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Artykuły w czasopismach na temat "Quorum Stimuli"
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Mandabi, Aviad, Hadas Ganin, Pnina Krief, Josep Rayo i Michael M. Meijler. "Karrikins from plant smoke modulate bacterial quorum sensing". Chem. Commun. 50, nr 40 (2014): 5322–25. http://dx.doi.org/10.1039/c3cc47501h.
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Geethanjali, V. Dinesh Kumar, N. Raghu, T. S. Gopenath, S. Veerana Gowda, K. W. Ong, M. S. Ranjith i in. "Quorum sensing: A molecular cell communication in bacterial cells". Journal of Biomedical Sciences 5, nr 2 (17.04.2019): 23–34. http://dx.doi.org/10.3126/jbs.v5i2.23635.
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Background: Quorum sensing is a cell-to-cell communication, which is extensively observed in bacteria. This process allows the cell to detect, analyze, share and act upon various environmental stimuli based on cell density. The molecular aspect of this process is the secretion and detection of chemical signaling molecules called autoinducers (AIs), which act upon the gene expression. The quorum sensing signaling pathway is specifically observed only bulk population or in other words, the quorum sensing is effective only in high cell density. The quorum sensing circuit in the bacterial population is widely studied under the following heading; quorum sensing in Gram positive bacterium, Quorum sensing in Gram negative bacterium and the Quorum sensing with respect to Interkingdom communication. These models are studied using the widely studied models like Vibrio fischeri in Gram negative QS circuit, Staphylococcus aureus in Gram positive QS circuit and Vibrio harveyi. This review paper details the introduction of quorum sensing and their gene level explanation and how they effect on the virulence of a particular species of bacteria. This paper also throws light on the realization that the bacteria has the capable of performing coordinated activities that was so long contributed to the eukaryotic cell performance.
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DeLisa, Matthew P., James J. Valdes i William E. Bentley. "Mapping Stress-Induced Changes in Autoinducer AI-2 Production in Chemostat-Cultivated Escherichia coli K-12". Journal of Bacteriology 183, nr 9 (1.05.2001): 2918–28. http://dx.doi.org/10.1128/jb.183.9.2918-2928.2001.
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ABSTRACT Numerous gram-negative bacteria employ a cell-to-cell signaling mechanism, termed quorum sensing, for controlling gene expression in response to population density. Recently, this phenomenon has been discovered in Escherichia coli, and while pathogenicE. coli utilize quorum sensing to regulate pathogenesis (i.e., expression of virulence genes), the role of quorum sensing in nonpathogenic E. coli is less clear, and in particular, there is no information regarding the role of quorum sensing during the overexpression of recombinant proteins. The production of autoinducer AI-2, a signaling molecule employed by E. coli for intercellular communication, was studied in E. coli W3110 chemostat cultures using a Vibrio harveyi AI-2 reporter assay (M. G. Surrette and B. L. Bassler, Proc. Natl. Acad. Sci. USA 95:7046–7050, 1998). Chemostat cultures enabled a study of AI-2 regulation through steady-state and transient responses to a variety of environmental stimuli. Results demonstrated that AI-2 levels increased with the steady-state culture growth rate. In addition, AI-2 increased following pulsed addition of glucose, Fe(III), NaCl, and dithiothreitol and decreased following aerobiosis, amino acid starvation, and isopropyl-β-d-thiogalactopyranoside-induced expression of human interleukin-2 (hIL-2). In general, the AI-2 responses to several perturbations were indicative of a shift in metabolic activity or state of the cells induced by the individual stress. Because of our interest in the expression of heterologous proteins in E. coli, the transcription of four quorum-regulated genes and 20 stress genes was mapped during the transient response to induced expression of hIL-2. Significant regulatory overlap was revealed among several stress and starvation genes and known quorum-sensing genes.
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Liu, Guiqing, Li Cao, Xuehong Qiu i Richou Han. "Quorum Sensing Activity and Hyphal Growth by External Stimuli in the Entomopathogenic Fungus Ophiocordyceps sinensis". Insects 11, nr 4 (26.03.2020): 205. http://dx.doi.org/10.3390/insects11040205.
