Quorum Sensing Signal Molecules Research Articles

Surfactin, a quorum sensing signal molecule, globally affects the carbon metabolism in Bacillus amyloliquefaciens

Surfactin, a quorum sensing signal molecule, is correlated with carbon metabolism in Bacillus amyloliquefaciens. In the present work, we found that mutation of srfA (ΔsrfA) led to an obviously changed carbon metabolism in B. amyloliquefaciens. Firstly, the PTS-glucose system was significantly increased as a feedback to glucose exhaustion. Secondly, the basic carbon metabolism such as glycolysis and TCA cycle was obviously weakened in ΔsrfA. Thirdly, the global regulator of CcpA (carbon catabolite protein A) and P ~ Ser46-HPr (seryl-phosphorylated form of histidine-containing protein) to mediate the CcpA-dependent CCR (carbon catabolite repression) were not increased, but the ability to use extracellular non- and less-preferred carbon sources was down-regulated in ΔsrfA. Fourthly, the carbon overflow metabolism such as biosynthesis of acetate was enhanced while biosynthesis of acetoin/2,3-butanediol and branched-chain amino acids were weakened in ΔsrfA. Finally, ΔsrfA could use most of non- and less-preferred carbon sources except for fatty acids, branched chain amino acids, and some organic acids (e.g. pyruvate, citrate and glutamate) after glucose exhaustion. Collectively, surfactin showed a global influence on carbon metabolism in B. amyloliquefaciens. Our studies highlighted a way to correlate quorum sensing with carbon metabolism via surfactin in Bacillus species.

N-Acyl-Homoserine Lactones May Affect the Gut Health of Low-Birth-Weight Piglets by Altering Intestinal Epithelial Cell Barrier Function and Amino Acid Metabolism.

In piglets, low birth weight (LBW) is associated with intestinal dysfunction, which affects their growth performance and causes economic losses. This study was designed to test whether microbial quorum sensing (QS) affects LBW-induced intestinal developmental defects in piglets. Seven normal-birth-weight (NBW; 1.36±0.01 kg) and 7 LBW (0.89±0.01 kg) piglets were selected. Feces were collected from piglets on 2, 21, and 50 days of age for detection of the QS signaling molecules, N-acyl-homoserine lactones (AHLs), and microbiota analysis. The associations between 2 long-chain AHLs [N-3-oxo-dodecanoyl-l-homoserine lactone (3OC12-HSL) and N-3-oxo-tetradecanoyl-l-homoserine lactone (3OC14-HSL)] and the microbes were tested using Spearman correlation coefficients. The effect of 3OC12-HSL and 3OC14-HSL on intestinal porcine epithelial cell-jejunum 2 (IPEC-J2) cell viability was investigated by cholecystokinin octapeptide assay. Transcriptomic analysis was performed by RNA sequencing on cells treated with 3OC12-HSL. The concentrations of 3OC12-HSL and 3OC14-HSL in the feces of LBW piglets were higher than those in NBW piglets at age 50 d by 2.5- and 2.24-fold, respectively (P<0.05). The microbial α diversity (observed species, abundance-based coverage estimator, and Shannon index) of LBW piglets was 81-91% lower than that of NBW piglets (P<0.05). The relative abundance of Ruminococcaceae UCG-002/UCG-013 was 43.0% and 30.0% lower, respectively, in feces from LBW compared with NBW piglets (P<0.05). 3OC12-HSL and Ruminococcaceae UCG-002/UCG-005/UCG-010 abundance were negatively correlated (ρ ≤ -0.58). Treatment with 400 μM 3OC12-HSL markedly reduced IPEC-J2 cell viability by 47.5%. Transcriptomic data showed that 3OC12-HSL mainly changed the "import across plasma membrane" and "arginine and proline metabolism" of IPEC-J2 cells. 3OC12-HSL is a QS signaling molecule with an ability to impair gut health of LBW piglets. This finding adds to our understanding of the mechanisms responsible for gut injury in LBW piglets.

