precipitated Pb (PbS) contents as well as lower expression of H2S-producing genes of metC and sseA than did strain S24. Furthermore, the S24∆sinI/R-traI/R/sinR mutant displayed reduced interactions between the hydroxyl, amino, carboxyl, and ether groups and Pb, compared with strain S24. These findings implied the vital role of the SinI/SinR-TraI/TraR systems in strain S24 for Pb stabilization through enhanced cell surface adsorption and extracellular precipitation in Pb-polluted aquatic environments.

The quorum sensing SinI/R system contributes to cadmium immobilization in Ensifer adhaerens NER9 in the cadmium-contaminated solution.

In this study, the cadmium (Cd)-tolerant Ensifer adhaerens strain NER9 with quorum sensing (QS) systems (responsible for N-acyl homoserine lactone (AHL) production) was characterized for QS system-mediated Cd immobilization and the underlying mechanisms involved. Whole-genome sequence analysis revealed that strain NER9 contains the QS SinI/R and TraI/R systems. Strains NER9 and the NER9∆sinI/R, NER9∆traI/R, and NER9∆sinI/R-traI/R mutants were constructed and compared for QS SinI/R and TraI/R system-mediated Cd immobilization in the solution and the mechanisms involved. After 24 h of incubation, strain NER9 significantly decreased the Cd concentration in the Cd-contaminated solution compared with the NER9∆sinI/R, NER9∆traI/R, and NER9∆sinI/R-traI/R mutants. The NER9∆sinI/R mutant had a greater impact on Cd immobilization and a lower impact on the activities of AHLs than did the NER9∆traI/R mutant. The NER9∆sinI/R mutant had significantly greater Cd concentrations and lower cell wall- and exopolysaccharide (EPS)-adsorbed Cd contents than did strain NER9. Furthermore, the NER9∆sinI/R mutant presented a decrease in the number of functional groups interacting with Cd, compared with strain NER9. These results suggested that the SinI/R system in strain NER9 contributed to Cd immobilization by mediating cell wall- and EPS-adsorption in Cd-containing solution.

The Deciphering of Growth-Dependent Strategies for Quorum-Sensing Networks in Pseudomonas aeruginosa.

Pseudomonas aeruginosa is recognized as a significant cause of morbidity and mortality among nosocomial pathogens. In respiratory infections, P. aeruginosa acts not only as a single player but also collaborates with the opportunistic fungal pathogen Aspergillus fumigatus. This study introduced a QS molecule portfolio as a potential new biomarker that affects the secretion of virulence factors and biofilm formation. The quantitative levels of QS molecules, including 3-o-C12-HSL, 3-o-C8-HSL, C4-HSL, C6-HSL, HHQ, PQS, and PYO, measured using mass spectrometry in a monoculture, indicated metabolic changes during the transition from planktonic to sessile cells. In the co-cultures with A. fumigatus, the profile of abundant QS molecules was reduced to 3-o-C12-HSL, C4-HSL, PQS, and PYO. A decrease in C4-HSL by 50% to 170.6 ± 11.8 ng/mL and an increase 3-o-C12-HSL by 30% up to 784.4 ± 0.6 ng/mL were detected at the stage of the coverage of the hyphae with bacteria. Using scanning electron microscopy, we showed the morphological stages of the P. aeruginosa biofilm, such as cell aggregates, maturated biofilm, and cell dispersion. qPCR quantification of the genome equivalents of both microorganisms suggested that they exhibited an interplay strategy rather than antagonism. This is the first study demonstrating the quantitative growth-dependent appearance of QS molecule secretion in a monoculture of P. aeruginosa and a co-culture with A. fumigatus.

In-silico and in-vitro assessment of the antibiofilm potential of azo dye, carmoisine against Pseudomonas aeruginosa.

