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Sample records for vulnificus produces quorum

  1. Vibrio vulnificus produces quorum sensing signals of the AHL-class

    DEFF Research Database (Denmark)

    Valiente, E.; Bruhn, Jesper Bartholin; Nielsen, Kristian Fog

    2009-01-01

    Vibrio vulnificus is an aquatic pathogenic bacterium that can cause vibriosis in humans and fish. The species is subdivided into three biotypes with the fish-virulent strains belonging to biotype 2. The quorum sensing (QS) phenomenon mediated by furanosyl borate diester or autoinducer 2 (AI-2) ha...... biotype 2 strains. No known AHL-related gene was detected by PCR or Southern blot suggesting that AHL-related genes in V. vulnificus are different from those found in other Gram-negative bacteria....... was detected when AHL-positive strains were grown in low-nutrient medium [modified sea water yeast extract (MSWYE)] but not in rich media (tryptic soy broth or brain–heart infusion) and its production was enhanced when blood factors were added to MSWYE. C4-HL was detected in vivo, in eels infected with AHL-positive...

  2. Quorum sensing signals are produced by Aeromonas salmonicida and quorum sensing inhibitors can reduce production of a potential virulence factor

    DEFF Research Database (Denmark)

    Rasch, Maria; Kastbjerg, Vicky Gaedt; Bruhn, Jesper Bartholin

    2007-01-01

    of Aeromonas salmonicida strains. All 31 typical strains were AHL producers as were 21 of 26 atypical strains, but on a strain population basis, production of virulence factors such as protease, lipase, A-layer or pigment did not correlate with the production and accumulation of AHLs in the growth medium....... Pigment production was only observed in broth under highly aerated conditions. Quorum sensing inhibitors (QSIs) are compounds that specifically block QS systems without affecting bacterial growth and 2 such compounds, sulphur-containing AHL-analogues, reduced production of protease in a typical strain...

  3. Secondary metabolites produced by marine streptomyces as antibiofilm and quorum-sensing inhibitor of uropathogen Proteus mirabilis.

    Science.gov (United States)

    Younis, Khansa Mohammed; Usup, Gires; Ahmad, Asmat

    2016-03-01

    Quorum-sensing regulates bacterial biofilm formation and virulence factors, thereby making it an interesting target for attenuating pathogens. In this study, we investigated anti-biofilm and anti-quorum-sensing compounds from secondary metabolites of halophiles marine streptomyces against urinary catheter biofilm forming Proteus mirabilis without effect on growth viability. A total of 40 actinomycetes were isolated from samples collected from different places in Iraq including marine sediments and soil samples. Fifteen isolates identified as streptomyces and their supernatant screened as anti-quorum-sensing by inhibiting quorum-sensing regulated prodigiosin biosynthesis of Serratia marcescens strain Smj-11 as a reporter strain. Isolate Sediment Lake Iraq (sdLi) showed potential anti-quorum-sensing activity. Out of 35 clinical isolates obtained from Urinary catheter used by patient at the Universiti Kebangsaan Malaysia Medical Center, 22 isolates were characterized and identified as Proteus mirabilis. Isolate Urinary Catheter B4 (UCB4) showed the highest biofilm formation with highest resistance to used antibiotic and was chosen for further studies. Ethyl acetate secondary metabolites extract was produced from sdLi isolate. First, we determined the Minimum Inhibitory Concentration (MIC) of sdLi crude extract against UCB4 isolate, and all further experiments used concentrations below the MIC. Tests of subinhibitory concentrations of sdLi crude extract showed good inhibition against UCB4 isolate biofilm formation on urinary catheter and cover glass using Scanning electron microscopy and light microscopy respectively. The influence of sub-MIC of sdLi crude extract was also found to attenuate the quorum sensing (QS)-dependent factors such as hemolysin activity, urease activity, pH value, and motility of UCB4 isolate. Evidence is presented that these nontoxic secondary metabolites may act as antagonists of bacterial quorum sensing by competing with quorum-sensing signals

  4. Pseudomonas cremoricolorata Strain ND07 Produces N-acyl Homoserine Lactones as Quorum Sensing Molecules

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    Nina Yusrina Muhamad Yunos

    2014-06-01

    Full Text Available Quorum sensing (QS is a bacterial cell-to-cell communication system controlling QS-mediated genes which is synchronized with the population density. The regulation of specific gene activity is dependent on the signaling molecules produced, namely N-acyl homoserine lactones (AHLs. We report here the identification and characterization of AHLs produced by bacterial strain ND07 isolated from a Malaysian fresh water sample. Molecular identification showed that strain ND07 is clustered closely to Pseudomonas cremoricolorata. Spent culture supernatant extract of P. cremoricolorata strain ND07 activated the AHL biosensor Chromobacterium violaceum CV026. Using high resolution triple quadrupole liquid chromatography-mass spectrometry, it was confirmed that P. cremoricolorata strain ND07 produced N-octanoyl-l-homoserine lactone (C8-HSL and N-decanoyl-l-homoserine lactone (C10-HSL. To the best of our knowledge, this is the first documentation on the production of C10-HSL in P. cremoricolorata strain ND07.

  5. Survey on antimicrobial resistance patterns in Vibrio vulnificus and Vibrio cholerae non-O1/non-O139 in Germany reveals carbapenemase-producing Vibrio cholerae in coastal waters

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    Nadja eBier

    2015-10-01

    Full Text Available An increase in the occurrence of potentially pathogenic Vibrio species is expected for waters in Northern Europe as a consequence of global warming. In this context, a higher incidence of Vibrio infections is predicted for the future and forecasts suggest that people visiting and living at the Baltic Sea are at particular risk.This study aimed to investigate antimicrobial resistance patterns among Vibrio vulnificus and Vibrio cholerae non-O1/non-O139 isolates that could pose a public health risk. Antimicrobial susceptibility of 141 V. vulnificus and 184 V. cholerae non-O1/non-O139 strains isolated from German coastal waters (Baltic Sea and North Sea as well as from patients and retail seafood was assessed by broth microdilution and disk diffusion. Both species were susceptible to most of the agents tested (12 subclasses and no multidrug-resistance was observed. Among V. vulnificus isolates, non-susceptibility was exclusively found towards aminoglycosides. In case of V. cholerae, a noticeable proportion of strains was non-susceptible to aminopenicillins and aminoglycosides. In addition, resistance towards carbapenems, quinolones, and folate pathway inhibitors was sporadically observed. Biochemical testing indicated the production of carbapenemases with unusual substrate specificity in four environmental V. cholerae strains. Most antimicrobial agents recommended for treatment of V. vulnificus and V. cholerae non-O1/non-O139 infections were found to be effective in vitro. However, the occurrence of putative carbapenemase producing V. cholerae in German coastal waters is of concern and highlights the need for systematic monitoring of antimicrobial susceptibility in potentially pathogenic Vibrio spp. in Europe.

  6. Inhibiting effect of bioactive metabolites produced by mushroom cultivation on bacterial quorum sensing-regulated behaviors.

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    Zhu, Hu; Wang, Shou-Xian; Zhang, Shuai-Shuai; Cao, Chun-Xu

    2011-01-01

    This study aimed to search for novel quorum sensing (QS) inhibitors from mushroom and to analyze their inhibitory activity, with a view to their possible use in controlling detrimental infections. The bioactive metabolites produced by mushroom cultivation were tested for their abilities to inhibit QS-regulated behavior. All mushroom strains were cultivated in potato-dextrose medium by large-scale submerged fermentation. The culture supernatant was condensed into 0.2 vol by freeze-drying. The condensed supernatant was sterilized by filtration through a 0.22-μm membrane filter and added to Chromobacterium violaceum CV026 cultures, which were used to monitor QS inhibition. Inhibitory activity was measured by quantifying violacein production using a microplate reader. The results have revealed that, of 102 mushroom strains, the bioactive metabolites produced by 14 basidiomycetes were found to inhibit violacein production, a QS-regulated behavior in C. violaceum. Higher fungi can produce QS-inhibitory compounds. Copyright © 2011 S. Karger AG, Basel.

  7. Identity and effects of quorum sensing inhibitors produced by Penicillium species

    DEFF Research Database (Denmark)

    Rasmussen, Thomas Bovbjerg; Skindersø, Mette Elena; Bjarnsholt, Thomas

    2005-01-01

    Quorum sensing (QS) communication systems are thought to afford bacteria with a mechanism to strategically cause disease. One example is Pseudomonas aeruginosa, which infects immunocompromised individuals such as cystic fibrosis patients. The authors have previously documented that blockage of th...

  8. The plant pathogen Pantoea ananatis produces N-acylhomoserine lactone and causes center rot disease of onion by quorum sensing.

    Science.gov (United States)

    Morohoshi, Tomohiro; Nakamura, Yuta; Yamazaki, Go; Ishida, Akio; Kato, Norihiro; Ikeda, Tsukasa

    2007-11-01

    A number of gram-negative bacteria have a quorum-sensing system and produce N-acyl-l-homoserine lactone (AHL) that they use them as a quorum-sensing signal molecule. Pantoea ananatis is reported as a common colonist of wheat heads at ripening and causes center rot of onion. In this study, we demonstrated that P. ananatis SK-1 produced two AHLs, N-hexanoyl-l-homoserine lactone (C6-HSL) and N-(3-oxohexanoyl)-l-homoserine lactone (3-oxo-C6-HSL). We cloned the AHL-synthase gene (eanI) and AHL-receptor gene (eanR) and revealed that the deduced amino acid sequence of EanI/EanR showed high identity to those of EsaI/EsaR from P. stewartii. EanR repressed the ean box sequence and the addition of AHLs resulted in derepression of ean box. Inactivation of the chromosomal eanI gene in SK-1 caused disruption of exopolysaccharide (EPS) biosynthesis, biofilm formation, and infection of onion leaves, which were recovered by adding exogenous 3-oxo-C6-HSL. These results demonstrated that the quorum-sensing system involved the biosynthesis of EPS, biofilm formation, and infection of onion leaves in P. ananatis SK-1.

  9. Zoonose Vibrio vulnificus: meldingsplicht raadzaam

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    Dijkstra, A.; Haenen, O.L.M.; Moller, L.

    2010-01-01

    Op de lijst van meldingsplichtige infectieziekten komen een aantal zoönosen voor, zoals pest, rabiës en leptospirose. De relatief onbekende zoönotische Vibrio vulnificus valt opmerkelijk genoeg niet onder de meldingsplichtige infectieziekten. Juist vanwege het zeer agressieve beloop van een

  10. Effect of quorum sensing signals produced by seaweed-associated bacteria on carpospore liberation from Gracilaria dura

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    Ravindra Pal Singh

    2015-03-01

    Full Text Available Epiphytic and endophytic bacteria associated with green macroalgae Ulva (U. fasciata and U. lactuca and red macroalgae Gracilaria (G. corticata and G. dura have been identified from three different seasons to evaluate the effect of quorum sensing molecules on carpospores liberation from Gracilaria dura. The bacterial isolates belonging to the orders Bacillales, Pseudomonadales, Alteromonadales and Vibrionales were present in all seasons, whereas Actinomycetales and Enterobacteriales were confined to pre-monsoon and post-monsoon seasons, respectively. Among all the Gram-negative bacteria, seven isolates were found to produce different types of N-acyl homoserine lactones (AHLs. Interestingly, Shewanella algae produced five types of AHL: C4-HSL, HC4-HSL, C6-HSL, 3-oxo-C6-HSL and 3-oxo-C12-HSL. Subsequently, the AHLs producing bacterial isolates were screened for carpospore liberation from G. dura and these isolates were found to positively induce carpospore liberation over the control. Also, observed that carpospore liberation increased significantly in C4- and C6-HSL treated cystocarps. Sodium dodecyl sulfate and native polyacrylamide gel electrophoresis of the total protein of the C4- and C6-HSL-treated cystocarps showed two specific peptide bands of different molecular weights (50 kDa and 60 kDa as compared to the control, confirming their indirect effect on carpospore liberation.

  11. Quorum sensing is a key regulator for the antifungal and biocontrol activity of chitinase-producing Chromobacterium sp. C61.

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    Kim, In Seon; Yang, Si Young; Park, Seur Kee; Kim, Young Cheol

    2017-01-01

    Chromobacterium sp. strain C61 has strong biocontrol activity; however, the genetic and biochemical determinants of its plant disease suppression activity are not well understood. Here, we report the identification and characterization of two new determinants of its biocontrol activity. Transposon mutagenesis was used to identify mutants that were deficient in fungal suppression. One of these mutants had an insertion in a homologue of depD, a structural gene in the dep operon, that encodes a protein involved in non-ribosomal peptide synthesis. In the second mutant, the insertion was in a homologue of the luxI gene, which encodes a homoserine lactone synthase. The luxI(-) and depD(-) mutants had no antifungal activity in vitro and a dramatically reduced capacity to suppress various plant diseases in planta. Antifungal production and biocontrol were restored by complementation of the luxI(-) mutant. Other phenotypes associated with effective biological control, including motility and lytic enzyme secretion, were also affected by the luxI mutation. Biochemical analysis of ethyl acetate extracts of culture filtrates of the mutant and wild-type strains showed that a key antifungal compound, chromobactomycin, was produced by wild-type C61 and the complemented luxI(-) mutant, but not by the luxI(-) or depD(-) mutant. These data suggest that multiple biocontrol-related phenotypes are regulated by homoserine lactones in C61. Thus, quorum sensing plays an essential role in the biological control potential of diverse bacterial lineages. © 2016 BSPP and John Wiley & Sons Ltd.

  12. Quorum sensing signaling molecules produced by reference and emerging soft-rot bacteria (Dickeya and Pectobacterium spp..

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    Alexandre Crépin

    Full Text Available BACKGROUND: Several small diffusible molecules are involved in bacterial quorum sensing and virulence. The production of autoinducers-1 and -2, quinolone, indole and γ-amino butyrate signaling molecules was investigated in a set of soft-rot bacteria belonging to six Dickeya or Pectobacterium species including recent or emerging potato isolates. METHODOLOGY/PRINCIPAL FINDINGS: Using bacterial biosensors, immunoassay, and chromatographic analysis, we showed that soft-rot bacteria have the common ability to produce transiently during their exponential phase of growth the N-3-oxo-hexanoyl- or the N-3-oxo-octanoyl-l-homoserine lactones and a molecule of the autoinducer-2 family. Dickeya spp. produced in addition the indole-3-acetic acid in tryptophan-rich conditions. All these signaling molecules have been identified for the first time in the novel Dickeya solani species. In contrast, quinolone and γ-amino butyrate signals were not identified and the corresponding synthases are not present in the available genomes of soft-rot bacteria. To determine if the variations of signal production according to growth phase could result from expression modifications of the corresponding synthase gene, the respective mRNA levels were estimated by reverse transcriptase-PCR. While the N-acyl-homoserine lactone production is systematically correlated to the synthase expression, that of the autoinducer-2 follows the expression of an enzyme upstream in the activated methyl cycle and providing its precursor, rather than the expression of its own synthase. CONCLUSIONS/SIGNIFICANCE: Despite sharing the S-adenosylmethionine precursor, no strong link was detected between the production kinetics or metabolic pathways of autoinducers-1 and -2. In contrast, the signaling pathway of autoinducer-2 seems to be switched off by the indole-3-acetic acid pathway under tryptophan control. It therefore appears that the two genera of soft-rot bacteria have similarities but also

  13. Quorum Systems

    DEFF Research Database (Denmark)

    Förster, Klaus-Tycho; Wattenhofer, Roger

    2017-01-01

    What happens if a single server is no longer powerful enough to service all your customers? The obvious choice is to add more servers and to use the majority approach (e.g. Paxos, Chapter 2) to guarantee consistency. However, even if you buy one million servers, a client still has to access more ...... study the theory behind overlapping sets, known as quorum systems....

  14. Attenuation of Quorum Sensing Regulated Virulence of Pectobacterium carotovorum subsp. carotovorum through an AHL Lactonase Produced by Lysinibacillus sp. Gs50.

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    Sneha S Garge

    Full Text Available Quorum sensing (QS is a mechanism in which Gram negative bacterial pathogens sense their population density through acyl homoserine lactones (AHLs and regulate the expression of virulence factors. Enzymatic degradation of AHLs by lactonases, known as quorum quenching (QQ, is thus a potential strategy for attenuating QS regulated bacterial infections. We characterised the QQ activity of soil isolate Lysinibacillus sp. Gs50 and explored its potential for controlling bacterial soft rot of crop plants. Lysinibacillus sp. Gs50 inactivated AHL, which could be restored upon acidification, suggested that inactivation was due to the lactone ring hydrolysis of AHL. Heterologous expression of cloned gene for putative hydrolase (792 bp designated adeH from Lysinibacillus sp. Gs50 produced a ~29 kDa protein which degraded AHLs of varying chain length. Mass spectrometry analysis of AdeH enzymatic reaction product revealed that AdeH hydrolyses the lactone ring of AHL and hence is an AHL lactonase. Multiple sequence alignment of the amino acid sequence of AdeH showed that it belongs to the metallo- β- lactamase superfamily, has a conserved "HXHXDH" motif typical of AHL lactonases. KM for AdeH for C6HSL was found to be 3.089 μM and the specific activity was 0.8 picomol min-1μg-1. AdeH has not so far been reported from any Lysinibacillus sp. and has less than 40% identity with known AHL lactonases. Finally we found that Lysinibacillus sp. Gs50 can degrade AHL produced by Pectobacterium carotovorum subsp. carotovorum (Pcc, a common cause of soft rot. This QQ activity causes a decrease in production of plant cell wall degrading enzymes of Pcc and attenuates symptoms of soft rot in experimental infection of potato, carrot and cucumber. Our results demonstrate the potential of Lysinibacillus sp. Gs50 as a preventive and curative biocontrol agent.

  15. Environmental occurrence and clinical impact of Vibrio vulnificus and Vibrio parahaemolyticus: a European perspective.

    Science.gov (United States)

    Baker-Austin, Craig; Stockley, Louise; Rangdale, Rachel; Martinez-Urtaza, Jaime

    2010-02-01

    Vibrio vulnificus and Vibrio parahaemolyticus are ubiquitous Gram-negative bacterial pathogens found naturally in marine and estuarine waters, and are a leading cause of seafood-associated bacterial illness. These pathogens are commonly reported in the USA and in many Asian countries, including China, Japan and Taiwan; however, there is growing concern that V. vulnificus and V. parahaemolyticus may represent an important and increasing clinical problem in Europe. Several factors underlie the need for a greater understanding of these non-cholera vibrios within a European context. First, there is a growing body of evidence to suggest that V. vulnificus and V. parahaemolyticus infections are increasing, and tend to follow regional climatic trends, with outbreaks typically following episodes of unusually warm weather. Such findings are especially alarming given current predictions regarding warming of marine waters as a result of global climatic change. Second, a myriad of epidemiological factors may greatly increase the incidence as well as clinical burden of these pathogens - including increasing global consumption and trade of seafood produce coupled to an increase in the number of susceptible individuals consuming seafood produce. Finally, there is currently a lack of detailed surveillance information regarding non-cholerae Vibrio infections in Europe, as these pathogens are not notifiable in many countries, which probably masks the true clinical burden of many human infections. This review will present a pertinent overview of both the environmental occurrence and clinical impact of V. vulnificus and V. parahaemolyticus in Europe. © 2010 Crown copyright.

  16. Vibrio vulnificus induces mTOR activation and inflammatory responses in macrophages.

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    Dan-Li Xie

    Full Text Available Vibrio vulnificus (V. vulnificus, a Gram-negative marine bacterium, can cause life-threatening primary septicemia, especially in patients with liver diseases. How V. vulnificus affects the liver and how it acts on macrophages are not well understood. In this report, we demonstrated that V. vulnificus infection causes a strong inflammatory response, marked expansion of liver-resident macrophages, and liver damage in mice. We demonstrated further that V. vulnificus activates mTOR in macrophages and inhibition of mTOR differentially regulates V. vulnificus induced inflammatory responses, suggesting the possibility of targeting mTOR as a strategy to modulate V. vulnificus induced inflammatory responses.

  17. Autecology of Vibrio vulnificus and Vibrio parahaemolyticus in tropical waters

    Energy Technology Data Exchange (ETDEWEB)

    Rivera, S.; Lugo, T.; Hazen, T.C. [Univ. of Puerto Rico, Rio Piedras (Puerto Rico)

    1988-12-31

    Water and shellfish samples collected from estuaries, mangroves, and beaches along the coast of Puerto Rico were examined for Vibrio vulnificus and Vibrio parahaemolyticus. An array of water quality parameters were also measured simultaneous with bacteria sampling. Both species of vibrio were associated with estuary and mangrove locations, and neither was isolated from sandy beaches. Densities of V. vulnificus were negatively correlated with salinity, 10--15 ppt being optimal. V. parahaemolyticus was isolated from sites with salinities between 20 and 35 ppt, the highest densities occurring at 20 ppt. Densities of Vibrio spp. and V. parahaemolyticus for a tropical estuary surpassed those reported for temperate estuaries by several orders of magnitude. Both densities of total Vibrio spp. and V. parahaemolyticus in the water were directly related to densities of fecal coliforms, unlike V. vulnificus. The incidence of ONPG(+) strains among sucrose({minus}) Vibrio spp. served as an indicator of the frequency of V. vulnificus in this group. More than 63% of the V. vulnificus isolated were pathogenic. V. vulnificus and V. parahaemolyticus occupy clearly separate niches within the tropical estuarine-marine ecosystem.

  18. Can the natural diversity of quorum sensing advance synthetic biology?

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    Rene Michele Davis

    2015-03-01

    Full Text Available Quorum-sensing networks enable bacteria to sense and respond to chemical signals produced by neighboring bacteria. They are widespread: over one hundred morphologically and genetically distinct species of eubacteria are known to use quorum sensing to control gene expression. This diversity suggests the potential to use natural protein variants to engineer parallel, input-specific, cell-cell communication pathways. However, only three distinct signaling pathways, Lux, Las, and Rhl, have been adapted for and broadly used in engineered systems. The paucity of unique quorum-sensing systems and their propensity for crosstalk limits the usefulness of our current quorum-sensing toolkit. This review discusses the need for more signaling pathways, roadblocks to using multiple pathways in parallel, and strategies for expanding the quorum-sensing toolbox for synthetic biology.

  19. Quorum quenching enzymes.

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    Fetzner, Susanne

    2015-05-10

    Bacteria use cell-to-cell communication systems based on chemical signal molecules to coordinate their behavior within the population. These quorum sensing systems are potential targets for antivirulence therapies, because many bacterial pathogens control the expression of virulence factors via quorum sensing networks. Since biofilm maturation is also usually influenced by quorum sensing, quenching these systems may contribute to combat biofouling. One possibility to interfere with quorum sensing is signal inactivation by enzymatic degradation or modification. Such quorum quenching enzymes are wide-spread in the bacterial world and have also been found in eukaryotes. Lactonases and acylases that hydrolyze N-acyl homoserine lactone (AHL) signaling molecules have been investigated most intensively, however, different oxidoreductases active toward AHLs or 2-alkyl-4(1H)-quinolone signals as well as other signal-converting enzymes have been described. Several approaches have been assessed which aim at alleviating virulence, or biofilm formation, by reducing the signal concentration in the bacterial environment. These involve the application or stimulation of signal-degrading bacteria as biocontrol agents in the protection of crop plants against soft-rot disease, the use of signal-degrading bacteria as probiotics in aquaculture, and the immobilization or entrapment of quorum quenching enzymes or bacteria to control biofouling in membrane bioreactors. While most approaches to use quorum quenching as antivirulence strategy are still in the research phase, the growing number of organisms and enzymes known to interfere with quorum sensing opens up new perspectives for the development of innovative antibacterial strategies. Copyright © 2014 Elsevier B.V. All rights reserved.

  20. The physical basis of bacterial quorum communication

    CERN Document Server

    2015-01-01

    This book aims to educate physical scientists and quantitatively-oriented biologists on the application of physical experimentation and analysis, together with appropriate modeling, to understanding and interpreting microbial chemical communication and especially quorum sensing (QS). Quorum sensing describes a chemical communication behavior that is nearly universal among bacteria. Individual cells release a diffusible small molecule (an autoinducer) into their environment. A high concentration of this autoinducer serves as a signal of high population density, triggering new patterns of gene expression throughout the population. However QS is often much more complex than simple census-taking. Many QS bacteria produce and detect multiple autoinducers, which generate quorum signal cross talk with each other and with other bacterial species. QS gene regulatory networks operate in physically complex environments and respond to a range of inputs in addition to autoinducer signals. While many individual QS systems ...

  1. Quorum Sensing and Quorum Quenching in the Mediterranean Seagrass Posidonia oceanica Microbiota

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    Elodie Blanchet

    2017-07-01

    Full Text Available Posidonia oceanica (L. Delile is an endemic Mediterranean seagrass angiosperm. The taxonomic diversity of the Posidonia-associated microbiota has previously been inventoried using culture-based and culture-independent approaches. However, little is known about the type of chemical interactions that occur between the cells within this microbiota. In this study, we isolated 60 bacterial strains from the leaves and rhizomes of P. oceanica and evaluated their capacity to communicate through quorum sensing. We found 6 strains able to emit 8 different types of quorum sensing acyl homoserine lactones, identified through UHPLC-HRMS/MS after bioguided fractionation of large cultures. We also identified 19 strains able to produce furanosyl diester borate, another type of quorum sensing autoinducer. Also, 5 strains were found to produce quorum quenching compounds. Finally, as quorum sensing is known to be involved in biofilm production, we also tested whether strains positive to our biotests were able to produce biofilms. Collectively, these data reveal the importance of examining chemical interactions within this bacterial consortium associated with P. oceanica that could have an impact on the physiology of this key Mediterranean seagrass.

  2. Variable Virulence of Biotype 3 Vibrio vulnificus due to MARTX Toxin Effector Domain Composition.

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    Kim, Byoung Sik; Gavin, Hannah E; Satchell, Karla J F

    2017-01-01

    Vibrio vulnificus is an environmental organism that causes septic human infections characterized by high morbidity and mortality. The annual incidence and global distribution of this pathogen are increasing as ocean waters warm. Clinical strains exhibit variations in the primary virulence toxin, suggesting a potential for the emergence of new strains with altered virulence properties. A clonal outbreak of tilapia-associated wound infections in Israel serves as a natural experiment for the sudden emergence of a new V. vulnificus strain. The effector domain content of the multifunctional autoprocessing RTX (MARTX) toxin of the outbreak-associated biotype 3 (BT3) strains was previously shown to harbor a modification generated by recombination. The modification introduced an actin-induced adenylate cyclase effector domain (ExoY) and an effector domain that disrupts the Golgi organelle (DmX). Here, we report that the exchange of these effector domains for a putative progenitor biotype 1 toxin arrangement produces a toxin that slows the lysis kinetics of targeted epithelial cells but increases cellular rounding phenotypes in response to bacteria. In addition, replacing the biotype 3 toxin variant with the putative progenitor biotype 1 variant renders the resulting strain significantly more virulent in mice. This suggests that the exchange of MARTX effector domains during the emergence of BT3 generated a toxin with reduced toxin potency, resulting in decreased virulence of this outbreak-associated strain. We posit that selection for reduced virulence may serve as a route for this lethal infectious agent to enter the human food chain by allowing it to persist in natural hosts. IMPORTANCEVibrio vulnificus is a serious infection linked to climate change. The virulence capacity of these bacteria can vary by gene exchange, resulting in new variants of the primary virulence toxin. In this study, we tested whether the emergence of an epidemic strain of V. vulnificus with a

  3. Vibrio vulnificus-infektioner i Danmark sommeren 1994

    DEFF Research Database (Denmark)

    Bruun, Brita Grønbech; Frimodt-Møller, N; Dalsgaard, A.

    1996-01-01

    The clinical manifestations and epidemiological data of 11 patients infected with Vibrio vulnificus found in Denmark during the unusually warm summer of 1994 are reported. All patients had been exposed to seawater prior to illness, but none had consumed seafood. Nine patients, including four...

  4. Fremmedlegemeinfektioner--nyt om biofilm og quorum sensing

    DEFF Research Database (Denmark)

    Høiby, Niels; Johansen, Helle Krogh; Ciofu, Oana

    2007-01-01

    Biofilms are structured consortia of bacteria embedded in self-produced polymer matrix. Biofilms are resistant to antibiotics, disinfectives and phagocytosis. The persistence of foreign body infections is due to biofilms. Chronic P. aeruginosa lung infection in cystic fibrosis patients is a biofilm....... Bacteria in biofilms communicate by means of quorum sensing which activates genes for virulence factors. Biofilms can be prevented by antibiotic prophylaxis or early therapy or by quorum sensing inhibitors which make them susceptible to antibiotics and phagocytosis....

  5. Quorum Colorings of Graphs

    NARCIS (Netherlands)

    S.M. Heditniemi (Sandra); R.C. Laskar (R.C.); H.M. Mulder (Martyn)

    2012-01-01

    textabstractLet $G = (V,E)$ be a graph. A partition $\\pi = \\{V_1, V_2, \\ldots, V_k \\}$ of the vertices $V$ of $G$ into $k$ {\\it color classes} $V_i$, with $1 \\leq i \\leq k$, is called a {\\it quorum coloring} if for every vertex $v \\in V$, at least half of the vertices in the closed neighborhood

  6. Quorum-quenching limits quorum-sensing exploitation by signal-negative invaders

    Science.gov (United States)

    Some bacteria produce and perceive quorum-sensing (QS) signals that coordinate several behaviors, including the physiologically costly processes of exoenzyme production and plasmid transfer. In the case of plasmid transfer, the emergence of QS signal-altered invaders and their policing are poorly do...

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

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    Christopher N LaRock

    Full Text Available 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.

  8. Modulation of Quorum Sensing in Acylhomoserine Lactone-Producing or -Degrading Tobacco Plants Leads to Alteration of Induced Systemic Resistance Elicited by the Rhizobacterium Serratia marcescens 90-166

    Directory of Open Access Journals (Sweden)

    Choong-Min Ryu

    2013-06-01

    Full Text Available Numerous root-associated bacteria (rhizobacteria are known to elicit induced systemic resistance (ISR in plants. Bacterial cell-density-dependent quorum sensing (QS is thought to be important for ISR. Here, we investigated the role of QS in the ISR elicited by the rhizobacterium, Serratia marcescens strain 90–166, in tobacco. Since S. marcescens 90–166 produces at least three QS signals, QS-mediated ISR in strain 90–166 has been difficult to understand. Therefore, we investigated the ISR capacity of two transgenic tobacco (Nicotiana tabacum plants that contained either bacterial acylhomoserine lactone-producing (AHL or -degrading (AiiA genes in conjunction with S. marcescens 90–166 to induce resistance against bacterial and viral pathogens. Root application of S. marcescens 90–166 increased ISR to the bacterial pathogens, Pectobacterium carotovorum subsp. carotovorum and Pseudomonas syringae pv. tabaci, in AHL plants and decreased ISR in AiiA plants. In contrast, ISR to Cucumber mosaic virus was reduced in AHL plants treated with S. marcescens 90–166 but enhanced in AiiA plants. Taken together, these data indicate that QS-dependent ISR is elicited by S. marcescens 90–166 in a pathogen-dependent manner. This study provides insight into QS-dependent ISR in tobacco elicited by S. marcescens 90–166.

  9. Quorum sensing inhibition

    DEFF Research Database (Denmark)

    Persson, T.; Givskov, Michael Christian; Nielsen, J.

    2005-01-01

    Quorum sensing (QS) systems comprise a new therapeutic target potentially substitutive or complementary to traditional antibiotic treatment of chronic diseases. One route to disrupt the previously established interrelationship between pathogenesis and QS is by blocking the dual functioning signal...... analogs of the native signaling molecules and the other compounds lacking structural resemblance. Biological activity is rationalized on the basis of structure-activity relationships and structural insight into the target protein....

  10. The cabABC Operon Essential for Biofilm and Rugose Colony Development in Vibrio vulnificus.

    Directory of Open Access Journals (Sweden)

    Jin Hwan Park

    2015-09-01

    Full Text Available A transcriptome analysis identified Vibrio vulnificus cabABC genes which were preferentially expressed in biofilms. The cabABC genes were transcribed as a single operon. The cabA gene was induced by elevated 3',5'-cyclic diguanylic acid (c-di-GMP and encoded a calcium-binding protein CabA. Comparison of the biofilms produced by the cabA mutant and its parent strain JN111 in microtiter plates using crystal-violet staining demonstrated that CabA contributed to biofilm formation in a calcium-dependent manner under elevated c-di-GMP conditions. Genetic and biochemical analyses revealed that CabA was secreted to the cell exterior through functional CabB and CabC, distributed throughout the biofilm matrix, and produced as the biofilm matured. These results, together with the observation that CabA also contributes to the development of rugose colony morphology, indicated that CabA is a matrix-associated protein required for maturation, rather than adhesion involved in the initial attachment, of biofilms. Microscopic comparison of the structure of biofilms produced by JN111 and the cabA mutant demonstrated that CabA is an extracellular matrix component essential for the development of the mature biofilm structures in flow cells and on oyster shells. Exogenously providing purified CabA restored the biofilm- and rugose colony-forming abilities of the cabA mutant when calcium was available. Circular dichroism and size exclusion analyses revealed that calcium binding induces CabA conformational changes which may lead to multimerization. Extracellular complementation experiments revealed that CabA can assemble a functional matrix only when exopolysaccharides coexist. Consequently, the combined results suggested that CabA is a structural protein of the extracellular matrix and multimerizes to a conformation functional in building robust biofilms, which may render V. vulnificus to survive in hostile environments and reach a concentrated infective dose.

  11. The cabABC Operon Essential for Biofilm and Rugose Colony Development in Vibrio vulnificus

    Science.gov (United States)

    Park, Jin Hwan; Jo, Youmi; Jang, Song Yee; Kwon, Haenaem; Irie, Yasuhiko; Parsek, Matthew R.; Kim, Myung Hee; Choi, Sang Ho

    2015-01-01

    A transcriptome analysis identified Vibrio vulnificus cabABC genes which were preferentially expressed in biofilms. The cabABC genes were transcribed as a single operon. The cabA gene was induced by elevated 3′,5′-cyclic diguanylic acid (c-di-GMP) and encoded a calcium-binding protein CabA. Comparison of the biofilms produced by the cabA mutant and its parent strain JN111 in microtiter plates using crystal-violet staining demonstrated that CabA contributed to biofilm formation in a calcium-dependent manner under elevated c-di-GMP conditions. Genetic and biochemical analyses revealed that CabA was secreted to the cell exterior through functional CabB and CabC, distributed throughout the biofilm matrix, and produced as the biofilm matured. These results, together with the observation that CabA also contributes to the development of rugose colony morphology, indicated that CabA is a matrix-associated protein required for maturation, rather than adhesion involved in the initial attachment, of biofilms. Microscopic comparison of the structure of biofilms produced by JN111 and the cabA mutant demonstrated that CabA is an extracellular matrix component essential for the development of the mature biofilm structures in flow cells and on oyster shells. Exogenously providing purified CabA restored the biofilm- and rugose colony-forming abilities of the cabA mutant when calcium was available. Circular dichroism and size exclusion analyses revealed that calcium binding induces CabA conformational changes which may lead to multimerization. Extracellular complementation experiments revealed that CabA can assemble a functional matrix only when exopolysaccharides coexist. Consequently, the combined results suggested that CabA is a structural protein of the extracellular matrix and multimerizes to a conformation functional in building robust biofilms, which may render V. vulnificus to survive in hostile environments and reach a concentrated infective dose. PMID:26406498

  12. Indole-positive Vibrio vulnificus isolated from disease outbreaks on a Danish eel farm

    DEFF Research Database (Denmark)

    Dalsgaard, Inger; Høi, L.; Siebeling, R.J.

    1999-01-01

    Vibrio vulnificus was isolated in 1996 from 2 disease outbreaks on a Danish eel farm which used brackish water. A characteristic clinical sign was extensive, deep muscle necrosis in the head region. V. vulnificus was isolated from kidney, mucus, spleen, gill and intestine of diseased eels. Thirty...

  13. Vibrio vulnificus outbreaks in Dutch eel farms since 1996: strain diversity and impact.

    NARCIS (Netherlands)

    Haenen, O.L.M.; Zanten, van E.; Jansen, R.; Roozenburg, I.; Engelsma, M.Y.; Dijkstra, A.; Boers, S.A.; Voorbergen-Laarman, M.; Möller, A.V.M.

    2014-01-01

    Vibrio vulnificus is a potentially zoonotic bacterial pathogen of fish, which can infect humans (causing necrotic fasciitis). We analysed 24 V. vulnificus isolates (from 23 severe eel disease outbreaks in 8 Dutch eel farms during 1996 to 2009, and 1 clinical strain from an eel farmer) for genetic

  14. MARTX Toxin in the Zoonotic Serovar of Vibrio vulnificus Triggers an Early Cytokine Storm in Mice

    Directory of Open Access Journals (Sweden)

    Celia Murciano

    2017-07-01

    Full Text Available Vibrio vulnificus biotype 2-serovar E is a zoonotic clonal complex that can cause death by sepsis in humans and fish. Unlike other biotypes, Bt2 produces a unique type of MARTXVv (Multifunctional-Autoprocessive-Repeats-in-Toxin; RtxA13, which is encoded by a gene duplicated in the pVvBt2 plasmid and chromosome II. In this work, we analyzed the activity of this toxin and its role in human sepsis by performing in vitro, ex vivo, and in vivo assays. First, we demonstrated that the ACD domain, present exclusively in this toxin variant, effectively has an actin-cross-linking activity. Second, we determined that the whole toxin caused death of human endotheliocytes and monocytes by lysis and apoptosis, respectively. Finally, we tested the hypothesis that RtxA13 contributes to human death caused by this zoonotic serovar by triggering an early cytokine storm in blood. To this end, we used a Bt2-SerE strain (R99 together with its rtxA13 deficient mutant, and a Bt1 strain (YJ016 producing RtxA11 (the most studied MARTXVv together with its rtxA11 deficient mutant, as controls. Our results showed that RtxA13 was essential for virulence, as R99ΔΔrtxA13 was completely avirulent in our murine model of infection, and that R99, but not strain YJ016, induced an early, strong and dysregulated immune response involving the up-regulation of a high number of genes. This dysregulated immune response was directly linked to RtxA13. Based on these results and those obtained ex vivo (human blood, we propose a model of infection for the zoonotic serovar of V. vulnificus, in which RtxA13 would act as a sepsis-inducing toxin.

  15. Synthetic quorum sensing in model microcapsule colonies

    Science.gov (United States)

    Shum, Henry; Balazs, Anna C.

    2017-08-01

    Biological quorum sensing refers to the ability of cells to gauge their population density and collectively initiate a new behavior once a critical density is reached. Designing synthetic materials systems that exhibit quorum sensing-like behavior could enable the fabrication of devices with both self-recognition and self-regulating functionality. Herein, we develop models for a colony of synthetic microcapsules that communicate by producing and releasing signaling molecules. Production of the chemicals is regulated by a biomimetic negative feedback loop, the “repressilator” network. Through theory and simulation, we show that the chemical behavior of such capsules is sensitive to both the density and number of capsules in the colony. For example, decreasing the spacing between a fixed number of capsules can trigger a transition in chemical activity from the steady, repressed state to large-amplitude oscillations in chemical production. Alternatively, for a fixed density, an increase in the number of capsules in the colony can also promote a transition into the oscillatory state. This configuration-dependent behavior of the capsule colony exemplifies quorum-sensing behavior. Using our theoretical model, we predict the transitions from the steady state to oscillatory behavior as a function of the colony size and capsule density.

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

    Science.gov (United States)

    2011-01-01

    Background Biofilms are microbial communities encased in a layer of extracellular polymeric substances (EPS). The EPS matrix provides several functional purposes for the biofilm, such as protecting bacteria from environmental stresses, and providing mechanical stability. Quorum sensing is a cell-cell communication mechanism used by several bacterial taxa to coordinate gene expression and behaviour in groups, based on population densities. Model We mathematically model quorum sensing and EPS production in a growing biofilm under various environmental conditions, to study how a developing biofilm impacts quorum sensing, and conversely, how a biofilm is affected by quorum sensing-regulated EPS production. We investigate circumstances when using quorum-sensing regulated EPS production is a beneficial strategy for biofilm cells. Results We find that biofilms that use quorum sensing to induce increased EPS production do not obtain the high cell populations of low-EPS producers, but can rapidly increase their volume to parallel high-EPS producers. Quorum sensing-induced EPS production allows a biofilm to switch behaviours, from a colonization mode (with an optimized growth rate), to a protection mode. Conclusions A biofilm will benefit from using quorum sensing-induced EPS production if bacteria cells have the objective of acquiring a thick, protective layer of EPS, or if they wish to clog their environment with biomass as a means of securing nutrient supply and outcompeting other colonies in the channel, of their own or a different species. PMID:21477365

  17. Quorum Sensing in the Squid-Vibrio Symbiosis

    Directory of Open Access Journals (Sweden)

    Tim Miyashiro

    2013-08-01

    Full Text Available Quorum sensing is an intercellular form of communication that bacteria use to coordinate group behaviors such as biofilm formation and the production of antibiotics and virulence factors. The term quorum sensing was originally coined to describe the mechanism underlying the onset of luminescence production in cultures of the marine bacterium Vibrio fischeri. Luminescence and, more generally, quorum sensing are important for V. fischeri to form a mutualistic symbiosis with the Hawaiian bobtail squid, Euprymna scolopes. The symbiosis is established when V. fischeri cells migrate via flagella-based motility from the surrounding seawater into a specialized structure injuvenile squid called the light organ. The cells grow to high cell densities within the light organ where the infection persists over the lifetime of the animal. A hallmark of a successful symbiosis is the luminescence produced by V. fischeri that camouflages the squid at night by eliminating its shadow within the water column. While the regulatory networks governing quorum sensing are critical for properly regulating V. fischeri luminescence within the squid light organ, they also regulate luminescence-independent processes during symbiosis. In this review, we discuss the quorum-sensing network of V. fischeri and highlight its impact at various stages during host colonization.

  18. Quorum Sensing in the Squid-Vibrio Symbiosis

    Science.gov (United States)

    Verma, Subhash C.; Miyashiro, Tim

    2013-01-01

    Quorum sensing is an intercellular form of communication that bacteria use to coordinate group behaviors such as biofilm formation and the production of antibiotics and virulence factors. The term quorum sensing was originally coined to describe the mechanism underlying the onset of luminescence production in cultures of the marine bacterium Vibrio fischeri. Luminescence and, more generally, quorum sensing are important for V. fischeri to form a mutualistic symbiosis with the Hawaiian bobtail squid, Euprymna scolopes. The symbiosis is established when V. fischeri cells migrate via flagella-based motility from the surrounding seawater into a specialized structure injuvenile squid called the light organ. The cells grow to high cell densities within the light organ where the infection persists over the lifetime of the animal. A hallmark of a successful symbiosis is the luminescence produced by V. fischeri that camouflages the squid at night by eliminating its shadow within the water column. While the regulatory networks governing quorum sensing are critical for properly regulating V. fischeri luminescence within the squid light organ, they also regulate luminescence-independent processes during symbiosis. In this review, we discuss the quorum-sensing network of V. fischeri and highlight its impact at various stages during host colonization. PMID:23965960

  19. Quorum sensing in the squid-Vibrio symbiosis.

    Science.gov (United States)

    Verma, Subhash C; Miyashiro, Tim

    2013-08-07

    Quorum sensing is an intercellular form of communication that bacteria use to coordinate group behaviors such as biofilm formation and the production of antibiotics and virulence factors. The term quorum sensing was originally coined to describe the mechanism underlying the onset of luminescence production in cultures of the marine bacterium Vibrio fischeri. Luminescence and, more generally, quorum sensing are important for V. fischeri to form a mutualistic symbiosis with the Hawaiian bobtail squid, Euprymna scolopes. The symbiosis is established when V. fischeri cells migrate via flagella-based motility from the surrounding seawater into a specialized structure injuvenile squid called the light organ. The cells grow to high cell densities within the light organ where the infection persists over the lifetime of the animal. A hallmark of a successful symbiosis is the luminescence produced by V. fischeri that camouflages the squid at night by eliminating its shadow within the water column. While the regulatory networks governing quorum sensing are critical for properly regulating V. fischeri luminescence within the squid light organ, they also regulate luminescence-independent processes during symbiosis. In this review, we discuss the quorum-sensing network of V. fischeri and highlight its impact at various stages during host colonization.

  20. Septic arthritis and subsequent fatal septic shock caused by Vibrio vulnificus infection

    DEFF Research Database (Denmark)

    Emamifar, Amir; Asmussen Andreasen, Rikke; Andersen, Nanna Skaarup

    2015-01-01

    Vibrio vulnificus is a rare but potential fatal bacterium that can cause severe infections. Wound infections, primary sepsis and gastroenteritis are the most common clinical features. Septic arthritis caused by V. vulnificus is an atypical presentation that has been reported in only two case...... reports; however, it has not been previously noted in Denmark. The authors report a case of septic arthritis caused by V. vulnificus in an immunocompromised patient. The disease progressed to severe sepsis and subsequent death within 10 h of admission....

  1. Quorum Sensing Activity in Pandoraea pnomenusa RB38

    Directory of Open Access Journals (Sweden)

    Robson Ee

    2014-06-01

    Full Text Available Strain RB38 was recovered from a former dumping area in Malaysia. MALDI-TOF mass spectrometry and genomic analysis identified strain RB-38 as Pandoraea pnomenusa. Various biosensors confirmed its quorum sensing properties. High resolution triple quadrupole liquid chromatography–mass spectrometry analysis was subsequently used to characterize the N-acyl homoserine lactone production profile of P. pnomenusa strain RB38, which validated that this isolate produced N-octanoyl homoserine lactone as a quorum sensing molecule. This is the first report of the production of N-octanoyl homoserine lactone by P. pnomenusa strain RB38.

  2. Fremmedlegemeinfektioner--nyt om biofilm og quorum sensing

    DEFF Research Database (Denmark)

    Høiby, Niels; Johansen, Helle Krogh; Ciofu, Oana

    2007-01-01

    Biofilms are structured consortia of bacteria embedded in self-produced polymer matrix. Biofilms are resistant to antibiotics, disinfectives and phagocytosis. The persistence of foreign body infections is due to biofilms. Chronic P. aeruginosa lung infection in cystic fibrosis patients is a biofilm....... Bacteria in biofilms communicate by means of quorum sensing which activates genes for virulence factors. Biofilms can be prevented by antibiotic prophylaxis or early therapy or by quorum sensing inhibitors which make them susceptible to antibiotics and phagocytosis. Udgivelsesdato: 2007-Nov-26...

  3. Fremmedlegemeinfektioner--nyt om biofilm og quorum sensing

    DEFF Research Database (Denmark)

    Høiby, Niels; Johansen, Helle Krogh; Ciofu, Oana

    2007-01-01

    . Bacteria in biofilms communicate by means of quorum sensing which activates genes for virulence factors. Biofilms can be prevented by antibiotic prophylaxis or early therapy or by quorum sensing inhibitors which make them susceptible to antibiotics and phagocytosis. Udgivelsesdato: 2007-Nov-26......Biofilms are structured consortia of bacteria embedded in self-produced polymer matrix. Biofilms are resistant to antibiotics, disinfectives and phagocytosis. The persistence of foreign body infections is due to biofilms. Chronic P. aeruginosa lung infection in cystic fibrosis patients is a biofilm...

  4. Computational modeling of the quorum-sensing network in bacteria

    Science.gov (United States)

    Fenley, Andrew; Banik, Suman; Kulkarni, Rahul

    2007-03-01

    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.

  5. The Fish Pathogen Vibrio vulnificus Biotype 2: Epidemiology, Phylogeny, and Virulence Factors Involved in Warm-Water Vibriosis.

    Science.gov (United States)

    Amaro, Carmen; Sanjuán, Eva; Fouz, Belén; Pajuelo, David; Lee, Chung-Te; Hor, Lien-I; Barrera, Rodolfo

    2015-06-01

    Vibrio vulnificus biotype 2 is the etiological agent of warm-water vibriosis, a disease that affects eels and other teleosts, especially in fish farms. Biotype 2 is polyphyletic and probably emerged from aquatic bacteria by acquisition of a transferable virulence plasmid that encodes resistance to innate immunity of eels and other teleosts. Interestingly, biotype 2 comprises a zoonotic clonal complex designated as serovar E that has extended worldwide. One of the most interesting virulence factors produced by serovar E is RtxA13, a multifunctional protein that acts as a lethal factor for fish, an invasion factor for mice, and a survival factor outside the host. Two practically identical copies of rtxA13 are present in all biotype 2 strains regardless of the serovar, one in the virulence plasmid and the other in chromosome II. The plasmid also contains other genes involved in survival and growth in eel blood: vep07, a gene for an outer membrane (OM) lipoprotein involved in resistance to eel serum and vep20, a gene for an OM receptor specific for eel-transferrin and, probably, other related fish transferrins. All the three genes are highly conserved within biotype 2, which suggests that they are under a strong selective pressure. Interestingly, the three genes are related with transferable plasmids, which emphasizes the role of horizontal gene transfer in the evolution of V. vulnificus in nutrient-enriched aquatic environments, such as fish farms.

  6. MR imaging findings of lower extremity sepsis caused by vibro vulnificus: A report of three cases

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jihyun; Koh, Sung Hye; Min, Soo Kee; Lee, Jeong A; Lee, Kwan Seop [Hallym University College of Medicine, Hallym University Sacred Heart Hospital, Anyang (Korea, Republic of)

    2017-01-15

    Lower extremity infection caused by Vibrio vulnificus sepsis is a rapidly progressing fatal condition. Prompt diagnosis followed by early and aggressive treatment with antibiotics and fasciotomy is crucial. In this report, we described lower extremity magnetic resonance (MR) images of three patients with Vibrio vulnificus sepsis. In our cases, MR imaging of lower extremity with Vibrio vulnificus sepsis showed three common findings. First, the MR signal abnormalities appeared simultaneously in all layers, including skin, subcutaneous fat, muscles, and deep fasciae. Second, the inflammation showed symmetry on both legs. Third, none of our cases was accompanied by abscess formation. These imaging features may represent rapid progression of Vibrio vulnificus sepsis and could be helpful for accurate diagnosis, and prompt and aggressive treatment.

  7. Ambroxol interferes with Pseudomonas aeruginosa quorum sensing.

    Science.gov (United States)

    Lu, Qi; Yu, Jialin; Yang, Xiqiang; Wang, Jiarong; Wang, Lijia; Lin, Yayin; Lin, Lihua

    2010-09-01

    The mucolytic agent ambroxol has been reported to interfere with the formation of Pseudomonas aeruginosa-derived biofilms in addition to reducing alginate production by undefined mechanisms. Since quorum sensing is a key regulator of virulence and biofilm formation, we examined the effects of ambroxol on P. aeruginosa PAO1 wild-type bacterial clearance rates, adhesion profiles and biofilm formation compared with the quorum sensing-deficient, double-mutant strains DeltalasR DeltarhlR and DeltalasI DeltarhlI. Data presented in this report demonstrated that ambroxol treatment reduced survival rates of the double-mutant strains compared with the wild-type strain in a dose-dependent manner even though the double-mutants had increased adhesion in the presence of ambroxol compared with the wild-type strain. The PAO1 wild-type strain produced a significantly thicker biofilm (21.64+/-0.57 microm) compared with the biofilms produced by the DeltalasR DeltarhlR (7.36+/-0.2 microm) and DeltalasI DeltarhlI (6.62+/-0.31 microm) isolates. Ambroxol treatment reduced biofilm thickness, increased areal porosity, and decreased the average diffusion distance and textual entropy of wild-type and double-mutant strains. However, compared with the double-mutant strains, the changes observed for the wild-type strain were more clearly defined. Finally, ambroxol exhibited significant antagonistic quorum-sensing properties, suggesting that it could be adapted for use clinically in the treatment of cystic fibrosis and to reduce biofilm formation and in the colonisation of indwelling devices. Copyright (c) 2010 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved.

  8. Characterization of the Hemorrhagic Reaction Caused by Vibrio vulnificus Metalloprotease, a Member of the Thermolysin Family

    OpenAIRE

    Miyoshi, Shin-ichi; Nakazawa, Hiromi; Kawata, Koji; Tomochika, Ken-ichi; Tobe, Kazuo; Shinoda, Sumio

    1998-01-01

    Vibrio vulnificus is an opportunistic human pathogen causing wound infections and septicemia, characterized by hemorrhagic and edematous damage to the skin. This human pathogen secretes a metalloprotease (V. vulnificus protease [VVP]) as an important virulence determinant. When several bacterial metalloproteases including VVP were injected intradermally into dorsal skin, VVP showed the greatest hemorrhagic activity. The level of the in vivo hemorrhagic activity of the bacterial metalloproteas...

  9. Use of a marker plasmid to examine differential rates of growth and death between clinical and environmental strains of Vibrio vulnificus in experimentally infected mice.

    Science.gov (United States)

    Starks, Angela M; Bourdage, Keri L; Thiaville, Patrick C; Gulig, Paul A

    2006-07-01

    Vibrio vulnificus is Gram-negative bacterium that contaminates oysters, causing highly lethal sepsis after consumption of raw oysters and wound infection. We previously described two sets of V. vulnificus strains with different levels of virulence in subcutaneously inoculated iron dextran-treated mice. Both virulent, clinical strains and attenuated, environmental strains could be recovered in high numbers from skin lesions and livers; however, the attenuated environmental strains required significantly higher numbers of colony-forming units (cfu) in the inoculum to produce lethal infection. Using some of these strains and an additional clinical strain, we presently asked if the different abilities to cause infection between the clinical and environmental strains were due to differences in rates of growth or death of the bacteria in the mouse host. We therefore constructed a marker plasmid, pGTR902, that functions as a replicon only in the presence of arabinose, which is not present in significant levels in animal tissues. V. vulnificus strains containing pGTR902 were inoculated into iron dextran-treated and untreated mice. Measuring the proportion of bacteria that had maintained the marker plasmid recovered from mice enabled us to monitor the number of in vivo divisions, hence growth rate; whereas measuring the number of marker plasmid-containing bacteria recovered enabled the measurement of death of the vibrios in the mice. The numbers of bacterial divisions in vivo for all of the strains over a 12-15 h infection period were not significantly different in iron dextran-treated mice; however, the rate of death of one environmental strain was significantly higher compared with the clinical strains. Infection of non-iron dextran-treated mice with clinical strains demonstrated that the greatest effect of iron dextran-treatment was increased growth rate, while one clinical strain also experienced increased death in untreated mice. V. vulnificus inoculated into iron

  10. Identification of Quorum Quenching Bacteria and Its Biocontrol Potential Against Soft Rot Disease Bacteria, Dickeya Dadantii

    OpenAIRE

    Khoiri, Syaiful; DAMAYANTI, TRI ASMIRA; Giyanto, Giyanto

    2017-01-01

    Dickeya dadantii is one of newly found bacteria causing soft rot on orchids in Indonesia. Infected plants showed severe rot rapidly only in few days. An effort to control the bacteria was conducted by utilizing selected quorum quenching (QQ) inducer bacteria which produce AHL-lactonase by aiiA gene. The aims of this research were to screen and identify of quorum quenching bacteria, and also assayed their biocontrol potential ability against D. dadantii in laboratory. The screening of QQ bacte...

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

    OpenAIRE

    Zaki, Ahmed; Shaaban, Mona; HASHISH, Nadia; Amer, Mohamed; Lahloub, Mohamed-Farid

    2012-01-01

    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; nam...

  12. RETRACTED ARTICLE: Quorum-sensing of bacteria and its application

    Science.gov (United States)

    Jiang, Guoliang; Su, Mingxia

    2009-12-01

    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.

  13. Vibrio vulnificus infection in Southern Brazil - Case report Infecção por Vibrio vulnificus no sul do Brasil - Relato de caso

    Directory of Open Access Journals (Sweden)

    João César Beenke França

    2013-06-01

    Full Text Available The genus Vibrio is a member of the family Vibrionaceae, and among their disease-causing species, Vibrio vulnificus, a lactose-positive gram-negative bacillus, is one of the most virulent pathogen of the noncholerae vibrios. We describe the case of a 39-year-old male patient, who was using immunosuppressive therapy, admitted to the hospital for liver transplantation. Twelve hours later, the patient presented high fever, myalgia, anuria and erythematous plaques on lower limbs, of rapid growth and proximal progression. The patient was treated with ceftriaxone, meropenem and oxacillin, however he expired within 30 hours. Blood cultures showed growth of a gram-negative bacillus, which was later identified as Vibrio vulnificus.O gênero Vibrio é membro da família Vibrionaceae, e entre as espécies patogênicas, Vibrio vulnificus, bacilo gram negativo lactose positivo, tem sido frequentemente citado. Descrevemos o caso de um paciente masculino de 39 anos, em uso de medicação imunossupressora, admitido no hospital para transplante hepático. Doze horas após a internação, o paciente evoluiu com febre, mialgias, anúria e placas eritematosas em membros inferiores, com rápido crescimento e evolução proximal. O paciente foi tratado com ceftriaxona, meropenem e oxacilina sem melhora, evoluindo para óbito em 30 horas. Hemocultura mostrou crescimento de bacilo gram negativo posteriormente identificado como Vibrio vulnificus.

  14. Comparison of a commercial biochemical kit and an oligonucleotide probe for identification of environmental isolates of Vibrio vulnificus

    DEFF Research Database (Denmark)

    Dalsgaard, A.; Dalsgaard, Inger; Høi, L.

    1996-01-01

    Methods for the identification and isolation of environmental isolates of Vibrio vulnificus were evaluated. Alkaline peptone water supplemented with polymyxin B and colistin-polymyxin B- cellobiose agar were employed for the isolation of suspected V. vulnificus from water, sediment and shellfish...

  15. Autocrine Signaling and Quorum Sensing: Extreme Ends of a Common Spectrum.

    Science.gov (United States)

    Doğaner, Berkalp A; Yan, Lawrence K Q; Youk, Hyun

    2016-04-01

    'Secrete-and-sense cells' can communicate by secreting a signaling molecule while also producing a receptor that detects the molecule. The cell can potentially 'talk' to itself ('self-communication') or talk to neighboring cells with the same receptor ('neighbor communication'). The predominant forms of secrete-and-sense cells are self-communicating 'autocrine cells', which are largely found in animals, and neighbor-communicating 'quorum sensing cells', which are mostly associated with bacteria. While assumed to function independently of one another, recent studies have discovered quorum-sensing organs and autocrine-signaling microbes. Moreover, similar types of genetic circuit control many autocrine and quorum-sensing cells. Here, we outline these recent findings and explain how autocrine and quorum sensing are two sides of a many-sided 'dice' created by the versatile secrete-and-sense cell. Copyright © 2015 Elsevier Ltd. All rights reserved.

  16. Prevalence of Vibrio vulnificus and Vibrio parahaemolyticus in the Maryland Coastal Bays

    Science.gov (United States)

    De Pascuale, V. O.

    2016-02-01

    The bacterial family of Vibrionaceae is indigenous in the marine estuarine environments such as the Maryland Coastal Bays. Vibrio vulnificus and Vibrio parahaemolyticus are both pathogenic bacteria. Understanding the distribution of Vibrio species is crucial because of the health concerns associated with the bacteria. The aim of this study was to evaluate the overall abundance of bacteria with a focus on Vibrio species in the Maryland Coastal Bays. Seawater samples were collected from 10 different sites that differ with regard to water quality. The total bacteria count (TBC) was determined by two methods: Total plate count and Epifluorescence microscopy. The most-probable-number (MPN) methodology was used to estimate the population of Vibrio parahaemolyticus and Vibrio vulnificus. In addition to the bacteriological analysis, the environmental parameters of temperature and salinity were measured using YSI 6600 multiparameter meter. The average total bacteria count was 2.21 log CFU ml-1. Vibrio vulnificus comprised 5% of the total bacteria count while Vibrio parahaemolyticus comprised only 2% of the total bacteria count. Vibrio vulnificus ranged from 0.30 to 2.48 log MPN ml-1 at the sites tested. Lower Vibrio parahaemolyticus count was observed at the sites with a range of 0.30 to 1.97 log MPN ml-1. There was no significant correlation between the environmental parameters and the Vibrio spp. Since both Vibrio vulnificus and Vibrio parahaemolyticus peak in the summer, there is a potential for a risk of wound infections and gastrointestinal illness based on this data.

  17. QuorUM: An Error Corrector for Illumina Reads.

    Directory of Open Access Journals (Sweden)

    Guillaume Marçais

    Full Text Available Illumina Sequencing data can provide high coverage of a genome by relatively short (most often 100 bp to 150 bp reads at a low cost. Even with low (advertised 1% error rate, 100 × coverage Illumina data on average has an error in some read at every base in the genome. These errors make handling the data more complicated because they result in a large number of low-count erroneous k-mers in the reads. However, there is enough information in the reads to correct most of the sequencing errors, thus making subsequent use of the data (e.g. for mapping or assembly easier. Here we use the term "error correction" to denote the reduction in errors due to both changes in individual bases and trimming of unusable sequence. We developed an error correction software called QuorUM. QuorUM is mainly aimed at error correcting Illumina reads for subsequent assembly. It is designed around the novel idea of minimizing the number of distinct erroneous k-mers in the output reads and preserving the most true k-mers, and we introduce a composite statistic π that measures how successful we are at achieving this dual goal. We evaluate the performance of QuorUM by correcting actual Illumina reads from genomes for which a reference assembly is available.We produce trimmed and error-corrected reads that result in assemblies with longer contigs and fewer errors. We compared QuorUM against several published error correctors and found that it is the best performer in most metrics we use. QuorUM is efficiently implemented making use of current multi-core computing architectures and it is suitable for large data sets (1 billion bases checked and corrected per day per core. We also demonstrate that a third-party assembler (SOAPdenovo benefits significantly from using QuorUM error-corrected reads. QuorUM error corrected reads result in a factor of 1.1 to 4 improvement in N50 contig size compared to using the original reads with SOAPdenovo for the data sets investigated

  18. Fremmedlegemeinfektioner--nyt om biofilm og quorum sensing

    DEFF Research Database (Denmark)

    Høiby, Niels; Johansen, Helle Krogh; Ciofu, Oana

    2007-01-01

    Biofilms are structured consortia of bacteria embedded in self-produced polymer matrix. Biofilms are resistant to antibiotics, disinfectives and phagocytosis. The persistence of foreign body infections is due to biofilms. Chronic P. aeruginosa lung infection in cystic fibrosis patients is a biofi....... Bacteria in biofilms communicate by means of quorum sensing which activates genes for virulence factors. Biofilms can be prevented by antibiotic prophylaxis or early therapy or by quorum sensing inhibitors which make them susceptible to antibiotics and phagocytosis.......Biofilms are structured consortia of bacteria embedded in self-produced polymer matrix. Biofilms are resistant to antibiotics, disinfectives and phagocytosis. The persistence of foreign body infections is due to biofilms. Chronic P. aeruginosa lung infection in cystic fibrosis patients is a biofilm...

  19. Improved isolation of Vibro vulnificus from seawater and sediment with cellobiose-colistin agar

    DEFF Research Database (Denmark)

    Høi, L.; Dalsgaard, Inger; Dalsgaard, A.

    1998-01-01

    An improved selective medium, cellobiose-colistin (CC) agar, gave a significantly higher (P agar, In a total of 446 alkaline peptone water preenrichments amended...... with polymyxin B, V. vulnificus was isolated from 154 preenrichments (35%) with mCPC agar and from 179 preenrichments (40%) with CC agar. CC agar gave a higher plating efficiency of V. vulnificus cells than did cellobiose-polymyxin B-colistin (CPC) agar, mCPC agar, or thiosulfate-citrate-bile salts-sucrose (TCBS......) agar; the only significant difference was observed with TCBS agar, which gave much lower plating efficiencies than the other selective media. Determination of MICs demonstrated that the concentrations of colistin and polymyxin B in CPC agar inhibit growth of a proportion of V. vulnificus strains....

  20. Morphological characterization and biocontrol effects of Vibrio vulnificus phages against Vibriosis in the shrimp aquaculture environment.

    Science.gov (United States)

    Srinivasan, Pappu; Ramasamy, Palaniappan

    2017-10-01

    The re-emerging field of phage therapy is the potential biocontrol agents for the transfer of virulence factor and to kill their bacterial hosts. In this study, the lytic Vibrio vulnificus phages were studied to provide a better understanding of phage-host interactions and development of phage therapy. Four new V. vulnificus phages were detected from shrimp aquaculture system, named VV1, VV2, VV3 and VV4. All lytic V. vulnificus phages are the Tectiviruses of the family Tectiviridae with typical double layered elongated icosahedral head and tailless morphology. Lytic V. vulnificus phages which infect other Vibrio isolates were further characterized by long term storage, enzymes treatment, organic solvents treatment, detergents treatment, pH stability, temperature stability, agar bioassay method and one-step growth experiment. The effects of chloroform, acetone, ethyl alcohol, methyl alcohol, ribonuclease (RNase), trypsin, protease, Triton-X100 treatments were not affected the growth of VV1, VV2, VV3 and VV4 phages. These phages (VV1-VV4) were inactivated completely with temperature (over 60 °C), pH (12), lysozyme and sodium dodecyl sulfate (SDS) treatment. One-step growth experiments indicated that the latent period was at 3 h and burst size was at 37 °C. Agar bioassay method indicated that the percentage of inhibition was 75% (VV1) and 70% (VV2, VV3 & VV4), respectively. SDS-PAGE analysis of all V. vulnificus phages had similar protein patterns with molecular weight masses of 260, 249, 204, 148, 63, 59, 22 and 15 kDa. Hence, it could be concluded that V. vulnificus phage had a broad lytic spectrum and potential biocontrol of luminous Vibriosis in the shrimp aquaculture system. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. Prevalence and population structure of Vibrio vulnificus on fishes from the northern Gulf of Mexico.

    Science.gov (United States)

    Tao, Zhen; Larsen, Andrea M; Bullard, Stephen A; Wright, Anita C; Arias, Covadonga R

    2012-11-01

    The prevalence of Vibrio vulnificus on the external surfaces of fish from the northern Gulf of Mexico was determined in this study. A collection of 242 fish comprising 28 species was analyzed during the course of 12 sampling trips over a 16-month period. The prevalence of V. vulnificus was 37% but increased up to 69% in summer. A positive correlation was found between the percentages of V. vulnificus-positive fish and water temperatures, while salinity and V. vulnificus-positive fish prevalence were inversely correlated. A general lineal model (percent V. vulnificus-positive fish = 0.5930 - 0.02818 × salinity + 0.01406 × water temperature) was applied to best fit the data. Analysis of the population structure was carried out using 244 isolates recovered from fish. Ascription to 16S rRNA gene types indicated that 157 isolates were type A (62%), 72 (29%) were type B, and 22 (9%) were type AB. The percentage of type B isolates, considered to have greater virulence potential, was higher than that previously reported in oyster samples from the northern Gulf of Mexico. Amplified fragment length polymorphism (AFLP) was used to resolve the genetic diversity within the species. One hundred twenty-one unique AFLP profiles were found among all analyzed isolates, resulting in a calculated Simpson's index of diversity of 0.991. AFLP profiles were not grouped on the basis of collection date, fish species, temperature, or salinity, but isolates were clustered into two main groups that correlated precisely with 16S rRNA gene type. The population of V. vulnificus associated with fishes from the northern Gulf of Mexico is heterogeneous and includes strains of great virulence potential.

  2. Evolution of resistance to quorum sensing inhibitors

    Science.gov (United States)

    Kalia, Vipin C.; Wood, Thomas K.; Kumar, Prasun

    2013-01-01

    The major cause of mortality and morbidity in human beings is bacterial infection. Bacteria have developed resistance to most of the antibiotics primarily due to large scale and “indiscriminate” usage. The need is to develop novel mechanisms to treat bacterial infections. The expression of pathogenicity during bacterial infections is mediated by a cell density dependent phenomenon known as quorum sensing (QS). A wide array of QS systems (QSS) is operative in expressing the virulent behavior of bacterial pathogens. Each QSS may be mediated largely by a few major signals along with others produced in minuscule quantities. Efforts to target signal molecules and their receptors have proved effective in alleviating the virulent behavior of such pathogenic bacteria. These QS inhibitors (QSIs) have been reported to be effective in influencing the pathogenicity without affecting bacterial growth. However, evidence is accumulating that bacteria may develop resistance to QSIs. The big question is whether QSIs will meet the same fate as antibiotics? PMID:24194099

  3. Heterogeneity among isolates of Vibrio vulnificus recovered from eels ( Anguilla anguilla ) in Denmark

    DEFF Research Database (Denmark)

    Høi, L.; Dalsgaard, Inger; DePaola, A.

