Quorum-sensing Molecules Research Articles

Bitter taste signaling in tracheal epithelial brush cells elicits innate immune responses to bacterial infection.

Constant exposure of the airways to inhaled pathogens requires efficient early immune responses protecting against infections. How bacteria on the epithelial surface are detected and first-line protective mechanisms are initiated are not well understood. We have recently shown that tracheal brush cells (BCs) express functional taste receptors. Here we report that bitter taste signaling in murine BCs induces neurogenic inflammation. We demonstrate that BC signaling stimulates adjacent sensory nerve endings in the trachea to release the neuropeptides CGRP and substance P that mediate plasma extravasation, neutrophil recruitment, and diapedesis. Moreover, we show that bitter tasting quorum-sensing molecules from Pseudomonas aeruginosa activate tracheal BCs. BC signaling depends on the key taste transduction gene Trpm5, triggers secretion of immune mediators, among them the most abundant member of the complement system, and is needed to combat P. aeruginosa infections. Our data provide functional insight into first-line defense mechanisms against bacterial infections of the lung.

Predicting quorum sensing peptides using stacked generalization ensemble with gradient boosting based feature selection.

Bacteria exist in natural environments for most of their life as complex, heterogeneous, and multicellular aggregates. Under these circumstances, critical cell functions are controlled by several signaling molecules known as quorum sensing (QS) molecules. In Gram-positive bacteria, peptides are deployed as QS molecules. The development of antibodies against such QS molecules has been identified as a promising therapeutic intervention for bacterial control. Hence, the identification of QS peptides has received considerable attention. Availability of a fast and reliable predictive model to effectively identify QS peptides can help the existing high throughput experiments. In this study, a stacked generalization ensemble model with Gradient Boosting Machine (GBM)-based feature selection, namely EnsembleQS was developed to predict QS peptides with high accuracy. On selected GBM features (791D), the EnsembleQS outperformed finely tuned baseline classifiers and demonstrated robust performance, indicating the superiority of the model. The accuracy of EnsembleQS is 4% higher than those resulting from ensemble model on hybrid dataset. When evaluating an independent data set of 40 QS peptides, the EnsembleQS model showed an accuracy of 93.4% with Matthew's Correlation Coefficient (MCC) and area under the ROC curve (AUC) values of 0.91 and 0.951, respectively. These results suggest that EnsembleQS will be a useful computational framework for predicting QS peptides and will efficiently support proteomics research. The source code and all datasets used in this study are publicly available at https://github.com/proteinexplorers/EnsembleQS .

Promoter Identification and Optimization for the Response of Lactobacillus plantarum WCFS1 to the Gram-Negative Pathogen-Associated Molecule N-3-Oxododecanoyl Homoserine Lactone.

Quorum sensing (QS) in bacteria has been well studied as a cellular communication phenomenon for decades. In recent years, such systems have been repurposed for the use of biosensors in both cellular and cell-free contexts as well as for inducible protein expression in nontraditional chassis organisms. Such biosensors are particularly intriguing when considering the association between the pathogenesis of some bacteria and their signaling intermediates. Considering this relationship and considering the recent demonstration of the species Lactobacillus plantarum WCFS1 as both a synthetic biology chassis and an organism capable of detecting a pathogen-associated QS molecule, we wanted to develop this organism as a QS sentinel. We used an approach combining techniques from both systems and synthetic biology to identify a number of native QS-response genes and to alter associated promoter activity to tune the output of L. plantarum cultures exposed to N-3-oxododecanoyl homoserine lactone. The resulting engineered QS sentinel reinforces the potential of modified lactic acid bacteria (LAB) for use in human-health-promoting applications and also demonstrates a simple rational workflow to engineer sentinel organisms to respond to any environmental or chemical stimuli.

N-3-Oxo-Octanoyl Homoserine Lactone Primes Plant Resistance Against Necrotrophic Pathogen Pectobacterium carotovorum by Coordinating Jasmonic Acid and Auxin-Signaling Pathways.

