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Sample records for acylhomoserine lactone quorum-sensing

  1. Acyl-Homoserine Lactone Quorum Sensing in the Roseobacter Clade

    Jindong Zan

    2014-01-01

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

  2. Acyl-Homoserine Lactone Recognition and Response Hindering the Quorum-Sensing Regulator EsaR

    Daniel J Schu; Scruggs, Jessica M.; Jared S Geissinger; Katherine G Michel; Stevens, Ann M.

    2014-01-01

    During quorum sensing in the plant pathogen Pantoea stewartii subsp. stewartii, EsaI, an acyl-homoserine lactone (AHL) synthase, and the transcription factor EsaR coordinately control capsular polysaccharide production. The capsule is expressed only at high cell density when AHL levels are high, leading to inactivation of EsaR. In lieu of detailed structural information, the precise mechanism whereby EsaR recognizes AHL and is hindered by it, in a response opposite to that of most other LuxR ...

  3. Acyl-homoserine lactone recognition and response hindering the quorum-sensing regulator EsaR.

    Schu, Daniel J; Scruggs, Jessica M; Geissinger, Jared S; Michel, Katherine G; Stevens, Ann M

    2014-01-01

    During quorum sensing in the plant pathogen Pantoea stewartii subsp. stewartii, EsaI, an acyl-homoserine lactone (AHL) synthase, and the transcription factor EsaR coordinately control capsular polysaccharide production. The capsule is expressed only at high cell density when AHL levels are high, leading to inactivation of EsaR. In lieu of detailed structural information, the precise mechanism whereby EsaR recognizes AHL and is hindered by it, in a response opposite to that of most other LuxR homologues, remains unresolved. Hence, a random mutagenesis genetic approach was designed to isolate EsaR* variants that are immune to the effects of AHL. Error-prone PCR was used to generate the desired mutants, which were subsequently screened for their ability to repress transcription in the presence of AHL. Following sequencing, site-directed mutagenesis was used to generate all possible mutations of interest as single, rather than multiple amino acid substitutions. Eight individual amino acids playing a critical role in the AHL-insensitive phenotype have been identified. The ability of EsaR* variants to bind AHL and the effect of individual substitutions on the overall conformation of the protein were examined through in vitro assays. Six EsaR* variants had a decreased ability to bind AHL. Fluorescence anisotropy was used to examine the relative DNA binding affinity of the final two EsaR* variants, which retained some AHL binding capability but remained unresponsive to it, perhaps due to an inability of the N-terminal domain to transduce information to the C-terminal domain. PMID:25238602

  4. Acyl-homoserine lactone recognition and response hindering the quorum-sensing regulator EsaR.

    Daniel J Schu

    Full Text Available During quorum sensing in the plant pathogen Pantoea stewartii subsp. stewartii, EsaI, an acyl-homoserine lactone (AHL synthase, and the transcription factor EsaR coordinately control capsular polysaccharide production. The capsule is expressed only at high cell density when AHL levels are high, leading to inactivation of EsaR. In lieu of detailed structural information, the precise mechanism whereby EsaR recognizes AHL and is hindered by it, in a response opposite to that of most other LuxR homologues, remains unresolved. Hence, a random mutagenesis genetic approach was designed to isolate EsaR* variants that are immune to the effects of AHL. Error-prone PCR was used to generate the desired mutants, which were subsequently screened for their ability to repress transcription in the presence of AHL. Following sequencing, site-directed mutagenesis was used to generate all possible mutations of interest as single, rather than multiple amino acid substitutions. Eight individual amino acids playing a critical role in the AHL-insensitive phenotype have been identified. The ability of EsaR* variants to bind AHL and the effect of individual substitutions on the overall conformation of the protein were examined through in vitro assays. Six EsaR* variants had a decreased ability to bind AHL. Fluorescence anisotropy was used to examine the relative DNA binding affinity of the final two EsaR* variants, which retained some AHL binding capability but remained unresponsive to it, perhaps due to an inability of the N-terminal domain to transduce information to the C-terminal domain.

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

    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. PMID:17827290

  6. Acyl-homoserine lactone-based quorum sensing and quorum quenching hold promise to determine the performance of biological wastewater treatments: An overview.