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The entomopathogenic fungus Ophiocordyceps sinensis is one of the best known and most precious medicines and health food in China. The blastospores-hyphae (dimorphism) transition of this fungus in host hemolymph is critical for the virulence and the mummification of host larvae. To regulate this transition, the effects of inoculum density and fifteen chemicals including fungal nutrients, fungal metabolites, quorum-sensing molecules (QSMs) and insect hormones on the dimorphism in O. sinensis were investigated in vitro. The blastospores tended to exhibit budding growth when inoculated at 107 blastospores per mL, and hyphal growth at concentrations lower than 106 blastospores per mL. At 105 blastospores per mL, the percentage of hyphal formation decreased with the addition of filtered spent medium containing 107 blastospores per mL, indicating the quorum-sensing effect. Blastospores-hyphae transition in this fungus by fifteen chemicals was varied from no response to dimorphic reversion. The addition of N-acetylglucosamine at three concentrations significantly stimulated hyphal formation while inhibiting budding growth. For the first time, insect hormone 20-hydroxyecdysone was found to be involved in the hyphal formation in fungi. These results open new possibilities to regulate the dimorphism, which would be beneficial for the cultivation of the Chinese cordyceps.
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Liu, Zhi, Ansel Hsiao, Adam Joelsson i Jun Zhu. "The Transcriptional Regulator VqmA Increases Expression of the Quorum-Sensing Activator HapR in Vibrio cholerae". Journal of Bacteriology 188, nr 7 (1.04.2006): 2446–53. http://dx.doi.org/10.1128/jb.188.7.2446-2453.2006.
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ABSTRACT Vibrio cholerae is the causative agent of the severe diarrheal disease cholera. A number of environmental stimuli regulate virulence gene expression in V. cholerae, including quorum-sensing signals. At high cell densities, quorum sensing in V. cholerae invokes a series of signal transduction pathways in order to activate the expression of the master regulator HapR, which then represses the virulence regulon and biofilm-related genes and activates protease production. In this study, we identified a transcriptional regulator, VqmA (VCA1078), that activates hapR expression at low cell densities. Under in vitro inducing conditions, constitutive expression of VqmA represses the virulence regulon in a HapR-dependent manner. VqmA increases hapR transcription as measured by the activity of the hapR-lacZ reporter, and it increases HapR production as measured by Western blotting. Using a heterogenous luxCDABE cosmid, we found that VqmA stimulates quorum-sensing regulation at lower cell densities and that this stimulation bypasses the known LuxO-small-RNA regulatory circuits. Furthermore, we showed that VqmA regulates hapR transcription directly by binding to its promoter region and that expression of vqmA is cell density dependent and autoregulated. The physiological role of VqmA is also discussed.
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Mujawdiya, Pavan K., i Suman Kapur. "Modulation of Gut Microbiota through Dietary Phytochemicals as a Novel Anti-infective Strategy". Current Drug Discovery Technologies 17, nr 4 (8.09.2020): 498–506. http://dx.doi.org/10.2174/1570163816666191107124214.
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: Quorum Sensing (QS) is a phenomenon in which bacterial cells communicate with each other with the help of several low molecular weight compounds. QS is largely dependent on population density, and it triggers when the concentration of quorum sensing molecules accumulate in the environment and crosses a particular threshold. Once a certain population density is achieved and the concentration of molecules crosses a threshold, the bacterial cells show a collective behavior in response to various chemical stimuli referred to as “auto-inducers”. The QS signaling is crucial for several phenotypic characteristics responsible for bacterial survival such as motility, virulence, and biofilm formation. Biofilm formation is also responsible for making bacterial cells resistant to antibiotics. : The human gut is home to trillions of bacterial cells collectively called “gut microbiota” or “gut microbes”. Gut microbes are a consortium of more than 15,000 bacterial species and play a very crucial role in several body functions such as metabolism, development and maturation of the immune system, and the synthesis of several essential vitamins. Due to its critical role in shaping human survival and its modulating impact on body metabolisms, the gut microbial community has been referred to as “the forgotten organ” by O`Hara et al. (2006) [1]. Several studies have demonstrated that chemical interaction between the members of bacterial cells in the gut is responsible for shaping the overall microbial community. : Recent advances in phytochemical research have generated a lot of interest in finding new, effective, and safer alternatives to modern chemical-based medicines. In the context of antimicrobial research various plant extracts have been identified with Quorum Sensing Inhibitory (QSI) activities among bacterial cells. This review focuses on the mechanism of quorum sensing and quorum sensing inhibitors isolated from natural sources.