    1998-01-01

    are genetically heterogenous as shown by ribotyping, Ribotyping also showed that the same isolates map persist in an eel farm and cause recurrent outbreaks, Phage typing did not correlate with ribotyping or serotyping. However, we observed that 26 of 28 isolates, which mere not susceptible to any of the phages......The findings of this study demonstrate that Vibrio vulnificus isolates recovered from diseased eels in Denmark are heterogeneous as shown by O serovars, capsule types, ribotyping, phage typing, and plasmid profiling, The study: includes 85 V. vulnificus isolates isolated from the gills, intestinal...

  4. Quorum Quenching of Nitrobacter winogradskyi Suggests that Quorum Sensing Regulates Fluxes of Nitrogen Oxide(s) during Nitrification.

    Science.gov (United States)

    Mellbye, Brett L; Giguere, Andrew T; Bottomley, Peter J; Sayavedra-Soto, Luis A

    2016-10-25

    Quorum sensing (QS) is a widespread process in bacteria used to coordinate gene expression with cell density, diffusion dynamics, and spatial distribution through the production of diffusible chemical signals. To date, most studies on QS have focused on model bacteria that are amenable to genetic manipulation and capable of high growth rates, but many environmentally important bacteria have been overlooked. For example, representatives of proteobacteria that participate in nitrification, the aerobic oxidation of ammonia to nitrate via nitrite, produce QS signals called acyl-homoserine lactones (AHLs). Nitrification emits nitrogen oxide gases (NO, NO2, and N2O), which are potentially hazardous compounds that contribute to global warming. Despite considerable interest in nitrification, the purpose of QS in the physiology/ecology of nitrifying bacteria is poorly understood. Through a quorum quenching approach, we investigated the role of QS in a well-studied AHL-producing nitrite oxidizer, Nitrobacter winogradskyi We added a recombinant AiiA lactonase to N. winogradskyi cultures to degrade AHLs to prevent their accumulation and to induce a QS-negative phenotype and then used mRNA sequencing (mRNA-Seq) to identify putative QS-controlled genes. Our transcriptome analysis showed that expression of nirK and nirK cluster genes (ncgABC) increased up to 19.9-fold under QS-proficient conditions (minus active lactonase). These data led to us to query if QS influenced nitrogen oxide gas fluxes in N. winogradskyi Production and consumption of NOx increased and production of N2O decreased under QS-proficient conditions. Quorum quenching transcriptome approaches have broad potential to identify QS-controlled genes and phenotypes in organisms that are not genetically tractable. Bacterial cell-cell signaling, or quorum sensing (QS), is a method of bacterial communication and gene regulation that is well studied in bacteria. However, little is known about the purpose of QS in many

  5. Production of quorum-sensing signals by bacteria in the coral mucus layer

    Science.gov (United States)

    Li, Jie; Kuang, Weiqi; Long, Lijuan; Zhang, Si

    2017-12-01

    Quorum sensing is an integral part of bacterial communication and interaction, but has not been well characterized in coral mucus microbiota. In this study, of 61 coral mucus isolates, five alphaproteobacteria and one Vibrio species were found to produce N-acyl homoserine lactone (AHL), a quorum-sensing signal in bacteria. Eight gammaproteobacteria isolates were found to produce autoinducer-2 (AI-2) quorum-sensing signals along with two actinobacteria of the genus Rothia. Coral mucus is rich in the antioxidant dimethylsulfoniopropionate (DMSP), the concentration of which has been found to increase under heat stress. Neither AHL nor AI-2 activity was induced by DMSP in those coral mucus isolates that did not initially produce quorum-sensing signals. However, the AI-2 activities of one Rothia isolate (SCSIO 13017) from coral mucus and of Vibrio shilonii (DSM 13774 isolated from a bleached coral) were found to increase in response to 5 μM DMSP but decreased in response to 50 μM DMSP for the first time. These findings suggest that the production of quorum-sensing signals in the coral mucus microbiota may play a role in structuring the surface microbial community as they respond to environmental stress.

  6. Phaeobacter inhibens as biocontrol agent against Vibrio vulnificus in oyster models

    DEFF Research Database (Denmark)

    Porsby, Cisse Hedegaard; Gram, Lone

    2016-01-01

    , the presence of P. inhibens could not prevent subsequently added V. vulnificus from entering the live animals, likely because of too low levels of the biocontrol strain. Whilst the oyster model studies provided indication that P. inhibens DSM 17395 could be a good candidate as biocontrol agent against V...

  7. Vibrio vulnificus Type 6 Secretion System 1 Contains Anti-Bacterial Properties.

    Directory of Open Access Journals (Sweden)

    Selina R Church

    Full Text Available Vibrio vulnificus is a bacterium responsible for severe gastroenteritis, sepsis and wound infections. Gastroenteritis and sepsis are commonly associated with the consumption of raw oysters, whereas wound infection is often associated with the handling of contaminated fish. Although classical virulence factors of this emerging pathogen are well characterised, there remains a paucity of knowledge regarding the general biology of this species. To investigate the presence of previously unreported virulence factors, we applied whole genome sequencing to a panel of ten V. vulnificus strains with varying virulence potentials. This identified two novel type 6 secretion systems (T6SSs, systems that are known to have a role in bacterial virulence and population dynamics. By utilising a range of molecular techniques and assays we have demonstrated the functionality of one of these T6SSs. Furthermore, we have shown that this system is subject to thermoregulation and is negatively regulated by increasing salinity concentrations. This secretion system was also shown to be involved in the killing of V. vulnificus strains that did not possess this system and a model is proposed as to how this interaction may contribute to population dynamics within V. vulnificus strains. In addition to this intra-species killing, this system also contributes to the killing of inter bacterial species and may have a role in the general composition of Vibrio species in the environment.

  8. Insight into the evolution of Vibrio vulnificus biotype 3's genome.

    Science.gov (United States)

    Efimov, Vera; Danin-Poleg, Yael; Raz, Nili; Elgavish, Sharona; Linetsky, Alex; Kashi, Yechezkel

    2013-01-01

    Vibrio vulnificus is an aquatic bacterium and an important human pathogen. Strains of V. vulnificus are biochemically classified into three biotypes. The newly emerged biotype 3 appears to be rather clonal and geographically restricted to Israel, where it caused an outbreak of wound infections and bacteremia. To understand the evolution of the bacterium's genome, we sequenced and analyzed the genome of biotype 3 strain VVyb1(BT3), and then conducted a microbial environmental survey of the hypothesized niche from which it probably evolved. The genome of this environmental isolate revealed higher similarity to the published biotype 1 genomes of clinical strains (90%) than to the environmental strains (87%), supporting the virulence of the biotype 3 group. Moreover, 214 of the total 5361 genes were found to be unique to strain VVyb1(BT3), having no sequence similarity to any of the known genomes of V. vulnificus; 35 of them function in DNA mobility and rearrangement, supporting the role of horizontal gene transfer in genome evolution. Interestingly, 29 of the "unique" genes had homologies among Shewanella species. In a survey conducted in aquaculture ponds in Israel, we successfully co-isolated Shewanella and V. vulnificus from the same niche, further supporting the probable contribution of Shewanella to the genome evolution of biotype 3. Indeed, one gene was found in a S. algae isolate. Surprisingly, molecular analysis revealed that some of the considered unique genes are harbored by non-sequenced biotype 1 strains isolated from the same environment. Finally, analyses of the biotype 3 genome together with the environmental survey suggested that its genome originated from a biotype 1 Israeli strain that acquired a rather small number of genes from other bacterial species in the niche, such as Shewanella. Therefore, aquaculture is likely to play a major role as a man-made ecological niche in bacterial evolution, leading the emergence of new pathogenic groups in V

  9. Comparative genomic analysis of clinical and environmental Vibrio vulnificus isolates revealed biotype 3 evolutionary relationships.

    Science.gov (United States)

    Koton, Yael; Gordon, Michal; Chalifa-Caspi, Vered; Bisharat, Naiel

    2014-01-01

    In 1996 a common-source outbreak of severe soft tissue and bloodstream infections erupted among Israeli fish farmers and fish consumers due to changes in fish marketing policies. The causative pathogen was a new strain of Vibrio vulnificus, named biotype 3, which displayed a unique biochemical and genotypic profile. Initial observations suggested that the pathogen erupted as a result of genetic recombination between two distinct populations. We applied a whole genome shotgun sequencing approach using several V. vulnificus strains from Israel in order to study the pan genome of V. vulnificus and determine the phylogenetic relationship of biotype 3 with existing populations. The core genome of V. vulnificus based on 16 draft and complete genomes consisted of 3068 genes, representing between 59 and 78% of the whole genome of 16 strains. The accessory genome varied in size from 781 to 2044 kbp. Phylogenetic analysis based on whole, core, and accessory genomes displayed similar clustering patterns with two main clusters, clinical (C) and environmental (E), all biotype 3 strains formed a distinct group within the E cluster. Annotation of accessory genomic regions found in biotype 3 strains and absent from the core genome yielded 1732 genes, of which the vast majority encoded hypothetical proteins, phage-related proteins, and mobile element proteins. A total of 1916 proteins (including 713 hypothetical proteins) were present in all human pathogenic strains (both biotype 3 and non-biotype 3) and absent from the environmental strains. Clustering analysis of the non-hypothetical proteins revealed 148 protein clusters shared by all human pathogenic strains; these included transcriptional regulators, arylsulfatases, methyl-accepting chemotaxis proteins, acetyltransferases, GGDEF family proteins, transposases, type IV secretory system (T4SS) proteins, and integrases. Our study showed that V. vulnificus biotype 3 evolved from environmental populations and formed a genetically

  10. Comparative Genomic Analysis of Clinical and Environmental Vibrio Vulnificus Isolates Revealed Biotype 3 Evolutionary Relationships

    Directory of Open Access Journals (Sweden)

    Yael eKotton

    2015-01-01

    Full Text Available In 1996 a common-source outbreak of severe soft tissue and bloodstream infections erupted among Israeli fish farmers and fish consumers due to changes in fish marketing policies. The causative pathogen was a new strain of Vibrio vulnificus, named biotype 3, which displayed a unique biochemical and genotypic profile. Initial observations suggested that the pathogen erupted as a result of genetic recombination between two distinct populations. We applied a whole genome shotgun sequencing approach using several V. vulnificus strains from Israel in order to study the pan genome of V. vulnificus and determine the phylogenetic relationship of biotype 3 with existing populations. The core genome of V. vulnificus based on 16 draft and complete genomes consisted of 3068 genes, representing between 59% and 78% of the whole genome of 16 strains. The accessory genome varied in size from 781 kbp to 2044 kbp. Phylogenetic analysis based on whole, core, and accessory genomes displayed similar clustering patterns with two main clusters, clinical (C and environmental (E, all biotype 3 strains formed a distinct group within the E cluster. Annotation of accessory genomic regions found in biotype 3 strains and absent from the core genome yielded 1732 genes, of which the vast majority encoded hypothetical proteins, phage-related proteins, and mobile element proteins. A total of 1916 proteins (including 713 hypothetical proteins were present in all human pathogenic strains (both biotype 3 and non-biotype 3 and absent from the environmental strains. Clustering analysis of the non-hypothetical proteins revealed 148 protein clusters shared by all human pathogenic strains; these included transcriptional regulators, arylsulfatases, methyl-accepting chemotaxis proteins, acetyltransferases, GGDEF family proteins, transposases, type IV secretory system (T4SS proteins, and integrases. Our study showed that V. vulnificus biotype 3 evolved from environmental populations and

  11. Size of quorum sensing communities

    DEFF Research Database (Denmark)

    Ferkinghoff-Borg, Jesper; Sams, Thomas

    2014-01-01

    Ensembles of bacteria are able to coordinate their phenotypic behavior in accordance with the size, density, and growth state of the ensemble. This is achieved through production and exchange of diffusible signal molecules in a cell–cell regulatory system termed quorum sensing. In the generic...... by a geometric factor which incorporates the boundary conditions constitutes an appropriate size measure. The geometric factor is the square of the radius for a spherical colony or a hemisphere attached to a reflecting surface. If surrounded by a rapidly exchanged medium, the geometric factor is divided by three...

  12. Pathogenesis of Infection by Clinical and Environmental Strains of Vibrio vulnificus in Iron-Dextran-Treated Mice

    OpenAIRE

    Starks, Angela M.; Schoeb, Trenton R.; Tamplin, Mark L.; Parveen, Salina; Doyle, Thomas J.; Bomeisl, Philip E.; Escudero, Gloria M.; Gulig, Paul A.

    2000-01-01

    Vibrio vulnificus is an opportunistic pathogen that contaminates oysters harvested from the Gulf of Mexico. In humans with compromising conditions, especially excess levels of iron in plasma and tissues, consumption of contaminated seafood or exposure of wounds to contaminated water can lead to systemic infection and disfiguring skin infection with extremely high mortality. V. vulnificus-associated diseases are noted for the rapid replication of the bacteria in host tissues, with extensive ti...

  13. Caffeine as a Potential Quorum Sensing Inhibitor

    Directory of Open Access Journals (Sweden)

    Kok-Gan Chan

    2013-04-01

    Full Text Available 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.

  14. Structure And Specificity of a Quorum-Quenching Lactonase (AiiB) From Agrobacterium Tumefaciens

    Energy Technology Data Exchange (ETDEWEB)

    Liu, D.; Thomas, P.W.; Momb, J.; Hoang, Q.Q.; Petsko, G.A.; Ringe, D.; Fast, W.

    2009-06-03

    N-Acyl-l-homoserine lactone (AHL) mediated quorum-sensing regulates virulence factor production in a variety of Gram-negative bacteria. Proteins capable of degrading these autoinducers have been called 'quorum-quenching' enzymes, can block many quorum-sensing dependent phenotypes, and represent potentially useful reagents for clinical, agricultural, and industrial applications. The most characterized quorum-quenching enzymes to date are the AHL lactonases, which are metalloproteins that belong to the metallo-beta-lactamase superfamily. Here, we report the cloning, heterologous expression, purification, metal content, substrate specificity, and three-dimensional structure of AiiB, an AHL lactonase from Agrobacterium tumefaciens. Much like a homologous AHL lactonase from Bacillus thuringiensis, AiiB appears to be a metal-dependent AHL lactonase with broad specificity. A phosphate dianion is bound to the dinuclear zinc site and the active-site structure suggests specific mechanistic roles for an active site tyrosine and aspartate. To our knowledge, this is the second representative structure of an AHL lactonase and the first of an AHL lactonase from a microorganism that also produces AHL autoinducers. This work should help elucidate the hydrolytic ring-opening mechanism of this family of enzymes and also facilitate the design of more effective quorum-quenching catalysts.

  15. Interspecies Quorum Sensing as a Stress-Anticipation Signal in E. coli

    DEFF Research Database (Denmark)

    Høyland-Kroghsbo, Nina Molin

    underlying the quorum sensing regulated defense mechanism, led to the discovery that AHL activates expression of cnu, encoding an Hha-family protein that interacts with the global regulatory protein H-NS, and potentially modifies its functions. Inspired by the discovery that AHL protects E. coli from...... of the general stress response also resulted in an increase in transiently antibiotic tolerant persister cells in E. coli. In conclusion, this thesis provides a key answer to why E. coli listens in on AHL signals it does not itself produce, namely that detection of interspecies AHL quorum sensing by E. coli...... serves to anticipate- and adapt to environmental stresses. This discovery may have important clinical implications, as quorum sensing-inhibitory drugs may, in addition to their primary purpose to decrease virulence of pathogens, additionally weaken bacterial defenses thus making them prone to succumb...

  16. Facultative cheating supports the coexistence of diverse quorum-sensing alleles.

    Science.gov (United States)

    Pollak, Shaul; Omer-Bendori, Shira; Even-Tov, Eran; Lipsman, Valeria; Bareia, Tasneem; Ben-Zion, Ishay; Eldar, Avigdor

    2016-02-23

    Bacterial quorum sensing enables bacteria to cooperate in a density-dependent manner via the group-wide secretion and detection of specific autoinducer molecules. Many bacterial species show high intraspecific diversity of autoinducer-receptor alleles, called pherotypes. The autoinducer produced by one pherotype activates its coencoded receptor, but not the receptor of another pherotype. It is unclear what selection forces drive the maintenance of pherotype diversity. Here, we use the ComQXPA system of Bacillus subtilis as a model system, to show that pherotype diversity can be maintained by facultative cheating--a minority pherotype exploits the majority, but resumes cooperation when its frequency increases. We find that the maintenance of multiple pherotypes by facultative cheating can persist under kin-selection conditions that select against "obligate cheaters" quorum-sensing response null mutants. Our results therefore support a role for facultative cheating and kin selection in the evolution of quorum-sensing diversity.

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

    DEFF Research Database (Denmark)

    Hentzer, Morten; Riedel, K.; Rasmussen, Thomas Bovbjerg

    2002-01-01

    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 lay 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. aeruginosa biofilms. It is reported that a synthetic halogenated furanone compound, which is a derivative of the secondary metabolites produced by the Australian...... macroalga Delisea pulchra, is capable of interfering with AHL-mediated quorum sensing in P. aeruginosa. It is demonstrated that the furanone compound specifically represses expression of a PlasB-gfp reporter fusion without affecting growth or protein synthesis. In addition, it reduces the production...

  18. Quorum sensing mechanisms in fungi

    Directory of Open Access Journals (Sweden)

    Jorge Barriuso

    2015-11-01

    Full Text Available In the environment, cells from microorganisms can communicate to each other through the secretion of signal molecules, so-called autoinducers, which accumulate in the medium as the population density grows. When the concentration of these molecules reaches a threshold, different genes are induced or repressed, and processes such as sporulation, pathogenesis or symbiosis are initiated. These mechanisms, known as quorum sensing (QS, were first discovered in bacteria, and more recently have been identified in fungi. The model eukaryote organism for this kind of studies is the dimorphic pathogenic yeast Candida albicans. However, QS mechanisms have been described in a variety of fungi with clinical or biotechnological interest. Hence, the study of these mechanisms may be useful to prevent fungal infections, and interesting for its exploitation in industrial biotechnology.

  19. How Delisea pulchra furanones affect quorum sensing and swarming motility in Serratia liquefaciens MG1

    DEFF Research Database (Denmark)

    Rasmussen, T B; Manefield, M; Andersen, Jens Bo

    2000-01-01

    Halogenated furanones produced by the benthic marine macroalga Delisea pulchra inhibit swarming motility of Serratia liquefaciens MG1. This study demonstrates that exogenously added furanones control transcription of the quorum sensing regulated gene swrA in competition with the cognate signal mo...

  20. Quorum Quenching Revisited—From Signal Decays to Signalling Confusion

    Directory of Open Access Journals (Sweden)

    Kok-Gan Chan

    2012-04-01

    Full Text Available In a polymicrobial community, while some bacteria are communicating with neighboring cells (quorum sensing, others are interrupting the communication (quorum quenching, thus creating a constant arms race between intercellular communication. In the past decade, numerous quorum quenching enzymes have been found and initially thought to inactivate the signalling molecules. Though this is widely accepted, the actual roles of these quorum quenching enzymes are now being uncovered. Recent evidence extends the role of quorum quenching to detoxification or metabolism of signalling molecules as food and energy source; this includes “signalling confusion”, a term coined in this paper to refer to the phenomenon of non-destructive modification of signalling molecules. While quorum quenching has been explored as a novel anti-infective therapy targeting, quorum sensing evidence begins to show the development of resistance against quorum quenching.

  1. Identification of DNA Sequences Specific for Vibrio vulnificus Biotype 2 Strains by Suppression Subtractive Hybridization

    OpenAIRE

    Lee, Chung-Te; Amaro, Carmen; Sanjuán, Eva; Hor, Lien-I

    2005-01-01

    Vibrio vulnificus can be divided into three biotypes, and only biotype 2, which is further divided into serovars, contains eel-virulent strains. We compared the genomic DNA of a biotype 2 serovar E isolate (tester) with the genomic DNAs of three biotype 1 strains by suppression subtractive hybridization and then tested the distribution of the tester-specific DNA sequences in a wide collection of bacterial strains. In this way we identified three plasmid-borne DNA sequences that were specific ...

  2. Role of iron, capsule, and toxins in the pathogenicity of Vibrio vulnificus biotype 2 for mice.

    OpenAIRE

    Amaro, C; Biosca, E G; Fouz, B; Toranzo, A E; Garay, E

    1994-01-01

    The virulence mechanisms of Vibrio vulnificus biotype 2 have been studied and compared with those of biotype 1 in mice as the experimental animals. Biotype 2 isolates from European eels were as virulent for mice as biotype 1 strains (50% lethal dose, about 10(5) CFU per mouse); a septicemic infection developed in less than 24 h. These strains had several properties in common with biotype 1 organisms including capsule expression, uptake of various iron sources, and production of exoproteins, w...

  3. Transmission to Eels, Portals of Entry, and Putative Reservoirs of Vibrio vulnificus Serovar E (Biotype 2)

    OpenAIRE

    Marco-Noales, Ester; Milán, Miguel; Fouz, Belén; Sanjuán, Eva; Amaro, Carmen

    2001-01-01

    Vibrio vulnificus serovar E (formerly biotype 2) is the etiologic agent that is responsible for the main infectious disease affecting farmed eels. Although the pathogen can theoretically use water as a vehicle for disease transmission, it has not been isolated from tank water during epizootics to date. In this work, the mode of transmission of the disease to healthy eels, the portals of entry of the pathogen into fish, and their putative reservoirs have been investigated by means of laborator...

  4. Modeling and forecasting the distribution of Vibrio vulnificus in Chesapeake Bay

    Energy Technology Data Exchange (ETDEWEB)

    Jacobs, John M.; Rhodes, M.; Brown, C. W.; Hood, Raleigh R.; Leight, A.; Long, Wen; Wood, R.

    2014-11-01

    The aim is to construct statistical models to predict the presence, abundance and potential virulence of Vibrio vulnificus in surface waters. A variety of statistical techniques were used in concert to identify water quality parameters associated with V. vulnificus presence, abundance and virulence markers in the interest of developing strong predictive models for use in regional oceanographic modeling systems. A suite of models are provided to represent the best model fit and alternatives using environmental variables that allow them to be put to immediate use in current ecological forecasting efforts. Conclusions: Environmental parameters such as temperature, salinity and turbidity are capable of accurately predicting abundance and distribution of V. vulnificus in Chesapeake Bay. Forcing these empirical models with output from ocean modeling systems allows for spatially explicit forecasts for up to 48 h in the future. This study uses one of the largest data sets compiled to model Vibrio in an estuary, enhances our understanding of environmental correlates with abundance, distribution and presence of potentially virulent strains and offers a method to forecast these pathogens that may be replicated in other regions.

  5. Modeling and forecasting the distribution of Vibrio vulnificus in Chesapeake Bay.

    Science.gov (United States)

    Jacobs, J M; Rhodes, M; Brown, C W; Hood, R R; Leight, A; Long, W; Wood, R

    2014-11-01

    To construct statistical models to predict the presence, abundance and potential virulence of Vibrio vulnificus in surface waters of Chesapeake Bay for implementation in ecological forecasting systems. We evaluated and applied previously published qPCR assays to water samples (n = 1636) collected from Chesapeake Bay from 2007-2010 in conjunction with State water quality monitoring programmes. A variety of statistical techniques were used in concert to identify water quality parameters associated with V. vulnificus presence, abundance and virulence markers in the interest of developing strong predictive models for use in regional oceanographic modeling systems. A suite of models are provided to represent the best model fit and alternatives using environmental variables that allow them to be put to immediate use in current ecological forecasting efforts. Environmental parameters such as temperature, salinity and turbidity are capable of accurately predicting abundance and distribution of V. vulnificus in Chesapeake Bay. Forcing these empirical models with output from ocean modeling systems allows for spatially explicit forecasts for up to 48 h in the future. This study uses one of the largest data sets compiled to model Vibrio in an estuary, enhances our understanding of environmental correlates with abundance, distribution and presence of potentially virulent strains and offers a method to forecast these pathogens that may be replicated in other regions. This article has been contributed to by US Government employees and their work is in the public domain in the USA.

  6. A case of Vibrio vulnificus infection complicated with fulminant purpura: gene and biotype analysis of the pathogen.

    Science.gov (United States)

    Hori, Masatoshi; Nakayama, Akifumi; Kitagawa, Daisuke; Fukushima, Hidetada; Asai, Hideki; Kawai, Yasuyuki; Okuchi, Kazuo

    2017-05-01

    Introduction.Vibrio vulnificus (V. vulnificus) causes a severe infection that develops in the compromised host. Its pathophysiology is classified into three types: (1) primary septicaemia, (2) gastrointestinal illness pattern and (3) wound infection pattern. Of these, primary septicaemia is critical. V. vulnificus can be classified into three biotypes and two genotypes and its pathogenicity is type-dependent. Case presentation. A 47-year-old man presented to a local hospital with chief complaints of fever, bilateral lower limb pain and diarrhoea. He had no history of foreign travel or known medical problems. He was in septic shock and developed fulminant purpura within 24 h of the onset. High-dose vasopressor and antibiotic administration failed to alter his status and he died 3 days after the onset of symptoms. V. vulnificus was isolated from blood, skin and nasal discharge cultures. Biotype and gene analysis of the microbe isolated identified it as Biotype 3, mainly reported in Israel in wound infections, and Genotype E, implicating an environmental isolate. These typing analyses indicated that the microbe isolated could be classified as a type with low pathogenicity. Conclusion. This case highlighted that Biotype 3 and Genotype E can also cause primary septicaemia. Although the majority of reports on Biotype 3 have been from the Middle East, this experience with the present case provided evidence that the habitat of Biotype 3 V. vulnificus has been extending to East Asia as well.

  7. Virulence Profiles of Vibrio vulnificus in German Coastal Waters, a Comparison of North Sea and Baltic Sea Isolates

    Directory of Open Access Journals (Sweden)

    Nadja Bier

    2015-12-01

    Full Text Available Vibrio vulnificus is a halophilic bacterium of coastal environments known for sporadically causing severe foodborne or wound infections. Global warming is expected to lead to a rising occurrence of V. vulnificus and an increasing incidence of human infections in Northern Europe. So far, infections in Germany were exclusively documented for the Baltic Sea coast, while no cases from the North Sea region have been reported. Regional variations in the prevalence of infections may be influenced by differences in the pathogenicity of V. vulnificus populations in both areas. This study aimed to compare the distribution of virulence-associated traits and genotypes among 101 V. vulnificus isolates from the Baltic Sea and North Sea in order to assess their pathogenicity potential. Furthermore, genetic relationships were examined by multilocus sequence typing (MLST. A high diversity of MLST sequences (74 sequence types and differences regarding the presence of six potential pathogenicity markers were observed in the V. vulnificus populations of both areas. Strains with genotypes and markers associated with pathogenicity are not restricted to a particular geographic region. This indicates that lack of reported cases in the North Sea region is not caused by the absence of potentially pathogenic strains.

  8. Quorum Quenching of Nitrobacter winogradskyi Suggests that Quorum Sensing Regulates Fluxes of Nitrogen Oxide(s during Nitrification

    Directory of Open Access Journals (Sweden)

    Brett L. Mellbye

    2016-10-01

    Full Text Available Quorum sensing (QS is a widespread process in bacteria used to coordinate gene expression with cell density, diffusion dynamics, and spatial distribution through the production of diffusible chemical signals. To date, most studies on QS have focused on model bacteria that are amenable to genetic manipulation and capable of high growth rates, but many environmentally important bacteria have been overlooked. For example, representatives of proteobacteria that participate in nitrification, the aerobic oxidation of ammonia to nitrate via nitrite, produce QS signals called acyl-homoserine lactones (AHLs. Nitrification emits nitrogen oxide gases (NO, NO2, and N2O, which are potentially hazardous compounds that contribute to global warming. Despite considerable interest in nitrification, the purpose of QS in the physiology/ecology of nitrifying bacteria is poorly understood. Through a quorum quenching approach, we investigated the role of QS in a well-studied AHL-producing nitrite oxidizer, Nitrobacter winogradskyi. We added a recombinant AiiA lactonase to N. winogradskyi cultures to degrade AHLs to prevent their accumulation and to induce a QS-negative phenotype and then used mRNA sequencing (mRNA-Seq to identify putative QS-controlled genes. Our transcriptome analysis showed that expression of nirK and nirK cluster genes (ncgABC increased up to 19.9-fold under QS-proficient conditions (minus active lactonase. These data led to us to query if QS influenced nitrogen oxide gas fluxes in N. winogradskyi. Production and consumption of NOx increased and production of N2O decreased under QS-proficient conditions. Quorum quenching transcriptome approaches have broad potential to identify QS-controlled genes and phenotypes in organisms that are not genetically tractable.

  9. Quorum-quenching limits quorum-sensing exploitation by signal-negative invaders

    Science.gov (United States)

    Tannières, Mélanie; Lang, Julien; Barnier, Claudie; Shykoff, Jacqui A.; Faure, Denis

    2017-01-01

    Some bacteria produce and perceive quorum-sensing (QS) signals that coordinate several behaviours, including the costly processes that are exoenzyme production and plasmid transfer. In the case of plasmid transfer, the emergence of QS signal-altered invaders and their policing are poorly documented. In Agrobacterium tumefaciens, the virulence Ti-plasmid encodes both synthesis and sensing of QS-signals, which promote its transfer from a donor to a recipient cell. Here, we reported that QS-altered A. tumefaciens mutants arose during experimental evolution. All showed improved growth compared to their ancestor. Genome sequencing revealed that, though some had lost the Ti-plasmid, most were defective for QS-signal synthesis and Ti-plasmid conjugation (traR mutations) and one exhibited a QS-signal exploitation behaviour, using signal produced by other cells to enhance its own Ti-plasmid transfer. We explored mechanisms that can limit this QS-hijacking. We showed that the A. tumefaciens capacity to inactivate QS-signals by expressing QS-degrading enzyme could attenuate dissemination of the QS signal-negative Ti-plasmids. This work shows that enzymatic QS-disruption whether encoded by the QS-producing Ti-plasmid itself, by a companion plasmid in the same donor cells, or by one in the recipient cells, in all cases can serve as a mechanism for controlling QS exploitation by QS signal-negative mutants.

  10. Quorum Systems With Applications to Storage and Consensus

    CERN Document Server

    Vukolic, Marko

    2012-01-01

    A quorum system is a collection of subsets of nodes, called quorums, with the property that each pair of quorums have a non-empty intersection. Quorum systems are the key mathematical abstraction for ensuring consistency in fault-tolerant and highly available distributed computing. Critical for many applications since the early days of distributed computing, quorum systems have evolved from simple majorities of a set of processes to complex hierarchical collections of sets, tailored for general adversarial structures. The initial non-empty intersection property has been refined many times to a

  11. Targeting quorum sensing in Pseudomonas aeruginosa biofilms

    DEFF Research Database (Denmark)

    Jakobsen, Tim Holm; Bjarnsholt, Thomas; Jensen, Peter Østrup

    2013-01-01

    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...

  12. Identification of Pathways Critical to Quorum Sensing and Virulence Induction

    Energy Technology Data Exchange (ETDEWEB)

    Ognibene, Ted J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Young, N. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Holtz-Morris, A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Daley, P. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2009-02-27

    Quorum sensing is a mode of intercellular communication between bacteria that allows them to collectively regulate behavior such as virulence, sporulation, motility and biofilm formation. It is mediated by bacterially synthesized, diffusible, signaling molecules (autoinducers) that increase in concentration as a bacterial population expands until a critical threshold concentration is reached. However, in most bacterial species that produce autoinducer molecules, the physiologic concentration of these molecules is unknown. Moreover, many bacterial species, including Y. pestis, produce an array of quorum sensing molecules and the physiologic concentration of each individual type of autoinducer molecule is not known. There is a need to accurately and precisely quantitate these molecules, as it may be that different types of autoinducer molecules have different effects on virulence in the bacterium. We focused our efforts on the construction of a platform to identify and quantitate autoinducer molecules using FTICR, 14C isotope labeling and accelerator mass spectrometry (AMS). Specifically, we focused on autoinducer-1 type molecules, acylhomoserine lactone (HSL), derived from S-adenosylmethionine (SAM).

  13. Quorum sensing in gram-negative bacteria

    DEFF Research Database (Denmark)

    Wu, H.; Song, Z.J.; Høiby, N.

    2004-01-01

    Bacteria can communicate with each other by means of signal molecules to coordinate the behavior of the entire community, and the mechanism is referred to as quorum sensing (QS). Signal systems enable bacteria to sense the size of their densities by monitoring the concentration of the signal...... molecules. Among Gram-negative bacteria N-acyl-L-homoserine lactone (acyl-HSL)-dependent quorum sensing systems are particularly widespread. These systems are used to coordinate expression of phenotypes that are fundamental to the interaction of bacteria with each other and with their environment...

  14. RpoN Regulates Virulence Factors of Pseudomonas aeruginosa via Modulating the PqsR Quorum Sensing Regulator

    Directory of Open Access Journals (Sweden)

    Zhao Cai

    2015-11-01

    Full Text Available The alternative sigma factor RpoN regulates many cell functions, such as motility, quorum sensing, and virulence in the opportunistic pathogen Pseudomonas aeruginosa (P. aeruginosa. P. aeruginosa often evolves rpoN-negative variants during the chronic infection in cystic fibrosis patients. It is unclear how RpoN interacts with other regulatory mechanisms to control virulence of P. aeruginosa. In this study, we show that RpoN modulates the function of PqsR, a quorum sensing receptor regulating production of virulence factors including the phenazine pyocyanin. The ∆rpoN mutant is able to synthesize 4-quinolone signal molecule HHQ but unable to activate PqsR and Pseudomonas quinolone signal (pqs quorum sensing. The ∆rpoN mutant produces minimal level of pyocyanin and is unable to produce the anti-staphylococcal agents. Providing pqsR in trans in the ∆rpoN mutant restores its pqs quorum sensing and virulence factor production to the wild-type level. Our study provides evidence that RpoN has a regulatory effect on P. aeruginosa virulence through modulating the function of the PqsR quorum sensing regulator.

  15. The response of Serratia marcescens JG to environmental changes by quorum sensing system.

    Science.gov (United States)

    Sun, Shu-Jing; Liu, Hui-Jun; Weng, Cai-Hong; Lai, Chun-Fen; Ai, Liu-Ying; Liu, Yu-Chen; Zhu, Hu

    2016-08-01

    Many bacterial cells are known to regulate their cooperative behaviors and physiological processes through a molecular mechanism called quorum sensing. Quorum sensing in Serratia marcescens JG is mediated by the synthesis of autoinducer 2 (AI-2) which is a furanosyl borate diester. In this study, the response of quorum sensing in S. marcescens JG to environment changes such as the initial pH, carbon sources and boracic acid was investigated by a bioreporter and real-time PCR analysis. The results show that glucose can affect AI-2 synthesis to the greatest extent, and 2.0 % glucose can stimulate S. marcescens JG to produce more AI-2, with a 3.5-fold increase in activity compared with control culture. Furthermore, the response of quorum sensing to changes in glucose concentration was performed by changing the amount of luxS RNA transcripts. A maximum of luxS transcription appeared during the exponential growth phase when the glucose concentration was 20.0 g/L. AI-2 production was also slightly impacted by the low initial pH. It is significant for us that the addition of boracic acid at microdosage (0.1-0.2 g/L) can also induce AI-2 synthesis, which probably demonstrated the feasible fact that the 4,5-dihydroxy-2, 3-pentanedione cyclizes by the addition of borate and the loss of water, is hydrated and is converted to the final AI-2 in S. marcescens JG.

  16. Probabilistically Bounded Staleness for Practical Partial Quorums

    Science.gov (United States)

    2012-01-03

    Conway, J. M. Hellerstein, and W. R. Marczak. Consistency Analysis in Bloom: a CALM and Collected Approach. In CIDR 2011. [13] M. Armbrust, K. Curtis, T... CIDR 2009. [34] M. Herlihy. Dynamic quorum adjustment for partitioned data. ACM Transactions on Database Systems, 12 (2):170–194, 1987. [35] M

  17. Chitinase determinants of Vibrio vulnificus: gene cloning and applications of a chitinase probe.

    OpenAIRE

    Wortman, A T; Somerville, C C; Colwell, R R

    1986-01-01

    To initiate study of the genetic control of chitinolytic activity in vibrios, the chitobiase gene was isolated by cloning chromosomal DNA prepared from Vibrio vulnificus. Chimeric plasmids were constructed from Sau3A I partial digests of chromosomal DNA by ligating 5 to 15-kilobase fragments into the BamHI site, i.e., in the Tcr gene, of pBR322 (Amr Tcr). The resulting plasmids were transformed into Escherichia coli DH1. Chitobiase activity of the insert-bearing clones was detected by using a...

  18. Is Quorum Signaling by Mycotoxins a New Risk-Mitigating Strategy for Bacterial Biocontrol of Fusarium verticillioides and Other Endophytic Fungal Species?

    Science.gov (United States)

    Bacon, Charles W; Hinton, Dorothy M; Mitchell, Trevor R

    2017-08-23

    Bacterial endophytes are used as biocontrol organisms for plant pathogens such as the maize endophyte Fusarium verticillioides and its production of fumonisin mycotoxins. However, such applications are not always predictable and efficient. In this work, we hypothesize and review work that quorum sensing inhibitors are produced either by fungi or by pathogenic bacteria for competitive purposes, altering the efficiency of the biocontrol organisms. Recently, quorum sensing inhibitors have been isolated from several fungi, including Fusarium species, three of which are mycotoxins. Thus, we further postulate that other mycotoxins are inhibitors or quenching metabolites that prevent the protective abilities and activities of endophytic biocontrol bacteria within intercellular spaces. To test the aforementioned suppositions, we review work detailing the use of bioassay bacteria for several mycotoxins for quorum activity. We specifically focus on the quorum use of endophytic bacteria as biocontrols for mycotoxic fungal endophytes, such as the Fusarium species and the fumonisin mycotoxins.

  19. A New Class of Quorum Quenching Molecules from Staphylococcus Species Affects Communication and Growth of Gram-Negative Bacteria

    Science.gov (United States)

    Chu, Ya-Yun; Nega, Mulugeta; Wölfle, Martina; Plener, Laure; Grond, Stephanie; Jung, Kirsten; Götz, Friedrich

    2013-01-01

    The knowledge that many pathogens rely on cell-to-cell communication mechanisms known as quorum sensing, opens a new disease control strategy: quorum quenching. Here we report on one of the rare examples where Gram-positive bacteria, the ‘Staphylococcus intermedius group’ of zoonotic pathogens, excrete two compounds in millimolar concentrations that suppress the quorum sensing signaling and inhibit the growth of a broad spectrum of Gram-negative beta- and gamma-proteobacteria. These compounds were isolated from Staphylococcus delphini. They represent a new class of quorum quenchers with the chemical formula N-[2-(1H-indol-3-yl)ethyl]-urea and N-(2-phenethyl)-urea, which we named yayurea A and B, respectively. In vitro studies with the N-acyl homoserine lactone (AHL) responding receptor LuxN of V. harveyi indicated that both compounds caused opposite effects on phosphorylation to those caused by AHL. This explains the quorum quenching activity. Staphylococcal strains producing yayurea A and B clearly benefit from an increased competitiveness in a mixed community. PMID:24098134

  20. Effects of natural and chemically synthesized furanones on quorum sensing in Chromobacterium violaceum

    Science.gov (United States)

    Martinelli, Daniel; Grossmann, Gilles; Séquin, Urs; Brandl, Helmut; Bachofen, Reinhard

    2004-01-01

    Background Cell to cell signaling systems in Gram-negative bacteria rely on small diffusible molecules such as the N-acylhomoserine lactones (AHL). These compounds are involved in the production of antibiotics, exoenzymes, virulence factors and biofilm formation. They belong to the class of furanone derivatives which are frequently found in nature as pheromones, flavor compounds or secondary metabolites. To obtain more information on the relation between molecular structure and quorum sensing, we tested a variety of natural and chemically synthesized furanones for their ability to interfere with the quorum sensing mechanism using a quantitative bioassay with Chromobacterium violaceum CV026 for antagonistic and agonistic action. We were looking at the following questions: 1. Do these compounds affect growth? 2) Do these compounds activate the quorum sensing system of C. violaceum CV026? 3) Do these compounds inhibit violacein formation induced by the addition of the natural inducer N-hexanoylhomoserine lactone (HHL)? 4) Do these compounds enhance violacein formation in presence of HHL? Results The naturally produced N-acylhomoserine lactones showed a strong non-linear concentration dependent influence on violacein production in C. violaceum with a maximum at 3.7*10-8 M with HHL. Apart from the N-acylhomoserine lactones only one furanone (emoxyfurane) was found to simulate N-acylhomoserine lactone activity and induce violacein formation. The most effective substances acting negatively both on growth and quorum sensing were analogs and intermediates in synthesis of the butenolides from Streptomyces antibioticus. Conclusion As the regulation of many bacterial processes is governed by quorum sensing systems, the finding of natural and synthetic furanones acting as agonists or antagonists suggests an interesting tool to control and handle detrimental AHL induced effects. Some effects are due to general toxicity; others are explained by a competitive interaction for Lux

  1. Uncertainty in model predictions of Vibrio vulnificus response to climate variability and change: a Chesapeake Bay case study.

    Directory of Open Access Journals (Sweden)

    Erin A Urquhart

    Full Text Available The effect that climate change and variability will have on waterborne bacteria is a topic of increasing concern for coastal ecosystems, including the Chesapeake Bay. Surface water temperature trends in the Bay indicate a warming pattern of roughly 0.3-0.4°C per decade over the past 30 years. It is unclear what impact future warming will have on pathogens currently found in the Bay, including Vibrio spp. Using historical environmental data, combined with three different statistical models of Vibrio vulnificus probability, we explore the relationship between environmental change and predicted Vibrio vulnificus presence in the upper Chesapeake Bay. We find that the predicted response of V. vulnificus probability to high temperatures in the Bay differs systematically between models of differing structure. As existing publicly available datasets are inadequate to determine which model structure is most appropriate, the impact of climatic change on the probability of V. vulnificus presence in the Chesapeake Bay remains uncertain. This result points to the challenge of characterizing climate sensitivity of ecological systems in which data are sparse and only statistical models of ecological sensitivity exist.

  2. Uncertainty in Model Predictions of Vibrio Vulnificus Response to Climate Variability and Change: A Chesapeake Bay Case Study

    Science.gov (United States)

    Urquhart, Erin A.; Zaitchik, Benjamin F.; Waugh, Darryn W.; Guikema, Seth D.; Del Castillo, Carlos E.

    2014-01-01

    The effect that climate change and variability will have on waterborne bacteria is a topic of increasing concern for coastal ecosystems, including the Chesapeake Bay. Surface water temperature trends in the Bay indicate a warming pattern of roughly 0.3-0.4 C per decade over the past 30 years. It is unclear what impact future warming will have on pathogens currently found in the Bay, including Vibrio spp. Using historical environmental data, combined with three different statistical models of Vibrio vulnificus probability, we explore the relationship between environmental change and predicted Vibrio vulnificus presence in the upper Chesapeake Bay. We find that the predicted response of V. vulnificus probability to high temperatures in the Bay differs systematically between models of differing structure. As existing publicly available datasets are inadequate to determine which model structure is most appropriate, the impact of climatic change on the probability of V. vulnificus presence in the Chesapeake Bay remains uncertain. This result points to the challenge of characterizing climate sensitivity of ecological systems in which data are sparse and only statistical models of ecological sensitivity exist.

  3. Necrotizing soft-tissue infections and sepsis caused by Vibrio vulnificus compared with those caused by Aeromonas species.

    Science.gov (United States)

    Tsai, Yao-Hung; Hsu, Robert Wen-Wei; Huang, Tsung-Jen; Hsu, Wei-Hsiu; Huang, Kuo-Chin; Li, Yen-Yao; Peng, Kuo-Ti

    2007-03-01

    Vibrio and Aeromonas species, which can cause necrotizing fasciitis and primary septicemia, are members of the Vibrionaceae family and thrive in aquatic environments. Because the clinical symptoms and signs of necrotizing fasciitis and sepsis caused by these two bacteria are similar, the purposes of this study were to describe the clinical characteristics of Vibrio vulnificus and Aeromonas infections, to analyze the risk factors for death, and to compare the effects of surgical treatment on the outcome. The cases of thirty-two patients with necrotizing soft-tissue infections and sepsis caused by Vibrio vulnificus (seventeen patients) and Aeromonas species (fifteen patients) were retrospectively reviewed over a four-year period. Surgical débridement or immediate limb amputation was initially performed in all patients. Demographic data, underlying diseases, laboratory results, and clinical outcome were analyzed for each patient in both groups. Six patients in the Vibrio vulnificus group and four patients in the Aeromonas group died. The patients who died had significantly lower serum albumin levels than did the patients who survived (p tissue infection with Vibrio vulnificus (contact with seawater or raw seafood) or Aeromonas species (contact with fresh or brackish water, soil, or wood). Early fasciotomy and culture-directed antimicrobial therapy should be aggressively performed in those patients with hypotensive shock, leukopenia, severe hypoalbuminemia, and underlying chronic illness, especially a combination of hepatic dysfunction and diabetes mellitus.

  4. Vibrio vulnificus infection in São Paulo, Brazil: case report and literature review

    Directory of Open Access Journals (Sweden)

    Maria Rita Elmor de Araujo

    Full Text Available Non cholera Vibrio may cause conjunctivitis, wound infection, gastroenteritis and serious sepsis. Transmission to men is through contact with skin, mucosa or wounds exposed to marine water, and consumption of certain barely cooked or raw seafood, more frequently in the summer. This is one of the first cases of severe infection related to Vibrio vulnificus described in Brazil. The patient was an old man, who ingested seafood in Guarujá, a seashore city near São Paulo, 3 days before hospitalization. He was admitted to the emergency room in an ill state with septic shock. On 2 sets of blood culture a highly virulent microorganism was isolated, Vibrio vulnificus, which leads to sepsis and frequently to death in susceptible patients. The objective of this report was to use this case to discuss clinical aspects, microbiological diagnosis and treatment of the infection caused by this agent, besides the review of epidemiology, associated risk factors and prevention before consuming or getting in contact with seafood, especially in patients with greater susceptibility to this kind of infection.

  5. A comparative epizootiologic study of the two fish-pathogenic serovars of Vibrio vulnificus biotype 2.

    Science.gov (United States)

    Fouz, B; Llorens, A; Valiente, E; Amaro, C

    2010-05-01

    Vibrio vulnificus biotype 2 is subdivided into two main serovars, serovar E, able to infect fish and humans, and serovar A, only virulent for fish. Serovar E emerged in 1976 as the causative agent of a haemorrhagic septicaemia (warm-water vibriosis) affecting eels cultured in brackish water. Serovar A emerged in 2000 in freshwater-cultured eels vaccinated against serovar E, causing warm-water vibriosis with fish showing a haemorrhagic intestine as the main differential sign. The aim of the present work was to compare the disease caused by both serovars in terms of transmission routes, portals of entry and host range. Results of bath, patch-contact and oral-anal challenges demonstrated that both serovars spread through water and infect healthy eels, serovar A entering mainly by the anus and serovar E by the gills. The course of the disease under laboratory conditions was similar for both serovars in terms of transmission and dependence of degree of virulence on water parameters (temperature and salinity). However, the decrease in degree of virulence in fresh water was significantly greater in serovar E than in serovar A. Finally, both serovars proved pathogenic for tilapia, sea bass and rainbow trout, but not for sea bream, with significant differences in degree of virulence only in rainbow trout. In conclusion, serovar A seems to represent a new antigenic form of V. vulnificus biotype 2 with an unusual portal of entry and is better adapted to fresh water than serovar E.

  6. An inhibitor of bacterial quorum sensing reduces mortalities caused by vibriosis in rainbow trout (Oncorhynchus mykiss, Walbaum)

    DEFF Research Database (Denmark)

    Rasch, Maria; Buch, Christiane; Austin, B.

    2004-01-01

    The fish pathogen Vibrio anguillarum produces quorum sensing signal molecules, N-acyl homoserine lactones (AHLs), which in several Gram-negative human and plant pathogenic bacteria regulate virulence factors. Expression of these factors can be blocked using specific quorum-sensing inhibitors (QSIs......). The purpose of this study was to investigate the effect of a QSI, furanone C-30, on mortality of rainbow trout during challenge with V. anguillarum. Addition of 0.01 or 0.1 muM furanone C-30 to rainbow trout infected by cohabitation caused a significant reduction in accumulated mortality from 80...

  7. Quorum Sensing Disruption in Vibrio harveyi Bacteria by Clay Materials.

    Science.gov (United States)

    Naik, Sajo P; Scholin, Jonathon; Ching, San; Chi, Fang; Herpfer, Marc

    2018-01-10

    This work describes the use of clay minerals as catalysts for the degradation of quorum sensing molecule N-(3-oxooctanoyl)-dl-homoserine lactone. Certain clay minerals as a result of their surface properties and porosity can catalytically degrade the quorum sensing molecule into smaller fragments. The disruption of quorum sensing by clay in a growing Gram-negative Vibrio harveyi bacteria culture was also studied by monitoring luminescence and population density of the bacteria, wherein quenching of bacterial quorum sensing activity was observed by means of luminescence reduction. The results of this study show that food-grade clays can be used as biocatalysts in disrupting bacterial activity in various media.

  8. Genome-wide SNP-genotyping array to study the evolution of the human pathogen Vibrio vulnificus biotype 3.

    Science.gov (United States)

    Raz, Nili; Danin-Poleg, Yael; Hayman, Ryan B; Bar-On, Yudi; Linetsky, Alex; Shmoish, Michael; Sanjuán, Eva; Amaro, Carmen; Walt, David R; Kashi, Yechezkel

    2014-01-01

    Vibrio vulnificus is an aquatic bacterium and an important human pathogen. Strains of V. vulnificus are classified into three different biotypes. The newly emerged biotype 3 has been found to be clonal and restricted to Israel. In the family Vibrionaceae, horizontal gene transfer is the main mechanism responsible for the emergence of new pathogen groups. To better understand the evolution of the bacterium, and in particular to trace the evolution of biotype 3, we performed genome-wide SNP genotyping of 254 clinical and environmental V. vulnificus isolates with worldwide distribution recovered over a 30-year period, representing all phylogeny groups. A custom single-nucleotide polymorphism (SNP) array implemented on the Illumina GoldenGate platform was developed based on 570 SNPs randomly distributed throughout the genome. In general, the genotyping results divided the V. vulnificus species into three main phylogenetic lineages and an additional subgroup, clade B, consisting of environmental and clinical isolates from Israel. Data analysis suggested that 69% of biotype 3 SNPs are similar to SNPs from clade B, indicating that biotype 3 and clade B have a common ancestor. The rest of the biotype 3 SNPs were scattered along the biotype 3 genome, probably representing multiple chromosomal segments that may have been horizontally inserted into the clade B recipient core genome from other phylogroups or bacterial species sharing the same ecological niche. Results emphasize the continuous evolution of V. vulnificus and support the emergence of new pathogenic groups within this species as a recurrent phenomenon. Our findings contribute to a broader understanding of the evolution of this human pathogen.

  9. Genome-Wide SNP-Genotyping Array to Study the Evolution of the Human Pathogen Vibrio vulnificus Biotype 3

    Science.gov (United States)

    Hayman, Ryan B.; Bar-On, Yudi; Linetsky, Alex; Shmoish, Michael; Sanjuán, Eva; Amaro, Carmen; Walt, David R.; Kashi, Yechezkel

    2014-01-01

    Vibrio vulnificus is an aquatic bacterium and an important human pathogen. Strains of V. vulnificus are classified into three different biotypes. The newly emerged biotype 3 has been found to be clonal and restricted to Israel. In the family Vibrionaceae, horizontal gene transfer is the main mechanism responsible for the emergence of new pathogen groups. To better understand the evolution of the bacterium, and in particular to trace the evolution of biotype 3, we performed genome-wide SNP genotyping of 254 clinical and environmental V. vulnificus isolates with worldwide distribution recovered over a 30-year period, representing all phylogeny groups. A custom single-nucleotide polymorphism (SNP) array implemented on the Illumina GoldenGate platform was developed based on 570 SNPs randomly distributed throughout the genome. In general, the genotyping results divided the V. vulnificus species into three main phylogenetic lineages and an additional subgroup, clade B, consisting of environmental and clinical isolates from Israel. Data analysis suggested that 69% of biotype 3 SNPs are similar to SNPs from clade B, indicating that biotype 3 and clade B have a common ancestor. The rest of the biotype 3 SNPs were scattered along the biotype 3 genome, probably representing multiple chromosomal segments that may have been horizontally inserted into the clade B recipient core genome from other phylogroups or bacterial species sharing the same ecological niche. Results emphasize the continuous evolution of V. vulnificus and support the emergence of new pathogenic groups within this species as a recurrent phenomenon. Our findings contribute to a broader understanding of the evolution of this human pathogen. PMID:25526263

  10. Effect of a BlpC-based quorum-sensing induction peptide on bacteriocin production in Streptococcus thermophiles

    Science.gov (United States)

    Bacteriocin synthesis in Streptococcus thermophilus is controlled by a complex blp locus. High levels of bacteriocin are produced only if the quorum-sensing regulatory mechanism is activated by the 30mer induction peptide (QSIP) which is embedded in the BlpC protein product of the blpC component. T...

  11. Crosstalk between mammalian cells and the microbiome through quorum sensing peptides, influencing cancer metastasis

    OpenAIRE

    Wynendaele, Evelien; Verbeke, Frederick; D'Hondt, Matthias; Hendrix, An; Van de Wiele, Christophe; Burvenich, Christian; Peremans, Kathelijne; De Wever, Olivier; Bracke, Marc; De Spiegeleer, Bart

    2014-01-01

    To date, the precise role of the human microbiome in health and disease remains largely unknown. Research mainly focused on the effect of toxins or DNA-damaging reactive oxygen species (ROS), produced by commensal or pathogenic bacteria, on inflammation or carcinogenesis.[1,2] In this study however, we demonstrate that quorum sensing peptides, secreted by intestinal bacteria, can also influence cancer cell behaviour: Phr0662 (Bacillus sp., ERNNT), EntF-metabolite (Enterococcus faecium, SNLVEC...

  12. Detection of Bacterial Quorum Sensing Molecules.

    Science.gov (United States)

    Stein, Elke; Schikora, Adam

    2018-01-01

    Bacterial cells use the quorum sensing system to communicate with each other. The gram-negative species very often use N-acyl homoserine lactones for this purpose. One of the easiest ways to detect these molecules is the use of particular reporter strains, which possess different kinds of reporter genes under the control of AHL-responsive promoters. Here we present some of the possibilities available today, even for not specialized researchers.

  13. Cadmium ion inhibition of quorum signalling in Chromobacterium violaceum.

    Science.gov (United States)

    Thornhill, Starla G; Kumar, Manish; Vega, Leticia M; McLean, Robert J C

    2017-10-01

    Single-celled bacteria are capable of acting as a community by sensing and responding to population density via quorum signalling. Quorum signalling in Chromobacterium violaceum, mediated by the luxI/R homologue, cviI/R, regulates a variety of phenotypes including violacein pigmentation, virulence and biofilm formation. A number of biological and organic molecules have been described as quorum signalling inhibitors but, to date, metal-based inhibitors have not been widely tested. In this study, we show that quorum sensing is inhibited in C. violaceum in the presence of sub-lethal concentrations of cadmium salts. Notable Cd2+-inhibition was seen against pigmentation, motility, chitinase production and biofilm formation. Cd-inhibition of quorum-signalling genes occurred at the level of transcription. There was no direct inhibition of chitinase activity by Cd2+ at the concentrations tested. Addition of the cognate quorum signals, N-hexanoyl homoserine lactone or N-decanoyl homoserine lactone, even at concentrations in excess of physiological levels, did not reverse the inhibition, suggesting that Cd-inhibition of quorum signaling is irreversible. This study represents the first description of heavy metal-based quorum inhibition in C. violaceum.

  14. Glyceryl trinitrate is a novel inhibitor of quorum sensing in ...

    African Journals Online (AJOL)

    Objectives: Investigation of the possible inhibition of quorum sensing-regulated virulence of Pseudomonas aeruginosa by glyceryltrinitrate. Methods: The quorum sensing inhibiting activity of glyceryl trinitrate was assessed by inhibition of violacein production in Chromobacterium violaceum ATCC 12472. Its ability to inhibit ...

  15. Repurposing metformin as a quorum sensing inhibitor in ...

    African Journals Online (AJOL)

    2017-09-03

    Sep 3, 2017 ... Abstract. Background: Quorum sensing is a mechanism of intercellular communication that controls the production of virulence fac- tors in Pseudomonas aeruginosa. Inhibition of quorum sensing can disarm the virulence factors without exerting stress on bacterial growth that leads to emergence of antibiotic ...

  16. Repurposing metformin as a quorum sensing inhibitor in ...

    African Journals Online (AJOL)

    Background: Quorum sensing is a mechanism of intercellular communication that controls the production of virulence factors in Pseudomonas aeruginosa. Inhibition of quorum sensing can disarm the virulence factors without exerting stress on bacterial growth that leads to emergence of antibiotic resistance. Objectives: ...

  17. Quorums Systems as a Method to Enhance Collaboration for Achieving Fault Tolerance in Distributed System

    Directory of Open Access Journals (Sweden)

    Ioan PETRI

    2009-01-01

    Full Text Available A system that implements the byzantine agreement algorithm is supposed to be very reliable and robust because of its fault tolerating feature. For very realistic environments, byzantine agreement protocols becomes inadequate, because they are based on the assumption that failures are controlled and they have unlimited severity. The byzantine agreement model works with a number of bounded failures that have to be tolerated. It is never concerned to identify these failures or to exclude them from the system. In this paper, we tackle quorum systems, which is a particular sort of distributed systems where some storage or computations are replicated on various machines in the idea that some of them work correctly to produce a reliable output at some given moment of time. Thus, by majority voting collaboration with quorums, one can achieve fault tolerance in distributed systems. Further, we argue that an algorithm to identify faulty-behaving machines is useful to identify purposeful malicious behaviors.

  18. Lack of AHL-based quorum sensing in Pseudomonas fluorescens isolated from milk

    Science.gov (United States)

    Martins, Maurilio L.; Pinto, Uelinton M.; Riedel, Kathrin; Vanetti, Maria C.D.; Mantovani, Hilário C.; de Araújo, Elza F.

    2014-01-01

    Numerous bacteria coordinate gene expression in response to small signalling molecules in many cases known as acylhomoserine lactones (AHLs), which accumulate as a function of cell density in a process known as quorum sensing. This work aimed to determine if phenotypes that are important to define microbial activity in foods such as biofilm formation, swarming motility and proteolytic activity of two Pseudomonas fluorescens strains, isolated from refrigerated raw milk, are influenced by AHL molecules. The tested P. fluorescens strains did not produce AHL molecules in none of the evaluated media. We found that biofilm formation was dependent on the culture media, but it was not influenced by AHLs. Our results indicate that biofilm formation, swarming motility and proteolytic activity of the tested P. fluorescens strains are not regulated by acyl-homoserine lactones. It is likely that AHL-dependent quorum sensing system is absent from these strains. PMID:25477941

  19. Metagenomic approaches to understanding phylogenetic diversity in quorum sensing

    Science.gov (United States)

    Kimura, Nobutada

    2014-01-01

    Quorum sensing, a form of cell–cell communication among bacteria, allows bacteria to synchronize their behaviors at the population level in order to control behaviors such as luminescence, biofilm formation, signal turnover, pigment production, antibiotics production, swarming, and virulence. A better understanding of quorum-sensing systems will provide us with greater insight into the complex interaction mechanisms used widely in the Bacteria and even the Archaea domain in the environment. Metagenomics, the use of culture-independent sequencing to study the genomic material of microorganisms, has the potential to provide direct information about the quorum-sensing systems in uncultured bacteria. This article provides an overview of the current knowledge of quorum sensing focused on phylogenetic diversity, and presents examples of studies that have used metagenomic techniques. Future technologies potentially related to quorum-sensing systems are also discussed. PMID:24429899

  20. Quorum sensing in CD4+ T cell homeostasis: a hypothesis and a model.

    Directory of Open Access Journals (Sweden)

    Afonso R.M. Almeida

    2012-05-01

    Full Text Available Homeostasis of lymphocyte numbers is believed to be due to competition between cellular populations for a common niche of restricted size, defined by the combination of interactions and trophic factors required for cell survival. Here we propose a new mechanism: homeostasis of lymphocyte numbers could also be achieved by the ability of lymphocytes to perceive the density of their own populations. Such a mechanism would be reminiscent of the primordial quorum sensing systems used by bacteria, in which some bacteria sense the accumulation of bacterial metabolites secreted by other elements of the population, allowing them to count the number of cells present and adapt their growth accordingly. We propose that homeostasis of CD4+ T cell numbers may occur via a quorum-sensing-like mechanism, where IL-2 is produced by activated CD4+ T cells and sensed by a population of CD4+ Treg cells that expresses the high-affinity IL-2Rα-chain and can regulate the number of activated IL-2-producing CD4+ T cells and the total CD4+T cell population. In other words, CD4+ T cell populations can restrain their growth by monitoring the number of activated cells, thus preventing uncontrolled lymphocyte proliferation during immune responses. We hypothesize that malfunction of this quorum-sensing mechanism may lead to uncontrolled T cell activation and autoimmunity. Finally, we present a mathematical model that describes the role of IL-2 and quorum-sensing mechanisms in CD4+ T cell homeostasis during an immune response.

  1. Correlations between Clinical Features and Mortality in Patients with Vibrio vulnificus Infection.

    Directory of Open Access Journals (Sweden)

    Hong Zhao

    Full Text Available Vibrio vulnificus is a common gram-negative bacterium, which might cause morbidity and mortality in patients following consumption of seafood or exposure to seawater in Southeast China. We retrospectively analyzed clinical data of patients with laboratory confirmed V. vulnificus infection. Twenty one patients were divided into a survival group and a non-surviving (or death group according to their clinical outcome. Clinical data and measurements were statistically analyzed. Four patients (19.05% died and five patients gave positive cultures from bile fluid, and 16 other patients gave positive culture from blood or blisters. Ten patients (47.62% had an underlying liver disease and marine-related events were found in sixteen patients (76.2%. Patients with heavy drinking habits might be at increased mortality (p = 0.028. Clinical manifestations of cellulitis (47.6%, septic shock (42.9% and multiple organ failure (28.6% were statistically significant when comparing survivors and non-survivors (p = 0.035, p = 0.021 and p = 0.003, respectively. The laboratory results, including hemoglobin < 9.0 g/L (p = 0.012, platelets < 2.0 × 109 /L, prothrombin time activity (PTA <20%, decreased serum creatinine and increased urea nitrogen were statistically significant (p = 0.012, p = 0.003, p = 0.028 and p = 0.028, respectively. Patients may be at a higher risk of mortality under situations where they have a history of habitual heavy alcoholic drink consumption (p = 0.028, OR = 22.5, 95%CI 1.5-335.3, accompanied with cellulitis, shock, multiple organ failure, and laboratory examinations that are complicated by decreased platelets, hemoglobin and significantly prolonged prothrombin time (PT.

  2. Necrotising fasciitis causing compartment syndrome of the forearm and septic shock due to Vibrio vulnificus: a case report.

    Science.gov (United States)

    Leechavengvongs, Somsak; Jidpugdeebodin, Suwanee; Milindankura, Samaniya

    2006-01-01

    Compartment syndrome caused by necrotising fasciitis has rarely been described. We report a case of systemic Vibrio vulnificus necrotising fasciitis presented with compartmental syndrome of the forearm and septic shock. The patient was treated with systemic antibiotic treatment and urgent surgical decompression followed by multiple necrotic tissue debridements. The patient recovered with some limited motion of the hand function. Prompt recognition and immediate treatment with antibiotics and surgical intervention are essential.

  3. Bacterial biofilms. Bacteria Quorum sensing in biofilms

    Directory of Open Access Journals (Sweden)

    E. S. Vorobey

    2012-03-01

    Full Text Available Data on biofilms, their structure and properties, peculiarities of formation and interaction between microorganisms in the film are presented. Information on discovery and study of biofilms, importance of biofilms in the medical and clinical microbiology are offered. The data allow to interpret biofilm as a form of existence of human normal microflora. For the exchange of information within the biofilm between the individual cells of the same or different species bacteria use the signal molecules of the Quorum sensing system. Coordination of bacterial cells activity in the biofilms gives them significant advantages: in the biofilms bacteria are protected from the influence of the host protective factors and the antibacterial drugs.

  4. Vibrio vulnificus biotype 3 multifunctional autoprocessing RTX toxin is an adenylate cyclase toxin essential for virulence in mice.

    Science.gov (United States)

    Ziolo, Kevin J; Jeong, Hee-Gon; Kwak, Jayme S; Yang, Shuangni; Lavker, Robert M; Satchell, Karla J F

    2014-05-01

    Vibrio vulnificus is an environmental organism that causes both food-borne and wound infections with high morbidity and mortality in humans. The annual incidence and global distribution of infections associated with this pathogen are increasing with climate change. In the late 1990s, an outbreak of tilapia-associated wound infections in Israel was linked to a previously unrecognized variant of V. vulnificus designated biotype 3. The sudden emergence and clonality of the outbreak suggest that this strain may be a true newly emergent pathogen with novel virulence properties compared to those of other V. vulnificus strains. In a subcutaneous infection model to mimic wound infection, the multifunctional autoprocessing RTX (MARTX) toxin of biotype 3 strains was shown to be an essential virulence factor contributing to highly inflammatory skin wounds with severe damage affecting every tissue layer. We conducted a sequencing-based analysis of the MARTX toxin and found that biotype 3 MARTX toxin has an effector domain structure distinct from that of either biotype 1 or biotype 2. Of the two new domains identified, a domain similar to Pseudomonas aeruginosa ExoY was shown to confer adenylate cyclase activity on the MARTX toxin. This is the first demonstration that the biotype 3 MARTX toxin is essential for virulence and that the ExoY-like MARTX effector domain is a catalytically active adenylate cyclase.

  5. Role of extracellular matrix protein CabA in resistance of Vibrio vulnificus biofilms to decontamination strategies.

    Science.gov (United States)

    Park, Jin Hwan; Lee, Byungho; Jo, Youmi; Choi, Sang Ho

    2016-11-07

    Biofilms are recalcitrant and raise safety problems in the food industry. In this study, the role of CabA, an extracellular matrix protein, in the resistance of the biofilms of Vibrio vulnificus, a foodborne pathogen, to decontamination strategies was investigated. Biofilms of the cabA mutant revealed reduced resistance to detachment by vibration and disinfection by sodium hypochlorite compared to the biofilms of the parental wild type in vitro. The reduced resistance of the cabA mutant biofilms was complemented by introducing a recombinant cabA, indicating that the reduced resistance of the cabA mutant biofilms is caused by the inactivation of cabA. The expression of cabA was induced in cells bound to oyster, the primary vehicle of the pathogen. The cabA mutant biofilms on oyster are defective in biomass and resistance to detachment and disinfection. The bacterial cells in the wild-type biofilms are clustered by filaments which are not apparent in the cabA mutant biofilms. The combined results indicated that CabA contributes to the structural integrity of V. vulnificus biofilms possibly by forming filaments in the matrix and thus rendering the biofilms robust, suggesting that CabA could be a target to control V. vulnificus biofilms on oyster. Copyright © 2016 Elsevier B.V. All rights reserved.

  6. Quorum Sensing Influences Burkholderia thailandensis Biofilm Development and Matrix Production.

    Science.gov (United States)

    Tseng, Boo Shan; Majerczyk, Charlotte D; Passos da Silva, Daniel; Chandler, Josephine R; Greenberg, E Peter; Parsek, Matthew R

    2016-10-01

    Members of the genus Burkholderia are known to be adept at biofilm formation, which presumably assists in the survival of these organisms in the environment and the host. Biofilm formation has been linked to quorum sensing (QS) in several bacterial species. In this study, we characterized Burkholderia thailandensis biofilm development under flow conditions and sought to determine whether QS contributes to this process. B. thailandensis biofilm formation exhibited an unusual pattern: the cells formed small aggregates and then proceeded to produce mature biofilms characterized by "dome" structures filled with biofilm matrix material. We showed that this process was dependent on QS. B. thailandensis has three acyl-homoserine lactone (AHL) QS systems (QS-1, QS-2, and QS-3). An AHL-negative strain produced biofilms consisting of cell aggregates but lacking the matrix-filled dome structures. This phenotype was rescued via exogenous addition of the three AHL signals. Of the three B. thailandensis QS systems, we show that QS-1 is required for proper biofilm development, since a btaR1 mutant, which is defective in QS-1 regulation, forms biofilms without these dome structures. Furthermore, our data show that the wild-type biofilm biomass, as well as the material inside the domes, stains with a fucose-binding lectin. The btaR1 mutant biofilms, however, are negative for fucose staining. This suggests that the QS-1 system regulates the production of a fucose-containing exopolysaccharide in wild-type biofilms. Finally, we present data showing that QS ability during biofilm development produces a biofilm that is resistant to dispersion under stress conditions. The saprophyte Burkholderia thailandensis is a close relative of the pathogenic bacterium Burkholderia pseudomallei, the causative agent of melioidosis, which is contracted from its environmental reservoir. Since most bacteria in the environment reside in biofilms, B. thailandensis is an ideal model organism for

  7. Quorum sensing and bacterial pathogenicity: From molecules to disease

    Directory of Open Access Journals (Sweden)

    Antariksh Deep

    2011-01-01

    Full Text Available 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 bacteria a mechanism to minimize host immune responses by delaying the production of tissue-damaging virulence factors until sufficient bacteria have amassed and are prepared to overwhelm host defense mechanisms and establish infection. Quorum sensing systems are studied in a large number of gram-negative bacterial species belonging to α, β, and γ 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.