A single point mutation converts a glutaryl-7-aminocephalosporanic acid acylase into an N-acyl-homoserine lactone acylase

ObjectiveTo change the specificity of a glutaryl-7-aminocephalosporanic acid acylase (GCA) towards N-acyl homoserine lactones (AHLs; quorum sensing signalling molecules) by site-directed mutagenesis.ResultsSeven residues were identified by analysis of existing crystal structures as potential determinants of substrate specificity. Site-saturation mutagenesis libraries were created for each of the seven selected positions. High-throughput activity screening of each library identified two variants—Arg255Ala, Arg255Gly—with new activities towards N-acyl homoserine lactone substrates. Structural modelling of the Arg255Gly mutation suggests that the smaller side-chain of glycine (as compared to arginine in the wild-type enzyme) avoids a key clash with the acyl group of the N-acyl homoserine lactone substrate.ConclusionsMutation of a single amino acid residue successfully converted a GCA (with no detectable activity against AHLs) into an AHL acylase. This approach may be useful for further engineering of ‘quorum quenching’ enzymes.

Biotransformation of Perrottetin F by Aspergillus niger: New Bioactive Secondary Metabolites

Biotransformation of bis-bibenzyl perrottetin F (1), isolated from the liverwort Lunularia cruciata by Aspergillus niger, has been investigated. New metabolites (2-4) have been isolated using reversed phase semipreparative HPLC and their structures were established to be 8-hydroxyperrottetin F, C-7-C-8 cleaved product, and perrottetin F 6’-sulfate using 1D and 2D NMR, HR-ESI-MS, IR and UV spectroscopy. The antimicrobial and cytotoxic properties of these compounds were also evaluated. Given the suggested cytotoxic properties of the parent compound, antiproliferative activity against healthy human lung fibroblasts (MRC5) and human lung carcinoma (A549) of three metabolites were evaluated revealing their lower cytotoxic properties in comparison to the starting compound - perrottetin F. The antimicrobial properties of these compounds were also evaluated, with the inhibitory activity against the Pseudomonas aeruginosa PAO1 and Staphylococcus aureus determined between 100 µM and 450 µM. The metabolites showed remarkable ability to inhibit synthesis of bacterial quorum-sensing signal molecules such as short chain acyl homoserine lactones (AHLs). Therefore, biotransformation method represents fast and effective tool for obtaining new bioactive structures.

Photocatalytic quorum quenching: A new antifouling and in-situ membrane cleaning strategy for an external membrane bioreactor coupled to UASB

Microbial quorum sensing (QS) induces biofilm formation on the membrane surfaces leading to severe biofouling, which remains a major bottleneck for membrane-based systems. Here, we report an effective UV photocatalytic quorum quenching (QQ) strategy in an integrated upflow anaerobic sludge blanket – photocatalytic membrane reactor (UASB-PMR) system, where TiO2 nanoparticles immobilized in porous polymeric beads were kept in suspension as the photocatalysts. The UASB unit reached a methane yield of 0.30 ± 0.05 L CH4/g COD removal while treating the synthetic wastewater, slightly higher than a typical internal anaerobic membrane bioreactor (AnMBR). This novel system showed 7-fold higher efficacy in membrane fouling control than the UV photolytic QQ system (19.1 ± 2.4 d vs. 2.7 ± 1.0 d) under intermittent UV irradiation (17% of total operation time). Continuous UV irradiation, both in photolytic and photocatalytic QQ, significantly alleviated membrane biofouling, while long-term UV exposure exerted some changes in the surface properties of the membranes, which were not observed under intermittent UV irradiation. The reactive oxygen species (ROS) generated by the UV-excited TiO2 not only oxidized the foulants on the membrane surface, but also quenched acyl-homoserine lactones (AHLs), the QS signal molecules, thus retarding membrane fouling to the maximum extent. Additionally, in-situ membrane cleaning, enhanced COD removal, and almost complete disinfection of the effluent were realized in the photocatalytic QQ system. Equipped with these advantages, this innovative photocatalytic QQ can be a readily implementable strategy to prevent fouling in external membrane bioreactors (MBRs) for the pilot- and/or full-scale applications.

Regulation of Plant Mineral Nutrition by Signal Molecules.