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Sheikh, Shaheen, i Vidya Tale. "EFFECT OF GREEN SYNTHESIZED SILVER NANOPARTICLES ON QUORUM SENSING INHIBITION OF UTI PATHOGENS". Asian Journal of Pharmaceutical and Clinical Research 10, nr 5 (1.05.2017): 302. http://dx.doi.org/10.22159/ajpcr.2017.v10i5.16949.
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Objective: The present study was conducted to evaluate the antimicrobial and anti-quorum sensing (QS) ability of nanoparticles synthesized usingfruit wastes.Methods: QS is a system of response and stimuli correlated to population density. Bacteria by QS secrete certain signaling molecules called autoinducers. These bacteria also have a receptor that can specifically detect the signaling molecule known as an inducer. Since QS governs numerous processes in bacteria including virulence, QS inhibition promises to be an ideal target for the development of novel therapeutics. In the present study, silver nanoparticles (AgNPs) synthesized from the ginger, lemon peel, cinnamon, corn silk, pomegranate peel, and orange peel exhibited anti-QS properties by inhibiting violacein production in Chromobacterium violaceum assayed using agar well diffusion method.Results: AgNPs were synthesized from various cost-effective fruit waste sources. These AgNPs exhibited significant antibacterial and anti-QS properties.Conclusion: Hence, such sources can be explored for developing the effective therapy for urinary tract infections.Keywords: Silver nanoparticles, Quorum sensing, Urinary Tract infection.
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Wedge, Marie-Ève, Erika Sayuri Naruzawa, Martha Nigg i Louis Bernier. "Diversity in yeast–mycelium dimorphism response of the Dutch elm disease pathogens: the inoculum size effect". Canadian Journal of Microbiology 62, nr 6 (czerwiec 2016): 525–29. http://dx.doi.org/10.1139/cjm-2015-0795.
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Dutch elm disease (DED) is caused by the dimorphic fungi Ophiostoma ulmi, Ophiostoma novo-ulmi, and Ophiostoma himal-ulmi. A cell population density-dependent phenomenon related to quorum sensing was previously shown to affect the reversible transition from yeast-like to mycelial growth in liquid shake cultures of O. novo-ulmi NRRL 6404. Since the response to external stimuli often varies among DED fungal strains, we evaluated the effect of inoculum size on 8 strains of the 3 species of DED agents by determining the proportion of yeast and mycelium produced at different spore inoculum concentrations in defined liquid shake medium. The results show that not all DED fungi strains respond similarly to inoculum size effect, since variations were observed among strains. It is thus possible that the different strains belonging to phylogenetically close species use different signalling molecules or molecular signalling pathways to regulate their growth mode via quorum-sensing mechanisms.
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Katzianer, David S., Hui Wang, Ryan M. Carey i Jun Zhu. "“Quorum Non-Sensing”: Social Cheating and Deception in Vibrio cholerae". Applied and Environmental Microbiology 81, nr 11 (27.03.2015): 3856–62. http://dx.doi.org/10.1128/aem.00586-15.
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ABSTRACTQuorum sensing (QS) is widely used by bacteria to coordinate behavior in response to external stimuli. InVibrio cholerae, this process is important for environmental survival and pathogenesis, though, intriguingly, a large percentage of natural isolates are QS deficient. Here, we show that QS-deficient mutants can spread as social cheaters by ceasing production of extracellular proteases under conditions requiring their growth. We further show that mutants stimulate biofilm formation and are over-represented in biofilms compared to planktonic communities; on this basis, we suggest that QS-deficient mutants may have the side effect of enhancing environmental tolerance of natural populations due to the inherent resistance properties of biofilms. Interestingly, high frequencies of QS-deficient individuals did not impact production of QS signaling molecules despite mutants being unable to respond to these inducers, indicating that these variants actively cheat by false signaling under conditions requiring QS. Taken together, our results suggest that social cheating may drive QS deficiency emergence withinV. choleraenatural populations.
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Vasudevan, Sahana, i Asmita A. Prabhune. "Photophysical studies on curcumin-sophorolipid nanostructures: applications in quorum quenching and imaging". Royal Society Open Science 5, nr 2 (luty 2018): 170865. http://dx.doi.org/10.1098/rsos.170865.