Many Gram-negative bacteria use small signal molecules, such as N-acyl-homoserine lactones (AHLs), to communicate with each other and coordinate their collective behaviors. Recently, increasing evidence has demonstrated that long-chained quorum-sensing signals play roles in priming defense responses in plants. Our previous work indicated that a short-chained signal, N-3-oxo-octanoyl homoserine lactone (3OC8-HSL), enhanced Arabidopsis resistance to the hemi-biotrophic bacteria Pseudomonas syringae pv. tomato DC3000 through priming the salicylic acid (SA) pathway. Here, we found that 3OC8-HSL could also prime resistance to the necrotrophic bacterium Pectobacterium carotovorum ssp. carotovorum (Pcc) through the jasmonic acid (JA) pathway, and is dependent on auxin responses, in both Chinese cabbage and Arabidopsis. The subsequent Pcc invasion triggered JA accumulation and increased the down-stream genes’ expressions of JA synthesis genes (LOX, AOS, and AOC) and JA response genes (PDF1.2 and VSP2). The primed state was not observed in the Arabidopsis coi1-1 and jar1-1 mutants, which indicated that the primed resistance to Pcc was dependent on the JA pathway. The 3OC8-HSL was not transmitted from roots to leaves and it induced indoleacetic acid (IAA) accumulation and the DR5 and SAUR auxin-responsive genes’ expressions in seedlings. When Arabidopsis and Chinese cabbage roots were pretreated with exogenous IAA (10 μM), the plants had activated the JA pathway and enhanced resistance to Pcc, which implied that the JA pathway was involved in AHL priming by coordinating with the auxin pathway. Our findings provide a new strategy for the prevention and control of soft rot in Chinese cabbage and provide theoretical support for the use of the quorum-sensing AHL signal molecule as a new elicitor.

3-oxo-C12:2-HSL, quorum sensing molecule from human intestinal microbiota, inhibits pro-inflammatory pathways in immune cells via bitter taste receptors.

In the gut ecosystem, microorganisms regulate group behaviour and interplay with the host via a molecular system called quorum sensing (QS). The QS molecule 3-oxo-C12:2-HSL, first identified in human gut microbiota, exerts anti-inflammatory effects and could play a role in inflammatory bowel diseases where dysbiosis has been described. Our aim was to identify which signalling pathways are involved in this effect. We observed that 3-oxo-C12:2-HSL decreases expression of pro-inflammatory cytokines such as Interleukine-1β (− 35%) and Tumor Necrosis Factor-α (TNFα) (− 40%) by stimulated immune RAW264.7 cells and decreased TNF secretion by stimulated PBMC in a dose-dependent manner, between 25 to 100 µM. Transcriptomic analysis of RAW264.7 cells exposed to 3-oxo-C12:2-HSL, in a pro-inflammatory context, highlighted JAK-STAT, NF-κB and TFN signalling pathways and we confirmed that 3-oxo-C12:2-HSL inhibited JAK1 and STAT1 phosphorylation. We also showed through a screening assay that 3-oxo-C12:2-HSL interacted with several human bitter taste receptors. Its anti-inflammatory effect involved TAS2R38 as shown by pharmacologic inhibition and led to an increase in intracellular calcium levels. We thus unravelled the involvement of several cellular pathways in the anti-inflammatory effects exerted by the QS molecule 3-oxo-C12:2-HSL.

Elucidation of the AI-2 communication system in the food-borne pathogen Campylobacter jejuni by whole-cell-based biosensor quantification

The food-borne pathogen Campylobacter jejuni produces autoinducer-2 (AI-2) as an interspecies signalling molecule. AI-2 can trigger enhanced colonisation and biofilm formation, and this poses a serious risk to public health. To date, this communication system of C. jejuni is only partially understood, as detection and quantification of such autoinducer signalling molecules in complex media is hard to achieve. We have developed a whole-cell Vibrioharveyi-based biosensor assay to accurately quantify and follow production of AI-2 by C. jejuni 81–176 in a defined growth medium and in a model food system. Several V. harveyi strains were tested, but the most sensitive bioluminescent response to C. jejuni AI-2 was achieved with V. harveyi MM30, likely due to its ability to self-amplify the response to AI-2. The AI-2 concentrations measured by this biosensor were confirmed using an independent analytical method, HPLC-FLD, which we introduced for Campylobacter analytics for the first time. The AI-2 concentration produced by C. jejuni 81–176 in the model food system was ∼5-fold that in the defined growth medium, at the same cell density. Together with the linear increments in AI-2 concentrations with cell density, this suggests that in C. jejuni, AI-2 represents a metabolic by-product rather than a true quorum-sensing molecule. This biosensor method is highly sensitive, as shown by the reduction in the limit of detection (by a factor of 100) compared to HPLC-FLD, and it enables quantification of AI-2 in complex matrices, such as food, which will help to improve the quality and safety of food production.