  8. Bacillus sp. QSI-1 modulate quorum sensing signals reduce Aeromonas hydrophila level and alter gut microbial community structure in fish

    Directory of Open Access Journals (Sweden)

    Shuxin Zhou

    2016-12-01

    Full Text Available Quorum sensing (QS is a cell density dependent process that enables bacteria to communicate with each other based on the production, secretion and sensing of the auto-inducer molecules and then subsequently regulate virulence associated gene expression. Interrupting quorum sensing may represent a novel alternative approach to combat bacterial pathogen. Several bacteria can produce quorum quenching (QQ enzymes. However, the role of QQ bacteria in shaping the microbiota and the level of N-acyl-homoserine lactones (AHLs, a prevalent type of QS molecules producing bacteria remains largely unknown. The objective of this study was to examine the presence of AHLs in the fish intestine and investigate the modulation of gut microbiota and its effect on Aeromonas hydrophila level by a QQ enzyme producing probiotic Bacillus sp.QSI-1. AHLs were found in fish gut content and were confirmed in Aeromonas species using Chromobacterium violaceum CV026 and Agrobacterium tumefaciens AT 136 (pZLR4 as reporter strains. We demonstrated that the composition of fish gut microbiota was affected by quenching bacteria QSI-1, and the percentage of A. hydrophila was decreased significantly. Taken together, these results provide valuable insights into QQ enzyme producing probiotics can modulate the microbiota structure and decrease the percentage of AHL-producing pathogenic bacteria in the gut. These data strongly suggest that QQ probiotics may serve as non-antibiotic feed additive in aquaculture to control bacterial diseases.

  9. 17 CFR 200.41 - Quorum of the Commission.

    Science.gov (United States)

    2010-04-01

    ...; CONDUCT AND ETHICS; AND INFORMATION AND REQUESTS Disposition of Commission Business § 200.41 Quorum of the... office; and provided further that on any matter of business as to which the number of members in office...

  10. Characterization of bacteria degrading 3-hydroxy palmitic acid methyl ester (3OH-PAME), a quorum sensing molecule of Ralstonia solanacearum.

    Science.gov (United States)

    Achari, G A; Ramesh, R

    2015-05-01

    Bacterial wilt pathogen Ralstonia solanacearum causes severe crop loss of eggplant, which is of economic importance in India. 3-hydroxy palmitic acid methyl ester (3OH-PAME) is the main quorum sensing molecule governing the expression of virulence factors in R. solanacearum. Ability of 164 bacterial isolates from the xylem of eggplant (Solanum melongena L.), chilli pepper (Capsicum annuum L.) and wild eggplant (Solanum torvum Sw.) to degrade 3OH-PAME was tested by disc diffusion assay. Enzymatic degradation of 3OH-PAME by five bacteria was confirmed by High-Performance Liquid Chromatography-Mass Spectrometry analysis. 3OH-PAME degrading bacteria were identified as Stenotrophomonas maltophilia, Pseudomonas aeruginosa and Rhodococcus corynebacterioides. 3OH-PAME degrading bacteria reduced the expression of virulence factors (exopolysaccharides and endoglucanase) of R. solanacearum in vitro and reduced wilt incidence in eggplant seedlings under greenhouse conditions. Isolates with quorum quenching activity successfully re-colonized eggplant seedlings. Quorum quenching bacteria produced antagonistic compounds, which may act synergistically with quorum quenching in reducing bacterial wilt in eggplant. This is the first report on endophytic bacteria of class Gammaproteobacteria and phylum Actinobacteria having 3OH-PAME degrading activity. This study demonstrates the potential use of endophytic bacteria as quorum quenching biocontrol agents for management of bacterial wilt in eggplant. © 2015 The Society for Applied Microbiology.

  11. How Quorum Sensing Connects Sporulation to Necrotrophism in Bacillus thuringiensis

    OpenAIRE

    Stéphane Perchat; Antoine Talagas; Sandrine Poncet; Noureddine Lazar; Inès Li de la Sierra-Gallay; Michel Gohar; Didier Lereclus; Sylvie Nessler

    2016-01-01

    Bacteria use quorum sensing to coordinate adaptation properties, cell fate or commitment to sporulation. The infectious cycle of Bacillus thuringiensis in the insect host is a powerful model to investigate the role of quorum sensing in natural conditions. It is tuned by communication systems regulators belonging to the RNPP family and directly regulated by re-internalized signaling peptides. One such RNPP regulator, NprR, acts in the presence of its cognate signaling peptide NprX as a transcr...

  12. SURVEY ON V. CHOLERAE, V. VULNIFICUS AND V. PARAHAEMOLYTICUS IN BIVALVE MOLLUSCS OF THE ADRIATIC SEA AND PROPOSAL OF AN ANALYTICAL PROTOCOL

    Directory of Open Access Journals (Sweden)

    M.L. Valeri

    2009-06-01

    Full Text Available Bivalve molluscs from Adriatic sea were analyzed for V. parahaemolyticus, V. cholerae e V. vulnificus presence. The isolates on TCBS Agar and m-CPC Agar were selected on the basis of a new biochemical screening, that showed a good performance, because among 2344 strains from primary culture only 237 (10% were presumptively assigned to the species of interest. The PCR analyses was performed for the target genes toxR hlyA, ctxA, tcpI (V. cholerae, toxR, tl, tdh, trh (V. parahaemolyticus, vvhA and viuB (V. vulnificus. Among the 9 strains confirmed to belong to V. parahaemolyticus specie, 6 were sucrose positive. On 215 samples of molluscs only 5 resulted positive for V. parahaemolyticus being toxR+, tl+, although non pathogenic (tdh-, trh-, and none for V. cholerae e V. vulnificus.

  13. Clinical Usefulness of Real-Time Polymerase Chain Reaction for the Diagnosis of Vibrio vulnificus Infection Using Skin and Soft Tissues.

    Science.gov (United States)

    Lee, Jun-Young; Kim, Seok Won; Kim, Dong-Min; Yun, Na Ra; Kim, Choon-Mee; Lee, Sang-Hong

    2017-08-01

    Vibrio vulnificus is a halophilic gram-negative bacillus isolated in seawater, fish, and shellfish. Infection by V. vulnificus is the most severe food-borne infection reported in the United States of America. Here, we aimed to examine the clinical usefulness of polymerase chain reaction (PCR) using tissue specimens other than blood samples as a diagnostic tool for V. vulnificus infection. A retrospective study was conducted with patients who underwent real-time PCR of toxR in both blood and skin tissues, including serum, bullae, swab, and operation room specimens, between 2006 and 2009. The median V. vulnificus DNA load of 14 patients in real-time PCR analysis of serum at the time of admission was 638.5 copies/mL blood, which was within the interquartile range (IQR: 37-3,225). In contrast, the median value by real-time PCR using the first tissue specimen at the time of admission was 16,650 copies/mL tissue fluid (IQR: 4,419-832,500). This difference was statistically significant (P = 0.022). DNA copy numbers in tissues were less affected by short-term antibiotic administration than that in blood samples, and antibiotic administration increased the DNA copy number in some patients. We found, for the first time, that DNA copy numbers in tissues of patients infected by V. vulnificus were higher than those in blood samples. Additionally, skin lesions were more useful than blood samples as specimens for PCR analysis in patients administered antibiotics for V. vulnificus infection before admission.

  14. Quorum Sensing in Marine Microbial Environments

    Science.gov (United States)

    Hmelo, Laura R.

    2017-01-01

    Quorum sensing (QS) is a form of chemical communication used by certain bacteria that regulates a wide range of biogeochemically important bacterial behaviors. Although QS was first observed in a marine bacterium nearly four decades ago, only in the past decade has there been a rise in interest in the role that QS plays in the ocean. It has become clear that QS, regulated by signals such as acylated homoserine lactones (AHLs) or furanosyl-borate diesters [autoinducer-2 (AI-2) molecules], is involved in important processes within the marine carbon cycle, in the health of coral reef ecosystems, and in trophic interactions between a range of eukaryotes and their bacterial associates. The most well-studied QS systems in the ocean occur in surface-attached (biofilm) communities and rely on AHL signaling. AHL-QS is highly sensitive to the chemical and biological makeup of the environment and may respond to anthropogenic change, including ocean acidification and rising sea surface temperatures.

  15. Suspension of oysters reduces the populations of Vibrio parahaemolyticus and Vibrio vulnificus.

    Science.gov (United States)

    Cole, K M; Supan, J; Ramirez, A; Johnson, C N

    2015-09-01

    Vibrio parahaemolyticus (Vp) and Vibrio vulnificus (Vv) are associated with the consumption of raw oysters and cause illnesses ranging from simple gastroenteritis to life-threatening septicaemia. These halophilic bacteria are frequently found in marine and estuarine systems, accumulating within the tissues of a number of aquatic organisms and passing on to humans after consumption, through contaminated water, or via open wounds. As benthic organisms capable of filtering 40 gallons of water per hour, sediment is an important source of potentially pathogenic vibrios in oysters destined for raw consumption. This research used off-bottom oyster culture to reduce vibrio concentrations in oysters. Colony hybridization was used to enumerate Vp and Vv in bottom and suspended oysters. Vv and Vp concentrations were generally lower in oysters suspended off-bottom, and suspension decreased vibrio loads in oysters by an average of 13%. Suspension of oysters reduced vibrio concentrations. This study found that oyster suspension significantly reduced some populations of potentially pathogenic vibrios. These results indicate that oyster suspension could be a viable approach for preharvest treatment to reduce illness in consumers of raw oysters. © 2015 The Society for Applied Microbiology.

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

    National Research Council Canada - National Science Library

    Kumar, Ravi; Chhibber, Sanjay; Harjai, Kusum

    2009-01-01

    .... 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...

  17. Quorum Sensing: a Transcriptional Regulatory System Involved in the Pathogenicity of Burkholderia mallei

    OpenAIRE

    Ulrich, Ricky L.; DeShazer, David; Hines, Harry B.; Jeddeloh, Jeffrey A

    2004-01-01

    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,...

  18. Virulence of Burkholderia mallei quorum-sensing mutants.

    Science.gov (United States)

    Majerczyk, Charlotte; Kinman, Loren; Han, Tony; Bunt, Richard; Greenberg, E Peter

    2013-05-01

    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.

  19. Anti-Quorum Sensing Potential of Potato Rhizospheric Bacteria

    Directory of Open Access Journals (Sweden)

    Adeleh Sobhanipour

    2017-01-01

    Full Text Available The occurrence of antibiotic-resistant pathogenic bacteria is becoming a serious problem. The rise of multiresistance strains has forced the pharmaceutical industry to come up with new generation of more effective and potent antibiotics, therefore creating development of antivirulence compounds. Due to extensive usage of cell-to-cell bacterial communication (QS systems to monitor the production of virulence factors, disruption of QS system results in creation of a promising strategy for the control of bacterial infection. Numerous natural quorum quenching (QQ agents have been identified. In addition, many microorganisms are capable of producing smaller molecular QS inhibitors and/or macromolecular QQ enzymes. In present survey, anti QS activity of 1280 rhizosphere bacteria was assessed using the Pectobacterium carotovorum as AHL-donor and Chromobacterium violaceum CV026 as biosensor system. The results showed that 61 strains had highly AHL-degrading activity. Both Lux I and Lux R activity were affected by some isolates, suggesting that the rhizobacteria target both QS signal and receptor. These soil microorganisms with their anti-QS activity have the potential to be novel therapeutic agents for reducing virulence and pathogenicity of antibiotic resistant bacteria.

  20. Rapid proliferation of Vibrio parahaemolyticus, Vibrio vulnificus, and Vibrio cholerae during freshwater flash floods in French Mediterranean coastal lagoons.

    Science.gov (United States)

    Esteves, Kevin; Hervio-Heath, Dominique; Mosser, Thomas; Rodier, Claire; Tournoud, Marie-George; Jumas-Bilak, Estelle; Colwell, Rita R; Monfort, Patrick

    2015-11-01

    Vibrio parahaemolyticus, Vibrio vulnificus, and Vibrio cholerae of the non-O1/non-O139 serotype are present in coastal lagoons of southern France. In these Mediterranean regions, the rivers have long low-flow periods followed by short-duration or flash floods during and after heavy intense rainstorms, particularly at the end of the summer and in autumn. These floods bring large volumes of freshwater into the lagoons, reducing their salinity. Water temperatures recorded during sampling (15 to 24°C) were favorable for the presence and multiplication of vibrios. In autumn 2011, before heavy rainfalls and flash floods, salinities ranged from 31.4 to 36.1‰ and concentrations of V. parahaemolyticus, V. vulnificus, and V. cholerae varied from 0 to 1.5 × 10(3) most probable number (MPN)/liter, 0.7 to 2.1 × 10(3) MPN/liter, and 0 to 93 MPN/liter, respectively. Following heavy rainstorms that generated severe flash flooding and heavy discharge of freshwater, salinity decreased, reaching 2.2 to 16.4‰ within 15 days, depending on the site, with a concomitant increase in Vibrio concentration to ca. 10(4) MPN/liter. The highest concentrations were reached with salinities between 10 and 20‰ for V. parahaemolyticus, 10 and 15‰ for V. vulnificus, and 5 and 12‰ for V. cholerae. Thus, an abrupt decrease in salinity caused by heavy rainfall and major flooding favored growth of human-pathogenic Vibrio spp. and their proliferation in the Languedocian lagoons. Based on these results, it is recommended that temperature and salinity monitoring be done to predict the presence of these Vibrio spp. in shellfish-harvesting areas of the lagoons. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

  1. Vibrio vulnificus MO6-24/O Lipopolysaccharide Stimulates Superoxide Anion, Thromboxane B2, Matrix Metalloproteinase-9, Cytokine and Chemokine Release by Rat Brain Microglia in Vitro

    Directory of Open Access Journals (Sweden)

    Alejandro M. S. Mayer

    2014-03-01

    Full Text Available Although human exposure to Gram-negative Vibrio vulnificus (V. vulnificus lipopolysaccharide (LPS has been reported to result in septic shock, its impact on the central nervous system’s innate immunity remains undetermined. The purpose of this study was to determine whether V. vulnificus MO6-24/O LPS might activate rat microglia in vitro and stimulate the release of superoxide anion (O2−, a reactive oxygen species known to cause oxidative stress and neuronal injury in vivo. Brain microglia were isolated from neonatal rats, and then treated with either V. vulnificus MO6-24/O LPS or Escherichia coli O26:B6 LPS for 17 hours in vitro. O2− was determined by cytochrome C reduction, and matrix metalloproteinase-2 (MMP-2 and MMP-9 by gelatinase zymography. Generation of cytokines tumor necrosis factor alpha (TNF-α, interleukin-1 alpha (IL-1α, IL-6, and transforming growth factor-beta 1 (TGF-β1, chemokines macrophage inflammatory protein (MIP-1α/chemokine (C-C motif ligand 3 (CCL3, MIP-2/chemokine (C-X-C motif ligand 2 (CXCL2, monocyte chemotactic protein-1 (MCP-1/CCL2, and cytokine-induced neutrophil chemoattractant-2alpha/beta (CINC-2α/β/CXCL3, and brain-derived neurotrophic factor (BDNF, were determined by specific immunoassays. Priming of rat microglia by V. vulnificus MO6-24/O LPS in vitro yielded a bell-shaped dose-response curve for PMA (phorbol 12-myristate 13-acetate-stimulated O2− generation: (1 0.1–1 ng/mL V. vulnificus LPS enhanced O2− generation significantly but with limited inflammatory mediator generation; (2 10–100 ng/mL V. vulnificus LPS maximized O2− generation with concomitant release of thromboxane B2 (TXB2, matrix metalloproteinase-9 (MMP-9, and several cytokines and chemokines; (3 1000–100,000 ng/mL V. vulnificus LPS, with the exception of TXB2, yielded both attenuated O2− production, and a progressive decrease in MMP-9, cytokines and chemokines investigated. Thus concentration-dependent treatment of

  2. Computer-aided identification of recognized drugs as Pseudomonas aeruginosa quorum-sensing inhibitors

    DEFF Research Database (Denmark)

    Yang, Liang; Rybtke, Morten Theil; Jakobsen, Tim Holm

    2009-01-01

    R, 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...

  3. Combination Therapy Strategy of Quorum Quenching Enzyme and Quorum Sensing Inhibitor in Suppressing Multiple Quorum Sensing Pathways of P. aeruginosa

    DEFF Research Database (Denmark)

    Fong, July; Zhang, Chaodong; Yang, Renliang

    2018-01-01

    The threat of antibiotic resistant bacteria has called for alternative antimicrobial strategies that would mitigate the increase of classical resistance mechanism. Many bacteria employ quorum sensing (QS) to govern the production of virulence factors and formation of drug-resistant biofilms...

  4. Effects of ambient exposure, refrigeration, and icing on Vibrio vulnificus and Vibrio parahaemolyticus abundances in oysters.

    Science.gov (United States)

    Jones, J L; Lydon, K A; Kinsey, T P; Friedman, B; Curtis, M; Schuster, R; Bowers, J C

    2017-07-17

    Vibrio vulnificus (Vv) and V. parahaemolyticus (Vp) illnesses are typically acquired through the consumption of raw molluscan shellfish, particularly oysters. As Vibrio spp. are naturally-occurring bacteria, one means of mitigation of illness is achieved by limiting post-harvest growth. In this study, effects of ambient air storage, refrigeration, and icing of oysters on Vibrio spp. abundances were examined at two sites in Alabama (AL) [Dog River (DR) and Cedar Point (CP)] and one site in Delaware Bay, New Jersey (NJ). As the United States shellfish program recommendations include testing for total these organisms and gene targets, Vv and total (tlh) and pathogenic (tdh+ and trh+) Vp were enumerated from samples using MPN-real-time-PCR approaches. Mean Vv and Vp abundances in oysters from AL-DR were lowest in immediately iced samples (2.3 and -0.1 log MPN/g, respectively) and highest in the 5h ambient then refrigerated samples (3.4 and 0.5 log MPN/g, respectively). Similarly, in AL-CP Vv and Vp mean levels in oysters were lowest in immediately iced samples (3.6 and 1.2 log MPN/g, respectively) and highest in 5h ambient then refrigerated samples (5.1 and 3.2 log MPN/g, respectively). Mean levels of pathogenic Vp from AL sites were frequently below the limit of detection (ice resulted in lower Vibrio spp. levels in oysters, compared to those that were refrigerated post-harvest. These results suggest vibriosis risk can be mitigated by shorter storage times and more rapid cooling of oysters, providing data regulatory authorities can use to evaluate Vibrio spp. control plans. Published by Elsevier B.V.

  5. Effectiveness of icing as a postharvest treatment for control of Vibrio vulnificus and Vibrio parahaemolyticus in the eastern oyster (Crassostrea virginica).

    Science.gov (United States)

    Melody, Kevin; Senevirathne, Reshani; Janes, Marlene; Jaykus, Lee Ann; Supan, John

    2008-07-01

    The focus of this research was to investigate the efficacy of icing as a postharvest treatment for reduction of the levels of Vibrio vulnificus and Vibrio parahaemolyticus in commercial quantities of shellstock oysters. The experiments were conducted in June and August of 2006 and consisted of the following treatments: (i) on-board icing immediately after harvest; (ii) dockside icing approximately 1 to 2 h prior to shipment; and (iii) no icing (control). Changes in the levels of pathogenic Vibrio spp. during wholesale and retail handling for 2 weeks postharvest were also monitored. On-board icing achieved temperature reductions in all sacks in accordance with the National Shellfish Sanitation Program standard, but dockside icing did not meet this standard. Based on one-way analysis of variance, the only statistically significant relationship between Vibrio levels and treatment occurred for samples harvested in August; in this case, the levels of V. vulnificus in the noniced oysters were significantly higher (P iced on-board. When analyzing counts over the 14-day storage period, using factorial analysis, there were statistically significant differences in V. vulnificus and V. parahaemolyticus levels by sample date and/or treatment (P iced) oysters had significantly higher gaping (approximately 20%) after 1 week in cold storage than did noniced oysters (approximately 10%) and gaping increased significantly by day 14 of commercial storage. On-board and dockside icing did not predictably reduce the levels of V. vulnificus or V. parahaemolyticus in oysters, and icing negatively impacted oyster survival during subsequent cold storage.

  6. Light scattering sensor for real-time identification of Vibrio parahaemolyticus, V. vulnificus and V. cholera colonies on solid agar plates

    Science.gov (United States)

    The three most common pathogenic species of Vibrio, V. cholerae, V. parahemolyticus and V. vulnificus, are of major concern as water- and food-borne pathogens because of an increasing incidence of water and seafood related outbreaks and illnesses worldwide. Current methods are time-consuming and req...

  7. Quorum sensing signalling and biofilm formation of brewery-derived bacteria, and inhibition of signalling by natural compounds.

    Science.gov (United States)

    Priha, O; Virkajärvi, V; Juvonen, R; Puupponen-Pimiä, R; Nohynek, L; Alakurtti, S; Pirttimaa, M; Storgårds, E

    2014-11-01

    Bacteria use quorum sensing signalling in various functions, e.g. while forming biofilms, and inhibition of this signalling could be one way to control biofilm formation. The aim of this study was to evaluate the production of signalling molecules and its correlation with the biofilm formation capability of bacteria isolated from brewery filling process. A further aim was to study berry extracts and wood-derived terpenes for their possible quorum sensing inhibitory effects. Out of the twenty bacteria studied, five produced short-chain and five long-chain AHL (acyl homoserine lactone) signalling molecules when tested with the Chromobacterium violaceum CV026 reporter bacterium. Production of AI-2 (autoinducer-2) signalling molecules was detected from nine strains with the Vibrio harveyi BB170 bioassay. Over half of the strains produced biofilm in the microtitre plate assay, but the production of AHL and AI-2 signalling molecules and biofilm formation capability did not directly correlate with each other. Out of the 13 berry extracts and wood-derived terpenes screened, four compounds decreased AHL signalling without effect on growth. These were betulin, raspberry extract and two cloudberry extracts. The effect of these compounds on biofilm formation of the selected six bacterial strains varied. The phenolic extract of freeze-dried cloudberry fruit caused a statistically significant reduction of biofilm formation of Obesumbacterium proteus strain. Further experiments should aim at identifying the active compounds and revealing whether quorum sensing inhibition causes structural changes in the biofilms formed.

  8. Detection of quorum sensing signal molecules and identification of an autoinducer synthase gene among biofilm forming clinical isolates of Acinetobacter spp.

    Directory of Open Access Journals (Sweden)

    Deepa Anbazhagan

    Full Text Available BACKGROUND: Quorum sensing is a term that describes an environmental sensing system that allows bacteria to monitor their own population density which contributes significantly to the size and development of the biofilm. Many gram negative bacteria use N-acyl-homoserine lactones as quorum sensing signal molecules. In this study, we sought to find out if the biofilm formation among clinical isolates of Acinetobacter spp. is under the control of autoinducing quorum sensing molecules. METHODOLOGY/PRINCIPAL FINDINGS: Biofilm formation among clinical isolates of Acinetobacter spp. was assessed and the production of signal molecules were detected with Chromobacterium violaceum CV026 biosensor system. Characterisation of autoinducers was carried out by mass spectrometric analysis. We have also reported the identification of an autoinducer synthase gene, abaΙ among the isolates that produce quorum sensing signal molecules and have reported that the mutation in the abaI gene influences their biofilm forming capabilities. Using a microtitre-plate assay it was shown that 60% of the 50 Acinetobacter spp. isolates significantly formed biofilms. Further detection with the biosensor strain showed that some of these isolates produced long chain signal molecules. Mass spectrometric analysis revealed that five of these isolates produced N-decanoyl homoserine lactone and two isolates produced acyl-homoserine lactone with a chain length equal to C(12. The abaΙ gene was identified and a tetracycline mutant of the abaΙ gene was created and the inhibition in biofilm formation in the mutant was shown. CONCLUSIONS/SIGNIFICANCE: These data are of great significance as the signal molecules aid in biofilm formation which in turn confer various properties of pathogenicity to the clinical isolates including drug resistance. The use of quorum sensing signal blockers to attenuate bacterial pathogenicity is therefore highly attractive, particularly with respect to the

  9. Quorum sensing in Acinetobacter: with special emphasis on antibiotic resistance, biofilm formation and quorum quenching

    Directory of Open Access Journals (Sweden)

    Bindu Subhadra

    2016-02-01

    Full Text Available Acinetobacter is an important nosocomial, opportunistic human pathogen that is gradually gaining more attention as a major health threat worldwide. Quorum sensing (QS is a cell-cell communication system in which specific signaling molecules called autoinducers accumulate in the medium as the population density grows and control various physiological processes including production of virulence factors, biofilm and development of antibiotic resistance. The complex QS machinery in Acinetobacter is mediated by a two-component system which is homologous to the typical LuxI/LuxR system found in Gram-negative bacteria. This cell signaling system comprises of a sensor protein that functions as autoinducer synthase and a receptor protein which binds to the signal molecules, acyl homoserine lactones inducing a cascade of reactions. Lately, disruption of QS has emerged as an anti-virulence strategy with great therapeutic potential. Here, we depict the current understanding of the existing QS network in Acinetobacter and describe important anti-virulent strategies developed in order to effectively tackle this pathogen. In addition, the prospects of quorum quenching to control Acinetobacter infections is also been discussed.

  10. Antibiotics Promote Escherichia coli-Pseudomonas aeruginosa Conjugation through Inhibiting Quorum Sensing.

    Science.gov (United States)

    Lu, Yang; Zeng, Jianming; Wang, Linjing; Lan, Kai; E, Shunmei; Wang, Lina; Xiao, Qian; Luo, Qiang; Huang, Xianzhang; Huang, Bin; Chen, Cha

    2017-12-01

    The effect of antibiotics on horizontal gene transfer (HGT) is controversial, and the underlying mechanism remains poorly understood. Here, using Escherichia coli SM10λπ as the donor strain, which carries a chromosomally integrated RP4 plasmid, we investigated the effect of antibiotics on conjugational transfer of a mobilizable gentamicin (Gm) resistance plasmid. The results showed that an exposure to gentamicin that restricted the survival of recipient cells significantly enhanced SM10λπ-Pseudomonas aeruginosa PAO1 conjugation, which was attenuated by a deficiency of lasI-rhlI, genes associated with the generation of the quorum sensing signals N-acyl homoserine lactones (AHLs) in PAO1, or the deletion of the AHL receptor SdiA in SM10λπ. Subsequent mechanistic investigations revealed that a treatment with Gm repressed the mRNA expression of lasI and rhlI in PAO1 and upregulated traI expression in SM10λπ. Moreover, PAO1 treated with other quorum sensing (QS)-inhibiting antibiotics such as azithromycin or chloramphenicol also showed a conjugation-promoting ability. On the other hand, when using non-AHL-producing E. coli strain EC600 as the recipient cells, the promoting effect of Gm on conjugation could not be observed. These data suggest that AHL-SdiA contributes to the effectiveness of antibiotics on plasmid conjugation. Collectively, our findings highlight the HGT-promoting effect of antibiotics and suggest quorum sensing as a promising target for controlling antibiotic resistance dissemination. These findings have implications for assessing the risks of antibiotic use and developing advisable antibiotic treatment protocols. Copyright © 2017 American Society for Microbiology.

  11. Quorum sensing in group A Streptococcus

    Science.gov (United States)

    Jimenez, Juan Cristobal; Federle, Michael J.

    2014-01-01

    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

  12. Why Quorum Sensing Controls Private Goods

    Directory of Open Access Journals (Sweden)

    Martin Schuster

    2017-05-01

    Full Text Available Cell-cell communication, also termed quorum sensing (QS, is a widespread process that coordinates gene expression in bacterial populations. The generally accepted view is that QS optimizes the cell density-dependent benefit attained from cooperative behaviors, often in the form of secreted products referred to as “public goods.” This view is challenged by an increasing number of cell-associated products or “private goods” reported to be under QS-control for which a collective benefit is not apparent. A prominent example is nucleoside hydrolase from Pseudomonas aeruginosa, a periplasmic enzyme that catabolizes adenosine. Several recent studies have shown that private goods can function to stabilize cooperation by co-regulated public goods, seemingly explaining their control by QS. Here we argue that this property is a by-product of selection for other benefits rather than an adaptation. Emphasizing ecophysiological context, we propose alternative explanations for the QS control of private goods. We suggest that the benefit attained from private goods is associated with high cell density, either because a relevant ecological condition correlates with density, or because the private good is, directly or indirectly, involved in cooperative behavior. Our analysis helps guide a systems approach to QS, with implications for antivirulence drug design and synthetic biology.

  13. Differential Equations Models to Study Quorum Sensing.

    Science.gov (United States)

    Pérez-Velázquez, Judith; Hense, Burkhard A

    2018-01-01

    Mathematical models to study quorum sensing (QS) have become an important tool to explore all aspects of this type of bacterial communication. A wide spectrum of mathematical tools and methods such as dynamical systems, stochastics, and spatial models can be employed. In this chapter, we focus on giving an overview of models consisting of differential equations (DE), which can be used to describe changing quantities, for example, the dynamics of one or more signaling molecule in time and space, often in conjunction with bacterial growth dynamics. The chapter is divided into two sections: ordinary differential equations (ODE) and partial differential equations (PDE) models of QS. Rates of change are represented mathematically by derivatives, i.e., in terms of DE. ODE models allow describing changes in one independent variable, for example, time. PDE models can be used to follow changes in more than one independent variable, for example, time and space. Both types of models often consist of systems (i.e., more than one equation) of equations, such as equations for bacterial growth and autoinducer concentration dynamics. Almost from the onset, mathematical modeling of QS using differential equations has been an interdisciplinary endeavor and many of the works we revised here will be placed into their biological context.

  14. Recent progresses on AI-2 bacterial quorum sensing inhibitors.

    Science.gov (United States)

    Zhu, Peng; Li, Minyong

    2012-01-01

    Quorum sensing (QS) is a communication procedure that predominates gene expression in response to cell density and fluctuations in the neighboring environment as a result of discerning molecules termed autoinducers (AIs). It has been embroiled that QS can govern bacterial behaviors such as the secretion of virulence factors, biofilm formation, bioluminescence production, conjugation, sporulation and swarming motility. Autoinducer 2 (AI-2), a QS signaling molecule brought up to be involved in interspecies communication, exists in both gram-negative and -positive bacteria. Therefore, novel approaches to interrupt AI-2 quorum sensing are being recognized as next generation antimicrobials. In the present review article, we summarized recent progresses on AI-2 bacterial quorum sensing inhibitors and discussed their potential as the antibacterial agents.

  15. Silencing Quorum Sensing through Extracts of Melicope lunu-ankenda

    Directory of Open Access Journals (Sweden)

    Kok-Gan Chan

    2012-03-01

    Full Text Available Quorum sensing regulates bacterial virulence determinants, therefore making it an interesting target to attenuate pathogens. In this work, we screened edible, endemic plants in Malaysia for anti-quorum sensing properties. Extracts from Melicope lunu-ankenda (Gaertn. T. G. Hartley, a Malay garden salad, inhibited response of Chromobacterium violaceum CV026 to N-hexanoylhomoserine lactone, thus interfering with violacein production; reduced bioluminescence expression of E. coli [pSB401], disrupted pyocyanin synthesis, swarming motility and expression of lecA::lux of Pseudomonas aeruginosa PAO1. Although the chemical nature of the anti-QS compounds from M. lunu-ankenda is currently unknown, this study proves that endemic Malaysian plants could serve as leads in the search for anti-quorum sensing compounds.

  16. A novel recombinant bivalent outer membrane protein of Vibrio vulnificus and Aeromonas hydrophila as a vaccine antigen of American eel (Anguilla rostrata).

    Science.gov (United States)

    SongLin, Guo; PanPan, Lu; JianJun, Feng; JinPing, Zhao; Peng, Lin; LiHua, Duan

    2015-04-01

    The immogenicity of a novel vaccine antigen was evaluated after immunized American eels (Anguilla rostrata) with a recombinant bivalent expressed outer membrane protein (OMP) of Vibrio vulnificus and Aeromonas hydrophila. Three groups of eels were intraperitoneal (i.p) injected with phosphate-buffered saline (PBS group), formaline-killed-whole-cell (FKC) of A. hydrophila and V. vulnificus (FKC group) or the bivalent OMP (OMP group). On 14, 21, 28 and 42 days post-vaccination respectively, proliferation of the whole blood cells, titers of specific antibody and lysozyme activities of experimental eels were detected. On 28 day post-vaccination, eels from three groups were challenged by i.p injection of live A. hydrophila or V. vulnificus. The results showed that, compared with the PBS group, proliferation of whole blood cells in OMP group was significant enhanced on 28 days, and the serum titers of anti-A.hydrophila and anti-V. vulnificus antibody in eels of FKC and OMP group were significant increased on 14, 21 and 28d. Lysozyme Activities in serum, skin mucus, liver and kidney were significant changed between the three groups. Relative Percent Survival (RPS) after challenged A. hydrophila in KFC vs. PBS group and OMP vs. PBS group were 62.5% and 50% respectively, and the RPS challenged V. vulnificus in FKC and OMP vs. PBS group were 37.5% and 50% respectively. These results suggest that American eels immunized with the bivalent OMP would positively affect specific as well as non-specific immune parameters and protect against infection by the two pathogens in fresh water farming. Copyright © 2015 Elsevier Ltd. All rights reserved.

  17. Biomimicry of quorum sensing using bacterial lifecycle model.

    Science.gov (United States)

    Niu, Ben; Wang, Hong; Duan, Qiqi; Li, Li

    2013-01-01

    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. 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. 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

  18. Modeling quorum sensing trade-offs between bacterial cell density and system extension from open boundaries

    Science.gov (United States)

    Marenda, Mattia; Zanardo, Marina; Trovato, Antonio; Seno, Flavio; Squartini, Andrea

    2016-12-01

    Bacterial communities undergo collective behavioural switches upon producing and sensing diffusible signal molecules; a mechanism referred to as Quorum Sensing (QS). Exemplarily, biofilm organic matrices are built concertedly by bacteria in several environments. QS scope in bacterial ecology has been debated for over 20 years. Different perspectives counterpose the role of density reporter for populations to that of local environment diffusivity probe for individual cells. Here we devise a model system where tubes of different heights contain matrix-embedded producers and sensors. These tubes allow non-limiting signal diffusion from one open end, thereby showing that population spatial extension away from an open boundary can be a main critical factor in QS. Experimental data, successfully recapitulated by a comprehensive mathematical model, demonstrate how tube height can overtake the role of producer density in triggering sensor activation. The biotic degradation of the signal is found to play a major role and to be species-specific and entirely feedback-independent.

  19. Modeling quorum sensing trade-offs between bacterial cell density and system extension from open boundaries.

    Science.gov (United States)

    Marenda, Mattia; Zanardo, Marina; Trovato, Antonio; Seno, Flavio; Squartini, Andrea

    2016-12-14

    Bacterial communities undergo collective behavioural switches upon producing and sensing diffusible signal molecules; a mechanism referred to as Quorum Sensing (QS). Exemplarily, biofilm organic matrices are built concertedly by bacteria in several environments. QS scope in bacterial ecology has been debated for over 20 years. Different perspectives counterpose the role of density reporter for populations to that of local environment diffusivity probe for individual cells. Here we devise a model system where tubes of different heights contain matrix-embedded producers and sensors. These tubes allow non-limiting signal diffusion from one open end, thereby showing that population spatial extension away from an open boundary can be a main critical factor in QS. Experimental data, successfully recapitulated by a comprehensive mathematical model, demonstrate how tube height can overtake the role of producer density in triggering sensor activation. The biotic degradation of the signal is found to play a major role and to be species-specific and entirely feedback-independent.

  20. Degradation of Bacterial Quorum Sensing Signaling Molecules by the Microscopic Yeast Trichosporon loubieri Isolated from Tropical Wetland Waters

    Science.gov (United States)

    Wong, Cheng-Siang; Koh, Chong-Lek; Sam, Choon-Kook; Chen, Jian Woon; Chong, Yee Meng; Yin, Wai-Fong; Chan, Kok-Gan

    2013-01-01

    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

  1. Surface polysaccharides and quorum sensing are involved in the attachment and survival of Xanthomonas albilineans on sugarcane leaves.

    Science.gov (United States)

    Mensi, Imene; Daugrois, Jean-Heinrich; Pieretti, Isabelle; Gargani, Daniel; Fleites, Laura A; Noell, Julie; Bonnot, Francois; Gabriel, Dean W; Rott, Philippe

    2016-02-01

    Xanthomonas albilineans, the causal agent of sugarcane leaf scald, is a bacterial plant pathogen that is mainly spread by infected cuttings and contaminated harvesting tools. However, some strains of this pathogen are known to be spread by aerial means and are able to colonize the phyllosphere of sugarcane before entering the host plant and causing disease. The objective of this study was to identify the molecular factors involved in the survival or growth of X. albilineans on sugarcane leaves. We developed a bioassay to test for the attachment of X. albilineans on sugarcane leaves using tissue-cultured plantlets grown in vitro. Six mutants of strain XaFL07-1 affected in surface polysaccharide production completely lost their capacity to survive on the sugarcane leaf surface. These mutants produced more biofilm in vitro and accumulated more cellular poly-β-hydroxybutyrate than the wild-type strain. A mutant affected in the production of small molecules (including potential biosurfactants) synthesized by non-ribosomal peptide synthetases (NRPSs) attached to the sugarcane leaves as well as the wild-type strain. Surprisingly, the attachment of bacteria on sugarcane leaves varied among mutants of the rpf gene cluster involved in bacterial quorum sensing. Therefore, quorum sensing may affect polysaccharide production, or both polysaccharides and quorum sensing may be involved in the survival or growth of X. albilineans on sugarcane leaves. © 2015 BSPP AND JOHN WILEY & SONS LTD.

  2. Solution structure and dynamics of C-terminal regulatory domain of Vibrio vulnificus extracellular metalloprotease

    Energy Technology Data Exchange (ETDEWEB)

    Yun, Ji-Hye; Kim, Heeyoun [Department of Biochemistry, College of Life Science and Biotechnology, Yonsei University, Seoul 120-749 (Korea, Republic of); Park, Jung Eun [Department of Biotechnology, College of Natural Sciences, Chosun University, Gwangju 501-759 (Korea, Republic of); Lee, Jung Sup, E-mail: jsplee@mail.chosun.ac.kr [Department of Biotechnology, College of Natural Sciences, Chosun University, Gwangju 501-759 (Korea, Republic of); Lee, Weontae, E-mail: wlee@spin.yonsei.ac.kr [Department of Biochemistry, College of Life Science and Biotechnology, Yonsei University, Seoul 120-749 (Korea, Republic of)

    2013-01-11

    Highlights: Black-Right-Pointing-Pointer We have determined solution structures of vEP C-terminal regulatory domain. Black-Right-Pointing-Pointer vEP C-ter100 has a compact {beta}-barrel structure with eight anti-parallel {beta}-strands. Black-Right-Pointing-Pointer Solution structure of vEP C-ter100 shares its molecular topology with that of the collagen-binding domain of collagenase. Black-Right-Pointing-Pointer Residues in the {beta}3 region of vEP C-ter100 might be important in putative ligand/receptor binding. Black-Right-Pointing-Pointer vEP C-ter100 interacts strongly with iron ion. -- Abstract: An extracellular metalloprotease (vEP) secreted by Vibrio vulnificus ATCC29307 is a 45-kDa proteolytic enzyme that has prothrombin activation and fibrinolytic activities during bacterial infection. The action of vEP could result in clotting that could serve to protect the bacteria from the host defense machinery. Very recently, we showed that the C-terminal propeptide (C-ter100), which is unique to vEP, is involved in regulation of vEP activity. To understand the structural basis of this function of vEP C-ter100, we have determined the solution structure and backbone dynamics using multidimensional nuclear magnetic resonance spectroscopy. The solution structure shows that vEP C-ter100 is composed of eight anti-parallel {beta}-strands with a unique fold that has a compact {beta}-barrel formation which stabilized by hydrophobic and hydrogen bonding networks. Protein dynamics shows that the overall structure, including loops, is very rigid and stabilized. By structural database analysis, we found that vEP C-ter100 shares its topology with that of the collagen-binding domain of collagenase, despite low sequence homology between the two domains. Fluorescence assay reveals that vEP C-ter100 interacts strongly with iron (Fe{sup 3+}). These findings suggest that vEP protease might recruit substrate molecules, such as collagen, by binding at C-ter100 and that vEP participates

  3. AI-2 quorum-sensing inhibitors affect the starvation response and reduce virulence in several Vibrio species, most likely by interfering with LuxPQ.

    Science.gov (United States)

    Brackman, Gilles; Celen, Shari; Baruah, Kartik; Bossier, Peter; Van Calenbergh, Serge; Nelis, Hans J; Coenye, Tom

    2009-12-01

    The increase of disease outbreaks caused by Vibrio species in aquatic organisms as well as in humans, together with the emergence of antibiotic resistance in Vibrio species, has led to a growing interest in alternative disease control measures. Quorum sensing (QS) is a mechanism for regulating microbial gene expression in a cell density-dependent way. While there is good evidence for the involvement of auto-inducer 2 (AI-2)-based interspecies QS in the control of virulence in multiple Vibrio species, only few inhibitors of this system are known. From the screening of a small panel of nucleoside analogues for their ability to disturb AI-2-based QS, an adenosine derivative with a p-methoxyphenylpropionamide moiety at C-3' emerged as a promising hit. Its mechanism of inhibition was elucidated by measuring the effect on bioluminescence in a series of Vibrio harveyi AI-2 QS mutants. Our results indicate that this compound, as well as a truncated analogue lacking the adenine base, block AI-2-based QS without interfering with bacterial growth. The active compounds affected neither the bioluminescence system as such nor the production of AI-2, but most likely interfered with the signal transduction pathway at the level of LuxPQ in V. harveyi. The most active nucleoside analogue (designated LMC-21) was found to reduce the Vibrio species starvation response, to affect biofilm formation in Vibrio anguillarum, Vibrio vulnificus and Vibrio cholerae, to reduce pigment and protease production in V. anguillarum, and to protect gnotobiotic Artemia from V. harveyi-induced mortality.

  4. Mechanisms of quorum sensing and strategies for quorum sensing disruption in aquaculture pathogens.

    Science.gov (United States)

    Zhao, J; Chen, M; Quan, C S; Fan, S D

    2015-09-01

    In many countries, infectious diseases are a considerable threat to aquaculture. The pathogenicity of micro-organisms that infect aquaculture systems is closely related to the release of virulence factors and the formation of biofilms, both of which are regulated by quorum sensing (QS). Thus, QS disruption is a potential strategy for preventing disease in aquaculture systems. QS inhibitors (QSIs) not only inhibit the expression of virulence-associated genes but also attenuate the virulence of aquaculture pathogens. In this review, we discuss QS systems in important aquaculture pathogens and focus on the relationship between QS mechanisms and bacterial virulence in aquaculture. We further elucidate QS disruption strategies for targeting aquaculture pathogens. Four main types of QSIs that target aquaculture pathogens are discussed based on their mechanisms of action. © 2014 John Wiley & Sons Ltd.

  5. Autoinducer-2 Quorum Sensing Influences Viability of Escherichia coli O157:H7 under Osmotic and In Vitro Gastrointestinal Stress Conditions

    Directory of Open Access Journals (Sweden)

    Hyunjoon Park

    2017-06-01

    Full Text Available Bacteria use autoinducer molecules to communicate both at intra-species and inter-species levels by quorum sensing. One such cell density-dependent signaling system is the luxS-mediated universal quorum sensing using autoinducer-2 (AI-2. Virulence of several pathogens is determined by an AI-2 system and is related to colonization and infection of the host. From this concept, numerous papers have suggested that AI-2 inhibition is an important strategy toward designing of new antimicrobial agents. However, recent studies indicate that the AI-2 system is also involved in adaptation and survival under environmental stress conditions. Therefore, we hypothesized that interaction between quorum sensing and environmental conditions may be critical in influencing predicted results in a control and when combating of target pathogens. We investigated the growth of enterohemorrhagic Escherichia coli O157:H7 (EHEC and its luxS-deficient (non AI-2 producing mutant strain under various stress conditions, and found significant differences in the growth rate under osmotic stress. Moreover, we could also show the impact of the AI-2 molecule on viability in the gastrointestinal tract model representing a complex environmental condition. Differences in vital responses of the strains suggest that AI-2 quorum sensing has a significant influence on the viability of EHEC under environmental stress conditions.

  6. Quorum quenching bacteria can be used to inhibit the biofouling of reverse osmosis membranes.

    Science.gov (United States)

    Oh, Hyun-Suk; Tan, Chuan Hao; Low, Jiun Hui; Rzechowicz, Miles; Siddiqui, Muhammad Faisal; Winters, Harvey; Kjelleberg, Staffan; Fane, Anthony G; Rice, Scott A

    2017-04-01

    Over the last few decades, significant efforts have concentrated on mitigating biofouling in reverse osmosis (RO) systems, with a focus on non-toxic and sustainable strategies. Here, we explored the potential of applying quorum quenching (QQ) bacteria to control biofouling in a laboratory-scale RO system. For these experiments, Pantoea stewartii was used as a model biofilm forming organism because it was previously shown to be a relevant wastewater isolate that also forms biofilms in a quorum sensing (QS) dependent fashion. A recombinant Escherichia coli strain, which can produce a QQ enzyme, was first tested in batch biofilm assays and significantly reduced biofilm formation by P. stewartii. Subsequently, RO membranes were fouled with P. stewartii and the QQ bacterium was introduced into the RO system using two different strategies, direct injection and immobilization within a cartridge microfilter. When the QQ bacterial cells were directly injected into the system, N-acylhomoserine lactone signals were degraded, resulting in the reduction of biofouling. Similarly, the QQ bacteria controlled biofouling when immobilized within a microfilter placed downstream of the RO module to remove QS signals circulating in the system. These results demonstrate the proof-of-principle that QQ can be applied to control biofouling of RO membranes and may be applicable for use in full-scale plants. Copyright © 2017 Elsevier Ltd. All rights reserved.

  7. Biosensing systems for the detection of bacterial quorum signaling molecules.

    Science.gov (United States)

    Kumari, Anjali; Pasini, Patrizia; Deo, Sapna K; Flomenhoft, Deborah; Shashidhar, Harohalli; Daunert, Sylvia

    2006-11-15

    Bacterial quorum sensing (QS) is a cell-to-cell communication phenomenon that allows bacteria to control the expression of certain specialized genes depending on their cell population size. Signaling molecules such N-acylhomoserine lactones (AHLs) mediate the communication, and their concentration reflects the bacterial population density. Quorum sensing regulates several processes including bacterial pathogenicity. We developed a method for the rapid, sensitive, and quantitative detection of AHLs in biological samples such as saliva and stools. The method is based on whole-cell sensing systems that employ QS regulatory systems as recognition elements and the luxCDABE gene cassette as a reporter. The method proved to be reproducible when applied to real samples and was able to detect low analyte concentrations down to 1 x 10(-9) M without requiring extensive sample preparation. We envision that this novel biosensing system could be employed in the diagnosis and management of various bacteria-related disorders, thus supporting the use of quorum sensing molecules as potential biomarkers of disease. Due to cost-effectiveness and high throughput, these biosensing systems could be successfully employed as a new tool for the screening of novel drugs that target quorum sensing mechanisms.

  8. Quorum sensing-controlled gene expression in lactic acid bacteria

    NARCIS (Netherlands)

    Kuipers, Oscar P.; Ruyter, Pascalle G.G.A. de; Kleerebezem, Michiel; Vos, Willem M. de

    1998-01-01

    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

  9. Deciphering Physiological Functions of AHL Quorum Quenching Acylases

    NARCIS (Netherlands)

    Utari, Putri D.; Vogel, Jan; Quax, Wim J.

    2017-01-01

    N-Acylhomoserine lactone (AHL)-acylase (also known as amidase or amidohydrolase) is a class of enzyme that belongs to the Ntn-hydrolase superfamily. As the name implies, AHL-acylases are capable of hydrolysing AHLs, the most studied signaling molecules for quorum sensing in Gram-negative bacteria.

  10. Attenuation of Pseudomonas aeruginosa virulence by quorum sensing inhibitors

    DEFF Research Database (Denmark)

    Hentzer, Morten; Wu, H.; Andersen, Jens Bo

    2003-01-01

    Traditional treatment of infectious diseases is based on compounds that kill or inhibit growth of bacteria. A major concern with this approach is the frequent development of resistance to antibiotics. The discovery of communication systems (quorum sensing systems) regulating bacterial virulence has...

  11. Quorum-quenching : role in nature and applied developments

    Science.gov (United States)

    Quorum sensing (QS) refers to the capacity of bacteria to monitor their population density and regulate gene expression accordingly: the QS-regulated processes deal with multicellular behaviors (e.g. growth and development of biofilm), horizontal gene transfer and host–microbe (symbiosis and pathoge...

  12. Impact of quorum sensing on the quality of fermented foods

    DEFF Research Database (Denmark)

    Johansen, Pernille; Jespersen, Lene

    2017-01-01

    The quality of fermented food highly dependents on the microorganisms involved, their metabolic activities and interactions. Recently, focus has been on quorum sensing (QS) being a cell density-dependent mechanism allowing adaptive responses. Specific QS molecules in prokaryotes and eukaryotes...

  13. Detection of quorum sensing molecules from Vibrio harveyi and use ...

    African Journals Online (AJOL)

    This paper explores the extraction and detection processes of quorum sensing molecules such as N-aceyl homoserine lactone compounds (AHL) from marine Vibrio harveyi. The spent culture of V. harveyi was solvent partitioned for AHL, rotary evaporated and re-suspended in 50% acetonitrile then detected with reporter ...

  14. Controlling the activity of quorum sensing autoinducers with light

    NARCIS (Netherlands)

    Van der Berg, J. P.; Velema, W. A.; Szymanski, W.; Driessen, A. J. M.; Feringa, B. L.

    2015-01-01

    Bacteria use a communication system, called quorum sensing (QS), to organize into communities and synchronize gene expression to promote virulence and secure survival. Here we report on a proof-of-principle for externally interfering with this bacterial communication system, using light. By

  15. Bacterial gangs: United and strong by means of quorum sensing

    DEFF Research Database (Denmark)

    Kuipers, Oscar P.; Kovács, Ákos T.

    2017-01-01

    Microorganisms can effectively communicate with each other. They share information about their community size (quorum), and thereby their nutrient requirement, then take appropriate action such as moving away. They use signalling molecules to coordinate their behaviour. These compounds, like simi...... similar molecules in humans, are called pheromones....

  16. Quorum decision-making facilitates information transfer in fish shoals.

    Science.gov (United States)

    Ward, Ashley J W; Sumpter, David J T; Couzin, Iain D; Hart, Paul J B; Krause, Jens

    2008-05-13

    Despite the growing interest in collective phenomena such as "swarm intelligence" and "wisdom of the crowds," little is known about the mechanisms underlying decision-making in vertebrate animal groups. How do animals use the behavior of others to make more accurate decisions, especially when it is not possible to identify which individuals possess pertinent information? One plausible answer is that individuals respond only when they see a threshold number of individuals perform a particular behavior. Here, we investigate the role of such "quorum responses" in the movement decisions of fish (three-spine stickleback, Gasterosteus aculeatus). We show that a quorum response to conspecifics can explain how sticklebacks make collective movement decisions, both in the absence and presence of a potential predation risk. Importantly our experimental work shows that a quorum response can reduce the likelihood of amplification of nonadaptive following behavior. Whereas the traveling direction of solitary fish was strongly influenced by a single replica conspecific, the replica was largely ignored by larger groups of four or eight sticklebacks under risk, and the addition of a second replica was required to exert influence on the movement decisions of such groups. Model simulations further predict that quorum responses by fish improve the accuracy and speed of their decision-making over that of independent decision-makers or those using a weak linear response. This study shows that effective and accurate information transfer in groups may be gained only through nonlinear responses of group members to each other, thus highlighting the importance of quorum decision-making.

  17. Quorum-sensing-directed protein expression in Serratia proteamaculans B5a

    DEFF Research Database (Denmark)

    Christensen, Allan Beck; Riedel, Kathrin; Eberl, Leo

    2003-01-01

    marcescens. Proteome analysis suggested that the presence of at least 39 intracellular proteins was affected by the 3-oxo-C6-HSL-based quorum sensing system. The lipB-encoded secretion system was identified as one target gene of the quorum sensing system. LipB was required for the production of extracellular...... lipolytic and proteolytic activities, thus rendering the production of food-deterioration-relevant exoenzymes indirectly under the control of quorum sensing. Strain B5a caused quorum-sensing-controlled spoilage of milk. Furthermore, chitinolytic activity was controlled by quorum sensing. This control...... appeared to be direct and not mediated via LipB. The data presented here demonstrate that quorum-sensing-controlled exoenzymic activities affect food quality....

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2010-03-29

    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

  19. Portrait of a viral infection: The infection cycle of Vibrio vulnificus phage VvAW1 visualized through plaque assay, electron microscopy, and proteomics

    Science.gov (United States)

    Clah, K. E. Y.; Nigro, O. D.; Miranda, J.; Schvarcz, C.; Culley, A.; Saito, M. A.; Steward, G.

    2016-02-01

    The bacterium Vibrio vulnificus is an opportunistic human pathogen that thrives in warm brackish waters. Viral infection is one of several mechanisms influencing the population dynamics of this bacterium in the natural environment. V. vulnificus-specific viruses have been isolated; however, the details of their infection cycle have not been reported. As a result, our current understanding of the interaction between the bacterium and its viruses in the environment is limited. To better understand the infection process, a strain of V. vulnificus (V93D1V) and its bacteriophage, Vibrio phage VvAW1, were isolated from the estuarine waters of the Ala Wai Canal, HI. A time-series infection experiment was conducted with the virus-host pair in which samples were collected every ten minutes for eighty minutes post-infection for analysis by plaque assay, electron microscopy, and proteomics. Using electron microscopy, visibly infected bacteria were observed forty minutes after the introduction of the virus, signaling the end of the eclipse period. The peak of infection occurred at seventy minutes with an average viral load of 78 viruses per bacterium. The percentage of visibly infected bacteria reached a maximum just prior to a rise in free viruses in the culture, indicating the end of the latent period. The percentage of infected cells that lysed was low and there was little effect on the bacterial population growth rate. Analysis of the proteome revealed that protein expression patterns, in particular capsid and other structural proteins, closely follow the timing of the observed infection cycle. Together, these analyses provided the first detailed view of a viral infection in a highly lethal aquatic bacterium. The apparent temperate nature of this virus suggests that it can be a source of mortality to V. vulnificus, but has evolved to avoid total destruction of its host by complete lysis, a characteristic that helps ensure its replication in subsequent generations.

  20. Impact of Hurricane Irene on Vibrio vulnificus and Vibrio parahaemolyticus concentrations in surface water, sediment, and cultured oysters in the Chesapeake Bay, MD, USA.

    Science.gov (United States)

    Shaw, Kristi S; Jacobs, John M; Crump, Byron C

    2014-01-01

    To determine if a storm event (i.e., high winds, large volumes of precipitation) could alter concentrations of Vibrio vulnificus and V. parahaemolyticus in aquacultured oysters (Crassostrea virginica) and associated surface water and sediment, this study followed a sampling timeline before and after Hurricane Irene impacted the Chesapeake Bay estuary in late August 2011. Aquacultured oysters were sampled from two levels in the water column: surface (0.3 m) and near-bottom (just above the sediment). Concentrations of each Vibrio spp. and associated virulence genes were measured in oysters with a combination of real-time PCR and most probable number (MPN) enrichment methods, and in sediment and surface water with real-time PCR. While concentration shifts of each Vibrio species were apparent post-storm, statistical tests indicated no significant change in concentration for either Vibrio species by location (surface or near bottom oysters) or date sampled (oyster tissue, surface water, and sediment concentrations). V. vulnificus in oyster tissue was correlated with total suspended solids (r = 0.41, P = 0.04), and V. vulnificus in sediment was correlated with secchi depth (r = -0.93, P depth [r = -0.48, P = 0.02 (sediment); r = -0.97, P <0.01 (surface water)] and tidal height [r = -0.96, P <0.01 (sediment), r = -0.59, P <0.01 (surface water)]. The concentrations of Vibrio spp. were higher in oysters relative to other studies (average V. vulnificus 4 × 10(5) MPN g(-1), V. parahaemolyticus 1 × 10(5) MPN g(-1)), and virulence-associated genes were detected in most oyster samples. This study provides a first estimate of storm-related Vibrio density changes in oyster tissues, sediment, and surface water at an aquaculture facility in the Chesapeake Bay.

  1. Signal Integration in Quorum Sensing Enables Cross-Species Induction of Virulence in Pectobacterium wasabiae

    Directory of Open Access Journals (Sweden)

    Rita S. Valente

    2017-05-01

    Full Text Available Bacterial communities can sense their neighbors, regulating group behaviors in response to cell density and environmental changes. The diversity of signaling networks in a single species has been postulated to allow custom responses to different stimuli; however, little is known about how multiple signals are integrated and the implications of this integration in different ecological contexts. In the plant pathogen Pectobacterium wasabiae (formerly Erwinia carotovora, two signaling networks—the N-acyl homoserine lactone (AHL quorum-sensing system and the Gac/Rsm signal transduction pathway—control the expression of secreted plant cell wall-degrading enzymes, its major virulence determinants. We show that the AHL system controls the Gac/Rsm system by affecting the expression of the regulatory RNA RsmB. This regulation is mediated by ExpR2, the quorum-sensing receptor that responds to the P. wasabiae cognate AHL but also to AHLs produced by other bacterial species. As a consequence, this level of regulation allows P. wasabiae to bypass the Gac-dependent regulation of RsmB in the presence of exogenous AHLs or AHL-producing bacteria. We provide in vivo evidence that this pivotal role of RsmB in signal transduction is important for the ability of P. wasabiae to induce virulence in response to other AHL-producing bacteria in multispecies plant lesions. Our results suggest that the signaling architecture in P. wasabiae was coopted to prime the bacteria to eavesdrop on other bacteria and quickly join the efforts of other species, which are already exploiting host resources.

  2. Specific quorum sensing-disrupting activity (AQSI) of thiophenones and their therapeutic potential

    Science.gov (United States)

    Yang, Qian; Aamdal Scheie, Anne; Benneche, Tore; Defoirdt, Tom

    2015-01-01

    Disease caused by antibiotic resistant pathogens is becoming a serious problem, both in human and veterinary medicine. The inhibition of quorum sensing, bacterial cell-to-cell communication, is a promising alternative strategy to control disease. In this study, we determined the quorum sensing-disrupting activity of 20 thiophenones towards the quorum sensing model bacterium V. harveyi. In order to exclude false positives, we propose a new parameter (AQSI) to describe specific quorum sensing activity. AQSI is defined as the ratio between inhibition of quorum sensing-regulated activity in a reporter strain and inhibition of the same activity when it is independent of quorum sensing. Calculation of AQSI allowed to exclude five false positives, whereas the six most active thiophenones (TF203, TF307, TF319, TF339, TF342 and TF403) inhibited quorum sensing at 0.25 μM, with AQSI higher than 10. Further, we determined the protective effect and toxicity of the thiophenones in a highly controlled gnotobiotic model system with brine shrimp larvae. There was a strong positive correlation between the specific quorum sensing-disrupting activity of the thiophenones and the protection of brine shrimp larvae against pathogenic V. harveyi. Four of the most active quorum sensing-disrupting thiophenones (TF 203, TF319, TF339 and TF342) were considered to be promising since they have a therapeutic potential of at least 10. PMID:26647822

  3. Anti-quorum sensing potential of crude Kigelia africana fruit extracts

    National Research Council Canada - National Science Library

    Chenia, Hafizah Y

    2013-01-01

    .... 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...

  4. Inter-kingdom signaling by the Legionella Quorum Sensing Molecule LAI-1 modulates cell migration through an IQGAP1-Cdc42-ARHGEF9-dependent pathway

    OpenAIRE

    Sylvia Simon; Ursula Schell; Natalie Heuer; Dominik Hager; Albers, Michael F.; Jan Matthias; Felix Fahrnbauer; Dirk Trauner; Ludwig Eichinger; Christian Hedberg; Hubert Hilbi

    2015-01-01

    Small molecule signaling promotes the communication between bacteria as well as between bacteria and eukaryotes. The opportunistic pathogenic bacterium Legionella pneumophila employs LAI-1 (3-hydroxypentadecane-4-one) for bacterial cell-cell communication. LAI-1 is produced and detected by the Lqs (Legionella quorum sensing) system, which regulates a variety of processes including natural competence for DNA uptake and pathogen-host cell interactions. In this study, we analyze the role of LAI-...

  5. 6-Gingerol reduces Pseudomonas aeruginosa biofilm formation and virulence via quorum sensing inhibition.

    Science.gov (United States)

    Kim, Han-Shin; Lee, Sang-Hoon; Byun, Youngjoo; Park, Hee-Deung

    2015-03-02

    Pseudomonas aeruginosa is a well-known pathogenic bacterium that forms biofilms and produces virulence factors via quorum sensing (QS). Interfering with normal QS interactions between signal molecules and their cognate receptors is a developing strategy for attenuating its virulence. Here we tested the hypothesis that 6-gingerol, a pungent oil of fresh ginger, reduces biofilm formation and virulence by antagonistically binding to P. aeruginosa QS receptors. In silico studies demonstrated molecular binding occurs between 6-gingerol and the QS receptor LasR through hydrogen bonding and hydrophobic interactions. Experimentally 6-gingerol reduced biofilm formation, several virulence factors (e.g., exoprotease, rhamnolipid, and pyocyanin), and mice mortality. Further transcriptome analyses demonstrated that 6-gingerol successfully repressed QS-induced genes, specifically those related to the production of virulence factors. These results strongly support our hypothesis and offer insight into the molecular mechanism that caused QS gene repression.

  6. Attenuation of Pseudomonas aeruginosa virulence by quorum sensing inhibitors

    DEFF Research Database (Denmark)

    Hentzer, Morten; Wu, Hong; Andersen, Jens Bo

    2003-01-01

    Traditional treatment of infectious diseases is based on compounds that kill or inhibit growth of bacteria. A major concern with this approach is the frequent development of resistance to antibiotics. The discovery of communication systems (quorum sensing systems) regulating bacterial virulence has...... afforded a novel opportunity to control infectious bacteria without interfering with growth. Compounds that can override communication signals have been found in the marine environment. Using Pseudomonas aeruginosa PAO1 as an example of an opportunistic human pathogen, we show that a synthetic derivate...... and inhibited virulence factor expression. Application of the drug to P.aeruginosa biofilms increased bacterial susceptibility to tobramycin and SDS. In a mouse pulmonary infection model, the drug inhibited quorum sensing of the infecting bacteria and promoted their clearance by the mouse immune response....

  7. Design, Synthesis and Biological Evaluation of Quorum Sensing Modulators

    DEFF Research Database (Denmark)

    Hansen, Mette Reimert

    of virulence factors. The system is driven by small signaling molecules, usually N-acylated homoserine lactones (AHLs). In the search for new treatment methods for biofilm infections the quorum sensing system has emerged as an attractive target. Recent advances in this area have proved that it is possible...... to intercept the communication system by synthetic non-native ligands and thereby lower the pathogenesis and antibiotic tolerance of a bacterial biofilm. To identify new ligands with quorum sensing modulating activities, three types of AHL analogs were synthesized using different synthetic strategies...... a solid-phase strategy. Another library in which the amide bond was replaced with a triazole unit was synthesized by means of the copper- and ruthenium-catalyzed azide-alkyne cycloadditions. Finally, the synthesis of compounds with biaryl functionalities in the position of the acyl chain was carried out...

  8. N-Acyl Homoserine Lactone-Mediated Quorum Sensing with Special Reference to Use of Quorum Quenching Bacteria in Membrane Biofouling Control

    Science.gov (United States)

    Paul, Diby

    2014-01-01

    Membrane biofouling remains a severe problem to be addressed in wastewater treatment systems affecting reactor performance and economy. The finding that many wastewater bacteria rely on N-acyl homoserine lactone-mediated quorum sensing to synchronize their activities essential for biofilm formations; the quenching bacterial quorum sensing suggests a promising approach for control of membrane biofouling. A variety of quorum quenching compounds of both synthetic and natural origin have been identified and found effective in inhibition of membrane biofouling with much less environmental impact than traditional antimicrobials. Work over the past few years has demonstrated that enzymatic quorum quenching mechanisms are widely conserved in several prokaryotic organisms and can be utilized as a potent tool for inhibition of membrane biofouling. Such naturally occurring bacterial quorum quenching mechanisms also play important roles in microbe-microbe interactions and have been used to develop sustainable nonantibiotic antifouling strategies. Advances in membrane fabrication and bacteria entrapment techniques have allowed the implication of such quorum quenching bacteria for better design of membrane bioreactor with improved antibiofouling efficacies. In view of this, the present paper is designed to review and discuss the recent developments in control of membrane biofouling with special emphasis on quorum quenching bacteria that are applied in membrane bioreactors. PMID:25147787

  9. Switch of SpnR function from activating to inhibiting quorum sensing by its exogenous addition

    Energy Technology Data Exchange (ETDEWEB)

    Takayama, Yuriko [Department of Innovation Systems Engineering, Graduate School of Engineering, Utsunomiya University, 7-1-2 Yoto, Utsunomiya, Tochigi 321-8585 (Japan); CREST, Japan Science and Technology Agency, 7-1-2 Yoto, Utsunomiya, Tochigi 321-8585 (Japan); Kato, Norihiro, E-mail: katon@cc.utsunomiya-u.ac.jp [CREST, Japan Science and Technology Agency, 7-1-2 Yoto, Utsunomiya, Tochigi 321-8585 (Japan); Department of Material and Environmental Chemistry, Graduate School of Engineering, Utsunomiya University, 7-1-2 Yoto, Utsunomiya, Tochigi 321-8585 (Japan)

    2016-09-02

    The opportunistic human pathogen Serratia marcescens AS-1 produces the N-hexanoylhomoserine lactone (C6HSL) receptor SpnR, a homologue of LuxR from Vibrio fischeri, which activates pig clusters to produce the antibacterial prodigiosin. In this study, we attempted to artificially regulate quorum sensing (QS) by changing the role of SpnR in N-acylhomoserine lactone (AHL)-mediated QS. SpnR was obtained as a fusion protein tagged with maltose-binding protein (MBP) from overexpression in Escherichia coli, and its specific affinity to C6HSL was demonstrated by quartz crystal microbalance analysis and AHL-bioassay with Chromobacterium violaceum CV026. Prodigiosin production was effectively inhibited by externally added MBP-SpnR in both wild-type AS-1 and the AHL synthase-defective mutant AS-1(ΔspnI). For the mutant, the induced amount of prodigiosin was drastically reduced to approximately 4% with the addition of 18 μM MBP-SpnR to the liquid medium, indicating 81% trapping of C6HSL. A system for inhibiting QS can be constructed by adding exogenous AHL receptor to the culture broth to keep the concentration of free AHL low, whereas intracellular SpnR naturally functions as the activator in response to QS. - Highlights: • Quorum sensing (QS) regulates the expression of some bacterial genes. • We added an AHL receptor to culture media to inhibit QS in Serratia marcescens AS-1. • The exogenous receptor effectively bound C6HSL and inhibited QS. • This approach can be used to artificially regulate AHL-mediated QS.