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Sophorolipid biosurfactants are biodegradable, less toxic and FDA approved. The purified acidic form of sophorolipid is stimuli-responsive with self-assembling properties and used for solubilizing hydrophobic drugs. This study encapsulated curcumin (CU) with acidic sophorolipid (ASL) micelles and analysed using photophysical studies like UV-visible spectroscopy, photoluminescence (PL) spectroscopy and time-correlated single photon counting (TCSPC). TEM images have revealed ellipsoid micelles of approximately 100 nm size and were confirmed by dynamic light scattering. The bacterial fluorescence uptake studies showed the uptake of formed CUASL nanostructures into both Gram-positive and Gram-negative bacteria. They also showed quorum quenching activity against Pseudomonas aeruginosa . The results have demonstrated this system has potential theranostic applications.
Rozprawy doktorskie na temat "Quorum Stimuli"
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Rajasree, Kalagiri. "Structural Studies on the Intracellular Steps that Govern the Staphylococcus aureus Quorum Sensing System". Thesis, 2015. https://etd.iisc.ac.in/handle/2005/4819.
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Quorum sensing in bacteria has been extensively examined over the past two decades. These studies suggest that the molecular mechanism that governs quorum sensing incorporates niche-specific, environmentally sensitive information in addition to chemosensory information embedded in the signaling molecules- autoinducing peptides (AIPs) or homoserine lactones. One aspect of the quorum sensing mechanism that was examined in the course of this study was the sensitivity and fidelity of the intracellular signal transduction cascade that correlates extracellular information with a cellular response. The Agr quorum-sensing system in Staphylococcus aureus provided a good model system to examine this aspect of the mechanism. As individual components of this mechanism had been characterized by other groups earlier, the tools to probe the intracellular cascade existed at the start of this project. This thesis describes the progress made in the course of studies to examine the role of two important intracellular components- AgrC and AgrA. These proteins were examined using a variety of biophysical, biochemical and structural biology techniques.
Części książek na temat "Quorum Stimuli"
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Lozano, Celia, Tobias Bäuerle i Clemens Bechinger. "Active Brownian Particles with Programmable Interaction Rules". W Active Matter and Nonequilibrium Statistical Physics, 219–29. Oxford University PressOxford, 2022. http://dx.doi.org/10.1093/oso/9780192858313.003.0007.
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Abstract It is commonly assumed that collective dynamics in living system emerges when individuals adapt their behavior to their peers. Usually, individuals respond to perceived stimuli by moving according to certain behavioral rules , e.g. attraction and or alignment with and to neighbours. Assessing the consequences of such individual perception-response rules at the group level is of paramount importance to understand, predict, and reproduce a given collective behavior. Here, we demonstrate that quorum sensing being employed by bacterial organisms can be implemented in a system of active colloidal particles whose response is controlled on a single particle level using an optical feedback mechanism. With this approach we are able to demonstrate that quorum sensing strongly enhances the formation of clusters, which are – compared to motility induced phase separation of uncontrolled particles – observed at considerably smaller densities.
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Alvarez-Lorenzo, Carmen, i Angel Concheiro. "Review of Smart Materials for Controlled Drug Release". W Fundamentals of Smart Materials, 170–92. The Royal Society of Chemistry, 2020. http://dx.doi.org/10.1039/bk9781782626459-00170.
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Chapter 15 reviews smart materials for controlled drug release. Systemically-administered controlled release systems allow fine-tuning of drug bioavailability, by regulating the amount and the rate at which the drug reaches the bloodstream, which is critical for the success of the therapy. Some drugs pose important problems in terms of efficacy and safety (e.g., antitumor drugs, antimicrobials) and suffer instability problems in the biological environment (e.g., gene materials), and thus the therapeutic performance of these drugs is improved when they are selectively directed (targeted) from the bloodstream to the site of action (tissues, cells or cellular structures). Both macro-dosage forms and nano-delivery systems may notably benefit from stimuli-responsive materials. Differently to pre-programmed drug release systems, formulations that provide discontinuous release as a function of specific signals (stimuli) are advantageous in many situations. Triggering drug release where, when, and how it is needed requires detailed knowledge of the changes that the illness causes in terms of physiological parameters. These changes can be characterized in terms of biomarkers (e.g., glucose, specific enzymes, or quorum sensing signals in the case of infection) and physicochemical parameters (pH, ions, temperature, glutathione) that may be exploited as internal stimuli. When the physio–pathological changes are too weak or poorly specific, the application of external stimuli may be an alternative. External sources of temperature, ultrasound, light, and magnetic or electric fields may allow for the focal switch on/off of drug release. This chapter provides an overview of the interest in activation-modulated and feedback-regulated controlled release systems, the mechanisms behind them, and some specific examples of responsive materials and their applications.