Microbes operate their metabolic activities at a unicellular level. However, it has been revealed that a few metabolic activities only prove beneficial to microbes if operated at high cell densities. These cell density-dependent activities termed quorum sensing (QS) operate through specific chemical signals. In Gram-negative bacteria, the most widely reported QS signals are acylhomoserine lactones. In contrast, a novel QS-like system has been elucidated, regulating communication between microbes and plants through strigolactones. These systems regulate bioprocesses, which affect the health of plants, animals, and human beings. This mini-review presents recent developments in the QS and QS-like signal molecules in promoting plant health.

(+)-Terpinen-4-ol Inhibits Bacillus cereus Biofilm Formation by Upregulating the Interspecies Quorum Sensing Signals Diketopiperazines and Diffusing Signaling Factors.

Bacillus cereus is a Gram-positive endospore-forming foodborne pathogen that causes lethal food poisoning and significant economic losses, usually through biofilm- and endospore-induced recurrent cross- and postprocessing contamination. Due to the lack of critical inhibitory targets and control strategies, B. cereus biofilm contamination is a problem that urgently needs a solution. In this study, the antibacterial and antibiofilm activities of several natural potential bacterial quorum sensing (QS) interferers, a group of spice-originated monoterpenoids, were screened, and terpinen-4-ol effectively inhibited B. cereus growth and biofilm and spore germination with minimum growth inhibition and 50% biofilm inhibitory concentrations of 8 and 2 μmol/mL, respectively. FESEM/CLSM and phenotypic research illustrated that in addition to a decrease in the number of attached B. cereus cells, (+)-terpinen-4-ol also obviously reduced extracellular matrix synthesis, especially exopolysaccharides, and inhibited the swarming motility and protease activity of B. cereus. (+)-Terpinen-4-ol did not exert a significant effect on AI-2 signals in B. cereus. Accordingly, the B. cereus-produced interspecies QS signals diffusing signal factors (DSFs, C8-C15) and diketopiperazines (DKPs) were detected and identified here, which suppressed B. cereus biofilm formation in a concentration-dependent manner. (+)-Terpinen-4-ol significantly increased the levels of specific DSF and DKP signals in B. cereus and down-regulated the gene expression of some rpfB homologues in transcription level. Moreover, both DKPs and DSFs inhibited swarming motility and protease activity in B. cereus, while just the DSF signals 2-dodecenoic acid and 11-methyl-2-dodecenoic acid inhibited exopolysaccharide synthesis like (+)-terpinen-4-ol. In summary, B. cereus strains were found to produce nine DSF- and six DKP-type QS signaling molecules, which repressed B. cereus biofilm formation. (+)-Terpinen-4-ol was confirmed to be a promising antibacterial and antibiofilm agent against B. cereus upregulating DSFs and DKPs levels, and it could target the critical genes rpfB for DSFs turnover.

N-(3-oxododecanoyl)-homoserine lactone disrupts intestinal barrier and induces systemic inflammation through perturbing gut microbiome in mice.

As a quorum sensing signal molecule, N-(3-oxododecanoyl)-homoserine lactone (3OC12) regulate the population behavior of microorganisms. Many studies have proved that 3OC12 harm the physiological function of host intestinal epithelial cells. However, the detrimental effects of 3OC12 on intestinal health need verification in animals. Besides, the role of gut microbiome in 3OC12-induced intestinal damage also needs further understanding. In our study, 3OC12 was first administered to specific pathogen-free (SPF) mice, then the fecal microbiome of SPF mice was transplanted into germ-free (GF) mice to reveal the effects of 3OC12 on intestinal health and regulatory mechanisms of the intestinal microbiome. 3OC12 treatment significantly decreased body weight, shortened colonic length, disrupted the morphology of the colonic epithelium and increased the histopathological score of the colon in SPF mice. The levels of diamine peroxidase, d-lactate, TNF-α, IL-1β, and IL-8 were found to be significantly elevated in the serum of 3OC12 mice, while the levels of IL-10 were significantly reduced. Besides, the fecal microbial community of mice was also altered in the 3OC12-treated SPF mice. The results of fecal microbial transplantation (FMT) experiment showed that the phenotypes in SPF mice were almost reproduced in GF mice, manifested by body weight loss, colon damage and changed in serum chemical markers. More importantly, a joint analysis of fecal microbes in SPF and GF mice revealed Feature14_Elizabethkingia spp. was common differential bacteria in the feces of two kinds of mice treated with and without FMT. Our results demonstrated that 3OC12 challenge led to systemic inflammation and body weight loss in mice by disrupting intestinal barrier function, in which gut microbiome played a key role. These findings increased our understanding of the mechanism of intestinal injury caused by 3CO12, providing new ideas for the prevention and therapy of diseases caused by bacterial infection from the perspective of intestinal microbiome.