Making Sense of Quorum Sensing at the Intestinal Mucosal Interface.

The gut microbiome can produce metabolic products that exert diverse activities, including effects on the host. Short chain fatty acids and amino acid derivatives have been the focus of many studies, but given the high microbial density in the gastrointestinal tract, other bacterial products such as those released as part of quorum sensing are likely to play an important role for health and disease. In this review, we provide of an overview on quorum sensing (QS) in the gastrointestinal tract and summarise what is known regarding the role of QS molecules such as auto-inducing peptides (AIP) and acyl-homoserine lactones (AHL) from commensal, probiotic, and pathogenic bacteria in intestinal health and disease. QS regulates the expression of numerous genes including biofilm formation, bacteriocin and toxin secretion, and metabolism. QS has also been shown to play an important role in the bacteria–host interaction. We conclude that the mechanisms of action of QS at the intestinal neuro–immune interface need to be further investigated.

Yeast-Mycelial Dimorphism in Pichia pastoris SMD1168 Is Triggered by Nutritional and Environmental Factors

This study reports, for the first time, morphological transition from yeast-like to filamentous form, normally associated with pathogenicity/increased protein secretion, in Pichia pastoris SMD1168 strain. The response was recorded in response to nutritional and environmental cues. The factors affecting this switch were extracellular pH (under nitrogen starvation conditions), carbon and nitrogen source under nitrogen- and carbon-limiting conditions respectively. Under nitrogen-limiting conditions, addition of fructose and sucrose in the culture medium induced filamentous morphology in a segregated form whereas addition of galactose led to a mixture of yeast and the filamentous form of the cells. Under carbon-limiting conditions, isoleucine and proline forced a filamentous form whereas glycine, valine, alanine and phenylalanine promoted yeast-like morphology. Similar dimorphic shift was also displayed by a recombinant methanol slow utilizing (Muts) strain (SMD-GCSF Muts) producing human granulocyte colony-stimulating factor in response to change in the initial inoculum level. Analysis of the extracellular metabolome by GC-MS indicated that several amino acids (leucine, proline, tyrosine), carboxylic acids (phenylacetic-, propanoic acid), alcohols and butylamine were present at different levels in the culture broth of the two morphological forms. High accumulation of proline and butylamine was seen in the extracellular culture filtrate of the filamentous form of the yeast. Presence of quorum-sensing molecules (phenylethyl alcohol, dodecanol) suggested complex network of pathways involved in this morphological transition.

Distribution of TAS2R38 bitter taste receptor phenotype and haplotypes among COVID-19 patients.

Bitter taste receptor TAS2R38 is expressed in the respiratory tract and can respond to quorum-sensing molecules produced by pathogens, stimulating the release of nitric oxide, with biocidal activity. TAS2R38 presents two main high-frequency haplotypes: the “taster” PAV and the “non-taster” AVI. Individuals carrying the AVI allele could be at greater risk of infections, including SARS-CoV-2. The aim of this study was to assess the frequency of PAV and AVI alleles in COVID-19 patients with severe or non-severe symptoms compared to healthy subjects to further corroborate, or not, the hypothesis that the PAV allele may act as a protecting factor towards SARS-CoV-2 infection while the AVI one may represent a risk factor. After careful selection, 54 individuals were included in the study and underwent genetic analysis and PROP phenotype assessment. Our investigation could not point out at a significant relationship between single nucleotide polymorphisms responsible for PROP bitterness and presence/severity of SARS-CoV-2 infection, as previous studies suggested. Our results uncouple the direct genetic contribution of rs10246939, rs1726866 and rs713598 on COVID-19, calling for caution when proposing a treatment based on TAS2R38 phenotypes.

