SEARCH · PubMed Health

Results for “Quorum Sensing”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 955 records · Page 53Linked to original sources

PubMed2003

Molecular identification of pathogenic and nonpathogenic strains of Vibrio harveyi using PCR and RAPD.

Fifteen environmental samples of Vibrio spp. isolated from healthy and diseased shrimps were tested for pathogenicity to juvenile shrimps. Two isolates, strains Z2 and Z3, were observed to be pathogenic, causing 100% mortality of the target host compared to the control strain Vibrio harveyi ATCC 14126. Environmental and type strains were subjected to molecular characterization by restriction fragment length polymorphism (RFLP) and PCR using primers targeted to different virulence, transcriptional regulator, or quorum sensing genes from V. harveyi. Primers designed for luxN were specific and identified all the environmental strains as V. harveyi. The random amplified polymorphic DNA (RAPD) method was used to differentiate between pathogenic and nonpathogenic strains of V. harveyi. These methodologies allowed us to detect and distinguish strains virulent and avirulent to juvenile shrimp.

Animal Diseases↗

PubMed1999

Recent trends in the biochemistry of surfactin.

The name surfactin refers to a bacterial cyclic lipopeptide, primarily renowned for its exceptional surfactant power since it lowers the surface tension of water from 72 mN m-1 to 27 mN m-1 at a concentration as low as 20 microM. Although surfactin was discovered about 30 years ago, there has been a revival of interest in this compound over the past decade, triggered by an increasing demand for effective biosurfactants for difficult contemporary ecological problems. This simple molecule also looks very promising as an antitumoral, antiviral and anti-Mycoplasma agent. Structural characteristics show the presence of a heptapeptide with an LLDLLDL chiral sequence linked, via a lactone bond, to a beta-hydroxy fatty acid with 13-15 C atoms. In solution, the molecule exhibits a characteristic "horse saddle" conformation that accounts for its large spectrum of biological activity, making it very attractive for both industrial applications and academic studies. Surfactin biosynthesis is catalysed non-ribosomally by the action of a large multienzyme complex consisting of four modular building blocks, called the surfactin synthetase. The biosynthetic activity involves the multicarrier thiotemplate mechanism and the enzyme is organized in structural domains that place it in the family of peptide synthetases, a class of enzymes involved in peptidic secondary-metabolite synthesis. The srfA operon, the sfp gene encoding a 4'-phosphopantetheinyltransferase and the comA regulatory gene work together for surfactin biosynthesis, while the gene encoding the acyltransferase remains to be isolated. Concerning surfactin production, there is no indication whether the genetic regulation, involving a quorum-sensing mechanism, overrides other regulation factors promoted by the fermentation conditions. Knowledge of the modular arrangement of the peptide synthetases is of the utmost relevance to combinatorial biosynthetic approaches and has been successfully used at the gene level to modify the surfactin template. Biosynthetic and genetic rationales have been described for building variants. A fine study of the structure/function relationships associated with the three-dimensional structure has led to the recognition of the specific residues required for activity. These studies will assist researchers in the selection of molecules with improved and/or refined properties useful in oil and biomedical industries.

Bacillus↗

PubMed2006

Identification of the critical role of Tyr-194 in the catalytic activity of a novel N-acyl-homoserine lactonase from marine Bacillus cereus strain Y2.

Enzymatic disruption of quorum-sensing (QS) pathways in pathogenic organisms is a promising anti-infection therapeutic strategy. AHL-lactonase, a potent tool for biocontrol, can hydrolyze QS signal molecule N-acyl-homoserine lactones (AHLs) into inactive products, thereby blocking the QS systems. A marine bacterial isolate Y2, identified as a Bacillus cereus subsp., was found capable of inactivating AHLs. The aiiA gene encoding the AHL-degrading enzyme from bacterial strain Y2 was cloned and expressed in Escherichia coli. The 28-kDa recombinant Y2-AiiA protein was purified and showed strong AHL-degrading activity. Sequence comparisons of Y2-aiiA with known AHL-lactonases revealed high identities in the deduced amino-acid sequences. Functional determination of a potential catalytic residue Tyr-194 of AHL-lactonases was performed by site-directed mutagenesis. As judged by AHL-degrading bioassay, substitution of Tyr-194 with Ala resulted in a dramatic decrease of activity compared with wild-type (WT) recombinant Y2-AiiA, although the expression level of the mutated Y2-AiiA protein was equivalent to that of WT Y2-AiiA. These results suggested that the conserved residue Tyr-194 is critical for catalytic function of the novel AHL-lactonase.

