In this paper, we investigated the intra-species bacterial quorum sensing at the single cell level using a double droplet trapping system. Escherichia coli transformed to express the quorum sensing receptor protein, LasR, were encapsulated in microdroplets that were positioned adjacent to microdroplets containing the autoinducer, N-(3-oxododecanoyl)-L-homoserine lactone (OdDHL). Functional activation of the LasR protein by diffusion of the OdDHL across the droplet interface was measured by monitoring the expression of green fluorescent protein (GFP) from a LasR-dependent promoter. A threshold concentration of OdDHL was found to induce production of quorum-sensing associated GFP by E. coli. Additionally, we demonstrated that LasR-dependent activation of GFP expression was also initiated when the adjacent droplets contained single E. coli transformed with the OdDHL synthase gene, LasI, representing a simple quorum sensing circuit between two droplets.
In this paper, we investigated the intra-species bacterial quorum sensing at the single cell level using a double droplet trapping system. Escherichia coli transformed to express the quorum sensing receptor protein, LasR, were encapsulated in microdroplets that were positioned adjacent to microdroplets containing the autoinducer, N-(3-oxododecanoyl)-L-homoserine lactone (OdDHL). Functional activation of the LasR protein by diffusion of the OdDHL across the droplet interface was measured by monitoring the expression of green fluorescent protein (GFP) from a LasR-dependent promoter. A threshold concentration of OdDHL was found to induce production of quorum-sensing associated GFP by E. coli. Additionally, we demonstrated that LasR-dependent activation of GFP expression was also initiated when the adjacent droplets contained single E. coli transformed with the OdDHL synthase gene, LasI, representing a simple quorum sensing circuit between two droplets.
A Networking Paradigm Inspired by Cell Communication Mechanisms: 10.4018/978-1-4666-5125-8.ch002: This chapter provides a brief review of molecular communication, a networking paradigm inspired by cell communication mechanisms. In molecular communication
Quorum sensing (QS) is a cell density-dependent mechanism which enables a population of bacteria to coordinate cooperative behaviors in response to the accumulation of self-produced autoinducer signals in their local environment. An emerging framework is that the adaptive significance of QS in the regulation of production of costly extracellular metabolites («public goods») is to maintain the homeostasis of cooperation. We investigated this model using the phytopathogenic bacterium Burkholderia glumae, which we have previously demonstrated uses QS to regulate the production of rhamnolipids, extracellular surface-active glycolipids promoting the social behavior called «swarming motility». Using mass spectrometric quantification and chromosomal lux-based gene expression, we made the unexpected finding that when unrestricted nutrient resources are provided, production of rhamnolipids is carried out completely independently of QS regulation. This is a unique observation among known QS-controlled factors
Quorum sensing (QS) systems play global regulatory roles in bacterial virulence. They synchronize the expression of multiple virulence factors and they control and modulate bacterial antibiotic...
The term `quorum sensing (QS) is used to define a population density based communication mechanism which uses chemical signal molecules called autoinducers to trigger unique and varied changes in gene expression. Although several communication methods have been identified in bacteria that are unique to a particular species, one type of signal molecule, autoinducer-2 (AI-2) is linked to interspecies communication, indicating its potential as a universal signal for cueing a QS response among multiple bacterial types. In E. coli, AI-2 acts as an effector by binding to the QS repressor LsrR. As a result, LsrR unbinds and relieves repression of the lsr regulon, stimulating a subsequent QS gene expression cascade. In this dissertation, LsrR structure and in vitro binding activity are examined. Genomic binding and DNA microarray analyses are conducted and three novel sites putatively regulated by LsrR, yegE-udk, mppA and yihF, are revealed. Two cAMP receptor protein (CRP) binding locations in ...
U.S. researchers say they have discovered a novel quorum-sensing pathway in Saccharomyces cerevisiae, also known as bakers yeast.
