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1

Caffeine as a potential quorum sensing inhibitor.  

PubMed

Quorum sensing enables bacteria to control the gene expression in response to the cell density. It regulates a variety of bacterial physiological functions such as biofilm formation, bioluminescence, virulence factors and swarming which has been shown contribute to bacterial pathogenesis. The use of quorum sensing inhibitor would be of particular interest in treating bacterial pathogenicity and infections. In this work, we have tested caffeine as quorum sensing inhibitor by using Chromobacterium violaceum CV026 as a biosensor. We verified that caffeine did not degrade the N-acyl homoserine lactones tested. In this work, it is shown that caffeine could inhibit N-acyl homoserine lactone production and swarming of a human opportunistic pathogen, namely Pseudomonas aeruginosa PA01. To the best of our knowledge, this is the first documentation providing evidence on the presence of anti-quorum sensing activity in caffeine. Our work will allow caffeine to be explored as anti-infective drugs. PMID:23598500

Norizan, Siti Nur Maisarah; Yin, Wai-Fong; Chan, Kok-Gan

2013-01-01

2

Targeting Staphylococcus aureus Quorum Sensing with Nonpeptidic Small Molecule Inhibitors  

PubMed Central

A series of 3-oxo-C12-HSL, tetramic acid, and tetronic acid analogues were synthesized to gain insights into the structural requirements for quorum sensing inhibition in Staphylococcus aureus. Compounds active against agr were noncompetitive inhibitors of the autoinducing peptide (AIP) activated AgrC receptor, by altering the activation efficacy of the cognate AIP-1. They appeared to act as negative allosteric modulators and are exemplified by 3-tetradecanoyltetronic acid 17, which reduced nasal cell colonization and arthritis in a murine infection model. PMID:24592914

2014-01-01

3

Quorum Sensing  

Microsoft Academic Search

Bacteria use small molecule signals to communicate with each other. Intercellular signalling at high population cell densities\\u000a is termed quorum sensing and explains many aspects of bacterial physiology observed in single species cultures entering stationary\\u000a phase in the laboratory. Quorum sensing is used by diverse species to control a multitude of phenotypic traits that often\\u000a include virulence factors (e.g., exoenzymes)

Simon Swift; Maria C. Rowe; Malavika Kamath

4

Computer-Aided Identification of Recognized Drugs as Pseudomonas aeruginosa Quorum-Sensing Inhibitors  

Microsoft Academic Search

Attenuation of Pseudomonas aeruginosa virulence by the use of small-molecule quorum-sensing inhibitors (referred to as the antipathogenic drug principle) is likely to play a role in future treatment strategies for chronic infections. In this study, structure-based virtual screening was used in a search for putative quorum- sensing inhibitors from a database comprising approved drugs and natural compounds. The database was

Liang Yang; Morten Theil Rybtke; Tim Holm Jakobsen; Morten Hentzer; Thomas Bjarnsholt; Michael Givskov; Tim Tolker-Nielsen

2009-01-01

5

Computer-Aided Identification of Recognized Drugs as Pseudomonas aeruginosa Quorum-Sensing Inhibitors? †  

PubMed Central

Attenuation of Pseudomonas aeruginosa virulence by the use of small-molecule quorum-sensing inhibitors (referred to as the antipathogenic drug principle) is likely to play a role in future treatment strategies for chronic infections. In this study, structure-based virtual screening was used in a search for putative quorum-sensing inhibitors from a database comprising approved drugs and natural compounds. The database was built from compounds which showed structural similarities to previously reported quorum-sensing inhibitors, the ligand of the P. aeruginosa quorum-sensing receptor LasR, and a quorum-sensing receptor agonist. Six top-ranking compounds, all recognized drugs, were identified and tested for quorum-sensing-inhibitory activity. Three compounds, salicylic acid, nifuroxazide, and chlorzoxazone, showed significant inhibition of quorum-sensing-regulated gene expression and related phenotypes in a dose-dependent manner. These results suggest that the identified compounds have the potential to be used as antipathogenic drugs. Furthermore, the results indicate that structure-based virtual screening is an efficient tool in the search for novel compounds to combat bacterial infections. PMID:19364871

Yang, Liang; Rybtke, Morten Theil; Jakobsen, Tim Holm; Hentzer, Morten; Bjarnsholt, Thomas; Givskov, Michael; Tolker-Nielsen, Tim

2009-01-01

6

Quorum sensing inhibitors as anti-biofilm agents.  

PubMed

Biofilms are microbial sessile communities characterized by cells that are attached to a substratum or interface or to each other, are embedded in a self-produced matrix of extracellular polymeric substances and exhibit an altered phenotype compared to planktonic cells. Biofilms are estimated to be associated with 80% of microbial infections and it is currently common knowledge that growth of micro-organisms in biofilms can enhance their resistance to antimicrobial agents. As a consequence antimicrobial therapy often fails to eradicate biofilms from the site of infection. For this reason, innovative anti-biofilm agents with novel targets and modes of action are needed. One alternative approach is targeting the bacterial communication system (quorum sensing, QS). QS is a process by which bacteria produce and detect signal molecules and thereby coordinate their behavior in a cell-density dependent manner. Three main QS systems can be distinguished: the acylhomoserine lactone (AHL) QS system in Gram-negative bacteria, the autoinducing peptide (AIP) QS system in Gram-positive bacteria and the autoinducer-2 (AI-2) QS system in both Gram-negative and -positive bacteria. Although much remains to be learned about the involvement of QS in biofilm formation, maintenance, and dispersal, QS inhibitors (QSI) have been proposed as promising antibiofilm agents. In this article we will give an overview of QS inhibitors which have been shown to play a role in biofilm formation and/or maturation. PMID:25189863

Brackman, Gilles; Coenye, Tom

2015-01-01

7

Food as a Source for Quorum Sensing Inhibitors: Iberin from Horseradish Revealed as a Quorum Sensing Inhibitor of Pseudomonas aeruginosa  

PubMed Central

Foods with health-promoting effects beyond nutritional values have been gaining increasing research focus in recent years, although not much has been published on this subject in relation to bacterial infections. With respect to treatment, a novel antimicrobial strategy, which is expected to transcend problems with selective pressures for antibiotic resistance, is to interrupt bacterial communication, also known as quorum sensing (QS), by means of signal antagonists, the so-called QS inhibitors (QSIs). Furthermore, QSI agents offer a potential solution to the deficiencies associated with use of traditional antibiotics to treat infections caused by bacterial biofilms and multidrug-resistant bacteria. Several QSIs of natural origin have been identified, and in this study, several common food products and plants were extracted and screened for QSI activity in an attempt to isolate and characterize previously unknown QSI compounds active against the common opportunistic pathogen Pseudomonas aeruginosa. Several extracts displayed activity, but horseradish exhibited the highest activity. Chromatographic separation led to the isolation of a potent QSI compound that was identified by liquid chromatography-diode array detector-mass spectrometry (LC-DAD-MS) and nuclear magnetic resonance (NMR) spectroscopy as iberin—an isothiocyanate produced by many members of the Brassicaceae family. Real-time PCR (RT-PCR) and DNA microarray studies showed that iberin specifically blocks expression of QS-regulated genes in P. aeruginosa. PMID:22286987

Jakobsen, Tim Holm; Bragason, Steinn Kristinn; Phipps, Richard Kerry; Christensen, Louise Dahl; van Gennip, Maria; Alhede, Morten; Skindersoe, Mette; Larsen, Thomas Ostenfeld; Høiby, Niels; Bjarnsholt, Thomas

2012-01-01

8

Identification of poultry meat-derived fatty acids functioning as quorum sensing signal inhibitors of autoinducer-2 (AI-2)  

Technology Transfer Automated Retrieval System (TEKTRAN)

Autoinducer-2 (AI-2) is a compound that plays a key role in bacterial cell-to-cell communication (quorum sensing). Previous research has shown certain food matrices inhibit this signaling compound. Using the reporter strain, Vibrio harveyi BB170, quorum sensing inhibitors contained in poultry meat...

9

Targeting quorum sensing in Pseudomonas aeruginosa biofilms: current and emerging inhibitors.  

PubMed

Bacterial resistance to conventional antibiotics combined with an increasing acknowledgement of the role of biofilms in chronic infections has led to a growing interest in new antimicrobial strategies that target the biofilm mode of growth. In the aggregated biofilm mode, cell-to-cell communication systems involved in the process known as quorum sensing regulate coordinated expression of virulence with immune shielding mechanisms and antibiotic resistance. For two decades, the potential of interference with quorum sensing by small chemical compounds has been investigated with the aim of developing alternative antibacterial strategies. Here, we review state of the art research of quorum sensing inhibitors against the opportunistic human pathogen Pseudomonas aeruginosa, which is found in a number of biofilm-associated infections and identified as the predominant organism infecting the lungs of cystic fibrosis patients. PMID:23841636

Jakobsen, Tim Holm; Bjarnsholt, Thomas; Jensen, Peter Østrup; Givskov, Michael; Høiby, Niels

2013-07-01

10

Quorum Sensing Inhibitors for Staphylococcus aureus from Italian Medicinal Plants  

PubMed Central

Morbidity and mortality estimates due to methicillin-resistant Staphylococcus aureus (MRSA) infections continue to rise. Therapeutic options are limited by antibiotic resistance. Anti-pathogenic compounds, which inhibit quorum sensing (QS) pathways, may be a useful alternative to antibiotics. Staphylococcal QS is encoded by the agr locus and is responsible for the production of ?-hemolysin. Quantification of ?-hemolysin found in culture supernatants permits the analysis of agr activity at the translational, rather than transcriptional, level. We employed RP-HPLC techniques to investigate the anti-QS activity of 168 extracts from 104 Italian plants through quantification of ?-hemolysin. Extracts from three medicinal plants (Ballota nigra, Castanea sativa, and Sambucus ebulus) exhibited a dose-dependent response in the production of ?-hemolysin, indicating strong anti-QS activity in a pathogenic MRSA isolate. PMID:20645243

Quave, Cassandra L.; Plano, Lisa R.W.; Bennett, Bradley C.

2010-01-01

11

Quorum Sensing and Phytochemicals  

PubMed Central

Most infectious diseases are caused by bacteria, which proliferate within quorum sensing (QS)-mediated biofilms. Efforts to block QS in bacteria and disrupt biofilms have enabled the identification of bioactive molecules that are also produced by plants. This mini review primarily focuses on natural QS inhibitors, which display potential for treating bacterial infections and also enhance the safety of food supply. PMID:23774835

Nazzaro, Filomena; Fratianni, Florinda; Coppola, Raffaele

2013-01-01

12

Structural understanding of quorum-sensing inhibitors by molecular modeling study in Pseudomonas aeruginosa  

Microsoft Academic Search

Inhibitors of 3OC12, an initial signal molecule of the quorum sensing (QS) signaling cascade in Pseudomonas aeruginosa have been developed. Eight inhibitor candidates were synthesized by substituting the head part of 3-oxododecanoyl-homoserine\\u000a lactone (3OC12) with different aromatic rings, and their docking poses and scores (binding energies) were predicted by in\\u000a silico modeling study. All compounds gave better docking scores than

Cheoljin Kim; Jaeeun Kim; Hyung-Yeon Park; Joon-Hee Lee; Hee-Jin Park; Chan Kyung Kim; Jeyong Yoon

2009-01-01

13

Bacterial quorum sensing inhibitors: attractive alternatives for control of infectious pathogens showing multiple drug resistance.  

PubMed

Quorum sensing (QS) is a bacterial communication process that depends on the bacterial population density. It involves small diffusible signaling molecules which activate the expression of myriad genes that control diverse array of functions like bioluminescence, virulence, biofilm formation, sporulation, to name a few. Since QS is responsible for virulence in the clinically relevant bacteria, inhibition of QS appears to be a promising strategy to control these pathogenic bacteria. With indiscriminate use of antibiotics, there has been an alarming increase in the number of antibiotic resistant pathogens. Antibiotics are no longer the magic bullets they were once thought to be and therefore there is a need for development of new antibiotics and/or other novel strategies to combat the infections caused by multidrug resistant organisms. Quorum sensing inhibition or quorum quenching has been pursued as one of such novel strategies. While antibiotics kill or slow down the growth of bacteria, quorum sensing inhibitors (QSIs) or quorum quenchers (QQs) attenuate bacterial virulence. A large body of work on QS has been carried out in deadly pathogens like Pseudomonas aeruginosa, Staphylococcus aureus, Vibrio fischeri, V. harveyi, Escherichia coli and V. cholerae etc to unravel the mechanisms of QS as well as identify and study QSIs. This review describes various aspects of QS, QSI, different model systems to study these phenomena and recent patents on various QSIs. It suggests QSIs as attractive alternatives for controlling human, animal and plant pathogens and their utility in agriculture and other industries. PMID:23394143

Bhardwaj, Ashima K; Vinothkumar, Kittappa; Rajpara, Neha

2013-04-01

14

In silico investigation of lactone and thiolactone inhibitors in bacterial quorum sensing using molecular modeling  

E-print Network

In the present study, the origin of the anti-quorum sensing (QS) activities of several members of a recently synthesized and in vitro tested class of lactone and thiolactone based inhibitors were computationally investigated. Docking and molecular dynamic (MD) simulations and binding free energy calculations were carried out to reveal the exact binding and inhibitory profiles of these compounds. The higher in vitro activity of the lactone series relative to their thiolactone isosteres was verified based on estimating the binding energies, the docking scores and monitoring the stability of the complexes produced in the MD simulations. The strong electrostatic contribution to the binding energies may be responsible for the higher inhibitory activity of the lactone with respect to the thiolactone series. The results of this study help to understand the anti-QS properties of lactone-based inhibitors and provide important information that may assist in the synthesis of novel QS inhibitors.

Ahmed, Marawan; Wang, Feng; Palombo, Enzo A

2013-01-01

15

Production of Quorum Sensing Inhibitors in Growing Onion Bulbs Infected with Pseudomonas aeruginosa E (HQ324110)  

PubMed Central

Eighteen organic compounds were present in growing onion bulbs cultivar Giza 6 infected with P. aeruginosa, but only fourteen of them are present in dry infected onion bulbs; however, four compounds were missing in dry onion. The missing compounds in dry infected onion bulbs are pantolactone, 4,5-dihydro-4,5-dimethylfuran-2(3H)-one, myristic acid, and linoleic acid. All of them were detected in growing onion (living cell) during Pseudomonas aeruginosa infection, and it is hypothesized that it may be produced by plants and act as defence system. Pantolactone and myristic acid were selected to explore their effects on growth and virulence factors of Pseudomonas aeruginosa. Exogenous application of pantolactone and myristic acid significantly inhibited pyocyanin production, protease, and lipase and polygalacturonase activity but did not have any significant effects on bacterial growth. The inhibition of virulence factors without reduction in bacterial growth may be providing strong support that these chemical molecules are general quorum sensing inhibitors than an antibacterial effect. Disruption of quorum sensing of pathogen indicates that this new approach has potential in fighting bacterial infections in human and plants. PMID:23724316

Abd-Alla, Mohamed H.; Bashandy, Shymaa R.

2012-01-01

16

QUORUM SENSING IN BACTERIA  

Microsoft Academic Search

? Abstract Quorum sensing is the regulation of gene expression in response to fluctuations in cell-population density. Quorum sensing bacteria produce and release chemical signal molecules called autoinducers that increase in concentration as a function of cell density. The detection of a minimal threshold stimulatory con- centration of an autoinducer leads to an alteration in gene expression. Gram-positive and Gram-negative

Melissa B. Miller; Bonnie L. Bassler

2001-01-01

17

Identification of Five Structurally Unrelated Quorum-Sensing Inhibitors of Pseudomonas aeruginosa from a Natural-Derivative Database  

PubMed Central

Bacteria communicate by means of small signal molecules in a process termed quorum sensing (QS). QS enables bacteria to organize their activities at the population level, including the coordinated secretion of virulence factors. Certain small-molecule compounds, known as quorum-sensing inhibitors (QSIs), have been shown to effectively block QS and subsequently attenuate the virulence of Pseudomonas aeruginosa, as well as increasing its susceptibility to both antibiotics and the immune system. In this study, a structure-based virtual screening (SB-VS) approach was used for the discovery of novel QSI candidates. Three-dimensional structures of 3,040 natural compounds and their derivatives were obtained, after which molecular docking was performed using the QS receptor LasR as a target. Based on docking scores and molecular masses, 22 compounds were purchased to determine their efficacies as quorum-sensing inhibitors. Using a live reporter assay for quorum sensing, 5 compounds were found to be able to inhibit QS-regulated gene expression in P. aeruginosa in a dose-dependent manner. The most promising compound, G1, was evaluated by isobaric tag for relative and absolute quantitation (iTRAQ)-based proteomic analysis, and it was found to significantly affect the abundance of 46 proteins (19 were upregulated; 27 were downregulated) in P. aeruginosa PAO1. It specifically reduced the expression of several quorum-sensing-regulated virulence factors, such as protease IV, chitinase, and pyoverdine synthetases. G1 was also able to reduce extracellular DNA release and inhibited the secretion of the virulence factor, elastase, whose expression is regulated by LasR. These results demonstrate the utility of SB-VS for the discovery of target-specific QSIs. PMID:24002091

Tan, Sean Yang-Yi; Chua, Song-Lin; Chen, Yicai; Rice, Scott A.; Kjelleberg, Staffan; Nielsen, Thomas E.; Givskov, Michael

2013-01-01

18

Screening of traditional Chinese medicinal plants for quorum-sensing inhibitors activity.  

PubMed

The misuse of antibiotics has contributed to widespread development of antimicrobial resistance among clinically significant bacterial species. Alternative approaches other than those using antibiotics are needed in the fight against infectious diseases. Quorum sensing (QS) is an intercellular signaling and gene regulatory mechanism, which is used by a number of opportunistic pathogenic bacteria in determining virulence gene expression. The study of QS may yield another strategy for disease control by interference with QS signals. Scientific research on complementary therapies such as traditional Chinese medicine (TCM) has focused mainly on its antibacterial properties. To test for anti-QS activity, 10 TCM herbs were screened using two biomonitor strains, Chromobacterium violaceum CV026 and Pseudomonas aeruginosa PA01. Interference with violacein (purple pigment) production in CV026 (exogenously supplied with homoserine lactone signals), and swarming in PA01, both QS-regulated phenomena, was used as indication of anti-QS activity. Eight of the selected TCM (80%) yielded QS inhibitors: Prunus armeniaca, Prunella vulgaris, Nelumbo nucifera, Panax notoginseng (root and flower), Punica granatum, Areca catechu, and Imperata cylindrica. Compounds that interfere with QS are present in TCM herbs and these medicines may be a rich source of compounds to combat pathogenic bacteria and reduce the development of antibiotic resistance. PMID:21439518

Koh, Khee Hoon; Tham, Foong-Yee

2011-04-01

19

Imidazolines as Non-Classical Bioisosteres of N-Acyl Homoserine Lactones and Quorum Sensing Inhibitors  

PubMed Central

A series of selected 2-substituted imidazolines were synthesized in moderate to excellent yields by a modification of protocols reported in the literature. They were evaluated as potential non-classical bioisosteres of AHL with the aim of counteracting bacterial pathogenicity. Imidazolines 18a, 18e and 18f at various concentrations reduced the violacein production by Chromobacterium violaceum, suggesting an anti-quorum sensing profile against Gram-negative bacteria. Imidazoline 18b did not affect the production of violacein, but had a bacteriostatic effect at 100 ?M and a bactericidal effect at 1 mM. Imidazoline 18a bearing a hexyl phenoxy moiety was the most active compound of the series, rendering a 72% inhibitory effect of quorum sensing at 100 ?M. Imidazoline 18f bearing a phenyl nonamide substituent presented an inhibitory effect on quorum sensing at a very low concentration (1 nM), with a reduction percentage of 28%. This compound showed an irregular performance, decreasing inhibition at concentrations higher than 10 ?M, until reaching 100 ?M, at which concentration it increased the inhibitory effect with a 49% reduction percentage. When evaluated on Serratia marcescens, compound 18f inhibited the production of prodigiosin by 40% at 100 ?M. PMID:22408391

Reyes-Arellano, Alicia; Bucio-Cano, Alejandro; Montenegro-Sustaita, Mabel; Curiel-Quesada, Everardo; Salgado-Zamora, Héctor

2012-01-01

20

At a Supra-Physiological Concentration, Human Sexual Hormones Act as Quorum-Sensing Inhibitors  

PubMed Central

N-Acylhomoserine lactone (AHL)-mediated quorum-sensing (QS) regulates virulence functions in plant and animal pathogens such as Agrobacterium tumefaciens and Pseudomonas aeruginosa. A chemolibrary of more than 3500 compounds was screened using two bacterial AHL-biosensors to identify QS-inhibitors (QSIs). The purity and structure of 15 QSIs selected through this screening were verified using HPLC MS/MS tools and their activity tested on the A. tumefaciens and P. aeruginosa bacterial models. The IC50 value of the identified QSIs ranged from 2.5 to 90 µg/ml, values that are in the same range as those reported for the previously identified QSI 4-nitropyridine-N-oxide (IC50 24 µg/ml). Under the tested culture conditions, most of the identified QSIs did not exhibit bacteriostatic or bactericidal activities. One third of the tested QSIs, including the plant compound hordenine and the human sexual hormone estrone, decreased the frequency of the QS-regulated horizontal transfer of the tumor-inducing (Ti) plasmid in A. tumefaciens. Hordenine, estrone as well as its structural relatives estriol and estradiol, also decreased AHL accumulation and the expression of six QS-regulated genes (lasI, lasR, lasB, rhlI, rhlR, and rhlA) in cultures of the opportunist pathogen P. aeruginosa. Moreover, the ectopic expression of the AHL-receptors RhlR and LasR of P. aeruginosa in E. coli showed that their gene-regulatory activity was affected by the QSIs. Finally, modeling of the structural interactions between the human hormones and AHL-receptors LasR of P. aeruginosa and TraR of A. tumefaciens confirmed the competitive binding capability of the human sexual hormones. This work indicates potential interferences between bacterial and eukaryotic hormonal communications. PMID:24376718

Beury-Cirou, Amélie; Tannières, Mélanie; Minard, Corinne; Soulère, Laurent; Rasamiravaka, Tsiry; Dodd, Robert H.; Queneau, Yves; Dessaux, Yves; Guillou, Catherine; Vandeputte, Olivier M.; Faure, Denis

2013-01-01

21

Quorum Sensing in Staphylococci  

Microsoft Academic Search

The staphylococcal agr locus encodes a quorum sensing (QS) system that controls the expression of virulence and other accessory genes by a classical two-component signaling module. Like QS modalities in other Gram-positive bacteria, agr encodes an autoactivating peptide (AIP) that is the inducing ligand for AgrC, the agr signal receptor. Unlike other such systems, agr variants have arisen that show

Richard P. Novick; Edward Geisinger

2008-01-01

22

Screening of SdiA inhibitors from Melia dubia seeds extracts towards the hold back of uropathogenic E.coli quorum sensing-regulated factors.  

PubMed

Plants have always been a supreme source of drugs and India is endowed with a wide variety of them with high medicinal values. The Quorum Sensing (QS) quenching efficiency of various solvent extracts of Melia dubia seeds was investigated against uropathogenic Escherichia coli (UPEC) to screen the competitive inhibitor of SdiA, a transcriptional activator of quorum sensing in E. coli. In this study, potentiality of five different extracts of Melia dubia seeds for quorum sensing inhibitory activity was investigated against uropathogenic Escherichia coli (UPEC). Assays such as cell density, swarming motility, protein, protease, hemolysis, hemagglutination, hydrophobicity and biofilm inhibition were performed. Biofilm, hemolysis and swarming motility were found to be inhibited by 92.1%, 20.9 % and 48.52% respectively, when the medium was supplemented with 30 mg/ml of the ethanolic extract. GC-MS spectrum of the ethanolic extract showed an array of 27 structurally unlinked compounds with natural ligand C8HSL. The docking against QS transcriptional regulator SdiA was predicted by in silico studies and the ligand C6 showed significant activity with -10.8 GScore. In vitro and in silico docking analysis showed fairly a good correlation, suggesting that the ethanolic extract showed potency to attenuate quorum sensing of uropathogenic E. coli. Further studies by in vitro and in vivo strategies are necessary to foresee the quorum quenching effect of the ligands. PMID:23210902

Ravichandiran, Vinothkannan; Shanmugam, Karthi; Solomon, Adline Princy

2013-09-01

23

Polyhydroxyanthraquinones as quorum sensing inhibitors from the guttates of Penicillium restrictum and their analysis by desorption electrospray ionization mass spectrometry.  

PubMed

The endophytic fungus Penicillium restrictum was isolated from the stems of a milk thistle (Silybum marianum) plant. In culture, the fungus produced distinct red guttates, which have been virtually uninvestigated, particularly from the standpoint of chemistry. Hence, this study examined the chemical mycology of P. restrictum and, in doing so, uncovered a series of both known and new polyhydroxyanthraquinones (1-9). These compounds were quorum sensing inhibitors in a clinical isolate of methicillin-resistant Staphylococcus aureus (MRSA), with IC50 values ranging from 8 to 120 ?M, suggesting antivirulence potential for the compounds. Moreover, the spatial and temporal distribution of the polyhydroxyanthraquinones was examined in situ via desorption electrospray ionization-mass spectrometry (DESI-MS) imaging, demonstrating the first application of this technique to a guttate-forming fungus and revealing both the concentration of secondary metabolites at the ventral surface of the fungus and their variance in colonies of differing ages. PMID:24911880

Figueroa, Mario; Jarmusch, Alan K; Raja, Huzefa A; El-Elimat, Tamam; Kavanaugh, Jeffrey S; Horswill, Alexander R; Cooks, R Graham; Cech, Nadja B; Oberlies, Nicholas H

2014-06-27

24

A Strategy for Antagonizing Quorum Sensing  

Microsoft Academic Search

Quorum-sensing bacteria communicate via small molecules called autoinducers to coordinate collective behaviors. Because quorum sensing controls virulence factor expression in many clinically relevant pathogens, membrane-permeable quorum sensing antagonists that prevent population-wide expression of virulence genes offer a potential route to novel antibacterial therapeutics. Here, we report a strategy for inhibiting quorum-sensing receptors of the widespread LuxR family. Structure-function studies with

Guozhou Chen

2011-01-01

25

Non-antibiotic quorum sensing inhibitors acting against N-acyl homoserine lactone synthase as druggable target  

PubMed Central

N-acylhomoserine lactone (AHL)-based quorum sensing (QS) is important for the regulation of proteobacterial virulence determinants. Thus, the inhibition of AHL synthases offers non-antibiotics-based therapeutic potentials against QS-mediated bacterial infections. In this work, functional AHL synthases of Pseudomonas aeruginosa LasI and RhlI were heterologously expressed in an AHL-negative Escherichia coli followed by assessments on their AHLs production using AHL biosensors and high resolution liquid chromatography–mass spectrometry (LCMS). These AHL-producing E. coli served as tools for screening AHL synthase inhibitors. Based on a campaign of screening synthetic molecules and natural products using our approach, three strongest inhibitors namely are salicylic acid, tannic acid and trans-cinnamaldehyde have been identified. LCMS analysis further confirmed tannic acid and trans-cinnemaldehyde efficiently inhibited AHL production by RhlI. We further demonstrated the application of trans-cinnemaldehyde inhibiting Rhl QS system regulated pyocyanin production in P. aeruginosa up to 42.06%. Molecular docking analysis suggested that trans-cinnemaldehyde binds to the LasI and EsaI with known structures mainly interacting with their substrate binding sites. Our data suggested a new class of QS-inhibiting agents from natural products targeting AHL synthase and provided a potential approach for facilitating the discovery of anti-QS signal synthesis as basis of novel anti-infective approach. PMID:25430794

Chang, Chien-Yi; Krishnan, Thiba; Wang, Hao; Chen, Ye; Yin, Wai-Fong; Chong, Yee-Meng; Tan, Li Ying; Chong, Teik Min; Chan, Kok-Gan

2014-01-01

26

Synthesis and evaluation of thiazolidinedione and dioxazaborocane analogues as inhibitors of AI-2 quorum sensing in Vibrio harveyi.  

PubMed

Two focused libraries based on two types of compounds, that is, thiazolidinediones and dioxazaborocanes were designed. Structural resemblances can be found between thiazolidinediones and well-known furanone type quorum sensing (QS) inhibitors such as N-acylaminofuranones, and/or acyl-homoserine lactone signaling molecules, while dioxazaborocanes structurally resemble previously reported oxazaborolidine derivatives which antagonized autoinducer 2 (AI-2) binding to its receptor. Because of this, we hypothesized that these compounds could affect AI-2 QS in Vibrio harveyi. Although all compounds blocked QS, the thiazolidinediones were the most active AI-2 QS inhibitors, with EC(50) values in the low micromolar range. Their mechanism of inhibition was elucidated by measuring the effect on bioluminescence in a series of V. harveyi QS mutants and by DNA-binding assays with purified LuxR protein. The active compounds neither affected bioluminescence as such nor the production of AI-2. Instead, our results indicate that the thiazolidinediones blocked AI-2 QS in V. harveyi by decreasing the DNA-binding ability of LuxR. In addition, several dioxazaborocanes were found to block AI-2 QS by targeting LuxPQ. PMID:23286963

Brackman, Gilles; Al Quntar, Abed Al Aziz; Enk, Claes D; Karalic, Izet; Nelis, Hans J; Van Calenbergh, Serge; Srebnik, Morris; Coenye, Tom

2013-02-01

27

Bacterial Quorum-Sensing Network Architectures  

PubMed Central

Quorum sensing is a cell-cell communication process in which bacteria use the production and detection of extracellular chemicals called autoinducers to monitor cell population density. Quorum sensing allows bacteria to synchronize the gene expression of the group, and thus, act in unison. Here, we review the mechanisms involved in quorum sensing with a focus on the Vibrio harveyi and Vibrio cholerae quorum-sensing systems. We discuss the differences between these two quorum-sensing systems and the differences between them and other paradigmatic bacterial signal transduction systems. We argue that the Vibrio quorum-sensing systems are optimally architected to precisely translate extracellular autoinducer information into internal changes in gene expression. We describe how studies of the V. harveyi and V. cholerae quorum-sensing systems have revealed some of the fundamental mechanisms underpinning the evolution of collective behaviors. PMID:19686078

Ng, Wai-Leung; Bassler, Bonnie L.

2015-01-01

28

Quorum Sensing Let Bacteria Talk  

Microsoft Academic Search

Quorum Sensing (QS), a wonderful natural method to regulate gene expressions in response to the fluctuation in the cell density of a given bacterial population and provides the key mechanism through which bacteria communicate. QS bacteria release chemical signal molecules called autoinducers that increase in concentration as a function of cell density. Lots of bacterial physiological activities including symbiosis, virulence,

Indrani Bhattacharyya; Mayukh Choudhury

2008-01-01

29

Honaucins A-C, potent inhibitors of inflammation and bacterial quorum sensing: synthetic derivatives and structure-activity relationships.  

PubMed

Honaucins A-C were isolated from the cyanobacterium Leptolyngbya crossbyana which was found overgrowing corals on the Hawaiian coast. Honaucin A consists of (S)-3-hydroxy-?-butyrolactone and 4-chlorocrotonic acid, which are connected via an ester linkage. Honaucin A and its two natural analogs exhibit potent inhibition of both bioluminescence, a quorum-sensing-dependent phenotype, in Vibrio harveyi BB120 and lipopolysaccharide-stimulated nitric oxide production in the murine macrophage cell line RAW264.7. The decrease in nitric oxide production was accompanied by a decrease in the transcripts of several proinflammatory cytokines, most dramatically interleukin-1?. Synthesis of honaucin A, as well as a number of analogs, and subsequent evaluation in anti-inflammation and quorum-sensing inhibition bioassays revealed the essential structural features for activity in this chemical class and provided analogs with greater potency in both assays. PMID:22633410

Choi, Hyukjae; Mascuch, Samantha J; Villa, Francisco A; Byrum, Tara; Teasdale, Margaret E; Smith, Jennifer E; Preskitt, Linda B; Rowley, David C; Gerwick, Lena; Gerwick, William H

2012-05-25

30

Honaucins A–C, Potent Inhibitors of Eukaryotic Inflammation and Bacterial Quorum Sensing: Synthetic Derivatives and Structure-Activity Relationships  

PubMed Central

SUMMARY Honaucins A–C were isolated from the cyanobacterium Leptolyngbya crossbyana which was found overgrowing corals on the Hawaiian coast. Honaucin A consists of (S)-3-hydroxy-?-butyrolactone and 4-chlorocrotonic acid which are connected via an ester linkage. Honaucin A and its two natural analogs exhibit potent inhibition of bioluminescence, a quorum sensing-dependent phenotype, in Vibrio harveyi BB120 as well as of lipopolysaccharide-stimulated nitric oxide production in the murine macrophage cell line RAW264.7. The decrease in nitric oxide production was accompanied by a decrease in the transcripts of several pro-inflammatory cytokines, most dramatically interleukin-1?. Synthesis of honaucin A as well as a number of analogs and subsequent evaluation in anti-inflammation and quorum sensing inhibition bioassays revealed the essential structural features for activity in this chemical class, and provided analogs with greater potency in both assays. PMID:22633410

Choi, Hyukjae; Mascuch, Samantha J.; Villa, Francisco A.; Byrum, Tara; Teasdale, Margaret E.; Smith, Jennifer E.; Preskitt, Linda B.; Rowley, David C.; Gerwick, Lena; Gerwick, William H.

2012-01-01

31

Vfr Controls Quorum Sensing in Pseudomonas aeruginosa  

Microsoft Academic Search

Pseudomonas aeruginosa controls several genes in a cell density-dependent manner through a phenomenon termed quorum sensing. The transcriptional activator protein of the las quorum-sensing system is encoded for by the lasR gene, which is at the top of a quorum-sensing hierarchy. The activation of LasR as a transcriptional activator induces the expression of multiple genes that code for factors important

ANNE M. ALBUS; EVERETT C. PESCI; LAURA J. RUNYEN-JANECKY; SUSAN E. H. WEST; BARBARA H. IGLEWSKI

1997-01-01

32

Optimal census by quorum sensing  

E-print Network

Quorum sensing is the regulation of gene expression in response to changes in cell density. To measure their cell density, bacterial populations produce and detect diffusible molecules called autoinducers. Individual bacteria internally represent the external concentration of autoinducers via the level of monitor proteins. In turn, these monitor proteins typically regulate both their own production and the production of autoinducers, thereby establishing internal and external feedbacks. Here, we ask whether feedbacks can increase the information available to cells about their local density. We quantify available information as the mutual information between the abundance of a monitor protein and the local cell density for biologically relevant models of quorum sensing. Using variational methods, we demonstrate that feedbacks can increase information transmission, allowing bacteria to resolve up to two additional ranges of cell density. Our analysis is relevant to multi-agent systems that track an external dri...

Taillefumier, Thibaud

2014-01-01

33

Quorum-sensing in Rhizobium  

Microsoft Academic Search

Quorum-sensing signals are found in many species of legume-nodulating rhizobia. In a well-characterized strain of R. leguminosarum biovar viciae, a variety of autoinducers are synthesised, and all have been identified as N-acyl-homoserine lactones. One of these N-acyl-homoserine lactones, is N-(3-hydroxy-7-cis-tetradecenoyl)-L- homoserine lactone, previously known as small bacteriocin, which inhibits the growth of several R. leguminosarum strains. The cinRI locus is

Florence Wisniewski-Dy; J. Allan Downie

2002-01-01

34

Quorum-sensing in Rhizobium  

Microsoft Academic Search

Quorum-sensing signals are found in many species of legume-nodulating rhizobia. In a well-characterized strain of R. leguminosarum biovar viciae, a variety of autoinducers are synthesised, and all have been identified as N-acyl-homoserine lactones. One of these N-acyl-homoserine lactones, is N-(3-hydroxy-7-cis-tetradecenoyl)-L-homoserine lactone, previously known as small bacteriocin, which inhibits the growth of several R. leguminosarum strains. The cinRI locus is responsible

Florence Wisniewski-Dyé; J. Allan Downie

2002-01-01

35

GENE EXPRESSION IN SALMONELLA ENTERICA SEROTYPE TYPHIMURIUM LUXS MUTANT IN RESPONSE TO QUORUM SENSING SIGNALS AND A POULTRY MEAT-DERIVED QUORUM SENSING INHIBITOR USING MICROARRAY-BASED STUDIES  

Technology Transfer Automated Retrieval System (TEKTRAN)

Quorum sensing describes the processes in which bacteria cells produce, secrete, and communicate using chemical signal molecules. There is evidence that these sensing signals, especially AI-2, can influence bacterial gene expression. We have previously shown that food matrices, such as poultry wash ...

36

Quorum sensing and swarming migration in bacteria  

Microsoft Academic Search

Bacterial cells can produce and sense signal molecules, allowing the whole population to initiate a concerted action once a critical concentration (corresponding to a particular population density) of the signal has been reached, a phenomenon known as quorum sensing. One of the possible quorum sensing-regulated phenotypes is swarming, a flagella-driven movement of differentiated swarmer cells (hyperflagellated, elongated, multinucleated) by which

Ruth Daniels; Jos Vanderleyden; Jan Michiels

2004-01-01

37

Combining in silico and biophysical methods for the development of Pseudomonas aeruginosa quorum sensing inhibitors: an alternative approach for structure-based drug design.  

PubMed

The present work deals with the optimization of an inhibitor of PqsD, an enzyme essential for Pseudomonas aeruginosa quorum sensing apparatus. Molecular docking studies, supported by biophysical methods (surface plasmon resonance, isothermal titration calorimetry, saturation transfer difference NMR), were used to illuminate the binding mode of the 5-aryl-ureidothiophene-2-carboxylic acids. Enabled to make profound predictions, structure-based optimization led to increased inhibitory potency. Finally a covalent inhibitor was obtained. Binding to the active site was confirmed by LC-ESI-MS and MALDI-TOF-MS experiments. Following this rational approach, potent PqsD inhibitors were efficiently developed within a short period of time. This example shows that a combination and careful application of in silico and biophysical methods represents a powerful complement to cocrystallography. PMID:24083807

Sahner, J Henning; Brengel, Christian; Storz, Michael P; Groh, Matthias; Plaza, Alberto; Müller, Rolf; Hartmann, Rolf W

2013-11-14

38

Quorum Sensing in Extreme Environments  

PubMed Central

Microbial communication, particularly that of quorum sensing, plays an important role in regulating gene expression in a range of organisms. Although this phenomenon has been well studied in relation to, for example, virulence gene regulation, the focus of this article is to review our understanding of the role of microbial communication in extreme environments. Cell signaling regulates many important microbial processes and may play a pivotal role in driving microbial functional diversity and ultimately ecosystem function in extreme environments. Several recent studies have characterized cell signaling in modern analogs to early Earth communities (microbial mats), and characterization of cell signaling systems in these communities may provide unique insights in understanding the microbial interactions involved in function and survival in extreme environments. Cell signaling is a fundamental process that may have co-evolved with communities and environmental conditions on the early Earth. Without cell signaling, evolutionary pressures may have even resulted in the extinction rather than evolution of certain microbial groups. One of the biggest challenges in extremophile biology is understanding how and why some microbial functional groups are located where logically they would not be expected to survive, and tightly regulated communication may be key. Finally, quorum sensing has been recently identified for the first time in archaea, and thus communication at multiple levels (potentially even inter-domain) may be fundamental in extreme environments. PMID:25371335

Montgomery, Kate; Charlesworth, James C.; LeBard, Rebecca; Visscher, Pieter T.; Burns, Brendan P.

2013-01-01

39

Quorum Sensing and its Relevance to Infectious Diseases  

Microsoft Academic Search

Quorum sensing allows bacteria to detect the density of their own species and alter their metabolism to take advantage of this density. Quorum sensing is used by a wide variety of bacteria including human pathogens. Quorum sensing genes are important for the pathogenic potential of Pseudomonas aeruginosa and Staphylococcus aureus, as well as other invasive bacteria. An understanding of quorum

H. Donabedian

2003-01-01

40

Global convergence of quorum-sensing networks  

E-print Network

In many natural synchronization phenomena, communication between individual elements occurs not directly but rather through the environment. One of these instances is bacterial quorum sensing, where bacteria release signaling ...

Slotine, Jean-Jacques E.

41

Localized Quorum Sensing in Vibrio fischeri  

Microsoft Academic Search

Quorum sensing is almost always regarded as a population density effect in three-dimensional bulk samples of bacteria. Here we create two-dimensional samples of Vibrio fischeri cells adhered onto glass surfaces to examine the effect of local population densities on quorum sensing. This is done by measuring the luminescent response. The 2-D bacterial populations enable us to simultaneously account for time

Mary E. Parent; Charles E. Snyder; Nathaniel D. Kopp; Darrell Velegol

2008-01-01

42

Modeling a synthetic multicellular clock: Repressilators coupled by quorum sensing  

E-print Network

Modeling a synthetic multicellular clock: Repressilators coupled by quorum sensing Jordi Garcia of such genetic oscillators interacting through a quorum-sensing mechanism should self-synchronize in a robust way

Elowitz, Michael

43

Dynamical Quorum Sensing and Synchronization in Large Populations  

E-print Network

Dynamical Quorum Sensing and Synchronization in Large Populations of Chemical Oscillators Annette F oscillate in nearly complete synchrony (12). This type of transition is much like quorum-sensing transitions solution (15). Many examples of quorum- sensing transitions have been found, such as the appearance

Showalter, Kenneth

44

Quorum Sensing-enabled Amplification for Molecular Nanonetworks  

E-print Network

Quorum Sensing-enabled Amplification for Molecular Nanonetworks Sergi Abadal, Ignacio Llatser. In this paper, we propose the employment of Quorum Sensing so as to achieve cooperative amplification of a given signal. By means of Quorum Sensing, we aim to synchronize the course of action of a certain number

Politècnica de Catalunya, Universitat

45

Attenuation of bacterial virulence by quorum sensing-regulated lysis  

Microsoft Academic Search

Genetically attenuated pathogenic bacteria have been extensively considered as vaccine candidates. However, insufficient attenuation has been a frequent limitation of this approach. Many pathogens use quorum sensing to escape host defense mechanism. Here, we hypothesized that quorum sensing can be manipulated to diminish pathogenesis. To test this hypothesis, we modified the quorum sensing circuitry of a live cholera vaccine strain

Anisia J. Silva; Jorge A. Benitez; Jian-He Wu

2010-01-01

46

Kin selection, quorum sensing and virulence in pathogenic bacteria  

E-print Network

Kin selection, quorum sensing and virulence in pathogenic bacteria Kendra P. Rumbaugh1, Urvish termed quorum sensing (QS) [1,2]. Cells release small diffusible signal molecules, which have two effects and virulence often depends upon the cooperative release of extracellular factors excreted in response to quorum

Dever, Jennifer A.

47

Migration of Dictyostelium Amoeba: Role of Adhesion and Quorum Sensing  

E-print Network

Migration of Dictyostelium Amoeba: Role of Adhesion and Quorum Sensing Laurent Gol´e LPMCN and cell and factors of Quorum sensing on the migration of Dictyostelium amoeba. Tools to automate´etection de Quorum sur la migration amibienne de Dictyostelium . Des outils pour automatiser les enreg

Paris-Sud XI, Université de

48

AI-2 Quorum Sensing in Campylobacter jejuni  

Technology Transfer Automated Retrieval System (TEKTRAN)

Quorum sensing response modulates many physiological attributes, such as bacterial virulence/pathogenesis, competence, and biofilm formation, when the bacterial population has reached a certain threshold. Among the various signaling compounds, autoinducer-2 (AI-2) is produced by most bacterial spec...

49

A Strategy for Antagonizing Quorum Sensing  

SciTech Connect

Quorum-sensing bacteria communicate via small molecules called autoinducers to coordinate collective behaviors. Because quorum sensing controls virulence factor expression in many clinically relevant pathogens, membrane-permeable quorum sensing antagonists that prevent population-wide expression of virulence genes offer a potential route to novel antibacterial therapeutics. Here, we report a strategy for inhibiting quorum-sensing receptors of the widespread LuxR family. Structure-function studies with natural and synthetic ligands demonstrate that the dimeric LuxR-type transcription factor CviR from Chromobacterium violaceum is potently antagonized by molecules that bind in place of the native acylated homoserine lactone autoinducer, provided that they stabilize a closed conformation. In such conformations, each of the two DNA-binding domains interacts with the ligand-binding domain of the opposing monomer. Consequently, the DNA-binding helices are held apart by {approx}60 {angstrom}, twice the {approx}30 {angstrom} separation required for operator binding. This approach may represent a general strategy for the inhibition of multidomain proteins.

G Chen; L Swem; D Swem; D Stauff; C OLoughlin; P Jeffrey; B Bassler; F Hughson

2011-12-31

50

Collective sensing and collective responses in quorum-sensing bacteria  

PubMed Central

Bacteria often face fluctuating environments, and in response many species have evolved complex decision-making mechanisms to match their behaviour to the prevailing conditions. Some environmental cues provide direct and reliable information (such as nutrient concentrations) and can be responded to individually. Other environmental parameters are harder to infer and require a collective mechanism of sensing. In addition, some environmental challenges are best faced by a group of cells rather than an individual. In this review, we discuss how bacteria sense and overcome environmental challenges as a group using collective mechanisms of sensing, known as ‘quorum sensing’ (QS). QS is characterized by the release and detection of small molecules, potentially allowing individuals to infer environmental parameters such as density and mass transfer. While a great deal of the molecular mechanisms of QS have been described, there is still controversy over its functional role. We discuss what QS senses and how, what it controls and why, and how social dilemmas shape its evolution. Finally, there is a growing focus on the use of QS inhibitors as antibacterial chemotherapy. We discuss the claim that such a strategy could overcome the evolution of resistance. By linking existing theoretical approaches to data, we hope this review will spur greater collaboration between experimental and theoretical researchers. PMID:25505130

Popat, R.; Cornforth, D. M.; McNally, L.; Brown, S. P.

2015-01-01

51

Collective sensing and collective responses in quorum-sensing bacteria.  

PubMed

Bacteria often face fluctuating environments, and in response many species have evolved complex decision-making mechanisms to match their behaviour to the prevailing conditions. Some environmental cues provide direct and reliable information (such as nutrient concentrations) and can be responded to individually. Other environmental parameters are harder to infer and require a collective mechanism of sensing. In addition, some environmental challenges are best faced by a group of cells rather than an individual. In this review, we discuss how bacteria sense and overcome environmental challenges as a group using collective mechanisms of sensing, known as 'quorum sensing' (QS). QS is characterized by the release and detection of small molecules, potentially allowing individuals to infer environmental parameters such as density and mass transfer. While a great deal of the molecular mechanisms of QS have been described, there is still controversy over its functional role. We discuss what QS senses and how, what it controls and why, and how social dilemmas shape its evolution. Finally, there is a growing focus on the use of QS inhibitors as antibacterial chemotherapy. We discuss the claim that such a strategy could overcome the evolution of resistance. By linking existing theoretical approaches to data, we hope this review will spur greater collaboration between experimental and theoretical researchers. PMID:25505130

Popat, R; Cornforth, D M; McNally, L; Brown, S P

2015-02-01

52

Cross-Species Induction of Antimicrobial Compounds, Biosurfactants and Quorum-Sensing Inhibitors in Tropical Marine Epibiotic Bacteria by Pathogens and Biofouling Microorganisms  

Microsoft Academic Search

Enhancement or induction of antimicrobial, biosurfactant, and quorum-sensing inhibition property in marine bacteria due to\\u000a cross-species and cross-genera interactions was investigated. Four marine epibiotic bacteria (Bacillus sp. S3, B. pumilus S8, B. licheniformis D1, and Serratia marcescens V1) displaying antimicrobial activity against pathogenic or biofouling fungi (Candida albicans CA and Yarrowia lipolytica YL), and bacteria (Pseudomonas aeruginosa PA and Bacillus

Devendra H. Dusane; Pratiek Matkar; Valayam P. Venugopalan; Ameeta Ravi Kumar; Smita S. Zinjarde

2011-01-01

53

ORIGINAL ARTICLE Interference with the quorum sensing systems in a Vibrio  

E-print Network

ORIGINAL ARTICLE Interference with the quorum sensing systems in a Vibrio harveyi strain alters is influenced Keywords Brachionus, brominated furanone, quorum sensing, Vibrio harveyi. Correspondence Nguyen whether quorum sensing is involved in the observed phenomena. Methods and Results: Gnotobiotic B

Wood, Thomas K.

54

The Evolutionary Ecology of the PlcR-PapR Quorum Sensing System in Bacillus thuringiensis  

E-print Network

1 The Evolutionary Ecology of the PlcR-PapR Quorum Sensing System in Bacillus thuringiensis Liqin called quorum sensing (QS), whereby bacteria monitor population density through the secretion of small......................................................... 13 1.3 Quorum sensing in microorganisms

Chittka, Lars

55

Is quorum sensing a side effect of diffusion sensing?  

Microsoft Academic Search

Many bacteria appear to communicate by releasing and sensing autoinducer molecules, which are believed to function primarily as sensors of population density. However, this quorum-sensing hypothesis rests on very weak foundations, as neither the need for group action nor the selective conditions required for its evolution have been demonstrated. Here, I argue for a more direct function of autoinducer secretion

Rosemary J. Redfield

2002-01-01

56

Highly Potent, Chemically Stable Quorum Sensing Agonists for Vibrio Cholerae.  

PubMed

In the Vibrio cholerae pathogen, initiation of bacterial quorum sensing pathways serves to suppress virulence. We describe herein a potent and chemically stable small molecule agonist of V. cholerae quorum sensing, which was identified through rational drug design based on the native quorum sensing signal. This novel agonist may serve as a useful lead compound for the control of virulence in V. cholerae. PMID:24436778

Perez, Lark J; Karagounis, Theodora K; Hurley, Amanda; Bassler, Bonnie L; Semmelhack, Martin F

2014-01-01

57

P. aeruginosa quorum-sensing systems and virulence  

Microsoft Academic Search

Quorum sensing is an important mechanism for the regulation of genes in many Gram-negative and Gram-positive bacteria. In the opportunistic pathogen Pseudomonas aeruginosa, the absence of one or more components of the quorum-sensing system results in a significant reduction in virulence. Recent advances in the past year have demonstrated that the quorum-sensing signal molecule 3O-C12-HSL is also a potent stimulator

Roger S Smith; Barbara H Iglewski

2003-01-01

58

Azithromycin Inhibits Quorum Sensing in Pseudomonas aeruginosa  

Microsoft Academic Search

We report that 2 mg of azithromycin\\/ml inhibits the quorum-sensing circuitry of Pseudomonas aeruginosa strain PAO1. Addition of synthetic autoinducers partially restored the expression of the trancriptional acti- vator-encoding genes lasR and rhlR but not that of the autoinducer synthase-encoding gene lasI. We propose that azithromycin interferes with the synthesis of autoinducers, by an unknown mechanism, leading to a reduction

KAZUHIRO TATEDA; RACHEL COMTE; JEAN-CLAUDE PECHERE; THILO KOHLER; KEIZO YAMAGUCHI; CHRISTIAN VAN DELDEN

2001-01-01

59

Quorum sensing in plant-associated bacteria  

Microsoft Academic Search

N-acyl homoserine lactone (AHL)-mediated quorum sensing by bacteria regulates traits that are involved in symbiotic, pathogenic and surface-associated relationships between microbial populations and their plant hosts. Recent advances demonstrate deviations from the classic LuxR\\/LuxI paradigm, which was first developed in Vibrio. For example, LuxR homologs can repress as well as activate gene expression, and non-AHL signals and signal mimics can

John Loh; Elizabeth A Pierson; Leland S Pierson; Gary Stacey; Arun Chatterjee

2002-01-01

60

Cooperation and conflict in quorum-sensing bacterial populations  

E-print Network

LETTERS Cooperation and conflict in quorum-sensing bacterial populations Stephen P. Diggle1 communicate by releasing and sensing small diffusible signal molecules in a process com- monly known as quorum sensing (QS)1­4 . It is generally assumed that QS is used to coordinate cooperative behaviours at the popu

West, Stuart

61

Exploiting Quorum Sensing To Confuse Bacterial Pathogens  

PubMed Central

SUMMARY Cell-cell communication, or quorum sensing, is a widespread phenomenon in bacteria that is used to coordinate gene expression among local populations. Its use by bacterial pathogens to regulate genes that promote invasion, defense, and spread has been particularly well documented. With the ongoing emergence of antibiotic-resistant pathogens, there is a current need for development of alternative therapeutic strategies. An antivirulence approach by which quorum sensing is impeded has caught on as a viable means to manipulate bacterial processes, especially pathogenic traits that are harmful to human and animal health and agricultural productivity. The identification and development of chemical compounds and enzymes that facilitate quorum-sensing inhibition (QSI) by targeting signaling molecules, signal biogenesis, or signal detection are reviewed here. Overall, the evidence suggests that QSI therapy may be efficacious against some, but not necessarily all, bacterial pathogens, and several failures and ongoing concerns that may steer future studies in productive directions are discussed. Nevertheless, various QSI successes have rightfully perpetuated excitement surrounding new potential therapies, and this review highlights promising QSI leads in disrupting pathogenesis in both plants and animals. PMID:23471618

LaSarre, Breah

2013-01-01

62

The impact of quorum sensing on the virulence of Aeromonas hydrophila and Aeromonas salmonicida towards burbot (Lota lota L.) larvae.  

PubMed

In this study, the link between quorum sensing in Aeromonas spp. and its virulence towards burbot (Lota lota) was investigated. High mortality occurred in burbot juveniles challenged with Aeromonas salmonicida HN-00, but not in juveniles challenged with Aeromonas hydrophila AH-1N. Meanwhile, both A. hydrophila AH-1N and A. salmonicida HN-00 were virulent towards larvae. The effect of quorum sensing on the virulence of A. hydrophila AH-1N towards burbot larvae was further investigated using quorum sensing mutants (N-(butyryl)-L-homoserine lactone production and receptor mutants). Challenge with these mutants resulted in higher survival of burbot larvae when compared to challenge with the wild type, and the addition of the signal molecule N-butyryl-L-homoserine lactone restored the virulence of the quorum sensing production mutant. Moreover, quorum sensing inhibitors protected the burbot larvae from both Aeromonas strains. Finally, the freshwater micro-algae Chlorella saccharophila and Chlamydomonas reinhardtii, which are able to interfere with quorum sensing, also protected burbot from the pathogens. However, QS interference was unlikely to be the only mechanism. This study revealed that the virulence of Aeromonas spp. towards burbot is regulated by quorum sensing and that quorum sensing inhibitors and micro-algae are promising biocontrol agents. PMID:22465799

Natrah, F M I; Alam, Md Iftakharul; Pawar, Sushant; Harzevili, A Shiri; Nevejan, Nancy; Boon, Nico; Sorgeloos, Patrick; Bossier, Peter; Defoirdt, Tom

2012-09-14

63

Global convergence of quorum-sensing networks  

NASA Astrophysics Data System (ADS)

In many natural synchronization phenomena, communication between individual elements occurs not directly but rather through the environment. One of these instances is bacterial quorum sensing, where bacteria release signaling molecules in the environment which in turn are sensed and used for population coordination. Extending this motivation to a general nonlinear dynamical system context, this paper analyzes synchronization phenomena in networks where communication and coupling between nodes are mediated by shared dynamical quantities, typically provided by the nodes’ environment. Our model includes the case when the dynamics of the shared variables themselves cannot be neglected or indeed play a central part. Applications to examples from system biology illustrate the approach.

Russo, Giovanni; Slotine, Jean Jacques E.

2010-10-01

64

Global convergence of quorum-sensing networks  

E-print Network

In many natural synchronization phenomena, communication between individual elements occurs not directly, but rather through the environment. One of these instances is bacterial quorum sensing, where bacteria release signaling molecules in the environment which in turn are sensed and used for population coordination. Extending this motivation to a general non- linear dynamical system context, this paper analyzes synchronization phenomena in networks where communication and coupling between nodes are mediated by shared dynamical quan- tities, typically provided by the nodes' environment. Our model includes the case when the dynamics of the shared variables themselves cannot be neglected or indeed play a central part. Applications to examples from systems biology illustrate the approach.

Russo, Giovanni

2010-01-01

65

Quorum sensing controls biofilm formation in Vibrio cholerae  

Microsoft Academic Search

Summary Multiple quorum-sensing circuits function in parallel to control virulence and biofilm formation in Vibrio cholerae . In contrast to other bacterial pathogens that induce virulence factor production and\\/or biofilm for- mation at high cell density in the presence of quorum- sensing autoinducers, V. cholerae represses these behaviours at high cell density. Consistent with this, we show here that V.