An innovative role for luteolin as a natural quorum sensing inhibitor in Pseudomonas aeruginosa

AimsThe emergence of antibiotic tolerance was a tricky problem in the treatment of chronic Pseudomonas aeruginosa-infected cystic fibrosis and burn victims. The quorum sensing (QS) inhibitor may serve as a new tactic for the bacterial resistance by inhibiting the biofilm formation and the production of virulence factors. This study explored the potential of luteolin as a QS inhibitor against P. aeruginosa and the molecular mechanism involved. Main methodsCrystal violet staining, CLSM observation, and SEM analysis were carried out to assess the effect of luteolin on biofilm formation. The motility assays and the production of virulence factors were determined to evaluate the QS-inhibitory activity of luteolin. Acyl-homoserine lactone, RT-PCR, and molecular docking assays were conducted to explain its anti-QS mechanisms. Key findingsThe biofilm formation, the production of virulence factors, and the motility of P. aeruginosa could be efficiently inhibited by luteolin. Luteolin could also attenuate the accumulation of the QS-signaling molecules N-(3-oxododecanoyl)-L-homoserine lactone (OdDHL) and N-butanoyl-L-homoserine lactone (BHL) (P < 0.01) and downregulate the transcription levels of QS genes (lasR, lasI, rhlR, and rhlI) (P < 0.01). Molecular docking analysis indicated that luteolin had a greater docking affinity with LasR regulator protein compared with OdDHL. SignificanceThis study is important as it reports the molecular mechanisms involved in the anti-biofilm formation activity of luteolin against P. aeruginosa. This study also indicated that luteolin could be helpful when used for the treatment of clinical drug-resistant infections of P. aeruginosa.

A Whole-Cell Biosensor for Point-of-Care Detection of Waterborne Bacterial Pathogens.

Water contamination by pathogenic bacteria is a major public health concern globally. Monitoring bacterial contamination in water is critically important to protect human health, but this remains a critical challenge. Engineered whole-cell biosensors created through synthetic biology hold great promise for rapid and cost-effective detection of waterborne pathogens. In this study, we created a novel whole-cell biosensor to detect water contamination by Pseudomonas aeruginosa and Burkholderia pseudomallei, which are two critical bacterial pathogens and are recognized as common causative agents for waterborne diseases. The biosensor detects the target bacterial pathogens by responding to the relevant quorum sensing signal molecules. Particularly, this study constructed and characterized the biosensor on the basis of the QscR quorum sensing signal system for the first time. We first designed and constructed a QscR on the basis of the sensing module in the E.coli host cell and integrated the QscR sensing module with a reporting module that expressed an enhanced green fluorescent protein (EGFP). The results demonstrated that the biosensor had high sensitivity in response to the quorum sensing signals of the target bacterial pathogens. We further engineered a biosensor that expressed a red pigment lycopene in the reporting module to produce a visible signal readout for the pathogen detection. Additionally, we investigated the feasibility of a paper-based assay by immobilizing the lycopene-based whole-cell biosensor on paper with the aim to build a prototype for developing portable detection devices. The biosensor would provide a simple and inexpensive alternative for timely and point-of-care detection of water contamination and protect human health.

Profiling of antimicrobial metabolites of plant growth promoting Pseudomonas spp. isolated from different plant hosts.

The online version contains supplementary material available at 10.1007/s13205-020-02585-8.

AI-2 represses CagA expression and bacterial adhesion, attenuating the Helicobacter pylori-induced inflammatory response of gastric epithelial cells.