    Huang, Jinhui; Shi, Yahui; Zeng, Guangming; Gu, Yanling; Chen, Guiqiu; Shi, Lixiu; Hu, Yi; Tang, Bi; Zhou, Jianxin

    2016-08-01

    Quorum sensing (QS) is a communication process between cells, in which bacteria secrete and sense the specific chemicals, and regulate gene expression in response to population density. Quorum quenching (QQ) blocks QS system, and inhibits gene expression mediating bacterial behaviors. Given the extensive research of acyl-homoserine lactone (AHL) signals, existences and effects of AHL-based QS and QQ in biological wastewater treatments are being subject to high concern. This review summarizes AHL structure, synthesis mode, degradation mechanisms, analytical methods, environmental factors, AHL-based QS and QQ mechanisms. The existences and roles of AHL-based QS and QQ in biomembrane processes, activated sludge processes and membrane bioreactors are summarized and discussed, and corresponding exogenous regulation strategy by selective enhancement of AHL-based QS or QQ coexisting in biological wastewater treatments is suggested. Such strategies including the addition of AHL signals, AHL-producing bacteria as well as quorum quenching enzyme or bacteria can effectively improve wastewater treatment performance without killing or limiting bacterial survival and growth. This review will present the theoretical and practical cognition for bacterial AHL-based QS and QQ, suggest the feasibility of exogenous regulation strategies in biological wastewater treatments, and provide useful information to scientists and engineers who work in this field. PMID:27213243

  7. Interference of Quorum Sensing by Delftia sp. VM4 Depends on the Activity of a Novel N-Acylhomoserine Lactone-Acylase

    Vimal B Maisuria; Nerurkar, Anuradha S.

    2015-01-01

    Background Turf soil bacterial isolate Delftia sp. VM4 can degrade exogenous N-acyl homoserine lactone (AHL), hence it effectively attenuates the virulence of bacterial soft rot pathogen Pectobacterium carotovorum subsp. carotovorum strain BR1 (Pcc BR1) as a consequence of quorum sensing inhibition. Methodology/Principal Findings Isolated Delftia sp. VM4 can grow in minimal medium supplemented with AHL as a sole source of carbon and energy. It also possesses the ability to degrade various AHL...

  8. Interference of Quorum Sensing by Delftia sp. VM4 Depends on the Activity of a Novel N-Acylhomoserine Lactone-Acylase.

    Vimal B Maisuria

    Full Text Available Turf soil bacterial isolate Delftia sp. VM4 can degrade exogenous N-acyl homoserine lactone (AHL, hence it effectively attenuates the virulence of bacterial soft rot pathogen Pectobacterium carotovorum subsp. carotovorum strain BR1 (Pcc BR1 as a consequence of quorum sensing inhibition.Isolated Delftia sp. VM4 can grow in minimal medium supplemented with AHL as a sole source of carbon and energy. It also possesses the ability to degrade various AHL molecules in a short time interval. Delftia sp. VM4 suppresses AHL accumulation and the production of virulence determinant enzymes by Pcc BR1 without interference of the growth during co-culture cultivation. The quorum quenching activity was lost after the treatment with trypsin and proteinase K. The protein with quorum quenching activity was purified by three step process. Matrix assisted laser desorption/ionization-time of flight (MALDI-TOF and Mass spectrometry (MS/MS analysis revealed that the AHL degrading enzyme (82 kDa demonstrates homology with the NCBI database hypothetical protein (Daci_4366 of D. acidovorans SPH-1. The purified AHL acylase of Delftia sp. VM4 demonstrated optimum activity at 20-40°C and pH 6.2 as well as AHL acylase type mode of action. It possesses similarity with an α/β-hydrolase fold protein, which makes it unique among the known AHL acylases with domains of the N-terminal nucleophile (Ntn-hydrolase superfamily. In addition, the kinetic and thermodynamic parameters for hydrolysis of the different AHL substrates by purified AHL-acylase were estimated. Here we present the studies that investigate the mode of action and kinetics of AHL-degradation by purified AHL acylase from Delftia sp. VM4.We characterized an AHL-inactivating enzyme from Delftia sp. VM4, identified as AHL acylase showing distinctive similarity with α/β-hydrolase fold protein, described its biochemical and thermodynamic properties for the first time and revealed its potential application as an anti