MO270: N-3-Oxododecanoyl Homoserine Lactone Inhibits Angiogenesis by Activating the Angiopoietin-Tie System in Human Endothelial Cells

Abstract BACKGROUND AND AIMS The dysregulation of the angiopoietin–Tie system is associated with the development of sepsis-associated endothelial dysfunction. Bacterial quorum-sensing molecules act as pathogen-associated molecular patterns; however, the effect of quorum-sensing molecules on the angiopoietin–Tie system remains uncertain. METHOD This study investigated the molecular mechanisms of endothelial dysfunction in human umbilical vein endothelial cells treated with N-3-oxododecanoyl homoserine lactone (3OC12-HSL) derived from Pseudomonas aeruginosa. RESULTS Treatment with 3OC12-HSL reduced cell viability in a dose-dependent manner. Moreover, 3OC12-HSL treatment impaired the ability of tube formation even at non-lethal concentrations. The patterns of mRNA expression regarding the angiopoietin-Tie axis were assessed and the increased mRNA expressions of angiopoietin-2, Foxo-1, Tie1, and VEGFR2 were found in the 3OC12-HSL-treated cells. Western blot revealed that treatment with 3OC12-HSL increased the relative expressions of agiopoietin-2 and Foxo-1 and decreased the expression of Tie2. The study further evaluated the expression of IQGAP1 and the expressions of IQGAP1 and Rac1 decreased in cells treated with 3OC12-HSL. In addition, coimmunoprecipitation studies showed that treatment with 3OC12-HSL decreased the association between IQGAP1 and Rac1 in endothelial cells. CONCLUSION 3OC12-HSL can impair endothelial angiogenesis via the activation of the angiopoietin-Tie pathway. In addition, it may induce the dissociation of IQGAP1 with Rac1. Adjuvant therapy for blocking the quorum-sensing systems can help preserve endothelial cell integrity and prevent organ failure in patients with sepsis.

Bio‐Imaging quorum sensing signal molecules in a soil‐mimic gel

Rhizosphere, the narrow region surrounding plant roots directly influenced by root exudates and the root associated microbiome, plays an important role in plant productivity and the rhizosphere is well known for stimulating microbial metabolic activities. How microbial communities interact to form stable, metabolically interconnected functional communities is an area of intense interest. The question remains on how microbially produced secreted molecules that function as intercellular communication signals shape the structure and function of microbial communities. Our goal is to detect and quantify signal molecules produced by microbes or plants in the root‐soil environment, spatially and temporarily. As a proof‐of‐concept, we are imaging diffusible extracellular microbial metabolites involved in a bacteria‐bacteria communication process called quorum‐sensing. Quorum‐sensing relies on the accumulation of high concentrations of signal molecules in the environment to control bacterial gene expression, influencing rhizosphere colonization and plant health. Local concentration of quorum sensing molecules are determined using aptamer based sensors. Aptamers that can specifically bind the desired signal molecules are selected through SELEX and immobilized on the surface of nano‐porous membranes. Binding of the signal molecules and aptamer covered surface results in changes in surface charge distribution and steric hinderance and thus modifying the transmembrane ionic transport. Changes in transmembrane impedance can be measured through electrochemical impedance spectroscopy methods to monitor local concentrations of signal molecules. Sensor responses were determined for different concentrations of signal molecules and results showed detection of C4‐HSL in a soil‐mimic solution with KD of 10 nM. We demonstrate that the quorum‐sensing signal molecule C4‐homoserine lactone and (C4‐HSL) can rapidly diffuse in a soil‐mimic gel, providing evidence for our use of a soil‐mimic for further aptasensor development and validation. The sensors were then inserted into soil mimic gel for monitoring C4‐HSL diffusion and the resulted impedance changes were used to determine the C4‐HSL concentration at different positions in the gel. Measurements of local C4‐HSL concentrations variation and numerical solution of diffusion equation were used to create 4D images of C4‐HSL molecule diffusion in the soil‐mimic gel.

Effect of luxS encoding a synthase of quorum-sensing signal molecule AI-2 of Vibrio vulnificus on mouse gut microbiome.

Autoinducer-2 (AI-2), a quorum-sensing signal molecule from the human pathogen Vibrio vulnificus, was assessed for its effect on the gut microbiome of mice. For this, we employed 16S rRNA sequencing to compare the gut microbiome of mice infected with either wild-type V. vulnificus or with the isotype ΔluxS that has a deletion in luxS which encodes the biosynthetic function of AI-2. The relative ratio of wild-type Vibrio species in the jejunum and ileum of mice infected with the wild type was significantly higher than that in mice infected with ΔluxS, suggesting that AI-2 plays an important role in the colonization of V. vulnificus in the small intestine. The bacterial composition in the gut of mice infected with ΔluxS comprises a higher proportion of Firmicutes, composed mainly of Lactobacillus, compared to the mice infected with wild-type cells. In the large intestine, Vibrio species were barely detected regardless of genetic background. Three Lactobacillus spp. isolated from fecal samples from mice infected with ΔluxS manifested significant antibacterial activities against V. vulnificus. Culture supernatants from these three species were dissolved by HPLC, and a substance in fractions showing inhibitory activity against V. vulnificus was determined to be lactic acid. Our results suggest that luxS in V. vulnificus affects not only the ability of the species to colonize the host gut but also its susceptibility to the growth-inhibiting activity of commensal bacteria including Lactobacillus. KEY POINTS: • Gut microbiomes of ΔluxS-infected and WT Vibrio-infected mice differed greatly. • Difference was most prominent in the jejunum and ileum compared to the duodenum or large intestine. • In the small and large intestines of mice, the relative proportions of Vibrio and Lactobacillus species showed a negative relationship. • Effector molecules produced by Lactobacillus in mouse gut inhibit Vibrio growth.