A mathematical model, involving diffusion of extracellular compounds and cell interactions, has been adapted, in order to assess the quorum sensing process occurring in biofilms. Quorum sensing is a diffusion dependent phenomenon; therefore, accumulation levels of extra-cellular substances can directly affect cellular development. In order to modeling quorum sensing from artificially structured microbial consortia (ASMC), accumulation of N-acyl-Lhomoserine lactone (AHL) was studied within a biofilm formed with three bacterial species, Agrobacterium tumefaciens KYC6, Escherichia coli JM109 and green fluorescent protein (GFP), producer and reporter, Escherichia coli JM105. Different artificial biofilm structures or ASMC and conditions were considered when modeling cell behavior under particular experimental situations, such as: accumulation from external addition or internal production of N-acyl-L-homoserine lactone (AHL) in mixed mono- and multi-layered biofilms. Mathematical modeling results ...
DI-fusion, le Dépôt institutionnel numérique de lULB, est loutil de référencementde la production scientifique de lULB.Linterface de recherche DI-fusion permet de consulter les publications des chercheurs de lULB et les thèses qui y ont été défendues.
New approaches to deal with drug-resistant pathogenic bacteria are urgent. We studied the antibacterial effect of chitosans against an |i|Escherichia coli|/i| quorum sensing biosensor reporter strain and selected a non-toxic chitosan to evaluate its quorum sensing (QS) inhibition activity and its ef …
Quorum sensing (QS) or cell-to-cell communication is a process by which bacteria produce and detect signal molecules and thereby coordinate their behavior in a cell-density dependent manner. Two main QS systems can be distinguished: the acylhomoserine lactone (AHL) and the autoinducer-2 (AI-2). The sequenced genome of the marine bioluminescent Shewanella woodyi MS32 contains genes coding for these two main QS systems. This work aims at identifying the QS communication systems present in this bacterium and understanding its role in luminescence production and biofilm formation. The objective is also to find molecules that interfere with QS processes to inhibit adhesion and biofilm formation ...
TY - CONF. T1 - Motility quorum sensing locus (mqsa, B3022) links autoinducer 2 and biofilm formation in Escherichia coli K12. AU - González Barrios, Andres F.. AU - Zuo, Ronjung. AU - Bentley, William. AU - Hashimoto, Yoshifumi. AU - Yang, Li. AU - Wood, Thomas Keith. PY - 2005/12/1. Y1 - 2005/12/1. N2 - Previously, the cross-species, quorum-sensing signal AI-2 has been found to induce biofilm formation 30-fold in E. coli K12 (unpublished) by increasing expression of 67 genes, primarily those associated with chemotaxis, motility, and flagellar synthesis (Biotechnol. Bioeng. 88: 630, 2004), including the specific motility loci qseBC and flhD (Mol. Microbiol. 43: 809, 2002). Differential gene expression has also been used to show b3 022 is induced 8-fold in biofilms relative to planktonic cells (Appl. Microbiol. Biotechnol. 64: 515, 2004). In this report we show the b3022 locus, which we have re-named motility quorum sensing (mqsA), regulates motility through the two-component motility ...
The recent rapid growth in the biofilm field has spawned a number of new strategies for controlling biofilms. Below are descriptions of a few of these emergent strategies.. For some years it has been known that bacteria communicate with each other via diffusible signal molecules in a process termed "quorum sensing." The discovery that quorum sensing regulates biofilm formation opens the door to interdicting normal biofilm development through the use of quorum sensing inhibitors. This strategy of jamming communication is now moving towards application. One example of such inhibitors are the brominated furanones that block quorum sensing by acyl homoserine lactones, signal molecules used by Gram-negative bacteria. These furanones were first isolated from a marine algae and are thought to be part of the plants natural defense against microbial biofouling. Furanone-based quorum sensing inhibitors have been shown to increase antibiotic sensitivity of Pseudomonas aeruginosa biofilms and improve ...