  9. Characterization of N-acylhomoserine lactone-degrading bacteria associated with the Zingiber officinale (ginger rhizosphere: Co-existence of quorum quenching and quorum sensing in Acinetobacter and Burkholderia

    Chhabra Siri

    2011-03-01

    Full Text Available Abstract Background Cell-to-cell communication (quorum sensing (QS co-ordinates bacterial behaviour at a population level. Consequently the behaviour of a natural multi-species community is likely to depend at least in part on co-existing QS and quorum quenching (QQ activities. Here we sought to discover novel N-acylhomoserine lactone (AHL-dependent QS and QQ strains by investigating a bacterial community associated with the rhizosphere of ginger (Zingiber officinale growing in the Malaysian rainforest. Results By using a basal growth medium containing N-(3-oxohexanoylhomoserine lactone (3-oxo-C6-HSL as the sole source of carbon and nitrogen, the ginger rhizosphere associated bacteria were enriched for strains with AHL-degrading capabilities. Three isolates belonging to the genera Acinetobacter (GG2, Burkholderia (GG4 and Klebsiella (Se14 were identified and selected for further study. Strains GG2 and Se14 exhibited the broadest spectrum of AHL-degrading activities via lactonolysis while GG4 reduced 3-oxo-AHLs to the corresponding 3-hydroxy compounds. In GG2 and GG4, QQ was found to co-exist with AHL-dependent QS and GG2 was shown to inactivate both self-generated and exogenously supplied AHLs. GG2, GG4 and Se14 were each able to attenuate virulence factor production in both human and plant pathogens. Conclusions Collectively our data show that ginger rhizosphere bacteria which make and degrade a wide range of AHLs are likely to play a collective role in determining the QS-dependent phenotype of a polymicrobial community.

  10. N-acylhomoserine-lactone-mediated communication between Pseudomonas aeruginosa and Burkholderia cepacia in mixed biofilms

    Riedel, K.; Hentzer, Morten; Geisenberger, O.;

    2001-01-01

    Pseudomonas aeruginosa and Burkholderia cepacia are capable of forming mixed biofilms in the lungs of cystic fibrosis patients. Both bacteria employ quorum-sensing systems, which rely on N-acylhomoserine lactone (AHL) signal molecules, to co- ordinate expression of virulence factors with the...

  11. N-acylhomoserine-lactone-mediated communication between Pseudomonas aeruginosa and Burkholderia cepacia in mixed biofilms

    Riedel, K; Hentzer, Morten; Geisenberger, O;

    2001-01-01

    Pseudomonas aeruginosa and Burkholderia cepacia are capable of forming mixed biofilms in the lungs of cystic fibrosis patients. Both bacteria employ quorum-sensing systems, which rely on N-acylhomoserine lactone (AHL) signal molecules, to co-ordinate expression of virulence factors with the forma...

  12. N-acylhomoserine-lactone-mediated communication between Pseudomonas aeruginosa and Burkholderia cepacia in mixed biofilms

    Riedel, K.; Hentzer, Morten; Geisenberger, O.;

    2001-01-01

    Pseudomonas aeruginosa and Burkholderia cepacia are capable of forming mixed biofilms in the lungs of cystic fibrosis patients. Both bacteria employ quorum-sensing systems, which rely on N-acylhomoserine lactone (AHL) signal molecules, to co- ordinate expression of virulence factors with the form...

  13. Acyl homoserine lactone-based quorum sensing in a methanogenic archaeon

    Zhang, Guishan; Zhang, Fan; Ding, Gang; Li, Jie; Guo, Xiaopeng; Zhu, Jinxing; Zhou, Liguang; Cai, Shichun; Liu, Xiaoli; Luo, Yuanming; Zhang, Guifeng; Shi, Wenyuan; Dong, Xiuzhu

    2012-01-01

    Acyl homoserine lactone (AHL)-based quorum sensing commonly refers to cell density-dependent regulatory mechanisms found in bacteria. However, beyond bacteria, this cell-to-cell communication mechanism is poorly understood. Here we show that a methanogenic archaeon, Methanosaeta harundinacea 6Ac, encodes an active quorum sensing system that is used to regulate cell assembly and carbon metabolic flux. The methanogen 6Ac showed a cell density-dependent physiology transition, which was related t...