Helicobacter pylori (H. pylori) infection of gastric epithelial cells induces inflammatory response. Outer membrane proteins (OMPs), Type 4 secretion system (T4SS) encoded by cagPAI, and the effector protein CagA are involved in the pathogenesis of H. pylori. H. pylori possesses a gene encoding LuxS which synthesizes AI-2, a quorum sensing signal molecule. The aim of this study was to investigate the role of AI-2 in the expression of virulence factors and the inflammatory response of gastric epithelial (AGS) cells induced by H. pylori. H. pylori ΔluxS mutant was constructed, and AI-2 activity was measured with Vibrio harveyi BB170. NF-κB activation, IL-8 production, expression of OMPs (outer membrane proteins), CagA, and T4SS encoded by cagPAI were investigated in H. pylori wild type, and ΔluxS with or without supplementation of AI-2. H. pylori produced approximately 7μM of AI-2 in the medium. AI-2 inhibited expression and translocation of CagA after infection of AGS cells. AI-2 upregulated the expression of CagM, CagE, and CagX, while had no effect to the interaction between T4SS and α5β1 integrin. AI-2 also reduced expression of adhesins and bacterial adhesion to AGS cells. Finally, AI-2 reduced the activation of NF-κB and expression of IL-8 in H. pylori-infected AGS. AI-2 plays an important role in the pathogenesis of H. pylori. AI-2 inhibits the bacterial adhesion, expression, and translocation of CagA, and attenuates the inflammatory response of AGS cells induced by H. pylori.

Quorum alleviating Molecules- A Review

The hindrance of quorum sensing is generally indicated to as quorum quenching. A few compounds have been combined to intrude on quorum sensing articulation by echoing AHL particles, N-acyl-3-amino-5H furanone, a synthetic analogue of N-AHL viably keeps the receipt of signal atom by obstructing its receptor Lux R protein. AHL controlled quorum sensing can be distressed by various methods, for example, lessening the movement of AHL cognate receptor protein or AHL synthase, hindering the creation of QS signal molecules, degradation of the AHL, and mimicking the signal atoms by utilizing their synthetic analogs. Additionally, obstruction of sensing signal transduction can be accomplished by utilizing an opponent particle equipped for contending or meddling with the local AHL motion for endorsed entry to the LUXR-type receptor. Competitive inhibitors are basically like the local AHL signal and can bind to and involve the AHL restricting site yet will fail to enact the LuxR-type receptor. The non-competitive inhibitors indicate almost no basic similarity to AHL signals and these particles bind to various locales on the receptor protein. A variety of natural Quorum quenching molecules have been identified.

Targeted and untargeted quantification of quorum sensing signalling molecules in bacterial cultures and biological samples via HPLC-TQ MS techniques

Quorum sensing (QS) is the ability of some bacteria to detect and to respond to population density through signalling molecules. QS molecules are involved in motility and cell aggregation mechanisms in diseases such as sepsis. Few biomarkers are currently available to diagnose sepsis, especially in high-risk conditions. The aim of this study was the development of new analytical methods based on liquid chromatography-mass spectrometry for the detection and quantification of QS signalling molecules, including N-acyl homoserine lactones (AHL) and hydroxyquinolones (HQ), in biofluids. Biological samples used in the study were Pseudomonas aeruginosa bacterial cultures and plasma from patients with sepsis. We developed two MS analytical methods, based on neutral loss (NL) and product ion (PI) experiments, to identify and characterize unknown AHL and HQ molecules. We then established a multiple-reaction-monitoring (MRM) method to quantify specific QS compounds. We validated the HPLC-MS-based approaches (MRM-NL-PI), and data were in accord with the validation guidelines. With the NL and PI MS-based methods, we identified and characterized 3 and 13 unknown AHL and HQ compounds, respectively, in biological samples. One of the newly found AHL molecules was C12-AHL, first quantified in Pseudomonas aeruginosa bacterial cultures. The MRM quantitation of analytes in plasma from patients with sepsis confirmed the analytical ability of MRM for the quantification of virulence factors during sepsis.Graphical abstract

Influence of Pseudomonas autoinducer N-3-oxododecanoyl homoserine lactone on human corneal epithelial cells.