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Quorum sensing molecules (QSMs) are involved in the regulation of complicated processes helping bacterial populations respond to changes in their cell-density. Although the QS gene cluster (comQXPA) has been identified in the genome sequence of some bacilli, the QS system B. licheniformis has not been investigated in detail, and its QSM (ComX pheromone) has not been identified. Given the importance of this antagonistic bacterium as an industrial workhorse, this study was aimed to elucidate B. licheniformis NCIMB-8874 QS. The results obtained from bioinformatics studies on the whole genome sequence of this strain confirmed the presence of essential quorum sensing-related genes. Although polymorphism was verified in three proteins of this cluster, ComQ, precursor-ComX and ComP, the transcription factor ComA was confirmed as the most conserved protein. The cell-cell communication of B. licheniformis NCIMB-8874 was investigated through further elucidation of the ComX pheromone as 13-amino acid ...
Acylhomoserine lactone (AHL) analogues in which the amide function is replaced by a triazole group were synthesized and evaluated for their effect on quorum sensing (QS) and biofilm formation in Burkholderia cenocepacia and Pseudomonas aeruginosa. In addition, the influence of the length of the acyl-mimicking chain was investigated. The compounds showed selectivity between two different AHL QS systems. 3-(1H-1,2,3-Triazol-1-yl)dihydrofuran-2(3H)-ones, in which the 4-substituent best resembled the acyl chain of the native AHL molecule exhibited significant QS agonistic and antagonistic activities. Replacing this aliphatic substituent by a phenyl-containing moiety resulted in active inhibitors of QS. The most active compounds showed biofilm inhibitory as well as biofilm eradicating activities in both test organisms. ...
Quorum sensing is a mechanism whereby bacteria respond to specific signals and exhibit group behavior, which at high cell density may include virulence factors associated with disease. At low cell density, bacteria act as individuals and may not be as virulent. Most quorum inhibitors identified to date compete with the native signal and once the inhibitor is removed, signaling can resume. Here, we show that a dissolved metal, cadmium, disrupts the quorum sensing proteins, which requires the bacteria to replace the damaged proteins in order to resume quorum sensing. This represents a new strategy for disrupting bacterial signaling ...
Princeton University. Biographical Sketch Not long ago, most biologists thought bacteria were asocial creatures. Now, it is clear that bacteria communicate within and between species using chemical languages that enable them to coordinately regulate gene expression and synchronize group behaviors. Bacterial communication, called quorum sensing, is a census-taking process that allows bacteria to wait until they have achieved a critical cell number before embarking on processes such as virulence, biofilm formation, sporulation and mating. Quorum sensing processes are typically ones that are not effective if undertaken by a single bacterium acting alone but become successful when a group of cells acts in concert.. Bonnie Bassler has been studying quorum sensing for nearly 20 years. She and her coworkers have shown that bacteria are multi-lingual: They have unique languages for communicating within their own species, and they also possess a common language for communication between species. Bassler ...
Quorum responses provide a means for group-living animals to integrate and filter disparate social information to produce accurate and coherent group decisions. A quorum response may be defined as a steep increase in the probability of group members
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Every mammal on the planet is colonized with E. coli ( 1 ), as well as cold-blooded animals (e.g., fish) at an appropriately warm temperature ( 2 ). We estimate there are 1021 E. coli cells in the human population alone. E. coli is frequently the first bacterium to colonize human infants and is a lifelong colonizer of adults ( 3 ). E. coli is arguably the best understood of all model organisms ( 4 ). Yet the essence of how E. coli colonizes and/or causes disease is still not completely understood. Certainly, innate immunity, adaptive immunity, and bacterial cell-to-cell communication play important roles in modulating the populations of the 500-1000 different commensal species in the intestine ( 5 - 11 ); however, these topics will not be a focus of this chapter. We have reviewed the mucus layer as habitat for E. coli to colonize the intestine, aspects of E. coli physiology that enable its success, and the model systems employed for colonization research ( 12 - 14 ). Here, we focus on E. coli metabolism
The goal of this research is to understand the molecular mechanisms underlying quorum sensing, a cell-cell communication process that allows bacteria to coordin...