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

    Olsen, Jacob Alsbæk; Severinsen, Rune Eg; Rasmussen, Thomas Bovbjerg; Hentzer, Morten; Givskov, Michael Christian; Nielsen, John

    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 whi...... 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....

  15. Absolute configuration and antimicrobial activity of acylhomoserine lactones.

    Pomini, Armando M; Marsaioli, Anita J

    2008-06-01

    (S)-N-Heptanoylhomoserine lactone is an uncommon acyl odd-chain natural product employed by many Gram-negative bacteria as a signaling substance in chemical communication mechanisms known as quorum sensing. The absolute configuration determination of the metabolite produced by the phytopathogen Pantoea ananatis Serrano is reported herein. As with all other substances of this class, the lactone moiety possesses S configuration, corroborating the hypothesis that it shares the same biosynthetic pathway as the (S)-N-hexanoylhomoserine lactone and also that some LuxI homologues can accept both hexanoyl- and heptanoyl-ACP as precursors. Evaluation of the antimicrobial activity of enantiomeric acylhomoserine lactones against three Gram-positive bacteria (Bacillus cereus, B. subtilis, and Staphylococcus aureus) revealed important features between absolute configuration and antimicrobial activity. The N-heptanoylhomoserine lactone was considerably less active than the 3-oxo derivatives. Surprisingly, non-natural (R)-N-(3-oxo-octanoyl)homoserine lactone was as active as the S enantiomer against B. cereus, while the synthetic racemic product was less active than either enantiomer. PMID:18465897

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

    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 ⩾2.4mgml(-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 0.071mgml(-1) of blumeoidolide B in comparison with ⩾3.6mgml(-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 in

  17. 产生物胺菌株群体感应AHLs检测及分析%Detection and analysis of quorum sensing about N-acylhomoserine lactones of biogenic amine strains

    陆静; 卢士玲; 刘玉晗; 尹罗罗; 李想鹏; 潘竞勇; 高雄颖

    2014-01-01

    为探讨发酵肉制品中生物胺的产生、累积机理,采用高效液相法分析了新疆熏马肠样品产生物胺优势菌株克雷伯氏菌(Klebsiella sp.)、阴沟肠杆菌(Enterobacter cloacae strain)和成团泛菌(Pantoea agglomerans strain)产生物胺能力.并选取克雷伯氏菌、阴沟肠杆菌、成团泛菌作为群体感应现象研究对象,利用微生物传感菌Agrobacterium tumefaciens A136及Agrobacterium tumefaciens KYC55平行线法检测AHLs.检测表明,3株产生物胺菌能够发生群体感应现象.通过β-半乳糖苷酶活性检测法测定AHLs活性试验、HPLC法对产生物胺菌株AHLs定性分析,结果表明,β-半乳糖苷酶活性越高,产生物胺菌株分泌的AHLs越多;Klebsiella sp.、Enterobacter cloacae strain均能分泌:N-butanoyl-L-homoserine lactone (C4-HSL)、N-hexanoyl-DL-homoserine homoserine lactone(C6-HSL)、N-octanoyl-DL-homoserine lactone(C8-HSL)类型的信号分子.

  18. Rapid Acyl-Homoserine Lactone Quorum Signal Biodegradation in Diverse Soils

    Ya-juan WANG; Leadbetter, Jared Renton

    2005-01-01

    Signal degradation impacts all communications. Although acyl-homoserine lactone (acyl-HSL) quorum-sensing signals are known to be degraded by defined laboratory cultures, little is known about their stability in nature. Here, we show that acyl-HSLs are biodegraded in soils sampled from diverse U.S. sites and by termite hindgut contents. When amended to samples at physiologically relevant concentrations, 14C-labeled acyl-HSLs were mineralized to 14CO2 rapidly and, at most sites examined, witho...

  19. Rosmarinic acid is a homoserine lactone mimic produced by plants that activates a bacterial quorum-sensing regulator.