The quorum-sensing (QS) signaling-dependent extracellular virulence factors of Pseudomonas aeruginosa can cause infections such as P. aeruginosa keratitis. P. aeruginosa communicates by secreting and sensing small chemical molecules called autoinducers in QS system. The key QS signal molecule, N-3-oxododecanoyl-homoserine lactone (3OC12HSL), can affect the behavior of host cells and initiate immune response. In this report we investigated the influence of 3OC12HSL on human corneal epithelial cells (HCECs) and the mechanisms of 3OC12HSL on activated toll-like receptor 2 (TLR2)-dependent interleukin-8 (IL-8) secretion in HCECs. Cells were cultured under different concentrations of 3OC12HSL. Cell viability was assessed using Crystal violet staining and the cell counting kit-8 assay. We demonstrated the administration of 3OC12HSL decreased HCEC viability and survival in a concentration- and time-dependent manner. At high concentrations, 3OC12HSL rapidly promoted a time-dependent increase in the expressions of TLR2 and TLR4. It was found that the nuclear translocation and expression of nuclear factor-κB (NF-κB) were also increased in response to 3OC12HSL treatment. The significantly elevated expressions of TLR2, TLR4, and NF-κB, encouraged us to further test their mechanisms that cause inflammatory response. Among the inflammatory factors examined (IL-6, IL-8, IL-10, and TNF-α), we found that IL-8 was significantly increased after treatment with 3OC12HSL and its expression was inhibited when TLR2 was specifically blocked or silenced. These results indicated that the QS signaling molecule 3OC12HSL could be recognized by the host innate immune system in HCECs. This recognition then triggered an immune inflammatory response involving the activation of TLR2 and an increase in expression of IL-8. This crosstalk between 3OC12HSL and host immunity in HCECs contributes to the development and progression of P. aeruginosa keratitis.

The Evanescent GacS Signal.

The GacS histidine kinase is the membrane sensor of the major upstream two-component system of the regulatory Gac/Rsm signal transduction pathway. This pathway governs the expression of a wide range of genes in pseudomonads and controls bacterial fitness and motility, tolerance to stress, biofilm formation, and virulence or plant protection. Despite the importance of these roles, the ligands binding to the sensor domain of GacS remain unknown, and their identification is an exciting challenge in this domain. At high population densities, the GacS signal triggers a switch from primary to secondary metabolism and a change in bacterial lifestyle. It has been suggested, based on these observations, that the GacS signal is a marker of the emergence of nutritional stress and competition. Biochemical investigations have yet to characterize the GacS signal fully. However, they portray this cue as a low-molecular weight, relatively simple and moderately apolar metabolite possibly resembling, but nevertheless different, from the aliphatic organic acids acting as quorum-sensing signaling molecules in other Proteobacteria. Significant progress in the development of metabolomic tools and new databases dedicated to Pseudomonas metabolism should help to unlock some of the last remaining secrets of GacS induction, making it possible to control the Gac/Rsm pathway.

Micro-rheological properties of lung homogenates correlate with infection severity in a mouse model of Pseudomonas aeruginosa lung infection

Lung infections caused by Pseudomonas aeruginosa pose a serious threat to patients suffering from, among others, cystic fibrosis, chronic obstructive pulmonary disease, or bronchiectasis, often leading to life-threatening complications. The establishment of a chronic infection is substantially related to communication between bacteria via quorum-sensing networks. In this study, we aimed to assess the role of quorum-sensing signaling molecules of the Pseudomonas quinolone signal (PQS) and to investigate the viscoelastic properties of lung tissue homogenates of PA-infected mice in a prolonged acute murine infection model. Therefore, a murine infection model was successfully established via intra-tracheal infection with alginate-supplemented Pseudomonas aeruginosa NH57388A. Rheological properties of lung homogenates were analyzed with multiple particle tracking (MPT) and quorum-sensing molecules were quantified with LC–MS/MS. Statistical analysis of bacterial load and quorum-sensing molecules showed a strong correlation between these biomarkers in infected lungs. This was accompanied by noticeable changes in the consistency of lung homogenates with increasing infection severity. Furthermore, viscoelastic properties of the lung homogenates strongly correlated with bacterial load and quorum sensing molecules. Considering the strong correlation between the viscoelasticity of lung homogenates and the aforementioned biomarkers, the viscoelastic properties of infected lungs might serve as reliable new biomarker for the evaluation of the severity of P. aeruginosa infections in murine models.