Results We assessed 52 participants for eligibility. Eight were excluded. 27 smokers were allocated to the group behaviour intervention and vanrenicline, another 25 smokers were allocated to the control group; More participants had quit at 4 weeks in the group behaviour intervention compared to the control group: 70.3% vs 52%, p,0.05; 62.9% vs 32% at 12 weeks, p,0.05; Reported quit rates remained high difference at 6 months, but there was some uncertainty about between group differences because of incomplete follow up.. ...
Quorum sensing is a system used by bacteria to detect population density and respond. This communication is carried out by molecular signals produced and released by the bacteria. The signals disperse to nearby individuals and eventually lead to a pathway that causes induction of more signal production in those neighbors, in addition to other desired genes[1]. The more dense the population, the higher concentration the signal is. This circuit creates a positive feedback loop that causes the population to work in sync. In nature, bacteria can use quorum sensing for functions such as bioluminescence[2], virulence[3], and biofilm formation[4]. Because quorum sensing is such an important aspect of biofilm formation, it is a valuable topic of research for disease prevention and treatment. In addition, QS has various applications in synthetic biology since QS systems can be engineered to accomplish useful tasks. ...
Researchers from the Institute of Food Research and the University of East Anglia have discovered how the beneficial bacteria in our guts communicate
Highly virulent enterococcal strains have a pathogenicity island within their genome that encodes, among other traits, a cytolytic toxin that uses a quorum-sensing mechanism to affect autoinduction. Coburn et al. (see the Perspective by Garsin) show that the bacterium actively secretes two components, an autoinducer and an anti-autoinducer. In the absence of target cells, these two interact and prevent the autoinducer from feeding back to induce high-level expression of the cytolysin. In the presence of the target cell, however, the anti-autoinducer binds to the target cell and allows the autoinducer to accumulate to the threshold level required for quorum induction of the cytolysin operon. The anti-autoinducer is itself a toxin component and effectively tags the target for destruction. P. S. Coburn, C. M. Pillar, B. D. Jett, W. Haas, M. S. Gilmore, Enterococcus faecalis senses target cells and in response expresses cytolysin. Science 306, 2270-2272 (2004). [Abstract] [Full Text]. D. A. Garsin, ...
When encountering a new host, every potential microbial pathogen can stay, acquire nutrients, colonize and then seek another host. Alternatively the pathogen could express its full battery of virulence factors, and invade the host. The successful attack of a host is now understood to be a communal process called Quorum Sensing (QS).
Quorum sensing is a wide-spread mode of cell-cell communication among bacteria in which cells release a signalling substance at a low rate. The concentration of this substance allows the bacteria to gain information about population size or spatial confinement. We consider a model for N cells which communicate with each other via a signalling substance in a diffusive medium with a background flow. The model consists of an initial boundary value problem for a parabolic PDE describing the exterior concentration u of the signalling substance, coupled with N ODEs for the masses ai of the substance within each cell. The cells are balls of radius R in R3, and under some scaling assumptions we formally derive an effective system of N ODEs describing the behaviour of the cells. The reduced system is then used to study the effect of flow on communication in general, and in particular for a number of geometric configurations.
Pathogenic bacteria are proliferating due to chemical chit chat called quorum sensing. Researchers are scrambling for a way to silence them.
Two hypotheses, termed quorum sensing (QS) and diffusion sensing (DS), have been suggested as competing explanations for why bacterial cells use the local concentration of small molecules to regulate numerous extracellular behaviours. Here, we show that: (i) although there are important differences between QS and DS, they are not diametrically opposed; (ii) empirical attempts to distinguish between QS and DS are misguided and will lead to confusion; (iii) the fundamental distinction is not between QS and DS, but whether or not the trait being examined is social; (iv) empirical data are consistent with both social interactions and a role of diffusion; (v) alternate hypotheses, such as efficiency sensing (ES), are not required to unite QS and DS. More generally, work in this area illustrates how the use of jargon can obscure the underlying concepts and key questions.