    Corral-Lugo, Andrés; Daddaoua, Abdelali; Ortega, Alvaro; Espinosa-Urgel, Manuel; Krell, Tino

    2016-01-01

    Quorum sensing is a bacterial communication mechanism that controls genes, enabling bacteria to live as communities, such as biofilms. Homoserine lactone (HSL) molecules function as quorum-sensing signals for Gram-negative bacteria. Plants also produce previously unidentified compounds that affect quorum sensing. We identified rosmarinic acid as a plant-derived compound that functioned as an HSL mimic. In vitro assays showed that rosmarinic acid bound to the quorum-sensing regulator RhlR of Pseudomonas aeruginosa PAO1 and competed with the bacterial ligand N-butanoyl-homoserine lactone (C4-HSL). Furthermore, rosmarinic acid stimulated a greater increase in RhlR-mediated transcription in vitro than that of C4-HSL. In P. aeruginosa, rosmarinic acid induced quorum sensing-dependent gene expression and increased biofilm formation and the production of the virulence factors pyocyanin and elastase. Because P. aeruginosa PAO1 infection induces rosmarinic acid secretion from plant roots, our results indicate that rosmarinic acid secretion is a plant defense mechanism to stimulate a premature quorum-sensing response. P. aeruginosa is a ubiquitous pathogen that infects plants and animals; therefore, identification of rosmarinic acid as an inducer of premature quorum-sensing responses may be useful in agriculture and inform human therapeutic strategies. PMID:26732761

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

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

    2007-01-01

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

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

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

    2007-01-01

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

  2. Synthesis and biological evaluation of novel N-α-haloacylated homoserine lactones as quorum sensing modulators

    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.

  3. Global and Phylogenetic Distribution of Quorum Sensing Signals, Acyl Homoserine Lactones, in the Family of Vibrionaceae

    Rasmussen, Bastian Barker; Nielsen, Kristian Fog; Machado, Henrique;

    2014-01-01

    Bacterial quorum sensing (QS) and the corresponding signals, acyl homoserine lactones (AHLs), were first described for a luminescent Vibrio species. Since then, detailed knowledge has been gained on the functional level of QS; however, the abundance of AHLs in the family of Vibrionaceae in the...... homology, however not with geographical location. In conclusion, a wide range of AHL signals are produced by a number of clades in the Vibrionaceae family and these results will allow future investigations of inter- and intra-species interactions within this cosmopolitan family of marine bacteria....

  4. Quorum sensing control of Type VI secretion factors restricts the proliferation of quorum-sensing mutants.

    Majerczyk, Charlotte; Schneider, Emily; Greenberg, E Peter

    2016-01-01

    Burkholderia thailandensis uses acyl-homoserine lactone-mediated quorum sensing systems to regulate hundreds of genes. Here we show that cell-cell contact-dependent type VI secretion (T6S) toxin-immunity systems are among those activated by quorum sensing in B. thailandensis. We also demonstrate that T6S is required to constrain proliferation of quorum sensing mutants in colony cocultures of a BtaR1 quorum-sensing signal receptor mutant and its parent. However, the BtaR1 mutant is not constrained by and outcompetes its parent in broth coculture, presumably because no cell contact occurs and there is a metabolic cost associated with quorum sensing gene activation. The increased fitness of the wild type over the BtaR1 mutant during agar surface growth is dependent on an intact T6SS-1 apparatus. Thus, quorum sensing activates B. thailandensis T6SS-1 growth inhibition and this control serves to police and constrain quorum-sensing mutants. This work defines a novel role for T6SSs in intraspecies mutant control. PMID:27183270