Amino Acid Sequence↗

PubMed1999

The development of bacterial biofilms on indwelling urethral catheters.

The biofilm mode of growth has been implicated in the majority of human bacterial infections. In the urinary tract, notable biofilm-associated infections include prostatitis, chronic cystitis, struvite urolithiasis, and catheter-associated infections. Biofilms protect the causative organisms from host defences and antimicrobial therapy. Biofilm formation has traditionally been considered to result from adhesion and capsule formation by adherent microorganisms. Recent work has shown that a large number of genes are activated during this process, some of which have been associated with twitching motility, quorum sensing, and slow growth. In this paper, we review some of the recent work on biofilm biology and highlight its role in urinary tract infections, particularly those associated with urinary catheters.

Biofilms↗

PubMed2026

Microbial partnerships and molecular mechanisms in plant stress physiology for climate-resilient and sustainable farming.

Plant-microbial partnerships and their underlying molecular mechanisms are indispensable, natural drivers of improved nutrient acquisition and stress tolerance in the face of climate-driven environmental challenges. Modern multi-omics tools, when coupled with artificial intelligence and synthetic biology, enable the precise design of targeted bioinoculants and synthetic microbial consortia. Translating these advanced microbiome-based strategies into scalable, field-level agricultural applications provides a sustainable path toward securing global food production while maintaining soil health. Global climate change imposes multifaceted abiotic and biotic stresses on crops, disrupting physiological and molecular processes and threatening agricultural productivity. Plant-associated microbes represent an underexplored yet powerful ally in enhancing crop resilience. This review presents current knowledge of plant-microbe interactions and the molecular mechanisms governing plant stress physiology, with an emphasis on climate-resilient and sustainable farming. Hence, ever-changing environmental cues pose a significant burden on agricultural productivity, and plant-associated microbial communities modulate a cascade of physiological and molecular responses, including production of phytohormones, signaling, regulation of reactive oxygen species homeostasis, and activation of plant immune responses to help plants withstand stress and enhance productivity. Moreover, root exudates, phytohormones, and quorum sensing mediate the central communication networks, facilitating plant-microbe cross talk. Additionally, the advances in OMICs approaches aid in disentangling the molecular underpinnings of these interactions by providing mechanistic insights and potential candidate gene targets for crop improvement and stress resilience. In the post-genomic era, integrating artificial intelligence and big data analysis to optimize microbiome-based strategies for sustainable agriculture is a new frontier for disentangling plant-microbe symbiosis to improve soil health, enhance crop yields, and improve stress tolerance. Thus, by integrating the ecological, physiological, and molecular perspectives, this review highlights the transformative potential of harnessing plant-microbe symbiosis for climate-resilient and sustainable agriculture.

Stress, Physiological↗

PubMed2003

Cytolysin gene expression in Enterococcus faecalis is regulated in response to aerobiosis conditions.

Here we investigate the expression of cylL(L)and cylL(S), the genes that encode the structural subunits of the cytolysin/haemolysin of Enterococcus faecalis, in response to aerobiosis conditions. Haemolysis assays of E. faecalis strains cultured under aerobic and anaerobic conditions revealed three different haemolytic phenotypes, one of which exhibited greater haemolysis under anaerobic conditions than under aerobic conditions, and was shown to be associated with the presence of the cyl genes. Reporter gene studies revealed that cylL(L) L(S) promoter activity was significantly greater (up to 8.6-fold) under anaerobic compared to aerobic conditions throughout batch growth, demonstrating that these genes are regulated in response to the degree of aerobiosis. Band shift assays confirmed the binding of a protein factor to the region between 202 and 37 bp upstream of the cylL(L)start codon, and a higher level of binding was observed with anaerobically derived cell-free extracts than with extracts of aerobically grown cells. This is the first report of an oxygen-regulated virulence factor in E. faecalis (that is distinct from the quorum-sensing regulatory system reported previously), and may be of in vivo relevance for the bacterium in biofilms and other environments characterised by oxygen gradients.