Biofilm is a community of microorganisms attached to the substrate and plays a significant role in microbial pathogenesis and medical device-related infection. Pseudomonas aeruginosa (PA) is a highly infectious gram-negative opportunistic biofilm-forming bacterium with high antibiotic resistance. Several reports underscore the antimicrobial activity of natural and synthetic food coloring agents, including carmoisine, turmeric dye, red amaranth dye, and phloxine B. However, their ability to suppress the PA biofilm is not clearly understood. Carmoisine is a red-colored synthetic azo dye containing naphthalene subunits and sulfonic groups and is widely used as a food coloring agent. This study investigated the antibiofilm potential and possible mechanism of biofilm inhibition by carmoisine against PA. Computational studies through molecular docking revealed that carmoisine strongly binds to QS regulator LasR (-12.7) and relatively less strongly but significantly with WspR (-6.9). Further analysis of the docked LasR-carmoisine complex using 100 ns MD simulation (Desmond, Schrödinger) validated the bonding strength and stability. Crystal violet assay, triphenyl tetrazolium chloride salt assay, and confocal microscopic studies were adopted for biofilm quantification, and the results indicated the dose-dependent antibiofilm activity of carmoisine against PA. We hypothesise that the carmoisine-mediated reduction of biofilm in PA is due to its interaction with LasR and interference with the QS system. The computational and biochemical analysis of another compound, 1,2-naphthoquinone-4-sulphonic acid, reiterated the role of the naphthalene ring in biofilm inhibition. Hence, this work will pave the way for the future discovery of antibiofilm drugs based on naphthalene ring-based lead compounds.Communicated by Ramaswamy H. Sarma.

Presence of quorum sensing system, virulence genes, biofilm formation and relationship among them and class 1 integron in carbapenem-resistant clinical Pseudomonas aeruginosa isolates.

Carbapenems are the most effective agents for treating clinical P. aeruginosa (PsA) infections. During an infection, a quorum-sensing (QS) system and its regulating virulence genes have a great role. The aim of the study was to detect the presence of a las and rhl QS system and related virulence genes, biofilm formation and a class 1 (Cls1) integron. A total of 52 carbapenem-resistant PsA (CRPsA) isolates obtained from Kastamonu, Turkey was analyzed. For the isolation and identification of CRPsA isolates, a conventional culture method, an automated VITEK-2 compact system, and oprL gene-based molecular technique were applied. The two QS system genes were detected in 51 (98.1%), and co-existed of four two QS system genes (lasI/R and rhIl/R genes) were determined in 41 (78.8%) of the isolates. algD, lasB, toxA and aprA genes were detected in between 46.1 and 88.5%, and co-existence of four two QS system genes with four virulence genes were detected in 40.4% of the isolates. Biofilm formation using microtiter plate assay and slime production using Congo Red Agar and Cls1 integron were determined in 84.6%, 67.3% and 51.9% of the isolates, respectively. According to statistical analyses results, there was a significant positive correlation (p < .10) between the las and the rhl systems and a strongly and positive correlation (p < .01 or p < .05) between the rhl system-three virulence genes and slime production-and among some virulence genes. In conclusion, the CRPsA isolates tested in the study are highly virulent and QS systems have a significant role in pathogenesis.

Genetic regulation, biosynthesis and applications of extracellular polysaccharides of the biofilm matrix of bacteria.

Bacterial biofilm formation is dependent mainly on the decision-making process of the two key factors of the gene regulatory network, namely the Quorum Sensing (QS) system and bis-(3'-5')-cyclic dimeric guanosine monophosphate (c-di-GMP). c-di-GMP is a secondary messenger molecule that enhances extracellular polysaccharides production by activating pelD and alg44. Genes involved in the metabolic pathway for the biosynthesis of extracellular polysaccharides are clustered within the genome of the producing bacteria. The extracellular polysaccharide gene cluster encodes specific regulatory enzymes and transporter proteins involved in the different steps of the biosynthesis route. The diversity of extracellular polysaccharides produced by the bacteria is synthesized via different biosynthesis pathways. Understanding the genetic regulation and biosynthesis of extracellular polysaccharides is crucial for tailor-made polymers via genetic, metabolic, and protein engineering approaches. This review illustrates structure, structure-function relationship, genetics, regulation, biosynthetic pathways, and various applications of extracellular polysaccharides.

Effects of ALA-PDT on biofilm structure, virulence factor secretion, and QS in Pseudomonas aeruginosa.

AIM: To investigate the effects of ALA-PDT on biofilm structure, virulence factor secretion, and quorum sensing (QS) in Pseudomonas aeruginosa. MATERIALS AND METHODS: We used confocal laser scanning microscopy (CLSM), an XTT assay, scanning electron microscopy (SEM), a virulence factor assay and qRT-PCR in this study. RESULTS: The XTT assay showed that ALA-PDT significantly inhibited the growth of planktonic P. aeruginosa. CLSM and SEM showed that ALA-PDT destroyed both bacterial and biofilm structures. The virulence factor assay showed that pyocyanin and elastase secretion were significantly inhibited in the ALA-PDT groups. qRT-PCR assays demonstrated that ALA-PDT significantly reduced the mRNA expression of QS-related genes. CONCLUSION: ALA-PDT kills planktonic and viable biofilm-associated P. aeruginosa cells, destroys biofilm structures, reduces virulence factor secretion and affects QS system gene expression.