Effect of Sub-Minimum Inhibitory Concentrations of Tyrosol and EDTA on Quorum Sensing and Virulence of Pseudomonas aeruginosa.

IntroductionPseudomonas aeruginosa is considered a dangerous pathogen, as it causes many human diseases, besides that it is resistant to almost all types of antibacterial agents. So, new strategies to overcome P. aeruginosa infection have evolved to attenuate its virulence factors and inhibit its quorum-sensing (QS) activity.PurposeThis study investigated the effect of tyrosol and EDTA as anti-quorum-sensing and antivirulence agents against P. aeruginosa PAO1.MethodsAnti-quorum activity of sub-minimum inhibitory concentrations (sub-MICs) of tyrosol and EDTA was tested using Chromobacterium violaceum (CV 12,472) biosensor bioassay. Miller assay was used to assess the inhibition of QS signal molecules by β-galactosidase activity determination. Also, their effects on the production of protease, lipase, lecithinase, and motility were tested. The inhibitory effects of these molecules on QS regulatory genes and exotoxins genes expression were evaluated by real-time PCR.ResultsTyrosol and EDTA at sub-MICs inhibited the production of violacein pigment. Both compounds inhibited QS molecules production and their associated virulence factors (protease, lipase, lecithinase, and motility) (P≤ 0.05). Besides, the expression levels of QS regulatory genes (lasI, lasR, rhƖI, rhIR, pqsA, and pqsR) and exotoxins genes (exoS and exoY) were significantly reduced (P≤ 0.05).ConclusionBoth tyrosol and EDTA can be used to fight P. aeruginosa infection as anti-quorum-sensing and antivirulence agents at their sub-MICs.

Evaluation of quorum-sensing inhibitory effects of extracts of three traditional medicine plants with known antibacterial properties.

Today an alternative approach to control bacterial infections is the use of natural and traditional plant compounds to interfere with their quorum-sensing (QS) systems. In this study, antibacterial and anti-QS sensing activity of Syzygium aromaticum, Dionysia revoluta Boiss. and Eucalyptus camaldulensis Dehnh. were evaluated. These plants are local to the Middle East region and have since ancient times been used for their antibacterial activity. Plant compounds were extracted with n-hexane, methanol and 96% ethanol mixed solvent. Antibacterial activity of this herbal extracts against five Gram-negative and Gram-positive bacteria were assessed. The effective sub–minimum inhibitory concentration (MIC) of this extract on bacterial QS systems were investigated by a violacein quantification assay in the Chromobacterium violaceum CV026 biosensor strain, inhibition of exogenously QS signal molecules in Aeromonas veronii bv. Sobria strain BC88 and Pseudomonas aeruginosa isolated from a patient with cystic fibrosis in vitro. Results found that Syzygium aromaticum 0.39 to 0.048 mg/mL, Dionysia revoluta Boiss. 3.1 to 0.39 mg/mL and E. camaldulensis 0.78 to 0.097 mg/mL showed anti-QS activities by reducing the violacein formation depletion of QS signals produced in A. veronii and P. aeruginosa at sub-MICs. Regarding the anti-QS effects of these herbal extracts, their effective components may be candidates for use in combating bacterial infections at sub-MICs.

Effects of exogenous bacterial quorum sensing signal molecule (messenger) N-hexanoyl-L-homoserine lactone (C6-HSL) on morphological and physiological responses of winter wheat under simulated acid rain

The paper is based on the results of the project № 0120U102936 “Development of innovative biotechnology for increasing the stability and productivity of cereals based on a complex of signaling molecules of plant and bacterial origin for environmental protection and restoration” (2020—2024) funded by the National Academy of Sciences of Ukraine.