Biodiversity of N-acyl homoserine lactonase (aiiA) gene from Bacillus subtilis

Microorganisms rely on the benefit of using chemical signals called autoinducers (AIs) as a connection matter in term of population, this mechanism is known as quorum sensing (QS). Quorum sensing is responsible for formation of biofilm together with virulence in bacteria. The most known QS molecule is N-acyl homoserine lactones (AHLs). A lot of degrading enzymes including lactonases that open the AHL ring and acylases that breakdown its acyl side chain can degrade or inactivate AHL. Due to similarity in lactone ring structure among AHLs it is susceptible to most of lactonases. Bacillus species are among the most promising bacteria producing AHL-lactonase. The aim of the work is to identify and study the diversity of the AHL-Lactonase gene among different Bacillus subtilis as a promising Quorum Quenching (QQ) strategy to prevent bacterial infections and biofilm formation. The AHL-lactonase (aiiA) gene of 64 B. subtilis isolates was amplified and sequenced followed by multiple sequence alignment of the translated amino acid sequences, homology modeling and docking study. An expected PCR product of about 750 base pair was detected in 22 B. subtilis isolates, and the results revealed that the isolates' sequences showed identity ranged between 97.61% and 99.47% with those in the NCBI GenBank database with 100% query coverage and 0.0 E-value. In addition, the results revealed high level of identity between many aiiA gene sequences of our isolates as they were closely related to the same sequences to many sequences of the NCBI GenBank database. The alignment of the amino acid sequences from the 22 B. subtilis isolates indicated that 84.4% of the amino acid residues were conserved between the aligned sequences. Docking of the co-crystalized ligand to wildtype and H109Y mutated protein showed a significant reduction of docking score for the mutated protein. This result indicate that this mutation might affect recognition or at least kinetics of these enzymes and hence their roles in quorum-quenching.

Innovative Biofouling Control for Membrane Bioreactors in Cold Regions by Inducing Environmental Adaptation in Quorum-Quenching Bacteria.

Bacterial quorum quenching (QQ), whose mechanism involves the degradation of quorum-sensing signal molecules, is an effective strategy for controlling biofouling in membrane bioreactors (MBRs). However, MBRs operated at low temperatures, either due to cold climates or seasonal variations, exhibit severe deterioration in QQ efficiency. In this study, a modified culture method for Rhodococcus sp. BH4, a QQ bacterium, was developed to induce environmental adaptation in cold regions. BH4-L, which was prepared by the modified culture method, showed enhancement in QQ efficiency at low temperatures. The higher QQ efficiency obtained by employing BH4-L at 10 °C (compared with that obtained by employing BH4 at 10 °C) was attributed to the higher live/dead cell ratio in the BH4-L-entrapping beads. When BH4-L-entrapping beads were applied to lab-scale MBRs operated at low temperatures, membrane biofouling in MBRs at low temperatures was successfully mitigated because BH4-L could substantially reduce the concentration of signal molecules (N-acyl homoserine lactones) in the biocake. Employing BH4-L in QQ-MBRs could offer a novel solution to the problem of severe membrane biofouling in MBRs in cold regions.

Amino Acid-Derived Quorum Sensing Molecule Alanine on the Gastrointestinal Tract Tolerance of the Lactobacillus Strains in the Cocultured Fermentation Model.