  10. Impact of Hurricane Irene on Vibrio vulnificus and Vibrio parahaemolyticus concentrations in surface water, sediment and cultured oysters in the Chesapeake Bay, Maryland, USA

    Directory of Open Access Journals (Sweden)

    Kristi S Shaw

    2014-05-01

    Full Text Available To determine if a storm event (i.e., high winds, large volumes of precipitation could alter concentrations of Vibrio vulnificus and Vibrio parahaemolyticus in aquacultured oysters (Crassostrea virginica and associated surface water and sediment, this study followed a sampling timeline before and after Hurricane Irene impacted the Chesapeake Bay estuary in late August 2011. Aquacultured oysters were sampled from two levels in the water column: surface 0.3 m and near-bottom just above the sediment. Concentrations of each Vibrio spp. and associated virulence genes were measured in oysters with a combination of real-time PCR and most probable number enrichment methods, and in sediment and surface water with real-time PCR. While concentration shifts of each Vibrio species were apparent post-storm, statistical tests indicated no significant change in concentration change for either Vibrio species by location (surface or near bottom oysters or date sampled (oyster tissue, surface water and sediment concentrations. V. vulnificus in oyster tissue was correlated with total suspended solids (r=0.41, p=0.04, and V. vulnificus in sediment was correlated with secchi depth (r=-0.93, p< 0.01, salinity (r=-0.46, p=0.02, tidal height (r=-0.45, p=0.03, and surface water V. vulnificus (r=0.98, p< 0.01. V. parahaemolyticus in oyster tissue did not correlate with environmental measurements, but V. parahaemolyticus in sediment and surface water correlated with several measurements including secchi depth (r=-0.48, p=0.02[sediment]; r=-0.97 p< 0.01[surface water] and tidal height (r=-0.96. p< 0.01[sediment], r=-0.59,p< 0.01 [surface water]. The concentrations of Vibrio spp. were higher in oysters relative to other studies (average V. vulnificus 4x105 MPN g-1, V. parahaemolyticus 1x105 MPN g-1, and virulence-associated genes were detected in most oyster samples. This study provides a first estimate of storm-related Vibrio density changes in oyster tissues, sediment and

  11. Stereochemical insignificance discovered in Acinetobacter baumannii quorum sensing.

    Directory of Open Access Journals (Sweden)

    Amanda L Garner

    Full Text Available 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.

  12. Quorum Quenching Mediated Approaches for Control of Membrane Biofouling

    Science.gov (United States)

    Lade, Harshad; Paul, Diby; Kweon, Ji Hyang

    2014-01-01

    Membrane biofouling is widely acknowledged as the most frequent adverse event in wastewater treatment systems resulting in significant loss of treatment efficiency and economy. Different strategies including physical cleaning and use of antimicrobial chemicals or antibiotics have been tried for reducing membrane biofouling. Such traditional practices are aimed to eradicate biofilms or kill the bacteria involved, but the greater efficacy in membrane performance would be achieved by inhibiting biofouling without interfering with bacterial growth. As a result, the search for environmental friendly non-antibiotic antifouling strategies has received much greater attention among scientific community. The use of quorum quenching natural compounds and enzymes will be a potential approach for control of membrane biofouling. This approach has previously proven useful in diseases and membrane biofouling control by triggering the expression of desired phenotypes. In view of this, the present review is provided to give the updated information on quorum quenching compounds and elucidate the significance of quorum sensing inhibition in control of membrane biofouling. PMID:24910534

  13. Dynorphin activates quorum sensing quinolone signaling in Pseudomonas aeruginosa.

    Directory of Open Access Journals (Sweden)

    Olga Zaborina

    2007-03-01

    Full Text Available There is now substantial evidence that compounds released during host stress directly activate the virulence of certain opportunistic pathogens. Here, we considered that endogenous opioids might function as such compounds, given that they are among the first signals to be released at multiple tissue sites during host stress. We tested the ability of various opioid compounds to enhance the virulence of Pseudomonas aeruginosa using pyocyanin production as a biological readout, and demonstrated enhanced virulence when P. aeruginosa was exposed to synthetic (U-50,488 and endogenous (dynorphin kappa-agonists. Using various mutants and reporter strains of P. aeruginosa, we identified involvement of key elements of the quorum sensing circuitry such as the global transcriptional regulator MvfR and the quorum sensing-related quinolone signaling molecules PQS, HHQ, and HQNO that respond to kappa-opioids. The in vivo significance of kappa-opioid signaling of P. aeruginosa was demonstrated in mice by showing that dynorphin is released from the intestinal mucosa following ischemia/reperfusion injury, activates quinolone signaling in P. aeruginosa, and enhances the virulence of P. aeruginosa against Lactobacillus spp. and Caenorhabditis elegans. Taken together, these data demonstrate that P. aeruginosa can intercept opioid compounds released during host stress and integrate them into core elements of quorum sensing circuitry leading to enhanced virulence.

  14. Quorum Sensing and the Use of Quorum Quenchers as Natural Biocides to Inhibit Sulfate-Reducing Bacteria

    KAUST Repository

    Scarascia, Giantommaso

    2016-12-15

    Sulfate-reducing bacteria (SRB) are one of the main protagonist groups of biocorrosion in the seawater environment. Given their principal role in biocorrosion, it remains a crucial task to develop strategies to reduce the abundance of SRBs. Conventional approaches include the use of biocides and antibiotics, which can impose health, safety, and environmental concerns. This review examines an alternative approach to this problem. This is achieved by reviewing the role of quorum sensing (QS) in SRB populations and its impact on the biofilm formation process. Genome databases of SRBs are mined to look for putative QS systems and homologous protein sequences representative of autoinducer receptors or synthases. Subsequently, this review puts forward the potential use of quorum quenchers as natural biocides against SRBs and outlines the potential strategies for the implementation of this approach.

  15. Quorum Sensing and the Use of Quorum Quenchers as Natural Biocides to Inhibit Sulfate-Reducing Bacteria

    Directory of Open Access Journals (Sweden)

    Giantommaso Scarascia

    2016-12-01

    Full Text Available Sulfate-reducing bacteria (SRB are one of the main protagonist groups of biocorrosion in the seawater environment. Given their principal role in biocorrosion, it remains a crucial task to develop strategies to reduce the abundance of SRBs. Conventional approaches include the use of biocides and antibiotics, which can impose health, safety, and environmental concerns. This review examines an alternative approach to this problem. This is achieved by reviewing the role of quorum sensing (QS in SRB populations and its impact on the biofilm formation process. Genome databases of SRBs are mined to look for putative QS systems and homologous protein sequences representative of autoinducer receptors or synthases. Subsequently, this review puts forward the potential use of quorum quenchers as natural biocides against SRBs and outlines the potential strategies for the implementation of this approach.

  16. Pseudomonas aeruginosa quorum-sensing response in the absence of functional LasR and LasI proteins: the case of strain 148, a virulent dolphin isolate.

    Science.gov (United States)

    Morales, Estefanía; González-Valdez, Abigail; Servín-González, Luis; Soberón-Chávez, Gloria

    2017-07-03

    Pseudomonas aeruginosa is an opportunistic pathogen that presents a complex regulatory network called 'quorum-sensing', which is responsible for the transcription of genes coding for several traits implicated in its pathogenicity. Strain 148 is a dolphin isolate that has been shown to produce quorum-sensing-regulated virulence traits and to be virulent in a mouse model, despite the fact that it contains a 20-kbp deletion that eliminates from the chromosome the lasR gene and the lasI promoter. LasR is a key quorum-sensing transcriptional regulator that, when coupled with the autoinducer 3-oxo-dodecanoyl homoserine lactone (3O-C12-HSL) produced by LasI, activates transcription of genes coding for some virulence-associated traits such as elastase, lasI, rhlI and rhlR. RhlR is also a key quorum-sensing transcriptional regulator that, when interacting with the autoinducer butanoyl homoserine lactone (C4-HSL) that is produced by the synthase RhlI, activates the genes involved in the synthesis of some virulence-associated traits, as rhamnolipids and pyocyanin. We describe that in P. aeruginosa 148, the LasR/3O-C12-HSL-independent rhlR transcriptional activation is due to the release of the negative effect of Vfr (a CRP-ortholog) caused by the insertion of an IS element in vfr, and that rhlI transcription is driven from the rhlR promoter, forming the rhlR-I operon. © FEMS 2017. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  17. Quorum Quenching of Nitrobacter winogradskyi Suggests that Quorum Sensing Regulates Fluxes of Nitrogen Oxide(s) during Nitrification

    OpenAIRE

    Brett L. Mellbye; Giguere, Andrew T.; Bottomley, Peter J.; Sayavedra-Soto, Luis A.

    2016-01-01

    ABSTRACT Quorum sensing (QS) is a widespread process in bacteria used to coordinate gene expression with cell density, diffusion dynamics, and spatial distribution through the production of diffusible chemical signals. To date, most studies on QS have focused on model bacteria that are amenable to genetic manipulation and capable of high growth rates, but many environmentally important bacteria have been overlooked. For example, representatives of proteobacteria that participate in nitrificat...

  18. A quorum-sensing-induced bacteriophage defense mechanism.

    Science.gov (United States)

    Høyland-Kroghsbo, Nina Molin; Maerkedahl, Rasmus Baadsgaard; Svenningsen, Sine Lo

    2013-02-19

    One of the key determinants of the size, composition, structure, and development of a microbial community is the predation pressure by bacteriophages. Accordingly, bacteria have evolved a battery of antiphage defense strategies. Since maintaining constantly elevated defenses is costly, we hypothesize that some bacteria have additionally evolved the abilities to estimate the risk of phage infection and to adjust their strategies accordingly. One risk parameter is the density of the bacterial population. Hence, quorum sensing, i.e., the ability to regulate gene expression according to population density, may be an important determinant of phage-host interactions. This hypothesis was investigated in the model system of Escherichia coli and phage λ. We found that, indeed, quorum sensing constitutes a significant, but so far overlooked, determinant of host susceptibility to phage attack. Specifically, E. coli reduces the numbers of λ receptors on the cell surface in response to N-acyl-l-homoserine lactone (AHL) quorum-sensing signals, causing a 2-fold reduction in the phage adsorption rate. The modest reduction in phage adsorption rate leads to a dramatic increase in the frequency of uninfected survivor cells after a potent attack by virulent phages. Notably, this mechanism may apply to a broader range of phages, as AHLs also reduce the risk of χ phage infection through a different receptor. IMPORTANCE To enable the successful manipulation of bacterial populations, a comprehensive understanding of the factors that naturally shape microbial communities is required. One of the key factors in this context is the interactions between bacteria and the most abundant biological entities on Earth, namely, the bacteriophages that prey on bacteria. This proof-of-principle study shows that quorum sensing plays an important role in determining the susceptibility of E. coli to infection by bacteriophages λ and χ. On the basis of our findings in the classical Escherichia coli

  19. Humans use social information to adjust their quorum thresholds adaptively in a simulated predator detection experiment

    NARCIS (Netherlands)

    Kurvers, R.H.J.M.; Wolf, M.; Krause, J.

    2014-01-01

    Quorum sensing is used in many biological systems to increase decision accuracy. In quorum sensing, the probability that an individual adopts a behavior is a nonlinear function of the number of other individuals adopting this behavior. From an optimal decision-making perspective, individuals should

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

    NARCIS (Netherlands)

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

    2014-01-01

    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

  1. Evaluation of Enoyl-Acyl Carrier Protein Reductase Inhibitors as Pseudomonas aeruginosa Quorum-Quenching Reagents

    Directory of Open Access Journals (Sweden)

    Søren Molin

    2010-02-01

    Full Text Available Pseudomonas aeruginosa is an opportunistic pathogen which is responsible for a wide range of infections. Production of virulence factors and biofilm formation by P. aeruginosa are partly regulated by cell-to-cell communication quorum-sensing systems. Identification of quorum-quenching reagents which block the quorum-sensing process can facilitate development of novel treatment strategies for P. aeruginosa infections. We have used molecular dynamics simulation and experimental studies to elucidate the efficiencies of two potential quorum-quenching reagents, triclosan and green tea epigallocatechin gallate (EGCG, which both function as inhibitors of the enoyl-acyl carrier protein (ACP reductase (ENR from the bacterial type II fatty acid synthesis pathway. Our studies suggest that EGCG has a higher binding affinity towards ENR of P. aeruginosa and is an efficient quorum-quenching reagent. EGCG treatment was further shown to be able to attenuate the production of virulence factors and biofilm formation of P. aeruginosa.

  2. Evaluation of Enoyl-Acyl Carrier Protein Reductase Inhibitors as Pseudomonas aeruginosa Quorum-Quenching Reagents

    DEFF Research Database (Denmark)

    Yang, Liang; Liu, Yang; Sternberg, Claus

    2010-01-01

    Pseudomonas aeruginosa is an opportunistic pathogen which is responsible for a wide range of infections. Production of virulence factors and biofilm formation by P. aeruginosa are partly regulated by cell-to-cell communication quorum-sensing systems. Identification of quorum-quenching reagents...... which block the quorum-sensing process can facilitate development of novel treatment strategies for P. aeruginosa infections. We have used molecular dynamics simulation and experimental studies to elucidate the efficiencies of two potential quorum-quenching reagents, triclosan and green tea...... epigallocatechin gallate (EGCG), which both function as inhibitors of the enoyl-acyl carrier protein (ACP) reductase (ENR) from the bacterial type II fatty acid synthesis pathway. Our studies suggest that EGCG has a higher binding affinity towards ENR of P. aeruginosa and is an efficient quorum-quenching reagent...

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

    Science.gov (United States)

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

    2013-03-13

    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.

  4. Detection of bacterial quorum sensing N-acyl homoserine lactones in clinical samples.

    Science.gov (United States)

    Kumari, Anjali; Pasini, Patrizia; Daunert, Sylvia

    2008-07-01

    Bacteria communicate among themselves using certain chemical signaling molecules. These signaling molecules generally are N-acyl homoserine lactones (AHLs) in Gram-negative bacteria and oligopeptides in Gram-positive bacteria. In addition, both Gram-positive and Gram-negative bacteria produce a family of signaling molecules known as autoinducer-2 that they employ for their communications. Bacteria coordinate their behavior by releasing and responding to the chemical signaling molecules present in proportion to their population density. This phenomenon is known as quorum sensing. The role of bacteria in the pathogenesis of several diseases, including gastrointestinal (GI) disorders, is well established. Moreover, rather recently bacterial quorum sensing has been implicated in the onset of bacterial pathogenicity. Thus, we hypothesized that the signaling molecules involved in bacterial communication may serve as potential biomarkers for the diagnosis and management of several bacteria-related diseases. For that, we previously developed a method based on genetically engineered whole-cell sensing systems for the rapid, sensitive, cost-effective and quantitative detection of AHLs in biological samples, such as saliva and stool, from both healthy and diseased individuals with GI disorders. Although various analytical methods, based on physical-chemical techniques and bacterial whole-cell biosensors, have been developed for the detection of AHLs in the supernatants of bacterial cultures, only a few of them have been applied to AHL monitoring in real samples. In this paper, we report work performed in our laboratory and review that from others that describes the detection of AHLs in biological, clinical samples, and report some of our recent experimental results.

  5. Toxicity and disruption of quorum sensing in Aliivibrio fisheri by environmental chemicals: Impacts of selected contaminants and microplastics

    Directory of Open Access Journals (Sweden)

    François Gagné

    2017-11-01

    Full Text Available The purpose of this study was to examine the effects of dissolved and particulate compounds on quorum sensing in the marine luminescent bacterium Aliivibrio fisheri. Bacteria were exposed to increasing concentrations of CuSO4 (Cu2+, gadolinium chloride (Gd3+, 20-nm silver nanoparticles (nanoAg and 1-3 μm microplastic polyethylene beads for 250 min. During this period, luminescence measurements were taken at 5-min intervals. Toxicity was first examined by measuring luminescence output at 5-min and 30-min incubation time. Based on the effective concentration that decreases luminescence by 20% (EC20, the compounds were toxic at the following concentrations in decreasing toxicity: Cu2+ (3.2 mg/L < nanoAg (3.4 mg/L, reported < Gd3+ (34 mg/L < microplastics (2.6 g/L. The data revealed that luminescence changed non-linearly over time. In control bacteria, luminescence changed at eight specific major frequencies between 0.04 and 0.27 cycle/min after Fourier transformation of time-dependent luminescence data. The addition of dissolved Cu2+ and Gd3+ eliminated the amplitude changes at these frequencies in a concentration-dependent manner, indicating loss of quorum sensing between bacteria at concentrations below EC20. In the presence of nanoAg and microplastic beads, the decreases in amplitudes were modest but compressed the luminescence profiles, with shorter frequencies appearing at concentrations well below EC20. Thus, loss of communication between bacteria occurs at non-toxic concentrations. In addition, with exposure to a mixture of the above compounds at concentrations that do not produce effects for Gd3+, nanoAg and microplastics, Cu2+ toxicity was significantly enhanced, suggesting synergy. This study revealed for the first time that small microplastic particles and nanoparticles can disrupt quorum sensing in marine bacteria.

  6. Transcriptome analysis revealed that a quorum sensing system regulates the transfer of the pAt megaplasmid in Agrobacterium tumefaciens.

    Science.gov (United States)

    Mhedbi-Hajri, Nadia; Yahiaoui, Noura; Mondy, Samuel; Hue, Nathalie; Pélissier, Franck; Faure, Denis; Dessaux, Yves

    2016-08-20

    Agrobacterium tumefaciens strain P4 is atypical, as the strain is not pathogenic and produces a for this species unusual quorum sensing signal, identified as N-(3-hydroxy-octanoyl)-homoserine lactone (3OH,C8-HSL). By sequence analysis and cloning, a functional luxI-like gene, named cinI, has been identified on the At plasmid of A. tumefaciens strain P4. Insertion mutagenesis in the cinI gene and transcriptome analyses permitted the identification of 32 cinI-regulated genes in this strain, most of them encoding proteins responsible for the conjugative transfer of pAtP4. Among these genes were the avhB genes that encode a type 4 secretion system (T4SS) involved in the formation of the conjugation apparatus, the tra genes that encode the DNA transfer and replication (Dtr) machinery and cinI and two luxR orthologs. These last two genes, cinR and cinX, exhibit an unusual organization, with the cinI gene surrounded by the two luxR orthologs. Conjugation experiments confirmed that the conjugative transfer of pAtP4 is regulated by 3OH,C8-HSL. Root colonization experiments indicated that the quorum sensing regulation of the conjugation of the pAtP4 does not confer a gain or a loss of fitness to the bacterial host in the tomato plant rhizosphere. This work is the first identification of the occurrence of a quorum sensing regulation of the pAt conjugation phenomenon in Agrobacterium.

  7. Abundance and distribution of Vibrio cholerae, V. parahaemolyticus, and V. vulnificus following a major freshwater intrusion into the Mississippi Sound.

    Science.gov (United States)

    Griffitt, Kimberly J; Grimes, D Jay

    2013-04-01

    In response to a major influx of freshwater to the Mississippi Sound following the opening of the Bonnet Carre Spillway, water samples were collected from three sites along the Mississippi shoreline to assess the impact of altered salinity on three pathogenic Vibrio species. Salinity readings across the affected area during the 2011 sample period ranged from 1.4 to 12.9 ppt (mean = 7.0) and for the 2012 sample period from 14.1 to 23.6 ppt (mean = 19.8). Analyses of the data collected in 2011 showed a reduction in densities of Vibrio parahaemolyticus and Vibrio vulnificus with a concurrent increase of Vibrio cholerae numbers, with V. cholerae becoming the only Vibrio detected once salinity readings dropped to 6 ppt. Follow-up samples taken in 2012 after recovery of the salinity in the sound showed that the relative densities of the three pathogenic vibrios had reverted back to normal levels. This study shows that although the spillway was open but a few weeks and the effects were therefore time limited, the Mississippi River water had a profound, if temporary, effect on Vibrio ecology in the Mississippi Sound.

  8. Functional conservation of RNase III-like enzymes: studies on a Vibrio vulnificus ortholog of Escherichia coli RNase III.

    Science.gov (United States)

    Lee, Minho; Ahn, Sangmi; Lim, Boram; Lee, Dong-Ho; Lee, Kangseok

    2014-04-01

    Bacterial ribonuclease III (RNase III) belongs to the RNase III enzyme family, which plays a pivotal role in controlling mRNA stability and RNA processing in both prokaryotes and eukaryotes. In the Vibrio vulnificus genome, one open reading frame encodes a protein homologous to E. coli RNase III, designated Vv-RNase III, which has 77.9 % amino acid identity to E. coli RNase III. Here, we report that Vv-RNase III has the same cleavage specificity as E. coli RNase III in vivo and in vitro. Expressing Vv-RNase III in E. coli cells deleted for the RNase III gene (rnc) restored normal rRNA processing and, consequently, growth rates of these cells comparable to wild-type cells. In vitro cleavage assays further showed that Vv-RNase III has the same cleavage activity and specificity as E. coli RNase III on RNase III-targeted sequences of corA and mltD mRNA. Our findings suggest that RNase III-like proteins have conserved cleavage specificity across bacterial species.

  9. Prevalence of Vibrio parahaemolyticus, and Vibrio vulnificus in blue crabs (Callinectes sapidus), seawater and sediments of the Maryland Coastal Bays.

    Science.gov (United States)

    Rodgers, C; Parveen, S; Chigbu, P; Jacobs, J; Rhodes, M; Harter-Dennis, J

    2014-10-01

    To determine the prevalence of total and pathogenic Vibrio parahaemolyticus (Vp) and V. vulnificus (Vv) in blue crabs, water and sediment from the Maryland Coastal Bays (MCBs), USA. Crab, haemolymph, sediment and seawater samples were collected monthly from four sites in MCBs from February 2012 through October 2012 with environmental parameters recorded. The most-probable-number (MPN) methodology was used to enumerate Vp and Vv with presumptive colonies and the presence of virulence markers confirmed using polymerase chain reaction (PCR). Results indicate that blue crabs contained both Vp and Vv at densities (7·28 and 5·43 log MPN g(-1) , respectively) higher than those reported for bivalves. In addition, markers for clinically relevant strains of both species were detected in over 30% of samples. Haemolymph, sediment and seawater samples were also routinely positive for both species and clinically relevant strains, but generally at lower densities than found in crabs (4·27, 3·28, and 2·39 log MPN g(-1) per ml(-1) Vp, and 4·28, 2·49 and 2·38 log MPN g(-1) per ml(-1) Vv). Blue crabs concentrate Vp and Vv at levels greater than found in water or sediment. While changes in abundance associated with temperature are apparent, there is little evidence to support differences among sampling locations. These results highlight the potential for blue crab related vibriosis and the importance of proper handling, cooking and care of this popular seafood before consumption. © 2014 The Society for Applied Microbiology.

  10. Faraday cage-type electrochemiluminescence immunosensor for ultrasensitive detection of Vibrio vulnificus based on multi-functionalized graphene oxide.

    Science.gov (United States)

    Guo, Zhiyong; Sha, Yuhong; Hu, Yufang; Yu, Zhongqing; Tao, Yingying; Wu, Yanjie; Zeng, Min; Wang, Sui; Li, Xing; Zhou, Jun; Su, Xiurong

    2016-10-01

    A novel Faraday cage-type electrochemiluminescence (ECL) immunosensor devoted to the detection of Vibrio vulnificus (VV) was fabricated. The sensing strategy was presented by a unique Faraday cage-type immunocomplex based on immunomagnetic beads (IMBs) and multi-functionalized graphene oxide (GO) labeled with (2,2'-bipyridine)(5-aminophenanthroline)ruthenium (Ru-NH2). The multi-functionalized GO could sit on the electrode surface directly due to the large surface area, abundant functional groups, and good electronic transport property. It ensures that more Ru-NH2 is entirely caged and become "effective," thus improving sensitivity significantly, which resembles extending the outer Helmholtz plane (OHP) of the electrode. Under optimal conditions, the developed immunosensor achieves a limit of detection as low as 1 CFU/mL. Additionally, the proposed immunosensor with high sensitivity and selectivity can be used for the detection of real samples. The novel Faraday cage-type method has shown potential application for the diagnosis of VV and opens up a new avenue in ECL immunoassay. Graphical abstract Faraday cage-type immunoassay mode for ultrasensitive detection by extending OHP.

  11. Imaging N-acyl homoserine lactone quorum sensing in vivo

    DEFF Research Database (Denmark)

    Christensen, Louise Dahl; van Gennip, Maria; Jakobsen, Tim Holm

    2011-01-01

    In order to study N-acyl homoserine lactone (AHL)-based quorum sensing in vivo, we present a protocol using an Escherichia coli strain equipped with a luxR-based monitor system, which in the presence of exogenous AHL molecules expresses a green fluorescent protein (GFP). Lungs from mice challenged...... intratracheally with alginate beads containing both a P. aeruginosa strain together with the E. coli monitor strain can be investigated at different time points postinfection. Epifluorescent or confocal scanning laser microscopy (CSLM) is used to detect the GFP-expressing E. coli monitor strain in the lung...

  12. Quasisynchronization in Quorum Sensing Systems with Parameter Mismatches

    Directory of Open Access Journals (Sweden)

    Jianbao Zhang

    2014-01-01

    Full Text Available The paper investigates quasisynchronization in a communication system, which consists of cells communicating through quorum sensing. With the help of Lyapunov function method and Lur’e system approach, some sufficient conditions for quasisynchronization are presented, and a bound on the synchronization errors is derived. The obtained theoretical results show that the synchronization quality is influenced by two parameters detrimentally: the error bound depends almost linearly on the mismatches between cells and depends sensitively on the diffusion rates of the signals inward the cell membrane. Numerical experiments are carried out to verify the theoretical results.

  13. A quorum-sensing-induced bacteriophage defense mechanism

    DEFF Research Database (Denmark)

    Høyland-Kroghsbo, Nina Molin; Mærkedahl, Rasmus Baadsgaard; Svenningsen, Sine

    2013-01-01

    . Specifically, E. coli reduces the numbers of ¿ receptors on the cell surface in response to N-acyl-l-homoserine lactone (AHL) quorum-sensing signals, causing a 2-fold reduction in the phage adsorption rate. The modest reduction in phage adsorption rate leads to a dramatic increase in the frequency...... of uninfected survivor cells after a potent attack by virulent phages. Notably, this mechanism may apply to a broader range of phages, as AHLs also reduce the risk of ¿ phage infection through a different receptor. IMPORTANCE To enable the successful manipulation of bacterial populations, a comprehensive...

  14. Comparison of the Effects of Environmental Parameters on Growth Rates of Vibrio vulnificus Biotypes I, II, and III by Culture and Quantitative PCR Analysis ▿

    Science.gov (United States)

    Chase, Eva; Harwood, Valerie J.

    2011-01-01

    Vibrio vulnificus is a natural inhabitant of estuarine waters. The three known biotypes include (i) most human pathogens, (ii) primarily eel pathogens, and (iii) pathogens associated with fish and with human wound infections in Israel. Despite the frequently lethal consequences of V. vulnificus infections, the growth rates of the various biotypes and their response to environmental changes are not well characterized. We compared the specific growth rates (μ) of a representative of each biotype by culture and quantitative PCR (qPCR) analysis in a defined medium under varied pH, temperature, and salinity. Growth rates based on culturable concentrations were always higher than those based on qPCR estimates; however, both enumeration methods yielded comparable results on the influence of environmental factors on growth rates. Temperature (25°C, 30°C, 37°C), pH (7.0, 8.0), and salinity (5 to 40‰) all had significant effects on the μ of each biotype. Temperature had the greatest effect on the μ of biotype 1 (CMCP6), whereas salinity had the greatest effect on the μ of biotypes 2 (ATCC 33147) and 3 (302/99). The biotypes' growth rates varied significantly; biotype 1 grew most rapidly, while biotype 3 grew most slowly. The highest growth rates were achieved at 37°C, pH 7.0, and salinities of 15 to 30‰ (μ = 4.0, 2.9, and 2.4 generations h−1 for biotypes 1, 2, and 3, respectively). Other strains of the biotypes yielded comparable results, suggesting that the physiological responses of the biotypes are differentially affected by parameters that are highly variable both in estuarine environments and between the free-living and pathogen states of V. vulnificus. PMID:21515718

  15. Inhibition of the production of the Pseudomonas aeruginosa virulence factor pyocyanin in wild-type cells by quorum sensing autoinducer-mimics.

    Science.gov (United States)

    Morkunas, Bernardas; Galloway, Warren R J D; Wright, Megan; Ibbeson, Brett M; Hodgkinson, James T; O'Connell, Kieron M G; Bartolucci, Noemi; Della Valle, Martina; Welch, Martin; Spring, David R

    2012-11-14

    Pseudomonas aeruginosa is a notorious human pathogen associated with a range of life-threatening nosocomial infections. There is an increasing problem of antibiotic resistance in P. aeruginosa, highlighted by the emergence of multi-drug resistant strains. Thus the exploration of new strategies for the treatment of P. aeruginosa infections is clearly warranted. P. aeruginosa is known to produce a range of virulence factors that enhance its ability to damage the host tissue and cause disease. One of the most important virulence factors is pyocyanin. P. aeruginosa regulates pyocyanin production using an intercellular communication mechanism called quorum sensing, which is mediated by small signalling molecules termed autoinducers. One native autoinducer is N-(3-oxododecanoyl)-L-homoserine lactone (OdDHL). Herein we report the synthesis of a collection of abiotic OdDHL-mimics. A number of novel compounds capable of competing with the endogenous OdDHL and consequently, inhibiting the production of pyocyanin in cultures of wild type P. aeruginosa were identified. We present evidence suggesting that compounds of this general structural type act as direct antagonists of quorum sensing in P. aeruginosa and as such may find value as molecular tools for the study and manipulation of this signalling pathway. A direct quantitative comparison of the pyocyanin suppressive activities of the most active OdDHL-mimics with some previously-reported inhibitors (based around different general structural frameworks) of quorum sensing from the literature, was also made.

  16. A Quorum Sensing-Disrupting Brominated Thiophenone with a Promising Therapeutic Potential to Treat Luminescent Vibriosis

    Science.gov (United States)

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

    2012-01-01

    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

  17. Anti-quorum sensing activity of phenolic extract from Eugenia brasiliensis (Brazilian cherry

    Directory of Open Access Journals (Sweden)

    Adeline Conceição RODRIGUES

    2016-01-01

    Full Text Available Abstract The aim of this study was to assess the anti-quorum sensing activity of phenolic extracts from grumixama (Eugenia brasiliensis, also known as Brazilian cherry, in concentrations that did not interfere with bacterial growth. The pulp phenolic compounds were extracted by using solid phage extraction in a mini-collumn C18 and quantified by spectrophotometry. The anti-quorum sensing activity was evaluated by testing the inhibition of violacein production in Chromobacterium violaceum and by evaluating the swarming motility in Aeromonas hydrophila and Serratia marcescens, both phenotypes regulated by quorum sensing. The phenolic extract strongly inhibited the production of violacein in C. violaceum, reducing its production in comparison with a control with no extract. No inhibition of growth was observed at the concentrations tested for quorum sensing inhibition. Confirming the quorum sensing inhibition phenotype, the extract was also able to inhibit swarming motility in S. marcescens and in A. hydrophila, although in the later the effect was marginal. Overall, these results indicate that phenolic extract from E. brasiliensis presents quorum sensing inhibitory activity most likely due to the presence of fruit phenolics which have been implicated as quorum sensing inhibitors in Gram negative bacteria.

  18. Zebrafish fed on recombinant Artemia expressing epinecidin-1 exhibit increased survival and altered expression of immunomodulatory genes upon Vibrio vulnificus infection.

    Science.gov (United States)

    Jheng, Yu-Hsuan; Lee, Lin-Han; Ting, Chen-Hung; Pan, Chieh-Yu; Hui, Cho-Fat; Chen, Jyh-Yih

    2015-01-01

    Artemia has been used extensively in aquaculture as fodder for larval fish, shrimp, and shellfish. Epinecidin-1, an antimicrobial peptide, was isolated from grouper (Epinephelus coioides) in 2005. Epinecidin-1 has been previously reported to possess antimicrobial activity against several Gram-positive and Gram-negative bacterial species, including Staphylococcus coagulase, Pseudomonas aeruginosa, Streptococcus pyogenes, and Vibrio vulnificus. In this study, we used electroporation to introduce plasmid DNA encoding a green fluorescent protein (EGFP)-epinecidin-1 fusion protein under the control of the cytomegalovirus (CMV) promoter into decapsulated Artemia cysts. Optimization of various properties (including cyst weight (0.2 g), plasmid concentration (50 μg/100 μl), and pulse voltage (150 V), length (10 ms), and number (2)) resulted in a hatching rate of 41.15%, a transfection efficiency of 49.81%, and a fluorescence intensity (A.U.) of 47.46. The expression of EGFP-epinecidin-1 was first detected by quantitative RT-PCR at 120 h post-electroporation, and protein was identified by Western blot at the same time. Furthermore, the EGFP-epinecidin-1 protein inhibited V. vulnificus (204) growth, as demonstrated by zone of inhibition studies. Zebrafish fed on transgenic Artemia expressing CMV-gfp-epi combined with commercial fodder were more resistant to infection by V. vulnificus (204): survival rate was enhanced by over 70% at 7, 14, and 21 days post-infection, and bacterial numbers in the liver and intestine were reduced. In addition, feeding of transgenic Artemia to zebrafish affected the immunomodulatory response to V. vulnificus (204) infection; expression of immune-responsive genes, including hepcidin and defbl2, was altered, as shown by qPCR. These findings suggest that feeding transgenic Artemia expressing CMV-gfp-epi to larval fish has antimicrobial effects, without the drawbacks of introducing drug residues or inducing bacterial drug resistance

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

    Science.gov (United States)

    Defoirdt, Tom; Sorgeloos, Patrick

    2012-01-01

    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

  20. The Vibrio cholerae quorum-sensing autoinducer CAI-1: analysis of the biosynthetic enzyme CqsA

    Energy Technology Data Exchange (ETDEWEB)

    Kelly, R.; Bolitho, M; Higgins, D; Lu, W; Ng, W; Jeffrey, P; Rabinowitz, J; Semmelhack, M; Hughson, F; Bassler, B

    2009-01-01

    Vibrio cholerae, the bacterium that causes the disease cholera, controls virulence factor production and biofilm development in response to two extracellular quorum-sensing molecules, called autoinducers. The strongest autoinducer, called CAI-1 (for cholera autoinducer-1), was previously identified as (S)-3-hydroxytridecan-4-one. Biosynthesis of CAI-1 requires the enzyme CqsA. Here, we determine the CqsA reaction mechanism, identify the CqsA substrates as (S)-2-aminobutyrate and decanoyl coenzyme A, and demonstrate that the product of the reaction is 3-aminotridecan-4-one, dubbed amino-CAI-1. CqsA produces amino-CAI-1 by a pyridoxal phosphate-dependent acyl-CoA transferase reaction. Amino-CAI-1 is converted to CAI-1 in a subsequent step via a CqsA-independent mechanism. Consistent with this, we find cells release {ge}100 times more CAI-1 than amino-CAI-1. Nonetheless, V. cholerae responds to amino-CAI-1 as well as CAI-1, whereas other CAI-1 variants do not elicit a quorum-sensing response. Thus, both CAI-1 and amino-CAI-1 have potential as lead molecules in the development of an anticholera treatment.

  1. Pyocyanin stimulates quorum sensing-mediated tolerance to oxidative stress and increases persister cell populations in Acinetobacter baumannii.

    Science.gov (United States)

    Bhargava, Nidhi; Sharma, Prince; Capalash, Neena

    2014-08-01

    Acinetobacter baumannii and Pseudomonas aeruginosa are nosocomial pathogens with overlapping sites of infection. This work reports that the two can coexist stably in mixed-culture biofilms. In a study intended to improve our understanding of the mechanism of their coexistence, it was found that pyocyanin, produced by P. aeruginosa that generally eliminates competition from other pathogens, led to the generation of reactive oxygen species (ROS) in A. baumannii cells, which in response showed a significant (P ≤ 0.05) increase in production of enzymes, specifically, catalase and superoxide dismutase (SOD). This work shows for the first time that the expression of catalase and SOD is under the control of a quorum-sensing system in A. baumannii. In support of this observation, a quorum-sensing mutant of A. baumannii (abaI::Km) was found to be sensitive to pyocyanin compared to its wild type and showed significantly (P ≤ 0.001) lower levels of the antioxidant enzymes, which increased on addition of 5 μM N-(3-hydroxydodecanoyl)-l-homoserine lactone. Likewise, in wild-type A. baumannii, there was a significant (P pyocyanin. These findings show that pyocyanin induces a protective mechanism in A. baumannii against oxidative stress and also increases its persistence against antibiotics which could be of clinical significance in the case of coinfections with A. baumannii and P. aeruginosa. Copyright © 2014, American Society for Microbiology. All Rights Reserved.

  2. Molecular basis for the substrate specificity of quorum signal synthases.

    Science.gov (United States)

    Dong, Shi-Hui; Frane, Nicole D; Christensen, Quin H; Greenberg, E Peter; Nagarajan, Rajesh; Nair, Satish K

    2017-08-22

    In several Proteobacteria , LuxI-type enzymes catalyze the biosynthesis of acyl-homoserine lactones (AHL) signals using S -adenosyl-l-methionine and either cellular acyl carrier protein (ACP)-coupled fatty acids or CoA-aryl/acyl moieties as progenitors. Little is known about the molecular mechanism of signal biosynthesis, the basis for substrate specificity, or the rationale for donor specificity for any LuxI member. Here, we present several cocrystal structures of BjaI, a CoA-dependent LuxI homolog that represent views of enzyme complexes that exist along the reaction coordinate of signal synthesis. Complementary biophysical, structure-function, and kinetic analysis define the features that facilitate the unusual acyl conjugation with S -adenosylmethionine (SAM). We also identify the determinant that establishes specificity for the acyl donor and identify residues that are critical for acyl/aryl specificity. These results highlight how a prevalent scaffold has evolved to catalyze quorum signal synthesis and provide a framework for the design of small-molecule antagonists of quorum signaling.

  3. Quorum quenching: role in nature and applied developments.

    Science.gov (United States)

    Grandclément, Catherine; Tannières, Mélanie; Moréra, Solange; Dessaux, Yves; Faure, Denis

    2016-01-01

    Quorum sensing (QS) refers to the capacity of bacteria to monitor their population density and regulate gene expression accordingly: the QS-regulated processes deal with multicellular behaviors (e.g. growth and development of biofilm), horizontal gene transfer and host-microbe (symbiosis and pathogenesis) and microbe-microbe interactions. QS signaling requires the synthesis, exchange and perception of bacterial compounds, called autoinducers or QS signals (e.g. N-acylhomoserine lactones). The disruption of QS signaling, also termed quorum quenching (QQ), encompasses very diverse phenomena and mechanisms which are presented and discussed in this review. First, we surveyed the QS-signal diversity and QS-associated responses for a better understanding of the targets of the QQ phenomena that organisms have naturally evolved and are currently actively investigated in applied perspectives. Next the mechanisms, targets and molecular actors associated with QS interference are presented, with a special emphasis on the description of natural QQ enzymes and chemicals acting as QS inhibitors. Selected QQ paradigms are detailed to exemplify the mechanisms and biological roles of QS inhibition in microbe-microbe and host-microbe interactions. Finally, some QQ strategies are presented as promising tools in different fields such as medicine, aquaculture, crop production and anti-biofouling area. © FEMS 2015. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  4. Proteomics of the bacterial cross-talk by quorum sensing.

    Science.gov (United States)

    Di Cagno, Raffaella; De Angelis, Maria; Calasso, Maria; Gobbetti, Marco

    2011-01-01

    Words such as language and behavior are frequently used to depict "quorum sensing" (QS) in the literature. Simplifying the concept, language and cross-talk between bacteria, and between bacteria and animal or plants hosts determine the behavior (e.g., beneficial or pathogenic effects). Genomics and transcriptomics were the principal approaches used to study the multiple mechanisms of QS. Nevertheless, sequencing of genomes paved the way for another approach which consists on comparative and functional proteomics. This review aims at describing how the proteomic dictionary translates: (i) the languages (N-acyl-L-homoserine lactones, AHL; autoinducing peptide, AIP; autoinducer-2, AI-2) used by bacteria to communicate; (ii) signals of QS which induce various phenotypes (e.g., virulence, biofilm maturation); (iii) cross-talk between lactic acid bacteria within various food ecosystems (e.g. sourdough and fermented milk); (iv) probiotic messages at intra- and inter-species and interkingdom levels; and (v) words for quorum quenching (QQ). Proteomics is an indispensible discipline to elucidate the mechanisms of regulation of the multitude of language signals which diffuse through different microbial communities. Copyright © 2010 Elsevier B.V. All rights reserved.

  5. Quorum Quenching in Culturable Phyllosphere Bacteria from Tobacco

    Directory of Open Access Journals (Sweden)

    Guoqiang Zhuang

    2013-07-01

    Full Text Available Many Gram-negative plant pathogenic bacteria employ a N-acylhomoserine lactone (AHL-based quorum sensing (QS system to regulate their virulence traits. A sustainable biocontrol strategy has been developed using quorum quenching (QQ bacteria to interfere with QS and protect plants from pathogens. Here, the prevalence and the diversity of QQ strains inhabiting tobacco leaf surfaces were explored. A total of 1177 leaf-associated isolates were screened for their ability to disrupt AHL-mediated QS, using the biosensor Chromobacterium violaceum CV026. One hundred and sixty-eight strains (14% are capable of interfering with AHL activity. Among these, 106 strains (63% of the culturable quenchers can enzymatically degrade AHL molecules, while the remaining strains might use other QS inhibitors to interrupt the chemical communication. Moreover, almost 79% of the QQ strains capable of inactivating AHLs enzymatically have lactonase activity. Further phylogenetic analysis based on 16S rDNA revealed that the leaf-associated QQ bacteria can be classified as Bacillus sp., Acinetobacter sp., Lysinibacillus sp., Serratia sp., Pseudomonas sp., and Myroides sp. The naturally occurring diversity of bacterial quenchers might provide opportunities to use them as effective biocontrol reagents for suppressing plant pathogen in situ.

  6. Non-thermal Plasma Exposure Rapidly Attenuates Bacterial AHL-Dependent Quorum Sensing and Virulence

    Science.gov (United States)

    Flynn, Padrig B.; Busetti, Alessandro; Wielogorska, Ewa; Chevallier, Olivier P.; Elliott, Christopher T.; Laverty, Garry; Gorman, Sean P.; Graham, William G.; Gilmore, Brendan F.

    2016-01-01

    The antimicrobial activity of atmospheric pressure non-thermal plasma has been exhaustively characterised, however elucidation of the interactions between biomolecules produced and utilised by bacteria and short plasma exposures are required for optimisation and clinical translation of cold plasma technology. This study characterizes the effects of non-thermal plasma exposure on acyl homoserine lactone (AHL)-dependent quorum sensing (QS). Plasma exposure of AHLs reduced the ability of such molecules to elicit a QS response in bacterial reporter strains in a dose-dependent manner. Short exposures (30–60 s) produce of a series of secondary compounds capable of eliciting a QS response, followed by the complete loss of AHL-dependent signalling following longer exposures. UPLC-MS analysis confirmed the time-dependent degradation of AHL molecules and their conversion into a series of by-products. FT-IR analysis of plasma-exposed AHLs highlighted the appearance of an OH group. In vivo assessment of the exposure of AHLs to plasma was examined using a standard in vivo model. Lettuce leaves injected with the rhlI/lasI mutant PAO-MW1 alongside plasma treated N-butyryl-homoserine lactone and n-(3-oxo-dodecanoyl)-homoserine lactone, exhibited marked attenuation of virulence. This study highlights the capacity of atmospheric pressure non-thermal plasma to modify and degrade AHL autoinducers thereby attenuating QS-dependent virulence in P. aeruginosa. PMID:27242335

  7. Mapping quorum sensing onto neural networks to understand collective decision making in heterogeneous microbial communities

    Science.gov (United States)

    Yusufaly, Tahir I.; Boedicker, James Q.

    2017-08-01

    Microbial communities frequently communicate via quorum sensing (QS), where cells produce, secrete, and respond to a threshold level of an autoinducer (AI) molecule, thereby modulating gene expression. However, the biology of QS remains incompletely understood in heterogeneous communities, where variant bacterial strains possess distinct QS systems that produce chemically unique AIs. AI molecules bind to ‘cognate’ receptors, but also to ‘non-cognate’ receptors found in other strains, resulting in inter-strain crosstalk. Understanding these interactions is a prerequisite for deciphering the consequences of crosstalk in real ecosystems, where multiple AIs are regularly present in the same environment. As a step towards this goal, we map crosstalk in a heterogeneous community of variant QS strains onto an artificial neural network model. This formulation allows us to systematically analyze how crosstalk regulates the community’s capacity for flexible decision making, as quantified by the Boltzmann entropy of all QS gene expression states of the system. In a mean-field limit of complete cross-inhibition between variant strains, the model is exactly solvable, allowing for an analytical formula for the number of variants that maximize capacity as a function of signal kinetics and activation parameters. An analysis of previous experimental results on the Staphylococcus aureus two-component Agr system indicates that the observed combination of variant numbers, gene expression rates and threshold concentrations lies near this critical regime of parameter space where capacity peaks. The results are suggestive of a potential evolutionary driving force for diversification in certain QS systems.

  8. Synthesis of (R)-norbgugaine and its potential as quorum sensing inhibitor against Pseudomonas aeruginosa

    Digital Repository Service at National Institute of Oceanography (India)

    Majik, M.S.; Naik, D.; Bhat, C.; Tilve, S.; Tilvi, S.; DeSouza, L.

    and cat hydrogenation as the key steps and its biological studies are reported for the first time. The synthesized norbgugaine was evaluated for inhibition of quorum sensing mediated virulence factors (motility, biofilm formation, pyocyanin pigmentation...

  9. Quorum sensing determines the choice of antiphage defense strategy in Vibrio anguillarum

    DEFF Research Database (Denmark)

    Tan, Demeng; Svenningsen, Sine Lo; Middelboe, Mathias

    2015-01-01

    -acylhomoserine lactone quorum-sensing signals in the culture medium, and (iii) survives mainly by one of these two defense mechanisms, rather than by genetic mutation to phage resistance. Taken together, our results demonstrate that V. anguillarum employs quorum-sensing information to choose between two complementary...... antiphage defense strategies. Further, the prevalence of nonmutational defense mechanisms in strain PF430-3 suggests highly flexible adaptations to KVP40 phage infection pressure, possibly allowing the long-term coexistence of phage and host. IMPORTANCE: Comprehensive knowledge on bacterial antiphage...... in pathogenic bacteria. Here, we demonstrate for the first time the presence of quorum-sensing-regulated phage defense mechanisms in the fish pathogen Vibrio anguillarum and provide evidence that quorum-sensing regulation allows V. anguillarum to alternate between different phage protection mechanisms depending...

  10. Quorum Sensing Protects Pseudomonas aeruginosa against Cheating by Other Species in a Laboratory Coculture Model.

    Science.gov (United States)

    Smalley, Nicole E; An, Dingding; Parsek, Matthew R; Chandler, Josephine R; Dandekar, Ajai A

    2015-10-01

    Many species of bacteria use a cell-cell communication system called quorum sensing (QS) to coordinate group activities. QS systems frequently regulate the production of exoproducts. Some of these products, such as proteases, are "public goods" that are shared among the population and vulnerable to cheating by nonproducing members of the population. Because the QS system of the opportunistic pathogen Pseudomonas aeruginosa regulates several public goods, it can serve as a model for studying cooperation. Bacteria also commonly regulate antimicrobial production through QS. In this study, we focused on the hypothesis that QS-regulated antimicrobials may be important for P. aeruginosa to protect against cheating by another bacterial species, Burkholderia multivorans. We assessed laboratory cocultures of P. aeruginosa and B. multivorans and investigated the importance of three P. aeruginosa QS-regulated antimicrobials, hydrogen cyanide, rhamnolipids, and phenazines, for competition. We found that P. aeruginosa dominates cocultures with B. multivorans and that the three antimicrobials together promote P. aeruginosa competitiveness, with hydrogen cyanide contributing the greatest effect. We show that these QS-regulated antimicrobials are also critical for P. aeruginosa to prevent B. multivorans from cheating under nutrient conditions where both species require a P. aeruginosa quorum-regulated protease for growth. Together our results highlight the importance of antimicrobials in protecting cooperating populations from exploitation by other species that can act as cheaters. Cooperative behaviors are threatened by social cheating, wherein individuals do not produce but nonetheless benefit from shared public goods. Bacteria have been shown to use several genetic mechanisms to restrain the emergence of cheaters from within the population, but public goods might also be used by other bacterial species in the vicinity. We demonstrate that a public good produced by Pseudomonas

  11. Anti-quorum sensing activity of phenolic extract from Eugenia brasiliensis (Brazilian cherry)

    OpenAIRE

    RODRIGUES,Adeline Conceição; OLIVEIRA,Brígida D’Ávila de; SILVA,Elis Regina da; SACRAMENTO,Nayara Thais Barbosa; BERTOLDI,Michele Corrêa; PINTO,Uelinton Manoel

    2016-01-01

    Abstract The aim of this study was to assess the anti-quorum sensing activity of phenolic extracts from grumixama (Eugenia brasiliensis), also known as Brazilian cherry, in concentrations that did not interfere with bacterial growth. The pulp phenolic compounds were extracted by using solid phage extraction in a mini-collumn C18 and quantified by spectrophotometry. The anti-quorum sensing activity was evaluated by testing the inhibition of violacein production in Chromobacterium violaceum and...

  12. Mini Review of Phytochemicals and Plant Taxa with Activity as Microbial Biofilm and Quorum Sensing Inhibitors

    OpenAIRE

    Chieu Anh Kim Ta; John Thor Arnason

    2015-01-01

    Microbial biofilms readily form on many surfaces in nature including plant surfaces. In order to coordinate the formation of these biofilms, microorganisms use a cell-to-cell communication system called quorum sensing (QS). As formation of biofilms on vascular plants may not be advantageous to the hosts, plants have developed inhibitors to interfere with these processes. In this mini review, research papers published on plant-derived molecules that have microbial biofilm or quorum sensing inh...

  13. Classroom Activities to Engage Students and Promote Critical Thinking about Genetic Regulation of Bacterial Quorum Sensing

    OpenAIRE

    Kimberly Aebli; Elizabeth Hutchison

    2016-01-01

    We developed an interactive activity to mimic bacterial quorum sensing, and a classroom worksheet to promote critical thinking about genetic regulation of the lux operon. The interactive quorum sensing activity engages students and provides a direct visualization of how population density functions to influence light production in bacteria. The worksheet activity consists of practice problems that require students to apply basic knowledge of the lux operon in order to make predictions about g...

  14. Transition to quorum sensing in an Agrobacterium population: A stochastic model.

    Directory of Open Access Journals (Sweden)

    Andrew B Goryachev

    2005-09-01

    Full Text Available Understanding of the intracellular molecular machinery that is responsible for the complex collective behavior of multicellular populations is an exigent problem of modern biology. Quorum sensing, which allows bacteria to activate genetic programs cooperatively, provides an instructive and tractable example illuminating the causal relationships between the molecular organization of gene networks and the complex phenotypes they control. In this work we--to our knowledge for the first time--present a detailed model of the population-wide transition to quorum sensing using the example of Agrobacterium tumefaciens. We construct a model describing the Ti plasmid quorum-sensing gene network and demonstrate that it behaves as an "on-off" gene expression switch that is robust to molecular noise and that activates the plasmid conjugation program in response to the increase in autoinducer concentration. This intracellular model is then incorporated into an agent-based stochastic population model that also describes bacterial motion, cell division, and chemical communication. Simulating the transition to quorum sensing in a liquid medium and biofilm, we explain the experimentally observed gradual manifestation of the quorum-sensing phenotype by showing that the transition of individual model cells into the "on" state is spread stochastically over a broad range of autoinducer concentrations. At the same time, the population-averaged values of critical autoinducer concentration and the threshold population density are shown to be robust to variability between individual cells, predictable and specific to particular growth conditions. Our modeling approach connects intracellular and population scales of the quorum-sensing phenomenon and provides plausible answers to the long-standing questions regarding the ecological and evolutionary significance of the phenomenon. Thus, we demonstrate that the transition to quorum sensing requires a much higher threshold

  15. Transition to Quorum Sensing in an Agrobacterium Population: A Stochastic Model.

    Directory of Open Access Journals (Sweden)

    2005-09-01

    Full Text Available Understanding of the intracellular molecular machinery that is responsible for the complex collective behavior of multicellular populations is an exigent problem of modern biology. Quorum sensing, which allows bacteria to activate genetic programs cooperatively, provides an instructive and tractable example illuminating the causal relationships between the molecular organization of gene networks and the complex phenotypes they control. In this work we-to our knowledge for the first time-present a detailed model of the population-wide transition to quorum sensing using the example of Agrobacterium tumefaciens. We construct a model describing the Ti plasmid quorum-sensing gene network and demonstrate that it behaves as an "on-off" gene expression switch that is robust to molecular noise and that activates the plasmid conjugation program in response to the increase in autoinducer concentration. This intracellular model is then incorporated into an agent-based stochastic population model that also describes bacterial motion, cell division, and chemical communication. Simulating the transition to quorum sensing in a liquid medium and biofilm, we explain the experimentally observed gradual manifestation of the quorum-sensing phenotype by showing that the transition of individual model cells into the "on" state is spread stochastically over a broad range of autoinducer concentrations. At the same time, the population-averaged values of critical autoinducer concentration and the threshold population density are shown to be robust to variability between individual cells, predictable and specific to particular growth conditions. Our modeling approach connects intracellular and population scales of the quorum-sensing phenomenon and provides plausible answers to the long-standing questions regarding the ecological and evolutionary significance of the phenomenon. Thus, we demonstrate that the transition to quorum sensing requires a much higher threshold cell

  16. PimT, an amino acid exporter controls polyene production via secretion of the quorum sensing pimaricin-inducer PI-factor in Streptomyces natalensis

    Directory of Open Access Journals (Sweden)

    Guerra Susana M

    2009-06-01

    Full Text Available Abstract Background Polyenes represent a major class of antifungal agents characterised by the presence of a series of conjugated double bonds in their planar hydroxylated macrolide ring structure. Despite their general interest, very little is known about the factors that modulate their biosynthesis. Among these factors, we have recently discovered a new inducing compound (PI-factor in the pimaricin producer Streptomyces natalensis, which elicits polyene production in a manner characteristic of quorum sensing. Here, we describe the involvement of an amino-acid exporter from S. natalensis in modulating the expression of pimaricin biosynthetic genes via secretion of the quorum-sensing pimaricin-inducer PI-factor. Results Adjacent to the pimaricin gene cluster lies a member of the RhtB family of amino-acid exporters. Gene deletion and complementation experiments provided evidence for a role for PimT in the export of L-homoserine, L-serine, and L-homoserine lactone. Expression of the gene was shown to be induced by homoserine and by the quorum-sensing pimaricin-inducer PI-factor. Interestingly, the mutant displayed 65% loss of pimaricin production, and also 50% decrease in the production of PI, indicating that PimT is used as PI-factor exporter, and suggesting that the effect in antifungal production might be due to limited secretion of the inducer. Conclusion This report describes the involvement of an amino acid exporter (encoded by pimT in the vicinity of the pimaricin cluster in modulating the expression of antibiotic biosynthetic genes via secretion of the quorum-sensing pimaricin-inducer PI-factor. The discovery of the participation of amino acid exporters in a signal transduction cascade for the production of polyene macrolides is unexpected, and represents an important step forward towards understanding the regulatory network for polyene regulation. Additionally, this finding constitutes the first detailed characterization of an amino

  17. Inhibition of quorum sensing-controlled virulence factors and biofilm formation in Pseudomonas fluorescens by cinnamaldehyde.

    Science.gov (United States)

    Li, Tingting; Wang, Dangfeng; Liu, Nan; Ma, Yan; Ding, Ting; Mei, Yongchao; Li, Jianrong

    2018-02-01

    Pseudomonas fluorescens, an important food spoiling bacteria, uses quorum sensing to control biofilm formation and motility. To date, only a few compounds targeting the LuxR-based quorum sensing system of P. fluorescens have been identified. In the present study, the quorum sensing inhibitory effect of cinnamaldehyde at sublethal concentrations was investigated in terms of inhibition of the extracellular protease, biofilm formation, and swimming and swarming motility. The total volatile basic nitrogen value was also measured to evaluate the effect of cinnamaldehyde on quality preservation of turbot fillets stored at 4 ± 1 °C for 15 days. The results showed that cinnamaldehyde significantly inhibited quorum sensing-dependent factors in P. fluorescens and extended the storage life of turbot. Unexpectedly, cinnamaldehyde did not interfere with production of AHLs (N-acylhomoserine lactones) by P. fluorescens, as shown by measurement of AHL production using GC-MS. Molecular docking analysis revealed that cinnamaldehyde can interact with the LuxR-type protein of P. fluorescens, which could constitute the molecular basis of the quorum sensing inhibition observed. These findings strongly suggest that cinnamaldehyde is a quorum sensing inhibitor with great potential for the preservation of aquatic products to guarantee food safety. Copyright © 2018. Published by Elsevier B.V.

  18. Plant-Derived Natural Products as Sources of Anti-Quorum Sensing Compounds

    Directory of Open Access Journals (Sweden)

    Kok-Gan Chan

    2013-05-01

    Full Text Available Quorum sensing is a system of stimuli and responses in relation to bacterial cell population density that regulates gene expression, including virulence determinants. Consequently, quorum sensing has been an attractive target for the development of novel anti-infective measures that do not rely on the use of antibiotics. Anti-quorum sensing has been a promising strategy to combat bacterial infections as it is unlikely to develop multidrug resistant pathogens since it does not impose any selection pressure. A number of anti-quorum sensing approaches have been documented and plant-based natural products have been extensively studied in this context. Plant matter is one of the major sources of chemicals in use today in various industries, ranging from the pharmaceutical, cosmetic, and food biotechnology to the textile industries. Just like animals and humans, plants are constantly exposed to bacterial infections, it is therefore logical to expect that plants have developed sophisticated of chemical mechanisms to combat pathogens. In this review, we have surveyed the various types of plant-based natural products that exhibit anti-quorum sensing properties and their anti-quorum sensing mechanisms.

  19. Death and Survival in Streptococcus mutans: Differing Outcomes of a Quorum-Sensing Signalling Peptide

    Directory of Open Access Journals (Sweden)

    Vincent eLeung

    2015-10-01

    Full Text Available Bacteria are considered ‘social’ organisms able to communicate with one another using small hormone-like molecules (pheromones in a process called quorum-sensing. These signalling molecules increase in concentration as a function of bacterial cell density. For most human pathogens, quorum-sensing is critical for virulence and biofilm formation, and the opportunity to interfere with bacterial quorum-sensing could provide a sophisticated means for manipulating the composition of pathogenic biofilms, and possibly eradicating the infection. Streptococcus mutans is a well-characterized resident of the dental plaque biofilm, and is the major pathogen of dental caries (tooth decay. In S. mutans, its CSP quorum-sensing signalling peptide does not act as a classical quorum-sensing signal by accumulating passively in proportion to cell density. In fact, particular stresses such as those encountered in the oral cavity, induces the production of the CSP pheromone, suggesting that the pheromone most probably functions as a stress-inducible alarmone by triggering the signalling to the bacterial population to initiate an adaptive response that results in different phenotypic outcomes. This mini-review discusses two different CSP-induced phenotypes, bacterial ‘suicide’ and dormancy, and the underlying mechanisms by which S. mutans utilizes the same quorum-sensing signalling peptide to regulate two opposite phenotypes.

  20. Bacterial autoinducer-2 detection via an engineered quorum sensing protein.

    Science.gov (United States)

    Raut, Nilesh; Joel, Smita; Pasini, Patrizia; Daunert, Sylvia

    2015-03-03

    Autoinducer-2 (AI-2) is a Quorum Sensing (QS) molecule utilized by bacteria in interspecies communication. More recently, it is identified to be vital in regulating QS pathways in a number of human and foodborne pathogens. Methods to detect AI-2 in a rapid and highly sensitive manner can help in the early detection of bacterial infections. Herein, we describe a rapid, selective, and highly sensitive protein based biosensing system employing the Fluorescence Resonance Energy Transfer (FRET) between a protein fusion LuxP-EGFP and 7-diethylamino-3-[N-(2-maleimidoethyl)carbamoyl]coumarin (MDCC). The developed biosensing system, which can detect AI-2 at subnanomolar levels, was successfully applied to detect AI-2 in clinical samples such as saliva and blood serum.

  1. Studying bacterial quorum-sensing at the single cell level

    Science.gov (United States)

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

    2010-03-01

    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.

  2. Bulk input queues with quorum and multiple vacations

    Directory of Open Access Journals (Sweden)

    Dshalalow Jewgeni H.

    1996-01-01

    Full Text Available The authors study a single-server queueing system with bulk arrivals and batch service in accordance to the general quorum discipline: a batch taken for service is not less than r and not greater than R ( ≥ r . The server takes vacations each time the queue level falls below r ( ≥ 1 in accordance with the multiple vacation discipline. The input to the system is assumed to be a compound Poisson process. The analysis of the system is based on the theory of first excess processes developed by the first author. A preliminary analysis of such processes enabled the authors to obtain all major characteristics for the queueing process in an analytically tractable form. Some examples and applications are given.

  3. Bulk input queues with quorum and multiple vacations

    Directory of Open Access Journals (Sweden)

    Jewgeni H. Dshalalow

    1996-01-01

    Full Text Available The authors study a single-server queueing system with bulk arrivals and batch service in accordance to the general quorum discipline: a batch taken for service is not less than r and not greater than R(≥r. The server takes vacations each time the queue level falls below r(≥1 in accordance with the multiple vacation discipline. The input to the system is assumed to be a compound Poisson process. The analysis of the system is based on the theory of first excess processes developed by the first author. A preliminary analysis of such processes enabled the authors to obtain all major characteristics for the queueing process in an analytically tractable form. Some examples and applications are given.

  4. Flexible Dynamics of Two Quorum Sensing Coupled Repressilators

    CERN Document Server

    Hellen, Edward H

    2016-01-01

    Genetic oscillators play important roles in cell life regulation. The regulatory efficiency usually depends strongly on the emergence of stable collective dynamic modes, which requires designing the interactions between genetic networks. We investigate the dynamics of two identical synthetic genetic repressilators coupled by an additional plasmid which implements quorum sensing (QS) in each network thereby supporting global coupling. In a basic genetic ring oscillator network in which three genes inhibit each other in unidirectional manner, QS stimulates the transcriptional activity of chosen genes providing for competition between inhibitory and stimulatory activities localized in those genes. The "promoter strength", the Hill cooperativity coefficient of transcription repression, and the coupling strength, i.e., parameters controlling the basic rates of genetic reactions, were chosen for extensive bifurcation analysis. The results are presented as a map of dynamic regimes. We found that the remarkable multi...

  5. Quorum sensing inhibitors of Staphylococcus aureus from Italian medicinal plants.

    Science.gov (United States)

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

    2011-01-01

    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 δ-hemolysin. Quantification of δ-hemolysin found in culture supernatants permits the analysis of AGR activity at the translational rather than transcriptional level. We employed reversed phase high performance chromatographic (RP-HPLC) techniques to investigate the anti-QS activity of 168 extracts from 104 Italian plants through quantification of δ-hemolysin. Extracts from three medicinal plants (Ballota nigra, Castanea sativa, and Sambucus ebulus) exhibited a dose-dependent response in the production of δ-hemolysin, indicating anti-QS activity in a pathogenic MRSA isolate. © Georg Thieme Verlag KG Stuttgart · New York.

  6. Quorum Signal Inhibitors and Their Potential Use against Fish Diseases.

    Science.gov (United States)

    Chu, Weihua; McLean, Robert J C

    2016-06-01

    Quorum sensing (QS) is a process of bacterial communication used to control group behaviors, including bioluminescence, virulence factor production, biofilm formation, and biofilm antimicrobial tolerance. Many aquatic bacterial pathogens such as Aeromonas, Vibrio, and Edwardsiella spp. use QS to regulate virulence factor production. The disruption of QS has been shown to be an effective strategy in the competition between higher organisms and bacteria and more recently between bacterial species. For this reason, QS disruption has been proposed as a strategy to prevent bacterial pathogenicity. In this review, we summarize the current literature and illustrate the value of QS inhibitors in controlling virulence production in aquatic bacterial pathogens. This represents a new, nonantibiotic strategy to combat fish diseases. Received August 11, 2015; accepted January 26, 2016.

  7. How Quorum Sensing Connects Sporulation to Necrotrophism in Bacillus thuringiensis.

    Directory of Open Access Journals (Sweden)

    Stéphane Perchat

    2016-08-01

    Full Text Available Bacteria use quorum sensing to coordinate adaptation properties, cell fate or commitment to sporulation. The infectious cycle of Bacillus thuringiensis in the insect host is a powerful model to investigate the role of quorum sensing in natural conditions. It is tuned by communication systems regulators belonging to the RNPP family and directly regulated by re-internalized signaling peptides. One such RNPP regulator, NprR, acts in the presence of its cognate signaling peptide NprX as a transcription factor, regulating a set of genes involved in the survival of these bacteria in the insect cadaver. Here, we demonstrate that, in the absence of NprX and independently of its transcriptional activator function, NprR negatively controls sporulation. NprR inhibits expression of Spo0A-regulated genes by preventing the KinA-dependent phosphorylation of the phosphotransferase Spo0F, thus delaying initiation of the sporulation process. This NprR function displays striking similarities with the Rap proteins, which also belong to the RNPP family, but are devoid of DNA-binding domain and indirectly control gene expression via protein-protein interactions in Bacilli. Conservation of the Rap residues directly interacting with Spo0F further suggests a common inhibition of the sporulation phosphorelay. The crystal structure of apo NprR confirms that NprR displays a highly flexible Rap-like structure. We propose a molecular regulatory mechanism in which key residues of the bifunctional regulator NprR are directly and alternatively involved in its two functions. NprX binding switches NprR from a dimeric inhibitor of sporulation to a tetrameric transcriptional activator involved in the necrotrophic lifestyle of B. thuringiensis. NprR thus tightly coordinates sporulation and necrotrophism, ensuring survival and dissemination of the bacteria during host infection.

  8. How Quorum Sensing Connects Sporulation to Necrotrophism in Bacillus thuringiensis.

    Science.gov (United States)

    Perchat, Stéphane; Talagas, Antoine; Poncet, Sandrine; Lazar, Noureddine; Li de la Sierra-Gallay, Inès; Gohar, Michel; Lereclus, Didier; Nessler, Sylvie

    2016-08-01

    Bacteria use quorum sensing to coordinate adaptation properties, cell fate or commitment to sporulation. The infectious cycle of Bacillus thuringiensis in the insect host is a powerful model to investigate the role of quorum sensing in natural conditions. It is tuned by communication systems regulators belonging to the RNPP family and directly regulated by re-internalized signaling peptides. One such RNPP regulator, NprR, acts in the presence of its cognate signaling peptide NprX as a transcription factor, regulating a set of genes involved in the survival of these bacteria in the insect cadaver. Here, we demonstrate that, in the absence of NprX and independently of its transcriptional activator function, NprR negatively controls sporulation. NprR inhibits expression of Spo0A-regulated genes by preventing the KinA-dependent phosphorylation of the phosphotransferase Spo0F, thus delaying initiation of the sporulation process. This NprR function displays striking similarities with the Rap proteins, which also belong to the RNPP family, but are devoid of DNA-binding domain and indirectly control gene expression via protein-protein interactions in Bacilli. Conservation of the Rap residues directly interacting with Spo0F further suggests a common inhibition of the sporulation phosphorelay. The crystal structure of apo NprR confirms that NprR displays a highly flexible Rap-like structure. We propose a molecular regulatory mechanism in which key residues of the bifunctional regulator NprR are directly and alternatively involved in its two functions. NprX binding switches NprR from a dimeric inhibitor of sporulation to a tetrameric transcriptional activator involved in the necrotrophic lifestyle of B. thuringiensis. NprR thus tightly coordinates sporulation and necrotrophism, ensuring survival and dissemination of the bacteria during host infection.

  9. Octanoyl-Homoserine Lactone Is the Cognate Signal for Burkholderia mallei BmaR1-BmaI1 Quorum Sensing▿

    OpenAIRE

    Breck A. Duerkop; Ulrich, Ricky L.; Greenberg, E. Peter

    2007-01-01

    Acyl-homoserine lactones (HSLs) serve as quorum-sensing signals for many Proteobacteria. Members of the LuxI family of signal generators catalyze the production of acyl-HSLs, which bind to a cognate receptor in the LuxR family of transcription factors. The obligate animal pathogen Burkholderia mallei produces several acyl-HSLs, and the B. mallei genome has four luxR and two luxI homologs, each of which has been established as a virulence factor. To begin to delineate the relevant acyl-HSL sig...

  10. Temperature effect on high salinity depuration of Vibrio vulnificus and V. parahaemolyticus from the Eastern oyster (Crassostrea virginica).