Brian K. Hammer; Bonnie L. Bassler

2003-01-01

66

Analysis of quorum sensing in Yersinia pestis CO92  

Microsoft Academic Search

The etiologic agent of bubonic plague, Yersinia pestis, produces cell density-dependent chemical signals in a process named quorum sensing (QS). Though the closely related enteric pathogen Yersinia pseudotuberculosis uses a QS system to regulate motility, the role of quorum sensing in Y. pestis is unclear. Yersinia pestis possess two conserved QS systems, an AI-1 system that utilizes acyl homoserine lactones

Jing Yu

2011-01-01

67

Quorum-sensing and cheating in bacterial biofilms  

E-print Network

Quorum-sensing and cheating in bacterial biofilms Roman Popat1,, Shanika A. Crusz1, Marco Messina1, Pseudomonas aeruginosa, by examining the influence of putative cheats that do not cooperate via cell-to-cell signalling (quorum-sensing, QS). We found that: (i) QS cheating occurs in biofilm populations owing

West, Stuart

68

Transition state analogs of 5'-methylthioadenosine nucleosidase disrupt quorum sensing.  

SciTech Connect

5'-Methylthioadenosine/S-adenosylhomocysteine nucleosidase (MTAN) is a bacterial enzyme involved in S-adenosylmethionine-related quorum sensing pathways that induce bacterial pathogenesis factors. Transition state analogs MT-DADMe-Immucillin-A, EtT-DADMe-Immucillin-A and BuT-DADMe-Immucillin-A are slow-onset, tight-binding inhibitors of Vibrio cholerae MTAN (VcMTAN), with equilibrium dissociation constants of 73, 70 and 208 pM, respectively. Structural analysis of VcMTAN with BuT-DADMe-Immucillin-A revealed interactions contributing to the high affinity. We found that in V. cholerae cells, these compounds are potent MTAN inhibitors with IC50 values of 27, 31 and 6 nM for MT-, EtT- and BuT-DADMe-Immucillin-A, respectively; the compounds disrupt autoinducer production in a dose-dependent manner without affecting growth. MT- and BuT-DADMe-Immucillin-A also inhibited autoinducer-2 production in enterohemorrhagic Escherichia coli O157:H7 with IC{sub 50} values of 600 and 125 nM, respectively. BuT-DADMe-Immucillin-A inhibition of autoinducer-2 production in both strains persisted for several generations and caused reduction in biofilm formation. These results support MTAN's role in quorum sensing and its potential as a target for bacterial anti-infective drug design.

Gutierrez, J.; Crowder, T; Rinaldo-Matthis, A; Ho, M; Almo, S; Schramm, V

2009-01-01

69

Engineered biological nanofactories trigger quorum sensing response in targeted bacteria  

NASA Astrophysics Data System (ADS)

Biological nanofactories, which are engineered to contain modules that can target, sense and synthesize molecules, can trigger communication between different bacterial populations. These communications influence biofilm formation, virulence, bioluminescence and many other bacterial functions in a process called quorum sensing. Here, we show the assembly of a nanofactory that can trigger a bacterial quorum sensing response in the absence of native quorum molecules. The nanofactory comprises an antibody (for targeting) and a fusion protein that produces quorum molecules when bound to the targeted bacterium. Our nanofactory selectively targets the appropriate bacteria and triggers a quorum sensing response when added to two populations of bacteria. The nanofactories also trigger communication between two bacterial populations that are otherwise non-communicating. We envision the use of these nanofactories in generating new antimicrobial treatments that target the communication networks of bacteria rather than their viability.

Fernandes, Rohan; Roy, Varnika; Wu, Hsuan-Chen; Bentley, William E.

2010-03-01

70

Quorum Quenching Enzymes and Their Application in Degrading Signal Molecules to Block Quorum Sensing-Dependent Infection  

PubMed Central

With the emergence of antibiotic-resistant strains of bacteria, the available options for treating bacterial infections have become very limited, and the search for a novel general antibacterial therapy has received much greater attention. Quorum quenching can be used to control disease in a quorum sensing system by triggering the pathogenic phenotype. The interference with the quorum sensing system by the quorum quenching enzyme is a potential strategy for replacing traditional antibiotics because the quorum quenching strategy does not aim to kill the pathogen or limit cell growth but to shut down the expression of the pathogenic gene. Quorum quenching enzymes have been identified in quorum sensing and non-quorum sensing microbes, including lactonase, acylase, oxidoreductase and paraoxonase. Lactonase is widely conserved in a range of bacterial species and has variable substrate spectra. The existence of quorum quenching enzymes in the quorum sensing microbes can attenuate their quorum sensing, leading to blocking unnecessary gene expression and pathogenic phenotypes. In this review, we discuss the physiological function of quorum quenching enzymes in bacterial infection and elucidate the enzymatic protection in quorum sensing systems for host diseases and their application in resistance against microbial diseases. PMID:24065091

Chen, Fang; Gao, Yuxin; Chen, Xiaoyi; Yu, Zhimin; Li, Xianzhen

2013-01-01

71

Quorum sensing and policing of Pseudomonas aeruginosa social cheaters.  

PubMed

The bacterium Pseudomonas aeruginosa is an opportunistic human pathogen that uses a quorum sensing signal cascade to activate expression of dozens of genes when sufficient population densities have been reached. Quorum sensing controls production of several key virulence factors, including secreted proteases such as elastase. Cooperating groups of bacteria growing on protein are susceptible to social cheating by quorum-sensing defective mutants. A possible way to restrict cheater emergence is by policing where cooperators produce costly goods to sanction or punish cheats. The P. aeruginosa LasR-LasI quorum sensing system controls genes including those encoding proteases and also those encoding a second quorum-sensing system, the RhlR-RhlI system, which controls numerous genes including those for cyanide production. By using RhlR quorum sensing mutants and cyanide synthesis mutants, we show that cyanide production is costly and cyanide-producing cooperators use cyanide to punish LasR-null social cheaters. Cooperators are less susceptible to cyanide than are LasR mutants. These experiments demonstrate policing in P. aeruginosa, provide a mechanistic understanding of policing, and show policing involves the cascade organization of the two quorum sensing systems in this bacterium. PMID:25646454

Wang, Meizhen; Schaefer, Amy L; Dandekar, Ajai A; Greenberg, E Peter

2015-02-17

72

Quorum sensing and Bacterial Pathogenicity: From Molecules to Disease  

PubMed Central

Quorum sensing in prokaryotic biology refers to the ability of a bacterium to sense information from other cells in the population when they reach a critical concentration (i.e. a Quorum) and communicate with them. The “language” used for this intercellular communication is based on small, self-generated signal molecules called as autoinducers. Quorum sensing is thought to afford pathogenic bacteriaa mechanism to minimize host immune responses by delaying theproduction of tissue-damaging virulence factors until sufficientbacteria have amassed and are prepared to overwhelm host defensemechanisms and establish infection. Quorum sensing systems are studied in a large number of gram-negative bacterial species belonging to ?, ?, and ? subclasses of proteobacteria. Among the pathogenic bacteria, Pseudomonas aeruginosa is perhaps the best understood in terms of the virulence factors regulated and the role the Quorum sensing plays in pathogenicity. Presently, Quorum sensing is considered as a potential novel target for antimicrobial therapy to control multi/all drug-resistant infections. This paper reviews Quorum sensing in gram positive and gram negative bacteria and its role in biofilm formation. PMID:21701655

Deep, Antariksh; Chaudhary, Uma; Gupta, Varsha

2011-01-01

73

Global convergence of quorum-sensing networks Giovanni Russo1,  

E-print Network

of quorum sensing-like mechanisms lies in the fact that communication between nodes (e.g. bacteria) occurs, communication between individual elements occurs not directly, but rather through the environment. One of these instances is bacterial quorum sens- ing, where bacteria release signaling molecules in the environment which

Slotine, Jean-Jacques E.

74

A spatial model of the evolution of quorum sensing regulating bacteriocin production  

E-print Network

A spatial model of the evolution of quorum sensing regulating bacteriocin production Tama´s Cza of cooperative behavior, quorum sensing (QS) in bacteria is potentially vulnerable to cheating, the occurrence, evolutionary stability, quorum sensing. [Behav Ecol 18:866­873 (2007)] Many species of bacteria exhibit quorum

Czárán, Tamás

75

Interspecific Quorum Sensing Mediates the Resuscitation of Viable but Nonculturable Vibrios  

PubMed Central

Entry and exit from dormancy are essential survival mechanisms utilized by microorganisms to cope with harsh environments. Many bacteria, including the opportunistic human pathogen Vibrio vulnificus, enter a form of dormancy known as the viable but nonculturable (VBNC) state. VBNC cells can resuscitate when suitable conditions arise, yet the molecular mechanisms facilitating resuscitation in most bacteria are not well understood. We discovered that bacterial cell-free supernatants (CFS) can awaken preexisting dormant vibrio populations within oysters and seawater, while CFS from a quorum sensing mutant was unable to produce the same resuscitative effect. Furthermore, the quorum sensing autoinducer AI-2 could induce resuscitation of VBNC V. vulnificus in vitro, and VBNC cells of a mutant unable to produce AI-2 were unable to resuscitate unless the cultures were supplemented with exogenous AI-2. The quorum sensing inhibitor cinnamaldehyde delayed the resuscitation of wild-type VBNC cells, confirming the importance of quorum sensing in resuscitation. By monitoring AI-2 production by VBNC cultures over time, we found quorum sensing signaling to be critical for the natural resuscitation process. This study provides new insights into the molecular mechanisms stimulating VBNC cell exit from dormancy, which has significant implications for microbial ecology and public health. PMID:24509922

Ayrapetyan, Mesrop; Williams, Tiffany C.

2014-01-01

76

Quorum sensing regulates the osmotic stress response in Vibrio harveyi.  

PubMed

Bacteria use a chemical communication process called quorum sensing to monitor cell density and to alter behavior in response to fluctuations in population numbers. Previous studies with Vibrio harveyi have shown that LuxR, the master quorum-sensing regulator, activates and represses >600 genes. These include six genes that encode homologs of the Escherichia coli Bet and ProU systems for synthesis and transport, respectively, of glycine betaine, an osmoprotectant used during osmotic stress. Here we show that LuxR activates expression of the glycine betaine operon betIBA-proXWV, which enhances growth recovery under osmotic stress conditions. BetI, an autorepressor of the V. harveyi betIBA-proXWV operon, activates the expression of genes encoding regulatory small RNAs that control quorum-sensing transitions. Connecting quorum-sensing and glycine betaine pathways presumably enables V. harveyi to tune its execution of collective behaviors to its tolerance to stress. PMID:25313392

van Kessel, Julia C; Rutherford, Steven T; Cong, Jian-Ping; Quinodoz, Sofia; Healy, James; Bassler, Bonnie L

2015-01-01

77

Role of Quorum Sensing in Sinorhizobium meliloti-Alfalfa Symbiosis  

Microsoft Academic Search

The ExpR\\/Sin quorum-sensing system of the gram-negative soil bacterium Sinorhizobium meliloti plays an important role in the establishment of symbiosis with its host plant Medicago sativa. A mutant unable to produce autoinducer signal molecules (sinI) is deficient in its ability to invade the host, but paradoxically, a strain lacking the quorum-sensing transcriptional regulator ExpR is as efficient as the wild

Nataliya Gurich; Juan E. Gonzalez

2009-01-01

78

Modeling of signal transduction in bacterial quorum-sensing  

Microsoft Academic Search

Several species of bacteria are able to coordinate gene regulation in response to population density, a process known as ``quorum-sensing''. Quorum-sensing bacteria produce, secrete, and detect signal molecules called autoinducers. For several species of bacteria in the Vibrio genus, recent results have shown that the external autoinducer concentrations control the expression of regulatory small RNA(s) which are critical to the

Andrew Fenley; Suman Banik; Rahul Kulkarni

2006-01-01

79

Early development and quorum sensing in bacterial biofilms  

Microsoft Academic Search

.  ?We develop mathematical models to examine the formation, growth and quorum sensing activity of bacterial biofilms. The growth\\u000a aspects of the model are based on the assumption of a continuum of bacterial cells whose growth generates movement, within\\u000a the developing biofilm, described by a velocity field. A model proposed in Ward et al. (2001) to describe quorum sensing, a process

John P. Ward; John R. King; Adrian J. Koerber; Julie M. Croft; R. Elizabeth Sockett; Paul Williams

2003-01-01

80

Detection of quorum-sensing-related molecules in Vibrio scophthalmi  

Microsoft Academic Search

BACKGROUND: Cell-to-cell communication (also referred to as quorum sensing) based on N-acyl-homoserine lactones (AHLs) is a widespread response to environmental change in Gram-negative bacteria. AHLs seem to be highly variable, both in terms of the acyl chain length and in the chemical structure of the radicals. Another quorum sensing pathway, the autoinducer-2-based system, is present both in Gram-positive and Gram-negative

Cristina García-Aljaro; Leo Eberl; Kathrin Riedel; Anicet R Blanch

2008-01-01

81

Quorum Sensing, or How Bacteria “Talk” to Each Other  

Microsoft Academic Search

Reviewed are recent advances in studying the quorum-sensing systems, which regulate gene expression depending on population density. Low-molecular-weight acyl derivatives of L-homoserine lactone (N-AHL) freely diffuse through cell membranes and determine cell-to-cell communication in bacteria. The quorum-sensing systems have first been found to regulate bioluminescence in marine bacteria Photobacterium(Vibrio) fischeriand Vibrio harveyi. Such systems are widespread and control expression of

G. B. Zavilgelsky; I. V. Manukhov

2001-01-01

82

Choosing an Appropriate Infection Model to Study Quorum Sensing Inhibition in Pseudomonas Infections  

PubMed Central

Bacteria, although considered for decades to be antisocial organisms whose sole purpose is to find nutrients and multiply are, in fact, highly communicative organisms. Referred to as quorum sensing, cell-to-cell communication mechanisms have been adopted by bacteria in order to co-ordinate their gene expression. By behaving as a community rather than as individuals, bacteria can simultaneously switch on their virulence factor production and establish successful infections in eukaryotes. Understanding pathogen-host interactions requires the use of infection models. As the use of rodents is limited, for ethical considerations and the high costs associated with their use, alternative models based on invertebrates have been developed. Invertebrate models have the benefits of low handling costs, limited space requirements and rapid generation of results. This review presents examples of such models available for studying the pathogenicity of the Gram-negative bacterium Pseudomonas aeruginosa. Quorum sensing interference, known as quorum quenching, suggests a promising disease-control strategy since quorum-quenching mechanisms appear to play important roles in microbe-microbe and host-pathogen interactions. Examples of natural and synthetic quorum sensing inhibitors and their potential as antimicrobials in Pseudomonas-related infections are discussed in the second part of this review. PMID:24065108

Papaioannou, Evelina; Utari, Putri Dwi; Quax, Wim J.

2013-01-01

83

Emergence of Collective Behavior in Groups of Excitable Catalyst-Loaded Particles: Spatiotemporal Dynamical Quorum Sensing  

E-print Network

Dynamical Quorum Sensing Mark R. Tinsley,1 Annette F. Taylor,2 Zhaoyang Huang,1 and Kenneth Showalter1 1, known as quorum sensing, cells communicate via the exchange of chemical signaling species through

Showalter, Kenneth

84

Computational modeling of the quorum-sensing network in bacteria  

NASA Astrophysics Data System (ADS)

Certain species of bacteria are able produce and sense the concentration of small molecules called autodinducers in order to coordinate gene regulation in response to population density, a process known as ``quorum-sensing''. The resulting regulation of gene expression involves both transcriptional and post-transcriptional regulators. In particular, the species of bacteria in the Vibrio genus use small RNAs to regulate the master protein controlling the quorum-sensing response (luminescence, biofilm formation, virulence...). We model the network of interactions using a modular approach which provides a quantitative understanding of how signal transduction occurs. The parameters of the input-module are fit to current experimental results allowing for testable predictions to be made for future experiments. The results of our analysis offer a revised perspective on quorum-sensing based regulation.

Fenley, Andrew; Banik, Suman; Kulkarni, Rahul

2007-03-01

85

Quorum sensing in group A Streptococcus  

PubMed Central

Quorum sensing (QS) is a widespread phenomenon in the microbial world that has important implications in the coordination of population-wide responses in several bacterial pathogens. In Group A Streptococcus (GAS), many questions surrounding QS systems remain to be solved pertaining to their function and their contribution to the GAS lifestyle in the host. The QS systems of GAS described to date can be categorized into four groups: regulator gene of glucosyltransferase (Rgg), Sil, lantibiotic systems, and LuxS/AI-2. The Rgg family of proteins, a conserved group of transcription factors that modify their activity in response to signaling peptides, has been shown to regulate genes involved in virulence, biofilm formation and competence. The sil locus, whose expression is regulated by the activity of signaling peptides and a putative two-component system (TCS), has been implicated on regulating genes involved with invasive disease in GAS isolates. Lantibiotic regulatory systems are involved in the production of bacteriocins and their autoregulation, and some of these genes have been shown to target both bacterial organisms as well as processes of survival inside the infected host. Finally AI-2 (dihydroxy pentanedione, DPD), synthesized by the LuxS enzyme in several bacteria including GAS, has been proposed to be a universal bacterial communication molecule. In this review we discuss the mechanisms of these four systems, the putative functions of their targets, and pose critical questions for future studies. PMID:25309879

Jimenez, Juan Cristobal; Federle, Michael J.

2014-01-01

86

Quorum sensing in group A Streptococcus.  

PubMed

Quorum sensing (QS) is a widespread phenomenon in the microbial world that has important implications in the coordination of population-wide responses in several bacterial pathogens. In Group A Streptococcus (GAS), many questions surrounding QS systems remain to be solved pertaining to their function and their contribution to the GAS lifestyle in the host. The QS systems of GAS described to date can be categorized into four groups: regulator gene of glucosyltransferase (Rgg), Sil, lantibiotic systems, and LuxS/AI-2. The Rgg family of proteins, a conserved group of transcription factors that modify their activity in response to signaling peptides, has been shown to regulate genes involved in virulence, biofilm formation and competence. The sil locus, whose expression is regulated by the activity of signaling peptides and a putative two-component system (TCS), has been implicated on regulating genes involved with invasive disease in GAS isolates. Lantibiotic regulatory systems are involved in the production of bacteriocins and their autoregulation, and some of these genes have been shown to target both bacterial organisms as well as processes of survival inside the infected host. Finally AI-2 (dihydroxy pentanedione, DPD), synthesized by the LuxS enzyme in several bacteria including GAS, has been proposed to be a universal bacterial communication molecule. In this review we discuss the mechanisms of these four systems, the putative functions of their targets, and pose critical questions for future studies. PMID:25309879

Jimenez, Juan Cristobal; Federle, Michael J

2014-01-01

87

Quorum sensing in fungi – a review  

PubMed Central

Quorum sensing (QS) is a mechanism of microbial communication dependent on cell density that can regulate several behaviors in bacteria such as secretion of virulence factors, biofilm formation, competence and bioluminescence. The existence of fungal QS systems was revealed ten years ago after the discovery that farnesol controls filamentation in the pathogenic polymorphic fungus Candida albicans. In the past decade, farnesol has been shown to play multiple roles in C. albicans physiology as a signaling molecule and inducing detrimental effects on host cells and other microbes. In addition to farnesol, the aromatic alcohol tyrosol was also found to be a C. albicans QS molecule (QSM) controlling growth, morphogenesis and biofilm formation. In Saccharomyces cerevisiae, two other aromatic alcohols, phenylethanol and tryptophol were found to be QSMs regulating morphogenesis during nitrogen starvation conditions. Additionally, population density-dependent behaviors that resemble QS have been described in several other fungal species. Although fungal QS research is still in its infancy, its discovery has changed our views about the fungal kingdom and could eventually lead to the development of new antifungal therapeutics. PMID:22268493

ALBUQUERQUE, PATRÍCIA; CASADEVALL, ARTURO

2015-01-01

88

Quorum sensing in fungi--a review.  

PubMed

Quorum sensing (QS) is a mechanism of microbial communication dependent on cell density that can regulate several behaviors in bacteria such as secretion of virulence factors, biofilm formation, competence and bioluminescence. The existence of fungal QS systems was revealed ten years ago after the discovery that farnesol controls filamentation in the pathogenic polymorphic fungus Candida albicans. In the past decade, farnesol has been shown to play multiple roles in C. albicans physiology as a signaling molecule and inducing detrimental effects on host cells and other microbes. In addition to farnesol, the aromatic alcohol tyrosol was also found to be a C. albicans QS molecule (QSM) controlling growth, morphogenesis and biofilm formation. In Saccharomyces cerevisiae, two other aromatic alcohols, phenylethanol and tryptophol were found to be QSMs regulating morphogenesis during nitrogen starvation conditions. Additionally, population density-dependent behaviors that resemble QS have been described in several other fungal species. Although fungal QS research is still in its infancy, its discovery has changed our views about the fungal kingdom and could eventually lead to the development of new antifungal therapeutics. PMID:22268493

Albuquerque, Patrícia; Casadevall, Arturo

2012-05-01

89

Integrated analysis of bacterial quorum-sensing networks  

NASA Astrophysics Data System (ADS)

The regulation of gene expression is fundamental to most processes in cellular biology. At the transcriptional level, regulation occurs by the binding of specific proteins called transcription factors to DNA. Post-transcriptional regulation is often carried out by small RNAs which have become the focus of intense research activity recently. The talk will discuss the physics and biology of these two regulatory mechanisms by focusing on a specific biological system: quorum-sensing networks in bacteria. Quorum sensing is the process by which bacteria communicate to regulate gene expression in response to cell population density. Using an integrated approach which combines computational modeling, bioinformatics and experimental molecular biology, we are studying quorum-sensing pathways in bacteria. This approach led to the discovery of multiple regulatory small RNAs which are an integral part of the quorum-sensing pathway in Vibrio cholerae and Vibrio harveyi. Modeling of regulation of and by small RNAs in quorum sensing reveals the circuit characteristics controlling the transition from the low cell-density response to the high cell-density response.

Kulkarni, Rahul

2005-11-01

90

Quorum sensing negatively regulates chitinase in Vibrio harveyi.  

PubMed

Quorum sensing, bacterial cell-to-cell communication, regulates the virulence of Vibrio harveyi towards different hosts. Chitinase can be considered as a virulence factor because it helps pathogenic bacteria to attach to the host and to penetrate its tissues (e.g. in case of shrimp). Here, we show that quorum sensing negatively regulates chitinase in V. harveyi. Chitinolytic activity towards natural chitin from crab shells, the synthetic chitin derivative chitin azure, and fluorogenic chitin oligomers was significantly higher in a mutant in which the quorum-sensing system is completely inactivated when compared with a mutant in which the system is maximally active. Furthermore, the addition of signal molecule containing cell-free culture fluids decreased chitinase activity in a Harveyi Autoinducer 1 and Autoinducer 2-deficient double mutant. Finally, chitinase A mRNA levels were fivefold lower in the mutant in which the quorum-sensing system is maximally active when compared with the mutant in which the system is completely inactivated. [Correction added on 25 September 2009, after first online publication: the preceding sentence was corrected from 'Finally, chitinase A mRNA levels were fivefold lower in the mutant in which the quorum-sensing system is completely inactivated when compared with the mutant in which the system is maximally active.'] We argue that this regulation might help the vibrios to switch between host-associated and free-living life styles. PMID:23765997

Defoirdt, Tom; Darshanee Ruwandeepika, H A; Karunasagar, Indrani; Boon, Nico; Bossier, Peter

2010-02-01

91

Measurement of the Copy Number of the Master Quorum-Sensing Regulator of a Bacterial Cell  

E-print Network

Measurement of the Copy Number of the Master Quorum-Sensing Regulator of a Bacterial Cell Shu, Princeton, New Jersey; and § Howard Hughes Medical Institute, Chevy Chase, Maryland ABSTRACT Quorum-sensing on parameters such as the copy number of particular quorum-sensing proteins should contribute strongly

Mehta, Pankaj

92

A Cell-Based Model for Quorum Sensing in Heterogeneous Bacterial Colonies  

E-print Network

A Cell-Based Model for Quorum Sensing in Heterogeneous Bacterial Colonies Pontus Melke1 , Patrik small diffusing autoinducer molecules. The phenomenon, known as quorum sensing, has mainly been proposed microcolonies to investigate a quorum-sensing mechanism at a single cell level. We show that the model indeed

McFall-Ngai, Margaret

93

Measurement of the copy number of the master quorum-sensing regulator of a bacterial cell  

E-print Network

Measurement of the copy number of the master quorum-sensing regulator of a bacterial cell Shu information on parameters such as the copy number of particular quorum-sensing proteins should contribute strongly to understanding how the quorum-sensing network functions. Here we show that the copy number

Ong, N. P.

94

Active regulation of receptor ratios controls integration of quorum-sensing signals  

E-print Network

Active regulation of receptor ratios controls integration of quorum-sensing signals in Vibrio 8616; E-mail: wingreen@princeton.edu Received 20.1.11; accepted 19.4.11 Quorum sensing is a chemical exist in the quorum-sensing circuit of the model bacterium Vibrio harveyi. Using fluorescence microscopy

Mehta, Pankaj

95

Quorum-sensing-regulated transcriptional initiation of plasmid transfer and replication genes in  

E-print Network

Quorum-sensing-regulated transcriptional initiation of plasmid transfer and replication genes symbiosis plasmid pRL1JI is regulated by a cascade of gene induction involving three LuxR-type quorum-sensing the quorum-sensing cascade mediated via BisR and TraR, showing that the pRL1JI plasmid replication genes

Downie, J. Allan

96

LuxS quorum sensing: more than just a numbers game  

Microsoft Academic Search

Quorum sensing is a process of bacterial cell-to-cell communication involving the production and detection of extracellular signaling molecules called autoinducers. Quorum sensing allows populations of bacteria to collectively control gene expression, and thus synchronize group behavior. Processes controlled by quorum sensing are typically ones that are unproductive unless many bacteria act together. Most autoinducers enable intraspecies communication; however, a recently

Karina B Xavier; Bonnie L Bassler

2003-01-01

97

Traveling waves in response to a diffusing quorum sensing signal in spatially-extended bacterial colonies  

E-print Network

Traveling waves in response to a diffusing quorum sensing signal in spatially-extended bacterial, Oregon State University, Corvallis, OR 97331-4605, United States H I G H L I G H T S Quorum sensing (QS Propagating wave a b s t r a c t In the behavior known as quorum sensing (QS), bacteria release diffusible

De Leenheer, Patrick

98

A Quorum Sensing Regulated Small Volatile Molecule Reduces Acute Virulence and Promotes Chronic Infection  

E-print Network

A Quorum Sensing Regulated Small Volatile Molecule Reduces Acute Virulence and Promotes Chronic model. We report for the first time the existence of a quorum sensing (QS) regulated volatile molecule: Kesarwani M, Hazan R, He J, Que Y, Apidianakis Y, et al. (2011) A Quorum Sensing Regulated Small Volatile

Paris-Sud XI, Université de

99

Edinburgh Research Explorer Combinatorial quorum sensing allows bacteria to resolve their  

E-print Network

Edinburgh Research Explorer Combinatorial quorum sensing allows bacteria to resolve their social-Phillips, TC, Ivens, A, Diggle, SP & Brown, SP 2014, 'Combinatorial quorum sensing allows bacteria to resolve. 2014 #12;Combinatorial quorum sensing allows bacteria to resolve their social and physical environment

Millar, Andrew J.

100

Quorum sensing is necessary for the virulence of Pseudomonas aeruginosa during urinary tract infection  

Microsoft Academic Search

Quorum sensing is a signaling pathway used by bacteria to monitor their population density by detecting small diffusible molecules. To understand the role of quorum sensing in pathogenesis of urinary tract infections, wild type Pseudomonas aeruginosa, having both functional las and rhl quorum sensing systems, and its isogenic single and double mutants were used in a mouse model of ascending

Ravi Kumar; Sanjay Chhibber; Kusum Harjai

2009-01-01

101

Disruption of quorum sensing in Vibrio harveyi by the AiiA protein of Bacillus thuringiensis  

Microsoft Academic Search

Quorum sensing is a mechanism in which bacteria coordinate the expression of certain genes in response to their population density by producing, releasing and detecting signal molecules called autoinducers. Quorum sensing is responsible for controlling a plethora of virulence genes in several bacterial pathogens. Disruption of the quorum sensing system of Vibrio harveyi has been proposed as a new anti-infective

Fangfang Bai; Yin Han; Jixiang Chen; Xiao-Hua Zhang

2008-01-01

102

Towards a P Systems Pseudomonas Quorum Sensing Model  

E-print Network

is a particular form of cell-to-cell communication in bacteria which exploits the concentration of a particular that exploits quorum sensing communication to synchronize individuals in a colony and this leads to an increase virulence factors only when it senses that the bacteria population has reached a certain threshold level

Gheorghe, Marian

103

Computational modeling of the quorum-sensing network in bacteria  

Microsoft Academic Search

Certain species of bacteria are able produce and sense the concentration of small molecules called autodinducers in order to coordinate gene regulation in response to population density, a process known as ``quorum-sensing''. The resulting regulation of gene expression involves both transcriptional and post-transcriptional regulators. In particular, the species of bacteria in the Vibrio genus use small RNAs to regulate the

Andrew Fenley; Suman Banik; Rahul Kulkarni

2007-01-01

104

A Direct Pre-screen for Marine Bacteria Producing Compounds Inhibiting Quorum Sensing Reveals Diverse Planktonic Bacteria that are Bioactive.  

PubMed

A promising new strategy in antibacterial research is inhibition of the bacterial communication system termed quorum sensing. In this study, a novel and rapid pre-screening method was developed to detect the production of chemical inhibitors of this system (quorum-quenching compounds) by bacteria isolated from marine and estuarine waters. This method involves direct screening of mixed populations on an agar plate, facilitating specific isolation of bioactive colonies. The assay showed that between 4 and 46 % of culturable bacteria from various samples were bioactive, and of the 95 selectively isolated bacteria, 93.7 % inhibited Vibrio harveyi bioluminescence without inhibiting growth, indicating potential production of quorum-quenching compounds. Of the active isolates, 21 % showed further activity against quorum-sensing-regulated pigment production by Serratia marcescens. The majority of bioactive isolates were identified by 16S ribosomal DNA (rDNA) amplification and sequencing as belonging to the genera Vibrio and Pseudoalteromonas. Extracts of two strongly bioactive Pseudoalteromonas isolates (K1 and B2) were quantitatively assessed for inhibition of growth and quorum-sensing-regulated processes in V. harveyi, S. marcescens and Chromobacterium violaceum. Extracts of the isolates reduced V. harveyi bioluminescence by as much as 98 % and C. violaceum pigment production by 36 % at concentrations which had no adverse effect on growth. The activity found in the extracts indicated that the isolates may produce quorum-quenching compounds. This study further supports the suggestion that quorum quenching may be a common attribute among culturable planktonic marine and estuarine bacteria. PMID:25082352

Linthorne, Jamie S; Chang, Barbara J; Flematti, Gavin R; Ghisalberti, Emilio L; Sutton, David C

2015-02-01

105

Modeling of signal transduction in bacterial quorum-sensing  

NASA Astrophysics Data System (ADS)

Several species of bacteria are able to coordinate gene regulation in response to population density, a process known as ``quorum-sensing''. Quorum-sensing bacteria produce, secrete, and detect signal molecules called autoinducers. For several species of bacteria in the Vibrio genus, recent results have shown that the external autoinducer concentrations control the expression of regulatory small RNA(s) which are critical to the process of quorum-sensing. We present a theoretical analysis of the network which relates the rate of small RNA expression to the external autoinducer concentrations. We relate the results from our modeling to previous experimental observations and suggest new experiments based on testable predictions of the model.

Fenley, Andrew; Banik, Suman; Kulkarni, Rahul

2006-03-01

106

Mathematical Modeling of Quorum-Sensing Control in Biofilms  

Microsoft Academic Search

\\u000a This chapter begins with an overview of the relevant\\u000a \\u0009 literature on theoretical approaches to modeling biofilms, quorum\\u000a \\u0009 sensing in bacteria, and anti-quorum-sensing treatment. Following\\u000a \\u0009 this, new mathematical models are proposed to investigate\\u000a \\u0009 anti-quorum-sensing treatment in batch cultures and in biofilm\\u000a \\u0009 environments. Details for the models' derivation are aimed so that\\u000a \\u0009 readers with a nonmathematical background will have a good idea of\\u000a \\u0009 how

John Ward

107

Biomimicry of quorum sensing using bacterial lifecycle model  

PubMed Central

Background Recent microbiologic studies have shown that quorum sensing mechanisms, which serve as one of the fundamental requirements for bacterial survival, exist widely in bacterial intra- and inter-species cell-cell communication. Many simulation models, inspired by the social behavior of natural organisms, are presented to provide new approaches for solving realistic optimization problems. Most of these simulation models follow population-based modelling approaches, where all the individuals are updated according to the same rules. Therefore, it is difficult to maintain the diversity of the population. Results In this paper, we present a computational model termed LCM-QS, which simulates the bacterial quorum-sensing (QS) mechanism using an individual-based modelling approach under the framework of Agent-Environment-Rule (AER) scheme, i.e. bacterial lifecycle model (LCM). LCM-QS model can be classified into three main sub-models: chemotaxis with QS sub-model, reproduction and elimination sub-model and migration sub-model. The proposed model is used to not only imitate the bacterial evolution process at the single-cell level, but also concentrate on the study of bacterial macroscopic behaviour. Comparative experiments under four different scenarios have been conducted in an artificial 3-D environment with nutrients and noxious distribution. Detailed study on bacterial chemotatic processes with quorum sensing and without quorum sensing are compared. By using quorum sensing mechanisms, artificial bacteria working together can find the nutrient concentration (or global optimum) quickly in the artificial environment. Conclusions Biomimicry of quorum sensing mechanisms using the lifecycle model allows the artificial bacteria endowed with the communication abilities, which are essential to obtain more valuable information to guide their search cooperatively towards the preferred nutrient concentrations. It can also provide an inspiration for designing new swarm intelligence optimization algorithms, which can be used for solving the real-world problems. PMID:23815296

2013-01-01

108

Information processing and signal integration in bacterial quorum sensing  

NASA Astrophysics Data System (ADS)

Bacteria communicate with each other using secreted chemical signaling molecules called autoinducers (AIs) in a process known as quorum sensing. Quorum sensing enables bacteria to collectively regulate their behavior depending on the number and/or species of bacteria present. The quorum-sensing network of the marine-bacteria Vibrio harveyi consists of three AIs encoding distinct ecological information, each detected by its own histidine-kinase sensor protein. The sensor proteins all phosphorylate a common response regulator and transmit sensory information through a shared phosphorelay that regulates expression of downstream quorum-sensing genes. Despite detailed knowledge of the Vibrio quorum-sensing circuit, it is still unclear how and why bacteria integrate information from multiple input signals to coordinate collective behaviors. Here we develop a mathematical framework for analyzing signal integration based on Information Theory and use it to show that bacteria must tune the kinase activities of sensor proteins in order to transmit information from multiple inputs. This is demonstrated within a quantitative model that allows us to quantify how much Vibrio's learn about individual inputs and explains experimentally measured input-output relations. Furthermore, we predicted and experimentally verified that bacteria manipulate the production rates of AIs in order to increase information transmission and argue that the quorum-sensing circuit is designed to coordinate a multi-cellular developmental program. Our results show that bacteria can successfully learn about multiple signals even when they are transmitted through a shared pathway and suggest that Information Theory may be a powerful tool for analyzing biological signaling networks.

Mehta, Pankaj

2009-03-01

109

Structural Basis for Native Agonist and Synthetic Inhibitor Recognition by the Pseudomonas aeruginosa Quorum Sensing Regulator PqsR (MvfR)  

PubMed Central

Bacterial populations co-ordinate gene expression collectively through quorum sensing (QS), a cell-to-cell communication mechanism employing diffusible signal molecules. The LysR-type transcriptional regulator (LTTR) protein PqsR (MvfR) is a key component of alkyl-quinolone (AQ)-dependent QS in Pseudomonas aeruginosa. PqsR is activated by 2-alkyl-4-quinolones including the Pseudomonas quinolone signal (PQS; 2-heptyl-3-hydroxy-4(1H)-quinolone), its precursor 2-heptyl-4-hydroxyquinoline (HHQ) and their C9 congeners, 2-nonyl-3-hydroxy-4(1H)-quinolone (C9-PQS) and 2-nonyl-4-hydroxyquinoline (NHQ). These drive the autoinduction of AQ biosynthesis and the up-regulation of key virulence determinants as a function of bacterial population density. Consequently, PqsR constitutes a potential target for novel antibacterial agents which attenuate infection through the blockade of virulence. Here we present the crystal structures of the PqsR co-inducer binding domain (CBD) and a complex with the native agonist NHQ. We show that the structure of the PqsR CBD has an unusually large ligand-binding pocket in which a native AQ agonist is stabilized entirely by hydrophobic interactions. Through a ligand-based design strategy we synthesized and evaluated a series of 50 AQ and novel quinazolinone (QZN) analogues and measured the impact on AQ biosynthesis, virulence gene expression and biofilm development. The simple exchange of two isosteres (OH for NH2) switches a QZN agonist to an antagonist with a concomitant impact on the induction of bacterial virulence factor production. We also determined the complex crystal structure of a QZN antagonist bound to PqsR revealing a similar orientation in the ligand binding pocket to the native agonist NHQ. This structure represents the first description of an LTTR-antagonist complex. Overall these studies present novel insights into LTTR ligand binding and ligand-based drug design and provide a chemical scaffold for further anti-P. aeruginosa virulence drug development by targeting the AQ receptor PqsR. PMID:23935486

Ilangovan, Aravindan; Fletcher, Matthew; Rampioni, Giordano; Pustelny, Christian; Rumbaugh, Kendra; Heeb, Stephan; Cámara, Miguel; Truman, Alex; Chhabra, Siri Ram; Emsley, Jonas; Williams, Paul

2013-01-01

110

Transcriptional control of the quorum sensing response in yeast.  

PubMed

Quorum sensing is a process of intercellular communication. It allows individual cells to assess population density and to co-ordinate behaviour by secreting and sensing communication molecules. In the yeast Saccharomyces cerevisiae, the communication molecules are the aromatic alcohols tryptophol and phenylethanol, and quorum sensing regulates the transition between the solitary yeast form and the filamentous form. Though it is known that addition of these communication molecules to yeast cultures causes large changes in gene expression, how these changes are orchestrated and whether this system is conserved in related fungal species is still unknown. In this work, by employing an integrated computational approach that makes use of large-scale genomics datasets, such as ChIP-ChIP and expression analysis upon deletion and over-expression of transcriptional factors, we predict CAT8 and MIG1 as key transcriptional regulators that control the differential expression of the genes affected by aromatic alcohol communication. In addition, through a comparative genomic analysis involving 31 fungal species, we show that the S. cerevisiae quorum sensing system is a recent evolutionary innovation and that the genes which are differentially expressed upon treatment with these molecules are distributed across the genome in a highly non-random manner. The identified transcription factors will aid in further unravelling the molecular mechanisms of S. cerevisiae quorum sensing and may facilitate the engineering of regulatory circuits for applications such as the expression of heterologous proteins via aromatic alcohols. PMID:20024075

Wuster, Arthur; Babu, M Madan

2010-01-01

111

Ratio-dependent quantity discrimination in quorum sensing ants.  

PubMed

To optimise behaviour, organisms require information on the quantity of various components of their environment, and the ability of animals to discriminate quantity has been a subject of considerable recent interest. This body of research hints at generalised mechanisms of quantity discrimination in vertebrates, but data on invertebrates are still relatively scarce. In this study, I present data on the quantification abilities of an invertebrate in a novel context: quorum sensing. Quorum sensing generates a behavioural response in group-living animals once a threshold number of individuals, a 'quorum', is detected performing some key action. This process forms the basis for consensus decision-making in many species and allows group-living organisms to decide among mutually exclusive alternatives without compromising group integrity. To determine when a quorum is achieved, individuals must assess the number of group members performing the key action. Social insects employ quorum decisions to decide among potential nest sites when searching for a new home. In the Japanese ant, Myrmecina nipponica, quorum thresholds increase with colony size, providing an opportunity to assess the accuracy of quantity discrimination at different stimulus magnitudes. In this study, I demonstrate that the variation in individual quorum thresholds around the mean increases with increasing colony size. This indicates that the quantity discrimination ability of ants decreases with stimulus magnitude, and thus exhibits ratio dependence in the manner of Weber's Law. This may have implications for the accuracy of consensus decision-making and other collective actions in a range of group-living organisms. PMID:24844665

Cronin, Adam L

2014-11-01

112

An Environment Aware P-System Model of Quorum Sensing  

E-print Network

of the most important mechanisms for bacterial cell-to-cell communication and behavior coordination under-wide attack nec- essary to breach host's immunological defences. Other bacteria (both Gram- negative and Gram. 2 Cell-to-Cell Communication by Means of Quorum Sensing The QS mechanism is a communication strategy

Krasnogor, Natalio

113

An Environment Aware P-System Model of Quorum Sensing  

E-print Network

. In this paper we will focus on one of the most important mechanisms for bacterial cell-to-cell communication- tack necessary to breach host's immunological defences. Other bacteria (both Gram-negative and Gram. 2 Cell-to-Cell Communication by Means of Quorum Sensing The QS mechanism is a communication strategy

Gheorghe, Marian

114

Sociomicrobiology: the connections between quorum sensing and biofilms  

Microsoft Academic Search

In the past decade, significant debate has surrounded the relative contributions of genetic determinants versus environmental conditions to certain types of human behavior. While this debate goes on, it is with a certain degree of irony that microbiologists studying aspects of bacterial community behavior face the same questions. Information regarding two social phenomena exhibited by bacteria, quorum sensing and biofilm

Matthew R. Parsek; E. P. Greenberg

2005-01-01

115

The Evolutionary History of Quorum-Sensing Systems in Bacteria  

Microsoft Academic Search

Communication among bacterial cells through quorum-sensing (QS) systems is used to regulate ecologically and medically important traits, including virulence to hosts. QS is widespread in bacteria; it has been demonstrated experimentally in diverse phylogenetic groups, and homologs to the implicated genes have been discovered in a large proportion of sequenced bacterial genomes. The widespread distribution of the underlying gene families

Emmanuelle Lerat; Nancy A. Moran

2004-01-01

116

The Evolution of Quorum Sensing in Bacterial Biofilms  

Microsoft Academic Search

Bacteria have fascinating and diverse social lives. They display coordinated group behaviors regulated by quorum-sensing systems that detect the density of other bacteria around them. A key example of such group behavior is biofilm formation, in which communities of cells attach to a surface and envelope themselves in secreted polymers. Curiously, after reaching high cell density, some bacterial species activate

Carey D Nadell; Joao B Xavier; Simon A Levin; Kevin R Foster

2008-01-01

117

Confinement-induced quorum sensing of individual Staphylococcus aureus bacteria  

Microsoft Academic Search

It is postulated that in addition to cell density, other factors such as the dimensions and diffusional characteristics of the environment could influence quorum sensing (QS) and induction of genetic reprogramming. Modeling studies predict that QS may operate at the level of a single cell, but, owing to experimental challenges, the potential benefits of QS by individual cells remain virtually

Eric C Carnes; DeAnna M Lopez; Niles P Donegan; Ambrose Cheung; Hattie Gresham; Graham S Timmins; C Jeffrey Brinker

2009-01-01

118

Pandoraea sp. RB-44, a novel quorum sensing soil bacterium.  

PubMed

Proteobacteria are known to communicate via signaling molecules and this process is known as quorum sensing. The most commonly studied quorum sensing molecules are N-acylhomoserine lactones (AHLs) that consists of a homoserine lactone moiety and an N-acyl side chain with various chain lengths and degrees of saturation at the C-3 position. We have isolated a bacterium, RB-44, from a site which was formally a landfill dumping ground. Using matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry analysis, this isolate was identified as a Pandoraea sp.which was then screened for AHL production using biosensors which indicated its quorum sensing properties. To identify the AHL profile of Pandoraea sp. RB-44, we used high resolution tandem mass spectrometry confirming that this isolate produced N-octanoylhomoserine lactone (C8-HSL). To the best of our knowledge, this is the first report that showed quorum sensing activity exhibited by Pandoraea sp. Our data add Pandoraea sp. to the growing number of bacteria that possess QS systems. PMID:24145919

Han-Jen, Robson Ee; Wai-Fong, Yin; Kok-Gan, Chan

2013-01-01

119

Quorum sensing-controlled gene expression in lactic acid bacteria  

Microsoft Academic Search

Quorum sensing in lactic acid bacteria (LAB) involves peptides that are directly sensed by membrane-located histidine kinases, after which the signal is transmitted to an intracellular response regulator. This regulator in turn activates transcription of target genes, that commonly include the structural gene for the inducer molecule. The two-component signal-transduction machinery has proven to be indispensable for transcription activation and

Oscar P. Kuipers; Michiel Kleerebezem; Willem M. de Vos

1998-01-01

120

Effects of Antibiotics on Quorum Sensing in Pseudomonas aeruginosa?  

PubMed Central

During infection, Pseudomonas aeruginosa employs bacterial communication (quorum sensing [QS]) to coordinate the expression of tissue-damaging factors. QS-controlled gene expression plays a pivotal role in the virulence of P. aeruginosa, and QS-deficient mutants cause less severe infections in animal infection models. Treatment of cystic fibrosis (CF) patients chronically infected with P. aeruginosa with the macrolide antibiotic azithromycin (AZM) has been demonstrated to improve the clinical outcome. Several studies indicate that AZM may accomplish its beneficial action in CF patients by impeding QS, thereby reducing the pathogenicity of P. aeruginosa. This led us to investigate whether QS inhibition is a common feature of antibiotics. We present the results of a screening of 12 antibiotics for their QS-inhibitory activities using a previously described QS inhibitor selector 1 strain. Three of the antibiotics tested, AZM, ceftazidime (CFT), and ciprofloxacin (CPR), were very active in the assay and were further examined for their effects on QS-regulated virulence factor production in P. aeruginosa. The effects of the three antibiotics administered at subinhibitory concentrations were investigated by use of DNA microarrays. Consistent results from the virulence factor assays, reverse transcription-PCR, and the DNA microarrays support the finding that AZM, CFT, and CPR decrease the expression of a range of QS-regulated virulence factors. The data suggest that the underlying mechanism may be mediated by changes in membrane permeability, thereby influencing the flux of N-3-oxo-dodecanoyl-l-homoserine lactone. PMID:18644954

Skindersoe, Mette E.; Alhede, Morten; Phipps, Richard; Yang, Liang; Jensen, Peter O.; Rasmussen, Thomas B.; Bjarnsholt, Thomas; Tolker-Nielsen, Tim; Høiby, Niels; Givskov, Michael

2008-01-01

121

The Vibrio campbellii quorum sensing signals have a different impact on virulence of the bacterium towards different crustacean hosts.  

PubMed

Pathogenic bacteria communicate with small signal molecules in a process called quorum sensing, and they often use different signal molecules to regulate virulence gene expression. Vibrio campbellii, one of the major pathogens of aquatic organisms, regulates virulence gene expression by a three channel quorum sensing system. Here we show that although they use a common signal transduction cascade, the signal molecules have a different impact on the virulence of the bacterium towards different hosts, i.e. the brine shrimp Artemia franciscana and the commercially important giant freshwater prawn Macrobrachium rosenbergii. These results suggest that the use of multiple types of signal molecules to regulate virulence gene expression is one of the features that allow bacteria to infect different hosts. Our findings emphasize that it is highly important to study the efficacy of quorum sensing inhibitors as novel biocontrol agents under conditions that are as close as possible to the clinical situation. PMID:24055027

Pande, Gde Sasmita Julyantoro; Natrah, Fatin Mohd Ikhsan; Sorgeloos, Patrick; Bossier, Peter; Defoirdt, Tom

2013-12-27

122

Transcriptome analysis of acyl-homoserine lactone-based quorum sensing regulation in Yersinia pestis [corrected].  

PubMed

The etiologic agent of bubonic plague, Yersinia pestis, senses self-produced, secreted chemical signals in a process named quorum sensing. Though the closely related enteric pathogen Y. pseudotuberculosis uses quorum sensing system to regulate motility, the role of quorum sensing in Y. pestis has been unclear. In this study we performed transcriptional profiling experiments to identify Y. pestis quorum sensing regulated functions. Our analysis revealed that acyl-homoserine lactone-based quorum sensing controls the expression of several metabolic functions. Maltose fermentation and the glyoxylate bypass are induced by acyl-homoserine lactone signaling. This effect was observed at 30°C, indicating a potential role for quorum sensing regulation of metabolism at temperatures below the normal mammalian temperature. It is proposed that utilization of alternative carbon sources may enhance growth and/or survival during prolonged periods in natural habitats with limited nutrient sources, contributing to maintenance of plague in nature. PMID:23620823

LaRock, Christopher N; Yu, Jing; Horswill, Alexander R; Parsek, Matthew R; Minion, F Chris

2013-01-01

123

Transcriptome Analysis of Acetyl-Homoserine Lactone-Based Quorum Sensing Regulation in Yersinia pestis  

PubMed Central

The etiologic agent of bubonic plague, Yersinia pestis, senses self-produced, secreted chemical signals in a process named quorum sensing. Though the closely related enteric pathogen Y. pseudotuberculosis uses quorum sensing system to regulate motility, the role of quorum sensing in Y. pestis has been unclear. In this study we performed transcriptional profiling experiments to identify Y. pestis quorum sensing regulated functions. Our analysis revealed that acyl-homoserine lactone-based quorum sensing controls the expression of several metabolic functions. Maltose fermentation and the glyoxylate bypass are induced by acyl-homoserine lactone signaling. This effect was observed at 30°C, indicating a potential role for quorum sensing regulation of metabolism at temperatures below the normal mammalian temperature. It is proposed that utilization of alternative carbon sources may enhance growth and/or survival during prolonged periods in natural habitats with limited nutrient sources, contributing to maintenance of plague in nature. PMID:23620823

Horswill, Alexander R.; Parsek, Matthew R.; Minion, F. Chris

2013-01-01

124

Quorum Sensing and Bacterial Social Interactions in Biofilms  

PubMed Central

Many bacteria are known to regulate their cooperative activities and physiological processes through a mechanism called quorum sensing (QS), in which bacterial cells communicate with each other by releasing, sensing and responding to small diffusible signal molecules. The ability of bacteria to communicate and behave as a group for social interactions like a multi-cellular organism has provided significant benefits to bacteria in host colonization, formation of biofilms, defense against competitors, and adaptation to changing environments. Importantly, many QS-controlled activities have been involved in the virulence and pathogenic potential of bacteria. Therefore, understanding the molecular details of quorum sensing mechanisms and their controlled social activities may open a new avenue for controlling bacterial infections. PMID:22736963

Li, Yung-Hua; Tian, Xiaolin

2012-01-01

125

RETRACTED ARTICLE: Quorum-sensing of bacteria and its application  

NASA Astrophysics Data System (ADS)

Quorum sensing, or auto induction, as a cell density dependent signaling mechanism in many microorganisms, is triggered via auto inducers which passively diffuse across the bacterial envelope and therefore intracellulaly accumulate only at higher bacterial densities to regulate specialized processes such as genetic competence, bioluminescence, virulence and sporulation. N-acyl homoserine lactones are the most common type of signal molecules. Aquaculture is one of the fastest-growing food-producing industries, but disease outbreaks caused by pathogenic bacteria are a significant constraint on the development of the sector worldwide. Many of these pathogens have been found to be controlled by their quorum sensing systems. As there is relevance between the pathogenic bacteria's virulence factor expression and their auto inducers, quorum quenching is a new effective anti-infective strategy to control infections caused by bacterial pathogens in aquaculture. The techniques used to do this mainly include the following: (1) the inhibition of signal molecule biosynthesis, (2) blocking signal transduction, and (3) chemical inactivation and biodegradation of signal molecules. To provide a basis for finding alternative means of controlling aquatic diseases by quorum quenching instead of treatment by antibiotics and disinfectants, we will discuss the examination, purification and identification of auto inducers in this paper.

Jiang, Guoliang; Su, Mingxia

2009-12-01

126

Quorum sensing enhancement of the stress response promotes resistance to quorum quenching and prevents social cheating.  

PubMed

Quorum sensing (QS) coordinates the expression of virulence factors and allows bacteria to counteract the immune response, partly by increasing their tolerance to the oxidative stress generated by immune cells. Despite the recognized role of QS in enhancing the oxidative stress response, the consequences of this relationship for the bacterial ecology remain unexplored. Here we demonstrate that QS increases resistance also to osmotic, thermal and heavy metal stress. Furthermore a QS-deficient lasR rhlR mutant is unable to exert a robust response against H2O2 as it has less induction of catalase and NADPH-producing dehydrogenases. Phenotypic microarrays revealed that the mutant is very sensitive to several toxic compounds. As the anti-oxidative enzymes are private goods not shared by the population, only the individuals that produce them benefit from their action. Based on this premise, we show that in mixed populations of wild-type and the mexR mutant (resistant to the QS inhibitor furanone C-30), treatment with C-30 and H2O2 increases the proportion of mexR mutants; hence, oxidative stress selects resistance to QS compounds. In addition, oxidative stress alone strongly selects for strains with active QS systems that are able to exert a robust anti oxidative response and thereby decreases the proportion of QS cheaters in cultures that are otherwise prone to invasion by cheats. As in natural environments stress is omnipresent, it is likely that this QS enhancement of stress tolerance allows cells to counteract QS inhibition and invasions by social cheaters, therefore having a broad impact in bacterial ecology. PMID:24936763

García-Contreras, Rodolfo; Nuñez-López, Leslie; Jasso-Chávez, Ricardo; Kwan, Brian W; Belmont, Javier A; Rangel-Vega, Adrián; Maeda, Toshinari; Wood, Thomas K

2015-01-01

127

Global Analysis of the Burkholderia thailandensis Quorum Sensing-Controlled Regulon  

PubMed Central

Burkholderia thailandensis contains three acyl-homoserine lactone quorum sensing circuits and has two additional LuxR homologs. To identify B. thailandensis quorum sensing-controlled genes, we carried out transcriptome sequencing (RNA-seq) analyses of quorum sensing mutants and their parent. The analyses were grounded in the fact that we identified genes coding for factors shown previously to be regulated by quorum sensing among a larger set of quorum-controlled genes. We also found that genes coding for contact-dependent inhibition were induced by quorum sensing and confirmed that specific quorum sensing mutants had a contact-dependent inhibition defect. Additional quorum-controlled genes included those for the production of numerous secondary metabolites, an uncharacterized exopolysaccharide, and a predicted chitin-binding protein. This study provides insights into the roles of the three quorum sensing circuits in the saprophytic lifestyle of B. thailandensis, and it provides a foundation on which to build an understanding of the roles of quorum sensing in the biology of B. thailandensis and the closely related pathogenic Burkholderia pseudomallei and Burkholderia mallei. PMID:24464461

Majerczyk, Charlotte; Brittnacher, Mitchell; Jacobs, Michael; Armour, Christopher D.; Radey, Mathew; Schneider, Emily; Phattarasokul, Somsak; Bunt, Richard

2014-01-01

128

Analysis of Autoinducer-2 Quorum Sensing in Yersinia pestis  

PubMed Central

The autoinducer-2 (AI-2) quorum-sensing system has been linked to diverse phenotypes and regulatory changes in pathogenic bacteria. In the present study, we performed a molecular and biochemical characterization of the AI-2 system in Yersinia pestis, the causative agent of plague. In strain CO92, the AI-2 signal is produced in a luxS-dependent manner, reaching maximal levels of 2.5 ?M in the late logarithmic growth phase, and both wild-type and pigmentation (pgm) mutant strains made equivalent levels of AI-2. Strain CO92 possesses a chromosomal lsr locus encoding factors involved in the binding and import of AI-2, and confirming this assignment, an lsr deletion mutant increased extracellular pools of AI-2. To assess the functional role of AI-2 sensing in Y. pestis, microarray studies were conducted by comparing ?pgm strain R88 to a ?pgm ?luxS mutant or a quorum-sensing-null ?pgm ?ypeIR ?yspIR ?luxS mutant at 37°C. Our data suggest that AI-2 quorum sensing is associated with metabolic activities and oxidative stress genes that may help Y. pestis survive at the host temperature. This was confirmed by observing that the luxS mutant was more sensitive to killing by hydrogen peroxide, suggesting a potential requirement for AI-2 in evasion of oxidative damage. We also show that a large number of membrane protein genes are controlled by LuxS, suggesting a role for quorum sensing in membrane modeling. Altogether, this study provides the first global analysis of AI-2 signaling in Y. pestis and identifies potential roles for the system in controlling genes important to disease. PMID:23959719

Yu, Jing; Madsen, Melissa L.; Carruthers, Michael D.; Phillips, Gregory J.; Kavanaugh, Jeffrey S.; Boyd, Jeff M.; Horswill, Alexander R.