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Curriculum Design and Instruction to Teach Roberts Rules of Order: Quorum: Order of Business and Related Concepts: Part XI: Author: Char
The Commonwealth Zoning board meeting set for yesterday at the Pedro P. Tenorio Multipurpose Center in Susupe was cancelled due to lack of quorum.
Many bacteria use population density to control gene expression via quorum sensing. In Vibrio cholerae, quorum sensing coordinates virulence, biofilm formation, and DNA uptake by natural competence. The transcription factors AphA and HapR, expressed at low and high cell density respectively, play a key role. In particular, AphA triggers the entire virulence cascade upon host colonisation. In this work we have mapped genome-wide DNA binding by AphA. We show that AphA is versatile, exhibiting distinct modes of DNA binding and promoter regulation. Unexpectedly, whilst HapR is known to induce natural competence, we demonstrate that AphA also intervenes. Most notably, AphA is a direct repressor of tfoX, the master activator of competence. Hence, production of AphA markedly suppressed DNA uptake; an effect largely circumvented by ectopic expression of tfoX. Our observations suggest dual regulation of competence. At low cell density AphA is a master repressor whilst HapR activates the process at high ...
END+. " title="Click here to sort" href="javascript:__doPostBack(ctl01$TemplateBody$WebPartManager1$gwpcieLinks$cieLinks$ResultsGrid$Grid1$ctl00$ctl02$ctl01$btn_ResultsGrid_2_Sort_,h4>Digital_Options:,/h4>,p>+CASE_WHEN_LinkAmazon_IS_NULL_OR_LinkAmazon=_THEN__ELSE_,a_href=+LinkAmazon+_title=Purchase_at_Amazon>,img_src=/images/Products/linkAmazon.png_class=bkLink/>,/a>_END+CASE_WHEN_LinkIbook_IS_NULL_OR_LinkIbook=_THEN__ELSE_,a_href=+LinkIbook+_title=Purchase_iBook>,img_src=/images/Products/linkIbook.png_class=bkLink/>,/a>_END+CASE_WHEN_LinkOnline_IS_NULL_OR_LinkOnline=_THEN__ELSE_,a_href=+LinkOnline+_title=Purchase_eBook>,img_src=/images/Products/linkOnline.png_class=bkLink/>,/a>_END+,/p ...
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Mr. Roger Carff is a research associate at the Florida Institute for Human and Machine Cognition (IHMC). He received his B.S. and Masters in Computer Science from UWF.. Mr. Carff started working for the Institute as a research assistant in 1992 on Project Quorum. His involvement in the project included developing a distributed network of mail servers that could communicate over various mediums (Modem, TCP/IP, SNA) to each other and quorum school clients. Also, he developed LLCorreo an e-mail tool for children designed to run on very low end DOS machines.. After the Project Quorum ended Mr. Carff has worked on multiple projects for IHMC including: CmapTools, TSAS, and Software Agents. Mr. Carffs research interests include user interfaces, Java, 3D simulations, and distributed computing. His personal interests include his family, church, coaching soccer and tee-ball, LEGOs, and computer games.. ...
January 08, 2013 at 13:24 MST. Upgraded to Rails 3.2.11 January 08, 2013 at 11:34 MST. Removed code duplication. December 17, 2012 at 15:00 MST. Added rack maintenance mode middleware. December 17, 2012 at 12:59 MST. Corrected CKFinder url path. December 17, 2012 at 12:27 MST. Updated config/application.rb December 17, 2012 at 12:08 MST. Merge branch master of github.com:ncgr/lis_species December 17, 2012 at 12:02 MST. Added maintenance mode rack middleware. December 17, 2012 at 11:32 MST. Change title to 503. December 17, 2012 at 11:25 MST. Added maintenance mode rack middleware. December 06, 2012 at 16:37 MST. Upgraded to Quorum v0.8.1 November 30, 2012 at 15:09 MST. Updated to Quorum v0.8.0 -- install as gem. November 29, 2012 at 10:32 MST. Removed href=# from anchors. November 28, 2012 at 15:25 MST. Updated gems. November 27, 2012 at 14:04 MST. Updated Quorum search url for next release. November 13, 2012 at 15:51 MST. Retain numeric filters when changing views. November 13, 2012 at ...