  5. Quorum sensing control of Type VI secretion factors restricts the proliferation of quorum-sensing mutants

    Majerczyk, Charlotte; Schneider, Emily; Greenberg, E Peter

    2016-01-01

    Burkholderia thailandensis uses acyl-homoserine lactone-mediated quorum sensing systems to regulate hundreds of genes. Here we show that cell-cell contact-dependent type VI secretion (T6S) toxin-immunity systems are among those activated by quorum sensing in B. thailandensis. We also demonstrate that T6S is required to constrain proliferation of quorum sensing mutants in colony cocultures of a BtaR1 quorum-sensing signal receptor mutant and its parent. However, the BtaR1 mutant is not constrained by and outcompetes its parent in broth coculture, presumably because no cell contact occurs and there is a metabolic cost associated with quorum sensing gene activation. The increased fitness of the wild type over the BtaR1 mutant during agar surface growth is dependent on an intact T6SS-1 apparatus. Thus, quorum sensing activates B. thailandensis T6SS-1 growth inhibition and this control serves to police and constrain quorum-sensing mutants. This work defines a novel role for T6SSs in intraspecies mutant control. DOI: http://dx.doi.org/10.7554/eLife.14712.001 PMID:27183270

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

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

    2005-01-01

    Parallel solution-phase synthesis of sulfide AHL analogues (10a s) by one-pot or a sequential approach is reported. The corresponding sulfoxides 13a-e and sulfones 14a-e were prepared to expand the diversity of the 19-member array of sulfides 10a-s. Likewise, dithianes 12a-c were prepared...... 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...

  7. Unusual Multiple Production of N-Acylhomoserine Lactones a by Burkholderia sp. Strain C10B Isolated from Dentine Caries

    Share Yuan Goh

    2014-05-01

    Full Text Available Bacteria realize the ability to communicate by production of quorum sensing (QS molecules called autoinducers, which regulate the physiological activities in their ecological niches. The oral cavity could be a potential area for the presence of QS bacteria. In this study, we report the isolation of a QS bacterial isolate C10B from dentine caries. Preliminary screening using Chromobacterium violaceum CV026 biosensor showed that isolate C10B was able to produce N-acylhomoserine lactones (AHLs. This bacterium was further identified as a member of Burkholderia, an opportunistic pathogen. The isolated Burkholderia sp. was confirmed to produce N-hexanoyl-L-homoserine lactone (C6-HSL, N-octanoyl-L-homoserine lactone (C8-HSL, N-decanoyl-L-homoserine lactone (C10-HSL and N-dodecanoyl-L-homoserine lactone (C12-HSL.

  8. Inhibition of Lux quorum-sensing system by synthetic N-acyl-L-homoserine lactone analogous

    2008-01-01

    In the present study, we investigated the inhibition of the Lux quorum-sensing system by N-acyi cyclopentylamine (Cn-CPA). The Lux quorum-sensing system regulates luminescence gene expression in Vibriofischeri. We have already reported on the synthesis of Cn-CPA and their abilities as inhibitors of the quorum-sensing systems in Pseudomonas aeruginosa and Serratia marcescens. In the case of Pseudomonas aeruginosa (Las and Rhl quorum-sensing system) and Serratia marcescens (Spn quorum-sensing system), specific Cn-CPA with a particular acyi chain length showed the strongest inhibitory effect. In the case of the Lux quorum-sensing system, it was found that several kinds of Cn-CPA with a range from C5 to C10 showed similar strong inhibitory effects. Moreover, the inhibitory effect of Cn-CPA on the Lux quorum-sensing system was stronger than that of halogenated furanone, a natural quorum-sensing inhibitor.

  9. Characterization of N-Acylhomoserine Lactones Produced by Bacteria Isolated from Industrial Cooling Water Systems

    Noriya Okutsu

    2015-12-01

    Full Text Available The cooling water systems are used to remove heat generated in the various industries. Biofouling of the cooling water systems causes blocking of condenser pipes and the heat exchanger tubes. In many Gram-negative bacteria, N-acylhomoserine lactone (AHL are used as quorum-sensing signal molecule and associated with biofilm formation. To investigate the relationship between quorum sensing and biofouling in the cooling water system, we isolated a total of 192 bacterial strains from the five cooling water systems, and screened for AHL production. Seven isolates stimulated AHL-mediated purple pigment production in AHL reporter strain Chromobacterium violaceum CV026 or VIR07. Based on their 16S rRNA gene sequences, AHL-producing isolates were assigned to Aeromonas hydrophila, Lysobacter sp., Methylobacterium oryzae, and Bosea massiliensis. To the best of our knowledge, B. massiliensis and Lysobacter sp. have not been reported as AHL-producing species in the previous researches. AHLs extracted from the culture supernatants of B. massiliensis and Lysobacter sp. were identified by liquid chromatography-mass spectrometry. AHLs produced by B. massiliensis were assigned as N-hexanoyl-l-homoserine lactone (C6-HSL, N-(3-oxohexanoyl-l-homoserine lactone (3-oxo-C6-HSL, and N-(3-oxooctanoyl-l-homoserine lactone (3-oxo-C8-HSL. AHLs produced by Lysobacter sp. were assigned as N-decanoyl-l-homoserine lactone (C10-HSL and N-(3-oxodecanoyl-l-homoserine lactone (3-oxo-C10-HSL. This is the first report of identification of AHLs produced by B. massiliensis and Lysobacter sp. isolated from the cooling water system.