2013-01-01

129

Characterization of Quorum Sensing and Quorum Quenching Soil Bacteria Isolated from Malaysian Tropical Montane Forest  

PubMed Central

We report the production and degradation of quorum sensing N-acyl-homoserine lactones by bacteria isolated from Malaysian montane forest soil. Phylogenetic analysis indicated that these isolates clustered closely to the genera of Arthrobacter, Bacillus and Pseudomonas. Quorum quenching activity was detected in six isolates of these three genera by using a series of bioassays and rapid resolution liquid chromatography analysis. Biosensor screening and high resolution liquid chromatography-mass spectrometry analysis revealed the production of N-dodecanoyl-L-homoserine lactone (C12-HSL) by Pseudomonas frederiksbergensis (isolate BT9). In addition to degradation of a wide range of N-acyl-homoserine lactones, Arthrobacter and Pseudomonas spp. also degraded p-coumaroyl-homoserine lactone. To the best of our knowledge, this is the first documentation of Arthrobacter and Pseudomonas spp. capable of degrading p-coumaroyl-homoserine lactone and the production of C12-HSL by P. frederiksbergensis. PMID:22666062

Chong, Teik-Min; Koh, Chong-Lek; Sam, Choon-Kook; Choo, Yeun-Mun; Yin, Wai-Fong; Chan, Kok-Gan

2012-01-01

130

Stationary-Phase Quorum-Sensing Signals Affect Autoinducer-2 and Gene Expression in Escherichia coli  

Microsoft Academic Search

Quorum sensing via autoinducer-2 (AI-2) has been identified in different strains, including those from Escherichia, Vibrio, Streptococcus, and Bacillus species, and previous studies have suggested the existence of additional quorum-sensing signals working in the stationary phase of Escherichia coli cultures. To investigate the presence and global effect of these possible quorum-sensing signals other than AI-2, DNA microarrays were used to

Dacheng Ren; Laura A. Bedzyk; Rick W. Ye; Stuart M. Thomas; Thomas K. Wood

2004-01-01

131

Contribution of Quorum Sensing to the Virulence of Pseudomonas aeruginosa in Burn Wound Infections  

Microsoft Academic Search

The Pseudomonas aeruginosa quorum-sensing systems, las and rhl, control the production of numerous virulence factors. In this study, we have used the burned-mouse model to examine the contribution of quorum-sensing systems to the pathogenesis of P. aeruginosa infections in burn wounds. Different quorum- sensing mutants of P. aeruginosa PAO1 that were defective in the lasR, lasI ,o rrhlI gene or

KENDRA P. RUMBAUGH; JOHN A. GRISWOLD; BARBARA H. IGLEWSKI; ABDUL N. HAMOOD

1999-01-01

132

NUROP Congress Paper A Second Quorum Sensing Regulon in Burkholderia pseudomallei  

Microsoft Academic Search

Burkholderia pseudomallei, a Gram-negative soil bacterium, is the causative agent of melioidosis. Quorum sensing is a mechanism responsible for the regulated expression of virulence genes in many bacterial pathogens. The first quorum sensing regulon in B. pseudomallei, Ai s\\/Air, was recently identified in our laboratory. The report describes the identification of a second quorum sensing regulon, RhlI\\/RhlR, in B. pseudomallei

133

[New class of Acyl-homoserine lactone quorum sensing signals].  

PubMed

Bacteria are known to regulate various gene expressions producing particular signal molecules termed "Auto-inducers" in the cell density-dependent manner. This physiological phenomenon termed "Quorum Sensing" has been discovered in many bacteria including normal bacterial flora and pathogens. Among Auto-inducers, Acyl-homoserine lactone has been best studied, which is leading with the human opportunistic pathogen, Pseudomonas aeruginosa. AHLs contain linear fatty-acyl side chains in the homoserine lactone moiety. Although the variation and specificity are determined by the sort of fatty acids, the number of fatty acid variations (approximately thirty) is absolutely less than that of AHL producers. However, new types of AHLs that have non-fatty acids in the side chain have been recently reported. This innovative finding enables to account for the diversity of AHL producing bacteria and also extend Quorum Sensing studies. In this paper, we will introduce novel classes of AHLs and their unique properties. PMID:24369303

Hirakawa, Hidetada; Tomita, Haruyoshi

2013-01-01

134

In vitro anti-quorum sensing activity of phytol.  

PubMed

Anti-quorum sensing activity of the diterpene phytol was evaluated in vitro for the first time. This compound (at three sub-MIC concentrations - 0.5, 0.25 and 0.125 MIC, respectively) reduced the formation of Pseudomonas aeruginosa PAO1 biofilm in the range of 74.00-84.33% exhibiting higher activity than the both positive controls used, streptomycin and ampicillin. Phytol (0.5 MIC) also effectively reduced P. aeruginosa twitching and flagella motility. Indeed, the bacteria treated were incapable of producing a twitching zone and had almost round, smooth and regular colony edges. Finally, the tested compound (0.5 MIC) exhibited good P. aeruginosa pyocyanin inhibitory activity (51.94%) practically to the same extent as streptomycin (52.09%). According to the experimental data obtained, this phytol property may inspire design of medical foods targeting P. aeruginosa quorum sensing activity. PMID:25103916

Pejin, Boris; Ciric, Ana; Glamoclija, Jasmina; Nikolic, Milos; Sokovic, Marina

2015-02-01

135

Role of quorum sensing in the pathogenicity of Burkholderia pseudomallei  

Microsoft Academic Search

Burkholderia pseudomallei is the causative agent of human and animal melioidosis. The role of quorum sensing (QS) in the in vivo pathogenicity of B. pseudomallei via inhalational exposure of BALB\\/c mice and intraperitoneal challenge of Syrian hamsters has not been reported. This investigation demonstrates that B. pseudomallei encodes a minimum of three luxI and five luxR homologues that are involved

Ricky L. Ulrich; David DeShazer; Ernst E. Brueggemann; Harry B. Hines; Petra C. Oyston; Jeffrey A. Jeddeloh

2004-01-01

136

(2) DNA O(n^5) Quorum-Sensing Lux  

E-print Network

- 1 - ( ) ( ) DNA RNA DNA RNA DNA DNA 2 DNA #12;- 2 - 17 6 (1) (2) DNA O(n^5) (3) Quorum-Sensing Lux (4) (5) LMNtal ambient LMNtal (1) (2) DNA (3) DNA (4) DNA (5) DNA (1) DNA ANP-96 (Precision System Science ) (2) RTRACS DNA RTRACS (3) in vivo in vivo (4) DNA trans cis 1/10 (5) DNA-PNA DNA DNA DNA DNA DNA

Hagiya, Masami

137

QUORUM SENSING: Cell-to-Cell Communication in Bacteria  

Microsoft Academic Search

Abstract Bacteria communicate,with,one,another,using,chemical,signal molecules. As in higher organisms, the information supplied by these molecules is critical for synchronizing,the activities of large groups of cells. In bacteria, chemical communication involves producing, re- leasing, detecting, and responding to small hormone-like molecules termed autoinducers. This process, termed quorum sensing, allows bacteria to monitor,the environment,for other bacteria and to al- ter behavior,on a population-wide,scale

Christopher M. Waters; Bonnie L. Bassler

2005-01-01

138

Quorum Sensing-Dependent Biofilms Enhance Colonization in Vibrio cholerae  

Microsoft Academic Search

Vibrio cholerae is the causative agent of the diarrheal disease cholera. By an incompletely understood developmental process, V. cholerae forms complex surface-associated communities called biofilms. Here we show that quorum sensing-deficient mutants of V. cholerae produce thicker biofilms than those formed by wild-type bacteria. Microarray analysis of biofilm-associated bacteria shows that expression of the Vibrio polysaccharide synthesis (vps) operons is

Jun Zhu; John J. Mekalanos

2003-01-01

139

Simple models for quorum sensing: Nonlinear dynamical analysis  

NASA Astrophysics Data System (ADS)

Quorum sensing refers to the change in the cooperative behavior of a collection of elements in response to the change in their population size or density. This behavior can be observed in chemical and biological systems. These elements or cells are coupled via chemicals in the surrounding environment. Here we focus on the change of dynamical behavior, in particular from quiescent to oscillatory, as the cell population changes. For instance, the silent behavior of the elements can become oscillatory as the system concentration or population increases. In this work, two simple models are constructed that can produce the essential representative properties in quorum sensing. The first is an excitable or oscillatory phase model, which is probably the simplest model one can construct to describe quorum sensing. Using the mean-field approximation, the parameter regime for quorum sensing behavior can be identified, and analytical results for the detailed dynamical properties, including the phase diagrams, are obtained and verified numerically. The second model consists of FitzHugh-Nagumo elements coupled to the signaling chemicals in the environment. Nonlinear dynamical analysis of this mean-field model exhibits rich dynamical behaviors, such as infinite period bifurcation, supercritical Hopf, fold bifurcation, and subcritical Hopf bifurcations as the population parameter changes for different coupling strengths. Analytical result is obtained for the Hopf bifurcation phase boundary. Furthermore, two elements coupled via the environment and their synchronization behavior for these two models are also investigated. For both models, it is found that the onset of oscillations is accompanied by the synchronized dynamics of the two elements. Possible applications and extension of these models are also discussed.

Chiang, Wei-Yin; Li, Yue-Xian; Lai, Pik-Yin

2011-10-01

140

Quorum Sensing and Synchronization in Populations of Coupled Chemical Oscillators  

NASA Astrophysics Data System (ADS)

Experiments and simulations of populations of coupled chemical oscillators, consisting of catalytic particles suspended in solution, provide insights into density-dependent dynamics displayed by many cellular organisms. Gradual synchronization transitions, the "switching on" of activity above a threshold number of oscillators (quorum sensing) and the formation of synchronized groups (clusters) of oscillators have been characterized. Collective behavior is driven by the response of the oscillators to chemicals emitted into the surrounding solution.

Taylor, Annette F.; Tinsley, Mark R.; Showalter, Kenneth

2013-12-01

141

RETRACTED ARTICLE: Quorum-sensing of bacteria and its application  

Microsoft Academic Search

Quorum sensing, or auto induction, as a cell density dependent signaling mechanism in many microorganisms, is triggered via\\u000a auto inducers which passively diffuse across the bacterial envelope and therefore intracellulaly accumulate only at higher\\u000a bacterial densities to regulate specialized processes such as genetic competence, bioluminescence, virulence and sporulation.\\u000a N-acyl homoserine lactones are the most common type of signal molecules. Aquaculture

Guoliang Jiang; Mingxia Su

2009-01-01

142

Transcriptional control of the quorum sensing response in yeastw Arthur Wuster* and M. Madan Babu*  

E-print Network

to synthesise, sense, and respond to the secreted communication molecules. Apart from bacteria, quorum sensing September 2009 DOI: 10.1039/b913579k Quorum sensing is a process of intercellular communication. It allows communication molecules. In the yeast Saccharomyces cerevisiae, the communication molecules are the aromatic

Babu, M. Madan

143

Stereochemical Insignificance Discovered in Acinetobacter baumannii Quorum Sensing  

PubMed Central

Stereochemistry is a key aspect of molecular recognition for biological systems. As such, receptors and enzymes are often highly stereospecific, only recognizing one stereoisomer of a ligand. Recently, the quorum sensing signaling molecules used by the nosocomial opportunistic pathogen, Acinetobacter baumannii, were identified, and the primary signaling molecule isolated from this species was N-(3-hydroxydodecanoyl)-l-homoserine lactone. A plethora of bacterial species have been demonstrated to utilize 3-hydroxy-acylhomoserine lactone autoinducers, and in virtually all cases, the (R)-stereoisomer was identified as the natural ligand and exhibited greater autoinducer activity than the corresponding (S)-stereoisomer. Using chemical synthesis and biochemical assays, we have uncovered a case of stereochemical insignificance in A. baumannii and provide a unique example where stereochemistry appears nonessential for acylhomoserine lactone-mediated quorum sensing signaling. Based on previously reported phylogenetic studies, we suggest that A. baumannii has evolutionarily adopted this unique, yet promiscuous quorum sensing system to ensure its survival, particularly in the presence of other proteobacteria. PMID:22629354

Struss, Anjali Kumari; Watkins, Richard; Feske, Brent D.; Kaufmann, Gunnar F.; Janda, Kim D.

2012-01-01

144

Quorum sensing and biofilms in the pathogen, Streptococcus pneumoniae.  

PubMed

Bacteria are able to colonize and thrive in a variety of different environments as a biofilm, but only within the last half century new insights have been gained in this complex biosystem. Bacterial biofilms play a major role in human health by forming a defensive barrier against antibacterial chemical therapeutics and other potential pathogens, and in infectious disease when the bacteria invade normally sterile compartments. Quorum sensing is the signaling network for cell-to-cell communication and utilized by bacteria to regulate biofilms and other cellular processes. This review will describe recent advances in quorum sensing and biofilms. Initially, it will focus on Streptococcus pneumoniae biofilm regulation and the involvement of the ComABCDE pathway. As part of this review an original analysis of the genotypic and phenotypic variation of the signaling molecule, ComC and its cognate receptor ComD, firstly within the pneumococcal species and then within the genus Streptococcus will be presented. Additionally, a pathway similar to ComABCDE, the BlpABCSRH that regulates bacteriocin and immunity protein production that inhibit the growth of competing bacteria will be described. This review will then examine a third quorum sensing mechanism in the pneumococcus, the LuxS/AI-2, and present a novel gene and protein sequence comparative analysis that indicates its occurrence is more universal across bacterial genera compared with the Com pathway, with more sequence similarities between bacterial genera that are known to colonize the mucosal epithelium. PMID:25189864

Galante, Joana; Ho, Alfred C-Y; Tingey, Sarah; Charalambous, Bambos M

2015-01-01

145

Negative Feedback in the Vibrio harveyi Quorum-Sensing Circuit  

NASA Astrophysics Data System (ADS)

Quorum sensing is the mechanism by which bacteria communicate and synchronize group behaviors. Multiple feedbacks have been identified in the model quorum-sensing bacterium Vibrio harveyi, but it has been unclear how these feedbacks interact in individual cells to control the fidelity of signal transduction. We measured the copy number distribution of the master regulators to quantify the activity of the signaling network. We find that the feedbacks affect the production rate, level, and noise of the core quorum-sensing components. Using fluorescence time-lapse microscopy, we directly observed the master regulator in individual cells, and analyzed the persistence of heterogeneity in terms of the normalized time-delayed direct correlation. Our findings suggest that feedback from small regulatory RNAs regulates a receptor to control the noise level in signal transduction. We further tested this model by re-engineering the gene circuit to specifically diminish this feedback. We conclude that negative feedbacks mediated by sRNAs permit fine-tuning of gene regulation, thereby increasing the fidelity of signal transduction.

Teng, Shu-Wen; Schaffer, Jessie; Wingreen, Ned; Bassler, Bonnie; Phuan Ong, Nai

2010-03-01

146

Possible quorum sensing in the rumen microbial community: detection of quorum-sensing signal molecules from rumen bacteria  

Microsoft Academic Search

The bioluminescence assay using Vibrio harveyi BB170 was used to examine quorum-sensing autoinducer 2 (AI-2) activity from cell-free culture fluids of rumen bacteria. The assay showed that the culture fluids of four species of rumen bacteria, Butyrivibrio fibrisolvens, Eubacterium ruminantium, Ruminococcus flavefaciens, and Succinimonas amylolytica, contained AI-2-like molecules. Furthermore, homologues for luxS genes were detected in rumen fluids collected from

Makoto Mitsumori; Liming Xu; Hiroshi Kajikawa; Mitsunori Kurihara; Kiyoshi Tajima; Jin Hai; Akio Takenaka

2003-01-01

147

Lead Precipitation by Vibrio harveyi: Evidence for Novel Quorum-Sensing Interactions  

PubMed Central

Three pleiotropic, quorum sensing-defective Vibrio harveyi mutants were observed to precipitate soluble Pb2+ as an insoluble compound. The compound was purified and subjected to X-ray diffraction and elemental analyses. These assays identified the precipitated compound as Pb9(PO4)6, an unusual and complex lead phosphate salt that is produced synthetically at temperatures of ca. 200°C. Regulation of the precipitation phenotype was also examined. Introduction of a luxO::kan allele into one of the mutants abolished lead precipitation, indicating that the well-characterized autoinducer 1 (AI1)-AI2 quorum-sensing system can block lead precipitation in dense cell populations. Interestingly, the V. harveyi D1 mutant, a strain defective for secretion of both AI1 and AI2, was shown to be an effective trans inhibitor of lead precipitation. This suggests that a previously undescribed V. harveyi autoinducer, referred to as AI3, can also negatively regulate lead precipitation. Experiments with heterologous bacterial populations demonstrated that many different species are capable of trans regulating the V. harveyi lead precipitation phenotype. Moreover, one of the V. harveyi mutants in this study exhibited little or no response to intercellular signals from other V. harveyi inocula but was quite responsive to some of the heterologous bacteria. Based on these observations, we propose that V. harveyi carries at least one quorum sensor that is specifically dedicated to receiving cross-species communication. PMID:14766565

Mire, Chad E.; Tourjee, Jeanette A.; O'Brien, William F.; Ramanujachary, Kandalam V.; Hecht, Gregory B.

2004-01-01

148

Quorum sensing via static coupling demonstrated by Chua's circuits  

NASA Astrophysics Data System (ADS)

Dynamical quorum sensing, the population based phenomenon, is believed to occur when the elements of a system interact via dynamic coupling. In the present work, we demonstrate an alternate scenario, involving static coupling, that could also lead to quorum sensing behavior. These static and dynamic coupling terms have already been employed by Konishi [Int. J. Bifurcation Chaos Appl. Sci. Eng.IJBEE40218-127410.1142/S0218127407018750 17, 2781 (2007)]. In our context, the coupling is defined as static or dynamic, on the basis of the relative time scales at which the surrounding dynamics and the elements' dynamics evolve. According to this, if the variation in the surrounding dynamics happens on a much larger (fast) time scale than that at which the elements' dynamics are varying (such as seconds and ?s), then the coupling is considered to be static, otherwise it is considered to be dynamic. A series of experiments have been performed starting from a system of three Chua's circuits to a system of 20 Chua's circuits to study two types of quorum transitions: the emergence and the extinction of global oscillations (period-1). The numerics involving up to 100 Chua's circuits validate the experimental observations.

Singh, Harpartap; Parmananda, P.

2013-10-01

149

Inhibition of quorum sensing in Pseudomonas aeruginosa by two herbal essential oils from Apiaceae family.  

PubMed

Ferula (Ferula asafoetida L.) and Dorema (Dorema aucheri Bioss.) both from Apiaceae family were tested for their anti-quorum sensing (QS) activity against Pseudomonas aeruginosa. Both essential oils exhibited anti-QS activity at 25 ?g/ml of concenteration. At this concenteration Ferula fully abolished and Dorema reduced the violacein production by C. violaceum. Pyocyanin, pyoverdine, elastase and biofilm production were decreased in Ferula oil treatments. Dorema oil reduced pyoverdine and elastase production, while pyocyanin and biofilm production were not affacted. Expresion analysis of QS-dependent genes confirmed our phenotypic data. Our data introduced native Dorema and Ferula plants as novel QS and virulence inhibitors. PMID:25564444

Sepahi, Ehsan; Tarighi, Saeed; Ahmadi, Farajollah Shahriari; Bagheri, Abdolreza

2015-02-01

150

The QseBC Quorum Sensing System is Involved in Salmonella enterica serovar Typhimurium Colonization of the Swine Gastrointestinal Tract  

Technology Transfer Automated Retrieval System (TEKTRAN)

The response of bacteria to hormone-like, chemical molecules is termed quorum sensing, a mechanism for cell-to-cell communication that includes sensing the host environment. In the gastrointestinal tract, at least two quorum sensing molecules are present that activate the bacterial QseBC quorum sen...

151

INHIBITION OF QUORUM SENSING IN CLOSTRIDIUM PERFRINGENS AS A MEANS TOWARD FOOD SAFETY  

Technology Transfer Automated Retrieval System (TEKTRAN)

Cell density-dependent signaling through the use of autoinducers, classified as quorum sensing, may play a role in the survival and virulence of Clostridium perfringens in foods. The natural 2-(5H)-furanone, ascorbic acid (vitamin C), was chosen for evaluation as a quorum sensing analogue due to it...

152

How bacteria talk to each other: regulation of gene expression by quorum sensing  

Microsoft Academic Search

Quorum sensing, or the control of gene expression in response to cell density, is used by both Gram-negative and Gram-positive bacteria to regulate a variety of physiological functions. In all cases, quorum sensing involves the production and detection of extracellular signalling molecules called autoinducers. While universal signalling themes exist, variations in the design of the extracellular signals, the signal detection

Bonnie L Bassler

1999-01-01

153

Inhibition of Candida albicans Biofilm Formation by Farnesol, a Quorum-Sensing Molecule  

Microsoft Academic Search

Farnesol is a quorum-sensing molecule that inhibits filamentation in Candida albicans. Both filamentation and quorum sensing are deemed to be important factors in C. albicans biofilm development. Here we examined the effect of farnesol on C. albicans biofilm formation. C. albicans adherent cell populations (after 0, 1, 2, and 4 h of adherence) and preformed biofilms (24 h) were treated

Gordon Ramage; Stephen P. Saville; Brian L. Wickes; J. L. Lopez-Ribot

2002-01-01

154

Extracellular noise-induced stochastic synchronization in heterogeneous quorum sensing network  

Microsoft Academic Search

Quorum sensing is a bacterial mechanism used to synchronize the coordinated response of a microbial population. Because quorum sensing in Gram-negative bacteria depends on release and detection of a diffusible signaling molecule (autoinducer) among a multicellular group, it is considered a simple form of cell–cell communication for the purposes of mathematical analysis. Stochastic equation systems have provided a common approach

Dawei Hong; William M. Saidel; Shushuang Man; Joseph V. Martin

2007-01-01

155

Microbial Communication, Cooperation and Cheating: Quorum Sensing Drives the Evolution of Cooperation in  

E-print Network

Microbial Communication, Cooperation and Cheating: Quorum Sensing Drives the Evolution interactions in which cheating and exploitation are commonplace. Citation: Cza´ra´n T, Hoekstra RF (2009) Microbial Communication, Cooperation and Cheating: Quorum Sensing Drives the Evolution of Cooperation

Czárán, Tamás

156

Structure and Inhibition of Quorum Sensing Target from Streptococcus pneumoniae  

SciTech Connect

Streptococcus pneumoniae 5'-methylthioadenosine/S-adenosylhomocysteine hydrolase (MTAN) catalyzes the hydrolytic deadenylation of its substrates to form adenine and 5-methylthioribose or S-ribosylhomocysteine (SRH). MTAN is not found in mammals but is involved in bacterial quorum sensing. MTAN gene disruption affects the growth and pathogenicity of bacteria, making it a target for antibiotic design. Kinetic isotope effects and computational studies have established a dissociative S{sub N}1 transition state for Escherichia coli MTAN, and transition state analogues resembling the transition state are powerful inhibitors of the enzyme [Singh, V., Lee, J. L., Nunez, S., Howell, P. L., and Schramm, V. L. (2005) Biochemistry 44, 11647-11659]. The sequence of MTAN from S. pneumoniae is 40% identical to that of E. coli MTAN, but S. pneumoniae MTAN exhibits remarkably distinct kinetic and inhibitory properties. 5'-Methylthio-Immucillin-A (MT-ImmA) is a transition state analogue resembling an early S{sub N}1 transition state. It is a weak inhibitor of S. pneumoniae MTAN with a K{sub i} of 1.0 {mu}M. The X-ray structure of S. pneumoniae MTAN with MT-ImmA indicates a dimer with the methylthio group in a flexible hydrophobic pocket. Replacing the methyl group with phenyl (PhT-ImmA), tolyl (p-TolT-ImmA), or ethyl (EtT-ImmA) groups increases the affinity to give K{sub i} values of 335, 60, and 40 nM, respectively. DADMe-Immucillins are geometric and electrostatic mimics of a fully dissociated transition state and bind more tightly than Immucillins. MT-DADMe-Immucillin-A inhibits with a K{sub i} value of 24 nM, and replacing the 5'-methyl group with p-Cl-phenyl (p-Cl-PhT-DADMe-ImmA) gave a K{sub i}* value of 0.36 nM. The inhibitory potential of DADMe-Immucillins relative to the Immucillins supports a fully dissociated transition state structure for S. pneumoniae MTAN. Comparison of active site contacts in the X-ray crystal structures of E. coli and S. pneumoniae MTAN with MT-ImmA would predict equal binding, yet most analogues bind 10{sup 3}-10{sup 4}-fold more tightly to the E. coli enzyme. Catalytic site efficiency is primarily responsible for this difference since k{sub cat}/K{sub m} for S. pneumoniae MTAN is decreased 845-fold relative to that of E. coli MTAN.

Singh,V.; Shi, W.; Almo, S.; Evans, G.; Furneaux, R.; Tyler, P.; Painter, G.; Lenz, D.; Mee, S.; et al.

2006-01-01

157

Bacterial Quorum Sensing: Its Role in Virulence and Possibilities for Its Control  

PubMed Central

Quorum sensing is a process of cell–cell communication that allows bacteria to share information about cell density and adjust gene expression accordingly. This process enables bacteria to express energetically expensive processes as a collective only when the impact of those processes on the environment or on a host will be maximized. Among the many traits controlled by quorum sensing is the expression of virulence factors by pathogenic bacteria. Here we review the quorum-sensing circuits of Staphylococcus aureus, Bacillus cereus, Pseudomonas aeruginosa, and Vibrio cholerae. We outline these canonical quorum-sensing mechanisms and how each uniquely controls virulence factor production. Additionally, we examine recent efforts to inhibit quorum sensing in these pathogens with the goal of designing novel antimicrobial therapeutics. PMID:23125205

Rutherford, Steven T.; Bassler, Bonnie L.

2012-01-01

158

Interaction of a P. aeruginosa Quorum Sensing Signal with Lipid Membranes  

NASA Astrophysics Data System (ADS)

Bacteria use a signaling and regulatory system called "quorum sensing" to alter their gene expressions in response to the concentration of neighboring bacteria and to environmental conditions that make collective activity favorable for bacteria. P. aeruginosa is an opportunistic human pathogen that uses quorum sensing to govern processes such as virulence and biofilm formation. This organism's two main quorum sensing circuits use two different signaling molecules that are amphiphilic and differ primarily in the length of their hydrocarbon side chain and thus in their hydrophobic physical chemistry. How these physical chemistries govern the propagation and spatial localization of signals and thus of quorum sensing is not known. We present preliminary results showing that signals preferentially sequester to amphiphilic lipid membranes, which can act as reservoirs for signal. This is promising for future characterization of how the quorum sensing signals of many bacteria and yeast partition to spatially-differentiated amphiphilic environments, in a host or biofilm.

Morrison, Rebecca; Hall, Amelia; Hutchison, Ellen; Nguyen, Thuc; Cooley, Benjamin; Gordon, Vernita

2011-03-01

159

Monitoring of quorum-sensing molecules during minifermentation studies in wine yeast.  

PubMed

At high cell density or under low nutrient conditions, yeasts collectively adapt their metabolism by secreting aromatic alcohols in what is known as quorum sensing. However, the mechanisms and role of quorum sensing in yeast are poorly understood, and the methodology behind this process is not well established. This paper describes an effective approach to study quorum sensing in yeast fermentations. The separation, detection, and quantification of the putative quorum-sensing molecules 2-phenylethanol, tryptophol, and tyrosol have been optimized on a simple HPLC-based system. With the use of a phenyl HPLC column and a fluorescence detector, the sensitivity of the system was significantly increased. This allowed extraction and concentration procedures to be eliminated and the process to be scaled down to 2 mL minifermentations. Additionally, an innovative method for rapid viable-cell counting is presented. This study forms the basis for detailed studies in kinetics and regulation of quorum sensing in yeast fermentation. PMID:23413824

Zupan, Jure; Avbelj, Martina; Butinar, Bojan; Kosel, Janez; Šergan, Matej; Raspor, Peter

2013-03-13

160

Quorum-Sensing Control of Antibiotic Synthesis in Burkholderia thailandensis?  

PubMed Central

The genome of Burkholderia thailandensis codes for several LuxR-LuxI quorum-sensing systems. We used B. thailandensis quorum-sensing deletion mutants and recombinant Escherichia coli to determine the nature of the signals produced by one of the systems, BtaR2-BtaI2, and to show that this system controls genes required for the synthesis of an antibiotic. BtaI2 is an acyl-homoserine lactone (acyl-HSL) synthase that produces two hydroxylated acyl-HSLs, N-3-hydroxy-decanoyl-HSL (3OHC10-HSL) and N-3-hydroxy-octanoyl-HSL (3OHC8-HSL). The btaI2 gene is positively regulated by BtaR2 in response to either 3OHC10-HSL or 3OHC8-HSL. The btaR2-btaI2 genes are located within clusters of genes with annotations that suggest they are involved in the synthesis of polyketide or peptide antibiotics. Stationary-phase cultures of wild-type B. thailandensis, but not a btaR2 mutant or a strain deficient in acyl-HSL synthesis, produced an antibiotic effective against gram-positive bacteria. Two of the putative antibiotic synthesis gene clusters require BtaR2 and either 3OHC10-HSL or 3OHC8-HSL for activation. This represents another example where antibiotic synthesis is controlled by quorum sensing, and it has implications for the evolutionary divergence of B. thailandensis and its close relatives Burkholderia pseudomallei and Burkholderia mallei. PMID:19376863

Duerkop, Breck A.; Varga, John; Chandler, Josephine R.; Peterson, Snow Brook; Herman, Jake P.; Churchill, Mair E. A.; Parsek, Matthew R.; Nierman, William C.; Greenberg, E. Peter

2009-01-01

161

Quorum Sensing and Expression of Virulence in Pectobacteria  

PubMed Central

Quorum sensing (QS) is a population density-dependent regulatory mechanism in which gene expression is coupled to the accumulation of a chemical signaling molecule. QS systems are widespread among the plant soft-rotting bacteria. In Pectobacterium carotovorum, at least two QS systems exist being specified by the nature of chemical signals involved. QS in Pectobacterium carotovorum uses N-acylhomoserine lactone (AHL) based, as well as autoinducer-2 (AI-2) dependent signaling systems. This review will address the importance of the QS in production of virulence factors and interaction of QS with other regulatory systems in Pectobacterium carotovorum. PMID:22737011

Põllumaa, Lee; Alamäe, Tiina; Mäe, Andres

2012-01-01

162

Small Molecule Inhibitors of AI-2 Signaling in Bacteria: State-of-the-Art and Future Perspectives for Anti-Quorum Sensing Agents  

PubMed Central

Bacteria respond to different small molecules that are produced by other neighboring bacteria. These molecules, called autoinducers, are classified as intraspecies (i.e., molecules produced and perceived by the same bacterial species) or interspecies (molecules that are produced and sensed between different bacterial species). AI-2 has been proposed as an interspecies autoinducer and has been shown to regulate different bacterial physiology as well as affect virulence factor production and biofilm formation in some bacteria, including bacteria of clinical relevance. Several groups have embarked on the development of small molecules that could be used to perturb AI-2 signaling in bacteria, with the ultimate goal that these molecules could be used to inhibit bacterial virulence and biofilm formation. Additionally, these molecules have the potential to be used in synthetic biology applications whereby these small molecules are used as inputs to switch on and off AI-2 receptors. In this review, we highlight the state-of-the-art in the development of small molecules that perturb AI-2 signaling in bacteria and offer our perspective on the future development and applications of these classes of molecules. PMID:23994835

Guo, Min; Gamby, Sonja; Zheng, Yue; Sintim, Herman O.

2013-01-01

163

Small molecule inhibitors of AI-2 signaling in bacteria: state-of-the-art and future perspectives for anti-quorum sensing agents.  

PubMed

Bacteria respond to different small molecules that are produced by other neighboring bacteria. These molecules, called autoinducers, are classified as intraspecies (i.e., molecules produced and perceived by the same bacterial species) or interspecies (molecules that are produced and sensed between different bacterial species). AI-2 has been proposed as an interspecies autoinducer and has been shown to regulate different bacterial physiology as well as affect virulence factor production and biofilm formation in some bacteria, including bacteria of clinical relevance. Several groups have embarked on the development of small molecules that could be used to perturb AI-2 signaling in bacteria, with the ultimate goal that these molecules could be used to inhibit bacterial virulence and biofilm formation. Additionally, these molecules have the potential to be used in synthetic biology applications whereby these small molecules are used as inputs to switch on and off AI-2 receptors. In this review, we highlight the state-of-the-art in the development of small molecules that perturb AI-2 signaling in bacteria and offer our perspective on the future development and applications of these classes of molecules. PMID:23994835

Guo, Min; Gamby, Sonja; Zheng, Yue; Sintim, Herman O

2013-01-01

164

Quorum Sensing Controls Exopolysaccharide Production in Sinorhizobium meliloti  

PubMed Central

Sinorhizobium meliloti is a soil bacterium capable of invading and establishing a symbiotic relationship with alfalfa plants. This invasion process requires the synthesis, by S. meliloti, of at least one of the two symbiotically important exopolysaccharides, succinoglycan and EPS II. We have previously shown that the sinRI locus of S. meliloti encodes a quorum-sensing system that plays a role in the symbiotic process. Here we show that the sinRI locus exerts one level of control through regulation of EPS II synthesis. Disruption of the autoinducer synthase gene, sinI, abolished EPS II production as well as the expression of several genes in the exp operon that are responsible for EPS II synthesis. This phenotype was complemented by the addition of acyl homoserine lactone (AHL) extracts from the wild-type strain but not from a sinI mutant, indicating that the sinRI-specified AHLs are required for exp gene expression. This was further confirmed by the observation that synthetic palmitoleyl homoserine lactone (C16:1-HL), one of the previously identified sinRI-specified AHLs, specifically restored exp gene expression. Most importantly, the absence of symbiotically active EPS II in a sinI mutant was confirmed in plant nodulation assays, emphasizing the role of quorum sensing in symbiosis. PMID:12486070

Marketon, Melanie M.; Glenn, Sarah A.; Eberhard, Anatol; González, Juan E.

2003-01-01

165

Chemical methods to interrogate bacterial quorum sensing pathways  

PubMed Central

Bacteria frequently manifest distinct phenotypes as a function of cell density in a phenomenon known as quorum sensing (QS). This intercellular signalling process is mediated by “chemical languages comprised of low-molecular weight signals, known as” autoinducers, and their cognate receptor proteins. As many of the phenotypes regulated by QS can have a significant impact on the success of pathogenic or mutualistic prokaryotic–eukaryotic interactions, there is considerable interest in methods to probe and modulate QS pathways with temporal and spatial control. Such methods would be valuable for both basic research in bacterial ecology and in practical medicinal, agricultural, and industrial applications. Toward this goal, considerable recent research has been focused on the development of chemical approaches to study bacterial QS pathways. In this Perspective, we provide an overview of the use of chemical probes and techniques in QS research. Specifically, we focus on: (1) combinatorial approaches for the discovery of small molecule QS modulators, (2) affinity chromatography for the isolation of QS receptors, (3) reactive and fluorescent probes for QS receptors, (4) antibodies as quorum “quenchers,” (5) abiotic polymeric “sinks” and “pools” for QS signals, and (6) the electrochemical sensing of QS signals. The application of such chemical methods can offer unique advantages for both elucidating and manipulating QS pathways in culture and under native conditions. PMID:22948815

Praneenararat, Thanit; Palmer, Andrew G.

2012-01-01

166

A quorum sensing-disrupting brominated thiophenone with a promising therapeutic potential to treat luminescent vibriosis.  

PubMed

Vibrio harveyi is amongst the most important bacterial pathogens in aquaculture. Novel methods to control this pathogen are needed since many strains have acquired resistance to antibiotics. We previously showed that quorum sensing-disrupting furanones are able to protect brine shrimp larvae against vibriosis. However, a major problem of these compounds is that they are toxic toward higher organisms and therefore, they are not safe to be used in aquaculture. The synthesis of brominated thiophenones, sulphur analogues of the quorum sensing-disrupting furanones, has recently been reported. In the present study, we report that these compounds block quorum sensing in V. harveyi at concentrations in the low micromolar range. Bioluminescence experiments with V. harveyi quorum sensing mutants and a fluorescence anisotropy assay indicated that the compounds disrupt quorum sensing in this bacterium by decreasing the ability of the quorum sensing master regulator LuxR to bind to its target promoter DNA. In vivo challenge tests with gnotobiotic brine shrimp larvae showed that thiophenone compound TF310, (Z)-4-((5-(bromomethylene)-2-oxo-2,5-dihydrothiophen-3-yl)methoxy)-4-oxobutanoic acid, completely protected the larvae from V. harveyi BB120 when dosed to the culture water at 2.5 µM or more, whereas severe toxicity was only observed at 250 µM. This makes TF310 showing the highest therapeutic index of all quorum sensing-disrupting compounds tested thus far in our brine shrimp model system. PMID:22848604

Defoirdt, Tom; Benneche, Tore; Brackman, Gilles; Coenye, Tom; Sorgeloos, Patrick; Scheie, Anne Aamdal

2012-01-01

167

Non-native acylated homoserine lactones reveal that LuxIR quorum sensing promotes symbiont stability.  

PubMed

Quorum sensing, a group behaviour coordinated by a diffusible pheromone signal and a cognate receptor, is typical of bacteria that form symbioses with plants and animals. LuxIR-type N-acyl L-homoserine (AHL) quorum sensing is common in Gram-negative Proteobacteria, and many members of this group have additional quorum-sensing networks. The bioluminescent symbiont Vibrio fischeri encodes two AHL signal synthases: AinS and LuxI. AinS-dependent quorum sensing converges with LuxI-dependent quorum sensing at the LuxR regulatory element. Both AinS- and LuxI-mediated signalling are required for efficient and persistent colonization of the squid host, Euprymna scolopes. The basis of the mutualism is symbiont bioluminescence, which is regulated by both LuxI- and AinS-dependent quorum sensing, and is essential for maintaining a colonization of the host. Here, we used chemical and genetic approaches to probe the dynamics of LuxI- and AinS-mediated regulation of bioluminescence during symbiosis. We demonstrate that both native AHLs and non-native AHL analogues can be used to non-invasively and specifically modulate induction of symbiotic bioluminescence via LuxI-dependent quorum sensing. Our data suggest that the first day of colonization, during which symbiont bioluminescence is induced by LuxIR, is a critical period that determines the stability of the V.?fischeri population once symbiosis is established. PMID:24191970

Studer, Sarah V; Schwartzman, Julia A; Ho, Jessica S; Geske, Grant D; Blackwell, Helen E; Ruby, Edward G

2014-08-01

168

Quorum sensing activity of Enterobacter asburiae isolated from lettuce leaves.  

PubMed

Bacterial communication or quorum sensing (QS) is achieved via sensing of QS signaling molecules consisting of oligopeptides in Gram-positive bacteria and N-acyl homoserine lactones (AHL) in most Gram-negative bacteria. In this study, Enterobacteriaceae isolates from Batavia lettuce were screened for AHL production. Enterobacter asburiae, identified by matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS) was found to produce short chain AHLs. High resolution triple quadrupole liquid chromatography mass spectrometry (LC/MS) analysis of the E. asburiae spent supernatant confirmed the production of N-butanoyl homoserine lactone (C4-HSL) and N-hexanoyl homoserine lactone (C6-HSL). To the best of our knowledge, this is the first report of AHL production by E. asburiae. PMID:24152877

Lau, Yin Yin; Sulaiman, Joanita; Chen, Jian Woon; Yin, Wai-Fong; Chan, Kok-Gan

2013-01-01

169

Monitoring of Vibrio harveyi quorum sensing activity in real time during infection of brine shrimp larvae.  

PubMed

Quorum sensing, bacterial cell-to-cell communication, has been linked to the virulence of pathogenic bacteria. Indeed, in vitro experiments have shown that many bacterial pathogens regulate the expression of virulence genes by this cell-to-cell communication process. Moreover, signal molecules have been detected in samples retrieved from infected hosts and quorum sensing disruption has been reported to result in reduced virulence in different host-pathogen systems. However, data on in vivo quorum sensing activity of pathogens during infection of a host are currently lacking. We previously reported that quorum sensing regulates the virulence of Vibrio harveyi in a standardised model system with gnotobiotic brine shrimp (Artemia franciscana) larvae. Here, we monitored quorum sensing activity in Vibrio harveyi during infection of the shrimp, using bioluminescence as a read-out. We found that wild-type Vibrio harveyi shows a strong increase in quorum sensing activity early during infection. In this respect, the bacteria behave remarkably similar in different larvae, despite the fact that only half of them survive the infection. Interestingly, when expressed per bacterial cell, Vibrio harveyi showed around 200-fold higher maximal quorum sensing-regulated bioluminescence when associated with larvae than in the culture water. Finally, the in vivo quorum sensing activity of mutants defective in the production of one of the three signal molecules is consistent with their virulence, with no detectable in vivo quorum sensing activity in AI-2- and CAI-1-deficient mutants. These results indicate that AI-2 and CAI-1 are the dominant signals during infection of brine shrimp. PMID:22673627

Defoirdt, Tom; Sorgeloos, Patrick

2012-12-01

170

Quenching quorum-sensing-dependent bacterial infection by an N-acyl homoserine lactonase  

Microsoft Academic Search

Bacterial cells sense their population density through a sophisticated cell-cell communication system and trigger expression of particular genes when the density reaches a threshold. This type of gene regulation, which controls diverse biological functions including virulence, is known as quorum sensing. Quorum-sensing signals, such as acyl-homoserine lactones (AHLs), are the essential components of the communication system. AHLs regulate virulence gene

Yi-Hu Dong; Lian-Hui Wang; Jin-Ling Xu; Hai-Bao Zhang; Xi-Fen Zhang; Lian-Hui Zhang

2001-01-01

171

Quorum sensing control of phosphorus acquisition in Trichodesmium consortia.  

PubMed

Colonies of the cyanobacterium Trichodesmium are abundant in the oligotrophic ocean, and through their ability to fix both CO(2) and N(2), have pivotal roles in the cycling of carbon and nitrogen in these highly nutrient-depleted environments. Trichodesmium colonies host complex consortia of epibiotic heterotrophic bacteria, and yet, the regulation of nutrient acquisition by these epibionts is poorly understood. We present evidence that epibiotic bacteria in Trichodesmium consortia use quorum sensing (QS) to regulate the activity of alkaline phosphatases (APases), enzymes used by epibionts in the acquisition of phosphate from dissolved-organic phosphorus molecules. A class of QS molecules, acylated homoserine lactones (AHLs), were produced by cultivated epibionts, and adding these AHLs to wild Trichodesmium colonies collected at sea led to a consistent doubling of APase activity. By contrast, amendments of (S)-4,5-dihydroxy-2,3-pentanedione (DPD)-the precursor to the autoinducer-2 (AI-2) family of universal interspecies signaling molecules-led to the attenuation of APase activity. In addition, colonies collected at sea were found by high performance liquid chromatography/mass spectrometry to contain both AHLs and AI-2. Both types of molecules turned over rapidly, an observation we ascribe to quorum quenching. Our results reveal a complex chemical interplay among epibionts using AHLs and AI-2 to control access to phosphate in dissolved-organic phosphorus. PMID:21900966

Van Mooy, Benjamin A S; Hmelo, Laura R; Sofen, Laura E; Campagna, Shawn R; May, Amanda L; Dyhrman, Sonya T; Heithoff, Abigail; Webb, Eric A; Momper, Lily; Mincer, Tracy J

2012-02-01

172

Novel quorum-sensing peptides mediating interspecies bacterial cell death.  

PubMed

ABSTRACT Escherichia coli mazEF is a toxin-antitoxin stress-induced module mediating cell death. It requires the quorum-sensing signal (QS) "extracellular death factor" (EDF), the penta-peptide NNWNN (EcEDF), enhancing the endoribonucleolytic activity of E. coli toxin MazF. Here we discovered that E. coli mazEF-mediated cell death could be triggered by QS peptides from the supernatants (SN) of the Gram-positive bacterium Bacillus subtilis and the Gram-negative bacterium Pseudomonas aeruginosa. In the SN of B. subtilis, we found one EDF, the hexapeptide RGQQNE, called BsEDF. In the SN of P. aeruginosa, we found three EDFs: the nonapeptide INEQTVVTK, called PaEDF-1, and two hexadecapeptides, VEVSDDGSGGNTSLSQ, called PaEDF-2, and APKLSDGAAAGYVTKA, called PaEDF-3. When added to a diluted E. coli cultures, each of these peptides acted as an interspecies EDF that triggered mazEF-mediated death. Furthermore, though their sequences are very different, each of these EDFs amplified the endoribonucleolytic activity of E. coli MazF, probably by interacting with different sites on E. coli MazF. Finally, we suggest that EDFs may become the basis for a new class of antibiotics that trigger death from outside the bacterial cells. IMPORTANCE Bacteria communicate with one another via quorum-sensing signal (QS) molecules. QS provides a mechanism for bacteria to monitor each other's presence and to modulate gene expression in response to population density. Previously, we added E. coli EDF (EcEDF), the peptide NNWNN, to this list of QS molecules. Here we extended the group of QS peptides to several additional different peptides. The new EDFs are produced by two other bacteria, Bacillus subtilis and Pseudomonas aeruginosa. Thus, in this study we established a "new family of EDFs." This family provides the first example of quorum-sensing molecules participating in interspecies bacterial cell death. Furthermore, each of these peptides provides the basis of a new class of antibiotics triggering death by acting from outside the cell. PMID:23736285

Kumar, Sathish; Kolodkin-Gal, Ilana; Engelberg-Kulka, Hanna

2013-01-01

173

Bacteria clustering by polymers induces the expression of quorum-sensing-controlled phenotypes  

NASA Astrophysics Data System (ADS)

Bacteria deploy a range of chemistries to regulate their behaviour and respond to their environment. Quorum sensing is one method by which bacteria use chemical reactions to modulate pre-infection behaviour such as surface attachment. Polymers that can interfere with bacterial adhesion or the chemical reactions used for quorum sensing are therefore a potential means to control bacterial population responses. Here, we report how polymeric ‘bacteria sequestrants’, designed to bind to bacteria through electrostatic interactions and therefore inhibit bacterial adhesion to surfaces, induce the expression of quorum-sensing-controlled phenotypes as a consequence of cell clustering. A combination of polymer and analytical chemistry, biological assays and computational modelling has been used to characterize the feedback between bacteria clustering and quorum sensing signalling. We have also derived design principles and chemical strategies for controlling bacterial behaviour at the population level.

Lui, Leong T.; Xue, Xuan; Sui, Cheng; Brown, Alan; Pritchard, David I.; Halliday, Nigel; Winzer, Klaus; Howdle, Steven M.; Fernandez-Trillo, Francisco; Krasnogor, Natalio; Alexander, Cameron

2013-12-01

174

Analysis of Quorum-Sensing Pantoea stewartii Strain M073A through Whole-Genome Sequencing  

PubMed Central

Pantoea stewartii strain M073a is a Gram-negative bacterium isolated from a tropical waterfall. This strain exhibits quorum-sensing activity. Here, the assembly and annotation of its genome are presented.

Izzati Mohamad, Nur; Tan, Wen-Si; Chang, Chien-Yi; Keng Tee, Kok; Yin, Wai-Fong

2015-01-01

175

The Apparent Quorum-Sensing Inhibitory Activity of Pyrogallol Is a Side Effect of Peroxide Production  

PubMed Central

There currently is more and more interest in the use of natural products, such as tea polyphenols, as therapeutic agents. The polyphenol compound pyrogallol has been reported before to inhibit quorum-sensing-regulated bioluminescence in Vibrio harveyi. Here, we report that the addition of 10 mg · liter?1 pyrogallol protects both brine shrimp (Artemia franciscana) and giant river prawn (Macrobrachium rosenbergii) larvae from pathogenic Vibrio harveyi, whereas the compound showed relatively low toxicity (therapeutic index of 10). We further demonstrate that the apparent quorum-sensing-disrupting activity is a side effect of the peroxide-producing activity of this compound rather than true quorum-sensing inhibition. Our results emphasize that verification of minor toxic effects by using sensitive methods and the use of appropriate controls are essential when characterizing compounds as being able to disrupt quorum sensing. PMID:23545532

Pande, Gde Sasmita Julyantoro; Baruah, Kartik; Bossier, Peter

2013-01-01

176

The apparent quorum-sensing inhibitory activity of pyrogallol is a side effect of peroxide production.  

PubMed

There currently is more and more interest in the use of natural products, such as tea polyphenols, as therapeutic agents. The polyphenol compound pyrogallol has been reported before to inhibit quorum-sensing-regulated bioluminescence in Vibrio harveyi. Here, we report that the addition of 10 mg · liter(-1) pyrogallol protects both brine shrimp (Artemia franciscana) and giant river prawn (Macrobrachium rosenbergii) larvae from pathogenic Vibrio harveyi, whereas the compound showed relatively low toxicity (therapeutic index of 10). We further demonstrate that the apparent quorum-sensing-disrupting activity is a side effect of the peroxide-producing activity of this compound rather than true quorum-sensing inhibition. Our results emphasize that verification of minor toxic effects by using sensitive methods and the use of appropriate controls are essential when characterizing compounds as being able to disrupt quorum sensing. PMID:23545532

Defoirdt, Tom; Pande, Gde Sasmita Julyantoro; Baruah, Kartik; Bossier, Peter

2013-06-01

177

Acyl-homoserine lactone quorum sensing in the Roseobacter clade.  

PubMed

Members of the Roseobacter clade are ecologically important and numerically abundant in coastal environments and can associate with marine invertebrates and nutrient-rich marine snow or organic particles, on which quorum sensing (QS) may play an important role. In this review, we summarize current research progress on roseobacterial acyl-homoserine lactone-based QS, particularly focusing on three relatively well-studied representatives, Phaeobacter inhibens DSM17395, the marine sponge symbiont Ruegeria sp. KLH11 and the dinoflagellate symbiont Dinoroseobacter shibae. Bioinformatic survey of luxI homologues revealed that over 80% of available roseobacterial genomes encode at least one luxI homologue, reflecting the significance of QS controlled regulatory pathways in adapting to the relevant marine environments. We also discuss several areas that warrant further investigation, including studies on the ecological role of these diverse QS pathways in natural environments. PMID:24402124

Zan, Jindong; Liu, Yue; Fuqua, Clay; Hill, Russell T

2014-01-01

178

Studying bacterial quorum-sensing at the single cell level  

NASA Astrophysics Data System (ADS)

Like many bacterial species, Vibrio fischeri can detect its own population density through a quorum sensing (QS) mechanism. The bacterium releases a signal molecule (AI, autoinducer), which accumulates at high population density and triggers a genetic switch. In V.fischeri this leads to bioluminescence. Little is known about how stochastic gene expression affects QS at the level of single cells. We are imaging the luminescence of individual V.fischeri cells in a flow chamber and directly measuring the intercell variability in AI activation of the QS circuit. Our single-cell luminescence experiments allow us to track cells over time and characterize variations in their response to AI levels. We find heterogeneous response to the external signal: at a given AI concentration some cells may be strongly luminescent while others are virtually dark. The analysis of noise in the individual cell response can eventually lead to a better understanding of how cells use QS to gather information about their environment.

Delfino Perez, Pablo; Pelakh, Leslie; Young, Jonathan; Johnson, Elaine; Hagen, Stephen

2010-03-01

179

Crowd Synchrony and Quorum Sensing in Delay-Coupled Lasers  

NASA Astrophysics Data System (ADS)

Crowd synchrony and quorum sensing arise when a large number of dynamical elements communicate with each other via a common information pool. Previous evidence has shown that this type of coupling leads to synchronization, when coupling is instantaneous and the number of coupled elements is large enough. Here we consider a situation in which the transmission of information between the system components and the coupling pool is not instantaneous. To that end, we model a system of semiconductor lasers optically coupled to a central laser with a delay. Our results show that, even though the lasers are nonidentical due to their distinct optical frequencies, zero-lag synchronization arises. By changing a system parameter, we can switch between two different types of synchronization transition. The dependence of the transition with respect to the delay-coupling parameters is studied.

Zamora-Munt, Jordi; Masoller, C.; Garcia-Ojalvo, Jordi; Roy, Rajarshi

2010-12-01

180

Crowd synchrony and quorum sensing in delay-coupled lasers  

E-print Network

Crowd synchrony and quorum sensing arise when a large number of dynamical elements communicate with each other via a common information pool. Previous evidence in different fields, including chemistry, biology and civil engineering, has shown that this type of coupling leads to synchronization, when coupling is instantaneous and the number of coupled elements is large enough. Here we consider a situation in which the transmission of information between the system components and the coupling pool is not instantaneous. To that end, we model a system of semiconductor lasers optically coupled to a central laser with a delay. Our results show that, even though the lasers are non-identical due to their distinct optical frequencies, zero-lag synchronization arises. By changing a system parameter, we can switch between two different types of synchronization transition. The dependence of the transition with respect to the delay-coupling parameters is studied.

Zamora-Munt, Jordi; Garcia-Ojalvo, Jordi; Roy, Rajarshi

2010-01-01

181

Synchronization and quorum sensing in a swarm of humanoid robots  

E-print Network

With the advent of inexpensive simple humanoid robots, new classes of robotic questions can be considered experimentally. One of these is collective behavior of groups of humanoid robots, and in particular robot synchronization and swarming. The goal of this work is to robustly synchronize a group of humanoid robots, and to demonstrate the approach experimentally on a choreography of 8 robots. We aim to be robust to network latencies, and to allow robots to join or leave the group at any time (for example a fallen robot should be able to stand up to rejoin the choreography). Contraction theory is used to allow each robot in the group to synchronize to a common virtual oscillator, and quorum sensing strategies are exploited to fit within the available bandwidth. The humanoids used are Nao's, developed by Aldebaran Robotics.

Bechon, Patrick

2012-01-01

182

Parallel Quorum Sensing Systems Converge to Regulate Virulence in Vibrio cholerae  

Microsoft Academic Search

The marine bacterium Vibrio harveyi possesses two quorum sensing systems (System 1 and System 2) that regulate bioluminescence. Although the Vibrio cholerae genome sequence reveals that a V. harveyi-like System 2 exists, it does not predict the existence of a V. harveyi-like System 1 or any obvious quorum sensing-controlled target genes. In this report we identify and characterize the genes

Melissa B. Miller; Karen Skorupski; Derrick H. Lenz; Ronald K. Taylor; Bonnie L. Bassler

2002-01-01

183

Inhibition of quorum sensing in Pseudomonas aeruginosa biofilm bacteria by a halogenated furanone compound  

Microsoft Academic Search

Novel molecular tools have been constructed which allow for in situ detection of N-acyl homoserine lactone (AHL)-mediated quorum sensing in Pseudomonas aeruginosa biofilms. The reporter responds to AHL activation of LasR by expression of an unstable version of the green-fluorescent protein (Gfp). Gfp- based reporter technology has been applied for non-destructive, single-cell- level detection of quorum sensing in laboratory-based P.

Morten Hentzer; Kathrin Riedel; Thomas B. Rasmussen; Arne Heydorn; Jens Bo Andersen; Matthew R. Parsek; Scott A. Rice; Leo Eberl; Søren Molin; Niels Høiby; Staffan Kjelleberg; Michael Givskov

2002-01-01

184

The RNPP family of quorum-sensing proteins in Gram-positive bacteria  

Microsoft Academic Search

Quorum sensing is one of several mechanisms that bacterial cells use to interact with each other and coordinate certain physiological\\u000a processes in response to cell density. This mechanism is mediated by extracellular signaling molecules; once a critical threshold\\u000a concentration has been reached, a target sensor kinase or response regulator is activated (or repressed), facilitating the\\u000a expression of quorum sensing-dependent genes.