    Science.gov (United States)

    Larsen, A M; Rikard, F S; Walton, W C; Arias, C R

    2015-01-02

    Vibrio vulnificus (Vv) and Vibrio parahaemolyticus (Vp) are opportunistic human pathogens naturally associated with the Eastern oyster Crassostrea virginica. The abundances of both pathogens in oysters are positively correlated with temperature, thus ingestion of raw oysters during the warm summer months is a risk factor for contracting illness from these bacteria. Current post-harvest processing (PHP) methods for elimination of these pathogens are expensive and kill the oyster, changing their organoleptic properties and making them less appealing to some consumers. High salinity has proven effective in reducing Vv numbers in the wild and our research aims at developing an indoor recirculating system to reduce pathogenic Vibrios while maintaining the taste and texture of live oysters. The goal of this study was to determine the influence of temperature on the efficacy of high salinity depuration. Vv was enumerated as most probable number (MPN) per gram of oyster tissue using the FDA-approved modified cellobiose polymyxin colistin (mCPC) protocol and with an alternative Vibrio specific media CHROMagar™ Vibrio (CaV). CaV was also used to quantify Vp. Oysters were held at 35 psu for 10 days at three temperatures: low (20°C), mid (22.5°C) and high (25°C). There was no difference in MPN/g of Vv between media; however more Vv isolates were obtained from mCPC than CaV. There was no significant effect of temperature on reduction of Vv or Vp throughout depuration but there was a tendency for low temperatures to be less effective than the higher ones. High salinity resulted in a significant decrease in Vv by day 3 and again by day 10, and a decrease in Vp by day 3. Oyster condition indices were maintained throughout depuration and mortality was low (4% across three trials). Overall these results support the use of mCPC for Vv enumeration and demonstrate the promise of high salinity depuration for PHP of the Eastern oyster. The trend for lower temperatures to be less

  11. Quorum sensing activity of a Kluyvera sp. isolated from a Malaysian waterfall.

    Science.gov (United States)

    Yunos, Nina Yusrina Muhamad; Tan, Wen-Si; Mohamad, Nur Izzati; Tan, Pui-Wan; Adrian, Tan-Guan-Sheng; Yin, Wai-Fong; Chan, Kok-Gan

    2014-05-08

    In many species of bacteria, the quorum sensing mechanism is used as a unique communication system which allows them to regulate gene expression and behavior in accordance with their population density. N-Acylhomoserine lactones (AHLs) are known as diffusible autoinducer molecules involved in this communication network. This finding aimed to characterize the production of AHL of a bacterial strain ND04 isolated from a Malaysian waterfall. Strain ND04 was identified as Kluyvera sp. as confirmed by molecular analysis of its 16S ribosomal RNA gene sequence. Kluyvera sp. is closely related to the Enterobacteriaceae family. Chromobacterium violaceum CV026 was used as a biosensor to detect the production of AHL by strain ND04. High resolution triple quadrupole liquid chromatography-mass spectrometry analysis of strain ND04 showed our isolate produced two AHLs which are N-(3-oxohexanoyl)homoserine lactone (3-oxo-C6 HSL) and N-3-oxo-octanoyl-L-homoserine lactone (3-oxo-C8 HSL).

  12. Quorum Sensing Activity of a Kluyvera sp. Isolated from a Malaysian Waterfall

    Directory of Open Access Journals (Sweden)

    Nina Yusrina Muhamad Yunos

    2014-05-01

    Full Text Available In many species of bacteria, the quorum sensing mechanism is used as a unique communication system which allows them to regulate gene expression and behavior in accordance with their population density. N-Acylhomoserine lactones (AHLs are known as diffusible autoinducer molecules involved in this communication network. This finding aimed to characterize the production of AHL of a bacterial strain ND04 isolated from a Malaysian waterfall. Strain ND04 was identified as Kluyvera sp. as confirmed by molecular analysis of its 16S ribosomal RNA gene sequence. Kluyvera sp. is closely related to the Enterobacteriaceae family. Chromobacterium violaceum CV026 was used as a biosensor to detect the production of AHL by strain ND04. High resolution triple quadrupole liquid chromatography-mass spectrometry analysis of strain ND04 showed our isolate produced two AHLs which are N-(3-oxohexanoylhomoserine lactone (3-oxo-C6 HSL and N-3-oxo-octanoyl-L-homoserine lactone (3-oxo-C8 HSL.

  13. Methylobacterium-plant interaction genes regulated by plant exudate and quorum sensing molecules.

    Science.gov (United States)

    Dourado, Manuella Nóbrega; Bogas, Andrea Cristina; Pomini, Armando M; Andreote, Fernando Dini; Quecine, Maria Carolina; Marsaioli, Anita J; Araújo, Welington Luiz

    2013-12-01

    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.

  14. Methylobacterium-plant interaction genes regulated by plant exudate and quorum sensing molecules

    Directory of Open Access Journals (Sweden)

    Manuella Nóbrega Dourado

    2013-12-01

    Full Text Available 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.

  15. Solonamide B inhibits quorum sensing and reduces Staphylococcus aureus mediated killing of human neutrophils.

    Science.gov (United States)

    Nielsen, Anita; Månsson, Maria; Bojer, Martin S; Gram, Lone; Larsen, Thomas O; Novick, Richard P; Frees, Dorte; Frøkiær, Hanne; Ingmer, Hanne

    2014-01-01

    Methicillin-resistant Staphylococcus aureus (MRSA) continues to be a serious human pathogen, and particularly the spread of community associated (CA)-MRSA strains such as USA300 is a concern, as these strains can cause severe infections in otherwise healthy adults. Recently, we reported that a cyclodepsipeptide termed Solonamide B isolated from the marine bacterium, Photobacterium halotolerans strongly reduces expression of RNAIII, the effector molecule of the agr quorum sensing system. Here we show that Solonamide B interferes with the binding of S. aureus autoinducing peptides (AIPs) to sensor histidine kinase, AgrC, of the agr two-component system. The hypervirulence of USA300 has been linked to increased expression of central virulence factors like α-hemolysin and the phenol soluble modulins (PSMs). Importantly, in strain USA300 Solonamide B dramatically reduced the activity of α-hemolysin and the transcription of psma encoding PSMs with an 80% reduction in toxicity of supernatants towards human neutrophils and rabbit erythrocytes. To our knowledge this is the first report of a compound produced naturally by a Gram-negative marine bacterium that interferes with agr and affects both RNAIII and AgrA controlled virulence gene expression in S. aureus.

  16. Solonamide B inhibits quorum sensing and reduces Staphylococcus aureus mediated killing of human neutrophils.

    Directory of Open Access Journals (Sweden)

    Anita Nielsen

    Full Text Available Methicillin-resistant Staphylococcus aureus (MRSA continues to be a serious human pathogen, and particularly the spread of community associated (CA-MRSA strains such as USA300 is a concern, as these strains can cause severe infections in otherwise healthy adults. Recently, we reported that a cyclodepsipeptide termed Solonamide B isolated from the marine bacterium, Photobacterium halotolerans strongly reduces expression of RNAIII, the effector molecule of the agr quorum sensing system. Here we show that Solonamide B interferes with the binding of S. aureus autoinducing peptides (AIPs to sensor histidine kinase, AgrC, of the agr two-component system. The hypervirulence of USA300 has been linked to increased expression of central virulence factors like α-hemolysin and the phenol soluble modulins (PSMs. Importantly, in strain USA300 Solonamide B dramatically reduced the activity of α-hemolysin and the transcription of psma encoding PSMs with an 80% reduction in toxicity of supernatants towards human neutrophils and rabbit erythrocytes. To our knowledge this is the first report of a compound produced naturally by a Gram-negative marine bacterium that interferes with agr and affects both RNAIII and AgrA controlled virulence gene expression in S. aureus.

  17. Epigallocatechin gallate from Camellia sinensis L. (Kuntze is a potential quorum sensing inhibitor in Chromobacterium violaceum

    Directory of Open Access Journals (Sweden)

    Joemar C. Taganna

    2008-06-01

    Full Text Available The problem on the widespread occurrence of antibiotic resistant strains of bacteria calls for novel methods of control of bacterial activity. One of the new viable alternatives to antibiotics is the use of substances that inhibit quorum sensing (QS – a bacterial communication system that has been known to regulate the expression of virulence genes during infection. In this study, epigallocatechin gallate (EGCG from green tea, Camellia sinensis L. (Kuntze was tested for its ability to inhibit QS in a test organism, Chromobacterium violaceum. This microorganism produces a violet-colored substance, violacein, through QS. This study aimed to detect inhibition of QS-regulated violacein production in C. violaceum by EGCG and to determine the dynamics of QS inhibition relative to the concentration of EGCG. The effect of increasing concentration of EGCG on both violacein production and cell density of treated and untreated C. violaceum was determined in a 96-well-microplate format and read at 570nm and 620nm for violacein production and growth, respectively. The results show that addition of EGCG increased the growth of the organism while there is concentration-dependent decrease in the QS-controlled production of violacein. This study thus establishes that EGCG is a potential QS inhibitor and can be further studied and developed for its use as an anti-pathogenic but non-toxic drug.

  18. Agaricus Blazei Hot Water Extract Shows Anti Quorum Sensing Activity in the Nosocomial Human PathogenPseudomonas Aeruginosa

    NARCIS (Netherlands)

    Sokovic, M.; Ciric, A.; Glamoclija, J.; Nicolic, M.; Griensven, van L.J.L.D.

    2014-01-01

    The edible mushroom Agaricus blazei Murill is known to induce protective immunomodulatory action against a variety of infectious diseases. In the present study we report potential anti-quorum sensing properties of A. blazei hot water extract. Quorum sensing (QS) plays an important role in virulence,

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

    Directory of Open Access Journals (Sweden)

    Evelina Papaioannou

    2013-09-01

    Full Text Available 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.

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

    Science.gov (United States)

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

    2013-04-01

    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.

  1. luxS Mutant Regulation: Quorum Sensing Impairment or Methylation Disorder?

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    Zhengwei Huang

    2012-05-01

    Full Text Available AI-2–mediated quorum sensing has been identified in various bacteria, including both Gram-negative and Gram-positive species, and numerous phenotypes have been reported to be regulated by this mechanism, using the luxS-mutant strain. But the AI-2 production process confused this regulatory function; some considered this regulation as the result of a metabolic change, which refers to an important metabolic cycle named activated methyl cycle (AMC, caused by luxS-mutant simultaneously with the defect of AI-2. Herein we hypothesized that the quorum sensing system—not the metabolic aspect—is responsible for such a regulatory function. In this study, we constructed plasmids infused with sahH and induced protein expression in the luxS-mutant strain to make the quorum-sensing system and metabolic system independent. The biofilm-related genes were investigated by real-time polymerase chain reaction (PCR, and the results demonstrated that the quorum-sensing completed strain restored the gene expression of the defective strain, but the metabolically completed one did not. This evidence supported our hypothesis that the autoinducer-2-mediated, quorum-sensing system, not the AMC, was responsible for luxS mutant regulation.

  2. Variability of the Quorum Sensing System in Natural Isolates of Bacillus sp.

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    Ines Mandic-Mulec

    2003-01-01

    Full Text Available Bacteria communicate with one another by (emitting and/or reacting to chemical signals. These communications, also known as quorum sensing, enable cells to control gene expression in response to cell density at the intra- and inter-species level. While bacteria use common signaling themes, variations in the design of the extracellular signals, the signal detection apparatus, and the biochemical mechanisms of signal relay have allowed quorum sensing systems to be adapted to diverse uses. The quorum sensing systems that govern natural genetic competence in Bacillus subtilis involve the ComX pheromones and the ComP-ComA, two-component regulator. ComX is synthesized as an inactive precursor and is then cleaved and modified by ComQ before export to the extra-cellular environment. The comQXP' loci of a set of natural Bacillus isolates have been sequenced and a striking polymorphism that correlates with specific patterns of activation of the quorum sensing response was shown. The ComX molecules representing different pherotypes were purified and characterized by mass spectroscopy. The analyses revealed that ComX variants also differ at the level of posttranslational modification of a conserved tryptophane residue, which was found to be an isoprenoid. The striking variability found in competence quorum sensing systems might be important for the survival of these bacteria in nature to escape the inappropriate induction of competence by closely related strains, playing the role of a sexual isolation mechanism.

  3. Quorum sensing inhibiting activity of Streptomyces coelicoflavus isolated from soil

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    Hassan eRamadan

    2016-05-01

    Full Text Available Quorum sensing (QS systems communicate bacterial population and stimulate microbial pathogenesis through signaling molecules. Inhibition of QS signals potentially suppresses microbial infections. Antimicrobial properties of Streptomyces have been extensively studied, however, less is known about quorum sensing inhibitory (QSI activities of Streptomyces. This study explored the QSI potential of Streptomyces isolated from soil. Sixty-five bacterial isolates were purified from soil samples with morphological characteristics of Streptomyces. The three isolates: S6, S12, and S17, exhibited QSI effect by screening with the reporter, Chromobacterium violaceum. Isolate S17 was identified as Streptomyces coelicoflavus by sequencing of the hypervariable regions (V1-V6 of 16S rRNA and was assigned gene bank number KJ855087. The QSI effect of the cell-free supernatant of isolate S17 was not abolished by proteinase K indicating the non-enzymatic activity of QSI components of S17. Three major compounds were isolated and identified, using spectroscopic techniques (1D, 2D NMR and Mass spectrometry, as behenic acid (docosanoic acid, borrelidin and 1H-pyrrole-2-carboxylic acid. 1H-pyrrole-2-carboxylic acid inhibited QS and related virulence factors of Pseudomonas aeruginosa PAO1 including; elastase, protease and pyocyanin without affecting Pseudomonas viability. At the molecular level, 1H-pyrrole-2-carboxylic acid suppressed the expression of QS genes (lasI, lasR, lasA, lasB, rhlI, rhlR, pqsA and pqsR. Moreover, QSI activity of S17 was assessed under different growth conditions and ISP2 medium supplemented with glucose 0.4% w/v and adjusted at pH 7, showed the highest QSI action. In conclusion, 1H-pyrrole-2-carboxylic acid, one of the major metabolites of Streptomyces isolate S17, inhibited QS and virulence determinants of P. aeruginosa PAO1. The findings of the study open the scope to exploit the in vivo efficacy of this active molecule as anti-pathogenic and

  4. Detection, Characterization, and Biological Effect of Quorum-Sensing Signaling Molecules in Peanut-Nodulating Bradyrhizobia

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    Walter Giordano

    2012-03-01

    Full Text Available Bacteria of the genus Bradyrhizobium are able to establish a symbiotic relationship with peanut (Arachis hypogaea root cells and to fix atmospheric nitrogen by converting it to nitrogenous compounds. Quorum sensing (QS is a cell-cell communication mechanism employed by a variety of bacterial species to coordinate behavior at a community level through regulation of gene expression. The QS process depends on bacterial production of various signaling molecules, among which the N-acylhomoserine lactones (AHLs are most commonly used by Gram-negative bacteria. Some previous reports have shown the production of QS signaling molecules by various rhizobia, but little is known regarding mechanisms of communication among peanut-nodulating strains. The aims of this study were to identify and characterize QS signals produced by peanut-nodulating bradyrhizobial strains and to evaluate their effects on processes related to cell interaction. Detection of AHLs in 53 rhizobial strains was performed using the biosensor strains Agrobacterium tumefaciens NTL4 (pZLR4 and Chromobacterium violaceum CV026 for AHLs with long and short acyl chains, respectively. None of the strains screened were found to produce AHLs with short acyl chains, but 14 strains produced AHLs with long acyl chains. These 14 AHL-producing strains were further studied by quantification of β-galactosidase activity levels (AHL-like inducer activity in NTL4 (pZLR4. Strains displaying moderate to high levels of AHL-like inducer activity were subjected to chemical identification of signaling molecules by high-performance liquid chromatography coupled to mass spectrometry (LC-MS/MS. For each AHL-producing strain, we found at least four different AHLs, corresponding to N-hexanoyl-DL-homoserine lactone (C6, N-(3-oxodecanoyl-L-homoserine lactone (3OC10, N-(3-oxododecanoyl-L-homoserine lactone (3OC12, and N-(3-oxotetradecanoyl-L-homoserine lactone (3OC14. Biological roles of 3OC10, 3OC12, and 3OC14 AHLs

  5. D-Ribose Interferes with Quorum Sensing to Inhibit Biofilm Formation of Lactobacillus paraplantarum L-ZS9

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    Lei Liu

    2017-09-01

    Full Text Available Biofilms help bacteria survive under adverse conditions, and the quorum sensing (QS system plays an important role in regulating their activities. Quorum sensing inhibitors (QSIs have great potential to inhibit pathogenic biofilm formation and are considered possible replacements for antibiotics; however, further investigation is required to understand the mechanisms of action of QSIs and to avoid inhibitory effects on beneficial bacteria. Lactobacillus paraplantarum L-ZS9, isolated from fermented sausage, is a bacteriocin-producing bacteria that shows potential to be a probiotic starter. Since exogenous autoinducer-2 (AI-2 promoted biofilm formation of the strain, expression of genes involved in AI-2 production was determined in L. paraplantarum L-ZS9, especially the key gene luxS. D-Ribose was used to inhibit biofilm formation because of its AI-2 inhibitory activity. Twenty-seven differentially expressed proteins were identified by comparative proteomic analysis following D-ribose treatment and were functionally classified into six groups. Real-time quantitative PCR showed that AI-2 had a counteractive effect on transcription of the genes tuf, fba, gap, pgm, nfo, rib, and rpoN. Over-expression of the tuf, fba, gap, pgm, and rpoN genes promoted biofilm formation of L. paraplantarum L-ZS9, while over-expression of the nfo and rib genes inhibited biofilm formation. In conclusion, D-ribose inhibited biofilm formation of L. paraplantarum L-ZS9 by regulating multiple genes involved in the glycolytic pathway, extracellular DNA degradation and transcription, and translation. This research provides a new mechanism of QSI regulation of biofilm formation of Lactobacillus and offers a valuable reference for QSI application in the future.

  6. D-Ribose Interferes with Quorum Sensing to Inhibit Biofilm Formation of Lactobacillus paraplantarum L-ZS9.

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    Liu, Lei; Wu, Ruiyun; Zhang, Jinlan; Shang, Nan; Li, Pinglan

    2017-01-01

    Biofilms help bacteria survive under adverse conditions, and the quorum sensing (QS) system plays an important role in regulating their activities. Quorum sensing inhibitors (QSIs) have great potential to inhibit pathogenic biofilm formation and are considered possible replacements for antibiotics; however, further investigation is required to understand the mechanisms of action of QSIs and to avoid inhibitory effects on beneficial bacteria. Lactobacillus paraplantarum L-ZS9, isolated from fermented sausage, is a bacteriocin-producing bacteria that shows potential to be a probiotic starter. Since exogenous autoinducer-2 (AI-2) promoted biofilm formation of the strain, expression of genes involved in AI-2 production was determined in L. paraplantarum L-ZS9, especially the key gene luxS. D-Ribose was used to inhibit biofilm formation because of its AI-2 inhibitory activity. Twenty-seven differentially expressed proteins were identified by comparative proteomic analysis following D-ribose treatment and were functionally classified into six groups. Real-time quantitative PCR showed that AI-2 had a counteractive effect on transcription of the genes tuf, fba, gap, pgm, nfo, rib, and rpoN. Over-expression of the tuf, fba, gap, pgm, and rpoN genes promoted biofilm formation of L. paraplantarum L-ZS9, while over-expression of the nfo and rib genes inhibited biofilm formation. In conclusion, D-ribose inhibited biofilm formation of L. paraplantarum L-ZS9 by regulating multiple genes involved in the glycolytic pathway, extracellular DNA degradation and transcription, and translation. This research provides a new mechanism of QSI regulation of biofilm formation of Lactobacillus and offers a valuable reference for QSI application in the future.

  7. Quorum sensing influences Vibrio harveyi growth rates in a manner not fully accounted for by the marker effect of bioluminescence.

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    Zeena E Nackerdien

    2008-02-01

    Full Text Available 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.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.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.

  8. Quorum sensing and social networking in the microbial world.

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    Atkinson, Steve; Williams, Paul

    2009-11-06

    For many years, bacterial cells were considered primarily as selfish individuals, but, in recent years, it has become evident that, far from operating in isolation, they coordinate collective behaviour in response to environmental challenges using sophisticated intercellular communication networks. Cell-to-cell communication between bacteria is mediated by small diffusible signal molecules that trigger changes in gene expression in response to fluctuations in population density. This process, generally referred to as quorum sensing (QS), controls diverse phenotypes in numerous Gram-positive and Gram-negative bacteria. Recent advances have revealed that bacteria are not limited to communication within their own species but are capable of 'listening in' and 'broadcasting to' unrelated species to intercept messages and coerce cohabitants into behavioural modifications, either for the good of the population or for the benefit of one species over another. It is also evident that QS is not limited to the bacterial kingdom. The study of two-way intercellular signalling networks between bacteria and both uni- and multicellular eukaryotes as well as between eukaryotes is just beginning to unveil a rich diversity of communication pathways.

  9. Bacterial quorum sensing and nitrogen cycling in rhizosphere soil

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

    2008-10-01

    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.

  10. Functions and regulation of quorum-sensing in Agrobacterium tumefaciens.

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    Lang, Julien; Faure, Denis

    2014-01-01

    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.

  11. Functions and regulation of quorum-sensing in Agrobacterium tumefaciens

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    Denis eFaure

    2014-01-01

    Full Text Available 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 twenty 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.

  12. Functions and regulation of quorum-sensing in Agrobacterium tumefaciens

    Science.gov (United States)

    Lang, Julien; Faure, Denis

    2014-01-01

    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

  13. Anti-quorum sensing potential of the mangrove Rhizophora annamalayana.

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

    2013-10-01

    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.

  14. The Effect of Magnetic Fields on the Quorum Sensing-Regulated Luminescence of Vibrio fischeri

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    Barron, Addie; Hagen, Steve; Son, Minjun

    2015-03-01

    Quorum sensing (QS) is a mechanism by which bacteria communicate through the secretion and detection of extracellular signaling molecules known as autoinducers. This research focuses on the quorum sensing regulated bioluminescence of Vibrio fischeri, a marine bacterium that lives in symbiosis with certain fish and squid species. Previous studies of V. harveyi, a close relative of V. fisheri, indicate that a strong magnetic field has a positive effect on V.harveyi bioluminescence. However the effect of magnetic fields on quorum sensing-regulated luminescence is in general poorly understood. We grew V. fischeri in solid and liquid growth media, subject to strong static magnetic fields, and imaged the bioluminescence over a period of forty-eight hours. Luminescence patterns were analyzed in both the spatial and time dimensions. We find no indication that a magnetic field influences Vibrio fischeri luminescence either positively or negatively. This research was funded by the Grant Number NSF DMR-1156737.

  15. Classroom Activities to Engage Students and Promote Critical Thinking about Genetic Regulation of Bacterial Quorum Sensing

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    Kimberly Aebli

    2016-05-01

    Full Text Available We developed an interactive activity to mimic bacterial quorum sensing, and a classroom worksheet to promote critical thinking about genetic regulation of the lux operon. The interactive quorum sensing activity engages students and provides a direct visualization of how population density functions to influence light production in bacteria. The worksheet activity consists of practice problems that require students to apply basic knowledge of the lux operon in order to make predictions about genetic complementation experiments, and students must evaluate how genetic mutations in the lux operon affect gene expression and overall phenotype. The worksheet promotes critical thinking and problem solving skills, and emphasizes the roles of diffusible signaling molecules, regulatory proteins, and structural proteins in quorum sensing.

  16. Molecular Mechanism of Quorum-Sensing in Enterococcus faecalis: Its Role in Virulence and Therapeutic Approaches

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    Ali, Liaqat; Goraya, Mohsan Ullah; Arafat, Yasir; Ajmal, Muhammad; Chen, Ji-Long; Yu, Daojin

    2017-01-01

    Quorum-sensing systems control major virulence determinants in Enterococcus faecalis, which causes nosocomial infections. The E. faecalis quorum-sensing systems include several virulence factors that are regulated by the cytolysin operon, which encodes the cytolysin toxin. In addition, the E. faecalis Fsr regulator system controls the expression of gelatinase, serine protease, and enterocin O16. The cytolysin and Fsr virulence factor systems are linked to enterococcal diseases that affect the health of humans and other host models. Therefore, there is substantial interest in understanding and targeting these regulatory pathways to develop novel therapies for enterococcal infection control. Quorum-sensing inhibitors could be potential therapeutic agents for attenuating the pathogenic effects of E. faecalis. Here, we discuss the regulation of cytolysin, the LuxS system, and the Fsr system, their role in E. faecalis-mediated infections, and possible therapeutic approaches to prevent E. faecalis infection. PMID:28467378

  17. Quorum sensing inhibitory potential and molecular docking studies of sesquiterpene lactones from Vernonia blumeoides.

    Science.gov (United States)

    Aliyu, Abubakar Babando; Koorbanally, Neil Anthony; Moodley, Brenda; Singh, Parvesh; Chenia, Hafizah Yousuf

    2016-06-01

    The increasing incidence of multidrug-resistant Gram-negative bacterial pathogens has focused research on the suppression of bacterial virulence via quorum sensing inhibition strategies, rather than the conventional antimicrobial approach. The anti-virulence potential of eudesmanolide sesquiterpene lactones previously isolated from Vernonia blumeoides was assessed by inhibition of quorum sensing and in silico molecular docking. Inhibition of quorum sensing-controlled violacein production in Chromobacterium violaceum was quantified using violacein inhibition assays. Qualitative modulation of quorum sensing activity and signal synthesis was investigated using agar diffusion double ring assays and C. violaceum and Agrobacterium tumefaciens biosensor systems. Inhibition of violacein production was concentration-dependent, with ⩾90% inhibition being obtained with ⩾2.4 mg ml(-1) of crude extracts. Violacein inhibition was significant for the ethyl acetate extract with decreasing inhibition being observed with dichloromethane, hexane and methanol extracts. Violacein inhibition ⩾80% was obtained with 0.071 mg ml(-1) of blumeoidolide B in comparison with ⩾3.6 mg ml(-1) of blumeoidolide A. Agar diffusion double ring assays indicated that only the activity of the LuxI synthase homologue, CviI, was modulated by blumeoidolides A and B, and V. blumeoides crude extracts, suggesting that quorum sensing signal synthesis was down-regulated or competitively inhibited. Finally, molecular docking was conducted to explore the binding conformations of sesquiterpene lactones into the binding sites of quorum sensing regulator proteins, CviR and CviR'. The computed binding energy data suggested that the blumeoidolides have a tendency to inhibit both CviR and CviR' with varying binding affinities. Vernonia eudesmanolide sesquiterpene lactones have the potential to be novel therapeutic agents, which might be important in reducing virulence and pathogenicity of drug-resistant bacteria

  18. Synthesis of new 3- and 4-substituted analogues of acyl homoserine lactone quorum sensing autoinducers

    DEFF Research Database (Denmark)

    Olsen, J. A.; Severinsen, R.; Rasmussen, T. B.

    2002-01-01

    The quorum sensing mechanism in Gram-negative bacteria uses small intercellular signal molecules, N-acyl-homoserine lactones (AHLs), to control transcription of specific genes in relation to population density. In this communication, we describe the parallel synthesis of new AHL analogues, in which...... substituents have been introduced into the 3- and 4-positions of the lactone ring. These analogues have been screened for their ability to activate and inhibit a Vibrio fischeri LuxI/LuxR-derived quorum sensing reporter system....

  19. Synthesis of new 3-and 4-substituted analogues of acyl homoserine lactone quorum sensing autoinducers

    DEFF Research Database (Denmark)

    Olsen, Jacob Alsbæk; Severinsen, Rune Eg; Rasmussen, Thomas Bovbjerg

    2002-01-01

    The quorum sensing mechanism in Gram-negative bacteria uses small intercellular signal molecules, N-acyl-homoserine lactones (AHLs), to control transcription of specific genes in relation to population density. In this communication, we describe the parallel synthesis of new AHL analogues, in which...... substituents have been introduced into the 3- and 4-positions of the lactone ring. These analogues have been screened for their ability to activate and inhibit a Vibrio fischeri LuxI/LuxR-derived quorum sensing reporter system....

  20. Functional characterization of a three-component regulatory system involved in quorum sensing-based regulation of peptide antibiotic production in Carnobacterium maltaromaticum

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    Quadri Luis EN

    2006-10-01

    Full Text Available Abstract Background Quorum sensing is a form of cell-to-cell communication that allows bacteria to control a wide range of physiological processes in a population density-dependent manner. Production of peptide antibiotics is one of the processes regulated by quorum sensing in several species of Gram-positive bacteria, including strains of Carnobacterium maltaromaticum. This bacterium and its peptide antibiotics are of interest due to their potential applications in food preservation. The molecular bases of the quorum sensing phenomenon controlling peptide antibiotic production in C. maltaromaticum remain poorly understood. The present study was aimed at gaining a deeper insight into the molecular mechanism involved in quorum sensing-mediated regulation of peptide antibiotic (bacteriocin production by C. maltaromaticum. We report the functional analyses of the CS (autoinducer-CbnK (histidine protein kinase-CbnR (response regulator three-component regulatory system and the three regulated promoters involved in peptide antibiotic production in C. maltaromaticum LV17B. Results CS-CbnK-CbnR system-dependent activation of carnobacterial promoters was demonstrated in both homologous and heterologous hosts using a two-plasmid system with a β-glucuronidase (GusA reporter read-out. The results of our analyses support a model in which the CbnK-CbnR two-component signal transduction system is necessary and sufficient to transduce the signal of the peptide autoinducer CS into the activation of the promoters that drive the expression of the genes required for production of the carnobacterial peptide antibiotics and the immunity proteins that protect the producer bacterium. Conclusions The CS-CbnK-CbnR triad forms a three-component regulatory system by which production of peptide antibiotics by C. maltaromaticum LV17B is controlled in a population density-dependent (or cell proximity-dependent manner. This regulatory mechanism would permit the bacterial

  1. A novel signal transduction pathway that modulates rhl quorum sensing and bacterial virulence in Pseudomonas aeruginosa.

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    Qiao Cao

    2014-08-01

    Full Text Available The rhl quorum-sensing (QS system plays critical roles in the pathogenesis of P. aeruginosa. However, the regulatory effects that occur directly upstream of the rhl QS system are poorly understood. Here, we show that deletion of gene encoding for the two-component sensor BfmS leads to the activation of its cognate response regulator BfmR, which in turn directly binds to the promoter and decreases the expression of the rhlR gene that encodes the QS regulator RhlR, causing the inhibition of the rhl QS system. In the absence of bfmS, the Acka-Pta pathway can modulate the regulatory activity of BfmR. In addition, BfmS tunes the expression of 202 genes that comprise 3.6% of the P. aeruginosa genome. We further demonstrate that deletion of bfmS causes substantially reduced virulence in lettuce leaf, reduced cytotoxicity, enhanced invasion, and reduced bacterial survival during acute mouse lung infection. Intriguingly, specific missense mutations, which occur naturally in the bfmS gene in P. aeruginosa cystic fibrosis (CF isolates such as DK2 strains and RP73 strain, can produce BfmS variants (BfmSL181P, BfmSL181P/E376Q, and BfmSR393H that no longer repress, but instead activate BfmR. As a result, BfmS variants, but not the wild-type BfmS, inhibit the rhl QS system. This study thus uncovers a previously unexplored signal transduction pathway, BfmS/BfmR/RhlR, for the regulation of rhl QS in P. aeruginosa. We propose that BfmRS TCS may have an important role in the regulation and evolution of P. aeruginosa virulence during chronic infection in CF lungs.

  2. Identification and characterization of a second quorum-sensing system in Agrobacterium tumefaciens A6.

    Science.gov (United States)

    Wang, Chao; Yan, Chunlan; Fuqua, Clay; Zhang, Lian-Hui

    2014-04-01

    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.

  3. Identification and Characterization of a Second Quorum-Sensing System in Agrobacterium tumefaciens A6

    Science.gov (United States)

    Wang, Chao; Yan, Chunlan; Fuqua, Clay

    2014-01-01

    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

  4. Quorum sensing of microalgae associated marine Ponticoccus sp. PD-2 and its algicidal function regulation.

    Science.gov (United States)

    Chi, Wendan; Zheng, Li; He, Changfei; Han, Bin; Zheng, Minggang; Gao, Wei; Sun, Chengjun; Zhou, Gefei; Gao, Xiangxing

    2017-12-01

    Quorum sensing (QS) systems play important roles in regulating many physiological functions of microorganisms, such as biofilm formation, bioluminescence, and antibiotic production. One marine algicidal bacterium, Ponticoccus sp. PD-2, was isolated from the microalga Prorocentrum donghaiense, and its N-acyl-homoserine lactone (AHL)-mediated QS system was verified. In this study, we analyzed the AHLs profile of strain PD-2. Two AHLs, 3-oxo-C8-HSL and 3-oxo-C10-HSL, were detected using a biosensor overlay assay and GC-MS methods. Two complete AHL-QS systems (designated zlaI/R and zlbI/R) were identified in the genome of strain PD-2. When expressed in Escherichia coli, both zlaI and zlbI genes could each produce 3-oxo-C8-HSL and 3-oxo-C10-HSL. Algicidal activity was investigated by evaluating the inhibitory rate (IR) of microalgae growth by measuring the fluorescence of viable cells. We found that the metabolites of strain PD-2 had algicidal activity against its host P. donghaiense (IR 84.81%) and two other red tide microalgae, Phaeocystis globosa (IR 78.91%) and Alexandrium tamarense (IR 67.14%). β-cyclodextrin which binds to AHLs and inhibits the QS system reduced the algicidal activity more than 50%. This indicates that inhibiting the QS system may affect the algicidal metabolites production of strain PD-2. Our study indicated that a QS-regulated algicidal system may play a potential role in the process of red tides disintegration. QS might be a potential way to control red tides.

  5. Whole-Cell Biosensors as Tools for the Detection of Quorum-Sensing Molecules: Uses in Diagnostics and the Investigation of the Quorum-Sensing Mechanism.

    Science.gov (United States)

    O'Connor, Gregory; Knecht, Leslie D; Salgado, Nelson; Strobel, Sebastian; Pasini, Patrizia; Daunert, Sylvia

    2015-10-17

    Genetically engineered bacterial whole-cell biosensors are powerful tools that take advantage of bacterial proteins and pathways to allow for detection of a specific analyte. These biosensors have been employed for a broad range of applications, including the detection of bacterial quorum-sensing molecules (QSMs). Bacterial QSMs are the small molecules bacteria use for population density-dependent communication, a process referred to as quorum sensing (QS). Various research groups have investigated the presence of QSMs, including N-acyl homoserine lactones (AHLs) and autoinducer-2 (AI-2), in physiological samples in attempts to enhance our knowledge of the role of bacteria and QS in disease states. Continued studies in these fields may allow for improved patient care and therapeutics based upon QSMs. Furthermore, bacterial whole-cell biosensors have elucidated the roles of some antibiotics as QS agonists and antagonists. Graphical Abstract.

  6. The plant pathogen Erwinia amylovora produces acyl-homoserine lactone signal molecules in vitro and in planta.

    Science.gov (United States)

    Venturi, Vittorio; Venuti, Chiara; Devescovi, Giulia; Lucchese, Carla; Friscina, Arianna; Degrassi, Giuliano; Aguilar, Claudio; Mazzucchi, Umberto

    2004-12-15

    We report for the first time the production of acyl homoserine lactones (AHLs) by Erwina amylovora, an important quarantine bacterial pathogen that causes fire blight in plants. E. amylovora produces one N-acyl homoserine lactone [a N-(3-oxo-hexanoyl)-homoserine lactone or a N-(3-hydroxy-hexanoyl)-homoserine lactone] quorum sensing signal molecule both in vitro and in planta (pear plant). Given the involvement of AHLs in plant pathogenesis, we speculate that AHL-dependent quorum sensing could play an important role in the regulation of E. amylovora virulence.

  7. Inhibition of marine biofouling by bacterial quorum sensing inhibitors.

    Science.gov (United States)

    Dobretsov, Sergey; Teplitski, Max; Bayer, Mirko; Gunasekera, Sarath; Proksch, Peter; Paul, Valerie J

    2011-09-01

    Seventy eight natural products from chemical libraries containing compounds from marine organisms (sponges, algae, fungi, tunicates and cyanobacteria) and terrestrial plants, were screened for the inhibition of bacterial quorum sensing (QS) using a reporter strain Chromobacterium violaceum CV017. About half of the natural products did not show any QS inhibition. Twenty four percent of the tested compounds inhibited QS of the reporter without causing toxicity. The QS inhibitory activities of the most potent and abundant compounds were further investigated using the LuxR-based reporter E. coli pSB401 and the LasR-based reporter E. coli pSB1075. Midpacamide and tenuazonic acid were toxic to the tested reporters. QS-dependent luminescence of the LasR-based reporter, which is normally induced by N-3-oxo-dodecanoyl-L-homoserine lactone, was reduced by demethoxy encecalin and hymenialdisin at concentrations >6.6 μM and 15 μM, respectively. Hymenialdisin, demethoxy encecalin, microcolins A and B and kojic acid inhibited responses of the LuxR-based reporter induced by N-3-oxo-hexanoyl-L-homoserine lactone at concentrations >0.2 μM, 2.2 μM, 1.5 μM, 15 μM and 36 μM, respectively. The ability to prevent microfouling by one of the compounds screened in this study (kojic acid; final concentrations 330 μM and 1 mM) was tested in a controlled mesocosm experiment. Kojic acid inhibited formation of microbial communities on glass slides, decreasing the densities of bacteria and diatoms in comparison with the control lacking kojic acid. The study suggests that natural products with QS inhibitory properties can be used for controlling biofouling communities.

  8. Leaders of neuronal cultures in a quorum percolation model

    Directory of Open Access Journals (Sweden)

    Jean-Pierre Eckmann

    2010-09-01

    Full Text Available We present a theoretical framework using quorum-percolation for describing the initiation of activity in a neural culture. The cultures are modeled as random graphs, whose nodes are neurons with $kin$ inputs and $kout$ outputs, and whose input degrees $kin=k$ obey given distribution functions $p_k$. We examine the firing activity of the population of neurons according to their input degree ($k$ classes and calculate for each class its firing probability $Phi_k(t$ as a function of $t$. The probability of a node to fire is found to be determined by its in-degree $k$, and the first-to-fire neurons are those that have a high $k$. A small minority of high-$k$ classes may be called ``Leaders,'' as they form an inter-connected subnetwork that consistently fires much before the rest of the culture. Once initiated, the activity spreads from the Leaders to the less connected majority of the culture. We then use the distribution of in-degree of the Leaders to study the growth rate of the number of neurons active in a burst, which was experimentally measured to be initially exponential. We find that this kind of growth rate is best described by a population that has an in-degree distribution that is a Gaussian centered around $k=75$ with width $sigma=31$ for the majority of the neurons, but also has a power law tail with exponent $-2$ for ten percent of the population. Neurons in the tail may have as many as $k=4,700$ inputs. We explore and discuss the correspondence between the degree distribution and a dynamic neuronal threshold, showing that from the functional point of view, structure and elementary dynamics are interchangeable. We discuss possible geometric origins of this distribution, and comment on the importance of size, or of having a large number of neurons, in the culture.

  9. Rational design and synthesis of new quorum-sensing inhibitors derived from acylated homoserine lactones and natural products from garlic

    DEFF Research Database (Denmark)

    Persson, T.; Rasmussen, Thomas Bovbjerg; Skindersoe, M.

    2005-01-01

    with similarity both to sulfides 10a-s and to bioactive structures from garlic. Design and biological screening of all compounds presented in this work targeted inhibition of quorum-sensing comprising competitive inhibition of transcriptional regulators LuxR and LasR. The design was based on critical interactions...... within the binding-site and structural motifs in molecular components isolated from garlic, 7 and 8, shown to be quorum-sensing inhibitors but not antibiotics. A potent quorum-sensing inhibitor N-(heptylsulfanylacetyl)-L-homoserine lactone (10c) was identified. Together with data collected for the other...

  10. Haloperoxidase Mediated Quorum Quenching by Nitzschia cf pellucida: Study of the Metabolization of N-Acyl Homoserine Lactones by a Benthic Diatom

    Directory of Open Access Journals (Sweden)

    Michail Syrpas

    2014-01-01

    Full Text Available Diatoms are known to produce a variety of halogenated compounds, which were recently shown to have a role in allelopathic interactions between competing species. The production of these compounds is linked to haloperoxidase activity. This research, has shown that this system may also be involved in diatom-bacteria interactions via the H2O2 dependent inactivation of a type of quorum sensing (QS molecule, i.e., N-β-ketoacylated homoserine lactones (AHLs, by a natural haloperoxidase system from the benthic diatom Nitzschia cf pellucida. The AHL degradation pathway towards corresponding halogenated derivatives was elucidated via HPLC-MS analysis and the synthesis of a broad series of novel halogenated AHL analogues as reference compounds. Furthermore, their biological activity as quorum sensing modulators was directly compared and evaluated against a series of naturally occurring β-keto-AHLs. It has been demonstrated that the loss of the QS activity results from the final cleavage of the halogenated N-acyl chain of the signal molecules.

  11. Choosing an appropriate infection model to study quorum sensing inhibition in Pseudomonas infections

    NARCIS (Netherlands)

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

    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

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

    NARCIS (Netherlands)

    Czaran, T.L.; Hoekstra, R.F.

    2007-01-01

    Like any form of cooperative behavior, quorum sensing (QS) in bacteria is potentially vulnerable to cheating, the occurrence of individuals that contribute less but still profit from the benefits provided by others. In this paper, we explore the evolutionary stability of QS as a regulatory mechanism

  13. NprR, a moonlighting quorum sensor shifting from a phosphatase activity to a transcriptional activator.

    Science.gov (United States)

    Perchat, Stéphane; Talagas, Antoine; Zouhir, Samira; Poncet, Sandrine; Bouillaut, Laurent; Nessler, Sylvie; Lereclus, Didier

    2016-11-04

    Regulation of biological functions requires factors (proteins, peptides or chemicals) able to sense and translate environmental conditions or any circumstances in order to modulate the transcription of a gene, the stability of a transcript or the activity of a protein. Quorum sensing is a regulation mechanism connecting cell density to the physiological state of a single cell. In bacteria, quorum sensing coordinates virulence, cell fate and commitment to sporulation and other adaptation properties. The critical role of such regulatory systems was demonstrated in pathogenicity and adaptation of bacteria from the Bacillus cereus group (i.e. B. cereus and Bacillus thuringiensis). Furthermore, using insects as a model of infection, it was shown that sequential activation of several quorum sensing systems allowed bacteria to switch from a virulence state to a necrotrophic lifestyle, allowing their survival in the host cadaver, and ultimately to the commitment into sporulation. The chronological development of these physiological states is directed by quorum sensors forming the RNPP family. Among them, NprR combines two distinct functions connecting sporulation to necrotrophism in B. thuringiensis. In the absence of its cognate signaling peptide (NprX), NprR negatively controls sporulation by acting as a phosphatase. In the presence of NprX, it acts as a transcription factor regulating a set of genes involved in the survival of the bacteria in the insect cadaver.

  14. Influence of clove oil on certain quorum-sensing-regulated functions ...

    Indian Academy of Sciences (India)

    2013-11-06

    Nov 6, 2013 ... MSc Thesis, Aligarh Muslim University, Aligarh, India. Skindersoe ME, Alhede M, Phipps R, Yang L, Jensen PO,. Rasmussen TB, Bjarnsholt T, Tolke-Nielsen T, Høiby N and. Givskov M 2008 Effects of antibiotics on quorum sensing in. Pseudomonas aeruginosa. Antimicrob. Agents Chemother. 52. 648– ...

  15. Going beyond the Control of Quorum-Sensing to Combat Biofilm Infections

    Directory of Open Access Journals (Sweden)

    Wolf-Rainer Abraham

    2016-01-01

    Full Text Available Most bacteria attach to surfaces where they form a biofilm, cells embedded in a complex matrix of polymers. Cells in biofilms are much better protected against noxious agents than free-living cells. As a consequence it is very difficult to control pathogens with antibiotics in biofilm infections and novel targets are urgently needed. One approach aims at the communication between cells to form and to maintain a biofilm, a process called quorum-sensing. Water soluble small-sized molecules mediate this process and a number of antagonists of these compounds have been found. In this review natural compounds and synthetic drugs which do not interfere with the classical quorum-sensing compounds are discussed. For some of these compounds the targets are still not known, but others interfere with the formation of exopolysaccharides, virulence factors, or cell wall synthesis or they start an internal program of biofilm dispersal. Some of their targets are more conserved among pathogens than the receptors for quorum sensing autoinducers mediating quorum-sensing, enabling a broader application of the drug. The broad spectrum of mechanisms, the diversity of bioactive compounds, their activity against several targets, and the conservation of some targets among bacterial pathogens are promising aspects for several clinical applications of this type of biofilm-controlling compound in the future.

  16. Cross-Talk between Staphylococcus aureus and Other Staphylococcal Species via the agr Quorum Sensing System

    DEFF Research Database (Denmark)

    Canovas de la Nuez, Jaime; Baldry, Mara; Bojer, Martin S

    2016-01-01

    Staphylococci are associated with both humans and animals. While most are non-pathogenic colonizers, Staphylococcus aureus is an opportunistic pathogen capable of causing severe infections. S. aureus virulence is controlled by the agr quorum sensing system responding to secreted auto-inducing pep...

  17. Surface hardness impairment of quorum sensing and swarming for Pseudomonas aeruginosa.

    Directory of Open Access Journals (Sweden)

    Nachiket G Kamatkar

    Full Text Available The importance of rhamnolipid to swarming of the bacterium Pseudomonas aeruginosa is well established. It is frequently, but not exclusively, observed that P. aeruginosa swarms in tendril patterns--formation of these tendrils requires rhamnolipid. We were interested to explain the impact of surface changes on P. aeruginosa swarm tendril development. Here we report that P. aeruginosa quorum sensing and rhamnolipid production is impaired when growing on harder semi-solid surfaces. P. aeruginosa wild-type swarms showed huge variation in tendril formation with small deviations to the "standard" swarm agar concentration of 0.5%. These macroscopic differences correlated with microscopic investigation of cells close to the advancing swarm edge using fluorescent gene reporters. Tendril swarms showed significant rhlA-gfp reporter expression right up to the advancing edge of swarming cells while swarms without tendrils (grown on harder agar showed no rhlA-gfp reporter expression near the advancing edge. This difference in rhamnolipid gene expression can be explained by the necessity of quorum sensing for rhamnolipid production. We provide evidence that harder surfaces seem to limit induction of quorum sensing genes near the advancing swarm edge and these localized effects were sufficient to explain the lack of tendril formation on hard agar. We were unable to artificially stimulate rhamnolipid tendril formation with added acyl-homoserine lactone signals or increasing the carbon nutrients. This suggests that quorum sensing on surfaces is controlled in a manner that is not solely population dependent.

  18. Experimental and Theoretical Investigation of Signaling in Quorum Sensing of Pseudomonas Aeruginosa

    DEFF Research Database (Denmark)

    Claussen, Anetta

    concentration) reaches a threshold value, after which the host system is surprised by a stealth attack. The focus of this study is on the Quorum Sensing regulatory system of Pseudomonas aeruginosa called the Las system. In this thesis, two distinct methods to obtain information about the system are considered...

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

    DEFF Research Database (Denmark)

    Hentzer, Morten; Riedel, Kathrin; Rasmussen, Thomas B

    2002-01-01

    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)....

  20. Artificially constructed quorum-sensing circuits are used for subtle control of bacterial population density.

    Directory of Open Access Journals (Sweden)

    Zhaoshou Wang

    Full Text Available Vibrio fischeri is a typical quorum-sensing bacterium for which lux box, luxR, and luxI have been identified as the key elements involved in quorum sensing. To decode the quorum-sensing mechanism, an artificially constructed cell-cell communication system has been built. In brief, the system expresses several programmed cell-death BioBricks and quorum-sensing genes driven by the promoters lux pR and PlacO-1 in Escherichia coli cells. Their transformation and expression was confirmed by gel electrophoresis and sequencing. To evaluate its performance, viable cell numbers at various time periods were investigated. Our results showed that bacteria expressing killer proteins corresponding to ribosome binding site efficiency of 0.07, 0.3, 0.6, or 1.0 successfully sensed each other in a population-dependent manner and communicated with each other to subtly control their population density. This was also validated using a proposed simple mathematical model.

  1. NprR, a moonlighting quorum sensor shifting from a phosphatase activity to a transcriptional activator

    Directory of Open Access Journals (Sweden)

    Stéphane Perchat

    2016-11-01

    Full Text Available Regulation of biological functions requires factors (proteins, peptides or chemicals able to sense and translate environmental conditions or any circumstances in order to modulate the transcription of a gene, the stability of a transcript or the activity of a protein. Quorum sensing is a regulation mechanism connecting cell density to the physiological state of a single cell. In bacteria, quorum sensing coordinates virulence, cell fate and commitment to sporulation and other adaptation properties. The critical role of such regulatory systems was demonstrated in pathogenicity and adaptation of bacteria from the Bacillus cereus group (i.e. B. cereus and Bacillus thuringiensis. Furthermore, using insects as a model of infection, it was shown that sequential activation of several quorum sensing systems allowed bacteria to switch from a virulence state to a necrotrophic lifestyle, allowing their survival in the host cadaver, and ultimately to the commitment into sporulation. The chronological development of these physiological states is directed by quorum sensors forming the RNPP family. Among them, NprR combines two distinct functions connecting sporulation to necrotrophism in B. thuringiensis. In the absence of its cognate signaling peptide (NprX, NprR negatively controls sporulation by acting as a phosphatase. In the presence of NprX, it acts as a transcription factor regulating a set of genes involved in the survival of the bacteria in the insect cadaver.

  2. Influence of clove oil on certain quorum-sensing-regulated functions

    Indian Academy of Sciences (India)

    Quorum sensing (QS) plays an important role in virulence, biofilm formation and survival of many pathogenic bacteria including Pseudomonas aeruginosa. This signalling pathway is considered as novel and promising target for anti-infective agents. In the present investigation, effect of the Sub-MICs of clove oil on QS ...

  3. Artificially Constructed Quorum-Sensing Circuits Are Used for Subtle Control of Bacterial Population Density

    Science.gov (United States)

    Wang, Zhaoshou; Wu, Xin; Peng, Jianghai; Hu, Yidan; Fang, Baishan; Huang, Shiyang

    2014-01-01

    Vibrio fischeri is a typical quorum-sensing bacterium for which lux box, luxR, and luxI have been identified as the key elements involved in quorum sensing. To decode the quorum-sensing mechanism, an artificially constructed cell–cell communication system has been built. In brief, the system expresses several programmed cell-death BioBricks and quorum-sensing genes driven by the promoters lux pR and PlacO-1 in Escherichia coli cells. Their transformation and expression was confirmed by gel electrophoresis and sequencing. To evaluate its performance, viable cell numbers at various time periods were investigated. Our results showed that bacteria expressing killer proteins corresponding to ribosome binding site efficiency of 0.07, 0.3, 0.6, or 1.0 successfully sensed each other in a population-dependent manner and communicated with each other to subtly control their population density. This was also validated using a proposed simple mathematical model. PMID:25119347

  4. Quorum-Quenching Acylase Reduces the Virulence of Pseudomonas aeruginosa in a Caenorhabditis elegans Infection Model

    NARCIS (Netherlands)

    Papaioannou, Evelina; Wahjudi, Mariana; Nadal-Jimenez, Pol; Koch, Gudrun; Setroikromo, Rita; Quax, Wim J.

    2009-01-01

    The Pseudomonas aeruginosa PAO1 gene pvdQ encodes an acyl-homoserine lactone (AHL) acylase capable of degrading N-(3-oxododecanoyl)-L-homoserine lactone by cleaving the AHL amide. PvdQ has been proven to function as a quorum quencher in vitro in a number of phenotypic assays. To address the question

  5. Ligand Binding Kinetics of the Quorum Sensing Regulator PqsR

    DEFF Research Database (Denmark)

    Welch, Martin; Hodgkinson, James T.; Gross, Jeremy

    2013-01-01

    The Pseudomonas aeruginosa quinolone signal (PQS) is a quorum sensing molecule that plays an important role in regulating the virulence of this organism. We have purified the ligand binding domain of the receptor PqsRLBD for PQS and have used Förster resonance energy transfer fluorimetry...

  6. Does “quorum sensing” imply a new type of biological information?

    DEFF Research Database (Denmark)

    Bruni, Luis Emilio

    2002-01-01

    of biological information implied by genetic information with that implied in the concept of “quorum sensing” (which refers to a prokaryotic cell-to-cell communication system) in order to explore if such integration is being achieved. I use the Lux operon paradigm and the Vibrio fischeri – Euprymna scolopes...

  7. Antisense RNA that Affects Rhodopseudomonas palustris Quorum-Sensing Signal Receptor Expression

    Science.gov (United States)

    2012-01-01

    a selectable DNA fragment. Gene 29:303–313. 17. Egland KA, Greenberg EP (1999) Quorum sensing in Vibrio fischeri : Elements of the luxl promoter. Mol...terminal region of the Vibrio fischeri LuxR pro- tein contains an inducer-independent lux gene activating domain. Proc Natl Acad Sci USA 88:11115

  8. Regulation of pqs quorum sensing via catabolite repression control in Pseudomonas aeruginosa

    DEFF Research Database (Denmark)

    Zhang, Lianbo; Gao, Qingguo; Chen, Wanying

    2013-01-01

    that the Pseudomonas aeruginosa catabolite repression control protein regulates the Pseudomonas quinolone signal quorum sensing, which further controls synthesis of virulence factor pyocyanin, biofilm formation and survival during infection models. Our study suggests that deregulation of the catabolite repression by P...

  9. Identification of quorum-sensing regulated proteins in the opportunistic pathogen Pseudomonas aeruginosa by proteomics

    DEFF Research Database (Denmark)

    Arevalo-Ferro, C.; Hentzer, Morten; Reil, G.

    2003-01-01

    The Gram-negative bacterium Pseudomonas aeruginosa is an opportunistic human pathogen which is responsible for severe nosocomial infections in immunocompromised patients and is the major pathogen in cystic fibrosis. The bacterium utilizes two interrelated quorum-sensing (QS) systems, which rely...

  10. Protoanemonin: a natural quorum sensing inhibitor that selectively activates iron starvation response

    NARCIS (Netherlands)

    Fazzini, R.A.; Skindersoe, M.; Bielecki, M.; Puchalka, J.; Givskov, M.; Martins Dos Santos, V.A.P.

    2013-01-01

    Many Gram-negative bacteria employ cell-to-cell communication mediated by N-acyl homoserine lactones (quorum sensing) to control expression of a wide range of genes including, but not limited to, genes encoding virulence factors. Outside the laboratory, the bacteria live in complex communities where

  11. Quorum quenching by an N-acyl-homoserine lactone acylase from Pseudomonas aeruginosa PAO1

    NARCIS (Netherlands)

    Sio, CF; Otten, LG; Cool, RH; Diggle, SP; Braun, PG; Daykin, M; Camara, M; Williams, P; Quax, WJ; Bos, R

    The virulence of the opportunistic human pathogen Pseudomonas aeruginosa PAO1 is controlled by an N-acyl-homoserine lactone (AHL)-dependent quorum-sensing system. During functional analysis of putative acylase genes in the P. aeruginosa PAO1 genome, the PA2385 gene was found to encode an acylase

  12. Pseudomonas aeruginosa tolerance to tobramycin, hydrogen peroxide and polymorphonuclear leukocytes is quorum-sensing dependent

    DEFF Research Database (Denmark)

    Bjarnsholt, Thomas; Jensen, Peter Østrup; Burmølle, Mette

    2005-01-01

    to otherwise lethal doses of antibiotics and are protected from bactericidal activity of polymorphonuclear leukocytes (PMNs). P. aeruginosa controls the expression of many of its virulence factors by means of a cell-cell communication system termed quorum sensing (QS). In the present report it is demonstrated...

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

    Science.gov (United States)

    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...

  14. Disulfide Bond-Containing Ajoene Analogues As Novel Quorum Sensing Inhibitors of Pseudomonas aeruginosa

    DEFF Research Database (Denmark)

    Fong, July; Yuan, Mingjun; Jakobsen, Tim Holm

    2017-01-01

    Since its discovery 22 years ago, the bacterial cell-to-cell communication system, termed quorum sensing (QS), has shown potential as antipathogenic target. Previous studies reported that ajoene from garlic inhibits QS in opportunistic human pathogen Pseudomonas aeruginosa. In this study, screening...

  15. Intra-Species Bacterial Quorum Sensing Studied at Single Cell Level in a Double Droplet Trapping System

    Directory of Open Access Journals (Sweden)

    Wilhelm T. S. Huck

    2013-05-01

    Full Text Available In this paper, we investigated the intra-species bacterial quorum sensing at the single cell level using a double droplet trapping system. Escherichia coli transformed to express the quorum sensing receptor protein, LasR, were encapsulated in microdroplets that were positioned adjacent to microdroplets containing the autoinducer, N-(3-oxododecanoyl-L-homoserine lactone (OdDHL. Functional activation of the LasR protein by diffusion of the OdDHL across the droplet interface was measured by monitoring the expression of green fluorescent protein (GFP from a LasR-dependent promoter. A threshold concentration of OdDHL was found to induce production of quorum-sensing associated GFP by E. coli. Additionally, we demonstrated that LasR-dependent activation of GFP expression was also initiated when the adjacent droplets contained single E. coli transformed with the OdDHL synthase gene, LasI, representing a simple quorum sensing circuit between two droplets.

  16. Cell-Free and In Vivo Characterization of Lux, Las, and Rpa Quorum Activation Systems in E. coli.

    Science.gov (United States)

    Halleran, Andrew D; Murray, Richard M

    2017-11-28

    Synthetic biologists have turned toward quorum systems as a path for building sophisticated microbial consortia that exhibit group decision making. Currently, however, even the most complex consortium circuits rely on only one or two quorum sensing systems, greatly restricting the available design space. High-throughput characterization of available quorum sensing systems is useful for finding compatible sets of systems that are suitable for a defined circuit architecture. Recently, cell-free systems have gained popularity as a test-bed for rapid prototyping of genetic circuitry. We take advantage of the transcription-translation cell-free system to characterize three commonly used Lux-type quorum activators, Lux, Las, and Rpa. We then compare the cell-free characterization to results obtained in vivo. We find significant genetic crosstalk in both the Las and Rpa systems and substantial signal crosstalk in Lux activation. We show that cell-free characterization predicts crosstalk observed in vivo.

  17. Role of the luxS Quorum-Sensing System in Biofilm Formation and Virulence of Staphylococcus epidermidis

    OpenAIRE

    Xu, Lin; Li, Hualin; Vuong, Cuong; Vadyvaloo, Viveka; Wang, Jianping; Yao, Yufeng; Otto, Michael; Gao, Qian

    2006-01-01

    Nosocomial infections caused by Staphylococcus epidermidis are characterized by biofilm formation on implanted medical devices. Quorum-sensing regulation plays a major role in the biofilm development of many bacterial pathogens. Here, we describe luxS, a quorum-sensing system in staphylococci that has a significant impact on biofilm development and virulence. We constructed an isogenic ΔluxS mutant strain of a biofilm-forming clinical isolate of S. epidermidis and demonstrated that luxS signa...

  18. Effects of temperature and salinity on prevalence and intensity of infection of blue crabs, Callinectes sapidus, by Vibrio cholerae, V. parahaemolyticus, and V. vulnificus in Louisiana.

    Science.gov (United States)

    Sullivan, Timothy J; Neigel, Joseph E

    2018-01-01

    Coastal marine and estuarine environments are experiencing higher average temperatures, greater frequency of extreme temperature events, and altered salinities. These changes are expected to stress organisms and increase their susceptibility to infectious diseases. However, beyond these generalities, little is known about how environmental factors influence host-pathogen relationships in the marine realm. We investigated the prevalence and intensity of infections by Vibrio cholerae, V. parahaemolyticus, and V. vulnificus in blue crabs, Callinectes sapidus, from Louisiana saltmarshes in relation to temperature and salinity. We evaluated relationships for single measurements taken at the time of collection and for more complex measurements representing accumulated exposure to physiologically-stressful environmental conditions for up to 31 days prior to collection. We found that: (1) prevalence of infection varied across the Louisiana coast, (2) prevalence of all three Vibrio species was influenced by temperature and salinity, and (3) measurements that represent accumulated exposure to extreme conditions are useful predictors of infection prevalence and can provide insights into underlying biological mechanisms. Copyright © 2017 Elsevier Inc. All rights reserved.

  19. Quorum sensing in Rhizobium sp. strain NGR234 regulates conjugal transfer (tra) gene expression and influences growth rate.

    Science.gov (United States)

    He, Xuesong; Chang, William; Pierce, Deanne L; Seib, Laura Ort; Wagner, Jennifer; Fuqua, Clay

    2003-02-01

    Rhizobium sp. strain NGR234 forms symbiotic, nitrogen-fixing nodules on a wide range of legumes via functions largely encoded by the plasmid pNGR234a. The pNGR234a sequence revealed a region encoding plasmid replication (rep) and conjugal transfer (tra) functions similar to those encoded by the rep and tra genes from the tumor-inducing (Ti) plasmids of Agrobacterium tumefaciens, including homologues of the Ti plasmid quorum-sensing regulators TraI, TraR, and TraM. In A. tumefaciens, TraI, a LuxI-type protein, catalyzes synthesis of the acylated homoserine lactone (acyl-HSL) N-3-oxo-octanoyl-L-homoserine lactone (3-oxo-C8-HSL). TraR binds 3-oxo-C8-HSL and activates expression of Ti plasmid tra and rep genes, increasing conjugation and copy number at high population densities. TraM prevents this activation under noninducing conditions. Although the pNGR234a TraR, TraI, and TraM appear to function similarly to their A. tumefaciens counterparts, the TraR and TraM orthologues are not cross-functional, and the quorum-sensing systems have differences. NGR234 TraI synthesizes an acyl-HSL likely to be 3-oxo-C8-HSL, but traI mutants and a pNGR234a-cured derivative produce low levels of a similar acyl-HSL and another, more hydrophobic signal molecule. TraR activates expression of several pNGR234a tra operons in response to 3-oxo-C8-HSL and is inhibited by TraM. However, one of the pNGR234a tra operons is not activated by TraR, and conjugal efficiency is not affected by TraR and 3-oxo-C8-HSL. The growth rate of NGR234 is significantly decreased by TraR and 3-oxo-C8-HSL through functions encoded elsewhere in the NGR234 genome.

  20. The CpAL Quorum Sensing System Regulates Production of Hemolysins CPA and PFO To Build Clostridium perfringens Biofilms

    Science.gov (United States)

    Shak, Joshua R.; Canizalez-Roman, Adrian

    2015-01-01

    Clostridium perfringens strains produce severe diseases, including myonecrosis and enteritis necroticans, in humans and animals. Diseases are mediated by the production of potent toxins that often damage the site of infection, e.g., skin epithelium during myonecrosis. In planktonic cultures, the regulation of important toxins, such as CPA, CPB, and PFO, is controlled by the C. perfringens Agr-like (CpAL) quorum sensing (QS) system. Strains also encode a functional LuxS/AI-2 system. Although C. perfringens strains form biofilm-like structures, the regulation of biofilm formation is poorly understood. Therefore, our studies investigated the role of CpAL and LuxS/AI-2 QS systems and of QS-regulated factors in controlling the formation of biofilms. We first demonstrate that biofilm production by reference strains differs depending on the culture medium. Increased biomass correlated with the presence of extracellular DNA in the supernatant, which was released by lysis of a fraction of the biofilm population and planktonic cells. Whereas ΔagrB mutant strains were not able to produce biofilms, a ΔluxS mutant produced wild-type levels. The transcript levels of CpAL-regulated cpa and pfoA genes, but not cpb, were upregulated in biofilms compared to planktonic cultures. Accordingly, Δcpa and ΔpfoA mutants, in type A (S13) or type C (CN3685) backgrounds, were unable to produce biofilms, whereas CN3685Δcpb made wild-type levels. Biofilm formation was restored in complemented Δcpa/cpa and ΔpfoA/pfoA strains. Confocal microscopy studies further detected CPA partially colocalizing with eDNA on the biofilm structure. Thus, CpAL regulates biofilm formation in C. perfringens by increasing levels of certain toxins required to build biofilms. PMID:25824838

  1. Anti-quorum Sensing and Anti-biofilm Activity of Delftia tsuruhatensis Extract by Attenuating the Quorum Sensing-Controlled Virulence Factor Production in Pseudomonas aeruginosa

    Directory of Open Access Journals (Sweden)

    Vijay K. Singh

    2017-07-01

    Full Text Available Multidrug-resistance bacteria commonly use cell-to-cell communication that leads to biofilm formation as one of the mechanisms for developing resistance. Quorum sensing inhibition (QSI is an effective approach for the prevention of biofilm formation. A Gram-negative bacterium, Delftia tsuruhatensis SJ01, was isolated from the rhizosphere of a species of sedge (Cyperus laevigatus grown along the coastal-saline area. The isolate SJ01 culture and bacterial crude extract showed QSI activity in the biosensor plate containing the reference strain Chromobacterium violaceum CV026. A decrease in the violacein production of approximately 98% was detected with the reference strain C. violaceum CV026. The bacterial extract (strain SJ01 exhibited anti-quorum sensing activity and inhibited the biofilm formation of clinical isolates wild-type Pseudomonas aeruginosa PAO1 and P. aeruginosa PAH. A non-toxic effect of the bacterial extract (SJ01 was detected on the cell growth of the reference strains as P. aeruginosa viable cells were present within the biofilm. It is hypothesized that the extract (SJ01 may change the topography of the biofilm and thus prevent bacterial adherence on the biofilm surface. The extract also inhibits the motility, virulence factors (pyocyanin and rhamnolipid and activity (elastase and protease in P. aeruginosa treated with SJ01 extract. The potential active compound present was identified as 1,2-benzenedicarboxylic acid, diisooctyl ester. Microarray and transcript expression analysis unveiled differential expression of quorum sensing regulatory genes. The key regulatory genes, LasI, LasR, RhlI, and RhlR were down-regulated in the P. aeruginosa analyzed by quantitative RT-PCR. A hypothetical model was generated of the transcriptional regulatory mechanism inferred in P. aeruginosa for quorum sensing, which will provide useful insight to develop preventive strategies against the biofilm formation. The potential active compound identified

  2. Encapsulated fusion protein confers "sense and respond" activity to chitosan-alginate capsules to manipulate bacterial quorum sensing.

    Science.gov (United States)

    Gupta, Apoorv; Terrell, Jessica L; Fernandes, Rohan; Dowling, Matthew B; Payne, Gregory F; Raghavan, Srinivasa R; Bentley, William E

    2013-02-01

    We demonstrate that "nanofactory"-loaded biopolymer capsules placed in the midst of a bacterial population can direct bacterial communication. Quorum sensing (QS) is a process by which bacteria communicate through small-molecules, such as autoinducer-2 (AI-2), leading to collective behaviors such as virulence and biofilm formation. In our approach, a "nanofactory" construct is created, which comprises an antibody complexed with a fusion protein that produces AI-2. These nanofactories are entrapped within capsules formed by electrostatic complexation of cationic (chitosan) and anionic (sodium alginate) biopolymers. The chitosan capsule shell is crosslinked by tripolyphosphate (TPP) to confer structural integrity. The capsule shell is impermeable to the encapsulated nanofactories, but freely permeable to small molecules. In turn, the capsules are able to take in substrates from the external medium via diffusion, and convert these via the nanofactories into AI-2, which then diffuses out. The exported AI-2 is shown to stimulate QS responses in vicinal Escherichia coli. Directing bacterial population behavior has potential applications in next-generation antimicrobial therapy and pathogen detection. We also envision such capsules to be akin to artificial "cells" that can participate in native biological signaling and communicate in real-time with the human microbiome. Through such interaction capabilities, these "cells" may sense the health of the microbiome, and direct its function in a desired, host-friendly manner. Copyright © 2012 Wiley Periodicals, Inc.

  3. Quorum sensing is a language of chemical signals and plays an ecological role in algal-bacterial interactions.

    Science.gov (United States)

    Zhou, Jin; Lyu, Yihua; Richlen, Mindy; Anderson, Donald M; Cai, Zhonghua

    2016-01-01

    Algae are ubiquitous in the marine environment, and the ways in which they interact with bacteria are of particular interest in marine ecology field. The interactions between primary producers and bacteria impact the physiology of both partners, alter the chemistry of their environment, and shape microbial diversity. Although algal-bacterial interactions are well known and studied, information regarding the chemical-ecological role of this relationship remains limited, particularly with respect to quorum sensing (QS), which is a system of stimuli and response correlated to population density. In the microbial biosphere, QS is pivotal in driving community structure and regulating behavioral ecology, including biofilm formation, virulence, antibiotic resistance, swarming motility, and secondary metabolite production. Many marine habitats, such as the phycosphere, harbour diverse populations of microorganisms and various signal languages (such as QS-based autoinducers). QS-mediated interactions widely influence algal-bacterial symbiotic relationships, which in turn determine community organization, population structure, and ecosystem functioning. Understanding infochemicals-mediated ecological processes may shed light on the symbiotic interactions between algae host and associated microbes. In this review, we summarize current achievements about how QS modulates microbial behavior, affects symbiotic relationships, and regulates phytoplankton chemical ecological processes. Additionally, we present an overview of QS-modulated co-evolutionary relationships between algae and bacterioplankton, and consider the potential applications and future perspectives of QS.