Aerobiosis↗

PubMed2005

Alleviation of insulitis and moderation of diabetes in NOD mice following treatment with a synthetic Pseudomonas aeruginosa signal molecule, N-(3-oxododecanoyl)-L-homoserine lactone.

Quorum sensing signal molecules (QSSMs) from the bacterium Pseudomonas aeruginosa control bacterial population density and the expression of virulence determinants. Coincidentally, and possibly to allow this pathogen to gain a foothold in the human body, certain signal molecules also downregulate immunological responses in an apparently T-helper 1-selective manner, which would suggest their application as therapeutics to some autoimmune diseases. In the present paper, experiments are described that indicate that one particular signal molecule, a synthetic N-(3-oxododecanoyl)-L-homoserine lactone, can be used to alleviate insulitis and diabetes in non-obese diabetic (NOD) mice, suggesting that bacterial signal molecules may represent a novel source of immune modulatory compounds for the treatment of type 1 diabetes, which afflicts more than 2 million individuals in Europe and North America.

4-Butyrolactone↗

PubMed2005

Role of biofilms in neurosurgical device-related infections.

Bacterial biofilms have recently been shown to be important in neurosurgical device-related infections. Because the concept of biofilms is novel to most practitioners, it is important to understand that both traditional pharmaceutical therapies and host defense mechanisms that are aimed at treating or overcoming free-swimming bacteria are largely ineffective against the sessile bacteria in a biofilm. Bacterial biofilms are complex surface-attached structures that are composed of an extruded extracellular matrix in which the individual bacteria are embedded. Superimposed on this physical architecture is a complex system of intercellular signaling, termed quorum sensing. These complex organizational features endow biofilms with numerous microenvironments and a concomitant number of distinct bacterial phenotypes. Each of the bacterial phenotypes within the biofilm displays a unique gene expression pattern tied to nutrient availability and waste transport. Such diversity provides the biofilm as a whole with an enormous survival advantage when compared to the individual component bacterial cells. Thus, it is appropriate to view the biofilm as a multicellular organism, akin to metazoan eukaryotic life. Bacterial biofilms are much hardier than free floating or planktonic bacteria and are primarily responsible for device-related infections. Now that basic research has demonstrated that the vast majority of bacteria exist in biofilms, the paradigm of biofilm-associated chronic infections is spreading to the clinical world. Understanding how these biofilm infections affect patients with neurosurgical devices is a prerequisite to developing strategies for their treatment and prevention.

Biofilms↗

PubMed2006

The diabetic foot: the importance of biofilms and wound bed preparation.

Biofilms are ubiquitous and medically important complex structures consisting of microbial-associated cells embedded in self-produced extracellular matrix of hydrated extrapolymeric substances, which are irreversibly attached to a biological or nonbiological surface. Bacteria that reside as biofilms are resistant to traditional therapy. This alternative community in which microbes exist has recently attracted interest as a potential reason why chronic wounds do not heal. This may be especially important for diabetic foot ulcers, which are often characterized by their refractory nature, their predisposition to have associated underlying infection, and their improvement with débridement. Animal and in vitro models have been developed to better study biofilms, which will allow a venue for therapeutic intervention. Potential opportunities exist that include prevention of bacterial attachment, prevention of biofilm formation, disruption of the biofilm to allow penetration of topical antimicrobial agents, interference with quorum sensing, and enhancement of bacteria dispersion from biofilms to a more easily destroyed planktonic state.

Animals↗

PubMed2004

PA-I lectin from Pseudomonas aeruginosa binds acyl homoserine lactones.