Jorge Rocha-Estrada; Angel E. Aceves-Diez; Gabriel Guarneros; Mayra de la Torre

2010-01-01

185

L-Canavanine Made by Medicago sativa Interferes with Quorum Sensing in Sinorhizobium meliloti  

Microsoft Academic Search

Sinorhizobium meliloti is a gram-negative soil bacterium, capable of establishing a nitrogen-fixing symbiosis with its legume host, alfalfa (Medicago sativa). Quorum sensing plays a crucial role in this symbiosis, where it influences the nodulation process and the synthesis of the symbiotically important exopolysaccharide II (EPS II). S. meliloti has three quorum-sensing systems (Sin, Tra, and Mel) that use N-acyl homoserine

Neela D. Keshavan; Puneet K. Chowdhary; Donovan C. Haines; Juan E. Gonzalez

2005-01-01

186

Contribution of quorum-sensing systems to virulence of Pseudomonas aeruginosa in an experimental pyelonephritis model  

Microsoft Academic Search

Background and Purpose: Pseudomonas aeruginosa has been reported to monitor its cell density as well as expression of virulence determinants by quorum-sensing signal mechanisms operative through autoinducers. In the present investigation, we studied the contribution of quorum-sensing signals during the course of P. aeruginosa- induced pyelonephritis in mice. Methods: The standard parent strain of P. aeruginosa (PAO1), possessing functional las

Rahul Mittal; Saroj Sharma; Sanjay Chhibber; Kusum Harjai

2006-01-01

187

The dependence of quorum sensing on the depth of a growing biofilm  

Microsoft Academic Search

In a process called quorum sensing, bacteria monitor their population density via extracellular signaling molecules and modulate\\u000a gene expression accordingly. In this paper, a one-dimensional model of a growing Pseudomonas aeruginosa biofilm is examined. Quorum sensing has been included in the model through equations describing the production, degradation,\\u000a and diffusion of the signaling molecules, acyl-homoserine lactones, in the biofilm. From

D. L. Chopp; M. J. Kirisits; B. Moran; M. R. Parsek

2003-01-01

188

Three Parallel Quorum-Sensing Systems Regulate Gene Expression in Vibrio harveyi  

Microsoft Academic Search

In a process called quorum sensing, bacteria communicate using extracellular signal molecules termed auto- inducers. Two parallel quorum-sensing systems have been identified in the marine bacterium Vibrio harveyi. System 1 consists of the LuxM-dependent autoinducer HAI-1 and the HAI-1 sensor, LuxN. System 2 consists of the LuxS-dependent autoinducer AI-2 and the AI-2 detector, LuxPQ. The related bacterium, Vibrio cholerae, a

Jennifer M. Henke; Bonnie L. Bassler

2004-01-01

189

Societal interactions in ovarian cancer metastasis: a quorum-sensing hypothesis  

Microsoft Academic Search

The biochemical and biological mechanisms metastatic cancer cells use to function as communities and thwart internal and external\\u000a growth control mechanisms remain undefined. In this work, we present the hypothesis that cancer cells may use a Quorum-Sensing mechanism to regulate multicellular functions and control steps in metastatic colonization. Quorum sensing is a bacterial\\u000a cell-cell communication process used to track increasing

Jonathan Hickson; S. Diane Yamada; Jonathan Berger; John Alverdy; James O’Keefe; Bonnie Bassler; Carrie Rinker-Schaeffer

2009-01-01

190

Quorum sensing by peptide pheromones and two component signal transduction systems in Gram-positive bacteria  

Microsoft Academic Search

Cell-density-dependent gene expression appears to be widely spread in bacteria. This quorum-sensing phenomenon has been well established in Gram-negative bacteria, where N-acyl homoserine lactones are the diffusible communication molecules that modulate cell-density-dependent phenotypes. Similarly, a variety of processes are known to be regulated in a cell-density- or growth-phase-dependent manner in Gram-positive bacteria. Examples of such quorum-sensing modes in Gram-positive bacteria

Michiel Kleerebezem; Luis E. N. Quadri; Oscar P. Kuipers; Willem M. de Vos

1997-01-01

191

Making sense of quorum sensing in lactobacilli: a special focus on Lactobacillus plantarum WCFS1  

Microsoft Academic Search

In silico identification criteria were defined to predict if genes encoding histidine protein kinases (HPKs) and response regulators (RRs) could be part of peptide-based quorum sensing (QS) two-component regulatory systems (QS-TCSs) in Firmicutes. These criteria were used to screen HPKs and RRs annotated on the completed genome sequences of Lactobacillus species, and several (putative) QS-TCSs were identified in this way.

M. H. J. Sturme; C. Francke; R. J. Siezen; W. M. de Vos; M. Kleerebezem

2007-01-01

192

DNA Microarray-Based Identification of Genes Controlled by Autoinducer 2Stimulated Quorum Sensing in Escherichia coli  

Microsoft Academic Search

Bacterial cell-to-cell communication facilitates coordinated expression of specific genes in a growth rate-II and cell density-dependent manner, a process known as quorum sensing. While the discovery of a diffusible Escherichia coli signaling pheromone, termed autoinducer 2 (AI-2), has been made along with several quorum sensing genes, the overall number and coordination of genes controlled by quorum sensing through the AI-2

MATTHEW P. DELISA; CHI-FANG WU; LIANG WANG; JAMES J. VALDES; WILLIAM E. BENTLEY

2001-01-01

193

Quorum Sensing in Escherichia coli, Salmonella typhimurium, and Vibrio harveyi: A New Family of Genes Responsible for Autoinducer Production  

Microsoft Academic Search

In bacteria, the regulation of gene expression in response to changes in cell density is called quorum sensing. Quorum-sensing bacteria produce, release, and respond to hormone-like molecules (autoinducers) that accumulate in the external environment as the cell population grows. In the marine bacterium Vibrio harveyi two parallel quorum-sensing systems exist, and each is composed of a sensor-autoinducer pair. V. harveyi

Michael G. Surette; Melissa B. Miller; Bonnie L. Bassler

1999-01-01

194

Quorum Sensing Regulatory Cascades Control Vibrio fluvialis Pathogenesis  

PubMed Central

Quorum sensing (QS) is a process by which individual bacteria are able to communicate with one another, thereby enabling the population as a whole to coordinate gene regulation and subsequent phenotypic outcomes. Communication is accomplished through production and detection of small molecules in the extracellular milieu. In many bacteria, particularly Vibrio species, multiple QS systems result in multiple signals, as well as cross talk between systems. In this study, we identify two QS systems in the halophilic enteric pathogen Vibrio fluvialis: one acyl-homoserine lactone (AHL) based and one CAI-1/AI-2 based. We show that a LuxI homolog, VfqI, primarily produces 3-oxo-C10-HSL, which is sensed by a LuxR homolog, VfqR. VfqR-AHL is required to activate vfqI expression and autorepress vfqR expression. In addition, we have shown that similar to that in V. cholerae and V. harveyi, V. fluvialis produces CAI-1 and AI-2 signal molecules to activate the expression of a V. cholerae HapR homolog through LuxO. Although VfqR-AHL does not regulate hapR expression, HapR can repress vfqR transcription. Furthermore, we found that QS in V. fluvialis positively regulates production of two potential virulence factors, an extracellular protease and hemolysin. QS also affects cytotoxic activity against epithelial tissue cultures. These data suggest that V. fluvialis integrates QS regulatory pathways to play important physiological roles in pathogenesis. PMID:23749976

Wang, Yunduan; Wang, Hui; Liang, Weili; Hay, Amanda J.; Zhong, Zengtao

2013-01-01

195

Cooperation, quorum sensing, and evolution of virulence in Staphylococcus aureus.  

PubMed

The virulence and fitness in vivo of the major human pathogen Staphylococcus aureus are associated with a cell-to-cell signaling mechanism known as quorum sensing (QS). QS coordinates the production of virulence factors via the production and sensing of autoinducing peptide (AIP) signal molecules by the agr locus. Here we show, in a wax moth larva virulence model, that (i) QS in S. aureus is a cooperative social trait that provides a benefit to the local population of cells, (ii) agr mutants, which do not produce or respond to QS signal, are able to exploit the benefits provided by the QS of others ("cheat"), allowing them to increase in frequency when in mixed populations with cooperators, (iii) these social interactions between cells determine virulence, with the host mortality rate being negatively correlated to the percentage of agr mutants ("cheats") in a population, and (iv) a higher within-host relatedness (lower strain diversity) selects for QS and hence higher virulence. Our results provide an explanation for why agr mutants show reduced virulence in animal models but can be isolated from infections of humans. More generally, by providing the first evidence that QS is a cooperative social behavior in a Gram-positive bacterium, our results suggest convergent, and potentially widespread, evolution for signaling to coordinate cooperation in bacteria. PMID:24343650

Pollitt, Eric J G; West, Stuart A; Crusz, Shanika A; Burton-Chellew, Maxwell N; Diggle, Stephen P

2014-03-01

196

Novel Quorum-Sensing Peptides Mediating Interspecies Bacterial Cell Death  

PubMed Central

ABSTRACT Escherichia coli mazEF is a toxin-antitoxin stress-induced module mediating cell death. It requires the quorum-sensing signal (QS) “extracellular death factor” (EDF), the penta-peptide NNWNN (EcEDF), enhancing the endoribonucleolytic activity of E. coli toxin MazF. Here we discovered that E. coli mazEF-mediated cell death could be triggered by QS peptides from the supernatants (SN) of the Gram-positive bacterium Bacillus subtilis and the Gram-negative bacterium Pseudomonas aeruginosa. In the SN of B. subtilis, we found one EDF, the hexapeptide RGQQNE, called BsEDF. In the SN of P. aeruginosa, we found three EDFs: the nonapeptide INEQTVVTK, called PaEDF-1, and two hexadecapeptides, VEVSDDGSGGNTSLSQ, called PaEDF-2, and APKLSDGAAAGYVTKA, called PaEDF-3. When added to a diluted E. coli cultures, each of these peptides acted as an interspecies EDF that triggered mazEF-mediated death. Furthermore, though their sequences are very different, each of these EDFs amplified the endoribonucleolytic activity of E. coli MazF, probably by interacting with different sites on E. coli MazF. Finally, we suggest that EDFs may become the basis for a new class of antibiotics that trigger death from outside the bacterial cells. PMID:23736285

Kumar, Sathish; Kolodkin-Gal, Ilana; Engelberg-Kulka, Hanna

2013-01-01

197

Quorum Sensing in Some Representative Species of Halomonadaceae  

PubMed Central

Cell-to-cell communication, or quorum-sensing (QS), systems are employed by bacteria for promoting collective behaviour within a population. An analysis to detect QS signal molecules in 43 species of the Halomonadaceae family revealed that they produced N-acyl homoserine lactones (AHLs), which suggests that the QS system is widespread throughout this group of bacteria. Thin-layer chromatography (TLC) analysis of crude AHL extracts, using Agrobacterium tumefaciens NTL4 (pZLR4) as biosensor strain, resulted in different profiles, which were not related to the various habitats of the species in question. To confirm AHL production in the Halomonadaceae species, PCR and DNA sequencing approaches were used to study the distribution of the luxI-type synthase gene. Phylogenetic analysis using sequence data revealed that 29 of the species studied contained a LuxI homolog. Phylogenetic analysis showed that sequences from Halomonadaceae species grouped together and were distinct from other members of the Gammaproteobacteria and also from species belonging to the Alphaproteobacteria and Betaproteobacteria. PMID:25371343

Tahrioui, Ali; Schwab, Melanie; Quesada, Emilia; Llamas, Inmaculada

2013-01-01

198

Bacterial quorum sensing and nitrogen cycling in rhizosphere soil  

SciTech Connect

Plant photosynthate fuels carbon-limited microbial growth and activity, resulting in increased rhizosphere nitrogen (N)-mineralization. Most soil organic N is macromolecular (chitin, protein, nucleotides); enzymatic depolymerization is likely rate-limiting for plant N accumulation. Analyzing Avena (wild oat) planted in microcosms containing sieved field soil, we observed increased rhizosphere chitinase and protease specific activities, bacterial cell densities, and dissolved organic nitrogen (DON) compared to bulk soil. Low-molecular weight DON (<3000 Da) was undetectable in bulk soil but comprised 15% of rhizosphere DON. Extracellular enzyme production in many bacteria requires quorum sensing (QS), cell-density dependent group behavior. Because proteobacteria are considered major rhizosphere colonizers, we assayed the proteobacterial QS signals acyl-homoserine lactones (AHLs), which were significantly increased in the rhizosphere. To investigate the linkage between soil signaling and N cycling, we characterized 533 bacterial isolates from Avena rhizosphere: 24% had chitinase or protease activity and AHL production; disruption of QS in 7 of 8 eight isolates disrupted enzyme activity. Many {alpha}-Proteobacteria were newly found with QS-controlled extracellular enzyme activity. Enhanced specific activities of N-cycling enzymes accompanied by bacterial density-dependent behaviors in rhizosphere soil gives rise to the hypothesis that QS could be a control point in the complex process of rhizosphere N-mineralization.

DeAngelis, K.M.; Lindow, S.E.; Firestone, M.K.

2008-10-01

199

Identification of quorum sensing-controlled genes in Burkholderia ambifaria.  

PubMed

The Burkholderia cepacia complex (Bcc) comprises strains with a virulence potential toward immunocompromised patients as well as plant growth-promoting rhizobacteria (PGPR). Owing to the link between quorum sensing (QS) and virulence, most studies among Bcc species have been directed toward QS of pathogenic bacteria. We have investigated the QS of B. ambifaria, a PGPR only infrequently recovered from patients. The cepI gene, responsible for the synthesis of the main signaling molecule N-octanoylhomoserine lactone (C8 -HSL), was inactivated. Phenotypes of the B. ambifaria cepI mutant we observed, such as increased production of siderophores and decreased proteolytic and antifungal activities, are in agreement with those of other Bcc cepI mutants. The cepI mutant was then used as background strain for a whole-genome transposon-insertion mutagenesis strategy, allowing the identification of 20 QS-controlled genes, corresponding to 17 loci. The main functions identified are linked to antifungal and antimicrobial properties, as we have identified QS-controlled genes implicated in the production of pyrrolnitrin, burkholdines (occidiofungin-like molecules), and enacyloxins. This study provides insights in the QS-regulated functions of a PGPR, which could lead to beneficial potential biotechnological applications. PMID:23382083

Chapalain, Annelise; Vial, Ludovic; Laprade, Natacha; Dekimpe, Valérie; Perreault, Jonathan; Déziel, Eric

2013-04-01

200

Inhibition of quorum sensing in Pseudomonas aeruginosa by sesquiterpene lactones.  

PubMed

Six sesquiterpene lactones (SLs) of the goyazensolide and isogoyazensolide-type isolated from the Argentine herb Centratherum punctatum were evaluated on their ability to inhibit virulence factors of Pseudomonas aeruginosa ATCC 27853. Although compounds were not able to completely inhibit bacterial growth at 200?g/ml, the SLs do altered biofilm formation, elastase activity, and production of N-acyl-homoserinelactones (AHLs) which are known quorum sensing autoinducers at lower concentration. Compounds 2, 3, and 5 displayed significant inhibitory effects on P. aeruginosa biofilm formation at 0.5?g/ml being compound 3 (1.32?M) the most potent (42%). Compounds 2, 3, 4, 5 and 6, inhibited 39, 44, 42, 32 and 35% the production of AHLs at 100?g/ml and inhibited by more than 50% the elastase activity at 0.5?g/ml. Our results clearly indicated that sesquiterpene lactones are good candidates for the development of new antimicrobial agents acting not as bactericidal but as antipathogenic agents. PMID:22925726

Amaya, Susana; Pereira, José A; Borkosky, Susana A; Valdez, Juan C; Bardón, Alicia; Arena, Mario E

2012-10-15

201

Functions and regulation of quorum-sensing in Agrobacterium tumefaciens  

PubMed Central

In Agrobacterium tumefaciens, horizontal transfer and vegetative replication of oncogenic Ti plasmids involve a cell-to-cell communication process called quorum-sensing (QS). The determinants of the QS-system belong to the LuxR/LuxI class. The LuxI-like protein TraI synthesizes N-acyl-homoserine lactone molecules which act as diffusible QS-signals. Beyond a threshold concentration, these molecules bind and activate the LuxR-like transcriptional regulator TraR, thereby initiating the QS-regulatory pathway. For the last 20 years, A. tumefaciens has stood as a prominent model in the understanding of the LuxR/LuxI type of QS systems. A number of studies also unveiled features which are unique to A. tumefaciens QS, some of them being directly related to the phytopathogenic lifestyle of the bacteria. In this review, we will present the current knowledge of QS in A. tumefaciens at both the genetic and molecular levels. We will also describe how interactions with plant host modulate the QS pathway of A. tumefaciens, and discuss what could be the advantages for the agrobacteria to use such a tightly regulated QS-system to disseminate the Ti plasmids. PMID:24550924

Lang, Julien; Faure, Denis

2014-01-01

202

Identification of quorum sensing-controlled genes in Burkholderia ambifaria  

PubMed Central

The Burkholderia cepacia complex (Bcc) comprises strains with a virulence potential toward immunocompromised patients as well as plant growth–promoting rhizobacteria (PGPR). Owing to the link between quorum sensing (QS) and virulence, most studies among Bcc species have been directed toward QS of pathogenic bacteria. We have investigated the QS of B. ambifaria, a PGPR only infrequently recovered from patients. The cepI gene, responsible for the synthesis of the main signaling molecule N-octanoylhomoserine lactone (C8-HSL), was inactivated. Phenotypes of the B. ambifaria cepI mutant we observed, such as increased production of siderophores and decreased proteolytic and antifungal activities, are in agreement with those of other Bcc cepI mutants. The cepI mutant was then used as background strain for a whole-genome transposon-insertion mutagenesis strategy, allowing the identification of 20 QS-controlled genes, corresponding to 17 loci. The main functions identified are linked to antifungal and antimicrobial properties, as we have identified QS-controlled genes implicated in the production of pyrrolnitrin, burkholdines (occidiofungin-like molecules), and enacyloxins. This study provides insights in the QS-regulated functions of a PGPR, which could lead to beneficial potential biotechnological applications. PMID:23382083

Chapalain, Annelise; Vial, Ludovic; Laprade, Natacha; Dekimpe, Valérie; Perreault, Jonathan; Déziel, Eric

2013-01-01

203

Anti-quorum sensing potential of the mangrove Rhizophora annamalayana.  

PubMed

The present study was carried out to assess the anti-quorum sensing (anti-QS) activity of bark extract obtained from the mangrove plant Rhizophora annamalayana Kathir. against Gram-negative bacteria. In microtitre plate assay, the bark extract at a concentration of 1 mg/ml inhibited the QS-dependent violacein production in Chromobacterium violaceum ATCC 12472. Further, the QS-dependent bioluminescence production in the aquatic bacterial pathogen Vibrio harveyi MTCC 3438 was also reduced to the level of 99 % when treated with the same concentration of the extract. Gas chromatography-mass spectrum analysis identified the presence of seven different chemical constituents, 1H-purin-6-amine, cycloheptasiloxane, cyclooctasiloxane, cyclononasiloxane, cyclononasiloxane octadecamethyl, cyclodecasiloxane eicosamethyl and 1,1,1,5,7,7,7-heptamethyl-3,3-bis(trimethylsiloxy)tetrasiloxane. The molecular docking analysis of the identified compounds revealed that the compounds cyclononasiloxane octadecamethyl and cyclodecasiloxane eicosamethyl exhibited the best docking energy with the QS receptors of C. violaceum and V. harveyi with that of the natural ligand N -hexanoyl- L -homoserine lactone (C6-HSL) and furanosyl borate diester (AI-2). Similarly, another compound 1,1,1,5,7,7,7-heptamethyl-3,3-bis(trimethylsiloxy)tetrasiloxane showed best docking energy only against C6-HSL. Thus, the results of the present study divulge the activity of R. annamalayana bark extract to interfere with bacterial QS. PMID:23591758

Musthafa, Khadar Syed; Sahu, Sunil Kumar; Ravi, Arumugam Veera; Kathiresan, Kandasamy

2013-10-01

204

Virulence of Burkholderia mallei Quorum-Sensing Mutants  

PubMed Central

Many Proteobacteria use acyl-homoserine lactone-mediated quorum-sensing (QS) to activate specific sets of genes as a function of cell density. QS often controls the virulence of pathogenic species, and in fact a previous study indicated that QS was important for Burkholderia mallei mouse lung infections. To gain in-depth information on the role of QS in B. mallei virulence, we constructed and characterized a mutant of B. mallei strain GB8 that was unable to make acyl-homoserine lactones. The QS mutant showed virulence equal to that of its wild-type parent in an aerosol mouse infection model, and growth in macrophages was indistinguishable from that of the parent strain. Furthermore, we assessed the role of QS in B. mallei ATCC 23344 by constructing and characterizing a mutant strain producing AiiA, a lactonase enzyme that degrades acyl-homoserine lactones. Although acyl-homoserine lactone levels in cultures of this strain are very low, it showed full virulence. Contrary to the previous report, we conclude that QS is not required for acute B. mallei infections of mice. QS may be involved in some stage of chronic infections in the natural host of horses, or the QS genes may be remnants of the QS network in B. pseudomallei from which this host-adapted pathogen evolved. PMID:23429539

Majerczyk, Charlotte; Kinman, Loren; Han, Tony; Bunt, Richard

2013-01-01

205

Quorum-Sensing Antagonistic Activities of Azithromycin in Pseudomonas aeruginosa PAO1: a Global Approach  

PubMed Central

The administration of macrolides such as azithromycin for chronic pulmonary infection of cystic fibrosis patients has been reported to be of benefit. Although the mechanisms of action remain obscure, anti-inflammatory effects as well as interference of the macrolide with Pseudomonas aeruginosa virulence factor production have been suggested to contribute to an improved clinical outcome. In this study we used a systematic approach and analyzed the impact of azithromycin on the global transcriptional pattern and the protein expression profile of P. aeruginosa PAO1 cultures versus those in untreated controls. The most remarkable result of this study is the finding that azithromycin exhibited extensive quorum-sensing antagonistic activities. In accordance with the inhibition of the quorum-sensing systems, virulence factor production was diminished and the oxidative stress response was impaired, whereas the type III secretion system was strongly induced. Moreover, P. aeruginosa motility was reduced, which probably accounts for the previously observed impaired biofilm formation capabilities of azithromycin-treated cultures. The interference of azithromycin with quorum-sensing-dependent virulence factor production, biofilm formation, and oxidative stress resistance in P. aeruginosa holds great promise for macrolide therapy in cystic fibrosis. Clearly quorum-sensing antagonist macrolides should be paid more attention in the management of chronic P. aeruginosa infections, and as quorum-sensing antagonists, macrolides might gain vital importance for more general application against chronic infections. PMID:16641435

Nalca, Yusuf; Jänsch, Lothar; Bredenbruch, Florian; Geffers, Robert; Buer, Jan; Häussler, Susanne

2006-01-01

206

Anti-Quorum Sensing Activity of the Traditional Chinese Herb, Phyllanthus amarus  

PubMed Central

The discovery of quorum sensing in Proteobacteria and its function in regulating virulence determinants makes it an attractive alternative towards attenuation of bacterial pathogens. In this study, crude extracts of Phyllanthus amarus Schumach. & Thonn, a traditional Chinese herb, were screened for their anti-quorum sensing properties through a series of bioassays. Only the methanolic extract of P. amarus exhibited anti-quorum sensing activity, whereby it interrupted the ability of Chromobacterium violaceum CVO26 to response towards exogenously supplied N-hexanoylhomoserine lactone and the extract reduced bioluminescence in E. coli [pSB401] and E. coli [pSB1075]. In addition to this, methanolic extract of P. amarus significantly inhibited selected quorum sensing-regulated virulence determinants of Pseudomonas aeruginosa PA01. Increasing concentrations of the methanolic extracts of P. amarus reduced swarming motility, pyocyanin production and P. aeruginosa PA01 lecA?lux expression. Our data suggest that P. amarus could be useful for attenuating pathogens and hence, more local traditional herbs should be screened for its anti-quorum sensing properties as their active compounds may serve as promising anti-pathogenic drugs. PMID:24169540

Priya, Kumutha; Yin, Wai-Fong; Chan, Kok-Gan

2013-01-01

207

Anti-quorum sensing activity of the traditional Chinese herb, Phyllanthus amarus.  

PubMed

The discovery of quorum sensing in Proteobacteria and its function in regulating virulence determinants makes it an attractive alternative towards attenuation of bacterial pathogens. In this study, crude extracts of Phyllanthus amarus Schumach. & Thonn, a traditional Chinese herb, were screened for their anti-quorum sensing properties through a series of bioassays. Only the methanolic extract of P. amarus exhibited anti-quorum sensing activity, whereby it interrupted the ability of Chromobacterium violaceum CVO26 to response towards exogenously supplied N-hexanoylhomoserine lactone and the extract reduced bioluminescence in E. coli [pSB401] and E. coli [pSB1075]. In addition to this, methanolic extract of P. amarus significantly inhibited selected quorum sensing-regulated virulence determinants of Pseudomonas aeruginosa PA01. Increasing concentrations of the methanolic extracts of P. amarus reduced swarming motility, pyocyanin production and P. aeruginosa PA01 lecA::lux expression. Our data suggest that P. amarus could be useful for attenuating pathogens and hence, more local traditional herbs should be screened for its anti-quorum sensing properties as their active compounds may serve as promising anti-pathogenic drugs. PMID:24169540

Priya, Kumutha; Yin, Wai-Fong; Chan, Kok-Gan

2013-01-01

208

Quorum sensing inhibitory activities of surface immobilized antibacterial dihydropyrrolones via click chemistry.  

PubMed

Device-related infection remains a major barrier to the use of biomaterial implants as life-saving devices. This study aims to examine the effectiveness and mechanism of action of surface attached dihydropyrrolones (DHPs), a quorum sensing (QS) inhibitor, against bacterial colonization. DHPs were covalently attached on glass surfaces via copper-catalyzed azide-alkyne 1,3-dipolar cycloaddition (CuAAC) click reaction. The covalent attachment of DHP surfaces was confirmed by X-ray photoelectron spectroscopy (XPS) and contact angle measurements, and the antimicrobial efficacy of the DHP coatings was assessed by confocal laser scanning microscopy (CLSM) and image analysis. The results demonstrated that covalently bound DHP compounds are effective in reducing the adhesion by up to 97% (p < 0.05) for both Pseudomonas aeruginosa and Staphylococcus aureus. Furthermore, using the green fluorescent protein (Gfp)-based reporter technology, it is demonstrated that surface attached DHPs were able to repress the expression of a lasB-gfp reporter fusion of P. aeruginosa by 72% (p < 0.001) without affecting cell viability. This demonstrates the ability of the covalently bound QS inhibitor to inhibit QS and suggests the existence of a membrane-based pathway(s) for QS inhibition. Hence, strategies based on incorporation of QS inhibitors such as DHPs represent a potential approach for prevention of device-related infections. PMID:24345737

Ho, Kitty K K; Chen, Renxun; Willcox, Mark D P; Rice, Scott A; Cole, Nerida; Iskander, George; Kumar, Naresh

2014-02-01

209

Type 2 quorum sensing monitoring, inhibition and biofilm formation in marine microrganisms.  

PubMed

The quorum sensing (QS) dependent behaviour of micro-organisms, in particular expression of virulence genes, biofilm formation and dispersal, have provided impetus for investigating practical approaches to interfere with microbial QS. This study tests Halomonas pacifica and Marinobacter hydrocarbonoclasticus, two halophilic marine micro-organism, for their AI-2 dependent QS signalling and the effect of two well-known quorum-sensing inhibitors (QSIs), patulin and penicillic acid, on biofilm formation. We report, for the first time, the successful amplification of a putative luxS gene in H. pacifica using degenerated primers and AI-2 dependent QS as well as inhibition using QSIs. Penicillic acid had a strong inhibitory effect on AI-2 induction of H. pacifica at non-growth inhibitory concentrations, while patulin has an adverse effect only at the highest concentration (25 ?M). QSIs effect on biofilm forming capability was isolate specific, with maximum inhibition at 25 ?M of patulin in H. pacifica. In M. hydrocarbonoclasticus, no adverse effects were noted at any tested concentration of either QSIs. Detection of bioluminescence and the presence of a putative luxS gene provide biochemical and genetic evidence for the production of a signalling molecule(s) which is the essential first step in characterizing H. pacifica QS. This study highlights the importance of AI-2 dependent QS in a marine setting, not previously reported. It further suggests that QSI compounds must be selected in the specific system in which they are to function, and they cannot easily be transferred from one QS system to another. PMID:24166155

Liaqat, Iram; Bachmann, Robert Thomas; Edyvean, Robert G J

2014-03-01

210

The Vibrio harveyi master quorum-sensing regulator, LuxR, a TetR-type protein is both an activator and a repressor: DNA  

E-print Network

The Vibrio harveyi master quorum-sensing regulator, LuxR, a TetR-type protein is both an activator, USA. 6 Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA. Summary Quorum sensing. The detection of these autoinducers ultimately leads to the produc- tion of LuxR, the quorum-sensing master

Bulyk, Martha L.

211

LuxU connects quorum sensing to biofilm formation in Vibrio fischeri  

E-print Network

LuxU connects quorum sensing to biofilm formation in Vibrio fischeri Valerie A. Ray and Karen L regulates bio- luminescence in this organism. Introduction Bacteria readily adapt to changing environmental condi- tions by sensing and integrating different cues present in their surroundings to produce

McFall-Ngai, Margaret

212

The Role of the QseC Sensor Kinase in Salmonella enterica serovar Typhimurium Quorum Sensing and Swine Colonization  

Technology Transfer Automated Retrieval System (TEKTRAN)

At least two quorum sensing molecules, autoinducer-3 (AI-3) and norepinephrine (NE), are present in the gastrointestinal tract and activate the E. coli QseBC quorum sensing system. AI-3 is produced by enteric bacteria, whereas NE is produced by the animal host, often during stress. Both 10% pre-co...

213

Synthetic furanones inhibit quorum-sensing and enhance bacterial clearance in Pseudomonas aeruginosa lung infection in mice  

Microsoft Academic Search

Introduction: Antibiotics are used to treat bacterial infections by killing the bacteria or inhibiting their growth, but resistance to antibiotics can develop readily. The discovery that bacterial quorum-sensing regu- lates bacterial virulence as well as the formation of biofilms opens up new ways to control certain bacterial infections. Furanone compounds capable of inhibiting bacterial quorum-sensing systems have been isolated from

H. Wu; Z. Song; M. Hentzer; J. B. Andersen; S. Molin; M. Givskov; N. Høiby

2004-01-01

214

Assessment of Anti-Quorum Sensing Activity for Some Ornamental and Medicinal Plants Native to Egypt  

PubMed Central

This study investigated the effects of some plant extracts on the bacterial communication system, expressed as quorum sensing (QS) activity. Quorum sensing has a directly proportional effect on the amount of certain compounds, such as pigments, produced by the bacteria. Alcohol extracts of 23 ornamental and medicinal plants were tested for anti-QS activity by the Chromobacterium violaceum assay using the agar cup diffusion method. The screening revealed the anti-QS activity of six plants; namely the leaves of Adhatoda vasica Nees, Bauhinia purpurea L., Lantana camara L., Myoporum laetum G. Forst.; the fruits of Piper longum L.; and the aerial parts of Taraxacum officinale F.H. Wigg. PMID:23641343

Zaki, Ahmed A.; Shaaban, Mona I.; Hashish, Nadia E.; Amer, Mohamed A.; Lahloub, Mohamed-Farid

2013-01-01

215

Dynamical quorum sensing and clustering dynamics in a population of spatially distributed active rotators  

NASA Astrophysics Data System (ADS)

A model of clustering dynamics is proposed for a population of spatially distributed active rotators. A transition from excitable to oscillatory dynamics is induced by the increase of the local density of active rotators. It is interpreted as dynamical quorum sensing. In the oscillation regime, phase waves propagate without decay, which generates an effectively long-range interaction in the clustering dynamics. The clustering process becomes facilitated and only one dominant cluster appears rapidly as a result of the dynamical quorum sensing. An exact localized solution is found to a simplified model equation, and the competitive dynamics between two localized states is studied numerically.

Sakaguchi, Hidetsugu; Maeyama, Satomi

2013-02-01

216

Dynamical quorum sensing and clustering dynamics in a population of spatially distributed active rotators  

E-print Network

A model of clustering dynamics is proposed for a population of spatially distributed active rotators. A transition from excitable to oscillatory dynamics is induced by the increase of the local density of active rotators. It is interpreted as dynamical quorum sensing. In the oscillation regime, phase waves propagate without decay, which generates an effectively long-range interaction in the clustering dynamics. The clustering process becomes facilitated and only one dominant cluster appears rapidly as a result of the dynamical quorum sensing. An exact localized solution is found to a simplified model equation, and the competitive dynamics between two localized states is studied numerically.

Hidetsugu Sakaguchi; Satomi Maeyama

2013-02-05

217

A model for signal transduction during quorum sensing in Vibrio harveyi  

NASA Astrophysics Data System (ADS)

We present a framework for analyzing luminescence regulation during quorum sensing in the bioluminescent bacterium Vibrio harveyi. Using a simplified model for signal transduction in the quorum sensing pathway, we identify key dimensionless parameters that control the system's response. These parameters are estimated using experimental data on luminescence phenotypes for different mutant strains. The corresponding model predictions are consistent with results from other experiments which did not serve as input for determining model parameters. Furthermore, the proposed framework leads to novel testable predictions for luminescence phenotypes and for responses of the network to different perturbations.

Banik, Suman K.; Fenley, Andrew T.; Kulkarni, Rahul V.

2009-12-01

218

Assessment of anti-quorum sensing activity for some ornamental and medicinal plants native to egypt.  

PubMed

This study investigated the effects of some plant extracts on the bacterial communication system, expressed as quorum sensing (QS) activity. Quorum sensing has a directly proportional effect on the amount of certain compounds, such as pigments, produced by the bacteria. Alcohol extracts of 23 ornamental and medicinal plants were tested for anti-QS activity by the Chromobacterium violaceum assay using the agar cup diffusion method. The screening revealed the anti-QS activity of six plants; namely the leaves of Adhatoda vasica Nees, Bauhinia purpurea L., Lantana camara L., Myoporum laetum G. Forst.; the fruits of Piper longum L.; and the aerial parts of Taraxacum officinale F.H. Wigg. PMID:23641343

Zaki, Ahmed A; Shaaban, Mona I; Hashish, Nadia E; Amer, Mohamed A; Lahloub, Mohamed-Farid

2013-03-01

219

Anti-quorum sensing potential of Adenanthera pavonina  

PubMed Central

Background: Quorum sensing (QS) in Pseudomonas aeruginosa plays a key role in virulence factor production, biofilm formation and antimicrobial resistance. Because of emerging antimicrobial resistance in P. aeruginosa, there is a need to find an alternate nonantibiotic agent for the control of infections caused by this organism. Objective: To evaluate anti-QS activity of Adenanthera pavonina L., a medicinal plant used in traditional medicine. Materials and Methods: Preliminary screening for anti-QS activity of ethanol extract of A. pavonina was carried out using Chromobacterium violaceum CV026 biosensor strain and inhibition of QS-regulated violacein production was quantified using C. violaceum ATCC12472. Bioassay guided fractionation of ethanol extract resulted in ethyl acetate fraction (AEF) with strong anti-QS activity and AEF was evaluated for inhibition of QS-regulated pyocyanin production, proteolytic, elastolytic activity, swarming motility and biofilm formation in P. aeruginosa PAO1. Results: AEF, at 0.5 mg/ml, inhibited pyocyanin production completely and at 1 mg/ml of AEF, complete inhibition of proteolytic and elastolytic activities were observed. However, viability of P. aeruginosa PAO1 was not affected at the tested concentrations of AEF as observed by cell count. Swarming motility was inhibited at the concentration of 0.1 mg/ml of AEF. Thin layer chromatography and biosensor overlay of AEF showed violacein inhibition zone at Rf value 0.63. Conclusion: From the results of this study, it can be concluded that A. pavonina extracts can be used as effective anti-QS agents. PMID:25598643

Vasavi, Halkare Suryanarayana; Arun, Ananthapadmanabha Bhagwath; Rekha, Punchappady-Devasya

2015-01-01

220

Quorum Sensing Influences Vibrio harveyi Growth Rates in a Manner Not Fully Accounted For by the Marker Effect of Bioluminescence  

PubMed Central

Background The light-emitting Vibrios provide excellent material for studying the interaction of cellular communication with growth rate because bioluminescence is a convenient marker for quorum sensing. However, the use of bioluminescence as a marker is complicated because bioluminescence itself may affect growth rate, e.g. by diverting energy. Methodology/Principal Findings The marker effect was explored via growth rate studies in isogenic Vibrio harveyi (Vh) strains altered in quorum sensing on the one hand, and bioluminescence on the other. By hypothesis, growth rate is energy limited: mutants deficient in quorum sensing grow faster because wild type quorum sensing unleashes bioluminescence and bioluminescence diverts energy. Findings reported here confirm a role for bioluminescence in limiting Vh growth rate, at least under the conditions tested. However, the results argue that the bioluminescence is insufficient to explain the relationship of growth rate and quorum sensing in Vh. A Vh mutant null for all genes encoding the bioluminescence pathway grew faster than wild type but not as fast as null mutants in quorum sensing. Vh quorum sensing mutants showed altered growth rates that do not always rank with their relative increase or decrease in bioluminescence. In addition, the cell-free culture fluids of a rapidly growing Vibrio parahaemolyticus (Vp) strain increased the growth rate of wild type Vh without significantly altering Vh's bioluminescence. The same cell-free culture fluid increased the bioluminescence of Vh quorum mutants. Conclusions/Significance The effect of quorum sensing on Vh growth rate can be either positive or negative and includes both bioluminescence-dependent and independent components. Bioluminescence tends to slow growth rate but not enough to account for the effects of quorum sensing on growth rate. PMID:18301749

Nackerdien, Zeena E.; Keynan, Alexander; Bassler, Bonnie L.; Lederberg, Joshua; Thaler, David S.

2008-01-01

221

Novel glycolipids synthesized using plant essential oils and their application in quorum sensing inhibition and as antibiofilm agents.  

PubMed

Essential oils (EOs) form an important part of traditional medicine so their anti-microbial and, in the recent past, antiquorum sensing activity has been well studied. However it is likely that due to their hydrophobic nature and reduced solubility in aqueous environments full potential of their activity cannot be realized. hence it is only rational to formulate a process to make these molecules more polar in nature. The present paper reports synthesis of sophorolipids using 12 different essential oils as substrates, thus providing surfactant-like properties to these EOs. The synthesis protocol makes the use of Candida bombicola ATCC 22214 as producer organism. The production process required 7 days of incubation at 28°C and 180?rpm. Preliminary characterization of the synthesized essential oil sophorolipids (EOSLs) was performed using thin layer chromatography (TLC) and Fourier transform infrared spectroscopy (FTIR). Additionally, essential oils that were incapable of mediating quorum sensing inhibition (QSI) on their own became potent quorum sensing inhibitors upon conversion into their corresponding EOSLs. Antibiofilm potential of these EOSLs was also demonstrated using V. cholerae as test organism. Use of essential oils as substrates for glycolipid synthesis has not been attempted previously, and hence this is the first report. PMID:24558341

Mukherji, Ruchira; Prabhune, Asmita

2014-01-01

222

Novel Glycolipids Synthesized Using Plant Essential Oils and Their Application in Quorum Sensing Inhibition and as Antibiofilm Agents  

PubMed Central

Essential oils (EOs) form an important part of traditional medicine so their anti-microbial and, in the recent past, antiquorum sensing activity has been well studied. However it is likely that due to their hydrophobic nature and reduced solubility in aqueous environments full potential of their activity cannot be realized. hence it is only rational to formulate a process to make these molecules more polar in nature. The present paper reports synthesis of sophorolipids using 12 different essential oils as substrates, thus providing surfactant-like properties to these EOs. The synthesis protocol makes the use of Candida bombicola ATCC 22214 as producer organism. The production process required 7 days of incubation at 28°C and 180?rpm. Preliminary characterization of the synthesized essential oil sophorolipids (EOSLs) was performed using thin layer chromatography (TLC) and Fourier transform infrared spectroscopy (FTIR). Additionally, essential oils that were incapable of mediating quorum sensing inhibition (QSI) on their own became potent quorum sensing inhibitors upon conversion into their corresponding EOSLs. Antibiofilm potential of these EOSLs was also demonstrated using V. cholerae as test organism. Use of essential oils as substrates for glycolipid synthesis has not been attempted previously, and hence this is the first report. PMID:24558341

Prabhune, Asmita

2014-01-01

223

Whole-Genome Analysis of Aeromonas hydrophila Strain 187, Exhibiting Quorum-Sensing Activity.  

PubMed

Aeromonas hydrophila is a quorum-sensing (QS) bacterium that causes diarrhea in humans upon infection. Here, we report the genome of pathogenic Aeromonas hydrophila strain 187, which possesses a QS gene responsible for signaling molecule N-acyl homoserine lactone (AHL) synthesis and has been found to be located at contig 36. PMID:25540357

Chan, Xin-Yue; Chua, Kek Heng; Yin, Wai-Fong; Puthucheary, S D; Chan, Kok-Gan

2014-01-01

224

Whole-Genome Analysis of Aeromonas hydrophila Strain 187, Exhibiting Quorum-Sensing Activity  

PubMed Central

Aeromonas hydrophila is a quorum-sensing (QS) bacterium that causes diarrhea in humans upon infection. Here, we report the genome of pathogenic Aeromonas hydrophila strain 187, which possesses a QS gene responsible for signaling molecule N-acyl homoserine lactone (AHL) synthesis and has been found to be located at contig 36. PMID:25540357

Chan, Xin-Yue; Chua, Kek Heng; Yin, Wai-Fong; Puthucheary, S. D.

2014-01-01

225

Visualizing Bacteria Quorum Sensing Maria Schwarz, Daniela Romano and Marian Gheorghe1  

E-print Network

Visualizing Bacteria Quorum Sensing Maria Schwarz, Daniela Romano and Marian Gheorghe1 12 Abstract. Large populations of bacteria communicate by sending into the environment some specific signalling is presented in [1]. Bacteria use QS to coordinate different behaviours. For example the light emission

Romano, Daniela

226

A qrr noncoding RNA deploys four different regulatory mechanisms to optimize quorum-sensing dynamics.  

PubMed

Quorum sensing is a cell-cell communication process that bacteria use to transition between individual and social lifestyles. In vibrios, homologous small RNAs called the Qrr sRNAs function at the center of quorum-sensing pathways. The Qrr sRNAs regulate multiple mRNA targets including those encoding the quorum-sensing regulatory components luxR, luxO, luxM, and aphA. We show that a representative Qrr, Qrr3, uses four distinct mechanisms to control its particular targets: the Qrr3 sRNA represses luxR through catalytic degradation, represses luxM through coupled degradation, represses luxO through sequestration, and activates aphA by revealing the ribosome binding site while the sRNA itself is degraded. Qrr3 forms different base-pairing interactions with each mRNA target, and the particular pairing strategy determines which regulatory mechanism occurs. Combined mathematical modeling and experiments show that the specific Qrr regulatory mechanism employed governs the potency, dynamics, and competition of target mRNA regulation, which in turn, defines the overall quorum-sensing response. PMID:25579683

Feng, Lihui; Rutherford, Steven T; Papenfort, Kai; Bagert, John D; van Kessel, Julia C; Tirrell, David A; Wingreen, Ned S; Bassler, Bonnie L

2015-01-15

227

Quantifying the Integration of Quorum-Sensing Signals with Single-Cell Resolution  

E-print Network

Medical Institute, Chevy Chase, Maryland, United States of America Cell-to-cell communication in bacteria.1371/journal.pbio.1000068 Introduction In a process called quorum sensing, bacteria communicate with one-positive bacteria (e.g., Bacillus) can use several peptides for communication [2,6]. These bacteria have evolved

Ong, N. P.

228

Evolutionary theory of bacterial quorum sensing: when is a signal not a signal?  

E-print Network

) and between bacteria and higher organisms (inter-kingdom). The fact that QS-based communication appears The term quorum sensing (QS) is used to describe the communication between bacterial cells, whereby to be widespread among microbes is strange, considering that explaining both cooperation and communication are two

West, Stuart

229

Natural Genome Diversity of AI-2 Quorum Sensing in Escherichia coli: Conserved Signal Production but Labile  

E-print Network

bacteria to be effective, that is, high cell density. Quorum sensing (QS) is a key communication system behaviors. Key words: genome evolution, gene loss, E. coli, balancing selection, social cheater, bacteria, bacteria can express complex coordinated multicellular behaviors, such as biofilm formation, antibiotic

Gordo, Isabel

230

Phosphorylation and Processing of the Quorum-Sensing Molecule Autoinducer-2 in Enteric Bacteria  

E-print Network

-6789 ABSTRACT Quorum sensing is a process of chemical communication that bacteria use to assess cell population with the signaling capabilities of neighboring species of bacteria. We have previously shown that Salmonella enterica a "universal" bacterial signal. Many bacteria control a variety of niche-specific behaviors in response to AI-2

Rabinowitz, Joshua D.

231

Density-dependent fitness benefits in quorum-sensing bacterial populations  

E-print Network

that bacteria communicate using small diffusible signal molecules to coordinate, among other things (QS) to coordinate behaviors at the population level (1­7). Cells produce and release QS signaling, the production of factors that are secreted outside of the cells in a process known as quorum sensing (QS

West, Stuart

232

Clustering in Sensor Networks using Quorum Sensing Ibiso Wokoma, Dr. Lionel Sacks, Dr. Ian Marshall  

E-print Network

Sensing (QS) is a type of intercellular signalling used by bacteria to monitor cell density for a variety the gene expression of the luminescent bacteria is regulated according to cell-density [4 the application layer. The protocol developed was inspired by the bacterial signalling process called quorum

Haddadi, Hamed

233

Whole-Genome Sequence of Quorum-Sensing Vibrio tubiashii Strain T33.  

PubMed

Vibrio tubiashii strain T33 was isolated from the coastal waters of Morib, Malaysia, and was shown to possess quorum-sensing activity similar to that of its famous relative Vibrio fischeri. Here, the assembly and annotation of its genome are presented. PMID:25555738

Izzati Mohamad, Nur; Yin, Wai-Fong; Chan, Kok-Gan

2015-01-01

234

MicroBQs: a centralized database for use in studying bacterial biofilms and quorum sensing  

Technology Transfer Automated Retrieval System (TEKTRAN)

Biofilm formation in many bacterial species may be negatively or positively regulated by cell-to-cell signaling systems referred to as quorum sensing (QS). To assist in understanding research related to biofilms, QS, and the role of QS in biofilm formation, a comprehensive, centralized database, kn...

235

Geminal dihalogen isosteric replacement in hydrated AI-2 affords potent quorum sensing modulators.  

PubMed

Hydrated carbonyl groups in AI-2, a quorum sensing autoinducer, make key hydrogen bonding interactions in the binding site of LsrR (a transcriptional regulator). This can be recapitulated with geminal dibromides, via halogen bonding. Geminal dihalogens represent interesting isosteric replacements for hydrated carbonyls in ligands and are currently under-utilized in ligand design. PMID:25573337

Guo, Min; Zheng, Yue; Terell, Jessica L; Ad, Michal; Opoku-Temeng, Clement; Bentley, William E; Sintim, Herman O

2015-01-29

236

Biofilm Formation and Sloughing in Serratia marcescens Are Controlled by Quorum Sensing and Nutrient Cues  

Microsoft Academic Search

We describe here a role for quorum sensing in the detachment, or sloughing, of Serratia marcescens filamentous biofilms, and we show that nutrient conditions affect the biofilm morphotype. Under reduced carbon or nitrogen conditions, S. marcescens formed a classical biofilm consisting of microcolonies. The filamentous biofilm could be converted to a microcolony-type biofilm by switching the medium after estab- lishment

S. A. Rice; K. S. Koh; S. Y. Queck; M. Labbate; K. W. Lam; S. Kjelleberg

2005-01-01

237

Noise regulation by quorum sensing in low mRNA copy number systems  

Microsoft Academic Search

BACKGROUND: Cells must face the ubiquitous presence of noise at the level of signaling molecules. The latter constitutes a major challenge for the regulation of cellular functions including communication processes. In the context of prokaryotic communication, the so-called quorum sensing (QS) mechanism relies on small diffusive molecules that are produced and detected by cells. This poses the intriguing question of

Marc Weber; Javier Buceta

2011-01-01

238

Whole-Genome Sequence of Quorum-Sensing Vibrio tubiashii Strain T33  

PubMed Central

Vibrio tubiashii strain T33 was isolated from the coastal waters of Morib, Malaysia, and was shown to possess quorum-sensing activity similar to that of its famous relative Vibrio fischeri. Here, the assembly and annotation of its genome are presented. PMID:25555738

Izzati Mohamad, Nur; Yin, Wai-Fong

2015-01-01

239

Whole-Genome Sequencing Analysis of Quorum-Sensing Aeromonas hydrophila Strain M023 from Freshwater  

PubMed Central

Aeromonas hydrophila is a well-known waterborne pathogen that recently was found to infect humans. Here, we report the draft genome of a freshwater isolate from a Malaysian waterfall, A. hydrophila strain M023, which portrays N-acylhomoserine lactone-dependent quorum sensing.

Tan, Wen-Si; Yin, Wai-Fong; Chang, Chien-Yi

2015-01-01

240

A Mathematical model to investigate quorum sensing regulation and its heterogenecity in pseudomonas syringae on leaves  

Technology Transfer Automated Retrieval System (TEKTRAN)

The bacterium Pseudomonas syringae is a plant-pathogen, which through quorum sensing (QS), controls virulence. In this paper, by means of mathematical modeling, we investigate QS of this bacterium when living on leaf surfaces. We extend an existing stochastic model for the formation of Pseudomonas s...

241

Selective Chemical Inhibition of agr Quorum Sensing in Staphylococcus aureus Promotes Host Defense with Minimal Impact on Resistance  

PubMed Central

Bacterial signaling systems are prime drug targets for combating the global health threat of antibiotic resistant bacterial infections including those caused by Staphylococcus aureus. S. aureus is the primary cause of acute bacterial skin and soft tissue infections (SSTIs) and the quorum sensing operon agr is causally associated with these. Whether efficacious chemical inhibitors of agr signaling can be developed that promote host defense against SSTIs while sparing the normal microbiota of the skin is unknown. In a high throughput screen, we identified a small molecule inhibitor (SMI), savirin (S. aureus virulence inhibitor) that disrupted agr-mediated quorum sensing in this pathogen but not in the important skin commensal Staphylococcus epidermidis. Mechanistic studies employing electrophoretic mobility shift assays and a novel AgrA activation reporter strain revealed the transcriptional regulator AgrA as the target of inhibition within the pathogen, preventing virulence gene upregulation. Consistent with its minimal impact on exponential phase growth, including skin microbiota members, savirin did not provoke stress responses or membrane dysfunction induced by conventional antibiotics as determined by transcriptional profiling and membrane potential and integrity studies. Importantly, savirin was efficacious in two murine skin infection models, abating tissue injury and selectively promoting clearance of agr+ but not ?agr bacteria when administered at the time of infection or delayed until maximal abscess development. The mechanism of enhanced host defense involved in part enhanced intracellular killing of agr+ but not ?agr in macrophages and by low pH. Notably, resistance or tolerance to savirin inhibition of agr was not observed after multiple passages either in vivo or in vitro where under the same conditions resistance to growth inhibition was induced after passage with conventional antibiotics. Therefore, chemical inhibitors can selectively target AgrA in S. aureus to promote host defense while sparing agr signaling in S. epidermidis and limiting resistance development. PMID:24945495

Sully, Erin K.; Malachowa, Natalia; Elmore, Bradley O.; Alexander, Susan M.; Femling, Jon K.; Gray, Brian M.; DeLeo, Frank R.; Otto, Michael; Cheung, Ambrose L.; Edwards, Bruce S.; Sklar, Larry A.; Horswill, Alexander R.; Hall, Pamela R.; Gresham, Hattie D.

2014-01-01

242

Quorum-sensing-directed protein expression in Serratia proteamaculans B5a  

Microsoft Academic Search

N-Acyl-L-homoserine-lactone-producing Serratia species are frequently encountered in spoiling foods of vegetable and protein origin. The role of quorum sensing in the food spoiling properties of these bacteria is currently being investigated. A set of luxR luxI homologous genes encoding a putative quorum sensor was identified in the N-(3-oxo-hexanoyl)-L-homoserine lactone (3-oxo-C6- HSL)-producing Serratia proteamaculans strain B5a. The 3-oxo-C6-HSL synthase SprI showed

Allan B. Christensen; Kathrin Riedel; Leo Eberl; Lars R. Flodgaard; Søren Molin; Lone Gram; Michael Givskov

2003-01-01

243

Synthesis and biological activities of some 1,3-benzoxazol-2(3H)-one derivatives as anti-quorum sensing agents.  

PubMed

Antibiotics are commonly used to treat microbial infections. Due to misuse or large-scale use of antibiotics, many pathogens have gained resistance which makes antibiotic treatments ineffective. The discovery that many bacteria use quorum sensing (QS) to regulate their virulence factor and pathogenicity production makes the QS system an attractive target for antimicrobial therapy. A series of 1,3-benzoxazol-2(3H)-one derivatives were designed and synthesized as QS inhibitors (QSIs) and tested for their QS inhibitory activities. In vitro quorum sensing inhibitor screen (QSIS) assay indicated that the 1,3-benzoxazol-2(3H)-one (compound 1), 5-chloro-1,3-benzoxazol-2(3H)-one (compound 6), 6-methyl-1,3-benzoxazol-2(3H)-one (compound 11), and 5-methyl-1,3-benzoxazol-2(3H)-one (compound 16), inhibit QS system in quorum sensing selector (QSIS)1 strain. These 4 QSIs also significantly reduced elastase production, biofilm formation and swarming motility of Pseudomonas aeruginosa PA01 strain. These results suggest that compound 1, 6, 11 and 16 may provide a starting point for the design and development of new anti-pathogenic drugs that restrict virulence of P. aeruginosa and possibly other clinically important human pathogens. In addition, these QSI molecules could potentially be used in combination with conventional antibiotics to increase the efficiency of disease control and to extend the life span of established antimicrobials. PMID:22588631

Miandji, A M; Ulusoy, S; Dündar, Y; Ozgen, S; Onurda?, F K; Bo?gelmez-T?naz, G; Noyanalpan, N

2012-07-01

244

Quorum-sensing regulators control virulence gene expression in Vibrio cholerae  

Microsoft Academic Search

The production of virulence factors including cholera toxin and the toxin-coregulated pilus in the human pathogen Vibrio cholerae is strongly influenced by environmental conditions. The well-characterized ToxR signal transduction cascade is responsible for sensing and integrating the environmental information and controlling the virulence regulon. We show here that, in addition to the known components of the ToxR signaling circuit, quorum-sensing

Jun Zhu; Melissa B. Miller; Russell E. Vance; Michelle Dziejman; John J. Mekalanos

2002-01-01

245

Ajoene, a sulfur-rich molecule from garlic, inhibits genes controlled by quorum sensing.  

PubMed

In relation to emerging multiresistant bacteria, development of antimicrobials and new treatment strategies of infections should be expected to become a high-priority research area. Quorum sensing (QS), a communication system used by pathogenic bacteria like Pseudomonas aeruginosa to synchronize the expression of specific genes involved in pathogenicity, is a possible drug target. Previous in vitro and in vivo studies revealed a significant inhibition of P. aeruginosa QS by crude garlic extract. By bioassay-guided fractionation of garlic extracts, we determined the primary QS inhibitor present in garlic to be ajoene, a sulfur-containing compound with potential as an antipathogenic drug. By comprehensive in vitro and in vivo studies, the effect of synthetic ajoene toward P. aeruginosa was elucidated. DNA microarray studies of ajoene-treated P. aeruginosa cultures revealed a concentration-dependent attenuation of a few but central QS-controlled virulence factors, including rhamnolipid. Furthermore, ajoene treatment of in vitro biofilms demonstrated a clear synergistic, antimicrobial effect with tobramycin on biofilm killing and a cease in lytic necrosis of polymorphonuclear leukocytes. Furthermore, in a mouse model of pulmonary infection, a significant clearing of infecting P. aeruginosa was detected in ajoene-treated mice compared to a nontreated control group. This study adds to the list of examples demonstrating the potential of QS-interfering compounds in the treatment of bacterial infections. PMID:22314537

Jakobsen, Tim Holm; van Gennip, Maria; Phipps, Richard Kerry; Shanmugham, Meenakshi Sundaram; Christensen, Louise Dahl; Alhede, Morten; Skindersoe, Mette Eline; Rasmussen, Thomas Bovbjerg; Friedrich, Karlheinz; Uthe, Friedrich; Jensen, Peter Østrup; Moser, Claus; Nielsen, Kristian Fog; Eberl, Leo; Larsen, Thomas Ostenfeld; Tanner, David; Høiby, Niels; Bjarnsholt, Thomas; Givskov, Michael

2012-05-01

246

Ajoene, a Sulfur-Rich Molecule from Garlic, Inhibits Genes Controlled by Quorum Sensing  

PubMed Central

In relation to emerging multiresistant bacteria, development of antimicrobials and new treatment strategies of infections should be expected to become a high-priority research area. Quorum sensing (QS), a communication system used by pathogenic bacteria like Pseudomonas aeruginosa to synchronize the expression of specific genes involved in pathogenicity, is a possible drug target. Previous in vitro and in vivo studies revealed a significant inhibition of P. aeruginosa QS by crude garlic extract. By bioassay-guided fractionation of garlic extracts, we determined the primary QS inhibitor present in garlic to be ajoene, a sulfur-containing compound with potential as an antipathogenic drug. By comprehensive in vitro and in vivo studies, the effect of synthetic ajoene toward P. aeruginosa was elucidated. DNA microarray studies of ajoene-treated P. aeruginosa cultures revealed a concentration-dependent attenuation of a few but central QS-controlled virulence factors, including rhamnolipid. Furthermore, ajoene treatment of in vitro biofilms demonstrated a clear synergistic, antimicrobial effect with tobramycin on biofilm killing and a cease in lytic necrosis of polymorphonuclear leukocytes. Furthermore, in a mouse model of pulmonary infection, a significant clearing of infecting P. aeruginosa was detected in ajoene-treated mice compared to a nontreated control group. This study adds to the list of examples demonstrating the potential of QS-interfering compounds in the treatment of bacterial infections. PMID:22314537

Jakobsen, Tim Holm; van Gennip, Maria; Phipps, Richard Kerry; Shanmugham, Meenakshi Sundaram; Christensen, Louise Dahl; Alhede, Morten; Skindersoe, Mette Eline; Rasmussen, Thomas Bovbjerg; Friedrich, Karlheinz; Uthe, Friedrich; Jensen, Peter Østrup; Moser, Claus; Nielsen, Kristian Fog; Eberl, Leo; Larsen, Thomas Ostenfeld; Tanner, David; Høiby, Niels; Bjarnsholt, Thomas

2012-01-01

247

Bridging adaptive estimation and control with modern machine learning : a quorum sensing inspired algorithm for dynamic clustering  

E-print Network

Quorum sensing is a decentralized biological process, by which a community of bacterial cells with no global awareness can coordinate their functional behaviors based only on local decision and cell-medium interaction. ...