  4. A novel chemical inducer of Streptococcus quorum sensing acts by inhibiting the pheromone-degrading endopeptidase PepO.

    Science.gov (United States)

    Pérez Morales, Tiara G; Ratia, Kiira; Wang, Duo-Sheng; Gogos, Artemis; Driver, Tom G; Federle, Michael J

    2017-12-04

    Bacteria produce chemical signals (pheromones) to coordinate behaviors across a population in a process termed quorum sensing (QS). QS systems comprising peptide pheromones and their corresponding Rgg receptors are widespread among Firmicutes and may be useful targets for manipulating microbial behaviors, like suppressing virulence. The Rgg2/3 QS circuit of the human pathogen Streptococcus pyogenes controls genes affecting resistance to host lysozyme in response to short hydrophobic pheromones (SHPs). Considering that artificial activation of a QS pathway may be as useful in the objective of manipulating bacteria as inhibiting it, we sought to identify small-molecule inducers of the Rgg2/3 QS system. We report the identification of a small molecule, P516-0475, that specifically induced expression of Rgg2/3-regulated genes in the presence of SHP pheromones at concentrations lower than typically required for QS induction. In searching for the mode of action of P516-0475, we discovered that an S. pyogenes mutant deficient in pepO, a neprilysin-like metallo-endopeptidase that degrades SHP pheromones, was unresponsive to the compound. P516-0475 directly inhibited recombinant PepO in vitro as an uncompetitive inhibitor. We conclude that this compound induces QS by stabilizing SHP pheromones in culture. Our study indicates the usefulness of cell-based screens that modulate pathway activities to identify unanticipated therapeutic targets contributing to QS signaling. Copyright © 2017, The American Society for Biochemistry and Molecular Biology.

  5. Isolation and characterization of quorum-sensing signalling molecules in Pseudomonas aeruginosa isolates recovered from nosocomial infections.

    Science.gov (United States)

    Lakshmana Gowda, Krishnappa; John, James; Marie, Mohammed A M; Sangeetha, Gopalkrishnan; Bindurani, Shanta Range

    2013-09-01

    Pseudomonas aeruginosa is one of the most common pathogens in nosocomial infections. Many studies have documented the role of quorum-sensing (QS) systems in antibiotic tolerance of P. aeruginosa. N-acyl homoserine lactones (AHLs) serve as QS signalling molecules and can be a target for modulating bacterial pathogenicity. In this study, nosocomial isolates of P. aeruginosa were characterized for the presence of different types of QS signalling molecules. AHLs were solvent extracted and quantified by determination of β-galactosidase activity using the Escherichia coli MG4 reporter strain. Further characterization was performed by analytical thin layer chromatography coupled with detection using the Agrobacterium tumefaciens A136 biosensor strain. All P. aeruginosa isolates produced AHLs, but there were differences in the quantity and nature of AHLs. We identified AHLs belonging to C4-homoserine lactone (HSL), C6-HSL, C8-HSL, C10-HSL and C12-HSL. AHL profiling of P. aeruginosa isolates showed differences in the amounts and types of AHLs, suggesting differences in the virulence factors and the potential for infection. Our results may be investigated further using animal model systems. © 2013 APMIS. Published by John Wiley & Sons Ltd.

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

    Science.gov (United States)

    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

    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

  7. Quorum sensing systems differentially regulate the production of phenazine-1-carboxylic acid in the rhizobacterium Pseudomonas aeruginosa PA1201.

    Science.gov (United States)

    Sun, Shuang; Zhou, Lian; Jin, Kaiming; Jiang, Haixia; He, Ya-Wen

    2016-07-26

    Pseudomonas aeruginosa strain PA1201 is a newly identified rhizobacterium that produces high levels of the secondary metabolite phenazine-1-carboxylic acid (PCA), the newly registered biopesticide Shenqinmycin. PCA production in liquid batch cultures utilizing a specialized PCA-promoting medium (PPM) typically occurs after the period of most rapid growth, and production is regulated in a quorum sensing (QS)-dependent manner. PA1201 contains two PCA biosynthetic gene clusters phz1 and phz2; both clusters contribute to PCA production, with phz2 making a greater contribution. PA1201 also contains a complete set of genes for four QS systems (LasI/LasR, RhlI/RhlR, PQS/MvfR, and IQS). By using several methods including gene deletion, the construction of promoter-lacZ fusion reporter strains, and RNA-Seq analysis, this study investigated the effects of the four QS systems on bacterial growth, QS signal production, the expression of phz1 and phz2, and PCA production. The possible mechanisms for the strain- and condition-dependent expression of phz1 and phz2 were discussed, and a schematic model was proposed. These findings provide a basis for further genetic engineering of the QS systems to improve PCA production.

  8. Diverse Profiles of AI-1 Type Quorum Sensing Molecules in Cultivable Bacteria from the Mangrove (Kandelia obovata Rhizosphere Environment

    Directory of Open Access Journals (Sweden)

    Zhiping Ma

    2016-12-01

    Full Text Available Mangrove rhizosphere environment harbors diverse populations of microbes, and some evidence showed that rhizobacteria behavior was regulated by quorum sensing (QS. Investigating the diverse profiles of QS molecules in mangrove ecosystems may shed light on the bacterial roles and lead to a better understanding of the symbiotic interactions between plants and microbes. The aims of the current study focus on identifying AI-1 type QS signals, i.e. acyl homoserine lactones (AHLs, in Kandelia obovata rhizosphere environment. Approximately 1200 rhizobacteria were screened and 184 strains (15.3% tested were positive. Subsequent 16s rRNA gene sequencing and dereplication analyses identified 24 species from the positive isolates, which were affiliated to three different phyla, including Proteobacteria, Firmicutes and Actinobacteria. Thin-layer chromatography (TLC separation of extracts revealed diverse AHL profiles and detected at least one active compound in the supernatant of these 24 cultivable AHL-producers. The active extracts from these bacterial isolates were further evaluated by ultra performance liquid chromatography-mass spectrometry (UPLC-MS, and the carbon side chain length ranged from C4 to C14. This is the first report on the diversity of AI-1 type auto-inducers in the mangrove plant K. obovata, and it is imperative to expand our knowledge of plant-bacteria interactions with respect to the maintenance of wetland ecosystem health.

  9. Pseudomonas aeruginosa from canine otitis externa exhibit a quorum sensing deficiency.

    Science.gov (United States)

    Tron, E A M; Wilke, H L; Petermann, S R; Rust, L

    2004-04-05

    Pseudomonas aeruginosa LasB elastase gene (lasB) transcription depends on cell density-dependent quorum-sensing mechanisms of gene activation. Previously, we collected several non-mucoid P. aeruginosa veterinary isolates and showed that the total matrix protease phenotype was similar for isolates regardless of host and site of isolation. In contrast, isolates from chronic canine ear infections (otitis externa) were significantly more likely to exhibit less elastase activity as measured by elastin Congo red than from any other site [Clin. Diag. Lab. Immun. 8 (2001) 632]. In this study, we found that the elastase deficiency phenotype is stable upon passage in broth culture. Transcript amplification analyses indicated that the elastase deficiency appears to be strain-specific, with each isolate exhibiting a unique expression profile relative to strain PAO1. Although a number of strain-specific transcriptional differences were observed, the overall pattern that emerges is a quorum sensing deficiency among canine ear P. aeruginosa isolates.

  10. Quorum system and random based asynchronous rendezvous protocol for cognitive radio ad hoc networks

    Directory of Open Access Journals (Sweden)

    Sylwia Romaszko

    2013-12-01

    Full Text Available This paper proposes a rendezvous protocol for cognitive radio ad hoc networks, RAC2E-gQS, which utilizes (1 the asynchronous and randomness properties of the RAC2E protocol, and (2 channel mapping protocol, based on a grid Quorum System (gQS, and taking into account channel heterogeneity and asymmetric channel views. We show that the combination of the RAC2E protocol with the grid-quorum based channel mapping can yield a powerful RAC2E-gQS rendezvous protocol for asynchronous operation in a distributed environment assuring a rapid rendezvous between the cognitive radio nodes having available both symmetric and asymmetric channel views. We also propose an enhancement of the protocol, which uses a torus QS for a slot allocation, dealing with the worst case scenario, a large number of channels with opposite ranking lists.

  11. Engineered Control of Genetic Variability Reveals Interplay among Quorum Sensing, Feedback Regulation, and Biochemical Noise.

    Science.gov (United States)

    Boada, Yadira; Vignoni, Alejandro; Picó, Jesús

    2017-10-20

    Stochastic fluctuations in gene expression trigger both beneficial and harmful consequences for cell behavior. Therefore, achieving a desired mean protein expression level while minimizing noise is of interest in many applications, including robust protein production systems in industrial biotechnology. Here, we consider a synthetic gene circuit combining intracellular negative feedback and cell-to-cell communication based on quorum sensing. Accounting for both intrinsic and extrinsic noise, stochastic simulations allow us to analyze the capability of the circuit to reduce noise strength as a function of its parameters. We obtain mean expression levels and noise strengths for all species under different scenarios, showing good agreement with system-wide available experimental data of protein abundance and noise in Escherichia coli. Our in silico experiments, validated by preliminary in vivo results, reveal significant noise attenuation in gene expression through the interplay between quorum sensing and negative feedback and highlight the differential role that they play in regard to intrinsic and extrinsic noise.

  12. A broad range quorum sensing inhibitor working through sRNA inhibition

    DEFF Research Database (Denmark)

    Jakobsen, Tim H.; Warming, Anders N.; Vejborg, Rebecca M.

    2017-01-01

    that the repressing effect of ajoene on quorum sensing occurs by inhibition of small regulatory RNAs (sRNA) in P. aeruginosa as well as in Staphylococcus aureus, another important human pathogen that employs quorum sensing to control virulence gene expression. Using various reporter constructs, we found that ajoene...... virulence factors such as hemolysins and proteases were lowered in the presence of ajoene in S. aureus. Importantly, our findings show that sRNAs across bacterial species potentially may qualify as targets of anti-virulence therapy and that ajoene could be a lead structure in search of broad...... lowered expression of the sRNAs RsmY and RsmZ in P. aeruginosa and the small dual-function regulatory RNA, RNAIII in S. aureus, that controls expression of key virulence factors. We confirmed the modulation of RNAIII by RNA sequencing and found that the expression of many QS regulated genes encoding...

  13. The influence of quorum sensing in compartment II of the MELiSSA loop

    Science.gov (United States)

    Condori, Sandra; Mastroleo, Felice; Wattiez, Ruddy; Leys, Natalie

    MELiSSA (Micro-Ecological Life Support System Alternative) has been conceived as a 5 compartments microorganisms and higher plants recycling system for long haul space flights. Rhodospirillum rubrum S1H colonizes compartment II. Previous work reported that continuous culture of the bacterium in a photobioreactor could lead to thick biofilm formation, leading to bioreactor arrest. Our aim is to investigate the unknown quorum sensing (QS) system of R. rubrum S1H, specifically under MELiSSA relevant culture conditions meaning light anaerobic (LAN) and using acetate as carbon source. In that purpose an autoinducer synthase gene (Rru_A3396) knockout mutant was constructed by allelic exchange generating strain M68. In addition phenotypic comparison between wild type (WT) and M68 was performed. Results of thin layer chromatography assay where Agrobacterium tumefaciens NT1 have been used as reporter strain showed that WT produces acyl-homoserine lactones (AHLs) from C4 to C12 acyl carbon chain length; however, in M68 no AHLs were detected confirming that gene Rru_A3396 (named rruI) encodes an autoinducer synthase. Interestingly under a low shear or static environment M68 showed cell aggregation similar as reported in a closely related bacterium Rhodobacter sphaeroides (cerI mutant). In contrast to WT, M68 did not form biofilm and exhibited a decreased motility and pigment content. M68 vs wild type transcriptomics results showed that 326 genes were statistically significant differentially expressed. Downregulation of genes related to photosynthesis e.g., reaction center subunits, light harvesting complex and photosynthetic assembly proteins was observed. Similar results were obtained for preliminary proteomic analysis. Results obtained showed that in R. rubrum S1H the AHL-based QS system regulates almost 8% of the genome which is linked to biofilm formation among other biological processes described above. Since strain M68 could not be used in compartment II due to its less

  14. Roles and Interactions of Burkholderia pseudomallei BpsIR Quorum-Sensing System Determinants▿

    OpenAIRE

    Kiratisin, Pattarachai; Sanmee, Sittinee

    2008-01-01

    The Burkholderia pseudomallei quorum-sensing system (QSS), designated BpsIR, is encoded by five bpsR genes and three bpsI genes. This study investigated the roles and interactions of the QSS determinants in terms of gene regulation and protein interaction. We report two novel findings, that BpsR can function as an activator and a repressor for bpsI expression and that BpsR may form homodimers and heterodimers.

  15. The BpsIR Quorum-Sensing System of Burkholderia pseudomallei

    OpenAIRE

    Song, Yan; Xie, Chao; Ong, Yong-Mei; Gan, Yunn-Hwen; Chua, Kim-Lee

    2005-01-01

    BpsIR, a LuxIR quorum-sensing homolog, is required for optimal expression of virulence and secretion of exoproducts in Burkholderia pseudomallei. Cell density-dependent expression of bpsI and bpsR, the positive regulation of bpsIR expression by BpsR, and the synthesis of N-octanoyl-homoserine lactone (C8HSL) by BpsI are described in this report.

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

    DEFF Research Database (Denmark)

    Kjærulff, Louise; Nielsen, Anita; Månsson, Maria

    2013-01-01

    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....... 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....

  17. Punicalagin Inhibits Salmonella Virulence Factors and Has Anti-Quorum-Sensing Potential

    OpenAIRE

    Li, Guanghui; Yan, Chunhong; Xu, Yunfeng; Feng, Yuqing; Wu, Qian; Lv, Xiaoying; Yang, Baowei; Wang, Xin; Xia, Xiaodong

    2014-01-01

    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...

  18. Identification of Quorum Sensing Signal Molecule of Lactobacillus delbrueckii subsp. bulgaricus.

    Science.gov (United States)

    Pang, Xiaoyang; Liu, Cuiping; Lyu, Pengcheng; Zhang, Shuwen; Liu, Lu; Lu, Jing; Ma, Changlu; Lv, Jiaping

    2016-12-14

    Many bacteria in nature use quorum sensing (QS) to regulate gene expression. The quorum sensing system plays critical roles in the adaptation of bacteria to the surrounding environment. Previous studies have shown that during high-density fermentation, the autolysis of lactic acid bacteria was regulated by the QS system, and the two-component system (TCS, LBUL_RS00115/LBUL_RS00110) is involved in the autolysis of Lactobacillus delbrueckii subsp. bulgaricus. However, the QS signal molecule, which regulates this pathway, has not been identified. In this study, we compared the genome of Lactobacillus bulgaricus ATCC BAA-365 with the locus of seven lactobacillus QS systems; the position of the QS signal molecule of Lactobacillus bulgaricus ATCC BAA-365 was predicted by bioinformatics tool. Its function was identified by in vitro experiments. Construction of TCS mutant by gene knockout of LBUL_RS00115 confirmed that the signal molecule regulates the density of the flora by the TCS (LBUL_RS00115/LBUL_RS00110). This study indicated that quorum quenching and inhibition based on the signal molecule might serve as an approach to reduce the rate of autolysis of LAB and increase the number of live bacteria in fermentation.

  19. Co-evolutionary dynamics of collective action with signaling for a quorum.

    Directory of Open Access Journals (Sweden)

    Jorge M Pacheco

    2015-02-01

    Full Text Available Collective signaling for a quorum is found in a wide range of organisms that face collective action problems whose successful solution requires the participation of some quorum of the individuals present. These range from humans, to social insects, to bacteria. The mechanisms involved, the quorum required, and the size of the group may vary. Here we address the general question of the evolution of collective signaling at a high level of abstraction. We investigate the evolutionary dynamics of a population engaging in a signaling N-person game theoretic model. Parameter settings allow for loners and cheaters, and for costly or costless signals. We find a rich dynamics, showing how natural selection, operating on a population of individuals endowed with the simplest strategies, is able to evolve a costly signaling system that allows individuals to respond appropriately to different states of Nature. Signaling robustly promotes cooperative collective action, in particular when coordinated action is most needed and difficult to achieve. Two different signaling systems may emerge depending on Nature's most prevalent states.

  20. Bacterial bioluminescence onset and quenching: a dynamical model for a quorum sensing-mediated property

    Science.gov (United States)

    Side, Domenico Delle; Nassisi, Vincenzo; Pennetta, Cecilia; Alifano, Pietro; Di Salvo, Marco; Talà, Adelfia; Chechkin, Aleksei; Seno, Flavio

    2017-01-01

    We present an effective dynamical model for the onset of bacterial bioluminescence, one of the most studied quorum sensing-mediated traits. Our model is built upon simple equations that describe the growth of the bacterial colony, the production and accumulation of autoinducer signal molecules, their sensing within bacterial cells, and the ensuing quorum activation mechanism that triggers bioluminescent emission. The model is directly tested to quantitatively reproduce the experimental distributions of photon emission times, previously measured for bacterial colonies of Vibrio jasicida, a luminescent bacterium belonging to the Harveyi clade, growing in a highly drying environment. A distinctive and novel feature of the proposed model is bioluminescence ‘quenching’ after a given time elapsed from activation. Using an advanced fitting procedure based on the simulated annealing algorithm, we are able to infer from the experimental observations the biochemical parameters used in the model. Such parameters are in good agreement with the literature data. As a further result, we find that, at least in our experimental conditions, light emission in bioluminescent bacteria appears to originate from a subtle balance between colony growth and quorum activation due to autoinducers diffusion, with the two phenomena occurring on the same time scale. This finding is consistent with a negative feedback mechanism previously reported for Vibrio harveyi.

  1. Plakofuranolactone as a Quorum Quenching Agent from the Indonesian Sponge Plakortis cf. lita

    Directory of Open Access Journals (Sweden)

    Valeria Costantino

    2017-02-01

    Full Text Available There is an urgent need for novel strategies to fight drug resistance and multi-drug resistance. As an alternative to the classic antibiotic therapy, attenuation of the bacteria virulence affecting their Quorum sensing (QS system is a promising approach. Quorum sensing (QS is a genetic regulation system that allows bacteria to communicate with each other and coordinate group behaviors. A new γ-lactone that is capable of inhibiting the LasI/R QS system, plakofuranolactone (1, was discovered in the extract of the marine sponge Plakortis cf. lita, and its structure, including absolute configuration, was determined by NMR spectroscopy, MS spectrometry, and quantum-mechanical prediction of optical rotation. The quorum quenching activity of plakofuranolactone was evaluated using reporter gene assays for long- and short-chain signals (E. coli pSB1075, E. coli pSB401, and C. violeaceum CV026 and was confirmed by measuring the total protease activity (a virulence factor which is under control of the LasI/R system of the wild-type P. aeruginosa PAO1. Further research will be pursued to assess the potential of plakofuranolactone as a new antivirulence lead compound and a chemical tool to increase the knowledge in this field.

  2. Bioactive proteins from Solanaceae as quorum sensing inhibitors against virulence in Pseudomonas aeruginosa.

    Science.gov (United States)

    Singh, Gurpreet; Tamboli, Ekant; Acharya, Aurovind; Kumarasamy, Chellan; Mala, Kanchana; Raman, Pachaiappan

    2015-06-01

    Cell-to-cell communication or quorum sensing (QS) is a generic event in bacteria that is used to coordinate gene expression among local populations. The phenomenon of QS depends on the fact that presence of sufficient bacteria ascertains a threshold level of autoinducer concentration that allows bacteria to sense a critical cell mass and to activate or repress target genes. Thus, QS has been an attractive target for the development of anti-infective strategies that are not based on the use of antibiotics. Several anti-QS approaches have been demonstrated including natural products from plant-based secondary metabolites. However, the role of plant bioactive proteins as an anti-QS peptide is yet to be deciphered. Against a backdrop of ever-increasing antibiotic resistant pathogens, there is a strong need for development of alternative therapeutic strategies. Thus, our hypothesis is that bioactive proteins from the plant family Solanaceae are quorum quenching molecules that can be exploited to develop a therapeutic strategy against virulence. We presume that bioactive proteins will inactivate or inhibit or degrade QS signals from bacteria to prevent cell-to-cell communication and thus inhibit development of virulence in Pseudomonas aeruginosa. Further, the use of proteins as quorum quenchers will delay the bacteria to develop resistance against these quenching molecules. Copyright © 2015 Elsevier Ltd. All rights reserved.

  3. Spatial dispersal of bacterial colonies induces a dynamical transition from local to global quorum sensing

    Science.gov (United States)

    Yusufaly, Tahir I.; Boedicker, James Q.

    2016-12-01

    Bacteria communicate using external chemical signals called autoinducers (AI) in a process known as quorum sensing (QS). QS efficiency is reduced by both limitations of AI diffusion and potential interference from neighboring strains. There is thus a need for predictive theories of how spatial community structure shapes information processing in complex microbial ecosystems. As a step in this direction, we apply a reaction-diffusion model to study autoinducer signaling dynamics in a single-species community as a function of the spatial distribution of colonies in the system. We predict a dynamical transition between a local quorum sensing (LQS) regime, with the AI signaling dynamics primarily controlled by the local population densities of individual colonies, and a global quorum sensing (GQS) regime, with the dynamics being dependent on collective intercolony diffusive interactions. The crossover between LQS to GQS is intimately connected to a trade-off between the signaling network's latency, or speed of activation, and its throughput, or the total spatial range over which all the components of the system communicate.

  4. The putative oligosaccharide translocase SypK connects biofilm formation with quorum signaling in Vibrio fischeri.

    Science.gov (United States)

    Miyashiro, Tim; Oehlert, Dane; Ray, Valerie A; Visick, Karen L; Ruby, Edward G

    2014-12-01

    Quorum signaling (QS) describes how bacteria can use small signaling molecules (autoinducers) to coordinate group-level behaviors. In Vibrio fischeri, QS is achieved through a complex regulatory network that ultimately controls bioluminescence, motility, and host colonization. We conducted a genetic screen focused on qrr1, which encodes a small regulatory RNA that is necessary for the core quorum-signaling cascade to transduce autoinducer information into cellular responses. We isolated unique mutants with a transposon inserted into one of two genes within the syp locus, which is involved in biofilm formation. We found that overexpression of sypK, which encodes a putative oligosaccharide translocase, is sufficient to activate qrr1, and, in addition, this effect appears to depend on the kinase activity of the sensor LuxQ. Consistent with the established model for QS in V. fischeri, enhanced expression of qrr1 by the overexpression of sypK resulted in reduced bioluminescence and increased motility. Finally, we found that induction of the syp locus by overexpression of sypG was sufficient to activate qrr1 levels. Together, our results show how conditions that promote biofilm formation impact the quorum-signaling network in V. fischeri, and further highlight the integrated nature of the regulatory circuits involved in complex bacterial behaviors. © 2014 The Authors. MicrobiologyOpen published by John Wiley & Sons Ltd.

  5. Rule–based regulatory and metabolic model for Quorum sensing in P. aeruginosa

    Science.gov (United States)

    2013-01-01

    Background In the pathogen P. aeruginosa, the formation of virulence factors is regulated via Quorum sensing signaling pathways. Due to the increasing number of strains that are resistant to antibiotics, there is a high interest to develop novel antiinfectives. In the combat of resistant bacteria, selective blockade of the bacterial cell–to–cell communication (Quorum sensing) has gained special interest as anti–virulence strategy. Here, we modeled the las, rhl, and pqs Quorum sensing systems by a multi–level logical approach to analyze how enzyme inhibitors and receptor antagonists effect the formation of autoinducers and virulence factors. Results Our rule–based simulations fulfill the behavior expected from literature considering the external level of autoinducers. In the presence of PqsBCD inhibitors, the external HHQ and PQS levels are indeed clearly reduced. The magnitude of this effect strongly depends on the inhibition level. However, it seems that the pyocyanin pathway is incomplete. Conclusions To match experimental observations we suggest a modified network topology in which PqsE and PqsR acts as receptors and an autoinducer as ligand that up–regulate pyocyanin in a concerted manner. While the PQS biosynthesis is more appropriate as target to inhibit the HHQ and PQS formation, blocking the receptor PqsR that regulates the biosynthesis reduces the pyocyanin level stronger. PMID:23965312

  6. KARAKTERISASI BAKTERI ANTI QUORUM SENSING (AQS SEBAGAI PENGHAMBAT VIRULENSI PENYAKIT PADA IKAN LELE DUMBO (Clarias gariepinus

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    Hessy Novita

    2015-03-01

    Full Text Available Penyakit bakterial adalah salah satu penyebab kerugian besar di bidang akuakultur. Faktor virulensi bakteri penyakit umumnya diekspresikan oleh gen-gen virulen yang diregulasi dengan sistem Quorum Sensing. Tujuan dari penelitian ini adalah untuk mendapatkan isolat bakteri yang memiliki potensi sebagai Anti Quorum Sensing (AQS yang dapat menghambat faktor virulensi bakteri patogen penyebab penyakit pada ikan lele dumbo (Clarias gariepinus. Isolasi bakteri dilakukan dari sedimen, organ pencernaan dan air kolam ikan lele dumbo dari Parung, Ciampea, dan Gunung Sindur, Bogor, Jawa Barat. Sebanyak 347 isolat bakteri berhasil diisolasi, dan sebanyak 68 (19% isolat di antaranya mempunyai aktivitas AQS dengan empat isolat yang berpotensi sebagai bakteri AQS yaitu: TS 1 dan TS 2, TA 23, dan TY 33. Empat isolat tersebut teridentifikasi berdasarkan sekuen 16S rRNA sebagai Bacillus amyloliquefaciens, Lysinnibacillus sphaericus, Lysinnibacillus fusiformis, dan Bacillus cereus dengan persentase kemiripan masing-masing 93%, 99%, dan 100%. Berdasarkan analisa gen AHL (Acyl Homoserine Lactone laktonase (aiiA, keempat isolat tersebut menghasilkan enzim AHL. Hasil studi ini menunjukkan bahwa isolat bakteri hasil isolasi dari kolam ikan lele dumbo dapat menghambat mekanisme Quorum Sensing bakteri patogen ikan dengan mendegradasi autoinduser-nya yang berupa AHL.

  7. Imidazolines as Non-Classical Bioisosteres of N-Acyl homoserine lactones and Quorum Sensing Inhibitors

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    Mabel Montenegro-Sustaita

    2012-01-01

    Full Text Available 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 µM 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 µM. 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 µM, until reaching 100 µM, 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 μM.

  8. Heterogeneous response to a quorum-sensing signal in the luminescence of individual Vibrio fischeri.

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    Pablo Delfino Pérez

    Full Text Available 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.

  9. AI-2 does not function as a quorum sensing molecule in Campylobacter jejuni during exponential growth in vitro

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    Winzer Klaus

    2009-10-01

    Full Text Available Abstract Background Campylobacter jejuni contains a homologue of the luxS gene shown to be responsible for the production of the signalling molecule autoinducer-2 (AI-2 in Vibrio harveyi and Vibrio cholerae. The aim of this study was to determine whether AI-2 acted as a diffusible quorum sensing signal controlling C. jejuni gene expression when it is produced at high levels during mid exponential growth phase. Results AI-2 activity was produced by the parental strain NCTC 11168 when grown in rich Mueller-Hinton broth (MHB as expected, but interestingly was not present in defined Modified Eagles Medium (MEM-α. Consistent with previous studies, the luxS mutant showed comparable growth rates to the parental strain and exhibited decreased motility halos in both MEM-α and MHB. Microarray analysis of genes differentially expressed in wild type and luxS mutant strains showed that many effects on mRNA transcript abundance were dependent on the growth medium and linked to metabolic functions including methionine metabolism. Addition of exogenously produced AI-2 to the wild type and the luxS mutant, growing exponentially in either MHB or MEM-α did not induce any transcriptional changes as analysed by microarray. Conclusion Taken together these results led us to conclude that there is no evidence for the role of AI-2 in cell-to-cell communication in C. jejuni strain NCTC 11168 under the growth conditions used, and that the effects of the luxS mutation on the transcriptome are related to the consequential loss of function in the activated methyl cycle.

  10. Recipient-induced transfer of the symbiotic plasmid pRL1JI in Rhizobium leguminosarum bv. viciae is regulated by a quorum-sensing relay.

    Science.gov (United States)

    Danino, Vittoria E; Wilkinson, Adam; Edwards, Anne; Downie, J Allan

    2003-10-01

    Analysis of the regulation of plasmid transfer genes on the symbiotic plasmid pRL1JI in Rhizobium leguminosarum bv. viciae has revealed a novel regulatory relay that is specifically poised to detect an N-acyl-homoserine lactone (AHL) made by different cells (potential recipients of pRL1JI). Adjacent to the traI-trbBCDEJKLFGHI plasmid transfer operon on pRL1JI are two regulatory genes, bisR and traR, which encode LuxR-type quorum-sensing regulators required for conjugation. Potential recipients of pRL1JI induce the traI-trb operon and plasmid transfer via a quorum-sensing relay involving BisR, TraR and the traI-trb operon in donor cells. BisR induces expression of traR in response to N-(3-hydroxy-7-cis-tetradecenoyl)-l-homoserine lactone (3-OH-C14:1-HSL), which is produced by CinI in potential recipient strains. In donor strains (carrying pRL1JI), BisR represses the expression of the chromosomal gene cinI; this repression results in a very low level of formation of 3-OH-C14:1-HSL and hence relatively low levels of expression of traR and the traI-trb operon in strains carrying pRL1JI. However, if 3-OH-C14:1-HSL from potential recipients is present, then traR and plasmid transfer are induced. The induction of traR occurs at very low concentrations of 3-OH-C14:1-HSL (around 1 nm). TraR then induces the traI-trb operon in a quorum-sensing dependent manner in re-sponse to the TraI-made AHLs, N-(3-oxo-octanoyl)-l-homoserine lactone and N-(octanoyl)-l-homoserine lactone. The resulting autoinduction results in high levels of expression of the traI-trb operon. Premature expression of the traI-trb operon is reduced by TraM, which probably titres out TraR preventing expression of traI when there are low levels of traR expression. Expression of traR in stationary phase cells is limited by feedback inhibition mediated by TraI-made AHLs.

  11. Reducing virulence of the human pathogen Burkholderia by altering the substrate specificity of the quorum-quenching acylase PvdQ

    NARCIS (Netherlands)

    Koch, Gudrun; Nadal-Jimenez, Pol; Reis, Carlos R.; Muntendam, Remco; Bokhove, Marcel; Melillo, Elena; Dijkstra, Bauke W.; Cool, Robbert H.; Quax, Wim J.

    2014-01-01

    The use of enzymes to interfere with quorum sensing represents an attractive strategy to fight bacterial infections. We used PvdQ, an effective quorum-quenching enzyme from Pseudomonas aeruginosa, as a template to generate an acylase able to effectively hydrolyze C8-HSL, the major communication

  12. DqsIR quorum sensing-mediated gene regulation of the extremophilic bacterium Deinococcus radiodurans in response to oxidative stress.

    Science.gov (United States)

    Lin, Lin; Dai, Shang; Tian, Bing; Li, Tao; Yu, Jiangliu; Liu, Chengzhi; Wang, Liangyan; Xu, Hong; Zhao, Ye; Hua, Yuejin

    2016-05-01

    Here, we show that AHLs can be employed by Deinococcus radiodurans, which belongs to the unique phylum Deinococcus-Thermus and is known for its cellular resistance to environmental stresses. An AHL-mediated quorum-sensing system (DqsI/DqsR) was identified in D. radiodurans. We found that under non-stress conditions, the AHL level was "shielded" by quorum quenching enzymes, whereas AHLs accumulated when D. radiodurans was exposed to oxidative stress. Upon exposure to H2 O2 , AHL synthetic enzymes (DqsI) were immediately induced, while the expression of quorum-quenching enzymes began to increase approximately 30 min after exposure to H2 O2 , as shown by time-course analyses of gene expression. Both dqsI mutant (DMDqsI) and dqsR mutant (MDqsR) were more sensitive to oxidative stress compared with the wild-type strain. Exogenous AHLs (5 μM) could completely restore the survival fraction of DMDqsI under oxidative stress. RNA-seq analysis showed that a number of genes involved in stress-response, cellular cleansing, and DNA repair had altered transcriptional levels in MDqsR. The DqsR, acting as a regulator of quorum sensing, controls gene expression along with AHLs. Hence, the DqsIR-mediated quorum sensing that mediates gene regulation is an adaptive strategy for D. radiodurans in response to oxidative stresses and is conserved in the extremophilic Deinococcus bacteria. © 2016 John Wiley & Sons Ltd.

  13. Expression and Quorum Sensing Regulation of Type III Secretion System Genes of Vibrio harveyi during Infection of Gnotobiotic Brine Shrimp

    Science.gov (United States)

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

    2015-01-01

    Type III secretion systems enable pathogens to inject their virulence factors directly into the cytoplasm of the host cells. The type III secretion system of Vibrio harveyi, a major pathogen of aquatic organisms and a model species in quorum sensing studies, is repressed by the quorum sensing master regulator LuxR. In this study, we found that during infection of gnotobiotic brine shrimp larvae, the expression levels of three type III secretion operons in V. harveyi increased within the first 12h after challenge and decreased again thereafter. The in vivo expression levels were highest in a mutant with a quorum sensing system that is locked in low cell density configuration (minimal LuxR levels) and lowest in a mutant with a quorum sensing system that is locked in the high cell density configuration (maximal LuxR levels), which is consistent with repression of type III secretion by LuxR. Remarkably, in vivo expression levels of the type III secretion system genes were much (> 1000 fold) higher than the in vitro expression levels, indicating that (currently unknown) host factors significantly induce the type III secretion system. Given the fact that type III secretion is energy-consuming, repression by the quorum sensing master regulators might be a mechanism to save energy under conditions where it does not provide an advantage to the cells. PMID:26636765

  14. Quorum Sensing N-acyl Homoserine Lactones-SdiA Suppresses Escherichia coli-Pseudomonas aeruginosa Conjugation through Inhibiting traI Expression.

    Science.gov (United States)

    Lu, Yang; Zeng, Jianming; Wu, Binning; E, Shunmei; Wang, Lina; Cai, Renxin; Zhang, Ni; Li, Youqiang; Huang, Xianzhang; Huang, Bin; Chen, Cha

    2017-01-01

    Conjugation is a key mechanism for horizontal gene transfer and plays an important role in bacterial evolution, especially with respect to antibiotic resistance. However, little is known about the role of donor and recipient cells in regulation of conjugation. Here, using an Escherichia coli (SM10λπ)-Pseudomonas aeruginosa (PAO1) conjugation model, we demonstrated that deficiency of lasI/rhlI, genes associated with generation of the quorum sensing signals N-acyl homoserine lactones (AHLs) in PAO1, or deletion of the AHLs receptor SdiA in the donor SM10λπ both facilitated conjugation. When using another AHLs-non-producing E. coli strain EC600 as recipient cells, deficiency of sdiA in donor SM10λπ hardly affect the conjugation. More importantly, in the presence of exogenous AHLs, the conjugation efficiency between SM10λπ and EC600 was dramatically decreased, while deficiency of sdiA in SM10λπ attenuated AHLs-inhibited conjugation. These data suggest the conjugation suppression function of AHLs-SdiA chemical signaling. Further bioinformatics analysis, β-galactosidase reporter system and electrophoretic mobility shift assays characterized the binding site of SdiA on the promoter region of traI gene. Furthermore, deletion of lasI/rhlI or sdiA promoted traI mRNA expression in SM10λπ and PAO1 co-culture system, which was abrogated by AHLs. Collectively, our results provide new insight into an important contribution of quorum sensing system AHLs-SdiA to the networks that regulate conjugation.

  15. Modulating the Global Response Regulator, LuxO of V. cholerae Quorum Sensing System Using a Pyrazine Dicarboxylic Acid Derivative (PDCApy: An Antivirulence Approach

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    M. Hema

    2017-10-01

    Full Text Available Vibrio cholerae is a Gram-negative pathogen which causes acute diarrhoeal disease, cholera by the expression of virulence genes through quorum sensing (QS mechanism. The QS circuit of V. cholerae is controlled by the global quorum regulator, LuxO, which at low cell density (LCD state produces major virulence factors such as, toxin co-regulated pilus (TCP and cholera toxin (CT to mediate infection. On the contrary, at the high cell density (HCD state the virulent genes are downregulated and the vibrios are detached from the host intestinal epithelial cells, promoted by HapA protease. Hence, targeting the global regulator LuxO would be a promising approach to modulate the QS to curtail V. cholerae pathogenesis. In our earlier studies, LuxO targeted ligand, 2,3 pyrazine dicarboxylic acid (PDCA and its derivatives having desired pharmacophore properties were chemically synthesized and were shown to have biofilm inhibition as well as synergistic activity with the conventionally used antibiotics. In the present study, the QS modulatory effect of the PDCA derivative with pyrrolidine moiety designated as PDCApy against the V. cholerae virulence gene expression was analyzed at various growth phases. The data significantly showed a several fold reduction in the expression of the genes, tcp and ct whereas the expression of hapR was upregulated at the LCD state. In addition, PDCApy reduced the adhesion and invasion of the vibrios onto the INT407 intestinal cell lines. Collectively, our data suggest that PDCApy could be a potential QS modulator (QSM for the antivirulence therapeutic approach.

  16. Inter-kingdom Signaling by the Legionella Quorum Sensing Molecule LAI-1 Modulates Cell Migration through an IQGAP1-Cdc42-ARHGEF9-Dependent Pathway.

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    Sylvia Simon

    2015-12-01

    Full Text Available Small molecule signaling promotes the communication between bacteria as well as between bacteria and eukaryotes. The opportunistic pathogenic bacterium Legionella pneumophila employs LAI-1 (3-hydroxypentadecane-4-one for bacterial cell-cell communication. LAI-1 is produced and detected by the Lqs (Legionella quorum sensing system, which regulates a variety of processes including natural competence for DNA uptake and pathogen-host cell interactions. In this study, we analyze the role of LAI-1 in inter-kingdom signaling. L. pneumophila lacking the autoinducer synthase LqsA no longer impeded the migration of infected cells, and the defect was complemented by plasmid-borne lqsA. Synthetic LAI-1 dose-dependently inhibited cell migration, without affecting bacterial uptake or cytotoxicity. The forward migration index but not the velocity of LAI-1-treated cells was reduced, and the cell cytoskeleton appeared destabilized. LAI-1-dependent inhibition of cell migration involved the scaffold protein IQGAP1, the small GTPase Cdc42 as well as the Cdc42-specific guanine nucleotide exchange factor ARHGEF9, but not other modulators of Cdc42, or RhoA, Rac1 or Ran GTPase. Upon treatment with LAI-1, Cdc42 was inactivated and IQGAP1 redistributed to the cell cortex regardless of whether Cdc42 was present or not. Furthermore, LAI-1 reversed the inhibition of cell migration by L. pneumophila, suggesting that the compound and the bacteria antagonistically target host signaling pathway(s. Collectively, the results indicate that the L. pneumophila quorum sensing compound LAI-1 modulates migration of eukaryotic cells through a signaling pathway involving IQGAP1, Cdc42 and ARHGEF9.

  17. Inter-kingdom Signaling by the Legionella Quorum Sensing Molecule LAI-1 Modulates Cell Migration through an IQGAP1-Cdc42-ARHGEF9-Dependent Pathway.

    Science.gov (United States)

    Simon, Sylvia; Schell, Ursula; Heuer, Natalie; Hager, Dominik; Albers, Michael F; Matthias, Jan; Fahrnbauer, Felix; Trauner, Dirk; Eichinger, Ludwig; Hedberg, Christian; Hilbi, Hubert

    2015-12-01

    Small molecule signaling promotes the communication between bacteria as well as between bacteria and eukaryotes. The opportunistic pathogenic bacterium Legionella pneumophila employs LAI-1 (3-hydroxypentadecane-4-one) for bacterial cell-cell communication. LAI-1 is produced and detected by the Lqs (Legionella quorum sensing) system, which regulates a variety of processes including natural competence for DNA uptake and pathogen-host cell interactions. In this study, we analyze the role of LAI-1 in inter-kingdom signaling. L. pneumophila lacking the autoinducer synthase LqsA no longer impeded the migration of infected cells, and the defect was complemented by plasmid-borne lqsA. Synthetic LAI-1 dose-dependently inhibited cell migration, without affecting bacterial uptake or cytotoxicity. The forward migration index but not the velocity of LAI-1-treated cells was reduced, and the cell cytoskeleton appeared destabilized. LAI-1-dependent inhibition of cell migration involved the scaffold protein IQGAP1, the small GTPase Cdc42 as well as the Cdc42-specific guanine nucleotide exchange factor ARHGEF9, but not other modulators of Cdc42, or RhoA, Rac1 or Ran GTPase. Upon treatment with LAI-1, Cdc42 was inactivated and IQGAP1 redistributed to the cell cortex regardless of whether Cdc42 was present or not. Furthermore, LAI-1 reversed the inhibition of cell migration by L. pneumophila, suggesting that the compound and the bacteria antagonistically target host signaling pathway(s). Collectively, the results indicate that the L. pneumophila quorum sensing compound LAI-1 modulates migration of eukaryotic cells through a signaling pathway involving IQGAP1, Cdc42 and ARHGEF9.

  18. The quorum sensing regulator CinR hierarchically regulates two other quorum sensing pathways in ligand-dependent and -independent fashions in Rhizobium etli.

    Science.gov (United States)

    Zheng, Huiming; Mao, Yiling; Zhu, Qingcheng; Ling, Jun; Zhang, Na; Naseer, Nawar; Zhong, Zengtao; Zhu, Jun

    2015-05-01

    Many rhizobial species use complex N-acyl-homoserine lactone (AHL)-based quorum sensing (QS) systems to monitor their population density and regulate their symbiotic interactions with their plant hosts. There are at least three LuxRI-type regulatory systems in Rhizobium etli CFN42: CinRI, RaiRI, and TraRI. In this study, we show that CinI, RaiI, and TraI are responsible for synthesizing all AHLs under the tested conditions. The activation of these AHL synthase genes requires their corresponding LuxR-type counterparts. We further demonstrate that CinRI is at the top of the regulatory cascade that activates RaiRI and TraRI QS systems. Moreover, we discovered that CinR possesses a specific affinity to bind cinI promoter in the absence of its cognate AHL ligand, thereby activating cinI transcription. Addition of AHLs leads to improved binding to the cinI promoter and enhanced cinI expression. Furthermore, we found that compared to the wild type, the cinR mutation displayed reduced nodule formation, and cinR, raiR, and traI mutants show significantly lower levels of nitrogen fixation activity than the wild type. These results suggest that the complex QS regulatory systems in R. etli play an important role in its symbiosis with legume hosts. Many bacteria use quorum sensing (QS) to monitor their cell densities and coordinately regulate a number of physiological functions. Rhizobia often have diverse and complex LuxR/LuxI-type quorum sensing systems that may be involved in symbiosis and N2 fixation. In this study, we identified three LuxR/LuxI-type QS systems in Rhizobium etli CFN42: CinRI, RaiRI, and TraRI. We established a complex network of regulation between these QS components and found that these QS systems played important roles in symbiosis processes. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

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

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    Grace Chong

    Full Text Available 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.

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

    Science.gov (United States)

    Chong, Grace; Kimyon, Önder; Manefield, Mike

    2013-01-01

    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

  1. Pseudomonas aeruginosa quorum-sensing signal molecules interfere with dendritic cell-induced T-cell proliferation

    DEFF Research Database (Denmark)

    Skindersø, Mette Elena; Zeuthen, Louise; Pedersen, Susanne Brix

    2009-01-01

    Pseudomonas aeruginosa releases a wide array of toxins and tissue-degrading enzymes. Production of these malicious virulence factors is controlled by interbacterial communication in a process known as quorum sensing. An increasing body of evidence reveals that the bacterial signal molecule N-(3......-oxododecanoyl)-l-homoserine lactone (OdDHL) exhibits both quorum-sensing signalling and immune-modulating properties. Recently, yet another quorum-sensing signal molecule, the Pseudomonas quinolone signal (PQS), has been shown to affect cytokine release by mitogen-stimulated human T cells. In the present...... article we demonstrate that both OdDHL and PQS decrease the production of interleukin-12 (IL-12) by Escherichia coli lipopolysaccharide-stimulated bone marrow-derived dendritic cells (BM-DCs) without altering their IL-10 release. Moreover, BM-DCs exposed to PQS and OdDHL during antigen stimulation exhibit...

  2. Secondary Metabolites Produced during the Germination of Streptomyces coelicolor

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    Matouš Čihák

    2017-12-01

    Full Text Available Spore awakening is a series of actions that starts with purely physical processes and continues via the launching of gene expression and metabolic activities, eventually achieving a vegetative phase of growth. In spore-forming microorganisms, the germination process is controlled by intra- and inter-species communication. However, in the Streptomyces clade, which is capable of developing a plethora of valuable compounds, the chemical signals produced during germination have not been systematically studied before. Our previously published data revealed that several secondary metabolite biosynthetic genes are expressed during germination. Therefore, we focus here on the secondary metabolite production during this developmental stage. Using high-performance liquid chromatography-mass spectrometry, we found that the sesquiterpenoid antibiotic albaflavenone, the polyketide germicidin A, and chalcone are produced during germination of the model streptomycete, S. coelicolor. Interestingly, the last two compounds revealed an inhibitory effect on the germination process. The secondary metabolites originating from the early stage of microbial growth may coordinate the development of the producer (quorum sensing and/or play a role in competitive microflora repression (quorum quenching in their nature environments.

  3. Model for end-stage liver disease (MELD score as a predictor and monitor of mortality in patients with Vibrio vulnificus necrotizing skin and soft tissue infections.

    Directory of Open Access Journals (Sweden)

    Kuo-Chin Huang

    2015-04-01

    Full Text Available Vibrio vulnificus necrotizing skin and soft tissue infections (VNSSTIs usually predispose patients with or without preexisting liver disease to septic shock, and then evolve to multiple organ dysfunction syndrome (MODS, thus resulting in high mortality in humans. However, clinicians do not have a valid prediction model to provide a reliable estimate of case-fatality rate when caring for these acutely and/or critically ill patients.We retrospectively analyzed 39 consecutive patients with VNSSTIs (mean age: 65.7 ± 11.3 years at our institution between 2007 and 2010. All patients were treated with the same protocol. Demographic and clinical characteristics, disease severity on admission, treatment details, and outcomes were collected for each patient and extracted for analyses. We studied the predictive value of the model for end-stage liver disease (MELD, modified MELD including sodium (MELD-Na, and laboratory risk indicator for necrotizing fasciitis (LRINEC scores for case-fatality. Logistic regression and receiver operating characteristic (ROC curve analyses were performed. The mean MELD, MELD-Na and LRINEC scores on admission were 15.1 ± 1.1, 17.7 ± 1.1, and 3.4 ± 0.4 points, respectively. After admission, these patients had temporary or progressive deterioration of nearly all their scores and lab values. The area under the ROC curve for the MELD and ΔMELD scoring models were 0.929 (p = 0.002 and 0.897 (p = 0.005, respectively. An optimal MELD/ΔMELD cutoff value ≥ 20/2 had a good sensitivity and specificity (all > 80%, with a 64/13-fold increased odds for case-fatality. Additionally, the development of severe forms of anemia (p = 0.014 and hypoalbuminemia (p = 0.019 were associated with an increased case-fatality rate.The MELD/ΔMELD scoring model is an effective risk stratification indicator at the time of admission and also an excellent condition monitor during hospitalization for medical care of acutely and/or critically ill patients

  4. Quorum Quenching and Microbial Control through Phenolic Extract of Eugenia Uniflora Fruits.

    Science.gov (United States)

    Rodrigues, Adeline Conceição; Zola, Flávia Guimarães; Ávila Oliveira, Brígida D'; Sacramento, Nayara Thais Barbosa; da Silva, Elis Regina; Bertoldi, Michele Corrêa; Taylor, Jason Guy; Pinto, Uelinton Manoel

    2016-10-01

    We describe the characterization of the centesimal composition, mineral and phenolic content of Eugenia uniflora fruit and the determination of the antioxidant, antimicrobial and quorum quenching activities of the pulp phenolic extract. Centesimal composition was determined according to standard methods; trace elements were measured by total reflection X-ray fluorescence spectroscopy. The phenolic compounds were extracted by solid-phase chromatography and quantified by spectrophotometry. Antioxidant activity was determined by using 3 different methods. Antimicrobial activity was evaluated against a panel of foodborne microorganisms and antiquorum sensing activity in Chromobacterium violaceum was performed by measuring inhibition of quorum sensing dependent violacein production. The centesimal composition (per 100 g of pulp) was as follows: protein 3.68 ± 0.21 g, lipids 0.02 ± 0.03 g, carbohydrates 10.31 g and fiber 2.06 g. Trace elements (mg/g of pulp) were determined as: K 0.90, Ca 3.36, Fe 0.60, Zn 0.17, Cl 0.56, Cr 0.06, Ni 0.04, and Cu 0.07. The pulp is a source of phenolic compounds and presents antioxidant activity similar to other berries. The fruit phenolic extract inhibited all tested bacteria. We also found that the fruit phenolic extract at low subinhibitory concentrations inhibited up to 96% of violacein production in C. violaceum, likely due to the fruit's phenolic content. This study shows the contribution of E. uniflora phenolic compounds to the antioxidant, antimicrobial and the newly discovered quorum quenching activity, all of which could be used by the food and pharmaceutical industries to develop new functional products. © 2016 Institute of Food Technologists®.

  5. Pharmacological inhibition of quorum sensing for the treatment of chronic bacterial infections

    DEFF Research Database (Denmark)

    Hentzer, Morten; Givskov, Michael Christian

    2003-01-01

    Traditional treatment of infectious diseases is based on compounds that aim to kill or inhibit bacterial growth. A major concern with this approach is the frequently observed development of resistance to antimicrobial compounds. The discovery of bacterial-communication systems (quorum......-sensing systems), which orchestrate important temporal events during the infection process, has afforded a novel opportunity to ameliorate bacterial infection by means other than growth inhibition. Compounds able to override bacterial signaling are present in nature. Herein we discuss the known signaling...

  6. Piper nigrum, Piper betle and Gnetum gnemon- Natural Food Sourcewith Anti-Quorum Sensing Properties

    OpenAIRE

    Li Ying Tan; Wai-Fong Yin; Kok-Gan Chan

    2013-01-01

    Various parts of Piper nigrum, Piper betle and Gnetum gnemon are used as food sources by Malaysians. The purpose of this study is to examine the anti-quorum sensing (anti-QS) properties of P. nigrum, P. betle and G. gnemon extracts. The hexane, chloroform and methanol extracts of these plants were assessed in bioassays involving Pseudomonas aeruginosa PA01, Escherichia coli [pSB401], E. coli [pSB1075] and Chromobacterium violaceum CV026. It was found that the extracts of these three plants ha...

  7. Eugenol exhibits anti-virulence properties by competitively binding to quorum sensing receptors.

    Science.gov (United States)

    Rathinam, Prasanth; Vijay Kumar, H S; Viswanathan, Pragasam

    2017-09-01

    The primary objective of this study was to ascertain the anti-biofilm and anti-virulence properties of sub-minimum inhibitory concentration (MIC) levels of eugenol against the standard strain PAO1 and two multi-drug resistant P. aeruginosa clinical isolates utilizing quorum sensing inhibition (QSI). Eugenol at 400 μM significantly reduced biofilm formation on urinary catheters and the virulence factors (VF) including extracellular polysaccharides, rhamnolipid, elastase, protease, pyocyanin, and pyoverdine (p associated genes besides the VF genes (p < 0.001). This study provides insights, for the first time, into the mechanism of the anti-virulence properties of eugenol.

  8. Effects of ambroxol on biofilm adhesion and viability of Pseudomonas aeruginosa quorum sensing defective strain

    OpenAIRE

    Lu, Qi; Hai-ying ZHONG; Lin, Li-Hua; Ya-yin LIN; Xi-qiang YANG; Yu, Jia-Lin

    2013-01-01

    Objective To investigate the effects of ambroxol on the biofilm viability and pristine adhesion of Pseudomonas aeruginosa wild (PAO1) and quorum sensing defective strain (QS, gene deletion of ∆lasI and ∆rhlI). Methods The biofilm was treated by different concentrations (0, 1.875, 3.75mg/ml) of ambroxol. The number of colony was measured with agar plate, multifunction fluorometer was used to measure the fluorescence intensity of PAO1 and QS strains at the bottom of 96-well plate. The adhesion ...

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

    Science.gov (United States)

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

    2015-12-01

    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. Copyright © 2014 Elsevier Ltd. All rights reserved.

  10. Solonamide B Inhibits Quorum Sensing and Reduces Staphylococcus aureus Mediated Killing of Human Neutrophils

    DEFF Research Database (Denmark)

    Nielsen, Anita; Månsson, Maria; Bojer, Martin S.

    2014-01-01

    Methicillin-resistant Staphylococcus aureus (MRSA) continues to be a serious human pathogen, and particularly the spread of community associated (CA)-MRSA strains such as USA300 is a concern, as these strains can cause severe infections in otherwise healthy adults. Recently, we reported...... that a cyclodepsipeptide termed Solonamide B isolated from the marine bacterium, Photobacterium halotolerans strongly reduces expression of RNAIII, the effector molecule of the agr quorum sensing system. Here we show that Solonamide B interferes with the binding of S. aureus autoinducing peptides (AIPs) to sensor......A controlled virulence gene expression in S. aureus....

  11. Garlic blocks quorum sensing and promotes rapid clearing of pulmonary Pseudomonas aeruginosa infections

    DEFF Research Database (Denmark)

    Bjarnsholt, Thomas; Jensen, Peter Østrup; Rasmussen, Thomas B

    2005-01-01

    The opportunistic human pathogen Pseudomonas aeruginosa is the predominant micro-organism of chronic lung infections in cystic fibrosis patients. P. aeruginosa colonizes the lungs by forming biofilm microcolonies throughout the lung. Quorum sensing (QS) renders the biofilm bacteria highly tolerant......-treated biofilm. Garlic extract was administered as treatment for a mouse pulmonary infection model. Mice were treated with garlic extract or placebo for 7 days, with the initial 2 days being prophylactic before P. aeruginosa was instilled in the left lung of the mice. Bacteriology, mortality, histopathology...... and phagocytosis by PMNs, as well as leading to an improved outcome of pulmonary infections....

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

    Science.gov (United States)

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

    2015-02-01

    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 μg/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.

  13. You are what you talk: quorum sensing induces individual morphologies and cell division modes in Dinoroseobacter shibae.

    Science.gov (United States)

    Patzelt, Diana; Wang, Hui; Buchholz, Ina; Rohde, Manfred; Gröbe, Lothar; Pradella, Silke; Neumann, Alexander; Schulz, Stefan; Heyber, Steffi; Münch, Karin; Münch, Richard; Jahn, Dieter; Wagner-Döbler, Irene; Tomasch, Jürgen

    2013-12-01

    Dinoroseobacter shibae, a member of the Roseobacter clade abundant in marine environments, is characterized by a pronounced pleomorphism. Cell shapes range from variable-sized ovoid rods to long filaments with a high copy number of chromosomes. Time-lapse microscopy shows cells dividing either by binary fission or by budding from the cell poles. Here we demonstrate that this morphological heterogeneity is induced by quorum sensing (QS). D. shibae utilizes three acylated homoserine lactone (AHL) synthases (luxI1-3) to produce AHLs with unsaturated C18 side chains. A ΔluxI1-knockout strain completely lacking AHL biosynthesis was uniform in morphology and divided by binary fission only. Transcriptome analysis revealed that expression of genes responsible for control of cell division was reduced in this strain, providing the link between QS and the observed phenotype. In addition, flagellar biosynthesis and type IV secretion system (T4SS) were downregulated. The wild-type phenotype and gene expression could be restored through addition of synthetic C18-AHLs. Their effectiveness was dependent on the number of double bonds in the acyl side chain and the regulated trait. The wild-type expression level of T4SS genes was fully restored even by an AHL with a saturated C18 side chain that has not been detected in D. shibae. QS induces phenotypic individualization of D. shibae cells rather than coordinating the population. This strategy might be beneficial in unpredictably changing environments, for example, during algal blooms when resource competition and grazing exert fluctuating selective pressures. A specific response towards non-native AHLs might provide D. shibae with the capacity for complex interspecies communication.

  14. Isoprenyl caffeate, a major compound in manuka propolis, is a quorum-sensing inhibitor in Chromobacterium violaceum.

    Science.gov (United States)

    Gemiarto, Adrian Tandhyka; Ninyio, Nathaniel Nyakaat; Lee, Siew Wei; Logis, Joko; Fatima, Ayesha; Chan, Eric Wei Chiang; Lim, Crystale Siew Ying

    2015-08-01

    The emergence of antibiotic-resistant bacterial pathogens, especially Gram-negative bacteria, has driven investigations into suppressing bacterial virulence via quorum sensing (QS) inhibition strategies instead of bactericidal and bacteriostatic approaches. Here, we investigated several bee products for potential compound(s) that exhibit significant QS inhibitory (QSI) properties at the phenotypic and molecular levels in Chromobacterium violaceum ATCC 12472 as a model organism. Manuka propolis produced the strongest violacein inhibition on C. violaceum lawn agar, while bee pollen had no detectable QSI activity and honey had bactericidal activity. Fractionated manuka propolis (pooled fraction 5 or PF5) exhibited the largest violacein inhibition zone (24.5 ± 2.5 mm) at 1 mg dry weight per disc. In C. violaceum liquid cultures, at least 450 µg/ml of manuka propolis PF5 completely inhibited violacein production. Gene expression studies of the vioABCDE operon, involved in violacein biosynthesis, showed significant (≥two-fold) down-regulation of vioA, vioD and vioE in response to manuka propolis PF5. A potential QSI compound identified in manuka propolis PF5 is a hydroxycinnamic acid-derivative, isoprenyl caffeate, with a [M-H] of 247. Complete violacein inhibition in C. violaceum liquid cultures was achieved with at least 50 µg/ml of commercial isoprenyl caffeate. In silico docking experiments suggest that isoprenyl caffeate may act as an inhibitor of the violacein biosynthetic pathway by acting as a competitor for the FAD-binding pockets of VioD and VioA. Further studies on these compounds are warranted toward the development of anti-pathogenic drugs as adjuvants to conventional antibiotic treatments, especially in antibiotic-resistant bacterial infections.

  15. Vanadium bromoperoxidase from Delisea pulchra: enzyme-catalyzed formation of bromofuranone and attendant disruption of quorum sensing.

    Science.gov (United States)

    Sandy, Moriah; Carter-Franklin, Jayme N; Martin, Jessica D; Butler, Alison

    2011-11-28

    Vanadium bromoperoxidase was isolated and cloned from the marine red alga Delisea pulchra. This enzyme catalyzes the bromolactonization of 4-pentynoic acid forming 5E-bromo-methylidenetetrahydro-2-furanone, a compound which is shown herein to inhibit quorum sensing in the engineered reporter strain, Agrobacterium tumefaciens NTL4.

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

    DEFF Research Database (Denmark)

    Wu, H; Song, Z; Hentzer, M

    2004-01-01

    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 regulates bacterial virulence as well as the formation of biofilms opens up new ways...

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

    DEFF Research Database (Denmark)

    Wu, H.; Song, Z.; Hentzer, Morten

    2004-01-01

    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 regulates bacterial virulence as well as the formation of biofilms opens up new ways...

  18. AI-2 does not function as a quorum sensing molecule in Campylobacter jejuni during exponential growth in vitro

    NARCIS (Netherlands)

    Holmes, K.; Tavender, T.J.; Winzer, K.; Wells, J.; Hardie, K.

    2009-01-01

    Background - Campylobacter jejuni contains a homologue of the luxS gene shown to be responsible for the production of the signalling molecule autoinducer-2 (AI-2) in Vibrio harveyi and Vibrio cholerae. The aim of this study was to determine whether AI-2 acted as a diffusible quorum sensing signal

  19. Integration of Metabolic and Quorum Sensing Signals Governing the Decision to Cooperate in a Bacterial Social Trait.

    Science.gov (United States)

    Boyle, Kerry E; Monaco, Hilary; van Ditmarsch, Dave; Deforet, Maxime; Xavier, Joao B

    2015-05-01

    Many unicellular organisms live in multicellular communities that rely on cooperation between cells. However, cooperative traits are vulnerable to exploitation by non-cooperators (cheaters). We expand our understanding of the molecular mechanisms that allow multicellular systems to remain robust in the face of cheating by dissecting the dynamic regulation of cooperative rhamnolipids required for swarming in Pseudomonas aeruginosa. We combine mathematical modeling and experiments to quantitatively characterize the integration of metabolic and population density signals (quorum sensing) governing expression of the rhamnolipid synthesis operon rhlAB. The combined computational/experimental analysis reveals that when nutrients are abundant, rhlAB promoter activity increases gradually in a density dependent way. When growth slows down due to nutrient limitation, rhlAB promoter activity can stop abruptly, decrease gradually or even increase depending on whether the growth-limiting nutrient is the carbon source, nitrogen source or iron. Starvation by specific nutrients drives growth on intracellular nutrient pools as well as the qualitative rhlAB promoter response, which itself is modulated by quorum sensing. Our quantitative analysis suggests a supply-driven activation that integrates metabolic prudence with quorum sensing in a non-digital manner and allows P. aeruginosa cells to invest in cooperation only when the population size is large enough (quorum sensing) and individual cells have enough metabolic resources to do so (metabolic prudence). Thus, the quantitative description of rhlAB regulatory dynamics brings a greater understating to the regulation required to make swarming cooperation stable.

  20. The effect of burdock leaf fraction on adhesion, biofilm formation, quorum sensing and virulence factors of Pseudomonas aeruginosa.

    Science.gov (United States)

    Lou, Z; Wang, H; Tang, Y; Chen, X

    2017-03-01

    This study aimed to evaluate the effect of a fraction of burdock (Arctium lappa L.) leaf on the initial adhesion, biofilm formation, quorum sensing and virulence factors of Pseudomonas aeruginosa. Antibiofilm activity of the burdock leaf fraction was studied by the method of crystal violet staining. When the concentration of the burdock leaf fraction was 2·0 mg ml -1 , the inhibition rates on biofilm formation of P. aeruginosa were 100%. The burdock leaf fraction was found to inhibit the formation of biofilm by reducing bacterial surface hydrophobicity, decreasing bacterial aggregation ability and inhibiting swarming motility. Interestingly, the burdock leaf fraction inhibited the secretion of quorum-sensing (QS) signalling molecule 3-oxo-C12-HSL and interfered quorum sensing. Moreover, the QS-regulated pyocyanin and elastase were also inhibited. Chemical composition analysis by UPLC-MS showed 11 active compounds in the burdock leaf fraction. The burdock leaf fraction significantly inhibited the formation of biofilm and quorum sensing, as well as significantly decreased the content of virulence factors. This study introduces a natural and effective bacterial biofilm inhibitor, which could also significantly decrease the content of virulence factors and the drug resistance of P. aeruginosa. © 2016 The Society for Applied Microbiology.

  1. Programming the quorum sensing-based AND gate in Shewanella oneidensis for logic gated-microbial fuel cells.

    Science.gov (United States)

    Hu, Yidan; Yang, Yun; Katz, Evgeny; Song, Hao

    2015-03-11

    An AND logic gate based on a synthetic quorum-sensing (QS) module was constructed in a Shewanella oneidensis MR-1 mtrA knockout mutant. The presence of two input signals activated the expression of a periplasmic decaheme cytochrome MtrA to regenerate the extracellular electron transfer conduit, enabling the construction of AND-gated microbial fuel cells.

  2. Effects of quorum-sensing on immunoglobulin G responses in a rat model of chronic lung infection with Pseudomonas aeruginosa

    DEFF Research Database (Denmark)

    WU, H.; Song, Z.J.; Givskov, Michael Christian

    2004-01-01

    I, lasI), compared with the wild-type PAO1. Four out of 15 rats infected with wild-type PAO1 contained bacteria in the lungs on day 106, whereas no bacteria were found in the mutant PAO1 group. The results indicate that quorum signals contribute to the persistence of the infection and influence...

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

    NARCIS (Netherlands)

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

    1997-01-01

    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,

  4. Solid‐Phase Synthesis and Biological Evaluation of N‐Dipeptido L‐Homoserine Lactones as Quorum Sensing Activators

    DEFF Research Database (Denmark)

    Hansen, Mette Reimert; Le Quement, Sebastian Thordal; Jakobsen, Tim Holm

    2014-01-01

    Bacteria use small signaling molecules to communicate in a process termed “quorum sensing” (QS), which enables the coordination of survival strategies, such as production of virulence factors and biofilm formation. In Gram‐negative bacteria, these signaling molecules are a series of N‐acylated L...

  5. Biofouling control by biostimulation of quorum-quenching bacteria in a membrane bioreactor for wastewater treatment.

    Science.gov (United States)

    Yu, Huarong; Liang, Heng; Qu, Fangshu; He, Junguo; Xu, Guoren; Hu, Huizhi; Li, Guibai

    2016-12-01

    Bacterial quorum quenching (QQ) has been shown to be effective in controlling biofouling in membrane bioreactors (MBRs) for wastewater treatment. However, the encapsulation of a sufficient level of QQ bacteria is complicated and difficult. In plant research, gamma-caprolactone (GCL), which is structurally similar to the quorum signal, N-acyl homoserine lactone (AHL), was successfully used to specifically stimulate AHL-degrading bacteria (biostimulation) in hydroponic systems to control blackleg and soft rot diseases in potato. In this study, the feasibility of enriching QQ bacteria from activated sludge by GCL was examined, and the effect of biostimulation on biofouling control in MBR treating domestic wastewater was investigated. The results showed that after enrichment with GCL, activated sludge could effectively degrade AHLs, and a QQ gene (qsdA) was augmented. The proposed biostimulation QQ strategy, by introducing and continuously dosing GCL, could significantly increase QQ activity, decrease AHL, control the secretion of extracellular polymeric substances (EPS), and thus, effectively control biofouling in an MBR. This biostimulation QQ strategy provides a more convenient option for biofouling control in MBR applications. Biotechnol. Bioeng. 2016;113: 2624-2632. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  6. Investigating the effect of antibiotics on quorum sensing with whole-cell biosensing systems.

    Science.gov (United States)

    Struss, Anjali K; Pasini, Patrizia; Flomenhoft, Deborah; Shashidhar, Harohalli; Daunert, Sylvia

    2012-04-01

    Quorum sensing (QS) allows bacteria to communicate with one another by means of QS signaling molecules and control certain behaviors in a group-based manner, including pathogenicity and biofilm formation. Bacterial gut microflora may play a role in inflammatory bowel disease pathogenesis, and antibiotics are one of the available therapeutic options for Crohn's disease. In the present study, we employed genetically engineered bioluminescent bacterial whole-cell sensing systems as a tool to evaluate the ability of antibiotics commonly employed in the treatment of chronic inflammatory conditions to interfere with QS. We investigated the effect of ciprofloxacin, metronidazole, and tinidazole on quorum sensing. Several concentrations of individual antibiotics were allowed to interact with two different types of bacterial sensing cells, in both the presence and absence of a fixed concentration of N-acylhomoserine lactone (AHL) QS molecules. The antibiotic effect was then determined by monitoring the biosensor's bioluminescence response. Ciprofloxacin, metronidazole, and tinidazole exhibited a dose-dependent augmentation in the response of both bacterial sensing systems, thus showing an AHL-like effect. Additionally, such an augmentation was observed, in both the presence and absence of AHL. The data obtained indicate that ciprofloxacin, metronidazole, and tinidazole may interfere with bacterial communication systems. The results suggest that these antibiotics, at the concentrations tested, may themselves act as bacterial signaling molecules. The beneficial effect of these antibiotics in the treatment of intestinal inflammation may be due, at least in part, to their effect on QS-related bacterial behavior in the gut.