ABSTRACTMore and more people are aware of the importance of intestinal flora to human health, and people are interested in the regulation of intestinal flora and its interaction with the host. The survival status of the probiotics in the gastrointestinal environment and the microbial interactions between the lactic acid bacteria have also received considerable attention. In this study, the gastrointestinal environment tolerance, adhesion ability, and biofilm formation of the Lactobacillus strain in the coculture system were explored through the real-time fluorescence-based quantitative PCR, UPLC-MS/MS metabolic profiling analysis, and Live/Dead BacLight cell staining methods. The results showed that the coculture system could promote the release of signal molecules autoinducer-2 and effectively protect the viability of the Lactobacillus acidophilus in the gastrointestinal environment. Meanwhile, amino acid-derived characteristic metabolite l-alanine (1%) could effectively enhance the communication of the cells in the complex fermentation model, which led to an increase in the tolerance ability of the L. acidophilus by 28% in the gastrointestinal-like environment.IMPORTANCE It was deduced from the study that amino acid-derived metabolites play an important role in cell communication in the gastrointestinal tract (GIT) environment, thus enhancing the communication of Lactobacillus strains in the complex fermentation model. Meanwhile, the viability of Lactobacillus acidophilus can be increased in the coculture system during the gastrointestinal stress environment treated with the amino acid-derived quorum sensing (QS) molecule l-alanine. It will shed some light on the application of amino acid-derived QS molecules in the fermentation stater industry.

Reduction in Pathogenicity in Yeast-like Fungi by Farnesol in Quail Model.

Simple SummaryDespite the discoveries of new therapeutic antimycotics, the development of drug resistance is still the main clinical challenge in the treatment of mycoses. Data on the presence of new phytopreparations, along with the direct fungicidal effects that interfere with the resistance of fungal pathogens located in the biofilm, are of great interest. The use of these compounds as monotherapies or in combination with known antimycotics may be an effective strategy for preventing and/or destroying Candida biofilms found on the surface of biomedical devices and in vivo. The action mechanisms of farnesol in fungi have yet to be fully understood, but they are complex and likely include several mechanisms such as growth inhibition and apoptosis promotion.Candida albicans was the first eukaryotic microorganism to exhibit quorum-sensing through the secretion of the sesquiterpene E, farnesol. This molecule is generated by dephosphorylation of farnesyl pyrophosphate in the mevalonate biosynthetic pathway in mammalian and yeast cells. Exogenous farnesol inhibits yeast-to-hyphal formation in a concentration- and time-dependent manner at the earliest stage of hyphal development. Much research has been devoted to studying the role of farnesol as an inhibitor of hyphal morphogenesis; however, little research has been published regarding the in vivo impacts of farnesol on fungal virulence and the development of Candida infection. While other studies have examined the impact of multiple doses of farnesol in addition to antimycotics, we hypothesize that C. albicans treated with a single dose of this quorum-sensing molecule could reduce fungal virulence in a quail model.

Knocking-out ARO80 promotes the intracellular ROS accumulation through weakening MAPK pathway of Saccharomyces cerevisiae

Previous works suggested a relationship between quorum sensing (QS) and reactive oxygen species (ROS)-related metabolisms in Saccharomyces cerevisiae, where ARO80 has been identified as the key gene regulating the QS. To clarify the effect of QS on ROS-related metabolisms and oxidative tolerance in yeast cells, we generated an ARO80 knockout (ΔARO80) strain of S. cerevisiae S288C. Deletion of ARO80 promoted ROS accumulation but decreased the oxidative tolerance of S. cerevisiae, while QS molecules (QSMs) reversed such changes. Transcriptomics analysis indicated 79 up-regulated and 55 down-regulated genes in the ΔARO80 strain compared to the wild-type strain. Based on our transcriptomics analysis and previous findings, the RCK1 was screened out as a target gene to be clarified. The ΔRCK1 strain exhibited higher ROS content but showed lower oxidative tolerance than the wild-type strain, suggesting a function in ARO80 deletion-associated regulation on ROS-related metabolism of S. cerevisiae by regulating the MAPK pathway.