Tan, Feng, S.M. Massachusetts Institute of Technology

2012-01-01

248

A nitric oxide-responsive quorum sensing circuit in Vibrio harveyi regulates flagella production and biofilm formation.  

PubMed

Cell signaling plays an important role in the survival of bacterial colonies. They use small molecules to coordinate gene expression in a cell density dependent manner. This process, known as quorum sensing, helps bacteria regulate diverse functions such as bioluminescence, biofilm formation and virulence. In Vibrio harveyi, a bioluminescent marine bacterium, four parallel quorum-sensing systems have been identified to regulate light production. We have previously reported that nitric oxide (NO), through the H-NOX/HqsK quorum sensing pathway contributes to light production in V. harveyi through the LuxU/LuxO/LuxR quorum sensing pathway. In this study, we show that nitric oxide (NO) also regulates flagellar production and enhances biofilm formation. Our data suggest that V. harveyi is capable of switching between lifestyles to be able to adapt to changes in the environment. PMID:23965964

Henares, Bernadette M; Xu, Yueming; Boon, Elizabeth M

2013-01-01

249

Ligand-Induced Asymmetry in Histidine Sensor Kinase Complex Regulates Quorum Sensing  

SciTech Connect

Bacteria sense their environment using receptors of the histidine sensor kinase family, but how kinase activity is regulated by ligand binding is not well understood. Autoinducer-2 (AI-2), a secreted signaling molecule originally identified in studies of the marine bacterium Vibrio harveyi, regulates quorum-sensing responses and allows communication between different bacterial species. AI-2 signal transduction in V. harveyi requires the integral membrane receptor LuxPQ, comprised of periplasmic binding protein (LuxP) and histidine sensor kinase (LuxQ) subunits. Combined X-ray crystallographic and functional studies show that AI-2 binding causes a major conformational change within LuxP, which in turn stabilizes a quaternary arrangement in which two LuxPQ monomers are asymmetrically associated. We propose that formation of this asymmetric quaternary structure is responsible for repressing the kinase activity of both LuxQ subunits and triggering the transition of V. harveyi into quorum-sensing mode.

Neiditch,M.; Federle, M.; Pompeani, A.; Kelly, R.; Swem, D.; Jeffrey, P.; Bassler, B.; Hughson, F.

2006-01-01

250

The Small RNA Chaperone Hfq and Multiple Small RNAs Control Quorum Sensing in Vibrio harveyi and Vibrio cholerae  

Microsoft Academic Search

Quorum-sensing bacteria communicate with extracellular signal molecules called autoinducers. This process allows community-wide synchronization of gene expression. A screen for additional components of the Vibrio harveyi and Vibrio cholerae quorum-sensing circuits revealed the protein Hfq. Hfq mediates interactions between small, regulatory RNAs (sRNAs) and specific messenger RNA (mRNA) targets. These interactions typically alter the stability of the target transcripts. We

Derrick H. Lenz; Kenny C. Mok; Brendan N. Lilley; Rahul V. Kulkarni; Ned S. Wingreen; Bonnie L. Bassler

2004-01-01

251

Reciprocal regulation by the CepIR and CciIR quorum sensing systems in Burkholderia cenocepacia  

Microsoft Academic Search

BACKGROUND: Burkholderia cenocepacia belongs to a group of closely related organisms called the B. cepacia complex (Bcc) which are important opportunistic human pathogens. B. cenocepacia utilizes a mechanism of cell-cell communication called quorum sensing to control gene expression including genes involved in virulence. The B. cenocepacia quorum sensing network includes the CepIR and CciIR regulatory systems. RESULTS: Global gene expression

Eoin P O'Grady; Duber F Viteri; Rebecca J Malott; Pamela A Sokol

2009-01-01

252

The quorum-sensing system in a plant bacterium Mesorhizobium huakuii affects growth rate and symbiotic nodulation  

Microsoft Academic Search

Mesorhizobium huakuii is a free-living bacterium which is capable of establishing a specific symbiotic relationship with Astragalus sinicus, an important winter green manure widely used in Eastern Asia, allowing for nitrogen fixing during this process. Previous studies demonstrate that M.?huakuii produces quorum-sensing molecules at high cell density and quorum sensing plays a role in biofilm formations. In this study, we

Yijing Gao; Zengtao Zhong; Kejing Sun; Hui Wang; Jun Zhu

2006-01-01

253

The impact of quorum sensing on the virulence of Aeromonas hydrophila and Aeromonas salmonicida towards burbot (Lota lota L.) larvae  

Microsoft Academic Search

In this study, the link between quorum sensing in Aeromonas spp. and its virulence towards burbot (Lota lota) was investigated. High mortality occurred in burbot juveniles challenged with Aeromonas salmonicida HN-00, but not in juveniles challenged with Aeromonas hydrophila AH-1N. Meanwhile, both A. hydrophila AH-1N and A salmonicida HN-00 were virulent towards larvae. The effect of quorum sensing on the

F. M. I. Natrah; M. I. Alam; S. Pawar; A. S. Harzevili; N. Nevejan; N. Boon; P. Sorgeloos; P. Bossier; T. Defoirdt

2012-01-01

254

Role of Quorum Sensing and Antimicrobial Component Production by Serratia plymuthica in Formation of Biofilms, Including Mixed Biofilms with Escherichia coli  

Microsoft Academic Search

We have previously characterized the N-acyl-L-homoserine lactone-based quorum-sensing system of the biofilm isolate Serratia plymuthica RVH1. Here we investigated the role of quorum sensing and of quorum- sensing-dependent production of an antimicrobial compound (AC) on biofilm formation by RVH1 and on the cocultivation of RVH1 and Escherichia coli in planktonic cultures or in biofilms. Biofilm formation of S. plymuthica was

Pieter Moons; Rob Van Houdt; Abram Aertsen; Kristof Vanoirbeek; Yves Engelborghs; Chris W. Michiels

2006-01-01

255

A negative feedback loop involving small RNAs accelerates Vibrio cholerae’s transition out of quorum-sensing mode  

PubMed Central

Quorum sensing is a cell-to-cell communication process that allows bacteria to measure their population numbers and to synchronously alter gene expression in response to changes in cell population density. At the core of the Vibrio cholerae quorum-sensing signal transduction pathway lie four redundant small RNAs (sRNAs), named the Quorum Regulatory RNAs (Qrr1–4). Expression of qrr1–4 is cell population density-dependent due to a requirement for the quorum-sensing controlled phosphorylated response regulator LuxO-P, which is abundant only at low cell population density. When expressed, Qrr1–4 repress translation of HapR, the “master” quorum-sensing transcription factor. Here we show a negative feedback loop in which HapR activates transcription of the qrr genes, which indirectly leads to hapR repression. Efficient feedback activation of the qrr genes requires the simultaneous presence of LuxO-P (present only at low cell population density) and HapR (present only at high cell population density). For this reason, the feedback loop does not influence quorum sensing at steady-state low or high cell population density. However, LuxO-P and HapR are simultaneously present immediately following the switch from high to low cell density conditions. In this state, the HapR feedback loop dramatically accelerates V. cholerae’s transition from the high to the low cell density mode. PMID:18198339

Svenningsen, Sine L.; Waters, Christopher M.; Bassler, Bonnie L.

2008-01-01

256

The art of antibacterial warfare: Deception through interference with quorum sensing-mediated communication.  

PubMed

Almost a century on from the discovery of penicillin, the war against bacterial infection still rages compounded by the emergence of strains resistant to virtually every clinically approved antibiotic and the dearth of new antibacterial agents entering the clinic. Consequently there is renewed interest in drugs which attenuate virulence rather than bacterial growth. Since the metaphors of warfare are often used to describe the battle between pathogen and host, we will describe in such a context, the molecular communication (quorum sensing) mechanisms used by bacteria to co-ordinate virulence at the population level. Recent progress in exploiting this information through the design of anti-virulence deception strategies that disrupt quorum sensing through signal molecule inactivation, inhibition of signal molecule biosynthesis or the blockade of signal transduction and their advantages and disadvantages are considered. PMID:24823895

Rampioni, Giordano; Leoni, Livia; Williams, Paul

2014-08-01

257

Dynamical quorum-sensing in oscillators coupled through an external medium  

NASA Astrophysics Data System (ADS)

Many biological and physical systems exhibit population-density-dependent transitions to synchronized oscillations in a process often termed “dynamical quorum sensing”. Synchronization frequently arises through chemical communication via signaling molecules distributed through an external medium. We study a simple theoretical model for dynamical quorum sensing: a heterogenous population of limit-cycle oscillators diffusively coupled through a common medium. We show that this model exhibits a rich phase diagram with four qualitatively distinct physical mechanisms that can lead to a loss of coherent population-level oscillations, including a novel mechanism arising from effective time-delays introduced by the external medium. We derive a single pair of analytic equations that allow us to calculate phase boundaries as a function of population density and show that the model reproduces many of the qualitative features of recent experiments on Belousov-Zhabotinsky catalytic particles as well as synthetically engineered bacteria.

Schwab, David J.; Baetica, Ania; Mehta, Pankaj

2012-11-01

258

[Networks involving quorum sensing, cyclic-di-GMP and nitric oxide on biofilm production in bacteria].  

PubMed

Bacterial biofilms are ubiquitous in nature, and their flexibility is derived in part from a complex extracellular matrix that can be made-to-order to cope with environmental demand. Although common developmental stages leading to biofilm formation have been described, an in-depth knowledge of genetic and signaling is required to understand biofilm formation. Bacteria detect changes in population density by quorum sensing and particular environmental conditions, using signals such as cyclic di-GMP or nitric oxide. The significance of understanding these signaling pathways lies in that they control a broad variety of functions such as biofilm formation, and motility, providing benefits to bacteria as regards host colonization, defense against competitors, and adaptation to changing environments. Due to the importance of these features, we here review the signaling network and regulatory connections among quorum sensing, c-di-GMP and nitric oxide involving biofilm formation. PMID:25444134

Ramírez-Mata, Alberto; Fernández-Domínguez, Ileana J; Nuñez-Reza, Karen J; Xiqui-Vázquez, María L; Baca, Beatriz E

2014-01-01

259

Transcriptome analysis of quorum-sensing regulation and virulence factor expression in Pseudomonas aeruginosa  

Microsoft Academic Search

The opportunistic pathogen Pseudomonas aeruginosa possesses two well-studied quorum-sensing (QS) systems (las and rhl) that are important in the production of virulence factors, antibiotic sensitivity, and biofilm development. High-density oligonucleotide microarrays were used to further characterize the las QS system and to investigate the effect of environment (planktonic or biofilm mode of growth, absence or presence of oxygen) and nutritional

Victoria E. Wagner; Richard J. Gillis; Barbara H. Iglewski

2004-01-01

260

Efficient Synthesis and Evaluation of Quorum Sensing Modulators Using Small Molecule Macroarrays  

PubMed Central

A method for the synthesis of small molecule macroarrays of N-acylated L-homoserine lactones (AHLs) is reported. A focused library of AHLs was constructed, and the macroarray platform was found to be compatible with both solution and agar-overlay assays using quorum-sensing (QS) reporter strains. Several QS antagonists were discovered and serve to showcase the macroarray as a straightforward technique for QS research. PMID:19743816

Praneenararat, Thanit; Geske, Grant D.; Blackwell, Helen E.

2011-01-01

261

Presence of Quorum-sensing Systems Associated with Multidrug Resistance and Biofilm Formation in Bacteroides fragilis  

Microsoft Academic Search

Bacteroides fragilis constitutes 1–2% of the natural microbiota of the human digestive tract and is the predominant anaerobic opportunistic pathogen\\u000a in gastrointestinal infections. Most bacteria use quorum sensing (QS) to monitor cell density in relation to other cells and\\u000a their environment. In Gram-negative bacteria, the LuxRI system is common. The luxR gene encodes a transcriptional activator inducible by type I

Lilian Pumbwe; Christopher A. Skilbeck; Hannah M. Wexler

2008-01-01

262

Biofilms on Indwelling Urethral Catheters Produce Quorum Sensing Signal Molecules In Situ and In Vitro  

Microsoft Academic Search

Acylated homoserine lactones (AHLs) are chemical signals that mediate population density-dependent (quorum-sensing) gene expression in numerous gram-negative bacteria. In this study, gram-negative bacilli isolated from catheters were screened for AHL production by a cross-feeding assay utilizing an AHL-responsive Agrobacterium tumefaciens reporter strain. Positive reactions were obtained from 14 isolates of Pseudomonas aeruginosa; negative or weakly positive reactions were recorded for

DAVID J. STICKLER; NICOLA S. MORRIS; ROBERT J. C. MCLEAN; CLAY FUQUA

263

Crystal Structure of the Vibrio Cholerae Quorum-Sensing Regulatory Protein HapR  

Microsoft Academic Search

Quorum sensing in Vibrio cholerae involves signaling between two-component sensor protein kinases and the response regulator LuxO to control the expression of the master regulator HapR. HapR, in turn, plays a central role in regulating a number of important processes, such as virulence gene expression and biofilm formation. We have determined the crystal structure of HapR to 2.2- Angstroms resolution.

R. DeSilva; Gabriela Kovacikova; Wei Lin; Ronald K. Taylor; Karen Skorupski; F. Jon Kull

2007-01-01

264

Siamycin Attenuates fsr Quorum Sensing Mediated by a Gelatinase Biosynthesis-Activating Pheromone in Enterococcus faecalis  

Microsoft Academic Search

The expression of two Enterococcus faecalis virulence-related proteases, gelatinase (GelE) and serine protease (SprE), is positively regulated by a quorum-sensing system encoded by the fsr gene cluster. In this system, E. faecalis secretes an autoinducing peptide, gelatinase biosynthesis-activating pheromone (GBAP), which trig- gers the FsrC-FsrA two-component regulatory system controlling the expression of two transcripts, fsrBDC and gelE-sprE. In the present

Jiro Nakayama; Emi Tanaka; Reiko Kariyama; Koji Nagata; Kenzo Nishiguchi; Ritsuko Mitsuhata; Yumi Uemura; Masaru Tanokura; Hiromi Kumon; Kenji Sonomoto

2007-01-01

265

Quenching of acyl-homoserine lactone-dependent quorum sensing by enzymatic disruption of signal molecules  

Microsoft Academic Search

Many Gram-positive and Gram-negative bacteria communicate using small diffusible signal mol - ecules called autoinducers. This process, known as quorum sensing (QS), links cell density to the expression of genes as diverse as those associated with virulence factors production of plant and animal pathogens, bioluminescence, antibiotic production, sporulation or biofilm formation. In Gram-negative bacteria, this communication is mainly mediated by

Robert Czajkowski; Sylwia Jafra

2009-01-01

266

Pseudomonas aeruginosa activates the quorum sensing LuxR response regulator through secretion of 2-aminoacetophenone.  

PubMed

In this study we identify a volatile compound produced by Pseudomonas aeruginosa, which can specifically activate the LuxR quorum-sensing response regulator of Vibrio fischeri. Comparative gas-chromatography analysis between P. aeruginosa wild type and a ?lasR mutant strain implied that the active volatile is 2-aminoacetophenone. The use of synthetic 2-aminoacetophenone and in silico docking analyses verified the activity of the molecule and provided putative interacting residues within the binding site. PMID:25614099

Kviatkovski, I; Chernin, L; Yarnitzky, T; Frumin, I; Sobel, N; Helman, Y

2015-02-01

267

Regulation of Uptake and Processing of the Quorum-Sensing Autoinducer AI2 in Escherichia coli  

Microsoft Academic Search

AI-2 is a quorum-sensing signaling molecule proposed to be involved in interspecies communication. In Escherichia coli and Salmonella enterica serovar Typhimurium, extracellular AI-2 accumulates in exponential phase, but the amount decreases drastically upon entry into stationary phase. In S. enterica serovar Typhi- murium, the reduction in activity is due to import and processing of AI-2 by the Lsr transporter. We

Karina B. Xavier; Bonnie L. Bassler

2005-01-01

268

Quorum sensing as a population-density-dependent determinant of bacterial physiology  

Microsoft Academic Search

The discovery that bacterial cells can communicate with each other has led to the realization that bacteria are capable of exhibiting much more complex patterns of co-operative behaviour than would be expected for simple unicellular microorganisms. Now generically termed ‘quorum sensing’, bacterial cell-to-cell communication enables a bacterial population to mount a unified response that is advantageous to its survival by

Simon Swift; J. Allan Downie; Neil A. Whitehead; Anne M. L. Barnard; George P. C. Salmond; Paul Williams

2001-01-01

269

Quorum sensing as an integral component of gene regulatory networks in Gram-negative bacteria  

Microsoft Academic Search

Bacterial cell-to-cell communication (quorum sensing) relies upon the interaction of a small diffusible signal molecule with a sensor or transcriptional activator to couple gene expression with cell population density. In Gram-negative bacteria, it is now clear that N-acylhomoserine lactones bind directly to LuxR homologues and can be synthesized via one of three unrelated bacterial protein families and by transgenic plants.

Helen Withers; Simon Swift; Paul Williams

2001-01-01

270

Quorum Sensing Is a Global Regulatory Mechanism in Enterohemorrhagic Escherichia coli O157:H7  

Microsoft Academic Search

Enterohemorrhagic Escherichia coli (EHEC) O157:H7 is responsible for outbreaks of bloody diarrhea and hemolytic-uremic syndrome in many countries. EHEC virulence mechanisms include the production of Shiga toxins (Stx) and formation of attaching and effacing (AE) lesions on intestinal epithelial cells. We recently reported that genes involved in the formation of the AE lesion were regulated by quorum sensing through autoinducer-2,

VANESSA SPERANDIO; ALFREDO G. TORRES; JORGE A. GIRON; JAMES B. KAPER

2001-01-01

271

Salmonella typhimurium Recognizes a Chemically Distinct Form of the Bacterial Quorum-Sensing Signal AI2  

Microsoft Academic Search

Bacterial populations use cell-cell communication to coordinate community-wide regulation of processes such as biofilm formation, virulence, and bioluminescence. This phenomenon, termed quorum sensing, is mediated by small molecule signals known as autoinducers. While most autoinducers are species specific, autoinducer-2 (AI-2), first identified in the marine bacterium Vibrio harveyi, is produced and detected by many Gram-negative and Gram-positive bacteria. The crystal

Stephen T. Miller; Karina B. Xavier; Shawn R. Campagna; Michiko E. Taga; Martin F. Semmelhack; Bonnie L. Bassler; Frederick M. Hughson

2004-01-01

272

The Pseudomonas Quinolone Signal Regulates rhl Quorum Sensing in Pseudomonas aeruginosa  

Microsoft Academic Search

The opportunistic pathogen Pseudomonas aeruginosa uses intercellular signals to control the density-depen- dent expression of many virulence factors. The las and rhl quorum-sensing systems function, respectively, through the autoinducers N-(3-oxododecanoyl)-L-homoserine lactone and N-butyryl-L-homoserine lactone (C4- HSL), which are known to positively regulate the transcription of the elastase-encoding gene, lasB. Recently, we reported that a second type of intercellular signal is

SUSAN L. MCKNIGHT; BARBARA H. IGLEWSKI; EVERETT C. PESCI

2000-01-01

273

Quorum-Sensing Genes in Pseudomonas aeruginosa Biofilms: Their Role and Expression Patterns  

Microsoft Academic Search

Acylated homoserine lactone molecules are used by a number of gram-negative bacteria to regulate cell density-dependent gene expression by a mechanism known as quorum sensing (QS). In Pseudomonas aerugi- nosa, QS or cell-to-cell signaling controls expression of a number of virulence factors, as well as biofilm differentiation. In this study, we investigated the role played by the las and rhl

TERESA R. DE KIEVIT; RICHARD GILLIS; STEVE MARX; CHRIS BROWN; BARBARA H. IGLEWSKI

2001-01-01

274

Quorum Sensing in Burkholderia cepacia: Identification of the LuxRI Homologs CepRI  

Microsoft Academic Search

Burkholderia cepacia has emerged as an important pathogen in patients with cystic fibrosis. Many gram- negative pathogens regulate the production of extracellular virulence factors by a cell density-dependent mech- anism termed quorum sensing, which involves production of diffusible N-acylated homoserine lactone signal molecules, called autoinducers. Transposon insertion mutants of B. cepacia K56-2 which hyperproduced sidero- phores on chrome azurol S

SHAWN LEWENZA; BARBARA CONWAY; E. P. GREENBERG; PAMELA A. SOKOL

1999-01-01

275

Diversity of biofilms produced by quorum-sensing-deficient clinical isolates of Pseudomonas aeruginosa  

Microsoft Academic Search

The quorum-sensing (QS) systems control several virulence attributes of Pseudomonas aeruginosa. Five QS-deficient P. aeruginosa clinical isolates (CI) that were obtained from wound (CI-1), tracheal (CI-2, CI-3, CI-4) and urinary tract (CI-5) infections had previously been characterized. In this study, a flow-through continuous-culture system was utilized to examine in detail the biofilms formed by these isolates in comparison with the

J. Andy Schaber; Adrienne Hammond; Nancy L. Carty; Simon C. Williams; Jane A. Colmer-Hamood; Ben H. Burrowes; Vijian Dhevan; John A. Griswold; Abdul N. Hamood

2007-01-01

276

Therapeutic frontiers: preventing and treating infectious diseases by inhibiting bacterial quorum sensing  

Microsoft Academic Search

Density-dependent cell–cell communication, or quorum sensing (QS), has been demonstrated in numerous species of bacteria.\\u000a The basic function of QS is likely to confer a nutritional advantage, particularly in a highly populated, mixed-species environment.\\u000a QS also has ramifications on the production of colonization and virulence factors. Pheromone-like substances secreted into\\u000a the extracellular milieu appear to govern many of the transcription

C. A. Martin; A. D. Hoven; A. M. Cook

2008-01-01

277

Specificity and Genetic Polymorphism of the Bacillus Competence Quorum-Sensing System  

Microsoft Academic Search

A quorum-sensing mechanism involving the pheromone ComX and the ComP-ComA two-component system controls natural competence in Bacillus subtilis. ComX is expressed as a cytoplasmic inactive precursor that is released into the extracellular medium as a cleaved, modified decapeptide. This process requires the product of comQ. In the presence of ComX, the membrane-localized ComP histidine kinase activates the response regulator ComA.

P. Tortosa; L. Logsdon; B. Kraigher; Y. Itoh; I. Mandic-Mulec; D. Dubnau

2001-01-01

278

The Role of the CAI-1 Fatty Acid Tail in the Vibrio cholerae Quorum Sensing Response  

PubMed Central

Quorum sensing is a mechanism of chemical communication among bacteria that enables collective behaviors. In V. cholerae, the etiological agent of the disease cholera, quorum sensing controls group behaviors including virulence factor production and biofilm formation. The major V. cholerae quorum-sensing system consists of the extracellular signal molecule called CAI-1 and its cognate membrane bound receptor called CqsS. Here, the ligand binding activity of CqsS is probed with structural analogs of the natural signal. Enabled by our discovery of a structurally simplified analog of CAI-1, we prepared and analyzed a focused library. The molecules were designed to probe the effects of conformational and structural changes along the length of the fatty acid tail of CAI-1. Our results, combined with pharmacophore modeling, suggest a molecular basis for signal molecule recognition and receptor fidelity with respect to the fatty acid tail portion of CAI-1. These efforts provide novel probes to enhance discovery of anti-virulence agents for the treatment of V. cholerae. PMID:23092313

Perez, Lark J.; Ng, Wai-Leung; Marano, Paul; Brook, Karolina; Bassler, Bonnie L.; Semmelhack, Martin F.

2013-01-01

279

Three Parallel Quorum-Sensing Systems Regulate Gene Expression in Vibrio harveyi†  

PubMed Central

In a process called quorum sensing, bacteria communicate using extracellular signal molecules termed autoinducers. Two parallel quorum-sensing systems have been identified in the marine bacterium Vibrio harveyi. System 1 consists of the LuxM-dependent autoinducer HAI-1 and the HAI-1 sensor, LuxN. System 2 consists of the LuxS-dependent autoinducer AI-2 and the AI-2 detector, LuxPQ. The related bacterium, Vibrio cholerae, a human pathogen, possesses System 2 (LuxS, AI-2, and LuxPQ) but does not have obvious homologues of V. harveyi System 1. Rather, System 1 of V. cholerae is made up of the CqsA-dependent autoinducer CAI-1 and a sensor called CqsS. Using a V. cholerae CAI-1 reporter strain we show that many other marine bacteria, including V. harveyi, produce CAI-1 activity. Genetic analysis of V. harveyi reveals cqsA and cqsS, and phenotypic analysis of V. harveyi cqsA and cqsS mutants shows that these functions comprise a third V. harveyi quorum-sensing system that acts in parallel to Systems 1 and 2. Together these communication systems act as a three-way coincidence detector in the regulation of a variety of genes, including those responsible for bioluminescence, type III secretion, and metalloprotease production. PMID:15466044

Henke, Jennifer M.; Bassler, Bonnie L.

2004-01-01

280

Measurement of the Copy Number of the Master Quorum-Sensing Regulator of a Bacterial Cell  

NASA Astrophysics Data System (ADS)

Quorum sensing is the mechanism by which bacteria communicate and synchronize group behaviors. Quantitative information on parameters such as the copy number of particular quorum-sensing proteins should contribute strongly to understanding how the quorum-sensing network functions. Here we show that the copy number of the master regulator protein LuxR in Vibrio harveyi, can be determined in vivo by exploiting small-number fluctuations of the protein distribution when cells undergo division. When a cell divides, both its volume and LuxR protein copy number N are partitioned with slight asymmetries. We have measured the distribution functions describing the partitioning of the protein fluorescence and the cell volume. The fluorescence distribution is found to narrow systematically as the LuxR population increases while the volume partitioning is unchanged. Analyzing these changes statistically, we have determined that N = 80-135 dimers at low cell density and 575 dimers at high cell density. In addition, we have measured the static distribution of LuxR over a large (3,000) clonal population. Combining the static and time-lapse experiments, we determine the magnitude of the Fano factor of the distribution. This technique has broad applicability as a general, in vivo technique for measuring protein copy number and burst size.

Teng, Shu-Wen; Wang, Yufang; Tu, Kimberly C.; Long, Tao; Mehta, Pankaj; Wingreen, Ned S.; Bassler, Bonnie L.; Ong, N. P.

2010-05-01

281

AphA and LuxR/HapR reciprocally control quorum sensing in vibrios  

PubMed Central

Bacteria cycle between periods when they perform individual behaviors and periods when they perform group behaviors. These transitions are controlled by a cell–cell communication process called quorum sensing, in which extracellular signal molecules, called autoinducers (AIs), are released, accumulate, and are synchronously detected by a group of bacteria. AI detection results in community-wide changes in gene expression, enabling bacteria to collectively execute behaviors such as bioluminescence, biofilm formation, and virulence factor production. In this study, we show that the transcription factor AphA is a master regulator of quorum sensing that operates at low cell density (LCD) in Vibrio harveyi and Vibrio cholerae. In contrast, LuxR (V. harveyi)/HapR (V. cholerae) is the master regulator that operates at high cell density (HCD). At LCD, redundant small noncoding RNAs (sRNAs) activate production of AphA, and AphA and the sRNAs repress production of LuxR/HapR. Conversely, at HCD, LuxR/HapR represses aphA. This network architecture ensures maximal AphA production at LCD and maximal LuxR/HapR production at HCD. Microarray analyses reveal that 300 genes are regulated by AphA at LCD in V. harveyi, a subset of which is also controlled by LuxR. We propose that reciprocal gradients of AphA and LuxR/HapR establish the quorum-sensing LCD and HCD gene expression patterns, respectively. PMID:21325136

Rutherford, Steven T.; van Kessel, Julia C.; Shao, Yi; Bassler, Bonnie L.

2011-01-01

282

Bacillus globigii cell size is influenced by variants of the quorum sensing peptide extracellular death factor.  

PubMed

Toxin-antitoxin modules are necessary for the mode of action of several antibiotics. One of the most studied toxin-antitoxin modules is the quorum sensing-dependent MazEF system in Escherichia coli. The quorum sensing factor in this system is called the extracellular death factor (EDF), a linear pentapeptide with the sequence NNWNN. In spite of the extensive research on the mazEF system and the involvement of the quorum sensing factor EDF, the effect of EDF itself on bacteria has not yet been studied. In this research, we determined the effect of EDF and variants on cell growth in the Gram-negative bacterium E. coli and the Gram-positive Bacillus globigii. By aligning the zwf gene (from where EDF originates) of different bacterial species, we found 27 new theoretical variants of the peptide. By evaluating growth curves and light microscopy we found that three EDF variants reduced bacterial cell size in B. globigii, but not in E. coli. The D-peptides did not affect cell size, indicating that the effect is stereospecific. Peptides wherein tryptophan was substituted by alanine also did not affect cell size, which indicates that the effect seen is mediated by an intracellular target. PMID:24198119

Sijbrandij, T; Kaman, W E; Ligtenberg, A J M; Nazmi, K; Veerman, E C I; Bikker, F J

2014-01-01

283

New Life for an Old Drug: the Anthelmintic Drug Niclosamide Inhibits Pseudomonas aeruginosa Quorum Sensing  

PubMed Central

The need for novel antibacterial strategies and the awareness of the importance of quorum sensing (QS) in bacterial infections have stimulated research aimed at identifying QS inhibitors (QSIs). However, clinical application of QSIs identified so far is still distant, likely due to their unsuitability for use in humans. A promising way to overcome this problem is searching for anti-QS side activity among the thousands of drugs approved for clinical use in the treatment of different diseases. Here, we applied this strategy to the search for QSIs, by screening a library of FDA-approved compounds for their ability to inhibit the QS response in the Gram-negative pathogen Pseudomonas aeruginosa. We found that the anthelmintic drug niclosamide strongly inhibits the P. aeruginosa QS response and production of acyl-homoserine lactone QS signal molecules. Microarray analysis showed that niclosamide affects the transcription of about 250 genes, with a high degree of target specificity toward the QS-dependent regulon. Phenotypic assays demonstrated that niclosamide suppresses surface motility and production of the secreted virulence factors elastase, pyocyanin, and rhamnolipids, and it reduces biofilm formation. In accordance with the strong antivirulence activity disclosed in vitro, niclosamide prevented P. aeruginosa pathogenicity in an insect model of acute infection. Besides the finding that an FDA-approved drug has a promising antivirulence activity against one of the most antibiotic-resistant bacterial pathogens, this work provides a proof of concept that a lateral anti-QS activity can be detected among drugs already used in humans, validating a new approach to identify QSIs that could easily move into clinical applications. PMID:23254430

Imperi, Francesco; Massai, Francesco; Ramachandran Pillai, Cejoice; Longo, Francesca; Zennaro, Elisabetta; Rampioni, Giordano; Visca, Paolo

2013-01-01

284

Chlamydomonas reinhardtii Secretes Compounds That Mimic Bacterial Signals and Interfere with Quorum Sensing Regulation in Bacteria1  

Microsoft Academic Search

The unicellular soil-freshwater alga Chlamydomonas reinhardtii was found to secrete substances that mimic the activity of the N-acyl-l-homoserine lactone (AHL) signal molecules used by many bacteria for quorum sensing regulation of gene expression. More than a dozen chemically separable but unidentified substances capable of specifically stimulating the LasR or CepR but not the LuxR, AhyR, or CviR AHL bacterial quorum

Max Teplitski; Hancai Chen; Sathish Rajamani; Mengsheng Gao; Massimo Merighi; Richard T. Sayre; Jayne B. Robinson; Barry G. Rolfe; Wolfgang D. Bauer

2004-01-01

285

Heterogeneous Response to a Quorum-Sensing Signal in the Luminescence of Individual Vibrio fischeri  

PubMed Central

The marine bacterium Vibrio fischeri regulates its bioluminescence through a quorum sensing mechanism: the bacterium releases diffusible small molecules (autoinducers) that accumulate in the environment as the population density increases. This accumulation of autoinducer (AI) eventually activates transcriptional regulators for bioluminescence as well as host colonization behaviors. Although V.fischeri quorum sensing has been extensively characterized in bulk populations, far less is known about how it performs at the level of the individual cell, where biochemical noise is likely to limit the precision of luminescence regulation. We have measured the time-dependence and AI-dependence of light production by individual V.fischeri cells that are immobilized in a perfusion chamber and supplied with a defined concentration of exogenous AI. We use low-light level microscopy to record and quantify the photon emission from the cells over periods of several hours as they respond to the introduction of AI. We observe an extremely heterogeneous response to the AI signal. Individual cells differ widely in the onset time for their luminescence and in their resulting brightness, even in the presence of high AI concentrations that saturate the light output from a bulk population. The observed heterogeneity shows that although a given concentration of quorum signal may determine the average light output from a population of cells, it provides far weaker control over the luminescence output of each individual cell. PMID:21103327

Pérez, Pablo Delfino; Hagen, Stephen J.

2010-01-01

286

Reciprocal regulation by the CepIR and CciIR quorum sensing systems in Burkholderia cenocepacia  

PubMed Central

Background Burkholderia cenocepacia belongs to a group of closely related organisms called the B. cepacia complex (Bcc) which are important opportunistic human pathogens. B. cenocepacia utilizes a mechanism of cell-cell communication called quorum sensing to control gene expression including genes involved in virulence. The B. cenocepacia quorum sensing network includes the CepIR and CciIR regulatory systems. Results Global gene expression profiles during growth in stationary phase were generated using microarrays of B. cenocepacia cepR, cciR and cepRcciIR mutants. This is the first time CciR was shown to be a global regulator of quorum sensing gene expression. CepR was primarily responsible for positive regulation of gene expression while CciR generally exerted negative gene regulation. Many of the genes that were regulated by both quorum sensing systems were reciprocally regulated by CepR and CciR. Microarray analysis of the cepRcciIR mutant suggested that CepR is positioned upstream of CciR in the quorum sensing hierarchy in B. cenocepacia. A comparison of CepIR-regulated genes identified in previous studies and in the current study showed a substantial amount of overlap validating the microarray approach. Several novel quorum sensing-controlled genes were confirmed using qRT-PCR or promoter::lux fusions. CepR and CciR inversely regulated flagellar-associated genes, the nematocidal protein AidA and a large gene cluster on Chromosome 3. CepR and CciR also regulated genes required for iron transport, synthesis of extracellular enzymes and surface appendages, resistance to oxidative stress, and phage-related genes. Conclusion For the first time, the influence of CciIR on global gene regulation in B. cenocepacia has been elucidated. Novel genes under the control of the CepIR and CciIR quorum sensing systems in B. cenocepacia have been identified. The two quorum sensing systems exert reciprocal regulation of many genes likely enabling fine-tuned control of quorum sensing gene expression in B. cenocepacia strains carrying the cenocepacia island. PMID:19761612

O'Grady, Eoin P; Viteri, Duber F; Malott, Rebecca J; Sokol, Pamela A

2009-01-01

287

Allele-Dependent Differences in Quorum-Sensing Dynamics Result in Variant Expression of Virulence Genes in Staphylococcus aureus  

PubMed Central

Agr is an autoinducing, quorum-sensing system that functions in many Gram-positive species and is best characterized in the pathogen Staphylococcus aureus, in which it is a global regulator of virulence gene expression. Allelic variations in the agr genes have resulted in the emergence of four quorum-sensing specificity groups in S. aureus, which correlate with different strain pathotypes. The basis for these predilections is unclear but is hypothesized to involve the phenomenon of quorum-sensing interference between strains of different agr groups, which may drive S. aureus strain isolation and divergence. Whether properties intrinsic to each agr allele directly influence virulence phenotypes within S. aureus is unknown. In this study, we examined group-specific differences in agr autoinduction and virulence gene regulation by utilizing congenic strains, each harboring a unique S. aureus agr allele, enabling a dissection of agr locus-dependent versus genotype-dependent effects on quorum-sensing dynamics and virulence factor production. Employing a reporter fusion to the principal agr promoter, P3, we observed allele-dependent differences in the timing and magnitude of agr activation. These differences were mediated by polymorphisms within the agrBDCA genes and translated to significant variations in the expression of a key transcriptional regulator, Rot, and of several important exoproteins and surface factors involved in pathogenesis. This work uncovers the contribution of divergent quorum-sensing alleles to variant expression of virulence determinants within a bacterial species. PMID:22467783

Geisinger, Edward; Chen, John

2012-01-01

288

Functional determinants of the quorum-sensing non-coding RNAs and their roles in target regulation.  

PubMed

Quorum sensing is a chemical communication process that bacteria use to control collective behaviours including bioluminescence, biofilm formation, and virulence factor production. In Vibrio harveyi, five homologous small RNAs (sRNAs) called Qrr1-5, control quorum-sensing transitions. Here, we identify 16 new targets of the Qrr sRNAs. Mutagenesis reveals that particular sequence differences among the Qrr sRNAs determine their target specificities. Modelling coupled with biochemical and genetic analyses show that all five of the Qrr sRNAs possess four stem-loops: the first stem-loop is crucial for base pairing with a subset of targets. This stem-loop also protects the Qrr sRNAs from RNase E-mediated degradation. The second stem-loop contains conserved sequences required for base pairing with the majority of the target mRNAs. The third stem-loop plays an accessory role in base pairing and stability. The fourth stem-loop functions as a rho-independent terminator. In the quorum-sensing regulon, Qrr sRNAs-controlled genes are the most rapid to respond to quorum-sensing autoinducers. The Qrr sRNAs are conserved throughout vibrios, thus insights from this work could apply generally to Vibrio quorum sensing. PMID:23838640

Shao, Yi; Feng, Lihui; Rutherford, Steven T; Papenfort, Kai; Bassler, Bonnie L

2013-07-31

289

Inhibition of Biofilm Formation, Quorum Sensing and Infection in Pseudomonas aeruginosa by Natural Products-Inspired Organosulfur Compounds  

PubMed Central

Using a microplate-based screening assay, the effects on Pseudomonas aeruginosa PAO1 biofilm formation of several S-substituted cysteine sulfoxides and their corresponding disulfide derivatives were evaluated. From our library of compounds, S-phenyl-L-cysteine sulfoxide and its breakdown product, diphenyl disulfide, significantly reduced the amount of biofilm formation by P. aeruginosa at levels equivalent to the active concentration of 4-nitropyridine-N-oxide (NPO) (1 mM). Unlike NPO, which is an established inhibitor of bacterial biofilms, our active compounds did not reduce planktonic cell growth and only affected biofilm formation. When used in a Drosophila-based infection model, both S-phenyl-L-cysteine sulfoxide and diphenyl disulfide significantly reduced the P. aeruginosa recovered 18 h post infection (relative to the control), and were non-lethal to the fly hosts. The possibility that the observed biofilm inhibitory effects were related to quorum sensing inhibition (QSI) was investigated using Escherichia coli-based reporters expressing P. aeruginosa lasR or rhIR response proteins, as well as an endogenous P. aeruginosa reporter from the lasI/lasR QS system. Inhibition of quorum sensing by S-phenyl-L-cysteine sulfoxide was observed in all of the reporter systems tested, whereas diphenyl disulfide did not exhibit QSI in either of the E. coli reporters, and showed very limited inhibition in the P. aeruginosa reporter. Since both compounds inhibit biofilm formation but do not show similar QSI activity, it is concluded that they may be functioning by different pathways. The hypothesis that biofilm inhibition by the two active compounds discovered in this work occurs through QSI is discussed. PMID:22715388

Cady, Nathaniel C.; McKean, Kurt A.; Behnke, Jason; Kubec, Roman; Mosier, Aaron P.; Kasper, Stephen H.; Burz, David S.; Musah, Rabi A.

2012-01-01

290

A Quorum-Quenching Approach To Investigate the Conservation of Quorum-Sensing-Regulated Functions within the Burkholderia cepacia Complex  

PubMed Central

Taxonomic studies of the past few years have shown that the Burkholderia cepacia complex, a heterogeneous group of B. cepacia-like organisms, consists of at least nine species. B. cepacia complex strains are ubiquitously distributed in nature and have been used for biocontrol, bioremediation, and plant growth promotion purposes. At the same time, B. cepacia complex strains have emerged as important opportunistic pathogens of humans, particularly those with cystic fibrosis. All B. cepacia complex species investigated thus far use quorum-sensing (QS) systems that rely on N-acylhomoserine lactone (AHL) signal molecules to express certain functions, including the production of extracellular proteases, swarming motility, biofilm formation, and pathogenicity, in a population-density-dependent manner. In this study we constructed a broad-host-range plasmid that allowed the heterologous expression of the Bacillus sp. strain 240B1 AiiA lactonase, which hydrolyzes the lactone ring of various AHL signal molecules, in all described B. cepacia complex species. We show that expression of AiiA abolished or greatly reduced the accumulation of AHL molecules in the culture supernatants of all tested B. cepacia complex strains. Phenotypic characterization of wild-type and transgenic strains revealed that protease production, swarming motility, biofilm formation, and Caenorhabditis elegans killing efficiency was regulated by AHL in the large majority of strains investigated. PMID:16461713

Wopperer, Julia; Cardona, Silvia T.; Huber, Birgit; Jacobi, Christoph A.; Valvano, Miguel A.; Eberl, Leo

2006-01-01

291

19/07/2012 16:21Density-dependent fitness benefits in quorum-sensing bacterial populations. -F1000 Page 1 of 2http://f1000.com/715297923  

E-print Network

19/07/2012 16:21Density-dependent fitness benefits in quorum-sensing bacterial populations. - F1000 Density-dependent fitness benefits in quorum-sensing bacterial populations. Darch SE, West SA, Winzer K that bacterial quorum-sensing is indeed beneficial to bacteria at high cell densities, a common wisdom statement

West, Stuart

292

20/11/2007 18:16Faculty of 1000 Biology | Cooperation and conflict in quorum-sensing bacterial populations. Page 1 of 2http://www.f1000biology.com/article/id/1095043  

E-print Network

20/11/2007 18:16Faculty of 1000 Biology | Cooperation and conflict in quorum-sensing bacterial Member List Must Read F1000 Factor 6.0 EndNote Cooperation and conflict in quorum-sensing bacterial article of importance to the study of quorum sensing (QS) in bacterial populations, particularly those

West, Stuart

293

Current Biology 19, 341345, February 24, 2009 2009 Elsevier Ltd All rights reserved DOI 10.1016/j.cub.2009.01.050 Quorum Sensing and the Social Evolution  

E-print Network

.cub.2009.01.050 Report Quorum Sensing and the Social Evolution of Bacterial Virulence Kendra P. Rumbaugh,1 cooperative behaviors and that this process of quorum sensing (QS) can be exploited by indi- vidual cells show that in mixed infections of the bacterium Pseudo- monas aeruginosa, containing quorum-sensing

West, Stuart

294

Testing the level of ant activity associated with quorum sensing: An empirical approach leading to the establishment and test of a null-model  

E-print Network

Testing the level of ant activity associated with quorum sensing: An empirical approach leading density, in the light organs of some marine fish and squid. This mechanism was first called `quorum sensing' by Fuqua et al. (1994). It has subsequently emerged that bacteria ubiquitously use both intra

Waxman, David

295

The LuxR Homolog ExpR, in Combination with the Sin Quorum Sensing System, Plays a Central Role in Sinorhizobium meliloti Gene Expression  

Microsoft Academic Search

Quorum sensing, a population density-dependent mechanism for bacterial communication and gene regu- lation, plays a crucial role in the symbiosis between alfalfa and its symbiont Sinorhizobium meliloti. The Sin system, one of three quorum sensing systems present in S. meliloti, controls the production of the symbiotically active exopolysaccharide EPS II. Based on DNA microarray data, the Sin system also seems

Hanh H. Hoang; Anke Becker; Juan E. Gonzalez

2004-01-01

296

Quorum Sensing Inhibition by Asparagopsis taxiformis, a Marine Macro Alga: Separation of the Compound that Interrupts Bacterial Communication  

PubMed Central

The majority of the marine algal species, though completing their life cycle in seawater, are rarely susceptible to fouling, making them an important source of quorum sensing (QS) inhibitory substances. The separation and characterization of QS inhibitors are crucial for any potential application. Thirty marine macroalgae were tested for QS inhibition activity by using Chromobacterium violaceum CV026 as the reporter strain, and among them, Asparagopsis taxiformis showed antibacterial, as well as antiquorum, sensing activities. Cinnamaldehyde (75 mM) and methanol were used as positive and negative controls, respectively. The antiquorum sensing activity of A. taxiformis was further confirmed using the sensor strain, Serratia liquefaciens MG44, having green fluorescent protein (gfp). Methanolic extract of the alga was fractionated by solid phase extraction (SPE), and each fraction was tested for QS inhibition. Two types of activities were observed—zone of clearance (antibacterial activity) and zone of inhibition with or without finger-like projections (QS inhibition). Out of five SPE cartridges, Bond Elut PH showed clear separation of these two fractions. The Ion Cyclotron Resonance Fourier Transformation Mass Spectrometer (ICR-FT/MS) analysis of the fractions further supported the bioassay results. The presence of strong QS inhibitory compound in A. taxiformis indicates its potential use in antifouling preparations. PMID:23344114

Jha, Bhavanath; Kavita, Kumari; Westphal, Jenny; Hartmann, Anton; Schmitt-Kopplin, Philippe

2013-01-01

297

Quorum sensing inhibition by Asparagopsis taxiformis, a marine macro alga: separation of the compound that interrupts bacterial communication.  

PubMed

The majority of the marine algal species, though completing their life cycle in seawater, are rarely susceptible to fouling, making them an important source of quorum sensing (QS) inhibitory substances. The separation and characterization of QS inhibitors are crucial for any potential application. Thirty marine macroalgae were tested for QS inhibition activity by using Chromobacterium violaceum CV026 as the reporter strain, and among them, Asparagopsis taxiformis showed antibacterial, as well as antiquorum, sensing activities. Cinnamaldehyde (75 mM) and methanol were used as positive and negative controls, respectively. The antiquorum sensing activity of A. taxiformis was further confirmed using the sensor strain, Serratia liquefaciens MG44, having green fluorescent protein (gfp). Methanolic extract of the alga was fractionated by solid phase extraction (SPE), and each fraction was tested for QS inhibition. Two types of activities were observed-zone of clearance (antibacterial activity) and zone of inhibition with or without finger-like projections (QS inhibition). Out of five SPE cartridges, Bond Elut PH showed clear separation of these two fractions. The Ion Cyclotron Resonance Fourier Transformation Mass Spectrometer (ICR-FT/MS) analysis of the fractions further supported the bioassay results. The presence of strong QS inhibitory compound in A. taxiformis indicates its potential use in antifouling preparations. PMID:23344114

Jha, Bhavanath; Kavita, Kumari; Westphal, Jenny; Hartmann, Anton; Schmitt-Kopplin, Philippe

2013-01-01

298

Prevention of bacterial quorum sensing in aquifer materials and effect on bioclogging  

NASA Astrophysics Data System (ADS)

In aquifer materials that are clogged as a result of the growth and metabolism of bacteria, microscopic observations usually show the bacterial cells to be present in aggregates that tend to be strategically located at constrictions in the pore space, either strained there, or accumulating at these spots for metabolic advantages. Aggregation appears to be fostered by exopolymer production, but can also occur purely as a result of electrostatic interactions. On membranes, research has shown that if bacteria are discouraged from aggregating, for example by eliminating the biochemical means (e.g., "quorum sensing") by which they communicate in order to do so, biofouling of the membranes is significantly delayed and in some cases even largely alleviated. In this context, the goal of the research described in this presentation was to determine if a similar situation might arise when quorum quenchers are added to the liquid injected in columns of fine sand inoculated with various bacterial strains. Traditional saturated hydraulic conductivity and piezometer measurements asre complemented with detailed microscopic observations in the pore space. Perspectives on the possible use of quorum quenchers in practical situations is discussed.

Baveye, P.; Superak, C.; Farris, K.

2012-12-01

299

Quorum Sensing Signal Synthesis May Represent a Selective Advantage Independent of Its Role in Regulation of Bioluminescence in Vibrio fischeri.  

PubMed

The evolution of biological signalling systems and apparently altruistic or cooperative traits in diverse organisms has required selection against the subversive tendencies of self-interested biological entities. The bacterial signalling and response system known as quorum sensing or Acylated Homoserine Lactone (AHL) mediated gene expression is thought to have evolved through kin selection. In this in vitro study on the model quorum sensing bioluminescent marine symbiont Vibrio fischeri, competition and long-term sub culturing experiments suggest that selection for AHL synthesis (encoded by the AHL synthase gene luxI) is independent of the quorum sensing regulated phenotype (bioluminescence encoded by luxCDABE). Whilst results support the hypothesis that signal response (AHL binding and transcriptional activation encoded by the luxR gene) is maintained through indirect fitness benefits (kin selection), signal synthesis is maintained in the V. fischeri genome over evolutionary time through direct fitness benefits at the individual level from an unknown function. PMID:23825662

Chong, Grace; Kimyon, Onder; Manefield, Mike

2013-01-01

300

Modulation of quorum sensing controlled behaviour of bacteria by growing seedling, seed and seedling extracts of leguminous plants.  

PubMed

Effect of growing seedling, seeds and seedlings extracts from seven leguminous plants (Pisum sativum, Vigna radiata, Vigna mungo, Cajanus cajan, Lentil culinaris, Cicer arietinum and Trigonella foenum graecum) were screened for their ability to influence quorum sensing controlled pigment production in Chromobacterium violaceum indicator strains (CV12472 and CVO26). Germinating seedling and seedling extracts of only P. sativum (pea) showed inhibition of violacein production. Interestingly, the T. foenum graecum (fenugreek) seed extracts enhances the pigment production. Quorum sensing regulated swarming motility in Pseudomonas aerugionsa PAO1 was reduced by pea seedling extract while enhanced by the fenugreek seed extracts. These findings suggest that plant metabolites of some legumes interact actively with bacterial quorum sensing and could modulate its associated functions. PMID:23100836

Fatima, Qaseem; Zahin, Maryam; Khan, Mohd Sajjad Ahmad; Ahmad, Iqbal

2010-06-01

301

Letter to Editor Testing the level of ant activity associated with quorum sensing: An empirical approach leading to the establishment and test of a  

E-print Network

Letter to Editor Testing the level of ant activity associated with quorum sensing: An empirical was not allowed in our experiments, the resulting data were not homogeneous in time.1 In this sense it shares

Waxman, David

302

The regulation of virulence in phytopathogenic Erwinia species: quorum sensing, antibiotics and ecological considerations.  

PubMed

Erwinia carotovora is a Gram-negative bacterial phytopathogen that causes soft-rot disease and potato blackleg. The organism is environmentally widespread and exhibits an opportunistic plant pathogenesis. The ability to secrete multiple plant cell wall-degrading enzymes is a key virulence trait and exoenzyme production is responsive to multiple environmental and physiological cues. One important cue is the cell population density of the pathogen. Cell density is monitored via an acylated homoserine lactone (acyl HSL) signalling molecule, which is thought to diffuse between Erwinia cells in a process now commonly known as 'quorum sensing'. This molecule also acts as the chemical communication signal controlling production of a broad-spectrum beta-lactam antibiotic (1-carbapen-2-em-3-carboxylic acid; carbapenem) synthesised in concert with exoenzyme elaboration, possibly for niche defence. In antibiotic production control, quorum sensing acts at the level of transcriptional activation of the antibiotic biosynthetic cluster. This is achieved via a dedicated LuxR-type protein, CarR that is bound to the signalling molecule. The molecular relay connecting acyl HSL production and exoenzyme induction is not clear, despite the identification of a multitude of global regulatory genes, including those of the RsmA/rsmB system, impinging on enzyme synthesis. Quorum sensing control mediated by acyl HSLs is widespread in Gram-negative bacteria and is responsible for the regulation of diverse phenotypes. Although there is still a paucity of meaningful information on acyl HSL availability and in-situ biological function, there is growing evidence that such molecules play significant roles in microbial ecology. PMID:12448721

Whitehead, Neil A; Byers, Joseph T; Commander, Paul; Corbett, Mark J; Coulthurst, Sarah J; Everson, Lee; Harris, Abigail K P; Pemberton, Clare L; Simpson, Natalie J L; Slater, Holly; Smith, Debra S; Welch, Martin; Williamson, Neil; Salmond, George P C

2002-08-01

303

From deep-sea volcanoes to human pathogens: a conserved quorum-sensing signal in Epsilonproteobacteria.  

PubMed

Chemosynthetic Epsilonproteobacteria from deep-sea hydrothermal vents colonize substrates exposed to steep thermal and redox gradients. In many bacteria, substrate attachment, biofilm formation, expression of virulence genes and host colonization are partly controlled via a cell density-dependent mechanism involving signal molecules, known as quorum sensing. Within the Epsilonproteobacteria, quorum sensing has been investigated only in human pathogens that use the luxS/autoinducer-2 (AI-2) mechanism to control the expression of some of these functions. In this study we showed that luxS is conserved in Epsilonproteobacteria and that pathogenic and mesophilic members of this class inherited this gene from a thermophilic ancestor. Furthermore, we provide evidence that the luxS gene is expressed-and a quorum-sensing signal is produced-during growth of Sulfurovum lithotrophicum and Caminibacter mediatlanticus, two Epsilonproteobacteria from deep-sea hydrothermal vents. Finally, we detected luxS transcripts in Epsilonproteobacteria-dominated biofilm communities collected from deep-sea hydrothermal vents. Taken together, our findings indicate that the epsiloproteobacterial lineage of the LuxS enzyme originated in high-temperature geothermal environments and that, in vent Epsilonproteobacteria, luxS expression is linked to the production of AI-2 signals, which are likely produced in situ at deep-sea vents. We conclude that the luxS gene is part of the ancestral epsilonproteobacterial genome and represents an evolutionary link that connects thermophiles to human pathogens.The ISME Journal advance online publication, 14 November 2014; doi:10.1038/ismej.2014.214. PMID:25397946

Pérez-Rodríguez, Ileana; Bolognini, Marie; Ricci, Jessica; Bini, Elisabetta; Vetriani, Costantino

2014-11-14

304

Quorumpeps database: chemical space, microbial origin and functionality of quorum sensing peptides.  

PubMed

Quorum-sensing (QS) peptides are biologically attractive molecules, with a wide diversity of structures and prone to modifications altering or presenting new functionalities. Therefore, the Quorumpeps database (http://quorumpeps.ugent.be) is developed to give a structured overview of the QS oligopeptides, describing their microbial origin (species), functionality (method, result and receptor), peptide links and chemical characteristics (3D-structure-derived physicochemical properties). The chemical diversity observed within this group of QS signalling molecules can be used to develop new synthetic bio-active compounds. PMID:23180797

Wynendaele, Evelien; Bronselaer, Antoon; Nielandt, Joachim; D'Hondt, Matthias; Stalmans, Sofie; Bracke, Nathalie; Verbeke, Frederick; Van De Wiele, Christophe; De Tré, Guy; De Spiegeleer, Bart

2013-01-01

305

Quorumpeps database: chemical space, microbial origin and functionality of quorum sensing peptides  

PubMed Central

Quorum-sensing (QS) peptides are biologically attractive molecules, with a wide diversity of structures and prone to modifications altering or presenting new functionalities. Therefore, the Quorumpeps database (http://quorumpeps.ugent.be) is developed to give a structured overview of the QS oligopeptides, describing their microbial origin (species), functionality (method, result and receptor), peptide links and chemical characteristics (3D-structure-derived physicochemical properties). The chemical diversity observed within this group of QS signalling molecules can be used to develop new synthetic bio-active compounds. PMID:23180797

Wynendaele, Evelien; Bronselaer, Antoon; Nielandt, Joachim; D’Hondt, Matthias; Stalmans, Sofie; Bracke, Nathalie; Verbeke, Frederick; Van De Wiele, Christophe; De Tré, Guy; De Spiegeleer, Bart

2013-01-01

306

Engineering quorum sensing signaling of Pseudomonas for enhanced wastewater treatment and electricity harvest: A review.  