  10. Characterization of N-Acylhomoserine Lactones Produced by Bacteria Isolated from Industrial Cooling Water Systems.

    Okutsu, Noriya; Morohoshi, Tomohiro; Xie, Xiaonan; Kato, Norihiro; Ikeda, Tsukasa

    2015-01-01

    The cooling water systems are used to remove heat generated in the various industries. Biofouling of the cooling water systems causes blocking of condenser pipes and the heat exchanger tubes. In many Gram-negative bacteria, N-acylhomoserine lactone (AHL) are used as quorum-sensing signal molecule and associated with biofilm formation. To investigate the relationship between quorum sensing and biofouling in the cooling water system, we isolated a total of 192 bacterial strains from the five cooling water systems, and screened for AHL production. Seven isolates stimulated AHL-mediated purple pigment production in AHL reporter strain Chromobacterium violaceum CV026 or VIR07. Based on their 16S rRNA gene sequences, AHL-producing isolates were assigned to Aeromonas hydrophila, Lysobacter sp., Methylobacterium oryzae, and Bosea massiliensis. To the best of our knowledge, B. massiliensis and Lysobacter sp. have not been reported as AHL-producing species in the previous researches. AHLs extracted from the culture supernatants of B. massiliensis and Lysobacter sp. were identified by liquid chromatography-mass spectrometry. AHLs produced by B. massiliensis were assigned as N-hexanoyl-L-homoserine lactone (C6-HSL), N-(3-oxohexanoyl)-L-homoserine lactone (3-oxo-C6-HSL), and N-(3-oxooctanoyl)-L-homoserine lactone (3-oxo-C8-HSL). AHLs produced by Lysobacter sp. were assigned as N-decanoyl-L-homoserine lactone (C10-HSL) and N-(3-oxodecanoyl)-L-homoserine lactone (3-oxo-C10-HSL). This is the first report of identification of AHLs produced by B. massiliensis and Lysobacter sp. isolated from the cooling water system. PMID:26729121

  11. Detection of N-acylhomoserine lactones in lung tissues of mice infected with Pseudomonas aeruginosa

    Wu, H; Song, Z; Hentzer, Morten;

    2000-01-01

    The pathogenesis of Pseudomonas aeruginosa is associated with expression of virulence factors, many of which are controlled by two N:-acylhomoserine lactone (AHL)-based quorum-sensing systems. Escherichia coli strains equipped with a luxR-based monitor system expressing green fluorescent protein...... (GFP) in the presence of exogenous AHL molecules were used to detect the production of AHLs from P. aeruginosa in vivo. Mice were challenged intratracheally with alginate beads containing P. aeruginosa and E. coli and killed on different days after the challenge. By means of confocal scanning laser...... microscopy, GFP-expressing E. coli bacteria could be detected in the lung tissues, indicating production and excretion of AHL molecules in vivo by the infecting P. aeruginosa. AHL signals were detected mainly in lung tissues exhibiting severe pathological changes. These findings support the view that...