Our project harnesses the use of quorum sensing to prevent bacteria from activating pathogenic factors triggered by AHLs. We developed a model system with Allivibrio fisheri. A. fisheri luminesces when activated by AHLs, which is a much safer alternative to pathogenic bacteria. We grew up our E. coli with Vibrio fisheri, and showed that the recombinant E. coli could detect V. fisheris AHLs, and inhibit V. fisheri from activating its quorum response genes by not producing light.The detection system then secretes factors that reduce the concentration of AHLs in the environment, thereby inhibiting the bacteria that use AHLs from communicating with each other. This is useful in preventing pathology from bacteria. When a threshold level of AHLs is reached in pathogenic bacteria, the signals activate transcription of pathogenic factors such as biofilm formation and host invasion signals (Raffa et al, 2005). We propose that disrupting the AHLs will inhibit these bacteria from creating biofilms or ...
It is generally assumed that microorganisms synthesize, release, detect and respond to small signaling hormone-like molecules. These molecules are used for a process termed
The only difference between the two signal receivers is a different YFP reporter protein. A quick rundown of how it will work: we will stick some sort of promoter in front of the BBa_F1610 in order to produce constitutive expression of HSL. We can play around with which promoter we want to use in order to tweak the sensitivity of the system. This HSL will normally diffuse quickly. Meanwhile, there is constitutive expression of the protein produced after transcription and translation of luxR (called R from now on) is continually going on in the bacteria with the receiver. The HSL will bind to the R and these bound complexes will dimerize and activate transcription of the YFP reporter. However, normally the concentration of HSL is too low and the equilibrium highly favors unbound HSL and R. In areas of high cell concentration, the concentration of HSL will be great enough to shift the equilibrium toward the bound complex. This bound complex will then activate the transcription of the reporter ...
In research published today in the journal Chemistry & Biology, Blackwell changed key building blocks in these protein targets one by one. "If that part of the protein is important, the change will have a significant effect on our signals activity," she explains.. In the study performed with recent graduate students Joseph Gerdt and Christine McInnis, Blackwell expected to knock out, or deactivate, the signals by making these point modifications. Sometimes, however, the changes actually converted an activation signal into a deactivation signal, or vice versa.. "It was surprising that making minor tweaks, very subtle changes, to the protein would convert a compound from an inhibitor to an activator, or turn an activator into an inhibitor," she says. "That shows that small-molecule control of quorum sensing is very finely tuned, much more than we even expected.". Quorum sensing is present in many, but not all, bacteria, and its advantage is clear. A few hundred bacteria cannot hope to overwhelm ...
A group of researchers led by Andrea Cavalleri at the Max Planck Institute for Structure and Dynamics of Matter (MPSD) in Hamburg has demonstrated a new method enabling precise measurements of the interatomic forces that hold crystalline solids together. The paper Probing the Interatomic Potential of Solids by Strong-Field Nonlinear Phononics, published online in Nature, explains how a terahertz-frequency laser pulse can drive very large deformations of the crystal. ...
So, are the quorum sensing (see: Prokaryote Colonies) molecules lipids? If so, perhaps they originally evolved as metabolic energy storing molecules which diffused across the membrane and thereby served the secondary function of lubricating the cells motion. As the concentration of these molecules built up outside the cell, the molecules still being produced inside the cell would have had more difficulty diffusing across the membrane because of the reduced concentration gradient. This build-up of the lipid quorum sensing molecules inside the cell could then have had an effect on the cells metabolism without the necessity of an intervening receptor ...
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Trying to influence Congress is hard work. You have to know who cares about what issues so you approach the right people. It also helps to know who has the power to actually make waves so you dont waste your time with ineffective members.