PubMed

Cell-cell communication that enables synchronized population behaviors in microbial communities dictates various biological processes. It is of great interest to unveil the underlying mechanisms of fine-tuning cell-cell communication to achieve environmental and energy applications. Pseudomonas is a ubiquitous microbe in environments that had wide applications in bioremediation and bioenergy generation. The quorum sensing (QS, a generic cell-cell communication mechanism) systems of Pseudomonas underlie the aromatics biodegradation, denitrification and electricity harvest. Here, we reviewed the recent progresses of the genetic strategies in engineering QS circuits to improve efficiency of wastewater treatment and the performance of microbial fuel cells. PMID:25455678

Yong, Yang-Chun; Wu, Xiang-Yang; Sun, Jian-Zhong; Cao, Ying-Xiu; Song, Hao

2014-11-13

307

Dynamical quorum sensing and synchronization in collections of excitable and oscillatory catalytic particles  

NASA Astrophysics Data System (ADS)

We present experimental studies of interacting excitable and oscillatory catalytic particles in well-stirred and spatially distributed systems. A number of distinct paths to synchronized oscillatory behavior are described. We present an example of a Kuramoto type transition in a well-stirred system with a collective rhythm emerging on increasing the number density of oscillatory particles. Groups of spatially distributed oscillatory particles become entrained to a common frequency by organizing centers. Quorum sensing type transitions are found in populations of globally and locally coupled excitable particles, with a sharp transition from steady state to fully synchronized behavior at a critical density or group size.

Tinsley, M. R.; Taylor, A. F.; Huang, Z.; Wang, F.; Showalter, K.

2010-06-01

308

Realization of Morphing Logic Gates in a Repressilator with Quorum Sensing Feedback  

E-print Network

We demonstrate how a genetic ring oscillator network with quorum sensing feedback can operate as a robust logic gate. Specifically we show how a range of logic functions, namely AND/NAND, OR/NOR and XOR/XNOR, can be realized by the system, thus yielding a versatile unit that can morph between different logic operations. We further demonstrate the capacity of this system to yield complementary logic operations in parallel. Our results then indicate the computing potential of this biological system, and may lead to bio-inspired computing devices.

Agrawal, Vidit; Sinha, Sudeshna

2013-01-01

309

Analysis of a bacteria-immunity model with delay quorum sensing  

NASA Astrophysics Data System (ADS)

A bacteria-immunity model with bacterial quorum sensing is formulated, which describes the competition between bacteria and immune cells. A distributed delay is introduced to characterize the time in which bacteria receive signal molecules and then combat with immune cells. In this paper, we focus on a subsystem of the bacteria-immunity model, analyze the stability of the equilibrium points, discuss the existence and stability of periodic solutions bifurcated from the positive equilibrium point, and finally investigate the stability of the nonhyperbolic equilibrium point by the center manifold theorem.

Zhang, Zhonghua; Peng, Jigen; Zhang, Juan

2008-04-01

310

Identification of a New Regulator in Streptococcus pneumoniae Linking Quorum Sensing to Competence for Genetic Transformation  

Microsoft Academic Search

Competence for genetic transformation in Streptococcus pneumoniae is regulated by a quorum-sensing system encoded by two genetic loci, comCDE and comAB. Additional competence-specific operons, cilA, cilB, cilC, cilD, cilE, cinA-recA, coiA, and cfl, involved in the DNA uptake process and recombination, share an unusual consensus sequence at 210 and 225 in the promoter, which is absent from the promoters of

MYEONG S. LEE; DONALD A. MORRISON

1999-01-01

311

Realization of morphing logic gates in a repressilator with quorum sensing feedback  

NASA Astrophysics Data System (ADS)

We demonstrate how a genetic ring oscillator network with quorum sensing feedback can operate as a robust logic gate. Specifically we show how a range of logic functions, namely AND/NAND, OR/NOR and XOR/XNOR, can be realized by the system, thus yielding a versatile unit that can morph between different logic operations. We further demonstrate the capacity of this system to yield complementary logic operations in parallel. Our results then indicate the computing potential of this biological system, and may lead to bio-inspired computing devices.

Agrawal, Vidit; Kang, Shivpal Singh; Sinha, Sudeshna

2014-03-01

312

Human and murine paraoxonase 1 are host modulators of Pseudomonas aeruginosa quorum-sensing  

Microsoft Academic Search

The pathogenic bacterium Pseudomonas aeruginosa uses acyl-HSL quorum-sensing signals to regulate genes controlling virulence and biofilm formation. We found that paraoxonase 1 (PON1), a mammalian lactonase with an unknown natural substrate, hydrolyzed the P. aeruginosa acyl-HSL 3OC12-HSL. In in vitro assays, mouse serum-PON1 was required and sufficient to degrade 3OC12-HSL. Furthermore, PON2 and PON3 also degraded 3OC12-HSL effectively. Serum-PON1 prevented

Egon A. Ozer; Alejandro Pezzulo; Diana M. Shih; Carlene Chun; Clement Furlong; Aldons J. Lusis; Everett P. Greenberg; Joseph Zabner

2005-01-01

313

A mathematical model of quorum sensing regulated EPS production in biofilm communities  

Microsoft Academic Search

Background  Biofilms are microbial communities encased in a layer of extracellular polymeric substances (EPS). The EPS matrix provides\\u000a several functional purposes for the biofilm, such as protecting bacteria from environmental stresses, and providing mechanical\\u000a stability. Quorum sensing is a cell-cell communication mechanism used by several bacterial taxa to coordinate gene expression\\u000a and behaviour in groups, based on population densities.\\u000a \\u000a \\u000a \\u000a \\u000a Model  We mathematically

Mallory R Frederick; Christina Kuttler; Burkhard A Hense; Hermann J Eberl

2011-01-01

314

A Tangled Web: Regulatory Connections between Quorum Sensing and Cyclic Di-GMP  

PubMed Central

Bacteria sense and respond to environmental cues to control important developmental processes. Two widely conserved and important strategies that bacteria employ to sense changes in population density and local environmental conditions are quorum sensing (QS) and cyclic di-GMP (c-di-GMP) signaling, respectively. The importance of these pathways in controlling a broad variety of functions, including virulence, biofilm formation, and motility, has been recognized in many species. Recent research has shown that these pathways are intricately intertwined. Here we review the regulatory connections between QS and c-di-GMP signaling. We propose that the integration of QS with c-di-GMP allows bacteria to assimilate information about the local bacterial population density with other physicochemical environmental signals within the broader c-di-GMP signaling network. PMID:22661686

Srivastava, Disha

2012-01-01

315

Inhaled Lactonase Reduces Pseudomonas aeruginosa Quorum Sensing and Mortality in Rat Pneumonia  

PubMed Central

Rationale The effectiveness of antibiotic molecules in treating Pseudomonas aeruginosa pneumonia is reduced as a result of the dissemination of bacterial resistance. The existence of bacterial communication systems, such as quorum sensing, has provided new opportunities of treatment. Lactonases efficiently quench acyl-homoserine lactone-based bacterial quorum sensing, implicating these enzymes as potential new anti-Pseudomonas drugs that might be evaluated in pneumonia. Objectives The aim of the present study was to evaluate the ability of a lactonase called SsoPox-I to reduce the mortality of a rat P. aeruginosa pneumonia. Methods To assess SsoPox-I-mediated quorum quenching, we first measured the activity of the virulence gene lasB, the synthesis of pyocianin, the proteolytic activity of a bacterial suspension and the formation of biofilm of a PAO1 strain grown in the presence of lactonase. In an acute lethal model of P. aeruginosa pneumonia in rats, we evaluated the effects of an early or deferred intra-tracheal treatment with SsoPox-I on the mortality, lung bacterial count and lung damage. Measurements and Primary Results SsoPox-I decreased PAO1 lasB virulence gene activity, pyocianin synthesis, proteolytic activity and biofilm formation. The early use of SsoPox-I reduced the mortality of rats with acute pneumonia from 75% to 20%. Histological lung damage was significantly reduced but the lung bacterial count was not modified by the treatment. A delayed treatment was associated with a non-significant reduction of mortality. Conclusion These results demonstrate the protective effects of lactonase SsoPox-I in P. aeruginosa pneumonia and open the way for a future therapeutic use. PMID:25350373

Lafleur, John; Lepidi, Hubert; Papazian, Laurent; Rolain, Jean-Marc; Raoult, Didier; Elias, Mikael; Silby, Mark W.; Bzdrenga, Janek; Bregeon, Fabienne; Chabriere, Eric

2014-01-01

316

Oregano essential oil-pectin edible films as anti-quorum sensing and food antimicrobial agents  

PubMed Central

Edible films can be used as carriers for antimicrobial compounds to assure food safety and quality; in addition, pathogenesis of food bacteria is related to a cell to cell communication mechanism called quorum sensing (QS). Oregano essential oil (OEO) has proved to be useful as food antimicrobial; however, its food applications can be compromised by the volatile character of its active constituents. Therefore, formulation of edible films containing OEO can be an alternative to improve its food usages. QS inhibitory activity of OEO and pectin-OEO films was evaluated using Chromobacterium violaceum as bacterial model. Additionally, antibacterial activity was tested against Escherichia coli O157:H7, Salmonella Choleraesuis, Staphylococcus aureus, and Listeria monocytogenes. OEO was effective to inhibit bacterial growth at MIC of 0.24 mg/mL for all tested bacteria and MBC of 0.24, 0.24, 0.48, and 0.24 mg/mL against E. coli O157:H7, S. Choleraesuis, S. aureus, and L. monocytogenes, respectively. Pectin-films incorporated with 36.1 and 25.9 mg/mL of OEO showed inhibition diameters of 16.3 and 15.2 mm for E. coli O157:H7; 18.1 and 24.2 mm for S. Choleraesuis; 20.8 and 20.3 mm for S. aureus; 21.3 and 19.3 mm for L. monocytogenes, respectively. Pectin-OEO film (15.7 mg/mL) was effective against E. coli O157:H7 (9.3 mm), S. aureus (9.7 mm), and L. monocytogenes (9.2 mm), but not for S. Choleraesuis. All concentrations of OEO (0.0156, 0.0312, 0.0625 and 0.125 mg/mL) and pectin-OEO films (15.7, 25.9 and 36.1 mg/mL) showed a significant anti-QS activity expressed as inhibition of violacein production by C. violaceum. Additionally, the application of pectin-OEO films was effective reducing total coliforms, yeast, and molds of shrimp and cucumber slices stored at 4°C during 15 d. These results demonstrated the potential of pectin films enriched with OEO as food related microorganisms and QS inhibitors. PMID:25566215

Alvarez, Maria V.; Ortega-Ramirez, Luis A.; Gutierrez-Pacheco, M. Melissa; Bernal-Mercado, A. Thalia; Rodriguez-Garcia, Isela; Gonzalez-Aguilar, Gustavo A.; Ponce, Alejandra; Moreira, Maria del R.; Roura, Sara I.; Ayala-Zavala, J. Fernando

2014-01-01

317

Determinants governing ligand specificity of the Vibrio harveyi?LuxN quorum-sensing receptor.  

PubMed

Quorum sensing is a process of bacterial cell-cell communication that relies on the production, release and receptor-driven detection of extracellular signal molecules called autoinducers. The quorum-sensing bacterium Vibrio harveyi exclusively detects the autoinducer N-((R)-3-hydroxybutanoyl)-L-homoserine lactone (3OH-C4 HSL) via the two-component receptor LuxN. To discover the principles underlying the exquisite selectivity LuxN has for its ligand, we identified LuxN mutants with altered specificity. LuxN uses three mechanisms to verify that the bound molecule is the correct ligand: in the context of the overall ligand-binding site, His210 validates the C3 modification, Leu166 surveys the chain-length and a strong steady-state kinase bias imposes an energetic hurdle for inappropriate ligands to elicit signal transduction. Affinities for the LuxN kinase on and kinase off states underpin whether a ligand will act as an antagonist or an agonist. Mutations that bias LuxN to the agonized, kinase off, state are clustered in a region adjacent to the ligand-binding site, suggesting that this region acts as the switch that triggers signal transduction. Together, our analyses illuminate how a histidine sensor kinase differentiates between ligands and exploits those differences to regulate its signaling activity. PMID:25367076

Ke, Xiaobo; Miller, Laura C; Bassler, Bonnie L

2015-01-01

318

Quorum sensing and biofilm formation investigated using laser-trapped bacterial arrays  

NASA Astrophysics Data System (ADS)

Studies of individual, free-swimming (planktonic) bacteria have yielded much information about their genetic and phenotypic characteristics and about ``quorum sensing,'' the autoinducing process by which bacteria detect high concentrations of other bacteria. However, in most environments the majority of bacteria are not in the planktonic form but are rather in biofilms, which are highly-structured, dynamic communities of multiple bacteria that adhere to a surface and to each other using an extracellular polysaccharide matrix. Bacteria in biofilms are phenotypically very different from their genetically-identical planktonic counterparts. Among other characteristics, they are much more antibiotic-resistant and virulent. Such biofilms form persistent infections on medical implants and in the lungs of cystic fibrosis patients, where Pseudomonas aeruginosa biofilms are the leading cause of lung damage and, ultimately, death. To understand the importance of different extracellular materials, motility mechanisms, and quorum sensing for biofilm formation and stability, we use single-gene knockout mutants and an infrared laser trap to create a bacterial aggregate that serves as a model biofilm and allows us to measure the importance of these factors as a function of trapping time, surface, and nutritional environment.

Gordon, Vernita; Butler, John; Smalyukh, Ivan; Parsek, Matthew; Wong, Gerard

2008-03-01

319

The ExpR/Sin Quorum-Sensing System Controls Succinoglycan Production in Sinorhizobium meliloti?  

PubMed Central

Sinorhizobium meliloti is a gram-negative soil bacterium capable of forming a symbiotic nitrogen-fixing relationship with its plant host, Medicago sativa. Various bacterially produced factors are essential for successful nodulation. For example, at least one of two exopolysaccharides produced by S. meliloti (succinoglycan or EPS II) is required for nodule invasion. Both of these polymers are produced in high- and low-molecular-weight (HMW and LMW, respectively) fractions; however, only the LMW forms of either succinoglycan or EPS II are active in nodule invasion. The production of LMW succinoglycan can be generated by direct synthesis or through the depolymerization of HMW products by the action of two specific endoglycanases, ExsH and ExoK. Here, we show that the ExpR/Sin quorum-sensing system in S. meliloti is involved in the regulation of genes responsible for succinoglycan biosynthesis as well as in the production of LMW succinoglycan. Therefore, quorum sensing, which has been shown to regulate the production of EPS II, also plays an important role in succinoglycan biosynthesis. PMID:17644606

Glenn, Sarah A.; Gurich, Nataliya; Feeney, Morgan A.; González, Juan E.

2007-01-01

320

``Quorum sensing'' generated multistability and chaos in a synthetic genetic oscillator  

NASA Astrophysics Data System (ADS)

We model the dynamics of the synthetic genetic oscillator Repressilator equipped with quorum sensing. In addition to a circuit of 3 genes repressing each other in a unidirectional manner, the model includes a phase-repulsive type of the coupling module implemented as the production of a small diffusive molecule—autoinducer (AI). We show that the autoinducer (which stimulates the transcription of a target gene) is responsible for the disappearance of the limit cycle (LC) through the infinite period bifurcation and the formation of a stable steady state (SSS) for sufficiently large values of the transcription rate. We found conditions for hysteresis between the limit cycle and the stable steady state. The parameters' region of the hysteresis is determined by the mRNA to protein lifetime ratio and by the level of transcription-stimulating activity of the AI. In addition to hysteresis, increasing AI-dependent stimulation of transcription may lead to the complex dynamic behavior which is characterized by the appearance of several branches on the bifurcation continuation, containing different regular limit cycles, as well as a chaotic regime. The multistability which is manifested as the coexistence between the stable steady state, limit cycles, and chaos seems to be a novel type of the dynamics for the ring oscillator with the added quorum sensing positive feedback.

Potapov, I.; Zhurov, B.; Volkov, E.

2012-06-01

321

Synchronization and quorum sensing in an ensemble of indirectly coupled chaotic oscillators  

NASA Astrophysics Data System (ADS)

The fact that the elements in some realistic systems are influenced by each other indirectly through a common environment has stimulated a new surge of studies on the collective behavior of coupled oscillators. Most of the previous studies, however, consider only the case of coupled periodic oscillators, and it remains unknown whether and to what extent the findings can be applied to the case of coupled chaotic oscillators. Here, using the population density and coupling strength as the tuning parameters, we explore the synchronization and quorum sensing behaviors in an ensemble of chaotic oscillators coupled through a common medium, in which some interesting phenomena are observed, including the appearance of the phase synchronization in the process of progressive synchronization, the various periodic oscillations close to the quorum sensing transition, and the crossover of the critical population density at the transition. These phenomena, which have not been reported for indirectly coupled periodic oscillators, reveal a corner of the rich dynamics inherent in indirectly coupled chaotic oscillators, and are believed to have important implications to the performance and functionality of some realistic systems.

Li, Bing-Wei; Fu, Chenbo; Zhang, Hong; Wang, Xingang

2012-10-01

322

Study of Signal Detection, Integration, and Propagation in Quorum Sensing at the Single Cell Level  

NASA Astrophysics Data System (ADS)

Bacteria respond to their environment and to each other and accordingly adjust their gene-expression levels. Accurate signal detection, appropriate signal integration, and faithful signal propagation are essential for a cell to make correct adjustments in response to various extracellular cues. To better understand this information processing by living cells, we studied a model system -- the quorum-sensing circuit in Vibrio harveyi. Quorum sensing is a process in which bacteria communicate with each other by diffusible chemical molecules, termed ``autoinducers'', to commit to coordinated developmental decisions. Three types of autoinducers are detected coincidently by three parallel receptors. The signals are then integrated into the same signaling pathway and propagated by phosphorylation or dephosphorylation of the pathway components. To quantitatively measure the intracellular response, we applied a fluorescent protein reporter, whose production is regulated by a phosphorylated protein in the pathway. By single-cell microscopy, we can explore features of this information-processing circuit such as coincidence detection, signal integration, noise reduction or filtering, and especially the fidelity in signal processing achieved in the presence of inevitable fluctuations.

Long, Tao; Bassler, Bonnie; Wingreen, Ned

2007-03-01

323

Quantifying the Integration of Quorum-Sensing Signals with Single-Cell Resolution  

PubMed Central

Cell-to-cell communication in bacteria is a process known as quorum sensing that relies on the production, detection, and response to the extracellular accumulation of signaling molecules called autoinducers. Often, bacteria use multiple autoinducers to obtain information about the vicinal cell density. However, how cells integrate and interpret the information contained within multiple autoinducers remains a mystery. Using single-cell fluorescence microscopy, we quantified the signaling responses to and analyzed the integration of multiple autoinducers by the model quorum-sensing bacterium Vibrio harveyi. Our results revealed that signals from two distinct autoinducers, AI-1 and AI-2, are combined strictly additively in a shared phosphorelay pathway, with each autoinducer contributing nearly equally to the total response. We found a coherent response across the population with little cell-to-cell variation, indicating that the entire population of cells can reliably distinguish several distinct conditions of external autoinducer concentration. We speculate that the use of multiple autoinducers allows a growing population of cells to synchronize gene expression during a series of distinct developmental stages. PMID:19320539

Long, Tao; Tu, Kimberly C; Wang, Yufang; Mehta, Pankaj; Ong, N. P; Bassler, Bonnie L; Wingreen, Ned S

2009-01-01

324

Influence of quorum sensing signal molecules on biofilm formation in Proteus mirabilis O18.  

PubMed

The influence of basis of quorum sensing molecules on Proteus strains is much less known as compared to Pseudomonas or Escherichia. We have previously shown that a series of acylated homoserine lactones (acyl-HSL) does not influence the ureolytic, proteolytic, or hemolytic abilities, and that the swarming motility of Proteus mirabilis rods is strain specific. The aim of the presented study was to find out if the presence of a series of acyl-HSL influences biofilm formation of P. mirabilis laboratory strain belonging to O18 serogroup. This serogroup is characterized by the presence of a unique non-carbohydrate component, namely phosphocholine. Escherichia coli and P. mirabilis O18 strains used in this work contains cloned plasmids encoding fluorescent protein genes with constitutive gene expression. In mixed biofilms in stationary and continuous flow conditions, P. mirabilis O18 overgrow whole culture. P. mirabilis O18 strain has genetically proved a presence of AI-2 quorum sensing system. Differences in biofilm structure were observed depending on the biofilm type and culture methods. From tested acylated homoserine lactones (BHL, HHL, OHL, DHL, dDHL, tDHL), a significant influence had BHL on thickness, structure, and the amount of exopolysaccharides produced by biofilms formed by P. mirabilis O18 pDsRed(2). PMID:22198843

Stankowska, Dorota; Czerwonka, Grzegorz; Rozalska, Sylwia; Grosicka, Michalina; Dziadek, Jaroslaw; Kaca, Wieslaw

2012-01-01

325

Regulation of Yersina pestis Virulence by AI-2 Mediated Quorum Sensing  

SciTech Connect

The proposed research was motivated by an interest in understanding Y. pestis virulence mechanisms and bacteria cell-cell communication. It is expected that a greater understanding of virulence mechanisms will ultimately lead to biothreat countermeasures and novel therapeutics. Y. pestis is the etiological agent of plague, the most devastating disease in human history. Y. pestis infection has a high mortality rate and a short incubation before mortality. There is no widely available and effective vaccine for Y. pestis and multi-drug resistant strains are emerging. Y. pestis is a recognized biothreat agent based on the wide distribution of the bacteria in research laboratories around the world and on the knowledge that methods exist to produce and aerosolize large amounts of bacteria. We hypothesized that cell-cell communication via signaling molecules, or quorum sensing, by Y. pestis is important for the regulation of virulence factor gene expression during host invasion, though a causative link had never been established. Quorum sensing is a mode of intercellular communication which enables orchestration of gene expression for many bacteria as a function of population density and available evidence suggests there may be a link between quorum sensing and regulation of Y. pesits virulence. Several pathogenic bacteria have been shown to regulate expression of virulence factor genes, including genes encoding type III secretion, via quorum sensing. The Y. pestis genome encodes several cell-cell signaling pathways and the interaction of at least three of these are thought to be involved in one or more modes of host invasion. Furthermore, Y. pestis gene expression array studies carried out at LLNL have established a correlation between expression of known virulence factors and genes involved in processing of the AI-2 quorum sensing signal. This was a basic research project that was intended to provide new insights into bacterial intercellular communication and how it is used to regulate virulence in Y. pestis. It is known that many bacteria use intercellular signaling molecules to orchestrate gene expression and cellular function. A fair amount is known about production and uptake of signaling molecules, but very little is known about how intercellular signaling regulates other pathways. Although several studies demonstrate that intercellular signaling plays a role in regulating virulence in other pathogens, the link between signaling and regulation of virulence has not been established. Very little work had been done directly with Y. pestis intercellular signaling apart from the work carried out at LLNL. The research we proposed was intended to both establish a causative link between AI-2 intercellular signaling and regulation of virulence in Y. pestis and elucidate the fate of the AI-2 signaling molecule after it is taken up and processed by Y. pestis. Elucidating the fate of AI-2 was expected to lead directly to the understanding of how AI-2 signal processing regulates other pathways as well as provide new insights in this direction.

Segelke, B; Hok, S; Lao, V; Corzett, M; Garcia, E

2010-03-29

326

Inhibition of Quorum Sensing-Controlled Virulence Factor Production in Pseudomonas aeruginosa by South Florida Plant Extracts  

Microsoft Academic Search

Quorum sensing (QS) is a key regulator of virulence and biofilm formation in Pseudomonas aeruginosa and other medically relevant bacteria. Aqueous extracts of six plants, Conocarpus erectus, Chamaesyce hypericifolia, Callistemon viminalis, Bucida buceras, Tetrazygia bicolor, and Quercus virginiana, were examined in this study for their effects on P. aeruginosa virulence factors and the QS system. C. erectus, B. buceras, and

Allison Adonizio; Kok-Fai Kong; Kalai Mathee

2008-01-01

327

Pseudomonas aeruginosa Quorum-Sensing Systems May Control Virulence Factor Expression in the Lungs of Patients with Cystic Fibrosis  

Microsoft Academic Search

Individuals with cystic fibrosis (CF) are commonly colonized with Pseudomonas aeruginosa. The chronic infections caused by P. aeruginosa are punctuated by acute exacerbations of the lung disease, which lead to significant morbidity and mortality. As regulators of virulence determinants, P. aeruginosa quorum-sensing systems may be active in the chronic lung infections associated with CF. We have examined the levels of

David L. Erickson; Ryan Endersby; Amanda Kirkham; Kent Stuber; Dolina D. Vollman; Harvey R. Rabin; Ian Mitchell; Douglas G. Storey

2002-01-01

328

Comparative study of the pln locus of the quorum-sensing regulated bacteriocin-producing L. plantarum J51 strain  

Microsoft Academic Search

Lactobacillus plantarum J51 strain was isolated from a Rioja red wine and it showed bacteriocin activity against a wide range of lactic acid bacteria of oenological importance. These characteristics conferred L. plantarum J51 a high interest both in wine microbiology and in the study of bacteriocin production. In this work the bacteriocin production regulated under the “quorum-sensing” mechanism is observed

Laura Navarro; Beatriz Rojo-Bezares; Yolanda Sáenz; Lorena Díez; Myriam Zarazaga; Fernanda Ruiz-Larrea; Carmen Torres

2008-01-01

329

Genome Sequence of Maribius sp. Strain MOLA 401, a Marine Roseobacter with a Quorum-Sensing Cell-Dependent Physiology  

PubMed Central

Maribius sp. strain MOLA401 is an alphaproteobacterium isolated from a coral reef lagoon located in New Caledonia, France. We report the genome sequence and its annotation which, interestingly, reveals the presence of genes involved in quorum sensing. This is the first report of a full genome within the genus Maribius. PMID:25278539

Doberva, Margot; Sanchez-Ferandin, Sophie; Ferandin, Yoan; Intertaglia, Laurent; Joux, Fabien; Lebaron, Philippe

2014-01-01

330

Genome Sequence of Maribius sp. Strain MOLA 401, a Marine Roseobacter with a Quorum-Sensing Cell-Dependent Physiology.  

PubMed

Maribius sp. strain MOLA401 is an alphaproteobacterium isolated from a coral reef lagoon located in New Caledonia, France. We report the genome sequence and its annotation which, interestingly, reveals the presence of genes involved in quorum sensing. This is the first report of a full genome within the genus Maribius. PMID:25278539

Doberva, Margot; Sanchez-Ferandin, Sophie; Ferandin, Yoan; Intertaglia, Laurent; Joux, Fabien; Lebaron, Philippe; Lami, Raphaël

2014-01-01

331

Insights into the Quorum-Sensing Activity in Aeromonas hydrophila Strain M013 as Revealed by Whole-Genome Sequencing.  

PubMed

Aeromonas hydrophila species can be found in warm climates and can survive in different environments. They possess the ability to communicate within their populations, which is known as quorum sensing. In this work, we present the draft genome sequence of A. hydrophila M013, a bacterium isolated from a Malaysian tropical rainforest waterfall. PMID:25555739

Tan, Wen-Si; Yin, Wai-Fong; Chan, Kok-Gan

2015-01-01

332

Draft Genome Sequence of a Quorum-Sensing Bacterium, Dickeya sp. Strain 2B12, Isolated from a Freshwater Lake.  

PubMed

Dickeya sp. strain 2B12 was isolated from a freshwater lake in Malaysia. Here, we report the draft genome sequence of Dickeya sp. 2B12 sequenced by the Illumina MiSeq platform. With the genome sequence available, this genome sequence will be useful for the study of quorum-sensing activity in this isolate. PMID:25657288

Tan, Kian-Hin; Sheng, Kit-Yeng; Chang, Chien-Yi; Yin, Wai-Fong; Chan, Kok-Gan

2015-01-01

333

AN EVALUATION OF ASCORBIC ACID AS A QUORUM SENSING ANALOGUE TO CONTROL GROWTH, SPORULATION, AND ENTEROTOXIN PRODUCTION IN CLOSTRIDIUM PERFRINGENS  

Technology Transfer Automated Retrieval System (TEKTRAN)

Inhibition of quorum sensing by enterotoxin-producing strains of Clostridium perfringens was investigated. Autoinducer-2 (AI-2) activity was measured in the presence and absence of ascorbic acid (vitamin C; concentrations ranging from 10 to 300 mM), an AI-2 analogue. Subsequent effects on AI-2 pro...

334

Vibrio fischeri Uses Two Quorum-Sensing Systems for the Regulation of Early and Late Colonization Factors  

Microsoft Academic Search

Vibrio fischeri possesses two quorum-sensing systems, ain and lux, using acyl homoserine lactones as signaling molecules. We have demonstrated previously that the ain system activates luminescence gene ex- pression at lower cell densities than those required for lux system activation and that both systems are essential for persistent colonization of the squid host, Euprymna scolopes. Here, we asked whether the

Claudia Lupp; Edward G. Ruby

2005-01-01

335

Genomic Insights of Pectobacterium carotovorum Strain M022 Quorum-Sensing Activity through Whole-Genome Sequencing.  

PubMed

Pectobacterium carotovorum is known to cause serious damage to various major crops worldwide. Here, we report the draft genome of Pectobacterium carotovorum strain M022, a freshwater isolate from a Malaysian waterfall, which has been reported as a plant pathogen and is able to communicate with N-acylhomoserine lactone-mediated quorum sensing. PMID:25676763

Chan, Kok-Gan; Tan, Wen-Si

2015-01-01

336

Insights into the Quorum-Sensing Activity in Aeromonas hydrophila Strain M013 as Revealed by Whole-Genome Sequencing  

PubMed Central

Aeromonas hydrophila species can be found in warm climates and can survive in different environments. They possess the ability to communicate within their populations, which is known as quorum sensing. In this work, we present the draft genome sequence of A. hydrophila M013, a bacterium isolated from a Malaysian tropical rainforest waterfall. PMID:25555739

Tan, Wen-Si; Yin, Wai-Fong

2015-01-01

337

Genetic and Phenotypic Diversity of Quorum-Sensing Systems in Clinical and Environmental Isolates of Vibrio cholerae  

Microsoft Academic Search

Vibrio cholerae is the causative agent of cholera, a severe and devastating diarrheal disease. V. cholerae lives naturally in various aquatic habitats during interepidemic periods. Recent studies reveal that quorum-sensing systems, which exist in many bacteria and help them monitor their population densities and regulate various cellular functions, control V. cholerae pathogenesis, biofilm formation, and protease production. In this study

Adam Joelsson; Zhi Liu; Jun Zhu

2006-01-01

338

Genomic Insights of Pectobacterium carotovorum Strain M022 Quorum-Sensing Activity through Whole-Genome Sequencing  

PubMed Central

Pectobacterium carotovorum is known to cause serious damage to various major crops worldwide. Here, we report the draft genome of Pectobacterium carotovorum strain M022, a freshwater isolate from a Malaysian waterfall, which has been reported as a plant pathogen and is able to communicate with N-acylhomoserine lactone-mediated quorum sensing. PMID:25676763

Tan, Wen-Si

2015-01-01

339

Modulation of quorum sensing controlled behaviour of bacteria by growing seedling, seed and seedling extracts of leguminous plants  

Microsoft Academic Search

Effect of growing seedling, seeds and seedlings extracts from seven leguminous plants (Pisum sativum, Vigna radiata, Vigna mungo, Cajanus cajan, Lentil culinaris, Cicer arietinum and Trigonella foenum graecum) were screened for their ability to influence quorum sensing controlled pigment production in Chromobacterium violaceum indicator strains (CV12472 and CVO26). Germinating seedling and seedling extracts of only P. sativum (pea) showed inhibition

Qaseem Fatima; Maryam Zahin; Mohd Sajjad Ahmad Khan; Iqbal Ahmad

2010-01-01

340

Thermoregulation of N-Acyl Homoserine Lactone-Based Quorum Sensing in the Soft Rot Bacterium Pectobacterium atrosepticum?  

PubMed Central

The psychrotolerant bacterium Pectobacterium atrosepticum produces four N-acyl homoserine lactones under a wide range of temperatures. Their thermoregulation differs from that of the exoenzyme production, described as being under quorum-sensing control. A mechanism involved in this thermoregulation consists of controlling N-acyl homoserine lactones synthase production at a transcriptional level. PMID:17468275

Latour, Xavier; Diallo, Stéphanie; Chevalier, Sylvie; Morin, Danièle; Smadja, Bruno; Burini, Jean-François; Haras, Dominique; Orange, Nicole

2007-01-01

341

Noise and crosstalk in two quorum-sensing inputs of Vibrio fischeri  

PubMed Central

Background One of the puzzles in bacterial quorum sensing is understanding how an organism integrates the information gained from multiple input signals. The marine bacterium Vibrio fischeri regulates its bioluminescence through a quorum sensing mechanism that receives input from three pheromone signals, including two acyl homoserine lactone (HSL) signals. While the role of the 3-oxo-C6 homoserine lactone (3OC6HSL) signal in activating the lux genes has been extensively studied and modeled, the role of the C8 homoserine lactone (C8HSL) is less obvious, as it can either activate luminescence or block its activation. It remains unclear how crosstalk between C8HSL and 3OC6HSL affects the information that the bacterium obtains through quorum sensing. Results We have used microfluidic methods to measure the response of individual V.fischeri cells to combinations of C8HSL and 3OC6HSL. By measuring the fluorescence of individual V.fischeri cells containing a chromosomal gfp-reporter for the lux genes, we study how combinations of exogenous HSLs affect both the population average and the cell-to-cell variability of lux activation levels. At the level of a population average, the crosstalk between the C8HSL and 3OC6HSL inputs is well-described by a competitive inhibition model. At the level of individual cells, the heterogeneity in the lux response depends only on the average degree of activation, so that the noise in the output is not reduced by the presence of the second HSL signal. Overall we find that the mutual information between the signal inputs and the lux output is less than one bit. A nonlinear correlation between fluorescence and bioluminescence outputs from lux leads to different noise properties for these reporters. Conclusions The lux genes in V.fischeri do not appear to distinguish between the two HSL inputs, and even with two signal inputs the regulation of lux is extremely noisy. Hence the role of crosstalk from the C8HSL input may not be to improve sensing precision, but rather to suppress the sensitivity of the switch for as long as possible during colony growth. PMID:21959018

2011-01-01

342

The involvement of bacterial quorum sensing in the spoilage of refrigerated Litopenaeus vannamei.  

PubMed

Quorum-sensing signals in refrigerated shrimp (Litopenaeus vannamei) undergoing spoilage were examined using bioreporter assays, thin-layer chromatography and gas chromatography-mass spectrometry, and the results revealed the presence of three types of autoinducers including acetylated homoserine lactones (AHLs) (i.e., N-hexanoyl-homoserine lactone, N-oxohexanoyl-homoserine lactone and N-octanoyl-homoserine lactone), autoinducer-2, and cyclic dipeptides (i.e., cyclo-(L-Pro-L-Leu), cyclo-(L-Leu-L-Leu) and cyclo-(L-Pro-L-Phe)). Autoinducer-2, rather than any AHL, was detected in extracts from pure cultures of the specific spoilage organisms (SSO), i.e., Shewanella putrefaciens (SS01) and Shewanella baltica (SA02). As for the cyclic peptides, only SA02 was determined to produce cyclo-(L-Pro-L-Leu). According to the transcription levels of LuxR (the master quorum-sensing regulator) in the SSO in response to exogenous autoinducers, the SSO could sense AHLs and cyclo-(L-Leu-L-Leu), rather than autoinducer-2, cyclo-(L-Leu-L-Leu) and cyclo-(L-Pro-L-Phe). In accordance with the results of LuxR expression, the production of biofilm matrixes and extracellular proteases in the SSO was regulated by exogenous AHLs and cyclo-(L-Pro-L-Leu), rather than 4,5-dihydroxy-2,3-pentanedione (the autoinducer-2 precursor), cyclo-(L-Leu-L-Leu) and cyclo-(L-Pro-L-Phe). Exogenous N-hexanoyl-homoserine lactone and cyclo-(L-Pro-L-Leu) increased the growth rates and population percentages of the SSO in shrimp samples under refrigerated storage, and interestingly, exogenous 4,5-dihydroxy-2,3-pentanedione also increased the population percentages of the SSO in vivo by inhibiting the growth of the competing bacteria. However, according to the levels of TVB-N and the volatile organic components in the shrimp samples, exogenous 4,5-dihydroxy-2,3-pentanedione did not accelerate the shrimp spoilage process as N-hexanoyl-homoserine lactone and cyclo-(L-Pro-L-Leu) did. In summary, our results suggest that quorum sensing involves the spoilage of refrigerated Litopenaeus vannamei. PMID:25305441

Zhu, Suqin; Wu, Haohao; Zeng, Mingyong; Liu, Zunying; Wang, Ying

2015-01-01

343

Exposure to static magnetic field stimulates quorum sensing circuit in luminescent Vibrio strains of the Harveyi clade.  

PubMed

In this study, the evidence of electron-dense magnetic inclusions with polyhedral shape in the cytoplasm of Harveyi clade Vibrio strain PS1, a bioluminescent bacterium living in symbiosis with marine organisms, led us to investigate the behavior of this bacterium under exposure to static magnetic fields ranging between 20 and 2000 Gauss. When compared to sham-exposed, the light emission of magnetic field-exposed bacteria growing on solid medium at 18°C ±0.1°C was increased up to two-fold as a function of dose and growth phase. Stimulation of bioluminescence by magnetic field was more pronounced during the post-exponential growth and stationary phase, and was lost when bacteria were grown in the presence of the iron chelator deferoxamine, which caused disassembly of the magnetic inclusions suggesting their involvement in magnetic response. As in luminescent Vibrio spp. bioluminescence is regulated by quorum sensing, possible effects of magnetic field exposure on quorum sensing were investigated. Measurement of mRNA levels by reverse transcriptase real time-PCR demonstrated that luxR regulatory gene and luxCDABE operon coding for luciferase and fatty acid reductase complex were significantly up-regulated in magnetic field-exposed bacteria. In contrast, genes coding for a type III secretion system, whose expression was negatively affected by LuxR, were down-regulated. Up-regulation of luxR paralleled with down-regulation of small RNAs that mediate destabilization of luxR mRNA in quorum sensing signaling pathways. The results of experiments with the well-studied Vibrio campbellii strain BB120 (originally classified as Vibrio harveyi) and derivative mutants unable to synthesize autoinducers suggest that the effects of magnetic fields on quorum sensing may be mediated by AI-2, the interspecies quorum sensing signal molecule. PMID:24960170

Talà, Adelfia; Delle Side, Domenico; Buccolieri, Giovanni; Tredici, Salvatore Maurizio; Velardi, Luciano; Paladini, Fabio; De Stefano, Mario; Nassisi, Vincenzo; Alifano, Pietro

2014-01-01

344

The Quorum-Sensing Molecules Farnesol/Homoserine Lactone and Dodecanol Operate via Distinct Modes of Action in Candida albicans?  

PubMed Central

Living as a commensal, Candida albicans must adapt and respond to environmental cues generated by the mammalian host and by microbes comprising the natural flora. These signals have opposing effects on C. albicans, with host cues promoting the yeast-to-hyphal transition and bacteria-derived quorum-sensing molecules inhibiting hyphal development. Hyphal development is regulated through modulation of the cyclic AMP (cAMP)/protein kinase A (PKA) signaling pathway, and it has been postulated that quorum-sensing molecules can affect filamentation by inhibiting the cAMP pathway. Here, we show that both farnesol and 3-oxo-C12-homoserine lactone, a quorum-sensing molecule secreted by Pseudomonas aeruginosa, block hyphal development by affecting cAMP signaling; they both directly inhibited the activity of the Candida adenylyl cyclase, Cyr1p. In contrast, the 12-carbon alcohol dodecanol appeared to modulate hyphal development and the cAMP signaling pathway without directly affecting the activity of Cyr1p. Instead, we show that dodecanol exerted its effects through a mechanism involving the C. albicans hyphal repressor, Sfl1p. Deletion of SFL1 did not affect the response to farnesol but did interfere with the response to dodecanol. Therefore, quorum sensing in C. albicans is mediated via multiple mechanisms of action. Interestingly, our experiments raise the possibility that the Burkholderia cenocepacia diffusible signal factor, BDSF, also mediates its effects via Sfl1p, suggesting that dodecanol's mode of action, but not farnesol or 3-oxo-C12-homoserine lactone, may be used by other quorum-sensing molecules. PMID:21666074

Hall, Rebecca A.; Turner, Kara J.; Chaloupka, James; Cottier, Fabien; De Sordi, Luisa; Sanglard, Dominique; Levin, Lonny R.; Buck, Jochen; Mühlschlegel, Fritz A.

2011-01-01

345

The social biology of quorum sensing in a naturalistic host pathogen system.  

PubMed

Many microorganisms cooperate by secreting products that are commonly available to neighboring cells. These "public goods" include autoinduced, quorum-sensing (QS) molecules and the virulence factors activated by these signals. Public goods cooperation is exploitable by cheaters, cells that avoid the costs of production but gain an advantage by freeloading on the products of others. QS signals and responses can be cooperative under artificial laboratory conditions, but it remains unclear whether QS is cooperative in nature: little is known about the frequency of cheaters in natural populations, and cheaters may do poorly because of the importance of QS in major transcriptional networks. Here, we investigate the cooperative nature of QS in a natural system: the Gram-positive insect pathogen Bacillus thuringiensis and the larvae of the diamondback moth, Plutella xylostella. Although we find evidence of cooperation, QS null mutants are not effective cheats in vivo and cannot outcompete wild-type strains. We show that spatial structure limits mutant fitness and that well-separated microcolonies occur in vivo because of the strong population bottlenecks occurring during natural infection. We argue that spatial structure and low densities are the norm in early-stage infections, and this can explain why QS cheaters are rare in B. thuringiensis and its relatives. These results contrast with earlier experiments describing the high fitness of Gram-negative QS cheaters and suggest that QS suppression ("quorum quenching") can be clinically effective without having negative impacts on the evolution of virulence. PMID:25308072

Zhou, Liqin; Slamti, Leyla; Nielsen-LeRoux, Christina; Lereclus, Didier; Raymond, Ben

2014-10-20

346

Conformational Change-Induced Repeat Domain Expansion Regulates Rap Phosphatase Quorum-Sensing Signal Receptors  

PubMed Central

The large family of Gram-positive quorum-sensing receptors known as the RNPP proteins consists of receptors homologous to the Rap, NprR, PlcR, and PrgX proteins that are regulated by imported oligopeptide autoinducers. Rap proteins are phosphatases and transcriptional anti-activators, and NprR, PlcR, and PrgX proteins are DNA binding transcription factors. Despite their obvious importance, the mechanistic basis of oligopeptide receptor regulation is largely unknown. Here, we report the X-ray crystal structure of the Bacillus subtilis quorum-sensing receptor RapJ in complex with the centrally important oligopeptide autoinducer competence and sporulation factor (CSF, also termed PhrC), a member of the Phr family of quorum-sensing signals. Furthermore, we present the crystal structure of RapI. Comparison of the RapJ-PhrC, RapI, RapH-Spo0F, and RapF-ComAC crystal structures reveals the mechanistic basis of Phr activity. More specifically, when complexed with target proteins, Rap proteins consist of a C-terminal tetratricopeptide repeat (TPR) domain connected by a flexible helix-containing linker to an N-terminal 3-helix bundle. In the absence of a target protein or regulatory peptide, the Rap protein 3-helix bundle adopts different conformations. However, in the peptide-bound conformation, the Rap protein N-terminal 3-helix bundle and linker undergo a radical conformational change, form TPR-like folds, and merge with the existing C-terminal TPR domain. To our knowledge, this is the first example of conformational change-induced repeat domain expansion. Furthermore, upon Phr binding, the entire Rap protein is compressed along the TPR superhelical axis, generating new intramolecular contacts that lock the Rap protein in an inactive state. The fact that Rap proteins are conformationally flexible is surprising considering that it is accepted dogma that TPR proteins do not undergo large conformational changes. Repeat proteins are widely used as scaffolds for the development of designed affinity reagents, and we propose that Rap proteins could be used as scaffolds for engineering novel ligand-switchable affinity reagents. PMID:23526881

Parashar, Vijay; Jeffrey, Philip D.; Neiditch, Matthew B.

2013-01-01

347

Quorum-sensing non-coding small RNAs use unique pairing regions to differentially control mRNA targets.  

PubMed

Quorum sensing is a mechanism of cell-cell communication that bacteria use to control collective behaviours including bioluminescence, biofilm formation and virulence factor production. In the Vibrio harveyi and Vibrio cholerae quorum-sensing circuits, multiple non-coding small regulatory RNAs called the quorum-regulated small RNAs (Qrr sRNAs) function to establish the global quorum-sensing gene expression pattern by modulating translation of multiple mRNAs encoding quorum-sensing regulatory factors. Here we show that the Qrr sRNAs post-transcriptionally activate production of the low cell density master regulator AphA through base pairing to aphA mRNA, and this is crucial for the accumulation of appropriate levels of AphA protein at low cell density. We find that the Qrr sRNAs use unique pairing regions to discriminate between their different targets. Qrr1 is not as effective as Qrr2-5 in activating aphA because Qrr1 lacks one of two required pairing regions. However, Qrr1 is equally effective as the other Qrr sRNAs at controlling targets like luxR and luxO because it harbours all of the required pairing regions for these targets. Sequence comparisons reveal that Vibrionaceae species possessing only qrr1 do not have the aphA gene under Qrr sRNA control. Our findings suggest co-evolving relationships between particular Qrr sRNAs and particular mRNA targets. PMID:22229925

Shao, Yi; Bassler, Bonnie L

2012-02-01

348

Inhibition of quorum sensing-controlled virulence factor production in Pseudomonas aeruginosa PAO1 by Ayurveda spice clove (Syzygium aromaticum) bud extract.  

PubMed

Quorum sensing controls the virulence determinants in most proteobacteria. In this work, the hexane, chloroform and methanol extracts of an Ayurveda spice, namely clove (Syzygium aromaticum), shown anti-quorum sensing activity. Hexane and methanol extracts of clove inhibited the response of C. violaceum CV026 to exogenously supplied N-hexanoylhomoserine lactone, in turn preventing violacein production. Chloroform and methanol extracts of clove significantly reduced bioluminescence production by E. coli [pSB1075] grown in the presence of N-(3-oxododecanoyl)-L-homoserine lactone. We demonstrated that clove extract inhibited quorum sensing-regulated phenotypes in Pseudomonas aeruginosa PA01, including expression of lecA::lux (by hexane extract), swarming (maximum inhibition by methanol extract), pyocyanin (maximum inhibition by hexane extract). This study shows that the presence of natural compounds that exhibit anti-quorum sensing activity in the clove extracts may be useful as the lead of anti-infective drugs. PMID:22666015

Krishnan, Thiba; Yin, Wai-Fong; Chan, Kok-Gan

2012-01-01

349

Identification of Four New agr Quorum Sensing-Interfering Cyclodepsipeptides from a Marine Photobacterium  

PubMed Central

During our search for new natural products from the marine environment, we discovered a wide range of cyclic peptides from a marine Photobacterium, closely related to P. halotolerans. The chemical fingerprint of the bacterium showed primarily non-ribosomal peptide synthetase (NRPS)-like compounds, including the known pyrrothine antibiotic holomycin and a wide range of peptides, from diketopiperazines to cyclodepsipeptides of 500–900 Da. Purification of components from the pellet fraction led to the isolation and structure elucidation of four new cyclodepsipeptides, ngercheumicin F, G, H, and I. The ngercheumicins interfered with expression of virulence genes known to be controlled by the agr quorum sensing system of Staphylococcus aureus, although to a lesser extent than the previously described solonamides from the same strain of Photobacterium. PMID:24351904

Kjaerulff, Louise; Nielsen, Anita; Mansson, Maria; Gram, Lone; Larsen, Thomas O.; Ingmer, Hanne; Gotfredsen, Charlotte H.

2013-01-01

350

Synthetic quorum-sensing circuit to control consortial biofilm formation and dispersal in a microfluidic device  

PubMed Central

To utilize biofilms for chemical transformations in biorefineries they need to be controlled and replaced. Previously, we engineered the global regulator Hha and cyclic diguanylate-binding BdcA to create proteins that enable biofilm dispersal. Here we report a biofilm circuit that utilizes these two dispersal proteins along with a population-driven quorum-sensing switch. With this synthetic circuit, in a novel microfluidic device, we form an initial colonizer biofilm, introduce a second cell type (dispersers) into this existing biofilm, form a robust dual-species biofilm and displace the initial colonizer cells in the biofilm with an extracellular signal from the disperser cells. We also remove the disperser biofilm with a chemically induced switch, and the consortial population could tune. Therefore, for the first time, cells have been engineered that are able to displace an existing biofilm and then be removed on command allowing one to control consortial biofilm formation for various applications. PMID:22215088

Hong, Seok Hoon; Hegde, Manjunath; Kim, Jeongyun; Wang, Xiaoxue; Jayaraman, Arul; Wood, Thomas K.

2012-01-01

351

Quorum sensing peptides mediating interspecies bacterial cell death as a novel class of antimicrobial agents.  

PubMed

mazEF is a toxin-antitoxin stress-induced module which is abundant on the chromosome of most bacteria including pathogens and most extensively studied in Escherichia coli. E. coli mazEF mediated cell death is a population phenomenon requiring the quorum-sensing (QS) 'Extracellular Death Factor' (EDF), the E. coli peptide NNWNN. E. coli mazEF-mediated cell death can also be triggered by different QS peptides secreted by the Gram positive bacterium Bacillus subtilis and the Gram negative bacterium Pseudomonas aeruginosa. Thus, the different EDFs belong to a family of QS peptides that mediates interspecies cell death. We suggest that members of the EDF family may become the basis for a novel class of antimicrobial agents to trigger death from outside the bacterial cells. PMID:25244032

Kumar, Sathish; Engelberg-Kulka, Hanna

2014-10-01

352

Dynamics and Mechanism of A Quorum Sensing Network Regulated by Small RNAs in Vibrio Harveyi  

NASA Astrophysics Data System (ADS)

Bacterial quorum sensing (QS) has attracted much interests and it is an important process of cell communication. Recently, Bassler et al. studied the phenomena of QS regulated by small RNAs and the experimental data showed that small RNAs played important role in the QS of Vibrio harveyi and it can permit the fine-tuning of gene regulation and maintenance of homeostasis. According to Michaelis—Menten kinetics and mass action law in this paper, we construct a mathematical model to investigate the mechanism induced QS by coexist of small RNA and signal molecular (AI) and show that there are periodic oscillation when the time delay and Hill coefficient exceed a critical value and the periodic oscillation produces the change of concentration and induces QS. These results are fit to the experimental results. In the meanwhile, we also get some theoretical value of Hopf Bifurcation on time deday. In addition, we also find this network is robust against noise.

Shen, Jian-Wei

2011-03-01

353

Synthesis and quorum sensing inhibitory activity of key phenolic compounds of ginger and their derivatives.  

PubMed

Phenolic components of ginger (Zingiber officinale Roscoe) viz. [6]-gingerol, [6]-shogaol and zingerone exhibited quorum sensing inhibitory activity (QSI) against Chromobacterium violaceum and Pseudomonas aeruginosa. The inhibitory activity of all the compounds was studied by zone inhibition, pyocyanin, and violacein assay. All the compounds displayed good inhibition at 500ppm. [6]-Azashogaol, a new derivative of [6]-shogaol has been synthesized by Beckmann rearrangement of its oxime in the presence of ZnCl2. The structure elucidation of this new derivative was carried out by 1D ((1)H NMR and (13)C NMR) and 2D-NMR (COSY, HSQC and NOESY) spectral studies. This compound showed good QSI activity against P. aeruginosa. An isoxazoline derivative of [6]-gingerol was prepared and it exhibited good QSI activity. Present study illustrated that, the phenolic compounds of ginger and their derivatives form a class of compounds with promising QSI activity. PMID:24767081

Kumar, N Vijendra; Murthy, Pushpa S; Manjunatha, J R; Bettadaiah, B K

2014-09-15

354

Quorum-sensing crosstalk-driven synthetic circuits: from unimodality to trimodality.  

PubMed

Widespread quorum-sensing (QS) enables bacteria to communicate and plays a critical role in controlling bacterial virulence. However, effects of promiscuous QS crosstalk and its implications for gene regulation and cell decision-making remain largely unknown. Here we systematically studied the crosstalk between LuxR/I and LasR/I systems and found that QS crosstalk can be dissected into signal crosstalk and promoter crosstalk. Further investigations using synthetic positive feedback circuits revealed that signal crosstalk significantly decreases a circuit's bistable potential while maintaining unimodality. Promoter crosstalk, however, reproducibly generates complex trimodal responses resulting from noise-induced state transitions and host-circuit interactions. A mathematical model that integrates the circuit's nonlinearity, stochasticity, and host-circuit interactions was developed, and its predictions of conditions for trimodality were verified experimentally. Combining synthetic biology and mathematical modeling, this work sheds light on the complex behaviors emerging from QS crosstalk, which could be exploited for therapeutics and biotechnology. PMID:25455858

Wu, Fuqing; Menn, David J; Wang, Xiao

2014-12-18

355

What role does the quorum-sensing accessory gene regulator system play during Staphylococcus aureus bacteremia?  

PubMed

Staphylococcus aureus is a major cause of bacteremia, which frequently results in serious secondary infections such as infective endocarditis, osteomyelitis, and septic arthritis. The ability of S. aureus to cause such a wide range of infections has been ascribed to its huge armoury of different virulence factors, many of which are under the control of the quorum-sensing accessory gene regulator (Agr) system. However, a significant fraction of S. aureus bacteremia cases are caused by agr-defective isolates, calling into question the role of Agr in invasive staphylococcal infections. This review draws on recent work to define the role of Agr during bacteremia and explain why the loss of this major virulence regulator is sometimes a price worth paying for S. aureus. PMID:25300477

Painter, Kimberley L; Krishna, Aishwarya; Wigneshweraraj, Sivaramesh; Edwards, Andrew M

2014-12-01

356

Anti-quorum sensing activity of selected sponge extracts: a case study of Pseudomonas aeruginosa.  

PubMed

The anti-quorum sensing activities towards the bacterium Pseudomonas aeruginosa PA01 (pyocyanin production, biofilm formation and twitching and flagella motility) of two crude extracts (methanol and acetone) of the freshwater sponge Ochridaspongia rotunda (Arndt, 1937) were evaluated in vitro for the first time. Both extracts demonstrated P. aeruginosa pyocyanin inhibitory activity, reducing its production for 49.90% and 42.44%, respectively. In addition, they both showed higher anti-biofilm activity (48.29% and 53.99%, respectively) than ampicillin (30.84%). Finally, O. rotunda extracts effectively reduced twitching and flagella motility of P. aeruginosa. Taken all together, these results suggest that endemic sponge species from the oldest lake in Europe may offer novel bioactive natural products with promising medicinal potential towards P. aeruginosa infections. PMID:25039944

Pejin, Boris; Talevska, Aleksandra; Ciric, Ana; Glamoclija, Jasmina; Nikolic, Milos; Talevski, Trajce; Sokovic, Marina

2014-01-01

357

Type II quorum sensing regulates virulence in Erwinia carotovora ssp. carotovora.  

PubMed

Quorum sensing is a process by which bacteria communicate using secreted chemical signaling molecules called autoinducers. In this study, the opportunistic plant pathogen Erwinia carotovora ssp. carotovora was observed to secrete type II signaling molecules. A homolog of luxS, the gene required for AI-2 synthesis in Vibrio harveyi, was isolated from the genome of the pathogen. To determine the potential role of AI-2 in virulence, an isogenic luxS- (ECC) mutant was constructed and tested for its ability to cause tissue maceration. The findings reported here demonstrate that the LuxS-dependent signaling affects the progression of disease symptoms during the early stages of infection by modulating the expression of pectinolytic enzymes. PMID:16640578

Laasik, Eve; Andresen, Liis; Mäe, Andres

2006-05-01

358

Production of Tyrosol by Candida albicans Biofilms and Its Role in Quorum Sensing and Biofilm Development?  