The study analyses the binding affinities of Pseudomonas aeruginosa PA-I lectin (PA-IL) to three N-acyl homoserine lactones (AHSL), quorum sensing signal molecules responsible for cell-cell communication in bacteria. It shows that like some plant lectins, PA-IL has a dual function and, besides its carbohydrate-binding capacity, can accommodate AHLS. Formation of complexes between PA-IL and AHSL with acyl side chains composed of 4, 6 or 12 methyl groups is characterized by changes in the emissions of two incorporated fluorescent markers, TNS and IAEDANS, both derivatives of naphthalene sulfonic acid. PA-IL shows increasing affinities to lactones with longer aliphatic side chains. The values of the apparent dissociation constants (K(d)), which are similar to the previously determined K(d) for the adenine high affinity binding, and the similar effects of lactones and adenine on the TNS emission indicate one identical binding site for these ligands, which is suggested to represent the central cavity of the oligomeric molecule formed after the association of the four identical subunits of PA-IL. Intramolecular distances between the fluorescent markers and protein Trp residues are determined by fluorescence resonance energy transfer (FRET).

Adhesins, Bacterial↗

PubMed2005

Crystallization and preliminary crystallographic analysis of Bacillus thuringiensis AHL-lactonase.

The quorum sensing (QS) systems in Gram-negative bacteria are mostly associated with diffusible N-acyl-L-homoserine lactones (AHLs). AHL-degrading enzymes hydrolyze the AHLs into inactive molecules, thereby blocking the QS systems that are closely linked to virulence factor production and biofilm formation. Consequently, these enzymes have recently attracted intense interest for the development of anti-infection therapies for plants and animals. However, despite significant progress in the investigation of AHL-degrading enzymes, no structure is yet available. Accordingly, this study reports on the expression and purification of the AHL-lactonase from Bacillus thuringiensis subsp. kurstaki HD263, as well as the successful crystallization of the enzyme. High-quality native crystals were obtained and a complete data set collected at 2.0 A resolution. The native crystal was found to belong to the space group P2(1)2(1)2(1), with unit cell parameters a=52.7 A, b=55.9 A, and c=74.1 A and one molecule in the asymmetric unit. MAD data were also collected at 2.4 A resolution for a SeMet-substituted crystal.

Bacillus thuringiensis↗

PubMed2006

Regulatory roles of spnT, a novel gene located within transposon TnTIR.

The transposon TnTIR contains spnIR quorum-sensing system regulating sliding motility and the production of nuclease, biosurfactant, and prodigiosin in Serratia marcescens. Within TnTIR, a gene named spnT is upstream of and co-transcribed with spnI. SpnT is a cytoplasmic protein and its level peaks during early stationary phase. spnT over-expression resulted in inhibition of sliding motility and synthesis of prodigiosin, and biosurfactant similar to spnR. spnT but not spnR over-expression induced cell elongation and aberrant DNA replication in S. marcescens and Escherichia coli strains. In comparison with wild-type E. coli strain, over-expression of spnT in an E. coli priA and dnaC double-mutant strain did not lead to the aberrant cell morphology phenotypes, suggesting SpnT may act through the recombination-dependent DNA replication system. As spnT over-expression inhibited swarming but not swimming motility, SpnT may indirectly function as a negative regulator of surface-dependent migration and secondary metabolite production.

Bacterial Proteins↗

PubMed2006

Distinct and overlapping binding sites of Pseudomonas aeruginosa Hfq and RsmA proteins on the non-coding RNA RsmY.

In Pseudomonas aeruginosa the Rsm system is involved in regulation of quorum-sensing and virulence gene expression. Our recent studies revealed that the stability and abundance of the non-coding RNA RsmY, which antagonizes the translational regulator RsmA, is dependent on Hfq. Here, we show that Hfq and RsmA bind concurrently to RsmY. Enzymatic probing of RsmY RNA in the presence of RsmA and Hfq verified the proposed -GGA- motifs as RsmA binding sites and located Hfq binding sites in single-stranded regions adjacent to stem-loop structures, respectively. We conclude that distinct binding of Hfq and RsmA on RsmY RNA permits RsmY-mediated RsmA titration upon binding to and stabilization of RsmY RNA by Hfq. In addition, we provide evidence that Hfq sequesters RNase E cleavage sites on RsmY, which explains the previously observed dependence of RsmY RNA stability on Hfq.

Bacterial Proteins↗

PubMed2005

A rule-based approach to the modelling of bacterial ecosystems.