  7. Silencing quorum sensing and ICE mobility through antiactivation and ribosomal frameshifting.

    Science.gov (United States)

    Ramsay, Joshua P; Ronson, Clive W

    2015-01-01

    Mobile genetic elements run an evolutionary gauntlet to maintain their mobility in the face of selection against their selfish dissemination but, paradoxically, they can accelerate the adaptability of bacteria through the gene-transfer events that they facilitate. These temporally conflicting evolutionary forces have shaped exquisite regulation systems that silence mobility and maximize the competitive fitness of the host bacterium, but maintain the ability of the element to deliver itself to a new host should the opportunity arise. Here we review the excision regulation system of the Mesorhizobium loti symbiosis island ICEMlSymR7A, a 502-kb integrative and conjugative element (ICE) capable of converting non-symbiotic mesorhizobia into plant symbionts. ICEMlSymR7A excision is activated by quorum sensing, however, both quorum sensing and excision are strongly repressed in the vast majority of cells by dual-target antiactivation and programmed ribosomal-frameshifting mechanisms. We examine these recently discovered regulatory features under the light of natural selection and discuss common themes that can be drawn from recent developments in ICE biology.

  8. Modification and Assembly of a Versatile Lactonase for Bacterial Quorum Quenching

    Directory of Open Access Journals (Sweden)

    Melissa K. Rhoads

    2018-02-01

    Full Text Available This work sets out to provide a self-assembled biopolymer capsule activated with a multi-functional enzyme for localized delivery. This enzyme, SsoPox, which is a lactonase and phosphotriesterase, provides a means of interrupting bacterial communication pathways that have been shown to mediate pathogenicity. Here we demonstrate the capability to express, purify and attach SsoPox to the natural biopolymer chitosan, preserving its activity to “neutralize” long-chain autoinducer-1 (AI-1 communication molecules. Attachment is shown via non-specific binding and by engineering tyrosine and glutamine affinity ‘tags’ at the C-terminus for covalent linkage. Subsequent degradation of AI-1, in this case N-(3-oxododecanoyl-l-homoserine lactone (OdDHL, serves to “quench” bacterial quorum sensing (QS, silencing intraspecies communication. By attaching enzymes to pH-responsive chitosan that, in turn, can be assembled into various forms, we demonstrate device-based flexibility for enzyme delivery. Specifically, we have assembled quorum-quenching capsules consisting of an alginate inner core and an enzyme “decorated” chitosan shell that are shown to preclude bacterial QS crosstalk, minimizing QS mediated behaviors.

  9. Label-Free Critical Micelle Concentration Determination of Bacterial Quorum Sensing Molecules

    Science.gov (United States)

    Davis, B.M.; Richens, J.L.; O'Shea, P.

    2011-01-01

    A practical label-free method for the rapid determination of small-molecule critical micelle concentration (CMC) using a fixed-angle light-scattering technique is described. Change in 90° light scattering at a fixed wavelength of incident radiation with increasing bacterial quorum molecule concentration and the observation of a break point is used to determine CMC. In our study, this technique is utilized to investigate the aqueous CMC of previously uncharacterized Pseudomonas aeruginosa quorum sensing signaling molecules (QSSM) belonging to the n-acylhomoserine lactone and 2-alkyl-4-quinolone classes. Several were found to form micelles within a physiologically relevant concentration range and potential roles of these micelles as QSSM transporters are discussed. The influence of temperature and the presence of biological membranes or serum proteins on QSSM CMC are also investigated and evidence is obtained to suggest the QSSMs studied are capable of both membrane and serum protein interaction. This demonstrates that the fixed-angle light-scattering technique outlined can be used simply and rapidly to determine small-molecule CMC under a variety of conditions. PMID:21723835

  10. Spontaneous quorum sensing mutation modulates electroactivity of Pseudomonas aeruginosa PA14.

    Science.gov (United States)

    Berger, Carola; Rosenbaum, Miriam A

    2017-10-01

    Pseudomonas aeruginosa is able to interact with the anode of a bioelectrochemical system through redox active phenazines. Earlier studies showed that this interaction is strain and carbon source dependent. With a spontaneously formed ΔlasR mutant of P. aeruginosa PA14 and the wildtype, we investigated the connection between the complex quorum sensing network and current production. Depending on the carbon source, phenazine production and subsequently current generation are effected differently in these two populations. In glucose-fed cultures, the lack of the LasR regulator led to a shift in phenazine concentration, relative composition, and time profiles. In contrast, with the common fermentation product 2,3-butanediol as carbon substrate, no phenazine production was detected for the ΔlasR mutant. For the wildtype, this carbon source is known to induce phenazine synthesis and elevated current production. This work supports the earlier hypothesis of a signaling link between 2,3-butanediol and the quorum-sensing regulatory system and extends this hypothesis to predict a lasR-dependent interaction. The wildtype and mutant population were also evaluated in direct competition, showing strong initial dominance of the wildtype but a higher survival rate of the ΔlasR mutant in later stages of growth. We found no evidence for strong social interactions between these two subpopulations. Copyright © 2017 Elsevier B.V. All rights reserved.

  11. Mini Review of Phytochemicals and Plant Taxa with Activity as Microbial Biofilm and Quorum Sensing Inhibitors

    Directory of Open Access Journals (Sweden)

    Chieu Anh Kim Ta

    2015-12-01

    Full Text Available Microbial biofilms readily form on many surfaces in nature including plant surfaces. In order to coordinate the formation of these biofilms, microorganisms use a cell-to-cell communication system called quorum sensing (QS. As formation of biofilms on vascular plants may not be advantageous to the hosts, plants have developed inhibitors to interfere with these processes. In this mini review, research papers published on plant-derived molecules that have microbial biofilm or quorum sensing inhibition are reviewed with the objectives of determining the biosynthetic classes of active compounds, their biological activity in assays, and their families of occurrence and range. The main findings are the identification of plant phenolics, including benzoates, phenyl propanoids, stilbenes, flavonoids, gallotannins, proanthocyanidins and coumarins as important inhibitors with both activities. Some terpenes including monoterpenes, sesquiterpenes, diterpenes and triterpenes also have anti-QS and anti-biofilm activities. Relatively few alkaloids were reported. Quinones and organosulfur compounds, especially from garlic, were also active. A common feature is the polar nature of these compounds. Phytochemicals with these activities are widespread in Angiosperms in temperate and tropical regions, but gymnosperms, bryophytes and pteridophytes were not represented.

  12. Quorum Sensing Inhibition and Structure–Activity Relationships of β-Keto Esters

    Directory of Open Access Journals (Sweden)

    Stephanie Forschner-Dancause

    2016-07-01

    Full Text Available Traditional therapeutics to treat bacterial infections have given rise to multi-drug resistant pathogens, which pose a major threat to human and animal health. In several pathogens, quorum sensing (QS—a cell-cell communication system in bacteria—controls the expression of genes responsible for pathogenesis, thus representing a novel target in the fight against bacterial infections. Based on the structure of the autoinducers responsible for QS activity and other QS inhibitors, we hypothesize that β-keto esters with aryl functionality could possess anti-QS activity. A panel of nineteen β-keto ester analogs was tested for the inhibition of bioluminescence (a QS-controlled phenotype in the marine pathogen Vibrio harveyi. Initial screening demonstrated the need of a phenyl ring at the C-3 position for antagonistic activity. Further additions to the phenyl ring with 4-substituted halo groups or a 3- or 4-substituted methoxy group resulted in the most active compounds with IC50 values ranging from 23 µM to 53 µM. The compounds additionally inhibit green fluorescent protein production by E. coli JB525. Evidence is presented that aryl β-keto esters may act as antagonists of bacterial quorum sensing by competing with N-acyl homoserine lactones for receptor binding. Expansion of the β-keto ester panel will enable us to obtain more insight into the structure–activity relationships needed to allow for the development of novel anti-virulence agents.

  13. Role of the quorum-sensing system in experimental pneumonia due to Pseudomonas aeruginosa in rats.

    Science.gov (United States)

    Lesprit, Philippe; Faurisson, Francois; Join-Lambert, Olivier; Roudot-Thoraval, Francoise; Foglino, Maryline; Vissuzaine, Christiane; Carbon, Claude

    2003-06-01

    The virulence of Pseudomonas aeruginosa is partly controlled by the las quorum-sensing system. A rat model of acute pneumonia was used to investigate the pathophysiological impact of this system by comparing the virulence of the wild-type virulent laboratory strain PAO1 with that of its lasR-deleted mutant PAOR. In comparison with PAO1, PAOR was avirulent after an instillation of 106 cfu (mortality rates, 72 versus 0%, respectively; p < 0.0001). A ten-fold higher inoculum slightly increased the mortality rate induced by PAOR (25%), which remained lower than that induced by PAO1 (75%, p = 0.0001). In addition, with both inocula lung and bronchoalveolar lavage bacterial counts were significantly lower in rats infected with PAOR than with PAO1 (p quorum-sensing system has an important role in the pathophysiology of P. aeruginosa pulmonary infection.

  14. EFFECTS OF PSYCHOTROPIC DRUGS AS BACTERIAL EFFLUX PUMP INHIBITORS ON QUORUM SENSING REGULATED BEHAVIORS

    Directory of Open Access Journals (Sweden)

    Aynur Aybey

    2014-10-01

    Full Text Available Psychotropic drugs are known to have antimicrobial activity against several groups of microorganisms. The antidepressant agents such as duloxetine, paroxetine, hydroxyzine and venlafaxine are shown to act as efflux pump inhibitors in bacterial cells. In order to the investigation of the effects of psychotropic drugs were determined for clinically significant pathogens by using standart broth microdillusion method. The anti-quorum sensing (anti-QS activity of psychotropic drugs was tested against four test pathogens using the agar well diffusion method. All drugs showed strong inhibitory effect on the growth of S. typhimurium. Additionally, quorum sensing-regulated behaviors of Pseudomonas aeruginosa, including swarming, swimming and twitching motility and alkaline protease production were investigated. Most effective drugs on swarming, swimming and twitching motility and alkaline protease production, respectively, were paroxetine and duloxetine; duloxetine; hydroxyzine and venlafaxine; paroxetine and venlafaxine; venlafaxine. Accordingly, psychotropic drugs were shown strongly anti-QS activity by acting as bacterial efflux pump inhibitors and effection on motility and alkaline protease production of P. aeruginosa.

  15. Effects of ambroxol on biofilm adhesion and viability of Pseudomonas aeruginosa quorum sensing defective strain

    Directory of Open Access Journals (Sweden)

    Qi LU

    2013-07-01

    Full Text Available Objective To investigate the effects of ambroxol on the biofilm viability and pristine adhesion of Pseudomonas aeruginosa wild (PAO1 and quorum sensing defective strain (QS, gene deletion of ∆lasI and ∆rhlI. Methods The biofilm was treated by different concentrations (0, 1.875, 3.75mg/ml of ambroxol. The number of colony was measured with agar plate, multifunction fluorometer was used to measure the fluorescence intensity of PAO1 and QS strains at the bottom of 96-well plate. The adhesion ratio (% was calculated to determine the effects of ambroxol on bacterial biofilm adhesion. Results Ambroxol treatment reduced the survival rate of the mutant strains compared to that of wild strain, even though the QS strain had increased the adhesion in the presence of ambroxol compared to that of wild strain (P<0.05. Conclusion Ambroxol has a property of significantly antagonizing quorum-sensing system, suggesting that it might be of importance in treatment against chronic Pseudomonasaeruginosainfections.

  16. Estimation of spatial distribution of quorum sensing signaling in sequencing batch biofilm reactor (SBBR) biofilms.

    Science.gov (United States)

    Wang, Jinfeng; Ding, Lili; Li, Kan; Huang, Hui; Hu, Haidong; Geng, Jinju; Xu, Ke; Ren, Hongqiang

    2018-01-15

    Quorum sensing (QS) signaling, plays a significant role in regulating formation of biofilms in the nature; however, little information about the occurrence and distribution of quorum sensing molecular in the biofilm of carriers has been reported. In this study, distribution of QS signaling molecules (the acylated homoserine lactones-AHLs, and AI-2), extracellular polymeric substances (EPS) and the mechanical properties in sequencing batch biofilm reactor (SBBR) biofilms have been investigated. Using increased centrifugal force, the biofilms were detached into different fractions. The AHLs ranged from 5.2ng/g to 98.3ng/g in different fractions of biofilms, and N-decanoyl-dl-homoserine lactone (C10-HSL) and N-dodecanoyl-dl-homoserine lactone (C12-HSL) in the biofilms obtained at various centrifugal forces displayed significant differences (pbiofilms ranged from 79.2ng/g to 98.3ng/g. Soluble EPS and loosely bound EPS content in the different fractions of biofilms displayed significant positive relationship with the distribution of C12-HSL (r=0.86, pbiofilms were positively related with AHLs with 22.76% was significantly positively (pBiofilm adhesion and compliance was the strongest in the tightly-bound biofilm, the weakest in the supernatant/surface biofilm, which was in accordance with the distribution of C12 HSL(r=0.77, pbiofilm application. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. A quorum-sensing factor in vegetative Dictyostelium discoideum cells revealed by quantitative migration analysis.

    Science.gov (United States)

    Golé, Laurent; Rivière, Charlotte; Hayakawa, Yoshinori; Rieu, Jean-Paul

    2011-01-01

    Many cells communicate through the production of diffusible signaling molecules that accumulate and once a critical concentration has been reached, can activate or repress a number of target genes in a process termed quorum sensing (QS). In the social amoeba Dictyostelium discoideum, QS plays an important role during development. However little is known about its effect on cell migration especially in the growth phase. To investigate the role of cell density on cell migration in the growth phase, we use multisite timelapse microscopy and automated cell tracking. This analysis reveals a high heterogeneity within a given cell population, and the necessity to use large data sets to draw reliable conclusions on cell motion. In average, motion is persistent for short periods of time (t ≤ 5 min), but normal diffusive behavior is recovered over longer time periods. The persistence times are positively correlated with the migrated distances. Interestingly, the migrated distance decreases as well with cell density. The adaptation of cell migration to cell density highlights the role of a secreted quorum sensing factor (QSF) on cell migration. Using a simple model describing the balance between the rate of QSF generation and the rate of QSF dilution, we were able to gather all experimental results into a single master curve, showing a sharp cell transition between high and low motile behaviors with increasing QSF. This study unambiguously demonstrates the central role played by QSF on amoeboid motion in the growth phase.

  18. Organ-level quorum sensing directs regeneration in hair stem cell populations

    Science.gov (United States)

    Chen, Chih-Chiang; Wang, Lei; Plikus, Maksim V.; Jiang, Ting Xin; Murray, Philip J.; Ramos, Raul; Guerrero-Juarez, Christian F.; Hughes, Michael W; Lee, Oscar K.; Shi, Songtao; Widelitz, Randall B.; Lander, Arthur D.; Chuong, Cheng Ming

    2015-01-01

    SUMMARY Coordinated organ behavior is crucial for an effective response to environmental stimuli. By studying regeneration of hair follicles in response to patterned hair removal, we demonstrate that organ-level quorum sensing allows coordinated responses to skin injury. Removing hair at different densities leads to a regeneration of up to 5 times more neighboring, unplucked resting hairs, indicating activation of a collective decision-making process. Through data modeling, the range of the quorum signal was estimated to be on the order of 1 mm, greater than expected for a diffusible molecular cue. Molecular and genetic analysis uncovered a two-step mechanism, where release of CCL2 from injured hairs leads to recruitment of TNF-α secreting macrophages, which accumulate and signal to both plucked and unplucked follicles. By coupling immune response with regeneration, this mechanism allows skin to respond predictively to distress, disregarding mild injury, while meeting stronger injury with full-scale cooperative activation of stem cells. PMID:25860610

  19. Effect of the quorum-sensing luxS gene on biofilm formation by Enterococcus faecalis.

    Science.gov (United States)

    He, Zhiyan; Liang, Jingping; Zhou, Wei; Xie, Qian; Tang, Zisheng; Ma, Rui; Huang, Zhengwei

    2016-06-01

    Enterococcus faecalis is the species of bacterium most frequently isolated from the root canals of teeth that exhibit chronic apical periodontitis refractory to endodontic treatment. In this study, we evaluated the effect of the S-ribosylhomocysteine lyase (luxS) quorum-sensing gene on E. faecalis biofilm formation by constructing a knockout mutant. The biofilms formed by both E. faecalis and its luxS mutant strain were evaluated using the MTT method. Important parameters that influence biofilm formation, including cell-surface hydrophobicity and the nutrient content of the growth medium, were also studied. Biofilm structures were observed using confocal laser scanning microscopy (CLSM), and expression of biofilm-related genes was investigated using RT-PCR. The results showed that the luxS gene can affect biofilm formation, whereas it does not affect the bacterial growth rate. Deletion of the luxS gene also increased cell-surface hydrophobicity. Biofilm formation was accelerated by the addition of increasing concentrations of glucose. The CLSM images revealed that the luxS mutant strain tends to aggregate into distinct clusters and relatively dense structures, whereas the wild-type strain appears confluent and more evenly distributed. All genes examined were up-regulated in the biofilms formed by the luxS mutant strain. The quorum-sensing luxS gene can affect E. faecalis biofilm formation. © 2016 Eur J Oral Sci.

  20. PepO, a CovRS-controlled endopeptidase, disrupts Streptococcus pyogenes quorum sensing.

    Science.gov (United States)

    Wilkening, Reid V; Chang, Jennifer C; Federle, Michael J

    2016-01-01

    Group A Streptococcus (GAS, Streptococcus pyogenes) is a human-restricted pathogen with a capacity to both colonize asymptomatically and cause illnesses ranging from pharyngitis to necrotizing fasciitis. An understanding of how and when GAS switches between genetic programs governing these different lifestyles has remained an enduring mystery and likely requires carefully tuned environmental sensors to activate and silence genetic schemes when appropriate. Herein, we describe the relationship between the Control of Virulence (CovRS, CsrRS) two-component system and the Rgg2/3 quorum-sensing pathway. We demonstrate that responses of CovRS to the stress signals Mg(2+) and a fragment of the antimicrobial peptide LL-37 result in modulated activity of pheromone signaling of the Rgg2/3 pathway through a means of proteolysis of SHP peptide pheromones. This degradation is mediated by the cytoplasmic endopeptidase PepO, which is the first identified enzymatic silencer of an RRNPP-type quorum-sensing pathway. These results suggest that under conditions in which the virulence potential of GAS is elevated (i.e. enhanced virulence gene expression), cellular responses mediated by the Rgg2/3 pathway are abrogated and allow individuals to escape from group behavior. These results also indicate that Rgg2/3 signaling is instead functional during non-virulent GAS lifestyles. © 2015 John Wiley & Sons Ltd.

  1. Acyl-Homoserine Lactone Production in Nitrifying Bacteria of the Genera Nitrosospira, Nitrobacter, and Nitrospira Identified via a Survey of Putative Quorum-Sensing Genes.

    Science.gov (United States)

    Mellbye, Brett L; Spieck, Eva; Bottomley, Peter J; Sayavedra-Soto, Luis A

    2017-11-15

    The genomes of many bacteria that participate in nitrogen cycling through the process of nitrification contain putative genes associated with acyl-homoserine lactone (AHL) quorum sensing (QS). AHL QS or bacterial cell-cell signaling is a method of bacterial communication and gene regulation and may be involved in nitrogen oxide fluxes or other important phenotypes in nitrifying bacteria. Here, we carried out a broad survey of AHL production in nitrifying bacteria in three steps. First, we analyzed the evolutionary history of AHL synthase and AHL receptor homologs in sequenced genomes and metagenomes of nitrifying bacteria to identify AHL synthase homologs in ammonia-oxidizing bacteria (AOB) of the genus Nitrosospira and nitrite-oxidizing bacteria (NOB) of the genera Nitrococcus, Nitrobacter, and Nitrospira Next, we screened cultures of both AOB and NOB with uncharacterized AHL synthase genes and AHL synthase-negative nitrifiers by a bioassay. Our results suggest that an AHL synthase gene is required for, but does not guarantee, cell density-dependent AHL production under the conditions tested. Finally, we utilized mass spectrometry to identify the AHLs produced by the AOB Nitrosospira multiformis and Nitrosospira briensis and the NOB Nitrobacter vulgaris and Nitrospira moscoviensis as N-decanoyl-l-homoserine lactone (C10-HSL), N-3-hydroxy-tetradecanoyl-l-homoserine lactone (3-OH-C14-HSL), a monounsaturated AHL (C10:1-HSL), and N-octanoyl-l-homoserine lactone (C8-HSL), respectively. Our survey expands the list of AHL-producing nitrifiers to include a representative of Nitrospira lineage II and suggests that AHL production is widespread in nitrifying bacteria.IMPORTANCE Nitrification, the aerobic oxidation of ammonia to nitrate via nitrite by nitrifying microorganisms, plays an important role in environmental nitrogen cycling from agricultural fertilization to wastewater treatment. The genomes of many nitrifying bacteria contain genes associated with bacterial cell

  2. Nonbioluminescent Strains of Photobacterium phosphoreum Produce the Cell-to-Cell Communication Signal N-(3-Hydroxyoctanoyl)homoserine Lactone

    OpenAIRE

    Flodgaard, L. R.; Dalgaard, P.; Andersen, J. B.; Nielsen, K.F.; Givskov, M.; Gram, L

    2005-01-01

    Bioluminescence is a common phenotype in marine bacteria, such as Vibrio and Photobacterium species, and can be quorum regulated by N-acylated homoserine lactones (AHLs). We extracted a molecule that induced a bacterial AHL monitor (Agrobacterium tumefaciens NT1 [pZLR4]) from packed cod fillets, which spoil due to growth of Photobacterium phosphoreum. Interestingly, AHLs were produced by 13 nonbioluminescent strains of P. phosphoreum isolated from the product. Of 177 strains of P. phosphoreum...

  3. Quorum sensing of bacteria and trans-kingdom interactions of N-acyl homoserine lactones with eukaryotes.

    Science.gov (United States)

    Hartmann, Anton; Schikora, Adam

    2012-06-01

    Many environmental and interactive important traits of bacteria, such as antibiotic, siderophore or exoenzyme (like cellulose, pectinase) production, virulence factors of pathogens, as well as symbiotic interactions, are regulated in a population density-dependent manner by using small signaling molecules. This phenomenon, called quorum sensing (QS), is widespread among bacteria. Many different bacterial species are communicating or "speaking" through diffusible small molecules. The production often is sophisticatedly regulated via an autoinducing mechanism. A good example is the production of N-acyl homoserine lactones (AHL), which occur in many variations of molecular structure in a wide variety of Gram-negative bacteria. In Gram-positive bacteria, other compounds, such as peptides, regulate cellular activity and behavior by sensing the cell density. The degradation of the signaling molecule--called quorum quenching--is probably another important integral part in the complex quorum sensing circuit. Most interestingly, bacterial quorum sensing molecules also are recognized by eukaryotes that are colonized by QS-active bacteria. In this case, the cross-kingdom interaction can lead to specific adjustment and physiological adaptations in the colonized eukaryote. The responses are manifold, such as modifications of the defense system, modulation of the immune response, or changes in the hormonal status and growth responses. Thus, the interaction with the quorum sensing signaling molecules of bacteria can profoundly change the physiology of higher organisms too. Higher organisms are obligatorily associated with microbial communities, and these truly multi-organismic consortia, which are also called holobionts, can actually be steered via multiple interlinked signaling substances that originate not only from the host but also from the associated bacteria.

  4. Quorum sensing activity in Ophiostoma ulmi: effects of fusel oils and branched chain amino acids on yeast-mycelial dimorphism.

    Science.gov (United States)

    Berrocal, A; Navarrete, J; Oviedo, C; Nickerson, K W

    2012-07-01

      For Ophiostoma (Ceratocystis) ulmi, the ability to undergo morphological change is a crucial factor for its virulence. To gain an understanding of quorum-sensing activity in O. ulmi as it relates to yeast-mycelium dimorphism control, this study examines the effects of branched-chain amino acids as well as their fusel alcohols and fusel acids as quorum sensing molecules.   In a defined medium containing glucose, proline and salts, O. ulmi grew as yeasts when the culture was inoculated with a high density of spores (2 × 10(7)  CFU ml(-1) ) and as mycelia when inoculated with a low spore density (4 × 10(5)  CFU ml(-1) ). The cultures displaying yeast morphology secreted a quorum-sensing factor that shifted the morphology from mycelia to yeast. This quorum-sensing molecule was lipophilic and extractable by organic solvents from the spent medium. Using GC/MS analysis, it was determined that the major compound in the extract was 2-methyl-1-butanol. A similar effect was observed when the branched-chain amino acids (fusel alcohol precursors) were used as the nitrogen source. E, E-farnesol had no effect on the morphology of O. ulmi.   Addition of the branched-chain amino acids or one of the compounds detected in the spent medium, 2-methyl-1-butanol or 4-hydroxyphenylacetic acid, or methylvaleric acid, decreased germ tube formation by more than 50%, thus demonstrating a quorum sensing molecule behaviour in O. ulmi cultures.   This study presents advances in the investigation of dimorphism in O. ulmi, complementing the existing scientific basis, for studying, understanding and controlling this phenomenon. © 2012 The Authors. Journal of Applied Microbiology © 2012 The Society for Applied Microbiology.

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

    Directory of Open Access Journals (Sweden)

    Adelfia Talà

    Full Text Available 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.

  6. Whole-Genome Sequence of Serratia liquefaciens HUMV-21, a Cytotoxic, Quorum-Sensing, and Biofilm-Producing Clinical Isolate.

    Science.gov (United States)

    Lázaro-Díez, María; Acosta, Felix; Remuzgo-Martínez, Sara; Ocampo-Sosa, Alain; Ocejo-Vinyals, Javier Gonzalo; Bravo, Jimena; El Aamri, Fátima; Escuela, Oliver; Martínez-Martínez, Luis; Ramos-Vivas, José

    2015-05-28

    A clinical isolate of Serratia liquefaciens (strain HUMV-21) was obtained from a skin ulcer of an adult patient. We report here its complete genome assembly using PacBio single-molecule real-time (SMRT) sequencing, which resulted in a single circular chromosome with 5.3 Mb. About 5,844 protein-coding genes are predicted from this assembly. Copyright © 2015 Lázaro-Díez et al.

  7. Deinococcus radiodurans can interfere with quorum sensing by producing an AHL-acylase and an AHL-lactonase

    NARCIS (Netherlands)

    Koch, Gudrun; Nadal-Jimenez, Pol; Cool, Robbert H.; Quax, Wim J.

    Bacterial communication via the secretion of small diffusible compounds allows microorganisms to regulate gene expression in a coordinated manner. As many virulence traits are regulated in this fashion, disruption of chemical communication has been proposed as novel antimicrobial therapy.

  8. The RpfB-Dependent Quorum Sensing Signal Turnover System Is Required for Adaptation and Virulence in Rice Bacterial Blight Pathogen Xanthomonas oryzae pv. oryzae.

    Science.gov (United States)

    Wang, Xing-Yu; Zhou, Lian; Yang, Jun; Ji, Guang-Hai; He, Ya-Wen

    2016-03-01

    Xanthomonas oryzae pv. oryzae, the bacterial blight pathogen of rice, produces diffusible signal factor (DSF) family quorum sensing signals to regulate virulence. The biosynthesis and perception of DSF family signals require components of the rpf (regulation of pathogenicity factors) cluster. In this study, we report that RpfB plays an essential role in DSF family signal turnover in X. oryzae pv. oryzae PXO99A. The production of DSF family signals was boosted by deletion of the rpfB gene and was abolished by its overexpression. The RpfC/RpfG-mediated DSF signaling system negatively regulates rpfB expression via the global transcription regulator Clp, whose activity is reversible in the presence of cyclic diguanylate monophosphate. These findings indicate that the DSF family signal turnover system in PXO99A is generally consistent with that in Xanthomonas campestris pv. campestris. Moreover, this study has revealed several specific roles of RpfB in PXO99A. First, the rpfB deletion mutant produced high levels of DSF family signals but reduced extracellular polysaccharide production, extracellular amylase activity, and attenuated pathogenicity. Second, the rpfB/rpfC double-deletion mutant was partially deficient in xanthomonadin production. Taken together, the RpfB-dependent DSF family signal turnover system is a conserved and naturally presenting signal turnover system in Xanthomonas spp., which plays unique roles in X. oryzae pv. oryzae adaptation and pathogenesis.

  9. Anti‐quorum sensing activity of AgCl‐TiO2 nanoparticles with potential use as active food packaging material

    National Research Council Canada - National Science Library

    Naik, K; Kowshik, M

    2014-01-01

    To study the anti-quorum sensing (anti-QS) activity of AgCl-TiO2 nanoparticles (ATNPs) and its mechanism. Anti-QS activity of ATNPs was evaluated using the bacterial model Chromobacterium violaceum...

  10. Inhibition of Quorum Sensing-Controlled Virulence Factor Production in Pseudomonas aeruginosa PAO1 by Ayurveda Spice Clove (Syzygium Aromaticum Bud Extract

    Directory of Open Access Journals (Sweden)

    Kok-Gan Chan

    2012-03-01

    Full Text Available 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.

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

    Science.gov (United States)

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

    2012-01-01

    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.

  12. Conformational change-induced repeat domain expansion regulates Rap phosphatase quorum-sensing signal receptors.

    Directory of Open Access Journals (Sweden)

    Vijay Parashar

    Full Text Available 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-ComA(C 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

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

    Science.gov (United States)

    Pérez, Pablo D; Weiss, Joel T; Hagen, Stephen J

    2011-09-29

    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. 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. 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

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

    Directory of Open Access Journals (Sweden)

    Weiss Joel T

    2011-09-01

    Full Text Available Abstract 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

  15. A quorum sensing-based in vivo expression system and its application in multivalent bacterial vaccine.

    Science.gov (United States)

    Chu, Teng; Ni, Chunshan; Zhang, Lingzhi; Wang, Qiyao; Xiao, Jingfan; Zhang, Yuanxing; Liu, Qin

    2015-03-18

    Delivery of antigens by live bacterial carriers can elicit effective humoral and cellular responses and may be an attractive strategy for live bacterial vaccine production through introduction of a vector that expresses an exogenous protective antigen. To overcome the instability and metabolic burden associated with plasmid introduction, alternative strategies, such as the use of in vivo-inducible promoters, have been proposed. However, screening an ideal in vivo-activated promoter with high efficiency and low leak expression in a particular strain poses great challenges to many researchers. In this work, we constructed an in vivo antigen-expressing vector suitable for Edwardsiella tarda, an enteric Gram-negative invasive intracellular pathogen of both animals and humans. By combining quorum sensing genes from Vibrio fischeri with iron uptake regulons, a synthetic binary regulation system (ironQS) for E. tarda was designed. In vitro expression assay demonstrated that the ironQS system is only initiated in the absence of Fe2+ in the medium when the cell density reaches its threshold. The ironQS system was further confirmed in vivo to present an in vivo-triggered and cell density-dependent expression pattern in larvae and adult zebrafish. A recombinant E. tarda vector vaccine candidate WED(ironQS-G) was established by introducing gapA34, which encodes the protective antigen glyceraldehyde-3-phosphate dehydrogenase (GAPDH) from the fish pathogen Aeromonas hydrophila LSA34 into ironQS system, and the immune protection afforded by this vaccine was assessed in turbot (Scophtalmus maximus). Most of the vaccinated fish survived under the challenge with A. hydrophila LSA34 (RPS=67.0%) or E. tarda EIB202 (RPS=72.3%). Quorum sensing system has been extensively used in various gene structures in synthetic biology as a well-functioning and population-dependent gene circuit. In this work, the in vivo expression system, ironQS, maintained the high expression efficiency of the

  16. Evolution of Microbial Quorum Sensing to Human Global Quorum Sensing: An Insight into How Gap Junctional Intercellular Communication Might Be Linked to the Global Metabolic Disease Crisis

    Science.gov (United States)

    Trosko, James E.

    2016-01-01

    The first anaerobic organism extracted energy for survival and reproduction from its source of nutrients, with the genetic means to ensure protection of its individual genome but also its species survival. While it had a means to communicate with its community via simple secreted molecules (“quorum sensing”), the eventual shift to an aerobic environment led to multi-cellular metazoan organisms, with evolutionary-selected genes to form extracellular matrices, stem cells, stem cell niches, and a family of gap junction or “connexin” genes. These germinal and somatic stem cells responded to extracellular signals that triggered intra-cellular signaling to regulate specific genes out of the total genome. These extra-cellular induced intra-cellular signals also modulated gap junctional intercellular communication (GJIC) in order to regulate the new cellular functions of symmetrical and asymmetrical cell division, cell differentiation, modes of cell death, and senescence. Within the hierarchical and cybernetic concepts, differentiated by neurons organized in the brain of the Homo sapiens, the conscious mind led to language, abstract ideas, technology, myth-making, scientific reasoning, and moral decision–making, i.e., the creation of culture. Over thousands of years, this has created the current collision between biological and cultural evolution, leading to the global “metabolic disease” crisis. PMID:27314399

  17. Evolution of Microbial Quorum Sensing to Human Global Quorum Sensing: An Insight into How Gap Junctional Intercellular Communication Might Be Linked to the Global Metabolic Disease Crisis.

    Science.gov (United States)

    Trosko, James E

    2016-06-15

    The first anaerobic organism extracted energy for survival and reproduction from its source of nutrients, with the genetic means to ensure protection of its individual genome but also its species survival. While it had a means to communicate with its community via simple secreted molecules ("quorum sensing"), the eventual shift to an aerobic environment led to multi-cellular metazoan organisms, with evolutionary-selected genes to form extracellular matrices, stem cells, stem cell niches, and a family of gap junction or "connexin" genes. These germinal and somatic stem cells responded to extracellular signals that triggered intra-cellular signaling to regulate specific genes out of the total genome. These extra-cellular induced intra-cellular signals also modulated gap junctional intercellular communication (GJIC) in order to regulate the new cellular functions of symmetrical and asymmetrical cell division, cell differentiation, modes of cell death, and senescence. Within the hierarchical and cybernetic concepts, differentiated by neurons organized in the brain of the Homo sapiens, the conscious mind led to language, abstract ideas, technology, myth-making, scientific reasoning, and moral decision-making, i.e., the creation of culture. Over thousands of years, this has created the current collision between biological and cultural evolution, leading to the global "metabolic disease" crisis.

  18. Synthesis and biological evaluation of novel N-α-haloacylated homoserine lactones as quorum sensing modulators

    Directory of Open Access Journals (Sweden)

    Michail Syrpas

    2014-10-01

    Full Text Available Novel N-α-haloacylated homoserine lactones, in which a halogen atom was introduced at the α-position of the carbonyl function of the N-acyl chain, have been studied as quorum sensing (QS modulators and compared with a library of natural N-acylated homoserine lactones (AHLs. The series of novel analogues consists of α-chloro, α-bromo and α-iodo AHL analogues. Furthermore, the biological QS activity of the synthetic AHL analogues compared to the natural AHLs was evaluated. Halogenated analogues demonstrated a reduced activity in the Escherichia coli JB523 bioassay, with the α-iodo lactones being the less active ones and the α-chloro AHLs the most potent QS agonists. Most of the α-haloacylated analogues did not exhibit a significant reduction when tested in the QS inhibition test. Therefore, these novel analogues could be utilized as chemical probes for QS structure–activity studies.

  19. Serotonin Activates Bacterial Quorum Sensing and Enhances the Virulence of Pseudomonas aeruginosa in the Host

    Directory of Open Access Journals (Sweden)

    Leslie D. Knecht

    2016-07-01

    Full Text Available Bacteria in humans play an important role in health and disease. Considerable emphasis has been placed in understanding the role of bacteria in host-microbiome interkingdom communication. Here we show that serotonin, responsible for mood in the brain and motility in the gut, can also act as a bacterial signaling molecule for pathogenic bacteria. Specifically, we found that serotonin acts as an interkingdom signaling molecule via quorum sensing and that it stimulates the production of bacterial virulence factors and increases biofilm formation in vitro and in vivo in a novel mouse infection model. This discovery points out at roles of serotonin both in bacteria and humans, and at phenotypic implications not only manifested in mood behavior but also in infection processes in the host. Thus, regulating serotonin concentrations in the gut may provide with paradigm shifting therapeutic approaches.

  20. Serotonin Activates Bacterial Quorum Sensing and Enhances the Virulence of Pseudomonas aeruginosa in the Host.

    Science.gov (United States)

    Knecht, Leslie D; O'Connor, Gregory; Mittal, Rahul; Liu, Xue Z; Daftarian, Pirouz; Deo, Sapna K; Daunert, Sylvia

    2016-07-01

    Bacteria in humans play an important role in health and disease. Considerable emphasis has been placed in understanding the role of bacteria in host-microbiome interkingdom communication. Here we show that serotonin, responsible for mood in the brain and motility in the gut, can also act as a bacterial signaling molecule for pathogenic bacteria. Specifically, we found that serotonin acts as an interkingdom signaling molecule via quorum sensing and that it stimulates the production of bacterial virulence factors and increases biofilm formation in vitro and in vivo in a novel mouse infection model. This discovery points out at roles of serotonin both in bacteria and humans, and at phenotypic implications not only manifested in mood behavior but also in infection processes in the host. Thus, regulating serotonin concentrations in the gut may provide with paradigm shifting therapeutic approaches. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

  1. Piper nigrum, Piper betle and Gnetum gnemon- Natural Food Sourcewith Anti-Quorum Sensing Properties

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    Li Ying Tan

    2013-03-01

    Full Text Available Various parts of Piper nigrum, Piper betle and Gnetum gnemon are used as food sources by Malaysians. The purpose of this study is to examine the anti-quorum sensing (anti-QS properties of P. nigrum, P. betle and G. gnemon extracts. The hexane, chloroform and methanol extracts of these plants were assessed in bioassays involving Pseudomonas aeruginosa PA01, Escherichia coli [pSB401], E. coli [pSB1075] and Chromobacterium violaceum CV026. It was found that the extracts of these three plants have anti-QS ability. Interestingly, the hexane, chloroform and methanol extracts from P. betle showed the most potent anti-QS activity as judged by the bioassays. Since there is a variety of plants that serve as food sources in Malaysia that have yet to be tested for anti-QS activity, future work should focus on identification of these plants and isolation of the anti-QS compounds.

  2. Piper nigrum, Piper betle and Gnetum gnemon- Natural Food Sources with Anti-Quorum Sensing Properties

    Science.gov (United States)

    Tan, Li Ying; Yin, Wai-Fong; Chan, Kok-Gan

    2013-01-01

    Various parts of Piper nigrum, Piper betle and Gnetum gnemon are used as food sources by Malaysians. The purpose of this study is to examine the anti-quorum sensing (anti-QS) properties of P. nigrum, P. betle and G. gnemon extracts. The hexane, chloroform and methanol extracts of these plants were assessed in bioassays involving Pseudomonas aeruginosa PA01, Escherichia coli [pSB401], E. coli [pSB1075] and Chromobacterium violaceum CV026. It was found that the extracts of these three plants have anti-QS ability. Interestingly, the hexane, chloroform and methanol extracts from P. betle showed the most potent anti-QS activity as judged by the bioassays. Since there is a variety of plants that serve as food sources in Malaysia that have yet to be tested for anti-QS activity, future work should focus on identification of these plants and isolation of the anti-QS compounds. PMID:23519352

  3. Tandem Mass Spectrometry Detection of Quorum Sensing Activity in Multidrug Resistant Clinical Isolate Acinetobacter baumannii

    Directory of Open Access Journals (Sweden)

    Kok-Gan Chan

    2014-01-01

    Full Text Available Many Proteobacteria communicate via production followed by response of quorum sensing molecules, namely, N-acyl homoserine lactones (AHLs. These molecules consist of a lactone moiety with N-acyl side chain with various chain lengths and degrees of saturation at C-3 position. AHL-dependent QS is often associated with regulation of diverse bacterial phenotypes including the expression of virulence factors. With the use of biosensor and high resolution liquid chromatography tandem mass spectrometry, the AHL production of clinical isolate A. baumannii 4KT was studied. Production of short chain AHL, namely, N-hexanoyl-homoserine lactone (C6-HSL and N-octanoyl-homoserine lactone (C8-HSL, was detected.

  4. Quorum sensing - A novel target for the treatment of biofilm infections

    DEFF Research Database (Denmark)

    Hentzer, Morten; Eberl, L.; Nielsen, J.

    2003-01-01

    that all therapeutics are considerably less effective on bacteria growing as biofilms when compared with planktonic cells. The latter point is of particular importance as evidence has accumulated over the past few years that most chronic bacterial infections involve biofilms. The discovery of bacterial......Present-day treatment of chronic infections is based on compounds that aim to kill or inhibit growth of bacteria. Two problems are recognised to be intrinsically associated with this approach: (i) the frequently observed development of resistance to antimicrobial compounds; and (ii) the fact...... communication systems (quorum sensing systems) in Gram-negative bacteria which are believed to orchestrate important temporal events during the infectious process, including the production of virulence factors and the formation of biofilms, has afforded a novel opportunity to control the activity of infecting...

  5. Quorum Sensing Regulation of Adhesion in Serratia Marcescens MG1 is surface dependent

    DEFF Research Database (Denmark)

    Labbate, M.; Zhu, H.; Thung, L.

    2007-01-01

    not able to identify a single QS-regulated adhesin essential for attachment to the abiotic surface, four AHL-regulated genes involved in adhesion to the abiotic surface were identified. Interestingly, two of these genes, bsmA and bsmB, were also shown to be involved in adhesion to the biotic surface...... in a non-QS-controlled fashion. Therefore, the expression of these two genes appears to be cocontrolled by regulators other than the QS system for mediation of attachment to HCE cells. We also found that QS in S. marcescens regulates other potential cell surface adhesins, including exopolysaccharide......Serratia marcescens is an opportunistic pathogen and a major cause of ocular infections. In previous studies of S. marcescens MG1, we showed that biofilm maturation and sloughing were regulated by N-acyl homoserine lactone (AHL)-based quorum sensing (QS). Because of the importance of adhesion...

  6. An Effective Application of Bacteria Quorum Sensing and Circular Elimination in MOPSO.

    Science.gov (United States)

    Cheng, Shan; Zhao, Long-Long; Jiang, Xiao-Yu

    2017-01-01

    In this paper, an approach that incorporates a turbulence mechanism and a circular elimination strategy is presented to strengthen the performance of multi-objective particle swarm optimization (MOPSO). For convergence enhancement, the turbulence mechanism derived from bacteria quorum sensing behavior is introduced to MOPSO to preserve the swarm diversity. Meanwhile, the circular elimination strategy is used to select particles for next iteration for better distribution of the Pareto-optimal solutions. The improved MOPSO algorithm has been tested on a set of benchmark functions and compared with representative multi-objective optimization algorithms. Simulation results illustrate that the algorithm outperforms the other algorithms on convergence while keep good spread performance, and could be used as an effective global optimization tool.

  7. Antibiotic-mediated selection of quorum-sensing-negative Staphylococcus aureus

    DEFF Research Database (Denmark)

    Paulander, Wilhelm Erik Axel; Varming, Anders Nissen; Bæk, Kristoffer Torbjørn

    2012-01-01

    -acquired S. aureus infections and suggest that the adaptability of S. aureus to antibiotics involves the agr locus. IMPORTANCE: Staphylococcus aureus is the most frequently isolated pathogen in intensive care units and a common cause of nosocomial infections, resulting in a high degree of morbidity......Staphylococcus aureus is a human commensal that at times turns into a serious bacterial pathogen causing life-threatening infections. For the delicate control of virulence, S. aureus employs the agr quorum-sensing system that, via the intracellular effector molecule RNAIII, regulates virulence gene...... increases the agr-mediated fitness cost by inducing the expression of RNAIII. Thus, the extensive use of antibiotics in hospitals may explain why agr-negative variants are frequently isolated from hospital-acquired S. aureus infections but rarely found among community-acquired S. aureus strains. Importantly...

  8. Kinetic Model for Signal Binding to the Quorum Sensing Regulator LasR

    DEFF Research Database (Denmark)

    Claussen, Anetta; Jakobsen, Tim Holm; Bjarnsholt, Thomas

    2013-01-01

    We propose a kinetic model for the activation of the las regulon in the opportunistic pathogen Pseudomonas aeruginosa. The model is based on in vitro data and accounts for the LasR dimerization and consecutive activation by binding of two OdDHL signal molecules. Experimentally, the production...... of the active LasR quorum-sensing regulator was studied in an Escherichia coli background as a function of signal molecule concentration. The functional activity of the regulator was monitored via a GFP reporter fusion to lasB expressed from the native lasB promoter. The new data shows that the active form...... of the LasR dimer binds two signal molecules cooperatively and that the timescale for reaching saturation is independent of the signal molecule concentration. This favors a picture where the dimerized regulator is protected against proteases and remains protected as it is activated through binding of two...

  9. Quorum-sensing inhibition abrogates the deleterious impact of Pseudomonas aeruginosa on airway epithelial repair.

    Science.gov (United States)

    Ruffin, Manon; Bilodeau, Claudia; Maillé, Émilie; LaFayette, Shantelle L; McKay, Geoffrey A; Trinh, Nguyen Thu Ngan; Beaudoin, Trevor; Desrosiers, Martin-Yvon; Rousseau, Simon; Nguyen, Dao; Brochiero, Emmanuelle

    2016-09-01

    Chronic Pseudomonas aeruginosa lung infections are associated with progressive epithelial damage and lung function decline. In addition to its role in tissue injury, the persistent presence of P. aeruginosa-secreted products may also affect epithelial repair ability, raising the need for new antivirulence therapies. The purpose of our study was to better understand the outcomes of P. aeruginosa exoproducts exposure on airway epithelial repair processes to identify a strategy to counteract their deleterious effect. We found that P. aeruginosa exoproducts significantly decreased wound healing, migration, and proliferation rates, and impaired the ability of directional migration of primary non-cystic fibrosis (CF) human airway epithelial cells. Impact of exoproducts was inhibited after mutations in P. aeruginosa genes that encoded for the quorum-sensing (QS) transcriptional regulator, LasR, and the elastase, LasB, whereas impact was restored by LasB induction in ΔlasR mutants. P. aeruginosa purified elastase also induced a significant decrease in non-CF epithelial repair, whereas protease inhibition with phosphoramidon prevented the effect of P. aeruginosa exoproducts. Furthermore, treatment of P. aeruginosa cultures with 4-hydroxy-2,5-dimethyl-3(2H)-furanone, a QS inhibitor, abrogated the negative impact of P. aeruginosa exoproducts on airway epithelial repair. Finally, we confirmed our findings in human airway epithelial cells from patients with CF, a disease featuring P. aeruginosa chronic respiratory infection. These data demonstrate that secreted proteases under the control of the LasR QS system impair airway epithelial repair and that QS inhibitors could be of benefit to counteract the deleterious effect of P. aeruginosa in infected patients.-Ruffin, M., Bilodeau, C., Maillé, É., LaFayette, S. L., McKay, G. A., Trinh, N. T. N., Beaudoin, T., Desrosiers, M.-Y., Rousseau, S., Nguyen, D., Brochiero, E. Quorum-sensing inhibition abrogates the deleterious impact

  10. Baicalein Inhibits Staphylococcus aureus Biofilm Formation and the Quorum Sensing System In Vitro.

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    Yan Chen

    Full Text Available Biofilm formed by Staphylococcus aureus significantly enhances antibiotic resistance by inhibiting the penetration of antibiotics, resulting in an increasingly serious situation. This study aimed to assess whether baicalein can prevent Staphylococcus aureus biofilm formation and whether it may have synergistic bactericidal effects with antibiotics in vitro. To do this, we used a clinically isolated strain of Staphylococcus aureus 17546 (t037 for biofilm formation. Virulence factors were detected following treatment with baicalein, and the molecular mechanism of its antibiofilm activity was studied. Plate counting, crystal violet staining, and fluorescence microscopy revealed that 32 μg/mL and 64 μg/mL baicalein clearly inhibited 3- and 7-day biofilm formation in vitro. Moreover, colony forming unit count, confocal laser scanning microscopy, and scanning electron microscopy showed that vancomycin (VCM and baicalein generally enhanced destruction of biofilms, while VCM alone did not. Western blotting and real-time quantitative polymerase chain reaction analyses (RTQ-PCR confirmed that baicalein treatment reduced staphylococcal enterotoxin A (SEA and α-hemolysin (hla levels. Most strikingly, real-time qualitative polymerase chain reaction data demonstrated that 32 μg/mL and 64 μg/mL baicalein downregulated the quorum-sensing system regulators agrA, RNAIII, and sarA, and gene expression of ica, but 16 μg/mL baicalein had no effect. In summary, baicalein inhibited Staphylococcus aureus biofilm formation, destroyed biofilms, increased the permeability of vancomycin, reduced the production of staphylococcal enterotoxin A and α-hemolysin, and inhibited the quorum sensing system. These results support baicalein as a novel drug candidate and an effective treatment strategy for Staphylococcus aureus biofilm-associated infections.

  11. Autoinducer-2 Quorum Sensing Contributes to Regulation of Microcin PDI in Escherichia coli

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    Shao-Yeh Lu

    2017-12-01

    Full Text Available The Escherichia coli quorum sensing (QS signal molecule, autoinducer-2 (AI-2, reaches its maximum concentration during mid-to-late growth phase after which it quickly degrades during stationary phase. This pattern of AI-2 concentration coincides with the up- then down-regulation of a recently described microcin PDI (mccPDI effector protein (McpM. To determine if there is a functional relationship between these systems, a prototypical mccPDI-expressing strain of E. coli 25 was used to generate ΔluxS, ΔlsrACDBFG (Δlsr, and ΔlsrR mutant strains that are deficient in AI-2 production, transportation, and AI-2 transport regulation, respectively. Trans-complementation, RT-qPCR, and western blot assays were used to detect changes of microcin expression and synthesis under co-culture and monoculture conditions. Compared to the wild-type strain, the AI-2-deficient strain (ΔluxS and -uptake negative strain (Δlsr were >1,000-fold less inhibitory to susceptible bacteria (P < 0.05. With in trans complementation of luxS, the AI-2 deficient mutant reduced the susceptible E. coli population by 4-log, which was within 1-log of the wild-type phenotype. RT-qPCR and western blot results for the AI-2 deficient E. coli 25 showed a 5-fold reduction in mcpM transcription with an average 2-h delay in McpM synthesis. Furthermore, overexpression of sRNA micC and micF (both involved in porin protein regulation was correlated with mcpM regulation, consistent with a possible link between QS and mcpM regulation. This is the direct first evidence that microcin regulation can be linked to quorum sensing in a Gram-negative bacterium.

  12. Phase transition approach to bursting in neuronal cultures: quorum percolation models

    Science.gov (United States)

    Monceau, P.; Renault, R.; Métens, S.; Bottani, S.; Fardet, T.

    2017-10-01

    The Quorum Percolation model has been designed in the context of neurobiology to describe bursts of activity occurring in neuronal cultures from the point of view of statistical physics rather than from a dynamical synchronization approach. It is based upon information propagation on a directed graph with a threshold activation rule; this leads to a phase diagram which exhibits a giant percolation cluster below some critical value mC of the excitability. We describe the main characteristics of the original model and derive extensions according to additional relevant biological features. Firstly, we investigate the effects of an excitability variability on the phase diagram and show that the percolation transition can be destroyed by a sufficient amount of such a disorder; we stress the weakly averaging character of the order parameter and show that connectivity and excitability can be seen as two overlapping aspects of the same reality. Secondly, we elaborate a discrete time stochastic model taking into account the decay originating from ionic leakage through the membrane of neurons and synaptic depression; we give evidence that the decay softens and shifts the transition, and conjecture than decay destroys the transition in the thermodynamical limit. We were able to develop mean-field theories associated with each of the two effects; we discuss the framework of their agreement with Monte Carlo simulations. It turns out that the the critical point mC from which information on the connectivity of the network can be inferred is affected by each of these additional effects. Lastly, we show how dynamical simulations of bursts with an adaptive exponential integrateand- fire model can be interpreted in terms of Quorum Percolation. Moreover, the usefulness of the percolation model including the set of sophistication we investigated can be extended to many scientific fields involving information propagation, such as the spread of rumors in sociology, ethology, ecology.

  13. Acinetobacter baumannii quorum-sensing signalling molecule induces the expression of drug-resistance genes

    Science.gov (United States)

    Dou, Yi; Song, Fei; Guo, Feng; Zhou, Zengding; Zhu, Cailian; Xiang, Jun; Huan, Jingning

    2017-01-01

    Quorum-sensing signalling molecules such as N-acyl homoserine lactones (AHLs) enable certain Gram-negative bacteria to respond to environmental changes through behaviours, such as biofilm formation and flagellar movement. The present study aimed to identify Acinetobacter baumannii AHLs and assess their influence on antibiotic resistance. A clinical isolate of A. baumannii strain S (AbS) was collected from the wound of a burn patient and high-performance liquid chromatography and tandem quadrupole or quadrupole time-of-flight high-resolution mass spectrometry was used to identify AbS AHLs. Antibiotic sensitivity was assessed in an AHL-deficient AbS mutant (AbS-M), and the expression of drug-resistance genes in the presence of meropenem in AbS, AbS-M and AbS-M treated with the AHL N-3-hydroxy-dodecanoyl-homoserine lactone (N-3-OH-C12-HSL). AbS-M was more sensitive to meropenem and piperacillin than wild-type AbS, but resistance was restored by supplementation with N-3-OH-C12-HSL. In addition, meropenem-treated AbS-M expressed lower levels of the drug-resistance genes oxacillinase 51, AmpC, AdeA and AdeB; treatment with N-3-OH-C12-HSL also restored the expression of these genes. Overall, the results of the present study indicate that N-3-OH-C12-HSL may be involved in regulating the expression of drug-resistance genes in A. baumannii. Therefore, this quorum-sensing signalling molecule may be an important target for treating multidrug-resistant A. baumannii infections. PMID:28487993

  14. Adaptive Significance of Quorum Sensing-dependent Regulation of Rhamnolipids by Integration of Growth Rate in Burkholderia glumae: A Trade-off between Survival and Efficiency

    Directory of Open Access Journals (Sweden)

    Arvin Nickzad

    2016-08-01

    Full Text Available Quorum sensing (QS is a cell density-dependent mechanism which enables a population of bacteria to coordinate cooperative behaviors in response to the accumulation of self-produced autoinducer signals in their local environment. An emerging framework is that the adaptive significance of QS in the regulation of production of costly extracellular metabolites («public goods» is to maintain the homeostasis of cooperation. We investigated this model using the phytopathogenic bacterium Burkholderia glumae, which we have previously demonstrated uses QS to regulate the production of rhamnolipids, extracellular surface-active glycolipids promoting the social behavior called «swarming motility». Using mass spectrometric quantification and chromosomal lux-based gene expression, we made the unexpected finding that when unrestricted nutrient resources are provided, production of rhamnolipids is carried out completely independently of QS regulation. This is a unique observation among known QS-controlled factors in bacteria. On the other hand, under nutrient-limited conditions, QS then becomes the main regulating mechanism, significantly enhancing the specific rhamnolipids yield. Accordingly, decreasing nutrient concentrations amplifies rhamnolipid biosynthesis gene expression, revealing a system where QS-dependent regulation is specifically triggered by the growth rate of the population, rather than by its cell density. Furthermore, a gradual increase in QS signal specific concentration upon decrease of specific growth rate suggests a reduction in quorum threshold, which reflects an increase in cellular demand for production of QS-dependent target gene product at low density populations. Integration of growth rate with QS as a decision-making mechanism for biosynthesis of costly metabolites, such as rhamnolipids, could serve to assess the demand and timing for expanding the carrying capacity of a population through spatial expansion mechanisms, such as

  15. Quorum quenching activity in cell-free lysate of endophytic bacteria isolated from Pterocarpus santalinus Linn., and its effect on quorum sensing regulated biofilm in Pseudomonas aeruginosa PAO1.

    Science.gov (United States)

    Rajesh, P S; Ravishankar Rai, V

    2014-01-01

    Quorum sensing mechanism allows the microorganisms to resist the antibiotic treatment by forming biofilms. Quorum quenching is one of the mechanisms to control the development of drug resistance in microbes. Endophyte bacteria are beneficial to plant growth as they support the immune system against the pathogen attack. The endophytic bacteria present in Pterocarpus santalinus were screened for the presence of N-acyl homoserine lactones (AHLs) degrading bacteria using biosensor strains and further confirmed by quantifying the violacein production. Cell-free lysate of endophytic bacteria, Bacillus firmus PT18 and Enterobacter asburiae PT39 exhibited potent AHL degrading ability by inhibiting about 80% violacein production in biosensor strain. Furthermore, when the cell-free lysate was applied to Pseudomonas aeruginosa PAO1 and PAO1-JP2 biofilm it resulted in significant (p<0.01) inhibition of biofilm formation. The biofilm inhibition was confirmed by visualization of biofilm slides under fluorescence microscopy, which showed decrease in total biomass formation in treated slides. Isolation and amplification of the gene (aiiA) indicated that the presence of AHL lactonase in cell-free lysate and sequence alignment indicated that AiiA contains a "HXHXDH" zinc-binding motif that is being conserved in several groups of metallohydrolases. Therefore, the study shows the potential of AHLs degradation by AHL lactonase present in cell-free lysate of isolated endophytic bacteria and inhibition of quorum sensing regulated biofilm formation in P. aeruginosa PAO1. Copyright © 2013 Elsevier GmbH. All rights reserved.

  16. Raw cow’s milk relatively inhibits quorum sensing activity of Cromobacterium violaceum in comparison to raw she-camel’s milk

    Directory of Open Access Journals (Sweden)

    A.A. Moawad

    2011-10-01

    Full Text Available Milk from different animal species has variable levels of antimicrobial factors against some of spoilage bacteria. For example, they are significantly present in higher concentration in she-camel’s milk than in cattle or buffalo and they are more heat-resistant than their counterparts in cattle and buffalo. Spoilage bacteria are known to communicate with each other by release of signaling molecules, a phenomenon described as quorum sensing (QS. Some food matrices inhibit these signaling compounds. In this study we screened QS inhibitory activities in raw milk of cattle and camel. Ten samples each of fresh raw cow’s milk and she-camel’s milk from apparently healthy animals were screened using the bacterial model Cromobacterium violaceum. The tested cow’s raw milk samples were able to inhibit the production of QS signalling molecules acyl-homoserine lactones (AHLs produced by C. violaceum. However, she-camel’s milk samples were less effective in inhibiting such AHLs. Thus, one of the factors which influence the inhibitory activity could be derived from variation in milk chemical composition, especially in the percentage of fat which is significantly higher in tested cow’s milk samples (2.22±0.12 than in tested she-camel’s milk samples (1.44±0.35. Natural inhibition of QS signaling by cow’s milk may offer a unique means to control foodborne pathogens and reduce microbial spoilage.

  17. The pattern of growth observed for Clostridium botulinum type A1 strain ATCC 19397 is influenced by nutritional status and quorum sensing: a modelling perspective.

    Science.gov (United States)

    Ihekwaba, Adaoha E C; Mura, Ivan; Peck, Michael W; Barker, G C

    2015-12-01

    Botulinum neurotoxins (BoNTs) produced by the anaerobic bacterium Clostridium botulinum are the most poisonous substances known to mankind. However, toxin regulation and signals triggering synthesis as well as the regulatory network and actors controlling toxin production are unknown. Experiments show that the neurotoxin gene is growth phase dependent for C. botulinum type A1 strain ATCC 19397, and toxin production is influenced both by culture conditions and nutritional status of the medium. Building mathematical models to describe the genetic and molecular machinery that drives the synthesis and release of BoNT requires a simultaneous description of the growth of the bacterium in culture. Here, we show four plausible modelling options which could be considered when constructing models describing the pattern of growth observed in a botulinum growth medium. Commonly used bacterial growth models are unsuitable to fit the pattern of growth observed, since they only include monotonic growth behaviour. We find that a model that includes both the nutritional status and the ability of the cells to sense their surroundings in a quorum-sensing manner is most successful at explaining the pattern of growth obtained for C. botulinum type A1 strain ATCC 19397. © FEMS 2015.

  18. A Method for Structure–Activity Analysis of Quorum-Sensing Signaling Peptides from Naturally Transformable Streptococci

    Directory of Open Access Journals (Sweden)

    Tian XiaoLin

    2009-06-01

    Full Text Available Abstract Many species of streptococci secrete and use a competence-stimulating peptide (CSP to initiate quorum sensing for induction of genetic competence, bacteriocin production, and other activities. These signaling molecules are small, unmodified peptides that induce powerful strain-specific activity at nano-molar concentrations. This feature has provided an excellent opportunity to explore their structure–function relationships. However, CSP variants have also been identified in many species, and each specifically activates its cognate receptor. How such minor changes dramatically affect the specificity of these peptides remains unclear. Structure–activity analysis of these peptides may provide clues for understanding the specificity of signaling peptide–receptor interactions. Here, we use the Streptococcus mutans CSP as an example to describe methods of analyzing its structure–activity relationship. The methods described here may provide a platform for studying quorum-sensing signaling peptides of other naturally transformable streptococci.

  19. A Method for Structure–Activity Analysis of Quorum-Sensing Signaling Peptides from Naturally Transformable Streptococci

    Directory of Open Access Journals (Sweden)

    Syvitski Raymond

    2009-01-01

    Full Text Available Abstract Many species of streptococci secrete and use a competence-stimulating peptide (CSP to initiate quorum sensing for induction of genetic competence, bacteriocin production, and other activities. These signaling molecules are small, unmodified peptides that induce powerful strain-specific activity at nano-molar concentrations. This feature has provided an excellent opportunity to explore their structure–function relationships. However, CSP variants have also been identified in many species, and each specifically activates its cognate receptor. How such minor changes dramatically affect the specificity of these peptides remains unclear. Structure–activity analysis of these peptides may provide clues for understanding the specificity of signaling peptide–receptor interactions. Here, we use the Streptococcus mutans CSP as an example to describe methods of analyzing its structure–activity relationship. The methods described here may provide a platform for studying quorum-sensing signaling peptides of other naturally transformable streptococci.

  20. The quorum sensing luxS gene is induced in Lactobacillus acidophilus NCFM in response to Listeria monocytogenes

    DEFF Research Database (Denmark)

    Moslehi Jenabian, Saloomeh; Vogensen, Finn Kvist; Jespersen, Lene

    2011-01-01

    The luxS gene involved in quorum sensing has been shown to control different behaviour of probiotic lactobacilli. In this study we investigated if luxS in Lactobacillus acidophilus NCFM was up-regulated in response to Listeria monocytogenes EGD-e. The two bacterial strains were grown in mono......-killed cells of L. monocytogenes have no effect on luxS transcription. The luxS gene involved in quorum sensing has been shown to control different behaviour of probiotic lactobacilli. In this study we investigated if luxS in Lactobacillus acidophilus NCFM was up-regulated in response to Listeria monocytogenes......- and co-culture and the growth of both bacteria and the transcriptional level of luxS in L. acidophilus cells were monitored. Contrary to L. acidophilus, the growth of L. monocytogenes was significantly affected by co-cultivation. Transcriptional analysis showed that the expression of luxS increased...

  1. Inhibiting effects of fructanase on competence-stimulating peptide-dependent quorum sensing system in Streptococcus mutans.

    Science.gov (United States)

    Suzuki, Yusuke; Nagasawa, Ryo; Senpuku, Hidenobu

    2017-09-01

    Streptococcus mutans produces glucosyltransferases encoded by the gtfB and gtfC genes, which synthesize insoluble glucan, and both insoluble and soluble glucans by conversion of sucrose, and are known as principal agents to provide strong biofilm formation and demineralization on tooth surfaces. S. mutans possess a Com-dependent quorum sensing (QS) system, which is important for survival in severe conditions. The QS system is stimulated by the interaction between ComD {Receptor to competence-stimulating peptide (CSP)} encoded by the comD and CSP encoded by the comC, and importantly associated with bacteriocin production and genetic competence. Previously, we found enzyme fructanase (FruA) as a new inhibitor for the glucan-dependent biofilm formation. In the present study, inhibiting effects by FruA on glucan-independent biofilm formation of S. mutans UA159, UA159.gtfB(-), UA159.gtfC(-), and UA159.gtfBC(-) were observed in sucrose and no sucrose sugars-supplemented conditions using the plate assay. The reduction of UA159.comC(-) and UA159.comD(-) biofilm formation were also observed as compared with UA159 in same conditions. These results suggested that inhibitions of glucan-independent and Com-dependent biofilm formation were involved in the inhibiting mechanism by FruA. To more thoroughly investigate effects by FruA on the QS system, we examined on CSP-stimulated and Com-dependent bacteriocin production and genetic transformation. FruA inhibited bacteriocin production in collaboration with CSP and genetic transformation in bacterial cell conditions treated with FruA. Our findings show that FruA has multiple effects that inhibit survival functions of S. mutans, including biofilm formation and CSP-dependent QS responses, indicating its potential use as an agent for prevention of dental caries. Copyright © 2017 Japanese Society of Chemotherapy and The Japanese Association for Infectious Diseases. Published by Elsevier Ltd. All rights reserved.

  2. quorum sensing

    African Journals Online (AJOL)

    kannappan

    2012-10-02

    Oct 2, 2012 ... Luminescence process was attributed to the transcriptional regulation of the enzyme called luciferase, which in turn match up to a threshold density of cells. This whole circuit is based on the estimation of bacterial density by means of releasing auto-inducers. They establish a communication between the ...

  3. Periodontitis, Porphyromonas gingivalis y su relación con la expresión de quorum sensing Periodontitis, Porphyromonas gingivalis and its relation to quorum sensing expression

    Directory of Open Access Journals (Sweden)

    Antonio Díaz Caballero

    2010-12-01

    Full Text Available Los mecanismos de señalización bacteriana desempeñan un papel fundamental en el establecimiento y progresión de la enfermedad periodontal. Dadas estas circunstancias es crucial profundizar en el entendimiento de estos mecanismos para intentar proveer estrategias terapéuticas novedosas. El presente artículo de revisión, de carácter narrativo, tiene como objetivo conducir un análisis crítico de la evidencia disponible sobre la influencia de Porphyromonas gingivalis (Pg y expresión de quorum sensing (Qs en enfermedad periodontal. Se realizó una búsqueda a través de bases de datos como Ovid (MEDLINE, ScienceDirect, Hinari. El conocimiento actual de estos mecanismos ofrece la posibilidad de desarrollar nuevos y profundos estudios (teóricos y experimentales sobre la expresión del QS en pacientes con enfermedad periodontal y permitirá un novedoso campo de investigación con el que no se cuenta en la actualidad. Desde su descubrimiento, el QS se vislumbra como un espacio de investigación valioso en el cual se debe insistir de manera permanente. La anterior evidencia permite concluir que a través de la regulación de la expresión de determinados genes en bacterias como la PG, se puede efectuar la inhibición de la formación de las biopelículas que tiene efectos directos e indirectos sobre el desarrollo de la enfermedad periodontal.The bacterial signaling mechanisms play a key role in the establishment and progression of periodontal disease. Due to these circumstances it is crucial to deepen in the understanding of these mechanisms to try to provide novel therapeutic strategies. The objective of present narrative literature review was to make a critical analyze of the available evidence on the influence of Porphyromonas gingivalis (PG and the quorum sensing expression in periodontal disease. Using the Ovid (MEDLINE ScienceDirect, Hinari database we made a search. The current knowledge of these mechanisms offers the possibility of

  4. Structure of PlcR: Insights into virulence regulation and evolution of quorum sensing in Gram-positive bacteria

    OpenAIRE

    Declerck, Nathalie; Bouillaut, Laurent; Chaix, Denis; Rugani, Nathalie; Slamti, Leyla; Hoh, François; Lereclus, Didier; Arold, Stefan T.

    2007-01-01

    Gram-positive bacteria use a wealth of extracellular signaling peptides, so-called autoinducers, to regulate gene expression according to population densities. These “quorum sensing” systems control vital processes such as virulence, sporulation, and gene transfer. Using x-ray analysis, we determined the structure of PlcR, the major virulence regulator of the Bacillus cereus group, and obtained mechanistic insights into the effects of autoinducer binding. Our structural and phylogenetic analy...

  5. The natural antimicrobial carvacrol inhibits quorum sensing in Chromobacterium violaceum and reduces bacterial biofilm formation at sub-lethal concentrations.

    Directory of Open Access Journals (Sweden)

    Sara A Burt

    Full Text Available 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.

  6. Escherichia coli Quorum-Sensing EDF, A Peptide Generated by Novel Multiple Distinct Mechanisms and Regulated by trans-Translation

    OpenAIRE

    Kumar, Sathish; Kolodkin-Gal, Ilana; Vesper, Oliver; Alam, Nawsad; Schueler-Furman, Ora; Moll, Isabella; Engelberg-Kulka, Hanna

    2016-01-01

    ABSTRACT Eshcerichia coli mazEF is a stress-induced toxin-antitoxin module mediating cell death and requiring a quorum-sensing (QS) extracellular death factor (EDF), the pentapeptide NNWNN. Here we uncovered several distinct molecular mechanisms involved in its generation from the zwf mRNA encoding glucose-6-phosphate dehydrogenase. In particular, we show that, under stress conditions, the endoribonuclease MazF cleaves specific ACA sites, thereby generating a leaderless zwf mRNA which is trun...