PubMed Central

Tyrosol and farnesol are quorum-sensing molecules produced by Candida albicans which accelerate and block, respectively, the morphological transition from yeasts to hyphae. In this study, we have investigated the secretion of tyrosol by C. albicans and explored its likely role in biofilm development. Both planktonic (suspended) cells and biofilms of four C. albicans strains, including three mutants with defined defects in the Efg 1 and Cph 1 morphogenetic signaling pathways, synthesized extracellular tyrosol during growth at 37°C. There was a correlation between tyrosol production and biomass for both cell types. However, biofilm cells secreted at least 50% more tyrosol than did planktonic cells when tyrosol production was related to cell dry weight. The addition of exogenous farnesol to a wild-type strain inhibited biofilm formation by up to 33% after 48 h. Exogenous tyrosol appeared to have no effect, but scanning electron microscopy revealed that tyrosol stimulated hypha production during the early stages (1 to 6 h) of biofilm development. Experiments involving the simultaneous addition of tyrosol and farnesol at different concentrations suggested that the action of farnesol was dominant, and 48-h biofilms formed in the presence of both compounds consisted almost entirely of yeast cells. When biofilm supernatants were tested for their abilities to inhibit or enhance germ tube formation by planktonic cells, the results indicated that tyrosol activity exceeds that of farnesol after 14 h, but not after 24 h, and that farnesol activity increases significantly during the later stages (48 to 72 h) of biofilm development. Overall, our results support the conclusion that tyrosol acts as a quorum-sensing molecule for biofilms as well as for planktonic cells and that its action is most significant during the early and intermediate stages of biofilm formation. PMID:16980403

Alem, Mohammed A. S.; Oteef, Mohammed D. Y.; Flowers, T. Hugh; Douglas, L. Julia

2006-01-01

359

Methylthioadenosine deaminase in an alternative quorum sensing pathway in Pseudomonas aeruginosa.  

PubMed

Pseudomonas aeruginosa possesses an unusual pathway for 5'-methylthioadenosine (MTA) metabolism involving deamination to 5'-methylthioinosine (MTI) followed by N-ribosyl phosphorolysis to hypoxanthine and 5-methylthio-?-d-ribose 1-phosphate. The specific MTI phosphorylase of P. aeruginosa has been reported [Guan, R., Ho, M. C., Almo, S. C., and Schramm, V. L. (2011) Biochemistry 50, 1247-1254], and here we characterize MTA deaminase from P. aeruginosa (PaMTADA). Genomic analysis indicated the PA3170 locus to be a candidate for MTA deaminase (MTADA). Protein encoded by PA3170 was expressed and shown to deaminate MTA with 40-fold greater catalytic efficiency for MTA than for adenosine. The k(cat)/K(m) value of 1.6 × 10(7) M(-1) s(-1) for MTA is the highest catalytic efficiency known for an MTA deaminase. 5'-Methylthiocoformycin (MTCF) is a 4.8 pM transition state analogue for PaMTADA but causes no significant inhibition of human adenosine deaminase or MTA phosphorylase. MTCF is permeable to P. aeruginosa and exhibits an IC(50) of 3 nM on cellular PaMTADA activity. PaMTADA is the only activity in P. aeruginosa extracts to act on MTA. MTA and 5-methylthio-?-d-ribose are involved in quorum sensing pathways; thus, PaMTADA is a potential target for quorum sensing. The crystal structure of PaMTADA in complex with MTCF shows the transition state mimic 8(R)-hydroxyl group in contact with a catalytic site Zn(2+), the 5'-methylthio group in a hydrophobic pocket, and the transition state mimic of the diazepine ring in contact with a catalytic site Glu. PMID:23050701

Guan, Rong; Ho, Meng-Chiao; Fröhlich, Richard F G; Tyler, Peter C; Almo, Steven C; Schramm, Vern L

2012-11-13

360

Vibrio campbellii hmgA-mediated pyomelanization impairs quorum sensing, virulence, and cellular fitness.  

PubMed

Melanization due to the inactivation of the homogentisate-1,2-dioxygenase gene (hmgA) has been demonstrated to increase stress resistance, persistence, and virulence in some bacterial species but such pigmented mutants have not been observed in pathogenic members of the Vibrio Harveyi clade. In this study, we used Vibrio campbellii ATCC BAA-1116 as model organism to understand how melanization affected cellular phenotype, metabolism, and virulence. An in-frame deletion of the hmgA gene resulted in the overproduction of a pigment in cell culture supernatants and cellular membranes that was identified as pyomelanin. Unlike previous demonstrations in Vibrio cholerae, Burkholderia cepacia, and Pseudomonas aeruginosa, the pigmented V. campbellii mutant did not show increased UV resistance and was found to be ~2.7 times less virulent than the wild type strain in Penaeus monodon shrimp virulence assays. However, the extracted pyomelanin pigment did confer a higher resistance to oxidative stress when incubated with wild type cells. Microarray-based transcriptomic analyses revealed that the hmgA gene deletion and subsequent pyomelanin production negatively effected the expression of 129 genes primarily involved in energy production, amino acid, and lipid metabolism, and protein translation and turnover. This transcriptional response was mediated in part by an impairment of the quorum sensing regulon as transcripts of the quorum sensing high cell density master regulator LuxR and other operonic members of this regulon were significantly less abundant in the hmgA mutant. Taken together, the results suggest that the pyomelanization of V. campbellii sufficiently impairs the metabolic activities of this organism and renders it less fit and virulent than its isogenic wild type strain. PMID:24376440

Wang, Zheng; Lin, Baochuan; Mostaghim, Anahita; Rubin, Robert A; Glaser, Evan R; Mittraparp-Arthorn, Pimonsri; Thompson, Janelle R; Vuddhakul, Varaporn; Vora, Gary J

2013-01-01

361

raiIR Genes Are Part of a Quorum-Sensing Network Controlled by cinI and cinR in Rhizobium leguminosarum  

Microsoft Academic Search

Analysis of N-acyl-L-homoserine lactones (AHLs) produced by Rhizobium leguminosarum bv. viciae indicated that there may be a network of quorum-sensing regulatory systems producing multiple AHLs in this species. Using a strain lacking a symbiosis plasmid, which carries some of the quorum-sensing genes, we isolated mutations in two genes (raiI and raiR) that are required for production of AHLs. The raiIR

F. Wisniewski-Dye; J. Jones; S. R. Chhabra; J. A. Downie

2002-01-01

362

Quorum-sensing antagonist ( 5Z )-4-bromo-5-(bromomethylene)-3-butyl-2( 5H )-furanone influences siderophore biosynthesis in Pseudomonas putida and Pseudomonas aeruginosa  

Microsoft Academic Search

Siderophore synthesis of Pseudomonas putida F1 was found to be regulated by quorum sensing since normalized siderophore production (per cell) increased 4.2-fold with cell density after the cells entered middle exponential phase; similarly, normalized siderophore concentrations in Pseudomonas aeruginosa JB2 increased 28-fold, and a 5.5-fold increase was seen for P. aeruginosa PAO1. Further evidence of the link between quorum sensing

Dacheng Ren; Rongjun Zuo; Thomas K. Wood

2005-01-01

363

Microbial growth and quorum sensing antagonist activities of herbal plants extracts.  

PubMed

Antimicrobial and antiquorum sensing (AQS) activities of fourteen ethanolic extracts of different parts of eight plants were screened against four Gram-positive, five Gram-negative bacteria and four fungi. Depending on the plant part extract used and the test microorganism, variable activities were recorded at 3 mg per disc. Among the Grampositive bacteria tested, for example, activities of Laurus nobilis bark extract ranged between a 9.5 mm inhibition zone against Bacillus subtilis up to a 25 mm one against methicillin resistant Staphylococcus aureus. Staphylococcus aureus and Aspergillus fumigatus were the most susceptible among bacteria and fungi tested towards other plant parts. Of interest is the tangible antifungal activity of a Tecoma capensis flower extract, which is reported for the first time. However, minimum inhibitory concentrations (MIC's) for both bacteria and fungi were relatively high (0.5-3.0 mg). As for antiquorum sensing activity against Chromobacterium violaceum, superior activity (>17 mm QS inhibition) was associated with Sonchus oleraceus and Laurus nobilis extracts and weak to good activity (8-17 mm) was recorded for other plants. In conclusion, results indicate the potential of these plant extracts in treating microbial infections through cell growth inhibition or quorum sensing antagonism, which is reported for the first time, thus validating their medicinal use. PMID:19783935

Al-Hussaini, Reema; Mahasneh, Adel M

2009-01-01

364

A case study on chemical defense based on quorum sensing: antibacterial activity of sponge-associated bacterium Pseudoalteromonas sp. NJ6-3-1 induced by quorum sensing mechanisms  

Microsoft Academic Search

A case study to investigate the relationship between antibacterial activity and quorum sensing mechanisms was carried out\\u000a on a sponge-associated bacterium with remarkable biological activities: Pseudoalteromonas sp. NJ6-3-1. The dependence of active substance production on cell density was studied under various growth conditions. Bacteria\\u000a NJ6-3-1 was found to start producing antibacterial compounds only when cell density reached the threshold value

Xiuchun Guo; Li Zheng; Wenhui Zhou; Zhisong Cui; Ping Han; Li Tian; Xiaoru Wang

2011-01-01

365

Individual and Combined Roles of the Master Regulators AphA and LuxR in Control of the Vibrio harveyi Quorum-Sensing Regulon  

PubMed Central

Bacteria use a chemical communication process called quorum sensing to control transitions between individual and group behaviors. In the Vibrio harveyi quorum-sensing circuit, two master transcription factors, AphA and LuxR, coordinate the quorum-sensing response. Here we show that AphA regulates 167 genes, LuxR regulates 625 genes, and they coregulate 77 genes. LuxR strongly controls genes at both low cell density and high cell density, suggesting that it is the major quorum-sensing regulator. In contrast, AphA is absent at high cell density and acts to fine-tune quorum-sensing gene expression at low cell density. We examined two loci as case studies of coregulation by AphA and LuxR. First, AphA and LuxR directly regulate expression of the genes encoding the quorum-regulatory small RNAs Qrr2, Qrr3, and Qrr4, the consequence of which is a specifically timed transition between the individual and the group life-styles. Second, AphA and LuxR repress type III secretion system genes but at different times and to different extents. The consequence of this regulation is that type III secretion is restricted to a peak at mid-cell density. Thus, the asymmetric production of AphA and LuxR coupled with differences in their strengths and timing of target gene regulation generate a precise temporal pattern of gene expression. PMID:23204455

van Kessel, Julia C.; Rutherford, Steven T.; Shao, Yi; Utria, Alan F.

2013-01-01

366

Inhibition of biofilm development of uropathogens by curcumin - an anti-quorum sensing agent from Curcuma longa.  

PubMed

Urinary tract infection is caused primarily by the quorum sensing (QS)-dependent biofilm forming ability of uropathogens. In the present investigation, an anti-quorum sensing (anti-QS) agent curcumin from Curcuma longa (turmeric) was shown to inhibit the biofilm formation of uropathogens, such as Escherichia coli, Pseudomonas aeruginosa PAO1, Proteus mirabilis and Serratia marcescens, possibly by interfering with their QS systems. The antibiofilm potential of curcumin on uropathogens as well as its efficacy in disturbing the mature biofilms was examined under light microscope and confocal laser scanning microscope. The treatment with curcumin was also found to attenuate the QS-dependent factors, such as exopolysaccharide production, alginate production, swimming and swarming motility of uropathogens. Furthermore, it was documented that curcumin enhanced the susceptibility of a marker strain and uropathogens to conventional antibiotics. PMID:24262582

Packiavathy, Issac Abraham Sybiya Vasantha; Priya, Selvam; Pandian, Shunmugiah Karutha; Ravi, Arumugam Veera

2014-04-01

367

A LuxR\\/LuxI-Type Quorum-Sensing System in a Plant Bacterium, Mesorhizobium tianshanense, Controls Symbiotic Nodulation  

Microsoft Academic Search

Received 22 November 2005\\/Accepted 7 December 2005 The ability of rhizobia to symbiotically fix nitrogen from the atmosphere when forming nodules on their plant hosts requires various signal transduction pathways. LuxR-LuxI-type quorum-sensing systems have been shown to be one of the players in a number of rhizobium species. In this study, we found that Mesorhizobium tianshanense, a moderate-growth Rhizobium that

Huiming Zheng; Zengtao Zhong; Xin Lai; Wen-Xin Chen; Shunpeng Li; Jun Zhu

2006-01-01

368

The natural antimicrobial carvacrol inhibits quorum sensing in Chromobacterium violaceum and reduces bacterial biofilm formation at sub-lethal concentrations.  

PubMed

The formation of biofilm by bacteria confers resistance to biocides and presents problems in medical and veterinary clinical settings. Here we report the effect of carvacrol, one of the major antimicrobial components of oregano oil, on the formation of biofilms and its activity on existing biofilms. Assays were carried out in polystyrene microplates to observe (a) the effect of 0-0.8 mM carvacrol on the formation of biofilms by selected bacterial pathogens over 24 h and (b) the effect of 0-8 mM carvacrol on the stability of pre-formed biofilms. Carvacrol was able to inhibit the formation of biofilms of Chromobacterium violaceum ATCC 12472, Salmonella enterica subsp. Typhimurium DT104, and Staphylococcus aureus 0074, while it showed no effect on formation of Pseudomonas aeruginosa (field isolate) biofilms. This inhibitory effect of carvacrol was observed at sub-lethal concentrations (<0.5 mM) where no effect was seen on total bacterial numbers, indicating that carvacrol's bactericidal effect was not causing the observed inhibition of biofilm formation. In contrast, carvacrol had (up to 8 mM) very little or no activity against existing biofilms of the bacteria described, showing that formation of the biofilm also confers protection against this compound. Since quorum sensing is an essential part of biofilm formation, the effect of carvacrol on quorum sensing of C. violaceum was also studied. Sub-MIC concentrations of carvacrol reduced expression of cviI (a gene coding for the N-acyl-L-homoserine lactone synthase), production of violacein (pigmentation) and chitinase activity (both regulated by quorum sensing) at concentrations coinciding with carvacrol's inhibiting effect on biofilm formation. These results indicate that carvacrol's activity in inhibition of biofilm formation may be related to the disruption of quorum sensing. PMID:24691035

Burt, Sara A; Ojo-Fakunle, Victoria T A; Woertman, Jenifer; Veldhuizen, Edwin J A

2014-01-01

369

Quorum Sensing Influences Vibrio harveyi Growth Rates in a Manner Not Fully Accounted For by the Marker Effect of Bioluminescence  

Microsoft Academic Search

BackgroundThe light-emitting Vibrios provide excellent material for studying the interaction of cellular communication with growth rate because bioluminescence is a convenient marker for quorum sensing. However, the use of bioluminescence as a marker is complicated because bioluminescence itself may affect growth rate, e.g. by diverting energy.Methodology\\/Principal FindingsThe marker effect was explored via growth rate studies in isogenic Vibrio harveyi (Vh)

Zeena E. Nackerdien; Alexander Keynan; Bonnie L. Bassler; Joshua Lederberg; David S. Thaler; Julian Rutherford

2008-01-01

370

The Quorum-Sensing Negative Regulator RsaL of Pseudomonas aeruginosa Binds to the lasI Promoter  

Microsoft Academic Search

A mutation in the rsaL gene of Pseudomonas aeruginosa produces dramatically higher amounts of N-acyl homoserine lactone with respect to the wild type, highlighting the key role of this negative regulator in controlling quorum sensing (QS) in this opportunistic pathogen. The DNA binding site of the RsaL protein on the rsaL-lasI bidirectional promoter partially overlaps the binding site of the

Giordano Rampioni; Iris Bertani; Elisabetta Zennaro; Fabio Polticelli; Vittorio Venturi; Livia Leoni

2006-01-01

371

The Natural Antimicrobial Carvacrol Inhibits Quorum Sensing in Chromobacterium violaceum and Reduces Bacterial Biofilm Formation at Sub-Lethal Concentrations  

PubMed Central

The formation of biofilm by bacteria confers resistance to biocides and presents problems in medical and veterinary clinical settings. Here we report the effect of carvacrol, one of the major antimicrobial components of oregano oil, on the formation of biofilms and its activity on existing biofilms. Assays were carried out in polystyrene microplates to observe (a) the effect of 0–0.8 mM carvacrol on the formation of biofilms by selected bacterial pathogens over 24 h and (b) the effect of 0–8 mM carvacrol on the stability of pre-formed biofilms. Carvacrol was able to inhibit the formation of biofilms of Chromobacterium violaceum ATCC 12472, Salmonella enterica subsp. Typhimurium DT104, and Staphylococcus aureus 0074, while it showed no effect on formation of Pseudomonas aeruginosa (field isolate) biofilms. This inhibitory effect of carvacrol was observed at sub-lethal concentrations (<0.5 mM) where no effect was seen on total bacterial numbers, indicating that carvacrol's bactericidal effect was not causing the observed inhibition of biofilm formation. In contrast, carvacrol had (up to 8 mM) very little or no activity against existing biofilms of the bacteria described, showing that formation of the biofilm also confers protection against this compound. Since quorum sensing is an essential part of biofilm formation, the effect of carvacrol on quorum sensing of C. violaceum was also studied. Sub-MIC concentrations of carvacrol reduced expression of cviI (a gene coding for the N-acyl-L-homoserine lactone synthase), production of violacein (pigmentation) and chitinase activity (both regulated by quorum sensing) at concentrations coinciding with carvacrol's inhibiting effect on biofilm formation. These results indicate that carvacrol's activity in inhibition of biofilm formation may be related to the disruption of quorum sensing. PMID:24691035

Burt, Sara A.; Ojo-Fakunle, Victoria T. A.; Woertman, Jenifer; Veldhuizen, Edwin J. A.

2014-01-01

372

5 Diggle, S.P. et al. (2007) Evolutionary theory of bacterial quorum sensing: when is a signal not a signal? Philos. Trans. R. Soc. Lond. B  

E-print Network

5 Diggle, S.P. et al. (2007) Evolutionary theory of bacterial quorum sensing: when is a signal.10.003 Available online 18 November 2008 Letters Response Response to Goldman and Brown: Making sense of microbial biology' [1], Goldman and Brown [2] encourage a synthesis that makes complete sense ­ the field

Arnold, Frances H.

373

The Transcriptional Regulator VqmA Increases Expression of the Quorum-Sensing Activator HapR in Vibrio cholerae  

PubMed Central

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. PMID:16547031

Liu, Zhi; Hsiao, Ansel; Joelsson, Adam; Zhu, Jun

2006-01-01

374

Influence of the AgrC-AgrA Complex on the Response Time of Staphylococcus aureus Quorum Sensing  

PubMed Central

The Staphylococcus aureus agr quorum-sensing system plays a major role in the transition from the persistent to the virulent phenotype. S. aureus agr type I to IV strains are characterized by mutations in the sensor domain of the histidine kinase AgrC and differences in the sequences of the secreted autoinducing peptides (AIP). Here we demonstrate that interactions between the cytosolic domain of AgrC (AgrCCyto) and the response regulator domain of AgrA (AgrARR) dictate the spontaneity of the cellular response to AIP stimuli. The crystal structure of AgrCCyto provided a basis for a mechanistic model of AgrC-AgrA interactions. This model enabled an analysis of the biochemical and biophysical parameters of AgrC-AgrA interactions in the context of the conformational features of the AgrC-AgrA complex. This analysis revealed distinct sequence and conformational features that determine the affinity, specificity, and kinetics of the phosphotransfer reaction. This step, which governs the response time for transcriptional reengineering triggered by an AIP stimulus, is independent of the agr type and similar for agonist and antagonist stimuli. These experimental data could serve as a basis on which to validate simulations of the quorum-sensing response and for strategies that employ the agr quorum-sensing system to combat biofilm formation in S. aureus infections. PMID:24858185

Srivastava, Sandeep K.; Rajasree, Kalagiri; Fasim, Aneesa; Arakere, Gayathri

2014-01-01

375

Degradation of Bacterial Quorum Sensing Signaling Molecules by the Microscopic Yeast Trichosporon loubieri Isolated from Tropical Wetland Waters  

PubMed Central

Proteobacteria produce N-acylhomoserine lactones as signaling molecules, which will bind to their cognate receptor and activate quorum sensing-mediated phenotypes in a population-dependent manner. Although quorum sensing signaling molecules can be degraded by bacteria or fungi, there is no reported work on the degradation of such molecules by basidiomycetous yeast. By using a minimal growth medium containing N-3-oxohexanoylhomoserine lactone as the sole source of carbon, a wetland water sample from Malaysia was enriched for microbial strains that can degrade N-acylhomoserine lactones, and consequently, a basidiomycetous yeast strain WW1C was isolated. Morphological phenotype and molecular analyses confirmed that WW1C was a strain of Trichosporon loubieri. We showed that WW1C degraded AHLs with N-acyl side chains ranging from 4 to 10 carbons in length, with or without oxo group substitutions at the C3 position. Re-lactonisation bioassays revealed that WW1C degraded AHLs via a lactonase activity. To the best of our knowledge, this is the first report of degradation of N-acyl-homoserine lactones and utilization of N-3-oxohexanoylhomoserine as carbon and nitrogen source for growth by basidiomycetous yeast from tropical wetland water; and the degradation of bacterial quorum sensing molecules by an eukaryotic yeast. PMID:24072030

Wong, Cheng-Siang; Koh, Chong-Lek; Sam, Choon-Kook; Chen, Jian Woon; Chong, Yee Meng; Yin, Wai-Fong; Chan, Kok-Gan

2013-01-01

376

Quorum Sensing Contributes to Activated IgM-Secreting B Cell Homeostasis  

PubMed Central

Maintenance of plasma IgM levels is critical for immune system function and homeostasis in humans and mice. However, the mechanisms that control homeostasis of the activated IgM-secreting B cells are unknown. After adoptive transfer into immune-deficient hosts, B lymphocytes expand poorly, but fully reconstitute the pool of natural IgM-secreting cells and circulating IgM levels. By using sequential cell transfers and B cell populations from several mutant mice, we were able to identify novel mechanisms regulating the size of the IgM-secreting B cell pool. Contrary to previous mechanisms described regulating homeostasis, which involve competition for the same niche by cells having overlapping survival requirements, homeostasis of the innate IgM-secreting B cell pool is also achieved when B cell populations are able to monitor the number of activated B cells by detecting their secreted products. Notably, B cell populations are able to assess the density of activated B cells by sensing their secreted IgG. This process involves the Fc?RIIB, a low-affinity IgG receptor that is expressed on B cells and acts as a negative regulator of B cell activation, and its intracellular effector the inositol phosphatase SHIP. As a result of the engagement of this inhibitory pathway, the number of activated IgM-secreting B cells is kept under control. We hypothesize that malfunction of this quorum-sensing mechanism may lead to uncontrolled B cell activation and autoimmunity. PMID:23209322

Montaudouin, Caroline; Anson, Marie; Hao, Yi; Duncker, Susanne V.; Fernandez, Tahia; Gaudin, Emmanuelle; Ehrenstein, Michael; Kerr, William G.; Colle, Jean-Hervé; Bruhns, Pierre; Daëron, Marc; Freitas, António A.

2013-01-01

377

Quorum sensing contributes to activated IgM-secreting B cell homeostasis.  

PubMed

Maintenance of plasma IgM levels is critical for immune system function and homeostasis in humans and mice. However, the mechanisms that control homeostasis of the activated IgM-secreting B cells are unknown. After adoptive transfer into immune-deficient hosts, B lymphocytes expand poorly, but fully reconstitute the pool of natural IgM-secreting cells and circulating IgM levels. By using sequential cell transfers and B cell populations from several mutant mice, we were able to identify novel mechanisms regulating the size of the IgM-secreting B cell pool. Contrary to previous mechanisms described regulating homeostasis, which involve competition for the same niche by cells having overlapping survival requirements, homeostasis of the innate IgM-secreting B cell pool is also achieved when B cell populations are able to monitor the number of activated B cells by detecting their secreted products. Notably, B cell populations are able to assess the density of activated B cells by sensing their secreted IgG. This process involves the Fc?RIIB, a low-affinity IgG receptor that is expressed on B cells and acts as a negative regulator of B cell activation, and its intracellular effector the inositol phosphatase SHIP. As a result of the engagement of this inhibitory pathway, the number of activated IgM-secreting B cells is kept under control. We hypothesize that malfunction of this quorum-sensing mechanism may lead to uncontrolled B cell activation and autoimmunity. PMID:23209322

Montaudouin, Caroline; Anson, Marie; Hao, Yi; Duncker, Susanne V; Fernandez, Tahia; Gaudin, Emmanuelle; Ehrenstein, Michael; Kerr, William G; Colle, Jean-Hervé; Bruhns, Pierre; Daëron, Marc; Freitas, António A

2013-01-01

378

Functional Analysis of the Quorum-Sensing Streptococcal Invasion Locus (sil)  

PubMed Central

Group A streptococcus (GAS) causes a wide variety of human diseases, and at the same time, GAS can also circulate without producing symptoms, similar to its close commensal relative, group G streptococcus (GGS). We previously identified, by transposon-tagged mutagenesis, the streptococcal invasion locus (sil). sil is a quorum-sensing regulated locus which is activated by the autoinducer peptide SilCR through the two-component system SilA-SilB. Here we characterize the DNA promoter region necessary for SilA-mediated activation. This site is composed of two direct repeats of 10 bp, separated by a spacer of 11 bp. Fusion of this site to gfp allowed us to systematically introduce single-base substitutions in the repeats region and to assess the relative contribution of various positions to promoter strength. We then developed an algorithm giving different weights to these positions, and performed a chromosome-wide bioinformatics search which was validated by transcriptome analysis. We identified 13 genes, mostly bacteriocin related, that are directly under the control of SilA. Having developed the ability to quantify SilCR signaling via GFP accumulation prompted us to search for GAS and GGS strains that sense and produce SilCR. While the majority of GAS strains lost sil, all GGS strains examined still possess the locus and ?63% are able to respond to exogenously added SilCR. By triggering the autoinduction circle using a minute concentration of synthetic SilCR, we identified GAS and GGS strains that are capable of sensing and naturally producing SilCR, and showed that SilCR can be sensed across these streptococci species. These findings suggest that sil may be involved in colonization and establishment of commensal host-bacterial relationships. PMID:19893632

Belotserkovsky, Ilia; Baruch, Moshe; Peer, Asaf; Dov, Eran; Ravins, Miriam; Mishalian, Inbal; Persky, Merav; Smith, Yoav; Hanski, Emanuel

2009-01-01

379

The Pseudomonas aeruginosa Lectins PAIL and PA-IIL Are Controlled by Quorum Sensing and by RpoS  

Microsoft Academic Search

In Pseudomonas aeruginosa, many exoproduct virulence determinants are regulated via a hierarchical quo- rum-sensing cascade involving the transcriptional regulators LasR and RhlR and their cognate activators, N-(3-oxododecanoyl)-L-homoserine lactone (3O-C12-HSL) and N-butanoyl-L-homoserine lactone (C4-HSL). In this paper, we demonstrate that the cytotoxic lectins PA-IL and PA-IIL are regulated via quorum sensing. Using immunoblot analysis, the production of both lectins was found

KLAUS WINZER; COLIN FALCONER; NACHMAN C. GARBER; STEPHEN P. DIGGLE; MIGUEL CAMARA; PAUL WILLIAMS

2000-01-01

380

Microarray Analysis of Pseudomonas aeruginosa Quorum-Sensing Regulons: Effects of Growth Phase and Environment†  

PubMed Central

Bacterial communication via quorum sensing (QS) has been reported to be important in the production of virulence factors, antibiotic sensitivity, and biofilm development. Two QS systems, known as the las and rhl systems, have been identified previously in the opportunistic pathogen Pseudomonas aeruginosa. High-density oligonucleotide microarrays for the P. aeruginosa PAO1 genome were used to investigate global gene expression patterns modulated by QS regulons. In the initial experiments we focused on identifying las and/or rhl QS-regulated genes using a QS signal generation-deficient mutant (PAO-JP2) that was cultured with and without added exogenous autoinducers [N-(3-oxododecanoyl) homoserine lactone and N-butyryl homoserine lactone]. Conservatively, 616 genes showed statistically significant differential expression (P ? 0.05) in response to the exogenous autoinducers and were classified as QS regulated. A total of 244 genes were identified as being QS regulated at the mid-logarithmic phase, and 450 genes were identified as being QS regulated at the early stationary phase. Most of the previously reported QS-promoted genes were confirmed, and a large number of additional QS-promoted genes were identified. Importantly, 222 genes were identified as being QS repressed. Environmental factors, such as medium composition and oxygen availability, eliminated detection of transcripts of many genes that were identified as being QS regulated. PMID:12644477

Wagner, Victoria E.; Bushnell, Daniel; Passador, Luciano; Brooks, Andrew I.; Iglewski, Barbara H.

2003-01-01

381

Inhibition of quorum sensing in gram-negative bacteria by alkylamine-modified cyclodextrins.  

PubMed

N-Acylhomoserine lactones (AHLs) are used as quorum-sensing (QS) signals by gram-negative bacteria. We have reported that the cyclic oligosaccharides known as cyclodextrins (CDs) form inclusion complexes with AHLs and disrupt QS signaling. In this study, a series of CD derivatives were designed and synthesized to improve the QS inhibitory activity over that of native CDs. The production of the red pigment prodigiosin by Serratia marcescens AS-1, which is regulated by AHL-mediated QS, was drastically decreased by adding 10 mg/ml 6-alkylacylamino-?-CD with an alkyl chain ranging from C7 to C12. An improvement in the QS inhibitory activity was also observed for 6-alkylamino-?- or ?-CDs and 2-alkylamino-CDs. Furthermore, 6,6'-dioctylamino-?-CD, which contains two octylamino groups, exhibited greater inhibitory activity than 6-monooctylamino-?-CD. The synthesized CD derivatives also had strong inhibitory effects on QS by other gram-negative bacteria, including Chromobacterium violaceum and Pseudomonas aeruginosa. The synthetic alkylamine-modified CD derivatives had higher equilibrium binding constants for binding with AHL than the native CDs did, consistent with the improved QS inhibition. ¹H NMR measurements suggested that the alkyl side chains of 6-alkylacylamino-?-CDs with alkyl chains up to 6 carbon atoms long could form self-inclusion complexes with the CD unit. PMID:23466297

Morohoshi, Tomohiro; Tokita, Kazuho; Ito, Satoshi; Saito, Yuki; Maeda, Saki; Kato, Norihiro; Ikeda, Tsukasa

2013-08-01

382

Inhibition of quorum sensing regulated biofilm formation in Serratia marcescens causing nosocomial infections.  

PubMed

Serratia marcescens is an opportunistic pathogen causing severe urinary tract infections in hospitalized individuals. Infections of S. marcescens are of great concern because of its increasing resistance towards conventional antibiotics. Quorum sensing (QS)-a cell to cell communication-system of S. marcescens acts as a global regulator of almost all the virulence factors and majorly its biofilm formation. Since, the QS system of S. marcescens directly accords to its pathogenesis, targeting QS system will provide an improved strategy to combat drug resistant pathogens. In the present study, QS system of S. marcescens has been used as target and its inhibition has been studied upon exposure to bioactives from coral associated bacteria (CAB). This study also emphasises the potential of CAB in producing bioactive agents with anti-QS and antibiofilm properties. Two CAB isolates CAB 23 and 41 have shown to inhibit biofilm formation and the production of QS dependent virulence factors like prodigiosin, protease, lipase and swarming motility. The study, on the whole explicates the potential of QS system as a target to treat drug resistant bacterial infections. PMID:22487181

Bakkiyaraj, Dhamodharan; Sivasankar, Chandran; Pandian, Shunmugiah Karutha

2012-05-01

383

A New Transcriptional Repressor of the Pseudomonas aeruginosa Quorum Sensing Receptor Gene lasR  

PubMed Central

Pseudomonas aeruginosa pathogenic potential is controlled via multiple regulatory pathways, including three quorum sensing (QS) systems. LasR is a key QS signal receptor since it acts as a global transcriptional regulator required for optimal expression of main virulence factors. P. aeruginosa modulates the QS response by integrating this cell density-dependent circuit to environmental and metabolic cues. Hence, QS also controls the adaptation to challenging environmental niches, such as infection sites. However, little is known about the molecular mechanisms connecting QS and other signalling pathways. In this work, DNA-affinity chromatography was used to identify new lasR transcriptional regulators. This approach led to the identification and functional characterization of the TetR-like transcriptional repressor PA3699. This protein was purified and shown to directly bind to the lasR promoter region in vitro. The induction of PA3699 expression in P. aeruginosa PAO1 cultures repressed lasR promoter activity and the production of LasR-dependent virulence factors, such as elastase, pyocyanin, and proteases. These findings suggest a role for PA3699 in P. aeruginosa pathogenicity. P. aeruginosa genome encodes at least 38 TetR-family proteins, and PA3699 is the eighth member of this group functionally characterized so far and the first one shown to bind the lasR promoter in vitro. PMID:23861975

Longo, Francesca; Rampioni, Giordano; Bondì, Roslen; Imperi, Francesco; Fimia, Gian Maria; Visca, Paolo; Zennaro, Elisabetta; Leoni, Livia

2013-01-01

384

Global position analysis of the Pseudomonas aeruginosa quorum-sensing transcription factor LasR  

PubMed Central

Summary In Pseudomonas aeruginosa quorum sensing (QS), the transcriptional regulator LasR controls the expression of more than 300 genes. Several of these genes are activated indirectly via a second, subordinate QS regulator, RhlR. Conserved sequence elements upstream of individual other genes have been shown to bind LasR in vitro. To comprehensively identify all regions that are bound by LasR in vivo, we employed chromatin immunoprecipitation in conjunction with microarray analysis. We identified 35 putative promoter regions that direct the expression of up to 74 genes. In vitro DNA binding studies allowed us to distinguish between cooperative and non-cooperative LasR binding sites, and allowed us to build consensus sequences according to the mode of binding. Five promoter regions were not previously recognized as QS-controlled. Two of the associated transcript units encode proteins involved in the cold-shock response and in Psl exopolysaccharide synthesis, respectively. The LasR regulon includes seven genes encoding transcriptional regulators, while secreted factors and secretion machinery are the most overrepresented functional categories overall. This supports the notion that the core function of LasR is to coordinate the production of extracellular factors, although many of its effects on global gene expression are likely mediated indirectly by regulatory genes under its control. PMID:19682264

Gilbert, Kerrigan B.; Kim, Tae Hoon; Gupta, Rashmi; Greenberg, E. P.; Schuster, Martin

2009-01-01

385

Crystal Structure of the Vibrio cholerae Quorum-Sensing Regulatory Protein HapR?  

PubMed Central

Quorum sensing in Vibrio cholerae involves signaling between two-component sensor protein kinases and the response regulator LuxO to control the expression of the master regulator HapR. HapR, in turn, plays a central role in regulating a number of important processes, such as virulence gene expression and biofilm formation. We have determined the crystal structure of HapR to 2.2-Å resolution. Its structure reveals a dimeric, two-domain molecule with an all-helical structure that is strongly conserved with members of the TetR family of transcriptional regulators. The N-terminal DNA-binding domain contains a helix-turn-helix DNA-binding motif and alteration of certain residues in this domain completely abolishes the ability of HapR to bind to DNA, alleviating repression of both virulence gene expression and biofilm formation. The C-terminal dimerization domain contains a unique solvent accessible tunnel connected to an amphipathic cavity, which by analogy with other TetR regulators, may serve as a binding pocket for an as-yet-unidentified ligand. PMID:17526705

De Silva, Rukman S.; Kovacikova, Gabriela; Lin, Wei; Taylor, Ronald K.; Skorupski, Karen; Kull, F. Jon

2007-01-01

386

Crystal structure of the Vibrio cholerae quorum-sensing regulatory protein HapR.  

PubMed

Quorum sensing in Vibrio cholerae involves signaling between two-component sensor protein kinases and the response regulator LuxO to control the expression of the master regulator HapR. HapR, in turn, plays a central role in regulating a number of important processes, such as virulence gene expression and biofilm formation. We have determined the crystal structure of HapR to 2.2-A resolution. Its structure reveals a dimeric, two-domain molecule with an all-helical structure that is strongly conserved with members of the TetR family of transcriptional regulators. The N-terminal DNA-binding domain contains a helix-turn-helix DNA-binding motif and alteration of certain residues in this domain completely abolishes the ability of HapR to bind to DNA, alleviating repression of both virulence gene expression and biofilm formation. The C-terminal dimerization domain contains a unique solvent accessible tunnel connected to an amphipathic cavity, which by analogy with other TetR regulators, may serve as a binding pocket for an as-yet-unidentified ligand. PMID:17526705

De Silva, Rukman S; Kovacikova, Gabriela; Lin, Wei; Taylor, Ronald K; Skorupski, Karen; Kull, F Jon

2007-08-01

387

Regulatory small RNAs circumvent the conventional quorum sensing pathway in pandemic Vibrio cholerae  

PubMed Central

Using a process called quorum sensing (QS), bacteria communicate with extracellular signal molecules called autoinducers (AIs). Response to AIs allows bacteria to coordinate gene expression on a population-wide scale and thereby carry out particular behaviors in unison, much like multicellular organisms. In Vibrio cholerae El Tor, the etiological agent of the current cholera pandemic, AI information is transduced internally through a phosphorelay circuit that impinges on the transcription of multiple small regulatory RNAs (sRNAs). These RNAs base-pair with, and repress the translation of, the mRNA encoding the master transcriptional regulator HapR. In V. cholerae, HapR controls virulence factor expression and biofilm formation. Here we identify a sRNA-dependent, HapR-independent QS pathway in which the sRNAs base-pair with a new target mRNA and activate translation by preventing formation of a translation-inhibiting stem-loop structure. We show that the classical V. cholerae strain, which caused previous pandemics and is reportedly incapable of QS because of a nonfunctional HapR, nonetheless exhibits QS-controlled gene expression through this new HapR-independent pathway. PMID:17556542

Hammer, Brian K.; Bassler, Bonnie L.

2007-01-01

388

Effects of 14-Alpha-Lipoyl Andrographolide on Quorum Sensing in Pseudomonas aeruginosa  

PubMed Central

In Pseudomonas aeruginosa, the quorum-sensing (QS) system is closely related to biofilm formation. We previously demonstrated that 14-alpha-lipoyl andrographolide (AL-1) has synergistic effects on antibiofilm and antivirulence factors (pyocyanin and exopolysaccharide) of P. aeruginosa when combined with conventional antibiotics, while it has little inhibitory effect on its growth. However, its molecular mechanism remains elusive. Here we investigated the effect of AL-1 on QS systems, especially the Las and Rhl systems. This investigation showed that AL-1 can inhibit LasR–3-oxo-C12-homoserine lactone (HSL) interactions and repress the transcriptional level of QS-regulated genes. Reverse transcription (RT)-PCR data showed that AL-1 significantly reduced the expression levels of lasR, lasI, rhlR, and rhlI in a dose-dependent manner. AL-1 not only decreased the expression level of Psl, which is positively regulated by the Las system, but also increased the level of secretion of ExoS, which is negatively regulated by the Rhl system, indicating that AL-1 has multiple effects on both the Las and Rhl systems. It is no wonder that AL-1 showed synergistic effects with other antimicrobial agents in the treatment of P. aeruginosa infections. PMID:22802260

Ma, Li; Liu, Xiangyang; Liang, Haihua; Che, Yizhou; Chen, Caixia; Dai, Huanqin; Yu, Ke; Liu, Mei; Ma, Luyan; Yang, Ching-Hong; Song, Fuhang

2012-01-01

389

Regulated proteolysis of Candida albicans Ras1 is involved in morphogenesis and quorum sensing regulation  

PubMed Central

Summary In Candida albicans, a fungal pathogen, the small G-protein Ras1 regulates many important behaviors including white-opaque switching, biofilm formation, and the induction and maintenance of hyphal growth. Like other Ras proteins, Ras1 is activated upon guanine triphosphate binding, and its activity is further modulated by post-translational lipid modifications. Here, we report that the levels of membrane-associated, full-length Ras1 were higher in hyphae than in yeast, and that yeast contained a shorter, soluble Ras1 species that resulted from cleavage. Deletion of the putative cleavage site led to more rapid induction of hyphal growth and delayed hypha-to-yeast transitions. The cleaved Ras1 species was less able to activate its effector, adenylate cyclase (Cyr1), unless tethered to the membrane by a heterologous membrane-targeting domain. Ras1 cleavage was repressed by cAMP-signaling, indicating the presence of a positive feedback loop in which Cyr1 and cAMP influence Ras1. The C. albicans quorum sensing molecule farnesol, which inhibits Cyr1 and represses filamentation, caused an increase in the fraction of Ras1 in the cleaved form, particularly in nascent yeast formed from hyphae. This newly recognized mode of Ras regulation may control C. albicans Ras1 activity in important ways. PMID:23692372

Piispanen, Amy; Grahl, Nora; Hollomon, Jeffrey M.; Hogan, Deborah A.

2013-01-01

390

2,5-Piperazinedione inhibits quorum sensing-dependent factor production in Pseudomonas aeruginosa PAO1.  

PubMed

The effects of 2,5-piperazinedione in reducing the production of quorum sensing (QS)-dependent factors in Pseudomonas aeruginosa PAO1 were assessed both in vitro and in vivo. 2,5-Piperazinedione exhibited a 69% reduction in the azocasein-degrading proteolytic activity and a 48% reduction in the elastolytic activity of PAO1. Further, it showed 85% and 96% reduction in the production of pyocyanin and extracellular polymeric substances (EPS) of PAO1, respectively. In the swimming inhibition assay, 2,5-piperazinedione-treated PAO1 cells exhibited poor swimming motility in swim agar medium. In the in vivo analysis, an enhanced survival of PAO1-preinfected Caenorhabditis elegans was observed after treatment with 2,5-piperazinedione. Regarding the mode of action, in the molecular docking analysis, 2,5-piperazinedione interacts with the amino acid residue of the LasR receptor protein required for binding the natural ligand N -3-oxododecanoyl-l-homoserine lactone (3-oxo-C12-HSL). This demonstrates the probability of 2,5-piperazinedione to interfere with the binding process of 3-oxo-C12-HSL to its receptor protein. Thus, the findings of the present study reveal the potential of 2,5-piperazinedione in reducing the QS-dependent phenotypic features of PAO1. PMID:22359266

Musthafa, Khadar Syed; Balamurugan, Krishnaswamy; Pandian, Shunmugiah Karutha; Ravi, Arumugam Veera

2012-12-01

391

Quorum sensing triggers the stochastic escape of individual cells from Pseudomonas putida biofilms  

PubMed Central

The term ‘quorum sensing’ (QS) is generally used to describe the phenomenon that bacteria release and perceive signal molecules to coordinate cooperative behaviour in response to their population size. QS-based communication has therefore been considered a social trait. Here we show that QS signals (N-acyl-homoserine lactones, AHLs) are stochastically produced in young biofilms of Pseudomonas putida and act mainly as self-regulatory signals rather than inducing neighbouring cells. We demonstrate that QS induces the expression of putisolvin biosurfactants that are not public goods, thereby triggering asocial motility of induced cells out of microcolonies. Phenotypic heterogeneity is most prominent in the early stages of biofilm development, whereas at later stages behaviour patterns across cells become more synchronized. Our findings broaden our perspective on QS by showing that AHLs can control the expression of asocial (self-directed) traits, and that heterogeneity in QS can serve as a mechanism to drive phenotypic heterogeneity in self-directed behaviour. PMID:25592773

Cárcamo-Oyarce, Gerardo; Lumjiaktase, Putthapoom; Kümmerli, Rolf; Eberl, Leo

2015-01-01

392

Protease IV, a quorum sensing-dependent protease of Pseudomonas aeruginosa modulates insect innate immunity.  

PubMed

In Pseudomonas aeruginosa, quorum sensing (QS) plays an essential role in pathogenesis and the QS response controls many virulence factors. Using a mealworm, Tenebrio molitor as a host model, we found that Protease IV, a QS-regulated exoprotease of P. aeruginosa functions as a key virulence effector causing the melanization and death of T. molitor larvae. Protease IV was able to degrade zymogens of spätzle processing enzyme (SPE) and SPE-activating enzyme (SAE) without the activation of the antimicrobial peptide (AMP) production. Since SPE and SAE function to activate spätzle, a ligand of Toll receptor in the innate immune system of T. molitor, we suggest that Protease IV may interfere with the activation of the Toll signaling. Independently of the Toll pathway, the melanization response, another innate immunity was still generated, since Protease IV directly converted Tenebrio prophenoloxidase into active phenoloxidase. Protease IV also worked as an important factor in the virulence to brine shrimp and nematode. These results suggest that Protease IV provides P. aeruginosa with a sophisticated way to escape the immune attack of host by interfering with the production of AMPs. PMID:25315216

Park, Su-Jin; Kim, Soo-Kyoung; So, Yong-In; Park, Ha-Young; Li, Xi-Hui; Yeom, Doo Hwan; Lee, Mi-Nan; Lee, Bok-Luel; Lee, Joon-Hee

2014-12-01

393

Anti-Quorum Sensing Potential of Crude Kigelia africana Fruit Extracts  

PubMed Central

The increasing incidence of multidrug-resistant pathogens has stimulated the search for novel anti-virulence compounds. Although many phytochemicals show promising antimicrobial activity, their power lies in their anti-virulence properties. Thus the quorum sensing (QS) inhibitory activity of four crude Kigelia africana fruit extracts was assessed qualitatively and quantitatively using the Chromobacterium violaceum and Agrobacterium tumefaciens biosensor systems. Inhibition of QS-controlled violacein production in C. violaceum was assayed using the qualitative agar diffusion assay as well as by quantifying violacein inhibition using K. africana extracts ranging from 0.31–8.2 mg/mL. Qualitative modulation of QS activity was investigated using the agar diffusion double ring assay. All four extracts showed varying levels of anti-QS activity with zones of violacein inhibition ranging from 9–10 mm. The effect on violacein inhibition was significant in the following order: hexane > dichloromethane > ethyl acetate > methanol. Inhibition was concentration-dependent, with the ?90% inhibition being obtained with ?1.3 mg/mL of the hexane extract. Both LuxI and LuxR activity were affected by crude extracts suggesting that the phytochemicals target both QS signal and receptor. K. africana extracts with their anti-QS activity, have the potential to be novel therapeutic agents, which might be important in reducing virulence and pathogenicity of drug-resistant bacteria in vivo. PMID:23447012

Chenia, Hafizah Y.

2013-01-01

394

Quorum sensing triggers the stochastic escape of individual cells from Pseudomonas putida biofilms.  

PubMed

The term 'quorum sensing' (QS) is generally used to describe the phenomenon that bacteria release and perceive signal molecules to coordinate cooperative behaviour in response to their population size. QS-based communication has therefore been considered a social trait. Here we show that QS signals (N-acyl-homoserine lactones, AHLs) are stochastically produced in young biofilms of Pseudomonas putida and act mainly as self-regulatory signals rather than inducing neighbouring cells. We demonstrate that QS induces the expression of putisolvin biosurfactants that are not public goods, thereby triggering asocial motility of induced cells out of microcolonies. Phenotypic heterogeneity is most prominent in the early stages of biofilm development, whereas at later stages behaviour patterns across cells become more synchronized. Our findings broaden our perspective on QS by showing that AHLs can control the expression of asocial (self-directed) traits, and that heterogeneity in QS can serve as a mechanism to drive phenotypic heterogeneity in self-directed behaviour. PMID:25592773

Cárcamo-Oyarce, Gerardo; Lumjiaktase, Putthapoom; Kümmerli, Rolf; Eberl, Leo

2015-01-01

395

Bacillus marcorestinctum sp. nov., a Novel Soil Acylhomoserine Lactone Quorum-Sensing Signal Quenching Bacterium  

PubMed Central

A Gram-positive, facultatively anaerobic, endospore-forming and rod-shaped bacterium was isolated from soil samples and designated strain LQQ. This organism strongly quenches the acylhomoserine lactone quorum-sensing signal. The LQQ strain exhibits phenotypic characteristics consistent with its classification in the genus Bacillus. It is positive in catalase and no special growth factor is needed. It uses glucose as sole carbon source. The DNA G + C content is 39.8 mol %. The closest relatives based on the 16S rRNA gene sequence are Bacillus anthracis, Bacillus thuringiensis, and Brevibacillus brevis (syn. Bacillus brevis) with the similarity of 96.5%. The DNA–DNA hybridization data indicates a low level of genomic relatedness with the relative type strains of Bacillus thuringiensis (6.1%), Bacillus anthracis (10.5%) and Brevibacillus brevis (8.7%). On the basis of the phenotypic and phylogenetic data together with the genomic distinctiveness, the LQQ strain represents a novel species of the genus Bacillus, for which the name Bacillus marcorestinctum sp. nov. is proposed. The type strain is LQQT. PMID:20386651

Han, Yan; Chen, Fang; Li, Nuo; Zhu, Bo; Li, Xianzhen

2010-01-01

396

Proline antagonizes GABA-induced quenching of quorum-sensing in Agrobacterium tumefaciens.  

PubMed

Plants accumulate free L-proline (Pro) in response to abiotic stresses (drought and salinity) and presence of bacterial pathogens, including the tumor-inducing bacterium Agrobacterium tumefaciens. However, the function of Pro accumulation in host-pathogen interaction is still unclear. Here, we demonstrated that Pro antagonizes plant GABA-defense in the A. tumefaciens C58-induced tumor by interfering with the import of GABA and consequently the GABA-induced degradation of the bacterial quorum-sensing signal, 3-oxo-octanoylhomoserine lactone. We identified a bacterial receptor Atu2422, which is implicated in the uptake of GABA and Pro, suggesting that Pro acts as a natural antagonist of GABA-signaling. The Atu2422 amino acid sequence contains a Venus flytrap domain that is required for trapping GABA in human GABA(B) receptors. A constructed atu2422 mutant was more virulent than the wild type bacterium; moreover, transgenic plants with a low level of Pro exhibited less severe tumor symptoms than did their wild-type parents, revealing a crucial role for Venus flytrap GABA-receptor and relative abundance of GABA and Pro in host-pathogen interaction. PMID:19706545

Haudecoeur, E; Planamente, S; Cirou, A; Tannières, M; Shelp, B J; Moréra, S; Faure, D

2009-08-25

397

Crystal Structure of the Vibrio Cholerae Quorum-Sensing Regulatory Protein HapR  

SciTech Connect

Quorum sensing in Vibrio cholerae involves signaling between two-component sensor protein kinases and the response regulator LuxO to control the expression of the master regulator HapR. HapR, in turn, plays a central role in regulating a number of important processes, such as virulence gene expression and biofilm formation. We have determined the crystal structure of HapR to 2.2- Angstroms resolution. Its structure reveals a dimeric, two-domain molecule with an all-helical structure that is strongly conserved with members of the TetR family of transcriptional regulators. The N-terminal DNA-binding domain contains a helix-turn-helix DNA-binding motif and alteration of certain residues in this domain completely abolishes the ability of HapR to bind to DNA, alleviating repression of both virulence gene expression and biofilm formation. The C-terminal dimerization domain contains a unique solvent accessible tunnel connected to an amphipathic cavity, which by analogy with other TetR regulators, may serve as a binding pocket for an as-yet-unidentified ligand.

DeSilva,R.; Kovacikova, G.; Lin, W.; Taylor, R.; Skorupski, K.; Kull, F.

2007-01-01

398

Collective behavior and quorum sensing in a system of communicating microcapsules  

NASA Astrophysics Data System (ADS)

We report the results on collective motion of polymeric microcapsules in a fluid-filled microchannel. We consider the case where motion of the nanoparticle-filled microcapsules is controlled by adhesion at the channel's wall and hydrodynamic coupling between the capsules. Using the hybrid Lattice Boltzmann method for fluid dynamics and Lattice spring model for the micromechanics of elastic solid, we determined how the characteristics of the substrate, the polymeric shell, encapsulated fluid and the surrounding solution affect the capsule's velocity and ``gait'' of the capsule within the system. In numerical computations we find the conditions under which microcapsules communicating through modification of the microchannel surface by released nanoparticles exhibit collective motion, thereby mimicking behavior of the colony of living cells. In particular, we show that this system demonstrates a quorum sensing. That is, the capsules motion depends on population and behavior of neighboring groups of capsules. Finally, the design of a repair-and-go system is presented, in which we show that deposition of nanoparticles from moving microcapsules onto a damaged substrate can be used as an effective tool for selective repair of defects or cracks on the substrate.

Kolmakov, German; Bhattacharya, Amitabh; Balazs, Anna

2009-11-01

399

Individuals in the crowd: studying bacterial quorum-sensing at the single-cell level  

NASA Astrophysics Data System (ADS)

Like many bacterial species, the marine bacterium Vibrio fischeri can detect its own population density through a quorum sensing (QS) mechanism. The bacterium releases a small molecule signal -- the autoinducer (AI) -- into its environment: high AI concentration indicates high population density and triggers a genetic switch that, in V.fischeri, leads to bioluminescence. Although the QS behavior of bulk cultures of V.fischeri has been extensively studied, little is known about either the response of individual cells to AI signal levels or the role of noise and local diffusion in QS signaling. We have used a photon-counting camera to record the luminescence of individual V.fischeri cells immobilized in a flow cell and subject to varying concentrations of AI. We observe that light output by individual cells varies not only with bulk AI concentration, but also over time, between cells, with local (micron-scale) population density, and even with the flow rate of the medium. Most of these variations would not be evident in a bulk culture. We will present an analysis of this heterogeneity at the cell level and its implications for the role of noise in QS signaling.

Delfino Perez, Pablo; Young, Jonathan; Johnson, Elaine L.; Hagen, Stephen J.

2009-03-01

400

Dynamics of AHL mediated quorum sensing under flow and non-flow conditions  

NASA Astrophysics Data System (ADS)

Quorum sensing (QS) describes the capability of microbes to communicate with each other by the aid of small molecules. Here we investigate the dynamics of QS-regulated gene expression induced by acylhomoserine lactones (AHLs) in Pseudomonas putida IsoF containing a green fluorescent protein-based AHL reporter. The fluorescence time course of individual colonies is monitored following the external addition of a defined AHL concentration to cells which had previously reached the QS-inactive state in AHL-free medium. Using a microfluidic setup the experiment is performed both under flow and non-flow conditions. We find that without supplying external AHL gene expression is induced without flow while flow suppresses the induction. Both without and with flow, at a low AHL concentration the fluorescence onset is significantly delayed while fluorescence starts to increase directly upon the addition of AHL at a high concentration. The differences between no flow and flow can be accounted for using a two-compartment model. This indicates AHL accumulation in a volume which is not affected by the flow. The experiments furthermore show significant cell-to-cell and colony-to-colony variability which is discussed in the context of a compartmentalized QS mechanism.

Meyer, Andrea; Megerle, Judith A.; Kuttler, Christina; Müller, Johannes; Aguilar, Claudio; Eberl, Leo; Hense, Burkhard A.; Rädler, Joachim O.