This paper presents an approach to ecological/evolutionary modelling that is inspired by natural bacterial ecosystems and bacterial evolution. An individual-based artificial ecosystem model is proposed, which is designed to explore the evolvability of adaptive behavioural strategies in artificial bacteria represented by rule-based learning classifier systems. The proposed ecosystem model consists of a n-dimensional environmental grid, which can contain different types of artificial resources in arbitrary arrangements. The resources provide the energy that is necessary for the organisms to sustain life, and can trigger different types of behaviour in the organisms, such as movement towards nutrients and away from toxic substances, growth, and the controlled release of signalling resources. The balance between energy and material is modelled carefully to ensure that the ecosystem is dissipative. Those organisms that are able to efficiently exploit the available resources gradually accumulate enough energy to reproduce (by binary fission) and generate copies of themselves in the environment. Organisms are also able to produce their own resources, which can potentially be used as markers to send signals to other organisms (a behaviour known as quorum sensing). The complex relationships between stimuli and actions in the organisms are stochastically altered by means of mutations, thus enabling the organisms to adapt to their environment and maximise their lifespan and reproductive success. In this paper, the proposed bacterial ecosystem model is defined formally and its structure is discussed in detail. This is followed by results from simulation experiments that illustrate the model's operation and how it can be used in evolutionary modelling/computing scenarios.

Bacteria↗

PubMed2005

Genomics, metagenomics and proteomics in biomining microorganisms.

The use of acidophilic, chemolithotrophic microorganisms capable of oxidizing iron and sulfur in industrial processes to recover metals from minerals containing copper, gold and uranium is a well established biotechnology with distinctive advantages over traditional mining. A consortium of different microorganisms participates in the oxidative reactions resulting in the extraction of dissolved metal values from ores. Considerable effort has been spent in the last years to understand the biochemistry of iron and sulfur compounds oxidation, bacteria-mineral interactions (chemotaxis, quorum sensing, adhesion, biofilm formation) and several adaptive responses allowing the microorganisms to survive in a bioleaching environment. All of these are considered key phenomena for understanding the process of biomining. The use of genomics, metagenomics and high throughput proteomics to study the global regulatory responses that the biomining community uses to adapt to their changing environment is just beginning to emerge in the last years. These powerful approaches are reviewed here since they offer the possibility of exciting new findings that will allow analyzing the community as a microbial system, determining the extent to which each of the individual participants contributes to the process, how they evolve in time to keep the conglomerate healthy and therefore efficient during the entire process of bioleaching.

Bacteria↗

PubMedDate not supplied

Infection in ventricular assist devices: the role of biofilm.

Ventricular assist devices improve hemodynamics in patients with heart failure, but like most implantable medical devices, they are prone to infection; organisms that are adept at forming biofilm cause most of these. Biofilm confers many advantages to the organisms, including protecting them against natural host defenses and antimicrobial therapies. This review will focus on the mechanisms of biofilm formation, including quorum sensing and subsequent changes in microbial gene and protein expression. Novel therapies targeting these processes, as well as improvements in device design and clinical management, have begun to emerge and will aid in the management of these recalcitrant infections.

Biofilms↗

PubMed2004

Mechanism of action of S-ribosylhomocysteinase (LuxS).

S-Ribosylhomocysteinase (LuxS) cleaves the thioether bond in S-ribosylhomocysteine to produce homocysteine and 4,5-dihydroxy-2,3-pentanedione. This reaction serves the dual purposes of detoxification of S-adenosylhomocysteine and production of type 2 quorum sensing molecule. Recent research has shown that LuxS uses Fe(2+) to catalyze an internal redox reaction, shifting the ribose carbonyl group from its C1 to C3 position. Subsequent beta-elimination completes this highly unusual reaction. LuxS and other enzymes on the same pathway may provide a novel class of antibacterial drug targets.

Anti-Bacterial Agents↗

PubMed2004

Small RNAs shed some light.

Small regulatory RNAs can act by pairing with their target messages, targeting themselves and the mRNA for degradation; Lenz et al. (this issue of Cell) now report that multiple small RNAs are essential regulators of the quorum-sensing systems of Vibrio species, including the regulation of virulence in V. cholerae.

Gene Expression Regulation, Bacterial↗