Fighting Acinetobacter baumannii infections with the acylase PvdQ

Acinetobacter baumannii is an opportunistic Gram-negative bacterial pathogen that poses a threat for frail patients worldwide. The high ability to withstand environmental stresses as well as its resistance towards a broad range of antibiotics make A. baumannii an effective hard-to-eradicate pathogen. One of the key mechanisms mediating tolerance against antibiotic treatment is the formation of biofilms, a process that is controlled by a multitude of different regulatory mechanisms. A key factor with major impact on biofilm formation is cell-to-cell communication by quorum-sensing, which in A. baumannii is mediated by acyl homoserine lactone signaling molecules. Here we show that the Ntn-Hydrolase PvdQ from Pseudomonas aeruginosa can reduce biofilm formation by the A. baumannii ATCC 17978 type strain and several clinical isolates on abiotic surfaces. Further, our study shows that a combination treatment of PvdQ-mediated quorum-quenching with the antibiotic gentamicin has a synergistic effect on the clearance of A. baumannii biofilms and possible biofilm dispersal. Moreover, we demonstrate in a Galleria mellonella larval infection model that PvdQ administration significantly prolongs survival of the larvae. Altogether, we conclude that the acylase-mediated irreversible cleavage of quorum-sensing signaling molecules as exemplified with PvdQ can set a profound limit to the progression of A. baumannii infections.

Intestinal Infection of Candida albicans: Preventing the Formation of Biofilm by C. albicans and Protecting the Intestinal Epithelial Barrier.

The large mortality and morbidity rate of C. albicans infections is a crucial problem in medical mycology. Because the generation of biofilms and drug resistance are growing concerns, the growth of novel antifungal agents and the looking for newer objectives are necessary. In this review, inhibitors of C. albicans biofilm generation and molecular mechanisms of intestinal epithelial barrier protection are elucidated. Recent studies on various transcription elements; quorum-sensing molecules; host responses to adherence; and changes in efflux pumps, enzymes, bud to hyphal transition, and lipid profiles have increased the knowledge of the intricate mechanisms underlying biofilm resistance. In addition, the growth of novel biomaterials with anti-adhesive nature, natural products, drugs, bioactive compounds, proteins, lipids, and carbohydrates are being researched. Recently, more and more attention has been given to various metal nanoparticles that have also appeared as antibiofilm agents in C. albicans. The intestinal epithelial obstacle exerts an crucial effect on keeping intestinal homeostasis and is increasingly associated with various disorders associated with the intestine such as inflammatory bowel disease (IBD), irritable bowel syndrome, metabolic syndrome, allergies, hepatic inflammation, septic shock, etc. However, whether their involvement in the prevention of other intestinal disorders like IBD are useful in C. albicans remains unknown. Further studies must be carried out in order to validate their inhibition functions in intestinal C. albicans. This provides innovates ideas for intestinal C. albicans treatment.

Bacillus subtilis BS-15 Effectively Improves Plantaricin Production and the Regulatory Biosynthesis in Lactiplantibacillus plantarum RX-8.

Plantaricin is a broad-spectrum bacteriocin produced by Lactiplantibacillus plantarum with significant food industry application potential. It was found that the plantaricin production of L. plantarum RX-8 was enhanced when co-culturing with Bacillus subtilis BS-15. This study, therefore, set out to explore how B. subtilis BS-15 induces biosynthesis of plantaricin. The effect of co-culturing with B. subtilis BS-15 on cell growth, plantaricin production, quorum-sensing (QS) signal molecule PlnA/autoinducer-2 (AI-2) secretion, as well as plantaricin biosynthesis gene cluster and AI-2 synthesis-associated gene expression, was investigated in bacteriocin-producer L. plantarum RX-8. When L. plantarum RX-8 and B. subtilis BS-15 were co-inoculated in Man–Rogosa–Sharp (MRS) for 20 h at an inoculum ratio of 1:1 (106:106 CFU/ml), the greatest plantaricin output (2,048 AU/ml) was obtained, rising by 32-fold compared with the monoculture of L. plantarum RX-8. Additionally, co-culture increased PlnA-inducing activity and AI-2 activity by 8- and 1.14-fold, respectively, over monoculture. RT-qPCR findings generated every 4 h (4–32 h) demonstrated that B. subtilis BS-15 remarkably improved the transcription of plnABCD and plnEF, and increased pfs and luxS transcription, even when using 200 mM D-ribose, a kind of AI-2 inhibitor. Based on the above findings, co-culturing with B. subtilis BS-15 as an environmental stimulus could activate the plantaricin induction via the PlnA-mediated intraspecies QS system and the AI-2-mediated interspecies QS system. Moreover, the inducing effect of PlnA and AI-2 in co-culture was independent. Differential proteomics analysis of B. subtilis BS-15 in co-culture indicated that bacteriocin-inducing regulatory mechanism may be related to flagellar assembly, peptidoglycan biosynthesis, anaerobic respiration, glycine cleavage system, or thiamin pyrophosphate biosynthesis.