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

    OpenAIRE

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

    2013-01-01

    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...

  8. Beneficial effects of bacteria-plant communication based on quorum sensing molecules of the N-acyl homoserine lactone group.

    Science.gov (United States)

    Schikora, Adam; Schenk, Sebastian T; Hartmann, Anton

    2016-04-01

    Bacterial quorum sensing (QS) mechanisms play a crucial role in the proper performance and ecological fitness of bacterial populations. Many key physiological processes are regulated in a QS-dependent manner by auto-inducers, like the N-acyl homoserine lactones (AHLs) in numerous Gram-negative bacteria. In addition, also the interaction between bacteria and eukaryotic hosts can be regulated by AHLs. Those mechanisms gained much attention, because of the positive effects of different AHL molecules on plants. This positive impact ranges from growth promotion to induced resistance and is quite contrasting to the rather negative effects observed in the interactions between bacterial AHL molecules and animals. Only very recently, we began to understand the molecular mechanisms underpinning plant responses to AHL molecules. In this review, we gathered the latest information in this research field. The first part gives an overview of the bacterial aspects of quorum sensing. Later we focus on the impact of AHLs on plant growth and AHL-priming, as one of the most understood phenomena in respect to the inter-kingdom interactions based on AHL-quorum sensing molecules. Finally, we discuss the potential benefits of the understanding of bacteria-plant interaction for the future agricultural applications.

  9. Regular Wounding in a Natural System: Bacteria Associated With Reproductive Organs of Bedbugs and Their Quorum Sensing Abilities

    Directory of Open Access Journals (Sweden)

    Oliver Otti

    2017-12-01

    Full Text Available During wounding, tissues are disrupted so that bacteria can easily enter the host and trigger a host response. Both the host response and bacterial communication can occur through quorum sensing (QS and quorum sensing inhibition (QSI. Here, we characterize the effect of wounding on the host-associated bacterial community of the bed bug. This is a model system where the male is wounding the female during every mating. Whereas several aspects of the microbial involvement during wounding have been previously examined, it is not clear to what extent QS and QSI play a role. We find that the microbiome differs depending on mating and feeding status of female bedbugs and is specific to the location of isolation. Most organs of bedbugs harbor bacteria, which are capable of both QS and QSI signaling. By focusing on the prokaryotic quorum communication system, we provide a baseline for future research in this unique system. We advocate the bedbug system as suitable for studying the effects of bacteria on reproduction and for addressing prokaryote and eukaryote communication during wounding.

  10. Anti-quorum sensing and antimicrobial activities of some traditional Chinese medicinal plants commonly used in South-East Asia

    Directory of Open Access Journals (Sweden)

    Yeo, S.S.M

    2012-01-01

    Full Text Available Aims: Traditional Chinese medicine (TCM has been used for relief and treatment of ailments dating back thousands of years and continues to the present day, with rapidly increasing interest in evidence-based evaluation of its efficacy. Studies of TCM plants have demonstrated that several have antimicrobial properties but few have explored their anti-quorum sensing potential. Quorum sensing (QS, also known as bacterial cell-to-cell communication, is used by a number of opportunistic pathogenic bacteria in the regulation of virulence expression. Compounds that interfere with QS signals and attenuate bacterial virulence without killing them may offer an alternative therapeutic solution with less pressure of antibiotic resistance developing. This study screened TCM plants for anti-quorum sensing properties and antimicrobial activities.Methodology and Results: Twenty TCM plants commonly used in South-East Asia were screened for QS inhibitors using two biomonitor strains, Chromobacterium violaceum CV026 and Pseudomonas aeruginosa PAO1. Ten of these selected TCM plant (50% were found to have QS inhibitory properties: Angelica sinensis (Umbelliferae, Cnidium monnieri (Umbelliferae, Astragalus membranaceus (Leguminosae, Crataegus cuneata (Rosaceae, Dioscorea nipponica (Dioscoreaceae, Lilium brownii (Liliaceae, Aloe barbadensis (Liliaceae, Magnolia officinalis (Magnoliaceae, Ephedra sinica (Ephedraceae and Panax pseudoginseng (Araliaceae. Of these, six (30% also showed varying antimicrobial activity against C. violaceum and P. aeruginosa.Conclusion, significance and impact of study: The results suggest that traditional Chinese medicinal plants could be a prospective source to explore for useful compounds in the fight against bacterial infections.

  11. More Efficient Media Design for Enhanced Biofouling Control in a Membrane Bioreactor: Quorum Quenching Bacteria Entrapping Hollow Cylinder.

    Science.gov (United States)

    Lee, Sang H; Lee, Seonki; Lee, Kibaek; Nahm, Chang H; Kwon, Hyeokpil; Oh, Hyun-Suk; Won, Young-June; Choo, Kwang-Ho; Lee, Chung-Hak; Park, Pyung-Kyu

    2016-08-16

    Recently, membrane bioreactors (MBRs) with quorum quenching (QQ) bacteria entrapping beads have been reported as a new paradigm in biofouling control because, unlike conventional post-biofilm control methods, bacterial QQ can inhibit biofilm formation through its combined effects of physical scouring of the membrane and inhibition of quorum sensing (QS). In this study, using a special reporter strain (Escherichia coli JB525), the interaction between QS signal molecules and quorum quenching bacteria entrapping beads (QQ-beads) was elucidated through visualization of the QS signal molecules within a QQ-bead using a fluorescence microscope. As a result, under the conditions considered in this study, the surface area of QQ-media was likely to be a dominant parameter in enhancing QQ activity over total mass of entrapped QQ bacteria because QQ bacteria located near the core of a QQ-bead were unable to display their QQ activities. On the basis of this information, a more efficient QQ-medium, a QQ hollow cylinder (QQ-HC), was designed and prepared. In batch experiments, QQ-HCs showed greater QQ activity than QQ-beads as a result of their higher surface area and enhanced physical washing effect because of their larger impact area against the membrane surface. Furthermore, it was shown that such advantages of QQ-HCs resulted in more effective mitigation of membrane fouling than from QQ-beads in lab-scale continuous MBRs.

  12. Indirect pathogenicity of Haemophilus influenzae and Moraxella catarrhalis in polymicrobial otitis media occurs via interspecies quorum signaling.

    Science.gov (United States)

    Armbruster, Chelsie E; Hong, Wenzhou; Pang, Bing; Weimer, Kristin E D; Juneau, Richard A; Turner, James; Swords, W Edward

    2010-07-06

    Otitis media (OM) is among the leading diseases of childhood and is caused by opportunists that reside within the nasopharynx, such as Haemophilus influenzae and Moraxella catarrhalis. As with most airway infections, it is now clear that OM infections involve multiple organisms. This study addresses the hypothesis that polymicrobial infection alters the course, severity, and/or treatability of OM disease. The results clearly show that coinfection with H. influenzae and M. catarrhalis promotes the increased resistance of biofilms to antibiotics and host clearance. Using H. influenzae mutants with known biofilm defects, these phenotypes were shown to relate to biofilm maturation and autoinducer-2 (AI-2) quorum signaling. In support of the latter mechanism, chemically synthesized AI-2 (dihydroxypentanedione [DPD]) promoted increased M. catarrhalis biofilm formation and resistance to antibiotics. In the chinchilla infection model of OM, polymicrobial infection promoted M. catarrhalis persistence beyond the levels seen in animals infected with M. catarrhalis alone. Notably, no such enhancement of M. catarrhalis persistence was observed in animals infected with M. catarrhalis and a quorum signaling-deficient H. influenzae luxS mutant strain. We thus conclude that H. influenzae promotes M. catarrhalis persistence within polymicrobial biofilms via interspecies quorum signaling. AI-2 may therefore represent an ideal target for disruption of chronic polymicrobial infections. Moreover, these results strongly imply that successful vaccination against the unencapsulated H. influenzae strains that cause airway infections may also significantly impact chronic M. catarrhalis disease by removing a reservoir of the AI-2 signal that promotes M. catarrhalis persistence within biofilm.

  13. The dependence of quorum sensing in Serratia marcescens JG on the transcription of luxS gene.

    Science.gov (United States)

    Sun, Shu-Jing; Liu, Yu-Chen; Sun, Jiao; Zhu, Hu

    2015-06-01

    Bacteria communicate with one another using chemical signal molecules. This phenomenon termed quorum sensing enables the bacteria to monitor the environment for other bacteria and to alter behavior on a population-wide scale in response to cell density. Serratia marcescens JG, a quorum sensing bacterium, can secrete a furanosyl borate diester autoinducer (AI-2) in the exponential phase of growth. In this study, to further investigate the regulation of AI-2 production in S. marcescens JG, the pfs and luxS promoter fusions to an operon luxCDABE reporter were constructed in a low-copy-number vector pBR322K, which allows an examination of transcription of the genes in the pathway for signal synthesis. The results show that the luxS expression is constitutive, and the transcription of luxS is tightly correlated with AI-2 production in S. marcescens JG because the peaks of AI-2 production and transcriptional level of luxS appear at the same time point. The close relation of the profiles of luxS transcription and AI-2 production was also confirmed with real-time PCR technology. These results support the hypothesis that the quorum sensing in S. marcescens JG is luxS dependent.

  14. Sub-MICs of Mentha piperita essential oil and menthol inhibits AHL mediated quorum sensing and biofilm of Gram negative bacteria

    Directory of Open Access Journals (Sweden)

    Fohad Mabood Husain

    2015-05-01

    Full Text Available Bacterial quorum sensing (QS is a density dependent communication system that regulates the expression of certain genes including production of virulence factors in many pathogens. Bioactive plant extract/compounds inhibiting QS regulated gene expression may be a potential candidate as antipathogenic drug. In this study anti-QS activity of peppermint (Mentha piperita oil was first tested using the Chromobacterium violaceum CVO26 biosensor. Further, the findings of the present investigation revealed that peppermint oil at sub-MICs strongly interfered with acyl homoserine lactone (AHL regulated virulence factors and biofilm formation in Pseudomonas aeruginosa and Aeromonas hydrophila. The result of molecular docking analysis attributed the quorum sensing inhibitory activity exhibited by peppermint oil to menthol. Assessment of ability of menthol to interfere with quorum sensing systems of various Gram-negative pathogens comprising diverse AHL molecules revealed that it reduced the AHL dependent production of violacein, virulence factors and biofilm formation indicating broad-spectrum anti-QS activity. Using two E. coli biosensors, MG4/pKDT17 and pEAL08-2, we also confirmed that menthol inhibited both the las and pqs quorum sensing systems. Further, findings of the in vivo studies with menthol on nematode model Caenorhabditis elegans showed significantly enhanced survival of the nematode. Our data identified menthol as a novel broad spectrum quorum sensing inhibitor.

  15. Methanol Extract from Anogeissus leiocarpus (DC Guill. et Perr. (Combretaceae Stem Bark Quenches the Quorum Sensing of Pseudomonas aeruginosa PAO1

    Directory of Open Access Journals (Sweden)

    Vincent Ouedraogo

    2016-10-01

    Full Text Available Background: Due to its extensive arsenal of virulence factors and inherent resistance to antibiotics, Pseudomonas aeruginosa is a threat particularly in immunocompromised patients. Considering the central role of quorum sensing in the production of virulence factors, inhibition of bacterial communication mechanism constitute an opportunity to attenuate pathogenicity of bacteria resistant to available antibiotics. Our study aimed to assess the anti-quorum sensing activity of Anogeissus leiocarpus, traditionally used in Burkina Faso, for the treatment of infected burn wounds. Methods: Investigations were carried out on methanol extract from A. leiocarpus stem bark. The reporter strains Chromobacterium violaceum CV026 and P. aeruginosa PAO1 derivatives were used to evidence any interference with the bacterial quorum sensing and expression of related genes. P. aeruginosa PAO1 was used to measure the impact on pyocyanin production. Results: At a sub-inhibitory concentration (100 µg/mL, A. leiocarpus methanol extract quenched the quorum sensing mechanism of P. aeruginosa PAO1 by down-streaming the rhlR gene, with a subsequent reduction of pyocyanin production. Moreover, the antioxidant polyphenols evidenced are able to reduce the oxidative stress induced by pyocyanin. Conclusion: The antioxidant and anti-quorum sensing activities of A. leiocarpus stem bark could justify its traditional use in the treatment of infected burn wounds.

  16. In search of alternative antibiotic drugs: Quorum-quenching activity in sponges and their bacterial isolates

    Directory of Open Access Journals (Sweden)

    Kumar eSaurav

    2016-04-01

    Full Text Available Owing to the extensive development of drug resistance in pathogens against the available antibiotic arsenal, antimicrobial resistance is now an emerging major threat to public healthcare. Anti-virulence drugs are a new type of therapeutic agent aiming at virulence factors rather than killing the pathogen, thus providing less selective pressure for evolution of resistance. One promising example of this therapeutic concept targets bacterial quorum sensing (QS, because QS controls many virulence factors responsible for bacterial infections. Marine sponges and their associated bacteria are considered a still untapped source for unique chemical leads with a wide range of biological activities. In the present study, we screened extracts of fourteen sponge species collected from the Red and Mediterranean Sea for their quorum-quenching (QQ potential. Half of the species showed QQ activity in at least 2 out of 3 replicates. Six out of the 14 species were selected for bacteria isolation, to test for QQ activity also in isolates, which, once cultured, represent an unlimited source of compounds. We show that approximately 20% of the isolates showed QQ activity based on a Chromobacterium violaceum CV026 screen, and that the presence or absence of QQ activity in a sponge extract did not co-relate with the abundance of isolates with the same activity from the same sponge species. This can be explained by the unknown source of QQ compounds in sponge-holobionts (host or symbionts, and further by the possible non-symbiotic nature of bacteria isolated from sponges. The potential symbiotic nature of the isolates showing QQ activity was tested according to the distribution and abundance of taxonomically close bacterial Operational Taxonomic Units (OTUs in a dataset including 97 sponge species and 178 environmental samples (i.e., seawater, freshwater and marine sediments. Most isolates were found not to be enriched in sponges, and may simply have been trapped in the

  17. The Agr-like quorum-sensing system regulates sporulation and production of enterotoxin and beta2 toxin by Clostridium perfringens type A non-food-borne human gastrointestinal disease strain F5603.

    Science.gov (United States)

    Li, Jihong; Chen, Jianming; Vidal, Jorge E; McClane, Bruce A

    2011-06-01

    Clostridium perfringens type A strains producing enterotoxin (CPE) cause one of the most common bacterial food-borne illnesses, as well as many cases of non-food-borne human gastrointestinal disease. Recent studies have shown that an Agr-like quorum-sensing system controls production of chromosomally encoded alpha-toxin and perfringolysin O by C. perfringens, as well as sporulation by Clostridium botulinum and Clostridium sporogenes. The current study explored whether the Agr-like quorum-sensing system also regulates sporulation and production of two plasmid-encoded toxins (CPE and beta2 toxin) that may contribute to the pathogenesis of non-food-borne human gastrointestinal disease strain F5603. An isogenic agrB null mutant was inhibited for production of beta2 toxin during vegetative growth and in sporulating culture, providing the first evidence that, in C. perfringens, this system can control production of plasmid-encoded toxins as well as chromosomally encoded toxins. This mutant also showed reduced production of alpha-toxin and perfringolysin O during vegetative growth. Importantly, when cultured in sporulation medium, the mutant failed to efficiently form spores and was blocked for CPE production. Complementation partially or fully reversed all phenotypic changes in the mutant, confirming that they were specifically due to inactivation of the agr locus. Western blots suggest that this loss of sporulation and sporulation-specific CPE production for the agrB null mutant involves, at least in part, Agr-mediated regulation of production of Spo0A and alternative sigma factors, which are essential for C. perfringens sporulation.

  18. Exploiting quorum sensing interfering strategies in gram-negative bacteria for the enhancement of environmental applications

    Directory of Open Access Journals (Sweden)

    Weiwei eZhang

    2016-01-01

    Full Text Available Quorum sensing (QS is a widespread intercellular form of communication to coordinate physiological processes and cooperative activities of bacteria at the population level, and it depends on the production, secretion, and detection of small diffusible autoinducers, such as acyl-homoserine lactones (AHLs, auto-inducing oligo-peptides (AIPs and autoinducer 2. In this review, the function of QS autoinducers of gram-negative bacteria in different aspects of wastewater treatment systems is examined. Based on research primarily performed over the past ten years, QS involvement in the formation of biofilm and aerobic granules and changes of the microbial community and degradation/transformation pathways is discussed. In particular, the QS pathway in the role of bacterial infections and disease prevention in aquaculture is addressed. Interference of QS autoinducer-regulated pathways is considered potential treatment for a variety of environmentally related problems. This review is expected to serve as a stepping stone for further study and development strategies based on the mediation of QS-regulated pathways to enhance applications in both wastewater treatment systems and aquaculture.

  19. Exploiting Quorum Sensing Interfering Strategies in Gram-Negative Bacteria for the Enhancement of Environmental Applications.

    Science.gov (United States)

    Zhang, Weiwei; Li, Chenghua

    2015-01-01

    Quorum sensing (QS) is a widespread intercellular form of communication to coordinate physiological processes and cooperative activities of bacteria at the population level, and it depends on the production, secretion, and detection of small diffusible autoinducers, such as acyl-homoserine lactones (AHLs), auto-inducing oligo-peptides (AIPs) and autoinducer 2. In this review, the function of QS autoinducers of gram-negative bacteria in different aspects of wastewater treatment systems is examined. Based on research primarily performed over the past 10 years, QS involvement in the formation of biofilm and aerobic granules and changes of the microbial community and degradation/transformation pathways is discussed. In particular, the QS pathway in the role of bacterial infections and disease prevention in aquaculture is addressed. Interference of QS autoinducer-regulated pathways is considered potential treatment for a variety of environmentally related problems. This review is expected to serve as a stepping stone for further study and development strategies based on the mediation of QS-regulated pathways to enhance applications in both wastewater treatment systems and aquaculture.

  20. Structure, Regulation, and Inhibition of the Quorum-Sensing Signal Integrator LuxO.

    Directory of Open Access Journals (Sweden)

    Hande Boyaci

    2016-05-01

    Full Text Available In a process called quorum sensing, bacteria communicate with chemical signal molecules called autoinducers to control collective behaviors. In pathogenic vibrios, including Vibrio cholerae, the accumulation of autoinducers triggers repression of genes responsible for virulence factor production and biofilm formation. The vibrio autoinducer molecules bind to transmembrane receptors of the two-component histidine sensor kinase family. Autoinducer binding inactivates the receptors' kinase activities, leading to dephosphorylation and inhibition of the downstream response regulator LuxO. Here, we report the X-ray structure of LuxO in its unphosphorylated, autoinhibited state. Our structure reveals that LuxO, a bacterial enhancer-binding protein of the AAA+ ATPase superfamily, is inhibited by an unprecedented mechanism in which a linker that connects the catalytic and regulatory receiver domains occupies the ATPase active site. The conformational change that accompanies receiver domain phosphorylation likely disrupts this interaction, providing a mechanistic rationale for LuxO activation. We also determined the crystal structure of the LuxO catalytic domain bound to a broad-spectrum inhibitor. The inhibitor binds in the ATPase active site and recapitulates elements of the natural regulatory mechanism. Remarkably, a single inhibitor molecule may be capable of inhibiting an entire LuxO oligomer.

  1. Anti-quorum sensing potential of crude Kigelia africana fruit extracts.

    Science.gov (United States)

    Chenia, Hafizah Y

    2013-02-27

    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.

  2. Necrotrophism Is a Quorum-Sensing-Regulated Lifestyle in Bacillus thuringiensis

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    Perchat, Stéphane; Lemy, Christelle; Buisson, Christophe; Nielsen-LeRoux, Christina; Gohar, Michel; Jacques, Philippe; Ramarao, Nalini; Kolstø, Anne-Brit; Lereclus, Didier

    2012-01-01

    How pathogenic bacteria infect and kill their host is currently widely investigated. In comparison, the fate of pathogens after the death of their host receives less attention. We studied Bacillus thuringiensis (Bt) infection of an insect host, and show that NprR, a quorum sensor, is active after death of the insect and allows Bt to survive in the cadavers as vegetative cells. Transcriptomic analysis revealed that NprR regulates at least 41 genes, including many encoding degradative enzymes or proteins involved in the synthesis of a nonribosomal peptide named kurstakin. These degradative enzymes are essential in vitro to degrade several substrates and are specifically expressed after host death suggesting that Bt has an active necrotrophic lifestyle in the cadaver. We show that kurstakin is essential for Bt survival during necrotrophic development. It is required for swarming mobility and biofilm formation, presumably through a pore forming activity. A nprR deficient mutant does not develop necrotrophically and does not sporulate efficiently in the cadaver. We report that necrotrophism is a highly regulated mechanism essential for the Bt infectious cycle, contributing to spore spreading. PMID:22511867

  3. Collective behavior and quorum sensing in a system of communicating microcapsules

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    Kolmakov, German; Bhattacharya, Amitabh; Balazs, Anna

    2009-11-01

    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.

  4. Bioinformatic Prediction of Gene Functions Regulated by Quorum Sensing in the Bioleaching Bacterium Acidithiobacillus ferrooxidans

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    Alvaro Banderas

    2013-08-01

    Full Text Available The biomining bacterium Acidithiobacillus ferrooxidans oxidizes sulfide ores and promotes metal solubilization. The efficiency of this process depends on the attachment of cells to surfaces, a process regulated by quorum sensing (QS cell-to-cell signalling in many Gram-negative bacteria. At. ferrooxidans has a functional QS system and the presence of AHLs enhances its attachment to pyrite. However, direct targets of the QS transcription factor AfeR remain unknown. In this study, a bioinformatic approach was used to infer possible AfeR direct targets based on the particular palindromic features of the AfeR binding site. A set of Hidden Markov Models designed to maintain palindromic regions and vary non-palindromic regions was used to screen for putative binding sites. By annotating the context of each predicted binding site (PBS, we classified them according to their positional coherence relative to other putative genomic structures such as start codons, RNA polymerase promoter elements and intergenic regions. We further used the Multiple EM for Motif Elicitation algorithm (MEME to further filter out low homology PBSs. In summary, 75 target-genes were identified, 34 of which have a higher confidence level. Among the identified genes, we found afeR itself, zwf, genes encoding glycosyltransferase activities, metallo-beta lactamases, and active transport-related proteins. Glycosyltransferases and Zwf (Glucose 6-phosphate-1-dehydrogenase might be directly involved in polysaccharide biosynthesis and attachment to minerals by At. ferrooxidans cells during the bioleaching process.

  5. Individuals in the crowd: studying bacterial quorum-sensing at the single-cell level

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    Delfino Perez, Pablo; Young, Jonathan; Johnson, Elaine L.; Hagen, Stephen J.

    2009-03-01

    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.

  6. "Quorum Non-Sensing": Social Cheating and Deception in Vibrio cholerae.

    Science.gov (United States)

    Katzianer, David S; Wang, Hui; Carey, Ryan M; Zhu, Jun

    2015-06-01

    Quorum sensing (QS) is widely used by bacteria to coordinate behavior in response to external stimuli. In Vibrio cholerae, this process is important for environmental survival and pathogenesis, though, intriguingly, a large percentage of natural isolates are QS deficient. Here, we show that QS-deficient mutants can spread as social cheaters by ceasing production of extracellular proteases under conditions requiring their growth. We further show that mutants stimulate biofilm formation and are over-represented in biofilms compared to planktonic communities; on this basis, we suggest that QS-deficient mutants may have the side effect of enhancing environmental tolerance of natural populations due to the inherent resistance properties of biofilms. Interestingly, high frequencies of QS-deficient individuals did not impact production of QS signaling molecules despite mutants being unable to respond to these inducers, indicating that these variants actively cheat by false signaling under conditions requiring QS. Taken together, our results suggest that social cheating may drive QS deficiency emergence within V. cholerae natural populations. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

  7. Extracts of Cordia gilletii de wild (Boraginaceae) quench the quorum sensing of Pseudomonas aeruginosa PAO1.

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    Okusa, Philippe N; Rasamiravaka, Tsiry; Vandeputte, Olivier; Stévigny, Caroline; Jaziri, Mondher El; Duez, Pierre

    2014-01-01

    The fight against infectious diseases and antimicrobial resistances needs the exploration of new active compounds with new proprieties like disrupting quorum sensing (QS) mechanisms, which is a cell-to-cell communication that regulates bacterial virulence factors. In this work, leaves and root barks extracts of a Congolese medicinal plant, Cordia gilletii, were investigated for their effect on the production of Pseudomonas aeruginosa major virulence factors regulated by QS. The effect of C. gilletii extracts on virulence factors of P. aeruginosa PAO1 was studied by the evaluation of the production of pyocyanine, elastase and biofilm; and by the measurement of the expression of QS-related genes. The dichloromethane extract from root barks was found to quench the production of pyocyanin, a QS-dependent virulence factor in P. aeruginosa PAO1. Moreover, this extract specifically inhibits the expression of several QS-regulated genes (i.e. lasB, rhlA, lasI, lasR, rhlI, and rhlR) and reduces biofilm formation by PAO1. This study contributes to explain the efficacy of C. gilletii in the traditional treatment of infectious diseases caused by P. aeruginosa.

  8. Broad spectrum pro-quorum-sensing molecules as inhibitors of virulence in vibrios.

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    Wai-Leung Ng

    Full Text Available Quorum sensing (QS is a bacterial cell-cell communication process that relies on the production and detection of extracellular signal molecules called autoinducers. QS allows bacteria to perform collective activities. Vibrio cholerae, a pathogen that causes an acute disease, uses QS to repress virulence factor production and biofilm formation. Thus, molecules that activate QS in V. cholerae have the potential to control pathogenicity in this globally important bacterium. Using a whole-cell high-throughput screen, we identified eleven molecules that activate V. cholerae QS: eight molecules are receptor agonists and three molecules are antagonists of LuxO, the central NtrC-type response regulator that controls the global V. cholerae QS cascade. The LuxO inhibitors act by an uncompetitive mechanism by binding to the pre-formed LuxO-ATP complex to inhibit ATP hydrolysis. Genetic analyses suggest that the inhibitors bind in close proximity to the Walker B motif. The inhibitors display broad-spectrum capability in activation of QS in Vibrio species that employ LuxO. To the best of our knowledge, these are the first molecules identified that inhibit the ATPase activity of a NtrC-type response regulator. Our discovery supports the idea that exploiting pro-QS molecules is a promising strategy for the development of novel anti-infectives.

  9. Antibacterial and quorum sensing regulatory activities of some traditional Eastern-European medicinal plants

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    Tolmacheva Anna A.

    2014-06-01

    Full Text Available The objective of this study was to screen extracts of twenty Eastern European medicinal plants, using wild-type and reporter Chromobacterium violaceum bioassays, for novel components that target bacterial cells and their quorum sensing (QS communication systems. Three types of activity and their combinations were revealed: (i direct antimicrobial growth-inhibitory activity, (ii non-specific and specific pro-QS activities, (iii anti-QS activity. Among seven plant extracts showing direct growth-inhibitory activity, the strongest effect was shown by Arctostaphylos uva- -ursi (bearberry leaves. Many plants stimulated violacein production by wild-type C. violaceum ATCC 31532 in a non-specific manner, and only the herb Bidens tripartita (three-lobe beggarticks contained compounds that mimic acyl-homoserine lactone and operated as a QS agonist. Anti-QS activity was found in eleven plants including Quercus robur (oak cortex, Betula verrucosa (birch buds and Eucalyptus viminalis (Manna Gum leaves. Subsequent statistical analysis showed differences between antimicrobial and anti-QS activities, whereas both activities were defined by phylogenetic position of medical resource plant. Finally, extract from Quercus robur cortex revealed at least two fractions, showing different anti-QS mechanisms. These data confirm that multicomponent anti-infectious mechanisms are used by plants, which may be useful for drug development

  10. Antibacterial and quorum sensing regulatory activities of some traditional Eastern-European medicinal plants.

    Science.gov (United States)

    Tolmacheva, Anna A; Rogozhin, Eugene A; Deryabin, Dmitry G

    2014-06-01

    The objective of this study was to screen extracts of twenty Eastern European medicinal plants, using wild-type and reporter Chromobacterium violaceum bioassays, for novel components that target bacterial cells and their quorum sensing (QS) communication systems. Three types of activity and their combinations were revealed: (i) direct antimicrobial growth-inhibitory activity, (ii) non-specific and specific pro-QS activities, (iii) anti-QS activity. Among seven plant extracts showing direct growth-inhibitory activity, the strongest effect was shown by Arctostaphylos uva-ursi (bearberry) leaves. Many plants stimulated violacein production by wild-type C. violaceum ATCC 31532 in a non-specific manner, and only the herb Bidens tripartita (three-lobe beggarticks) contained compounds that mimic acyl-homoserine lactone and operated as a QS agonist. Anti-QS activity was found in eleven plants including Quercus robur (oak) cortex, Betula verrucosa (birch) buds and Eucalyptus viminalis (Manna Gum) leaves. Subsequent statistical analysis showed differences between antimicrobial and anti-QS activities, whereas both activities were defined by phylogenetic position of medical resource plant. Finally, extract from Quercus robur cortex revealed at least two fractions, showing different anti-QS mechanisms. These data confirm that multicomponent anti-infectious mechanisms are used by plants, which may be useful for drug development.

  11. Microbial interactions during sugar cane must fermentation for bioethanol production: does quorum sensing play a role?

    Science.gov (United States)

    Brexó, Ramon Peres; Sant'Ana, Anderson de Souza

    2018-03-01

    Microbial interactions represent important modulatory role in the dynamics of biological processes. During bioethanol production from sugar cane must, the presence of lactic acid bacteria (LAB) and wild yeasts is inevitable as they originate from the raw material and industrial environment. Increasing the concentration of ethanol, organic acids, and other extracellular metabolites in the fermentation must are revealed as wise strategies for survival by certain microorganisms. Despite this, the co-existence of LAB and yeasts in the fermentation vat and production of compounds such as organic acids and other extracellular metabolites result in reduction in the final yield of the bioethanol production process. In addition to the competition for nutrients, reduction of cellular viability of yeast strain responsible for fermentation, flocculation, biofilm formation, and changes in cell morphology are listed as important factors for reductions in productivity. Although these consequences are scientifically well established, there is still a gap about the physiological and molecular mechanisms governing these interactions. This review aims to discuss the potential occurrence of quorum sensing mechanisms between bacteria (mainly LAB) and yeasts and to highlight how the understanding of such mechanisms can result in very relevant and useful tools to benefit the biofuels industry and other sectors of biotechnology in which bacteria and yeast may co-exist in fermentation processes.

  12. Selection of Functional Quorum Sensing Systems by Lysogenic Bacteriophages in Pseudomonas aeruginosa.

    Science.gov (United States)

    Saucedo-Mora, Miguel A; Castañeda-Tamez, Paulina; Cazares, Adrián; Pérez-Velázquez, Judith; Hense, Burkhard A; Cazares, Daniel; Figueroa, Wendy; Carballo, Marco; Guarneros, Gabriel; Pérez-Eretza, Berenice; Cruz, Nelby; Nishiyama, Yoshito; Maeda, Toshinari; Belmont-Díaz, Javier A; Wood, Thomas K; García-Contreras, Rodolfo

    2017-01-01

    Quorum sensing (QS) in Pseudomonas aeruginosa coordinates the expression of virulence factors, some of which are used as public goods. Since their production is a cooperative behavior, it is susceptible to social cheating in which non-cooperative QS deficient mutants use the resources without investing in their production. Nevertheless, functional QS systems are abundant; hence, mechanisms regulating the amount of cheating should exist. Evidence that demonstrates a tight relationship between QS and the susceptibility of bacteria against the attack of lytic phages is increasing; nevertheless, the relationship between temperate phages and QS has been much less explored. Therefore, in this work, we studied the effects of having a functional QS system on the susceptibility to temperate bacteriophages and how this affects the bacterial and phage dynamics. We find that both experimentally and using mathematical models, that the lysogenic bacteriophages D3112 and JBD30 select QS-proficient P. aeruginosa phenotypes as compared to the QS-deficient mutants during competition experiments with mixed strain populations in vitro and in vivo in Galleria mellonella, in spite of the fact that both phages replicate better in the wild-type background. We show that this phenomenon restricts social cheating, and we propose that temperate phages may constitute an important selective pressure toward the conservation of bacterial QS.

  13. The Organization of the Quorum Sensing luxI/R Family Genes in Burkholderia

    Science.gov (United States)

    Choudhary, Kumari Sonal; Hudaiberdiev, Sanjarbek; Gelencsér, Zsolt; Coutinho, Bruna Gonçalves; Venturi, Vittorio; Pongor, Sándor

    2013-01-01

    Members of the Burkholderia genus of Proteobacteria are capable of living freely in the environment and can also colonize human, animal and plant hosts. Certain members are considered to be clinically important from both medical and veterinary perspectives and furthermore may be important modulators of the rhizosphere. Quorum sensing via N-acyl homoserine lactone signals (AHL QS) is present in almost all Burkholderia species and is thought to play important roles in lifestyle changes such as colonization and niche invasion. Here we present a census of AHL QS genes retrieved from public databases and indicate that the local arrangement (topology) of QS genes, their location within chromosomes and their gene neighborhoods show characteristic patterns that differ between the known Burkholderia clades. In sequence phylogenies, AHL QS genes seem to cluster according to the local gene topology rather than according to the species, which suggests that the basic topology types were present prior to the appearance of current Burkholderia species. The data are available at http://net.icgeb.org/burkholderia/. PMID:23820583

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

    Science.gov (United States)

    Koh, Khee Hoon; Tham, Foong-Yee

    2011-04-01

    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. Copyright © 2011. Published by Elsevier B.V.

  15. Selection of Functional Quorum Sensing Systems by Lysogenic Bacteriophages in Pseudomonas aeruginosa

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    Miguel A. Saucedo-Mora

    2017-08-01

    Full Text Available Quorum sensing (QS in Pseudomonas aeruginosa coordinates the expression of virulence factors, some of which are used as public goods. Since their production is a cooperative behavior, it is susceptible to social cheating in which non-cooperative QS deficient mutants use the resources without investing in their production. Nevertheless, functional QS systems are abundant; hence, mechanisms regulating the amount of cheating should exist. Evidence that demonstrates a tight relationship between QS and the susceptibility of bacteria against the attack of lytic phages is increasing; nevertheless, the relationship between temperate phages and QS has been much less explored. Therefore, in this work, we studied the effects of having a functional QS system on the susceptibility to temperate bacteriophages and how this affects the bacterial and phage dynamics. We find that both experimentally and using mathematical models, that the lysogenic bacteriophages D3112 and JBD30 select QS-proficient P. aeruginosa phenotypes as compared to the QS-deficient mutants during competition experiments with mixed strain populations in vitro and in vivo in Galleria mellonella, in spite of the fact that both phages replicate better in the wild-type background. We show that this phenomenon restricts social cheating, and we propose that temperate phages may constitute an important selective pressure toward the conservation of bacterial QS.

  16. ω-Hydroxyemodin Limits Staphylococcus aureus Quorum Sensing-Mediated Pathogenesis and Inflammation

    Science.gov (United States)

    Daly, Seth M.; Elmore, Bradley O.; Kavanaugh, Jeffrey S.; Triplett, Kathleen D.; Figueroa, Mario; Raja, Huzefa A.; El-Elimat, Tamam; Crosby, Heidi A.; Femling, Jon K.; Cech, Nadja B.; Horswill, Alexander R.; Oberlies, Nicholas H.

    2015-01-01

    Antibiotic-resistant pathogens are a global health threat. Small molecules that inhibit bacterial virulence have been suggested as alternatives or adjuncts to conventional antibiotics, as they may limit pathogenesis and increase bacterial susceptibility to host killing. Staphylococcus aureus is a major cause of invasive skin and soft tissue infections (SSTIs) in both the hospital and community settings, and it is also becoming increasingly antibiotic resistant. Quorum sensing (QS) mediated by the accessory gene regulator (agr) controls virulence factor production essential for causing SSTIs. We recently identified ω-hydroxyemodin (OHM), a polyhydroxyanthraquinone isolated from solid-phase cultures of Penicillium restrictum, as a suppressor of QS and a compound sought for the further characterization of the mechanism of action. At concentrations that are nontoxic to eukaryotic cells and subinhibitory to bacterial growth, OHM prevented agr signaling by all four S. aureus agr alleles. OHM inhibited QS by direct binding to AgrA, the response regulator encoded by the agr operon, preventing the interaction of AgrA with the agr P2 promoter. Importantly, OHM was efficacious in a mouse model of S. aureus SSTI. Decreased dermonecrosis with OHM treatment was associated with enhanced bacterial clearance and reductions in inflammatory cytokine transcription and expression at the site of infection. Furthermore, OHM treatment enhanced the immune cell killing of S. aureus in vitro in an agr-dependent manner. These data suggest that bacterial disarmament through the suppression of S. aureus QS may bolster the host innate immune response and limit inflammation. PMID:25645827

  17. qPMS9: An Efficient Algorithm for Quorum Planted Motif Search

    Science.gov (United States)

    Nicolae, Marius; Rajasekaran, Sanguthevar

    2015-01-01

    Discovering patterns in biological sequences is a crucial problem. For example, the identification of patterns in DNA sequences has resulted in the determination of open reading frames, identification of gene promoter elements, intron/exon splicing sites, and SH RNAs, location of RNA degradation signals, identification of alternative splicing sites, etc. In protein sequences, patterns have led to domain identification, location of protease cleavage sites, identification of signal peptides, protein interactions, determination of protein degradation elements, identification of protein trafficking elements, discovery of short functional motifs, etc. In this paper we focus on the identification of an important class of patterns, namely, motifs. We study the (l, d) motif search problem or Planted Motif Search (PMS). PMS receives as input n strings and two integers l and d. It returns all sequences M of length l that occur in each input string, where each occurrence differs from M in at most d positions. Another formulation is quorum PMS (qPMS), where the motif appears in at least q% of the strings. We introduce qPMS9, a parallel exact qPMS algorithm that offers significant runtime improvements on DNA and protein datasets. qPMS9 solves the challenging DNA (l, d)-instances (28, 12) and (30, 13). The source code is available at https://code.google.com/p/qpms9/.

  18. Quorum Sensing Regulation of Competence and Bacteriocins in Streptococcus pneumoniae and mutans

    Science.gov (United States)

    Shanker, Erin; Federle, Michael J.

    2017-01-01

    The human pathogens Streptococcus pneumoniae and Streptococcus mutans have both evolved complex quorum sensing (QS) systems that regulate the production of bacteriocins and the entry into the competent state, a requirement for natural transformation. Natural transformation provides bacteria with a mechanism to repair damaged genes or as a source of new advantageous traits. In S. pneumoniae, the competence pathway is controlled by the two-component signal transduction pathway ComCDE, which directly regulates SigX, the alternative sigma factor required for the initiation into competence. Over the past two decades, effectors of cellular killing (i.e., fratricides) have been recognized as important targets of the pneumococcal competence QS pathway. Recently, direct interactions between the ComCDE and the paralogous BlpRH pathway, regulating bacteriocin production, were identified, further strengthening the interconnections between these two QS systems. Interestingly, a similar theme is being revealed in S. mutans, the primary etiological agent of dental caries. This review compares the relationship between the bacteriocin and the competence QS pathways in both S. pneumoniae and S. mutans, and hopes to provide clues to regulatory pathways across the genus Streptococcus as a potential tool to efficiently investigate putative competence pathways in nontransformable streptococci. PMID:28067778

  19. Quorum sensing communication between bacteria and human cells: signals, targets and functions

    Directory of Open Access Journals (Sweden)

    Angelika eHolm

    2014-06-01

    Full Text Available Both direct and long-range interactions between pathogenic Pseudomonas aeruginosa bacteria and their eukaryotic hosts are important in the outcome of infections. For cell-to-cell communication, these bacteria employ the quorum sensing (QS system to pass on information of the density of the bacterial population and collectively switch on virulence factor production, biofilm formation and resistance development. Thus, QS allows bacteria to behave as a community to perform tasks which would be impossible for individual cells, e.g. to overcome defense and immune systems and establish infections in higher organisms. This review highlights these aspects of QS and our own recent research on how P.aeruginosa communicates with human cells using the small QS signal molecules N-acyl homoserine lactones (AHL. We focus on how this conversation changes the behavior and function of neutrophils, macrophages and epithelial cells and on how the signaling machinery in human cells responsible for the recognition of AHL. Understanding the bacteria-host relationships at both cellular and molecular levels is essential for the identification of new targets and for the development of novel strategies to fight bacterial infections in the future.

  20. A new transcriptional repressor of the pseudomonas aeruginosa quorum sensing receptor gene lasR.

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    Francesca Longo

    Full Text Available 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.

  1. Chemical Composition and Disruption of Quorum Sensing Signaling in Geographically Diverse United States Propolis

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    Michael A. Savka

    2015-01-01

    Full Text Available Propolis or bee glue has been used for centuries for various purposes and is especially important in human health due to many of its biological and pharmacological properties. In this work we showed quorum sensing inhibitory (QSI activity of ten geographically distinct propolis samples from the United States using the acyl-homoserine lactone- (AHL- dependent Chromobacterium violaceum strain CV026. Based on GC-MS chemical profiling the propolis samples can be classified into several groups that are as follows: (1 rich in cinnamic acid derivatives, (2 rich in flavonoids, and (3 rich in triterpenes. An in-depth analysis of the propolis from North Carolina led to the isolation and identification of a triterpenic acid that was recently isolated from Hondurian propolis (Central America and ethyl ether of p-coumaric alcohol not previously identified in bee propolis. QSI activity was also observed in the second group US propolis samples which contained the flavonoid pinocembrin in addition to other flavonoid compounds. The discovery of compounds that are involved in QSI activity has the potential to facilitate studies that may lead to the development of antivirulence therapies that can be complementary and/or alternative treatments against antibiotic resistant bacterial pathogens and/or emerging pathogens that have yet to be identified.

  2. Flavonoids from Piper delineatum modulate quorum-sensing-regulated phenotypes in Vibrio harveyi.

    Science.gov (United States)

    Martín-Rodríguez, Alberto J; Ticona, Juan C; Jiménez, Ignacio A; Flores, Ninoska; Fernández, José J; Bazzocchi, Isabel L

    2015-09-01

    Quorum sensing (QS), or bacterial cell-to-cell communication, is a key process for bacterial colonization of substrata through biofilm formation, infections, and production of virulence factors. In an ongoing investigation of bioactive secondary metabolites from Piper species, four new flavonoids (1-4), along with five known ones (5-9) were isolated from the leaves of Piper delineatum. Their stereostructures were established by spectroscopic and spectrometric methods, including 1D and 2D NMR experiments, and comparison with data reported in the literature. The compounds were screened for their ability to interfere with QS signaling in the bacterial model Vibrio harveyi. Four compounds from this series (2, 3, 6, and 7) exhibited remarkable activity in the micromolar range, being compounds 3 and 7 particularly attractive since they did not affect bacterial growth. The results suggest that these flavonoids disrupt QS-mediated bioluminescence by interaction with elements downstream LuxO in the QS circuit of V. harveyi, and also, they exhibited a strong dose-dependent inhibition of biofilm formation. The present findings shed light on the QS inhibition mechanisms of flavonoids, underlining their potential applications. Copyright © 2015 Elsevier Ltd. All rights reserved.

  3. Quorum sensing and density-dependent dispersal in an aquatic model system.

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    Simon Fellous

    Full Text Available Many organisms use cues to decide whether to disperse or not, especially those related to the composition of their environment. Dispersal hence sometimes depends on population density, which can be important for the dynamics and evolution of sub-divided populations. But very little is known about the factors that organisms use to inform their dispersal decision. We investigated the cues underlying density-dependent dispersal in inter-connected microcosms of the freshwater protozoan Paramecium caudatum. In two experiments, we manipulated (i the number of cells per microcosm and (ii the origin of their culture medium (supernatant from high- or low-density populations. We found a negative relationship between population density and rates of dispersal, suggesting the use of physical cues. There was no significant effect of culture medium origin on dispersal and thus no support for chemical cues usage. These results suggest that the perception of density - and as a result, the decision to disperse - in this organism can be based on physical factors. This type of quorum sensing may be an adaptation optimizing small scale monitoring of the environment and swarm formation in open water.

  4. Inhibition of quorum sensing mediated biofilm development and virulence in uropathogens by Hyptis suaveolens.

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    Salini, Ramesh; Sindhulakshmi, Muthukrishnan; Poongothai, Thirumaran; Pandian, Shunmugiah Karutha

    2015-04-01

    Bacterial urinary tract infections (UTIs) are the most common nosocomial infections, accounting for about 40 % of all hospital-acquired infections. The bacterial spectrum of nosocomial UTIs is broad and the treatment of UTIs is becoming difficult owing to the emergence of drug resistance. Therefore, it is reasonable to investigate novel and alternative therapeutic strategies to treat UTIs. Since UTIs are caused by uropathogens with quorum sensing (QS)-dependent biofilm forming abilities, interruption of QS systems may be a novel approach to combat drug resistance. In the present study, a methanol extract (and hexane extract derived from it) of the medicinal plant Hyptis suaveolens (L.) were shown to have anti-QS activity against the biosensor strain Chromobacterium violaceum (ATCC 12472). Furthermore, the hexane extract of H. suaveolens (HEHS) inhibited biofilm formation by uropathogens such as Escherichia coli, Proteus vulgaris, Proteus mirabilis, Klebsiella pneumoniae and Serratia marcescens. HEHS promotes the loosening of biofilm architecture and strongly inhibits in vitro biofilm formation by uropathogens, which was more apparent from microscopic images. In addition to this, HEHS reduces the production of QS-dependent virulence factors like protease and hemolysin, along with motility. The partial purification and GC-MS analysis of the active fraction revealed the presence of several therapeutically important compounds which may synergistically act on the uropathogens and possibly reduce the QS-dependent phenotypes. These findings suggest HEHS as potential phytotherapeutic agent which can be employed to formulate protective strategies against biofilm linked infections caused by uropathogens.

  5. Impact of phenolic compounds in the acyl homoserine lactone-mediated quorum sensing regulatory pathways.

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    Hossain, Md Akil; Lee, Seung-Jin; Park, Na-Hye; Mechesso, Abraham Fikru; Birhanu, Biruk Tesfaye; Kang, JeongWoo; Reza, Md Ahsanur; Suh, Joo-Won; Park, Seung-Chun

    2017-09-06

    Quorum sensing (QS) is a cell density-dependent regulation of virulent bacterial gene expression by autoinducers that potentially pertains in the epidemic of bacterial virulence. This study was initially designed to evaluate the effect of 5 phenolic compounds in the modulation of QS and virulence factors of Chromobacterium violaceum and Pseudomonas aeruginosa, and to determine the mechanisms of their effects. Biosensor strains were used to assess antibacterial and anti-QS effect of these compounds. Only methyl gallate (MG) among these compounds demonstrated profound anti-QS effect in the preliminary study, and thus only MG was utilized further to evaluate the effects on the synthesis and activity of acyl homoserine lactone (AHL) in C. violaceum and on the modulation of biofilm, motility, proteolytic, elastase, pyocyanin, and rhamnolipid activity in P. aeruginosa. Finally, the effect of MG on the expression of QS-regulated genes of P. aeruginosa was verified. MG suppressed both the synthesis and activity of AHL in C. violaceum. It also restricted the biofilm formation and other QS-associated virulence factor of P. aeruginosa. MG concentration-dependently suppressed the expression of lasI/R, rhlI/R, and pqsA of P. aeruginosa and was non-toxic in in vitro study. This is the first report of the anti-QS mechanism of MG.

  6. Inhibition of Bacterial Quorum Sensing by Extracts from Aquatic Fungi: First Report from Marine Endophytes

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    Alberto J. Martín-Rodríguez

    2014-11-01

    Full Text Available In our search for quorum-sensing (QS disrupting molecules, 75 fungal isolates were recovered from reef organisms (endophytes, saline lakes and mangrove rhizosphere. Their QS inhibitory activity was evaluated in Chromobacterium violaceum CVO26. Four strains of endophytic fungi stood out for their potent activity at concentrations from 500 to 50 μg mL−1. The molecular characterization, based on the internal transcribed spacer (ITS region sequences (ITS1, 5.8S and ITS2 between the rRNA of 18S and 28S, identified these strains as belonging to four genera: Sarocladium (LAEE06, Fusarium (LAEE13, Epicoccum (LAEE14, and Khuskia (LAEE21. Interestingly, three came from coral species and two of them came from the same organism, the coral Diploria strigosa. Metabolic profiles obtained by Liquid Chromatography-High Resolution Mass Spectrometry (LC-HRMS suggest that a combination of fungal secondary metabolites and fatty acids could be the responsible for the observed activities. The LC-HRMS analysis also revealed the presence of potentially new secondary metabolites. This is, to the best of our knowledge, the first report of QS inhibition by marine endophytic fungi.

  7. Broad spectrum pro-quorum-sensing molecules as inhibitors of virulence in vibrios.

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    Ng, Wai-Leung; Perez, Lark; Cong, Jianping; Semmelhack, Martin F; Bassler, Bonnie L

    2012-01-01

    Quorum sensing (QS) is a bacterial cell-cell communication process that relies on the production and detection of extracellular signal molecules called autoinducers. QS allows bacteria to perform collective activities. Vibrio cholerae, a pathogen that causes an acute disease, uses QS to repress virulence factor production and biofilm formation. Thus, molecules that activate QS in V. cholerae have the potential to control pathogenicity in this globally important bacterium. Using a whole-cell high-throughput screen, we identified eleven molecules that activate V. cholerae QS: eight molecules are receptor agonists and three molecules are antagonists of LuxO, the central NtrC-type response regulator that controls the global V. cholerae QS cascade. The LuxO inhibitors act by an uncompetitive mechanism by binding to the pre-formed LuxO-ATP complex to inhibit ATP hydrolysis. Genetic analyses suggest that the inhibitors bind in close proximity to the Walker B motif. The inhibitors display broad-spectrum capability in activation of QS in Vibrio species that employ LuxO. To the best of our knowledge, these are the first molecules identified that inhibit the ATPase activity of a NtrC-type response regulator. Our discovery supports the idea that exploiting pro-QS molecules is a promising strategy for the development of novel anti-infectives.

  8. Marine organisms as source of extracts to disrupt bacterial communication: bioguided isolation and identification of quorum sensing inhibitors from Ircinia felix

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    Jairo Quintana

    Full Text Available AbstractIn this study, 39 extracts from marine organisms were evaluated as quorum sensing inhibitors, collected in the Colombian Caribbean Sea and the Brazilian Coast including 26 sponges, seven soft corals, five algae and one zooanthid. The results showed that crude extracts from the soft coral Eunicea laciniata, and the sponges Svenzea tubulosa, Ircinia felix and Neopetrosia carbonaria were the most promising source of quorum sensing inhibitors compounds without affecting bacterial growth, unlike the raw extracts of Agelas citrina, Agelas tubulata, Iotrochota arenosa, Topsentia ophiraphidites, Niphates caycedoi, Cliona tenuis, Ptilocaulis walpersi, Petrosia pellasarca, and the algae Laurencia catarinensis and Laurencia obtusa, which displayed potent antibacterial activity against the biosensors employed. The crude extract from the sponge I. felix was fractionated, obtaining furanosesterterpenes which were identified and evaluated as quorum sensing inhibitors, showing a moderate activity without affecting the biosensor's growth.

  9. Antimicrobial and anti-Quorum Sensing activities of selected medicinal plants of Ethiopia: Implication for development of potent antimicrobial agents.

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    Bacha, Ketema; Tariku, Yinebeb; Gebreyesus, Fisseha; Zerihun, Shibru; Mohammed, Ali; Weiland-Bräuer, Nancy; Schmitz, Ruth A; Mulat, Mulugeta

    2016-07-11

    Traditional medicinal plants have been used as an alternative medicine in many parts of the world, including Ethiopia. There are many documented scientific reports on antimicrobial activities of the same. To our knowledge, however, there is no report on the anti-Quorum Sensing (Quorum Quenching, QQ) potential of traditional Ethiopian medicinal plants. As many of the opportunistic pathogenic bacteria depend on Quorum Sensing (QS) systems to coordinate their virulence expression, interference with QS could be a novel approach to control bacterial infections. Thus, the aim of this study was to evaluate selected medicinal plants from Ethiopia for their antimicrobial activities against bacterial and fungal pathogens; and to assess the interference of these plant extracts with QS of bacteria. Antimicrobial activities of plant extracts (oil, resins and crude extracts) were evaluated following standard agar diffusion technique. The minimum inhibitory concentrations (MIC) of potent extracts were determined using 96 well micro-titer plates and optical densities were measured using an ELISA Microplate reader. Interference with Quorum Sensing activities of extracts was determined using the recently established E. coli based reporter strain AI1-QQ.1 and signaling molecule N-(ß-ketocaproyl)-L-homoserine lactone (3-oxo-C6-HSL). Petroleum ether extract of seed of Nigella sativa exhibited the highest activity against both the laboratory isolated Bacillus cereus [inhibition zone (IZ), 44 ± 0.31 mm] and B. cereus ATCC 10987 (IZ, 40 ± 2.33 mm). Similarly, oil extract from mature ripe fruit husk of Aframomum corrorima and mature unripe fruit of A. corrorima revealed promising activities against Candida albicans ATCC 90028 (IZ, 35 ± 1.52 mm) and Staphylococcus aureus DSM 346 (IZ, 25 ± 1.32 mm), respectively. Antimicrobial activities of oil extract from husk of A. corrorima and petroleum ether extract of seed of N. sativa were significantly higher than that of

  10. Marine-Derived Quorum-Sensing Inhibitory Activities Enhance the Antibacterial Efficacy of Tobramycin against Pseudomonas aeruginosa

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    Alessandro Busetti

    2014-12-01

    Full Text Available 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.

  11. Disruption of a Quorum Sensing mechanism triggers tumorigenesis: a simple discrete model corroborated by experiments in mammary cancer stem cells

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    Kirnasovsky Oleg U

    2010-04-01

    Full Text Available Abstract Background The balance between self-renewal and differentiation of stem cells is expected to be tightly controlled in order to maintain tissue homeostasis throughout life, also in the face of environmental hazards. Theory, predicting that homeostasis is maintained by a negative feedback on stem cell proliferation, implies a Quorum Sensing mechanism in higher vertebrates. Results Application of this theory to a cellular automata model of stem cell development in disrupted environments shows a sharply dichotomous growth dynamics: maturation within 50-400 cell cycles, or immortalization. This dichotomy is mainly driven by intercellular communication, low intensity of which causes perpetual proliferation. Another driving force is the cells' kinetic parameters. Reduced tissue life span of differentiated cells results in uncontrolled proliferation. Model's analysis, showing that under the Quorum Sensing control, stem cell fraction within a steady state population is fixed, is corroborated by experiments in breast carcinoma cells. Experimental results show that the plating densities of CD44+ cells and of CD44+/24lo/ESA+ cells do not affect stem cell fraction near confluence. Conclusions This study suggests that stem cell immortalization may be triggered by reduced intercellular communication, rather than exclusively result from somatic evolution, and implies that stem cell proliferation can be attenuated by signal manipulation, or enhanced by cytotoxics targeted to differentiated cells. In vivo verification and identification of the Quorum Sensing mediating molecules will pave the way to a higher level control of stem cell proliferation in cancer and in tissue engineering. Reviewers This article was reviewed by Glenn Webb and Marek Kimmel.

  12. Effect of organic acids on biofilm formation and quorum signaling of pathogens from fresh fruits and vegetables.

    Science.gov (United States)

    Amrutha, Balagopal; Sundar, Kothandapani; Shetty, Prathapkumar Halady

    2017-10-01

    Organic acids are known to be used as food preservatives due to their antimicrobial potential. This study evaluated the ability of three organic acids, namely, acetic acid, citric acid and lactic acid to manage E. coli and Salmonella sp. from fresh fruits and vegetables. Effect of these organic acids on biofilm forming ability and anti-quorum potential was also investigated. The effect of organic acids on inactivation of E. coli and Salmonella sp. on the surface of a selected vegetable (cucumber) was determined. The minimum inhibitory concentration of the organic acids were found to be 1.5, 2 and 0.2% in E. coli while it was observed to be 1, 1.5 and 1% in Salmonella sp. for acetic, citric and lactic acids respectively. Maximum inhibition of biofilm formation was recorded at 39.13% with lactic acid in E. coli and a minimum of 22.53% with citric acid in Salmonella sp. EPS production was affected in E. coli with lactic acid showing reduction by 13.42% while citric acid and acetic acid exhibited only 6.25% and 10.89% respectively. Swimming and swarming patterns in E. coli was notably affected by both acetic and lactic acids. Lactic and acetic acids showed higher anti-quorum sensing (QS) potential when compared to citric acid. 2% lactic acid showed a maximum inhibition of violacein production by 37.7%. Organic acids can therefore be used as potential quorum quenching agents in food industry. 2% lactic acid treatment on cucumber demonstrated that it was effective in inactivating E. coli and Salmonella sp. There was 1 log reduction in microbial count over a period of 6 days after the lactic acid treatment. Thus, organic acids can act as effective potential sanitizers in reducing the microbial load associated with fresh fruits and vegetables. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Dissection of quorum-sensing genes in Burkholderia glumae reveals non-canonical regulation and the new regulatory gene tofM for toxoflavin production.

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    Ruoxi Chen

    Full Text Available Burkholderia glumae causes bacterial panicle blight of rice and produces major virulence factors, including toxoflavin, under the control of the quorum-sensing (QS system mediated by the luxI homolog, tofI, and the luxR homolog, tofR. In this study, a series of markerless deletion mutants of B. glumae for tofI and tofR were generated using the suicide vector system, pKKSacB, for comprehensive characterization of the QS system of this pathogen. Consistent with the previous studies by other research groups, ΔtofI and ΔtofR strains of B. glumae did not produce toxoflavin in Luria-Bertani (LB broth. However, these mutants produced high levels of toxoflavin when grown in a highly dense bacterial inoculum (∼ 10(11 CFU/ml on solid media, including LB agar and King's B (KB agar media. The ΔtofI/ΔtofR strain of B. glumae, LSUPB201, also produced toxoflavin on LB agar medium. These results indicate the presence of previously unknown regulatory pathways for the production of toxoflavin that are independent of tofI and/or tofR. Notably, the conserved open reading frame (locus tag: bglu_2g14480 located in the intergenic region between tofI and tofR was found to be essential for the production of toxoflavin by tofI and tofR mutants on solid media. This novel regulatory factor of B. glumae was named tofM after its homolog, rsaM, which was recently identified as a novel negative regulatory gene for the QS system of another rice pathogenic bacterium, Pseudomonas fuscovaginae. The ΔtofM strain of B. glumae, LSUPB286, produced a less amount of toxoflavin and showed attenuated virulence when compared with its wild type parental strain, 336gr-1, suggesting that tofM plays a positive role in toxoflavin production and virulence. In addition, the observed growth defect of the ΔtofI strain, LSUPB145, was restored by 1 µM N-octanoyl homoserine lactone (C8-HSL.

  14. Impact of Pseudomonas aeruginosa quorum sensing on biofilm persistence in an in vivo intraperitoneal foreign-body infection model

    DEFF Research Database (Denmark)

    Christensen, Louise Dahl; Moser, Claus; Jensen, Peter Østrup

    2007-01-01

    Pseudomonas aeruginosa is an opportunistic human pathogen that causes chronic biofilm-based infections in host organisms. P. aeruginosa employs quorum sensing (QS) to control expression of its virulence, and to establish and maintain chronic infections. Under such conditions, the biofilm mode...... of growth contributes significantly to P. aeruginosa tolerance to the action of the innate and adaptive defence system and numerous antibiotics. In the present study, an in vivo foreign-body infection model was established in the peritoneal cavity of mice. Experimental data showed that QS-deficient P...

  15. [Advances in the research of LuxR family protein in quorum-sensing system of gram-negative bacteria].

    Science.gov (United States)

    Chen, Z; Xiang, J

    2016-09-20

    Quorum sensing (QS) is a cell-density-dependent method for information transmission among bacteria, as well as a mechanism for the bacteria to adapt to environment. LuxR family protein plays a key role in gram-negative bacterial QS system as a kind of transcription regulators and participates in a variety of biological behaviors with LuxI protein and signal molecules, such as bioluminescence, biofilm formation, virulence factors production, and so on. The advances in the research of LuxR family protein in QS system of gram-negative bacteria were summarized in this review.

  16. "Hot Stuff": The Many Uses of a Radiolabel Assay in Detecting Acyl-Homoserine Lactone Quorum-Sensing Signals.

    Science.gov (United States)

    Schaefer, Amy L; Harwood, Caroline S; Greenberg, E Peter

    2018-01-01

    Many Proteobacteria synthesize acyl-homoserine lactone (AHL) molecules for use as signals in cell density-dependent gene regulation known as quorum sensing (QS) and response. AHL detection protocols are essential to QS researchers and several techniques are available, including a 14C-AHL radiolabel assay. This assay is based on the uptake of radiolabeled methionine by living cells and conversion of the radiolabel into S-adenosylmethionine (SAM). The radiolabeled SAM is then incorporated into AHL signal by an AHL synthase enzyme. Here we describe a methodology to perform the AHL radiolabel assay, which is unbiased, relatively fast, and very sensitive compared to other AHL detection protocols.

  17. Efficacy of the Quorum Sensing Inhibitor FS10 Alone and in Combination with Tigecycline in an Animal Model of Staphylococcal Infected Wound.

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    Oriana Simonetti

    Full Text Available In staphylococci, quorum sensing regulates both biofilm formation and toxin production, moreover it has been demonstrated to be inhibited by RNAIII inhibiting peptide (RIP. Aim our study was to evaluate the in vitro activity and its in vivo efficacy of the combined administration of FS10, a novel RIP derivative, and tigecycline in an animal model of methicillin-resistant (MR and methicillin-sensitive (MS Staphylococcus aureus wound infection. Using a 1.x2 cm template, one full thickness wound was established through the panniculus carnosus on the back subcutaneous tissue of each animal. Infection was determined by inoculation of 5x107 CFU/ml of bacteria, that produced an abscess within 24 h, after this, treatment was initiated. The study included, for each strain, a control group without infection, a control infected group that did not receive any treatment and a control infected group with drug-free foam dressing, and three infected groups treated, respectively, with: FS10-soaked foam dressing (containing 20 μg FS10, daily intraperitoneal tigecycline (7 mg/Kg, FS10-soaked foam dressing (containing 20 μg FS10 and daily intraperitoneal injections of tigecycline (7 mg/Kg. The main outcome measures were quantitative culture and histological examination of tissue repair. The highest inhibition of infection was achieved in the group that received FS10-soaked and parenteral tigecycline reducing the bacterial load from 107 CFU/ml to about 103 CFU/g for MSSA and to about 104 CFU/g for MRSA. The group treated with FS10-soaked foam dressing associated with parenteral tigecycline showed, histologically, better overall healing with epithelialization and collagen scores significantly higher than those of the other groups in both strains. In conclusion, the combined use of topical FS10 with i.p. tigecycline induced positive interaction in vivo, resulting in an enhanced therapeutic benefit versus staphylococcal infections in murine wound models.

  18. The Alternative Sigma Factor SigX Controls Bacteriocin Synthesis and Competence, the Two Quorum Sensing Regulated Traits in Streptococcus mutans.

    Science.gov (United States)

    Reck, Michael; Tomasch, Jürgen; Wagner-Döbler, Irene

    2015-07-01

    Two small quorum sensing (QS) peptides regulate competence in S. mutans in a cell density dependent manner: XIP (sigX inducing peptide) and CSP (competence stimulating peptide). Depending on the environmental conditions isogenic S. mutans cells can split into a competent and non-competent subpopulation. The origin of this population heterogeneity has not been experimentally determined and it is unknown how the two QS systems are connected. We developed a toolbox of single and dual fluorescent reporter strains and systematically knocked out key genes of the competence signaling cascade in the reporter strain backgrounds. By following signal propagation on the single cell level we discovered that the master regulator of competence, the alternative sigma factor SigX, directly controls expression of the response regulator for bacteriocin synthesis ComE. Consequently, a SigX binding motif (cin-box) was identified in the promoter region of comE. Overexpressing the genetic components involved in competence development demonstrated that ComRS represents the origin of bimodality and determines the modality of the downstream regulators SigX and ComE. Moreover these analysis showed that there is no direct regulatory link between the two QS signaling cascades. Competence is induced through a hierarchical XIP signaling cascade, which has no regulatory input from the CSP cascade. CSP exclusively regulates bacteriocin synthesis. We suggest renaming it mutacin inducing peptide (MIP). Finally, using phosphomimetic comE mutants we show that unimodal bacteriocin production is controlled posttranslationally, thus solving the puzzling observation that in complex media competence is observed in a subpopulation only, while at the same time all cells produce bacteriocins. The control of both bacteriocin synthesis and competence through the alternative sigma-factor SigX suggests that S. mutans increases its genetic repertoire via QS controlled predation on neighboring species in its

  19. Conjugative transfer of p42a from rhizobium etli CFN42, which is required for mobilization of the symbiotic plasmid, is regulated by quorum sensing.

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    Tun-Garrido, Cristina; Bustos, Patricia; González, Víctor; Brom, Susana

    2003-03-01

    Rhizobium etli CFN42 contains six plasmids. Only one of them, p42a, is self-conjugative at high frequency. This plasmid is strictly required for mobilization of the symbiotic plasmid (pSym). To study the transfer mechanism of p42a, a self-transmissible cosmid clone containing its transfer region was isolated. Its sequence showed that most of the tra genes are highly similar to genes of Agrobacterium tumefaciens pTiC58 and other related plasmids. Four putative regulatory genes were identified; three of these (traI, traR, and cinR) belong to the LuxR-LuxI family. Mutagenesis of these genes confirmed their requirement for p42a transfer. We found that the conjugative transfer of p42a is dependent on quorum sensing, and consequently pSym transfer also was found to be similarly regulated, establishing a complex link between environmental conditions and pSym transfer. Although R. etli has been shown to produce different N-acyl-homoserine lactones, only one of them, a 3-oxo-C(8)-homoserine lactone encoded by the traI gene described here, was involved in transfer. Mutagenesis of the fourth regulatory gene, traM, had no effect on transfer. Analysis of transcriptional fusions of the regulatory genes to a reporter gene suggests a complex regulation scheme for p42a conjugative transfer. Conjugal transfer gene expression was found to be directly upregulated by TraR and the 3-oxo-C(8)-homoserine lactone synthesized by TraI. The traI gene was autoregulated by these elements and positively regulated by CinR, while cinR expression required traI. Finally, we did not detect expression of traM, indicating that in p42a TraM may be expressed so weakly that it cannot inhibit conjugal transfer, leading to the unrepressed transfer of p42a.

  20. Paraoxonase 2 modulates a proapoptotic function in LS174T cells in response to quorum sensing molecule N-(3-oxododecanoyl)-L-homoserine lactone.

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    Tao, Shiyu; Luo, Yanwen; Bin He; Liu, Jie; Qian, Xi; Ni, Yingdong; Zhao, Ruqian

    2016-07-01

    A mucus layer coats the gastrointestinal tract and serves as the first line of intestinal defense against infection. N-acyl-homoserine lactone (AHL) quorum-sensing molecules produced by gram-negative bacteria in the gut can influence the homeostasis of intestinal epithelium. In this study, we investigated the effects of two representative long- and short-chain AHLs, N-3-(oxododecanoyl)-homoserine lactone (C12-HSL) and N-butyryl homoserine lactone (C4-HSL), on cell viability and mucus secretion in LS174T cells. C12-HSL but not C4-HSL significantly decreased cell viability by inducing mitochondrial dysfunction and activating cell apoptosis which led to a decrease in mucin expression. Pretreatment with lipid raft disruptor (Methyl-β-cyclodextrin, MβCD) and oxidative stress inhibitor (N-acetyl-L-cysteine, NAC) slightly rescued the viability of cells damaged by C12-HSL exposure, while the paraoxonase 2 (PON2) inhibitor (Triazolo[4,3-a]quinolone, TQ416) significantly affected recovering cells viability and mucin secretion. When LS174T cells were treated with C12-HSL and TQ416 simultaneously, TQ416 showed the maximal positive effect on cells viability. However, if cells were first treated with C12-HSL for 40 mins, and then TQ46 was added, the TQ416 had no effect on cell viability. These results suggest that the C12-HSL-acid process acts at an early step to activate apoptosis as part of C12-HSL's effect on intestinal mucus barrier function.