2012-04-01

401

Quorum Sensing-Mediated, Cell Density-Dependent Regulation of Growth and Virulence in Cryptococcus neoformans  

PubMed Central

ABSTRACT Quorum sensing (QS) is a cell density-dependent mechanism of communication between microorganisms, characterized by the release of signaling molecules that affect microbial metabolism and gene expression in a synchronized way. In this study, we investigated cell density-dependent behaviors mediated by conditioned medium (CM) in the pathogenic encapsulated fungus Cryptococcus neoformans. CM produced dose-dependent increases in the growth of planktonic and biofilm cells, glucuronoxylomannan release, and melanin synthesis, important virulence attributes of this organism. Mass spectrometry revealed the presence of pantothenic acid (PA) in our samples, and commercial PA was able to increase growth and melanization, although not to the same extent as CM. Additionally, we found four mutants that were either unable to produce active CM or failed to respond with increased growth in the presence of wild-type CM, providing genetic evidence for the existence of intercellular communication in C. neoformans. C. neoformans CM also increased the growth of Cryptococcus albidus, Candida albicans, and Saccharomyces cerevisiae. Conversely, CM from Cryptococcus albidus, C. albicans, S. cerevisiae, and Sporothrix schenckii increased C. neoformans growth. In summary, we report the existence of a new QS system regulating the growth and virulence factor expression of C. neoformans in vitro and, possibly, also able to regulate growth in other fungi. PMID:24381301

Albuquerque, Patrícia; Nicola, André M.; Nieves, Edward; Paes, Hugo Costa; Williamson, Peter R.; Silva-Pereira, Ildinete; Casadevall, Arturo

2013-01-01

402

Bacterial quorum sensing, cooperativity, and anticipation of stationary-phase stress  

PubMed Central

Acyl-homoserine lactone–mediated quorum sensing (QS) regulates diverse activities in many species of Proteobacteria. QS-controlled genes commonly code for production of secreted or excreted public goods. The acyl-homoserine lactones are synthesized by members of the LuxI signal synthase family and are detected by cognate members of the LuxR family of transcriptional regulators. QS affords a means of population density-dependent gene regulation. Control of public goods via QS provides a fitness benefit. Another potential role for QS is to anticipate overcrowding. As population density increases and stationary phase approaches, QS might induce functions important for existence in stationary phase. Here we provide evidence that in three related species of the genus Burkholderia QS allows individuals to anticipate and survive stationary-phase stress. Survival requires QS-dependent activation of cellular enzymes required for production of excreted oxalate, which serves to counteract ammonia-mediated alkaline toxicity during stationary phase. Our findings provide an example of QS serving as a means to anticipate stationary phase or life at the carrying capacity of a population by activating the expression of cytoplasmic enzymes, altering cellular metabolism, and producing a shared resource or public good, oxalate. PMID:23150539

Goo, Eunhye; Majerczyk, Charlotte D.; An, Jae Hyung; Chandler, Josephine R.; Seo, Young-Su; Ham, Hyeonheui; Lim, Jae Yun; Kim, Hongsup; Lee, Bongsoo; Jang, Moon Sun; Greenberg, E. Peter; Hwang, Ingyu

2012-01-01

403

Uracil influences quorum sensing and biofilm formation in Pseudomonas aeruginosa and fluorouracil is an antagonist  

PubMed Central

Summary Pseudomonas aeruginosa is an ubiquitous, opportunistic pathogen whose biofilms are notoriously difficult to control. Here we discover uracil influences all three known quorum?sensing (QS) pathways of P. aeruginosa. By screening 5850 transposon mutants for altered biofilm formation, we identified seven uracil?related mutations that abolished biofilm formation. Whole?transcriptome studies showed the uracil mutations (e.g. pyrF that catalyses the last step in uridine monophosphate synthesis) alter the regulation of all three QS pathways [LasR?, RhlR? and 2?heptyl?3?hydroxy?4?quinolone (PQS)?related regulons]; addition of extracellular uracil restored global wild?type regulation. Phenotypic studies confirmed uracil influences the LasR (elastase), RhlR (pyocyanin, rhamnolipids), PQS and swarming regulons. Our results also demonstrate uracil influences virulence (the pyrF mutant was less virulent to barley). Additionally, we found an anticancer uracil analogue, 5?fluorouracil, that repressed biofilm formation, abolished QS phenotypes and reduced virulence. Hence, we have identified a central regulator of an important pathogen and a potential novel class of efficacious drugs for controlling cellular behaviour (e.g. biofilm formation and virulence). PMID:21261882

Ueda, Akihiro; Attila, Can; Whiteley, Marvin; Wood, Thomas K.

2009-01-01

404

Small Molecules that Modulate Quorum Sensing and Control Virulence in Pseudomonas aeruginosa  

PubMed Central

Bacteria use small molecule signals to access their local population densities in a process called quorum sensing (QS). Once a threshold signal concentration is reached, and therefore a certain number of bacteria have assembled, bacteria use QS to change gene expression levels and initiate behaviors that benefit the group. These group processes play central roles in both bacterial virulence and symbiosis, and can have significant impacts on human health, agriculture, and the environment. The dependence of QS on small molecule signals has inspired organic chemists to design non-native molecules that can intercept these signals and thereby perturb bacterial group behaviors. The opportunistic pathogen Pseudomonas aeruginosa has been the target of many of these efforts due to its prevalence in human infections. P. aeruginosa uses at least two N-acyl L-homoserine lactone signals and three homologous LuxR-type receptors to initiate a range of pathogenic behaviors at high cell densities, including biofilm formation and the production of an arsenal of virulence factors. This review highlights recent chemical efforts to modulate LuxR-type receptor activity in P. aeruginosa, and offers insight into the development of receptor-specific ligands as potential anti-virulence strategies. PMID:20672805

Mattmann, Margrith E.; Blackwell, Helen E.

2010-01-01

405

Microbial Quorum-Sensing Molecules Induce Acrosome Loss and Cell Death in Human Spermatozoa?  

PubMed Central

Infertility in men and women is frequently associated with genital contamination by various commensal or uropathogenic microbes. Since many microorganisms are known to release quorum-sensing signals in substantial amounts, we raised the question whether such molecules can directly affect human spermatozoa. Here we show that farnesol and 3-oxododecanoyl-l-homoserine lactone, employed by the opportunistic pathogenic yeast Candida albicans and the gram-negative bacterium Pseudomonas aeruginosa, respectively, induce multiple damage in spermatozoa. A reduction in the motility of spermatozoa coincided in a dose-dependent manner with apoptosis and necrosis at concentrations which were nondeleterious for dendritic cell-like immune cells. Moreover, sublethal doses of both signaling molecules induced premature loss of the acrosome, a cap-like structure of the sperm head which is essential for fertilization. Addressing their mechanism of action, we found that the bacterial molecule, but not the fungal molecule, actively induced the acrosome reaction via a calcium-dependent mechanism. This work uncovers a new facet in the interaction of microorganisms with human gametes and suggests a putative link between microbial communication systems and host infertility. PMID:19687207

Rennemeier, Claudia; Frambach, Torsten; Hennicke, Florian; Dietl, Johannes; Staib, Peter

2009-01-01

406

Discovery of a nitric oxide responsive quorum sensing circuit in Vibrio harveyi.  

PubMed

Bacteria use small molecules to assess the density and identity of nearby organisms and formulate a response. This process, called quorum sensing (QS), commonly regulates bioluminescence, biofilm formation, and virulence. Vibrio harveyi have three described QS circuits. Each involves the synthesis of a molecule that regulates phosphorylation of its cognate receptor kinase. Each receptor exchanges phosphate with a common phosphorelay protein, LuxU, which ultimately regulates bioluminescence. Here, we show that another small molecule, nitric oxide (NO), participates in QS through LuxU. V. harveyi display a NO concentration-dependent increase in bioluminescence that is regulated by an hnoX gene. We demonstrate that H-NOX is a NO sensor and NO/H-NOX regulates phosphorylation of a kinase that transfers phosphate to LuxU. This study reveals the discovery of a fourth QS pathway in V. harveyi and suggests that bacteria use QS to integrate not only the density of bacteria but also other diverse information about their environment into decisions about gene expression. PMID:22606970

Henares, Bernadette M; Higgins, Kate E; Boon, Elizabeth M

2012-08-17

407

Global and Phylogenetic Distribution of Quorum Sensing Signals, Acyl Homoserine Lactones, in the Family of Vibrionaceae  

PubMed Central

Bacterial quorum sensing (QS) and the corresponding signals, acyl homoserine lactones (AHLs), were first described for a luminescent Vibrio species. Since then, detailed knowledge has been gained on the functional level of QS; however, the abundance of AHLs in the family of Vibrionaceae in the environment has remained unclear. Three hundred and one Vibrionaceae strains were collected on a global research cruise and the prevalence and profile of AHL signals in this global collection were determined. AHLs were detected in 32 of the 301 strains using Agrobacterium tumefaciens and Chromobacterium violaceum reporter strains. Ethyl acetate extracts of the cultures were analysed by ultra-high performance liquid chromatography-high resolution mass spectrometry (MS) with automated tandem MS confirmation for AHLs. N-(3-hydroxy-hexanoyl) (OH-C6) and N-(3-hydroxy-decanoyl) (OH-C10) homoserine lactones were the most common AHLs found in 17 and 12 strains, respectively. Several strains produced a diversity of different AHLs, including N-heptanoyl (C7) HL. AHL-producing Vibrionaceae were found in polar, temperate and tropical waters. The AHL profiles correlated with strain phylogeny based on gene sequence homology, however not with geographical location. In conclusion, a wide range of AHL signals are produced by a number of clades in the Vibrionaceae family and these results will allow future investigations of inter- and intra-species interactions within this cosmopolitan family of marine bacteria. PMID:25419995

Barker Rasmussen, Bastian; Fog Nielsen, Kristian; Machado, Henrique; Melchiorsen, Jette; Gram, Lone; Sonnenschein, Eva C.

2014-01-01

408

Freshwater-Borne Bacteria Isolated from a Malaysian Rainforest Waterfall Exhibiting Quorum Sensing Properties  

PubMed Central

One obvious requirement for concerted action by a bacterial population is for an individual to be aware of and respond to the other individuals of the same species in order to form a response in unison. The term “quorum sensing” (QS) was coined to describe bacterial communication that is able to stimulate expression of a series of genes when the concentration of the signaling molecules has reached a threshold level. Here we report the isolation from aquatic environment of a bacterium that was later identified as Enterobacter sp.. Chromobacterium violaceum CV026 and Escherichia coli [pSB401] were used for preliminary screening of N-acyl homoserine lactone (AHL) production. The Enterobacter sp. isolated was shown to produce two types of AHLs as confirmed by analysis using high resolution tandem mass spectrometry. To the best of our knowledge, this is the first documentation of an Enterobacter sp. that produced both 3-oxo-C6-HSL and 3-oxo-C8-HSL as QS signaling molecules. PMID:24932870

Tan, Wen-Si; Yunos, Nina Yusrina Muhamad; Tan, Pui-Wan; Mohamad, Nur Izzati; Adrian, Tan-Guan-Sheng; Yin, Wai-Fong; Chan, Kok-Gan

2014-01-01

409

Methylobacterium-plant interaction genes regulated by plant exudate and quorum sensing molecules  

PubMed Central

Bacteria from the genus Methylobacterium interact symbiotically (endophytically and epiphytically) with different plant species. These interactions can promote plant growth or induce systemic resistance, increasing plant fitness. The plant colonization is guided by molecular communication between bacteria-bacteria and bacteria-plants, where the bacteria recognize specific exuded compounds by other bacteria (e.g. homoserine molecules) and/or by the plant roots (e.g. flavonoids, ethanol and methanol), respectively. In this context, the aim of this study was to evaluate the effect of quorum sensing molecules (N-acyl-homoserine lactones) and plant exudates (including ethanol) in the expression of a series of bacterial genes involved in Methylobacterium-plant interaction. The selected genes are related to bacterial metabolism (mxaF), adaptation to stressful environment (crtI, phoU and sss), to interactions with plant metabolism compounds (acdS) and pathogenicity (patatin and phoU). Under in vitro conditions, our results showed the differential expression of some important genes related to metabolism, stress and pathogenesis, thereby AHL molecules up-regulate all tested genes, except phoU, while plant exudates induce only mxaF gene expression. In the presence of plant exudates there is a lower bacterial density (due the endophytic and epiphytic colonization), which produce less AHL, leading to down regulation of genes when compared to the control. Therefore, bacterial density, more than plant exudate, influences the expression of genes related to plant-bacteria interaction. PMID:24688531

Dourado, Manuella Nóbrega; Bogas, Andrea Cristina; Pomini, Armando M.; Andreote, Fernando Dini; Quecine, Maria Carolina; Marsaioli, Anita J.; Araújo, Welington Luiz

2013-01-01

410

A Quorum Sensing Small Volatile Molecule Promotes Antibiotic Tolerance in Bacteria  

PubMed Central

Bacteria can be refractory to antibiotics due to a sub-population of dormant cells, called persisters that are highly tolerant to antibiotic exposure. The low frequency and transience of the antibiotic tolerant “persister” trait has complicated elucidation of the mechanism that controls antibiotic tolerance. In this study, we show that 2’ Amino-acetophenone (2-AA), a poorly studied but diagnostically important small, volatile molecule produced by the recalcitrant gram-negative human pathogen Pseudomonas aeruginosa, promotes antibiotic tolerance in response to quorum-sensing (QS) signaling. Our results show that 2-AA mediated persister cell accumulation occurs via alteration of the expression of genes involved in the translational capacity of the cell, including almost all ribosomal protein genes and other translation-related factors. That 2-AA promotes persisters formation also in other emerging multi-drug resistant pathogens, including the non 2-AA producer Acinetobacter baumannii implies that 2-AA may play an important role in the ability of gram-negative bacteria to tolerate antibiotic treatments in polymicrobial infections. Given that the synthesis, excretion and uptake of QS small molecules is a common hallmark of prokaryotes, together with the fact that the translational machinery is highly conserved, we posit that modulation of the translational capacity of the cell via QS molecules, may be a general, widely distributed mechanism that promotes antibiotic tolerance among prokaryotes. PMID:24367477

Strobel, Benjamin; Maura, Damien; He, Jianxin; Kesarwani, Meenu; Panopoulos, Panagiotis; Tsurumi, Amy; Giddey, Marlyse; Wilhelmy, Julie; Mindrinos, Michael N.; Rahme, Laurence G.

2013-01-01

411

A metabolic regulator modulates virulence and quorum sensing signal production in Pectobacterium atrosepticum.  

PubMed

Plant cell wall-degrading enzymes (PCWDE) are key virulence determinants in the pathogenesis of the potato pathogen Pectobacterium atrosepticum. In this study, we report the impact on virulence of a transposon insertion mutation in the metJ gene that codes for the repressor of the methionine biosynthesis regulon. In a mutant strain defective for the small regulatory RNA rsmB, PCWDE are not produced and virulence in potato tubers is almost totally abolished. However, when the metJ gene is disrupted in this background, the rsmB(-) phenotype is suppressed and virulence and PCWDE production are restored. Additionally, when metJ is disrupted, production of the quorum-sensing signal, N-(3-oxohexanoyl)-homoserine lactone, is increased. The metJ mutant strains showed pleiotropic transcriptional impacts affecting approximately a quarter of the genome. Genes involved in methionine biosynthesis were most highly upregulated but many virulence-associated transcripts were also upregulated. This is the first report of the impact of the MetJ repressor on virulence in bacteria. PMID:23113713

Cubitt, Marion F; Hedley, Peter E; Williamson, Neil R; Morris, Jenny A; Campbell, Emma; Toth, Ian K; Salmond, George P C

2013-03-01

412

10/17/2007 02:14 PMThis Week in Evolution: Cooperation and cheating in microbes: quorum sensing and persisters Page 1 of 3http://blog.lib.umn.edu/denis036/thisweekinevolution/2007/09/cooperation_and_cheating_in_mi.html#more  

E-print Network

10/17/2007 02:14 PMThis Week in Evolution: Cooperation and cheating in microbes: quorum sensing and cheating in microbes: quorum sensing and persisters Two papers on cooperation this week. If you were trying enough of a "virulence factor" to overcome host defenses. Bacteria often exchange "quorum-sensing

Reece, Sarah

413

Genome wide dissection of the quorum sensing signaling pathway in Trypanosoma brucei  

PubMed Central

The protozoan parasites Trypanosoma brucei spp. cause important human and livestock diseases in sub Saharan Africa. In the mammalian blood, two developmental forms of the parasite exist: proliferative ‘slender’ forms and arrested ‘stumpy’ forms that are responsible for transmission to tsetse flies. The slender to stumpy differentiation is a density-dependent response that resembles quorum sensing (QS) in microbial systems and is crucial for the parasite life cycle, ensuring both infection chronicity and disease transmission1. This response is triggered by an elusive ‘stumpy induction factor’ (SIF) whose intracellular signaling pathway is also uncharacterized. Laboratory-adapted (monomorphic) trypanosome strains respond inefficiently to SIF but can generate forms with stumpy characteristics when exposed to cell permeable cAMP and AMP analogues. Exploiting this, we have used a genome-wide RNAi library screen to identify the signaling components driving stumpy formation. In separate screens, monomorphic parasites were exposed to 8-(4-chlorophenylthio)-cAMP (pCPTcAMP) or 8-pCPT-2?-O-Me-5?-AMP to select cells that were unresponsive to these signals and hence remained proliferative. Genome-wide ion torrent-based RNA interference Target sequencing identified cohorts of genes implicated in each step of the signaling pathway, from purine metabolism, through signal transducers (kinases, phosphatases) to gene expression regulators. Genes at each step were independently validated in cells naturally capable of stumpy formation, confirming their role in density sensing in vivo, whilst the putative RNA-binding protein, RBP7, was required for normal QS and promoted cell-cycle arrest and transmission competence when overexpressed. This study reveals that QS signaling in trypanosomes shares similarities to fundamental quiescence pathways in eukaryotic cells, its components providing targets for QS-interference based therapeutics. PMID:24336212

Ivens, Alasdair; Rojas, Federico; Cowton, Andrew; Young, Julie; Horn, David; Matthews, Keith

2013-01-01

414

ESPM 131 Study Questions for last 1/3 of course S06 What is quorum sensing and why do bacteria do it?  

E-print Network

ESPM 131 Study Questions for last 1/3 of course S06 What is quorum sensing and why do bacteria do in the sense that they are limited to a single plant family, but how are they major players from a global

California at Berkeley, University of

415

Targeting agr- and agr-Like Quorum Sensing Systems for Development of Common Therapeutics to Treat Multiple Gram-Positive Bacterial Infections  

PubMed Central

Invasive infection by the Gram-positive pathogen Staphylococcus aureus is controlled by a four gene operon, agr that encodes a quorum sensing system for the regulation of virulence. While agr has been well studied in S. aureus, the contribution of agr homologues and analogues in other Gram-positive pathogens is just beginning to be understood. Intriguingly, other significant human pathogens, including Clostridium perfringens, Listeria monocytogenes, and Enterococcus faecalis contain agr or analogues linked to virulence. Moreover, other significant human Gram-positive pathogens use peptide based quorum sensing systems to establish or maintain infection. The potential for commonality in aspects of these signaling systems across different species raises the prospect of identifying therapeutics that could target multiple pathogens. Here, we review the status of research into these agr homologues, analogues, and other peptide based quorum sensing systems in Gram-positive pathogens as well as the potential for identifying common pathways and signaling mechanisms for therapeutic discovery. PMID:23598501

Gray, Brian; Hall, Pamela; Gresham, Hattie

2013-01-01

416

Marine-Derived Quorum-Sensing Inhibitory Activities Enhance the Antibacterial Efficacy of Tobramycin against Pseudomonas aeruginosa.  

PubMed

Bacterial epiphytes isolated from marine eukaryotes were screened for the production of quorum sensing inhibitory compounds (QSIs). Marine isolate KS8, identified as a Pseudoalteromonas sp., was found to display strong quorum sensing inhibitory (QSI) activity against acyl homoserine lactone (AHL)-based reporter strains Chromobacterium violaceum ATCC 12472 and CV026. KS8 supernatant significantly reduced biofilm biomass during biofilm formation (-63%) and in pre-established, mature P. aeruginosa PAO1 biofilms (-33%). KS8 supernatant also caused a 0.97-log reduction (-89%) and a 2-log reduction (-99%) in PAO1 biofilm viable counts in the biofilm formation assay and the biofilm eradication assay respectively. The crude organic extract of KS8 had a minimum inhibitory concentration (MIC) of 2 mg/mL against PAO1 but no minimum bactericidal concentration (MBC) was observed over the concentration range tested (MBC > 16 mg/mL). Sub-MIC concentrations (1 mg/mL) of KS8 crude organic extract significantly reduced the quorum sensing (QS)-dependent production of both pyoverdin and pyocyanin in P. aeruginosa PAO1 without affecting growth. A combinatorial approach using tobramycin and the crude organic extract at 1 mg/mL against planktonic P. aeruginosa PAO1 was found to increase the efficacy of tobramycin ten-fold, decreasing the MIC from 0.75 to 0.075 µg/mL. These data support the validity of approaches combining conventional antibiotic therapy with non-antibiotic compounds to improve the efficacy of current treatments. PMID:25546516

Busetti, Alessandro; Shaw, George; Megaw, Julianne; Gorman, Sean P; Maggs, Christine A; Gilmore, Brendan F

2014-01-01

417

Marine-Derived Quorum-Sensing Inhibitory Activities Enhance the Antibacterial Efficacy of Tobramycin against Pseudomonas aeruginosa  

PubMed Central

Bacterial epiphytes isolated from marine eukaryotes were screened for the production of quorum sensing inhibitory compounds (QSIs). Marine isolate KS8, identified as a Pseudoalteromonas sp., was found to display strong quorum sensing inhibitory (QSI) activity against acyl homoserine lactone (AHL)-based reporter strains Chromobacterium violaceum ATCC 12472 and CV026. KS8 supernatant significantly reduced biofilm biomass during biofilm formation (?63%) and in pre-established, mature P. aeruginosa PAO1 biofilms (?33%). KS8 supernatant also caused a 0.97-log reduction (?89%) and a 2-log reduction (?99%) in PAO1 biofilm viable counts in the biofilm formation assay and the biofilm eradication assay respectively. The crude organic extract of KS8 had a minimum inhibitory concentration (MIC) of 2 mg/mL against PAO1 but no minimum bactericidal concentration (MBC) was observed over the concentration range tested (MBC > 16 mg/mL). Sub-MIC concentrations (1 mg/mL) of KS8 crude organic extract significantly reduced the quorum sensing (QS)-dependent production of both pyoverdin and pyocyanin in P. aeruginosa PAO1 without affecting growth. A combinatorial approach using tobramycin and the crude organic extract at 1 mg/mL against planktonic P. aeruginosa PAO1 was found to increase the efficacy of tobramycin ten-fold, decreasing the MIC from 0.75 to 0.075 µg/mL. These data support the validity of approaches combining conventional antibiotic therapy with non-antibiotic compounds to improve the efficacy of current treatments. PMID:25546516

Busetti, Alessandro; Shaw, George; Megaw, Julianne; Gorman, Sean P.; Maggs, Christine A.; Gilmore, Brendan F.

2014-01-01

418

Expanding dialogues: from natural autoinducers to non-natural analogues that modulate quorum sensing in Gram-negative bacteria†  

PubMed Central

Bacteria are capable of “communicating” their local population densities via a process termed quorum sensing (QS). Gram-negative bacteria use N-acylated l-homoserine lactones (AHLs), in conjunction with their cognate LuxR-type receptors, as their primary signalling circuit for QS. In this critical review, we examine AHL signalling in Gram-negative bacteria with a primary focus on the design of non-natural AHLs, their structure-activity relationships, and their application in chemical biological approaches to study QS. PMID:18568169

Geske, Grant D.; O’Neill, Jennifer C.; Blackwell, Helen E.

2008-01-01

419

Private link between signal and response in Bacillus subtilis quorum sensing  

PubMed Central

Bacteria coordinate their behavior using quorum sensing (QS), whereby cells secrete diffusible signals that generate phenotypic responses associated with group living. The canonical model of QS is one of extracellular signaling, where signal molecules bind to cognate receptors and cause a coordinated response across many cells. Here we study the link between QS input (signaling) and QS output (response) in the ComQXPA QS system of Bacillus subtilis by characterizing the phenotype and fitness of comQ null mutants. These lack the enzyme to produce the ComX signal and do not activate the ComQXPA QS system in other cells. In addition to the activation effect of the signal, however, we find evidence of a second, repressive effect of signal production on the QS system. Unlike activation, which can affect other cells, repression acts privately: the de-repression of QS in comQ cells is intracellular and only affects mutant cells lacking ComQ. As a result, the QS signal mutants have an overly responsive QS system and overproduce the secondary metabolite surfactin in the presence of the signal. This surfactin overproduction is associated with a strong fitness cost, as resources are diverted away from primary metabolism. Therefore, by acting as a private QS repressor, ComQ may be protected against evolutionary competition from loss-of-function mutations. Additionally, we find that surfactin participates in a social selection mechanism that targets signal null mutants in coculture with signal producers. Our study shows that by pleiotropically combining intracellular and extracellular signaling, bacteria may generate evolutionarily stable QS systems. PMID:24425772

Oslizlo, Anna; Stefanic, Polonca; Dogsa, Iztok; Mandic-Mulec, Ines

2014-01-01

420

What Does the Talking?: Quorum Sensing Signalling Genes Discovered in a Bacteriophage Genome  

PubMed Central

The transfer of novel genetic material into the genomes of bacterial viruses (phages) has been widely documented in several host-phage systems. Bacterial genes are incorporated into the phage genome and, if retained, subsequently evolve within them. The expression of these phage genes can subvert or bolster bacterial processes, including altering bacterial pathogenicity. The phage phiCDHM1 infects Clostridium difficile, a pathogenic bacterium that causes nosocomial infections and is associated with antibiotic treatment. Genome sequencing and annotation of phiCDHM1 shows that despite being closely related to other C. difficile myoviruses, it has several genes that have not been previously reported in any phage genomes. Notably, these include three homologs of bacterial genes from the accessory gene regulator (agr) quorum sensing (QS) system. These are; a pre-peptide (AgrD) of an autoinducing peptide (AIP), an enzyme which processes the pre-peptide (AgrB) and a histidine kinase (AgrC) that detects the AIP to activate a response regulator. Phylogenetic analysis of the phage and C. difficile agr genes revealed that there are three types of agr loci in this species. We propose that the phage genes belonging to a third type, agr3, and have been horizontally transferred from the host. AgrB and AgrC are transcribed during the infection of two different strains. In addition, the phage agrC appears not to be confined to the phiCDHM1 genome as it was detected in genetically distinct C. difficile strains. The discovery of QS gene homologs in a phage genome presents a novel way in which phages could influence their bacterial hosts, or neighbouring bacterial populations. This is the first time that these QS genes have been reported in a phage genome and their distribution both in C. difficile and phage genomes suggests that the agr3 locus undergoes horizontal gene transfer within this species. PMID:24475037

Hargreaves, Katherine R.; Kropinski, Andrew M.; Clokie, Martha R. J.

2014-01-01

421

QsrO a Novel Regulator of Quorum-Sensing and Virulence in Pseudomonas aeruginosa  

PubMed Central

In Pseudomonas aeruginosa, the production of many secreted virulence factors is controlled by a quorum-sensing (QS) circuit, constituted of transcriptional activators (LasR, RhlR, PqsR) and their cognate signaling molecules (3-oxo-C12-HSL, C4-HSL, PQS). QS is a cooperative behavior that is beneficial to a population but can be exploited by “QS-cheaters”, individuals which do not respond to the QS-signal, but can use public goods produced by QS-cooperators. In order to identify QS-deficient clones we designed a genetic screening based on a lasB-lacZ fusion. We isolated one clone (PT1617) deficient in QS-dependent gene expression and virulence factor production despite wild type lasR, rhlR and pqsR alleles. Whole genome sequencing of PT1617 revealed a 3,552 bp deletion encompassing ORFs PA2228-PA2229-PA2230 and the pslA gene. However, complementation of PT1617 by plasmid-encoded copies of these ORFs, did not restore QS. Unexpectedly, gene expression levels of ORFs PA2228, PA2227 (vqsM) and PA2222, located adjacent to the deletion, were 10 to 100 fold higher in mutant PT1617 than in PAO1. When expressed from a constitutive promoter on a plasmid, PA2226, alone was found to be sufficient to confer a QS-negative phenotype on PAO1 as well as on PA14. Co-expression of PA2226 and PA2225 in PAO1 further prevented induction of the type III secretion system. In summary, we have identified a novel genetic locus including ORF2226 termed qsrO (QS-repressing ORF), capable of down-regulating all three known QS-systems in P. aeruginosa. PMID:24551066

Köhler, Thilo; Ouertatani-Sakouhi, Hajer; Cosson, Pierre; van Delden, Christian

2014-01-01

422

Quorum Sensing: a Transcriptional Regulatory System Involved in the Pathogenicity of Burkholderia mallei  

PubMed Central

Numerous gram-negative bacterial pathogens regulate virulence factor expression by using a cell density mechanism termed quorum sensing (QS). An in silico analysis of the Burkholderia mallei ATCC 23344 genome revealed that it encodes at least two luxI and four luxR homologues. Using mass spectrometry, we showed that wild-type B. mallei produces the signaling molecules N-octanoyl-homoserine lactone and N-decanoyl-homoserine lactone. To determine if QS is involved in the virulence of B. mallei, we generated mutations in each putative luxIR homologue and tested the pathogenicities of the derivative strains in aerosol BALB/c mouse and intraperitoneal hamster models. Disruption of the B. mallei QS alleles, especially in RJ16 (bmaII) and RJ17 (bmaI3), which are luxI mutants, significantly reduced virulence, as indicated by the survival of mice who were aerosolized with 104 CFU (10 50% lethal doses [LD50s]). For the B. mallei transcriptional regulator mutants (luxR homologues), mutation of the bmaR5 allele resulted in the most pronounced decrease in virulence, with 100% of the challenged animals surviving a dose of 10 LD50s. Using a Syrian hamster intraperitoneal model of infection, we determined the LD50s for wild-type B. mallei and each QS mutant. An increase in the relative LD50 was found for RJ16 (bmaI1) (>967 CFU), RJ17 (bmaI3) (115 CFU), and RJ20 (bmaR5) (151 CFU) compared to wild-type B. mallei (<13 CFU). These findings demonstrate that B. mallei carries multiple luxIR homologues that either directly or indirectly regulate the biosynthesis of an essential virulence factor(s) that contributes to the pathogenicity of B. mallei in vivo. PMID:15501791

Ulrich, Ricky L.; DeShazer, David; Hines, Harry B.; Jeddeloh, Jeffrey A.

2004-01-01

423

Punicalagin inhibits Salmonella virulence factors and has anti-quorum-sensing potential.  

PubMed

Punicalagin, an essential component of pomegranate rind, has been demonstrated to possess antimicrobial activity against several food-borne pathogens, but its activity on the virulence of pathogens and its anti-quorum-sensing (anti-QS) potential have been rarely reported. This study investigated the efficacy of subinhibitory concentrations of punicalagin on Salmonella virulence factors and QS systems. A broth microdilution method was used to determine the MICs of punicalagin for 10 Salmonella strains. Motility assay and quantitative reverse transcription (RT)-PCR were performed to evaluate the effects of punicalagin on the virulence attributes and QS-related genes of Salmonella. The MICs of punicalagin for several Salmonella strains ranged from 250 to 1,000 ?g/ml. Motility assays showed that punicalagin, at 1/16× MIC and 1/32× MIC, significantly decreased bacterial swimming and swarming motility, which corresponded to downregulation of the motility-related genes (fliA, fliY, fljB, flhC, and fimD) in RT-PCR assays. RT-PCR also revealed that punicalagin downregulated the expression of most of the selected genes involved in Salmonella virulence. Moreover, a QS inhibition assay indicated that punicalagin dose dependently inhibited the production of violacein by Chromobacterium violaceum and repressed the expression of QS-related genes (sdiA and srgE) in Salmonella. In addition, punicalagin significantly reduced Salmonella invasion of colonic cells (P<0.01) with no impact on adhesion. These findings suggest that punicalagin has the potential to be developed as an alternative or supplemental agent for prevention of Salmonella infection. PMID:25085489

Li, Guanghui; Yan, Chunhong; Xu, Yunfeng; Feng, Yuqing; Wu, Qian; Lv, Xiaoying; Yang, Baowei; Wang, Xin; Xia, Xiaodong

2014-10-01

424

Quorum sensing controls hyphal initiation in Candida albicans through Ubr1-mediated protein degradation  

PubMed Central

Candida albicans is the most common cause of invasive fungal infections in humans. Its ability to undergo the morphological transition from yeast to hyphal growth forms is critical for its pathogenesis. Hyphal initiation requires the activation of the cAMP-PKA pathway, which down-regulates the expression of NRG1, the major repressor of hyphal development. Hyphal initiation also requires inoculation of a small amount of C. albicans cells from overnight culture to fresh medium. This inoculation releases the inhibition from farnesol, a quorum-sensing molecule of C. albicans, that accumulated in the spent medium. Here, we show that farnesol inhibits hyphal initiation mainly through blocking the protein degradation of Nrg1. Through screening a kinase mutant library, we identified Sok1 as the kinase required for Nrg1 degradation during inoculation. SOK1 expression is transiently activated on inoculation during hyphal initiation, and overexpression of SOK1 overcomes the farnesol-mediated inhibition of hyphal initiation. Screening a collection of transcription factor mutants, the homeodomain-containing transcription repressor Cup9 is found to be responsible for the repression of SOK1 expression in response to farnesol inhibition. Interestingly, farnesol inhibits Cup9 degradation mediated by the N-end rule E3 ubiquitin ligase, Ubr1. Therefore, hyphal initiation requires both the cAMP-PKA pathway-dependent transcriptional down-regulation of NRG1 and Sok1-mediated degradation of Nrg1 protein. The latter is triggered by the release from farnesol inhibition of Cup9 degradation and consequently, derepression of SOK1 transcription. Neither pathway alone is sufficient for hyphal initiation. PMID:24449897

Lu, Yang; Su, Chang; Unoje, Ohimai; Liu, Haoping

2014-01-01

425

Regulation of universal stress protein genes by quorum sensing and RpoS in Burkholderia glumae.  

PubMed

Burkholderia glumae possesses a quorum-sensing (QS) system mediated by N-octanoyl-homoserine lactone (C(8)-HSL) and its cognate receptor TofR. TofR/C(8)-HSL regulates the expression of a transcriptional regulator, qsmR. We identified one of the universal stress proteins (Usps), Usp2, from a genome-wide analysis of QS-dependent proteomes of B. glumae. In the whole genome of B. glumae BGR1, 11 usp genes (usp1 to usp11) were identified. Among the stress conditions tested, usp1 and usp2 mutants died 1 h after heat shock stress, whereas the other usp mutants and the wild-type strain survived for more than 3 h at 45°C. The expressions of all usp genes were positively regulated by QS, directly by QsmR. In addition, the expressions of usp1 and usp2 were dependent on RpoS in the stationary phase, as confirmed by the direct binding of RpoS-RNA holoenzyme to the promoter regions of the usp1 and usp2 genes. The expression of usp1 was upregulated upon a temperature shift from 37°C to either 28°C or 45°C, whereas the expression of usp2 was independent of temperature stress. This indicates that the regulation of usp1 and usp2 expression is different from what is known about Escherichia coli. Compared to the diverse roles of Usps in E. coli, Usps in B. glumae are dedicated to heat shock stress. PMID:22178971

Kim, Hongsup; Goo, Eunhye; Kang, Yongsung; Kim, Jinwoo; Hwang, Ingyu

2012-03-01

426

Regulation of Universal Stress Protein Genes by Quorum Sensing and RpoS in Burkholderia glumae  

PubMed Central

Burkholderia glumae possesses a quorum-sensing (QS) system mediated by N-octanoyl-homoserine lactone (C8-HSL) and its cognate receptor TofR. TofR/C8-HSL regulates the expression of a transcriptional regulator, qsmR. We identified one of the universal stress proteins (Usps), Usp2, from a genome-wide analysis of QS-dependent proteomes of B. glumae. In the whole genome of B. glumae BGR1, 11 usp genes (usp1 to usp11) were identified. Among the stress conditions tested, usp1 and usp2 mutants died 1 h after heat shock stress, whereas the other usp mutants and the wild-type strain survived for more than 3 h at 45°C. The expressions of all usp genes were positively regulated by QS, directly by QsmR. In addition, the expressions of usp1 and usp2 were dependent on RpoS in the stationary phase, as confirmed by the direct binding of RpoS-RNA holoenzyme to the promoter regions of the usp1 and usp2 genes. The expression of usp1 was upregulated upon a temperature shift from 37°C to either 28°C or 45°C, whereas the expression of usp2 was independent of temperature stress. This indicates that the regulation of usp1 and usp2 expression is different from what is known about Escherichia coli. Compared to the diverse roles of Usps in E. coli, Usps in B. glumae are dedicated to heat shock stress. PMID:22178971

Kim, Hongsup; Goo, Eunhye; Kang, Yongsung; Kim, Jinwoo

2012-01-01

427

The DSF Quorum Sensing System Controls the Positive Influence of Stenotrophomonas maltophilia on Plants  

PubMed Central

The interaction of the Gram-negative bacterium Stenotrophomonas maltophilia with eukaryotes can improve overall plant growth and health, but can also cause opportunistic infections in humans. While the quorum sensing molecule DSF (diffusible signal factor) is responsible for the regulation of phenotypes in pathogenic Stenotrophomonas, up until now, no beneficial effects were reported to be controlled by it. Our objective was to study the function of DSF in the plant growth promoting model strain S. maltophilia R551-3 using functional and transcriptomic analyses. For this purpose, we compared the wild-type strain with a mutant deficient in the rpfF (regulation of pathogenicity factors) gene that is essential for the synthesis of DSF. Oilseed rape seeds treated with the wild-type strain showed a statistically significant increase in germination rate compared with those treated with the rpfF mutant. Similarly, the wild-type strain exhibited better plant growth promotion and a greater efficiency in colonizing oilseed rape compared to the mutant strain. Moreover, only the wild-type was capable of forming structured cell aggregates both in vitro and in the rhizosphere, a characteristic mediated by DSF. Gene transcription analyses showed that numerous genes known to play a role in plant colonization (e.g. chemotaxis, cell motility, biofilm formation, multidrug efflux pumps) are controlled by the rpf/DSF system in S. maltophilia. In addition, we detected new potential functions of spermidine, primarily for both growth promotion and stress protection. Overall, our results showed a correspondence between the regulation of DSF and the positive interaction effect with the plant host. PMID:23874407

Alavi, Peyman; Müller, Henry; Cardinale, Massimiliano; Zachow, Christin; Sánchez, María B.; Martínez, José Luis; Berg, Gabriele

2013-01-01

428

Private link between signal and response in Bacillus subtilis quorum sensing.  

PubMed

Bacteria coordinate their behavior using quorum sensing (QS), whereby cells secrete diffusible signals that generate phenotypic responses associated with group living. The canonical model of QS is one of extracellular signaling, where signal molecules bind to cognate receptors and cause a coordinated response across many cells. Here we study the link between QS input (signaling) and QS output (response) in the ComQXPA QS system of Bacillus subtilis by characterizing the phenotype and fitness of comQ null mutants. These lack the enzyme to produce the ComX signal and do not activate the ComQXPA QS system in other cells. In addition to the activation effect of the signal, however, we find evidence of a second, repressive effect of signal production on the QS system. Unlike activation, which can affect other cells, repression acts privately: the de-repression of QS in comQ cells is intracellular and only affects mutant cells lacking ComQ. As a result, the QS signal mutants have an overly responsive QS system and overproduce the secondary metabolite surfactin in the presence of the signal. This surfactin overproduction is associated with a strong fitness cost, as resources are diverted away from primary metabolism. Therefore, by acting as a private QS repressor, ComQ may be protected against evolutionary competition from loss-of-function mutations. Additionally, we find that surfactin participates in a social selection mechanism that targets signal null mutants in coculture with signal producers. Our study shows that by pleiotropically combining intracellular and extracellular signaling, bacteria may generate evolutionarily stable QS systems. PMID:24425772

Oslizlo, Anna; Stefanic, Polonca; Dogsa, Iztok; Mandic-Mulec, Ines

2014-01-28

429

Growth Phase-Differential Quorum Sensing Regulation of Anthranilate Metabolism in Pseudomonas aeruginosa  

PubMed Central

Pseudomonas quinolone signal (PQS) plays a role in the regulation of virulence genes and it is intertwined in the las/rhl quorum sensing (QS) circuits of Pseudomonas aeruginosa. PQS is synthesized from anthranilate by pqsA-D and pqsH whose expression is influenced by the las/rhl systems. Since anthranilate can be degraded by functions of antABC and catBCA, PQS synthesis might be regulated by the balance between the expression of the pqsA-D/phnAB, pqsH, antABC, and catBCA gene loci. antA and catA are repressed by LasR during log phase and activated by RhlR in late stationary phase, whereas pqsA-E/phnAB is activated by LasR in log phase and repressed by RhlR. QscR represses both but each repression occurs in a different growth phase. This growth phasedifferential regulation appears to be accomplished by the antagonistic interplay of LasR, RhlR, and QscR, mediated by two intermediate regulators, AntR and PqsR, and their cofactors, anthranilate and PQS, where the expressions of antR and pqsR and the production of anthranilate and PQS are growth phase-differentially regulated by QS systems. Especially, the anthranilate level increases in an RhlRdependent manner at late stationary phase. From these results, we suggest that RhlR and LasR regulate the anthranilate metabolism in a mutually antagonistic and growth phase-differential manner by affecting both the expressions and activities of AntR and PqsR, and that QscR also phase-differentially represses both LasR and RhlR functions in this regulation. PMID:21614486

Choi, Yusang; Park, Ha-Young; Park, Seong Joon; Park, Su-Jin; Kim, Soo-Kyoung; Ha, Changwan; Im, Su-Jin; Lee, Joon-Hee

2011-01-01

430

Bacterial response to siderophore and quorum-sensing chemical signals in the seawater microbial community  

PubMed Central

Background Oceans are iron-deficient and nutrient-poor environments. These conditions impart limitations on our understanding of and our ability to identify microorganisms from the marine environment. However, less of knowledge on the influence of siderophores and N-acyl homoserinelactone as interspecies communication signals on the bacterial diversity of seawater has been understood. Results In the presence of 0.1 nM of the commercial siderophore desferroixamine and the known quorum-sensing chemical signals, synthetic N-(3-oxo)-hexanoylhomoserine lactone (0.1 nM) or N-octanoylhomoserine lactone (0.1 nM), the total numbers of bacteria in S9905 seawater increased nearly three-fold, and nearly eight-fold in S0011 seawater as determined by DAPI staining and counting, and increased three-fold by counting colony forming units in S9905 seawater after 7 days of incubation. Similar bacterial changes in bacterial abundance were observed when high concentration of desferroixamine (1 ?M) and each of homoserine lactone compounds (1 ?M) were presented in seawater samples. The number of cultivable bacterial species observed was also found to increase from 3 (without addition) to 8 (with additions) including three unknown species which were identified by phylogenetic analysis of 16S rDNA sequences. The growth of unknown species was found to be related to their siderophore production with response to the addition of desferroixamine and N-acyl homoserine lactones under iron-limited conditions. Conclusion Artificial addition of siderophores and HSLs may be a possible method to aid in the identification and isolation of marine bacterial species which are thought to be unknown. PMID:11716787

Guan, Le Luo; Kamino, Kei

2001-01-01

431

Identification and Characterization of a Second Quorum-Sensing System in Agrobacterium tumefaciens A6  

PubMed Central

Quorum sensing (QS) is a widespread mechanism of bacterial communication in which individual cells produce and respond to small chemical signals. In Agrobacterium tumefaciens, an acylhomoserine lactone-dependent QS mechanism is known to regulate the replication and conjugation of the tumor-inducing (Ti) plasmid. Most of the QS regulatory proteins are encoded within the Ti plasmid. Among them, TraI is the LuxI-type enzyme synthesizing the QS signal N-3-oxooctanoyl-l-homoserine lactone (3OC8HSL), TraR is the LuxR-type transcriptional factor that recognizes 3OC8HSL, and TraM is an antiactivator that antagonizes TraR. Recently, we identified a TraM homolog encoded by the traM2 gene in the chromosomal background of A. tumefaciens A6. In this study, we further identified additional homologs (TraI2 and TraR2) of TraI and TraR in this strain. We showed that similar to TraI, TraI2 could predominantly synthesize the QS signal 3OC8HSL. We also showed that TraR2 could recognize 3OC8HSL and activate the tra box-containing promoters as efficiently as TraR. Further analysis showed that traM2, traI2, and traR2 are physically linked on a mobile genetic element that is not related to the Ti plasmid. These findings indicate that A. tumefaciens A6 carries a second QS system that may play a redundant role in the regulation of the replication and conjugation of the Ti plasmid. PMID:24464459

Wang, Chao; Yan, Chunlan; Fuqua, Clay

2014-01-01

432

Characterization of Type 2 Quorum Sensing in Klebsiella pneumoniae and Relationship with Biofilm Formation  

PubMed Central

Quorum sensing is a process by which bacteria communicate by using secreted chemical signaling molecules called autoinducers. Many bacterial species modulate the expression of a wide variety of physiological functions in response to changes in population density by this mechanism. In this study, the opportunistic pathogen Klebsiella pneumoniae was observed to secrete type 2 signaling molecules. A homologue of luxS, the gene required for AI-2 synthesis in Vibrio harveyi, was isolated from the K. pneumoniae genome. A V. harveyi bioassay showed the luxS functionality in K. pneumoniae and its ability to complement the luxS-negative phenotype of Escherichia coli DH5?. Autoinducer activity was detected in the supernatant, and maximum expression of specific messengers detected by quantitative reverse transcription-PCR analysis occurred during the late exponential phase. The highest levels of AI-2 were observed in minimal medium supplemented with glycerol. To determine the potential role of luxS in colonization processes, a K. pneumoniae luxS isogenic mutant was constructed and tested for its capacity to form biofilms in vitro on an abiotic surface and to colonize the intestinal tract in a murine model. No difference was observed in the level of intestinal colonization between the wild-type strain and the luxS mutant. Microscopic analysis of biofilm structures revealed that the luxS mutant was able to form a mature biofilm but with reduced capacities in the development of microcolonies, mostly in the early steps of biofilm formation. These data suggest that a LuxS-dependent signal plays a role in the early stages of biofilm formation by K. pneumoniae. PMID:15805533

Balestrino, Damien; Haagensen, Janus A. J.; Rich, Chantal; Forestier, Christiane

2005-01-01

433

Phylogenetically Novel LuxI/LuxR-Type Quorum Sensing Systems Isolated Using a Metagenomic Approach  

PubMed Central

A great deal of research has been done to understand bacterial cell-to-cell signaling systems, but there is still a large gap in our current knowledge because the majority of microorganisms in natural environments do not have cultivated representatives. Metagenomics is one approach to identify novel quorum sensing (QS) systems from uncultured bacteria in environmental samples. In this study, fosmid metagenomic libraries were constructed from a forest soil and an activated sludge from a coke plant, and the target genes were detected using a green fluorescent protein (GFP)-based Escherichia coli biosensor strain whose fluorescence was screened by spectrophotometry. DNA sequence analysis revealed two pairs of new LuxI family N-acyl-l-homoserine lactone (AHL) synthases and LuxR family transcriptional regulators (clones N16 and N52, designated AubI/AubR and AusI/AusR, respectively). AubI and AusI each produced an identical AHL, N-dodecanoyl-l-homoserine lactone (C12-HSL), as determined by nuclear magnetic resonance (NMR) and mass spectrometry. Phylogenetic analysis based on amino acid sequences suggested that AusI/AusR was from an uncultured member of the Betaproteobacteria and AubI/AubR was very deeply branched from previously described LuxI/LuxR homologues in isolates of the Proteobacteria. The phylogenetic position of AubI/AubR indicates that they represent a QS system not acquired recently from the Proteobacteria by horizontal gene transfer but share a more ancient ancestry. We demonstrated that metagenomic screening is useful to provide further insight into the phylogenetic diversity of bacterial QS systems by describing two new LuxI/LuxR-type QS systems from uncultured bacteria. PMID:22983963

Nasuno, Eri; Fujita, Masaki J.; Nakatsu, Cindy H.; Kamagata, Yoichi; Hanada, Satoshi

2012-01-01

434

Quorum-sensing inhibitory compounds from extremophilic microorganisms isolated from a hypersaline cyanobacterial mat.  

PubMed

In this study, extremely halophilic and moderately thermophilic microorganisms from a hypersaline microbial mat were screened for their ability to produce antibacterial, antidiatom, antialgal, and quorum-sensing (QS) inhibitory compounds. Five bacterial strains belonging to the genera Marinobacter and Halomonas and one archaeal strain belonging to the genus Haloterrigena were isolated from a microbial mat. The strains were able to grow at a maximum salinity of 22-25 % and a maximum temperature of 45-60 °C. Hexanes, dichloromethane, and butanol extracts from the strains inhibited the growth of at least one out of nine human pathogens. Only butanol extracts of supernatants of Halomonas sp. SK-1 inhibited growth of the microalga Dunaliella salina. Most extracts from isolates inhibited QS of the acyl homoserine lactone producer and reporter Chromobacterium violaceum CV017. Purification of QS inhibitory dichloromethane extracts of Marinobacter sp. SK-3 resulted in isolation of four related diketopiperazines (DKPs): cyclo(L-Pro-L-Phe), cyclo(L-Pro-L-Leu), cyclo(L-Pro-L-isoLeu), and cyclo(L-Pro-D-Phe). QS inhibitory properties of these DKPs were tested using C. violaceum CV017 and Escherichia coli-based QS reporters (pSB401 and pSB1075) deficient in AHL production. Cyclo(L-Pro-L-Phe) and cyclo(L-Pro-L-isoLeu) inhibited QS-dependent production of violacein by C. violaceum CV017. Cyclo(L-Pro-L-Phe), cyclo(L-Pro-L-Leu), and cyclo(L-Pro-L-isoLeu) reduced QS-dependent luminescence of the reporter E. coli pSB401 induced by 3-oxo-C6-HSL. Our study demonstrated the ability of halophilic and moderately thermophilic strains from a hypersaline microbial mat to produce biotechnologically relevant compounds that could be used as antifouling agents. PMID:23645384

Abed, Raeid M M; Dobretsov, Sergey; Al-Fori, Marwan; Gunasekera, Sarath P; Sudesh, Kumar; Paul, Valerie J

2013-07-01

435

Quorum Sensing Coordinates Brute Force and Stealth Modes of Infection in the Plant Pathogen Pectobacterium atrosepticum  

PubMed Central

Quorum sensing (QS) in vitro controls production of plant cell wall degrading enzymes (PCWDEs) and other virulence factors in the soft rotting enterobacterial plant pathogen Pectobacterium atrosepticum (Pba). Here, we demonstrate the genome-wide regulatory role of QS in vivo during the Pba–potato interaction, using a Pba-specific microarray. We show that 26% of the Pba genome exhibited differential transcription in a QS (expI-) mutant, compared to the wild-type, suggesting that QS may make a greater contribution to pathogenesis than previously thought. We identify novel components of the QS regulon, including the Type I and II secretion systems, which are involved in the secretion of PCWDEs; a novel Type VI secretion system (T6SS) and its predicted substrates Hcp and VgrG; more than 70 known or putative regulators, some of which have been demonstrated to control pathogenesis and, remarkably, the Type III secretion system and associated effector proteins, and coronafacoyl-amide conjugates, both of which play roles in the manipulation of plant defences. We show that the T6SS and a novel potential regulator, VirS, are required for full virulence in Pba, and propose a model placing QS at the apex of a regulatory hierarchy controlling the later stages of disease progression in Pba. Our findings indicate that QS is a master regulator of phytopathogenesis, controlling multiple other regulators that, in turn, co-ordinately regulate genes associated with manipulation of host defences in concert with the destructive arsenal of PCWDEs that manifest the soft rot disease phenotype. PMID:18566662

Liu, Hui; Coulthurst, Sarah J.; Pritchard, Leighton; Hedley, Peter E.; Ravensdale, Michael; Humphris, Sonia; Burr, Tom; Takle, Gunnhild; Brurberg, May-Bente; Birch, Paul R. J.; Salmond, George P. C.; Toth, Ian K.

2008-01-01

436

Quorum sensing coordinates brute force and stealth modes of infection in the plant pathogen Pectobacterium atrosepticum.  

PubMed

Quorum sensing (QS) in vitro controls production of plant cell wall degrading enzymes (PCWDEs) and other virulence factors in the soft rotting enterobacterial plant pathogen Pectobacterium atrosepticum (Pba). Here, we demonstrate the genome-wide regulatory role of QS in vivo during the Pba-potato interaction, using a Pba-specific microarray. We show that 26% of the Pba genome exhibited differential transcription in a QS (expI-) mutant, compared to the wild-type, suggesting that QS may make a greater contribution to pathogenesis than previously thought. We identify novel components of the QS regulon, including the Type I and II secretion systems, which are involved in the secretion of PCWDEs; a novel Type VI secretion system (T6SS) and its predicted substrates Hcp and VgrG; more than 70 known or putative regulators, some of which have been demonstrated to control pathogenesis and, remarkably, the Type III secretion system and associated effector proteins, and coronafacoyl-amide conjugates, both of which play roles in the manipulation of plant defences. We show that the T6SS and a novel potential regulator, VirS, are required for full virulence in Pba, and propose a model placing QS at the apex of a regulatory hierarchy controlling the later stages of disease progression in Pba. Our findings indicate that QS is a master regulator of phytopathogenesis, controlling multiple other regulators that, in turn, co-ordinately regulate genes associated with manipulation of host defences in concert with the destructive arsenal of PCWDEs that manifest the soft rot disease phenotype. PMID:18566662

Liu, Hui; Coulthurst, Sarah J; Pritchard, Leighton; Hedley, Peter E; Ravensdale, Michael; Humphris, Sonia; Burr, Tom; Takle, Gunnhild; Brurberg, May-Bente; Birch, Paul R J; Salmond, George P C; Toth, Ian K

2008-06-01

437

Synthetic analogs of bacterial quorum sensors  

DOEpatents

Bacterial quorum-sensing molecule analogs having the following structures: ##STR00001## and methods of reducing bacterial pathogenicity, comprising providing a biological system comprising pathogenic bacteria which produce natural quorum-sensing molecule; providing a synthetic bacterial quorum-sensing molecule having the above structures and introducing the synthetic quorum-sensing molecule into the biological system comprising pathogenic bacteria. Further is provided a method of targeted delivery of an antibiotic, comprising providing a synthetic quorum-sensing molecule; chemically linking the synthetic quorum-sensing molecule to an antibiotic to produce a quorum-sensing molecule-antibiotic conjugate; and introducing the conjugate into a biological system comprising pathogenic bacteria susceptible to the antibiotic.

Iyer, Rashi S.; Ganguly, Kumkum; Silks, Louis A.

2013-01-08

438

Synthetic analogs of bacterial quorum sensors  

SciTech Connect

Bacterial quorum-sensing molecule analogs having the following structures: ##STR00001## and methods of reducing bacterial pathogenicity, comprising providing a biological system comprising pathogenic bacteria which produce natural quorum-sensing molecule; providing a synthetic bacterial quorum-sensing molecule having the above structures and introducing the synthetic quorum-sensing molecule into the biological system comprising pathogenic bacteria. Further is provided a method of targeted delivery of an antibiotic, comprising providing a synthetic quorum-sensing molecule; chemically linking the synthetic quorum-sensing molecule to an antibiotic to produce a quorum-sensing molecule-antibiotic conjugate; and introducing the conjugate into a biological system comprising pathogenic bacteria susceptible to the antibiotic.

Iyer, Rashi (Los Alamos, NM); Ganguly, Kumkum (Los Alamos, NM); Silks, Louis A. (Los Alamos, NM)

2011-12-06

439

Guava leaf extract inhibits quorum-sensing and Chromobacterium violaceum induced lysis of human hepatoma cells: whole transcriptome analysis reveals differential gene expression.  

PubMed

Quorum sensing (QS) is a process mediated via small molecules termed autoinducers (AI) that allow bacteria to respond and adjust according to the cell population density by altering the expression of multitudinous genes. Since QS governs numerous bioprocesses in bacteria, including virulence, its inhibition promises to be an ideal target for the development of novel therapeutics. We found that the aqueous leaf extract of Psidium guajava (GLE) exhibited anti-QS properties as evidenced by inhibition of violacein production in Chromobacterium violaceum and swarming motility of Pseudomonas aeruginosa. The gram-negative bacterium, C. violaceum is a rare pathogen with high mortality rate. In this study, perhaps for the first time, we identified the target genes of GLE in C. violaceum MTCC 2656 by whole transcriptome analysis on Ion Torrent. Our data revealed that GLE significantly down-regulated 816 genes at least three fold, with p value ? 0.01, which comprises 19% of the C. violaceum MTCC 2656 genome. These genes were distributed throughout the genome and were associated with virulence, motility and other cellular processes, many of which have been described as quorum regulated in C. violaceum and other gram negative bacteria. Interestingly, GLE did not affect the growth of the bacteria. However, consistent with the gene expression pattern, GLE treated C. violaceum cells were restrained from causing lysis of human hepatoma cell line, HepG2, indicating a positive relationship between the QS-regulated genes and pathogenicity. Overall, our study proposes GLE as a QS inhibitor (QSI) with the ability to attenuate virulence without affecting growth. To the best of our knowledge, this is the first report which provides with a plausible set of candidate genes regulated by the QS system in the neglected pathogen C. violaceum. PMID:25229331

Ghosh, Runu; Tiwary, Bipransh Kumar; Kumar, Anoop; Chakraborty, Ranadhir

2014-01-01

440

Small molecule probes of the receptor binding site in the Vibrio cholerae CAI-1 quorum sensing circuit  

PubMed Central

Based on modification of separate structural features of the Vibrio cholerae quorum sensing signal, (S)-3-hydroxytridecan-4-one (CAI-1), three focused compound libraries have been synthesized and evaluated for biological activity. Modifications to the acyl tail and ?-hydroxy ketone typically provided agonists with activities correlated to tail length and conservative changes to the hydroxy ketone. Among the molecules identified within this collection of agonists is Am-CAI-1 (B11), which is among the most potent agonists reported to date with an EC50 of 0.21 ?M. Modifications to the ethyl side chain delivered molecules with both agonist and antagonist activity, including m-OH-Ph-CAI-1 (C13) which is the most potent antagonist reported to date with an IC50 of 36 ?M. The molecules described in this manuscript are anticipated to serve as valuable tools in the study of quorum sensing in Vibrio cholerae and provide new leads in the development of an antivirulence therapy against this human pathogen. PMID:22001326

Bolitho, Megan E.; Perez, Lark J.; Koch, Matthew J.; Ng, Wai-Leung; Bassler, Bonnie L; Semmelhack, Martin F.

2013-01-01