  12. Acyl-homoserine lactones from Erwinia psidii R. IBSBF 435T, a guava phytopathogen (Psidium guajava L.).

    Pomini, Armando M; Manfio, Gilson P; Araújo, Welington L; Marsaioli, Anita J

    2005-08-10

    The phytopathogen Erwinia psidii R. IBSBF 435T causes rot in branches, flowers, and fruits of guava (Psidium guajava L.), being responsible for crop losses, and has no effective control. It was demonstrated that this strain produces two compounds [S-(-)-N-hexanoyl and N-heptanoyl-homoserine lactone], both belonging to the class of quorum-sensing signaling substances. A protocol using gas chromatography-flame ionization detection with chiral stationary phase is described for the absolute configuration determination of a natural acyl-homoserine lactone. Biological assays with specific reporter and synthesis of identified substances are also described. This is the first report on the N-heptanoyl-homoserine lactone occurrence in the Erwinia genus. PMID:16076103

  13. Changes in the Salmonella enterica Enteritidis phenotypes in presence of acyl homoserine lactone quorum sensing signals.

    Campos-Galvão, Maria Emilene Martino; Ribon, Andrea Oliveira Barros; Araújo, Elza Fernandes; Vanetti, Maria Cristina Dantas

    2016-05-01

    Quorum sensing is used by bacteria to coordinate gene expression in response to population density and involves the production, detection and response to extracellular signaling molecules known as autoinducers (AIs). Salmonella does not synthesize the AI-1, acyl homoserine lactone (AHL) common to gram-negative bacteria; however, it has a receptor for AI-1, the SdiA protein. The effect of SdiA in modulating phenotypes of Salmonella has not been elucidated. In this report, we provide evidence that the AIs-1 affect Salmonella enterica serovar Enteritidis behavior by enhancing the biofilm formation and expression of virulence genes under anaerobic conditions. Biofilm formation by Salmonella was detected by the crystal violet method and by scanning electron microscopy. The presence of AHLs, particularly C12-HSL, increased biofilm formation and promoted expression of biofilm formation genes (lpfA, fimF, fliF, glgC) and virulence genes (hilA, invA, invF). Our results demonstrated that AHLs produced by other organisms played an important role in virulence phenotypes of Salmonella Enteritidis. PMID:26662614

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

    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 id...

  15. The Pseudomonas putida Lon protease is involved in N-acyl homoserine lactone quorum sensing regulation

    Leoni Livia

    2007-07-01

    Full Text Available Abstract Background In Pseudomonas putida and Pseduomonas aeruginosa, the similar PpuR/RsaL/PpuI and LasR/RsaL/LasI acyl homoserine lactones (AHLs quorum sensing (QS systems have been shown to be under considerable regulation by other global regulators. A major regulator is the RsaL protein which strongly directly represses the transcription of the P. putida ppuI and P. aeruginosa lasI AHL synthases. In this study we screened a transposon mutant bank of P. putida in order to identify if any other regulators were involved in negative regulation of AHL QS. Results In our screen we identified three Tn5 mutants which displayed overproduction of AHLs in P. putida strain WCS358. Two of the mutants had a Tn5 located in the rsaL gene, whereas in one mutant the transposon was located in the lon protease gene. Lon proteases play important roles in protein quality control via degradation of misfolded proteins. It was determined that in the P. putida lon mutant, AHL levels, PpuR levels and ppuI promoter activity all increased significantly; we therefore postulated that PpuR is a target for Lon. The Lon protease had no effect on AHL production in P. aeruginosa. Conclusion The Lon protease is a negative regulator of AHL production in P. putida WCS358. The Lon protease has also been shown by others to influence AHL QS in Vibrio fischeri and Agrobacterium tumefaciens and can thus become an important regulator of AHL QS timing and regulation in bacteria.

  16. Acyl-homoserine Lactone from Saccharum × officinarum with Stereochemistry-Dependent Growth Regulatory Activity.

    Olher, Vanessa G A; Ferreira, Nagela P; Souza, Alan G; Chiavelli, Lucas U R; Teixeira, Aline F; Santos, Wanderley D; Santin, Silvana M O; Ferrarese Filho, Osvaldo; Silva, Cleuza C; Pomini, Armando M

    2016-05-27

    Acyl-homoserine lactones (AHLs) are a class of compounds produced by Gram-negative bacteria that are used in a process of chemical communication called quorum sensing. Much is known about how bacteria use these chemical compounds to control the expression of important factors; however, there have been few reports about the presence and effects of AHLs in plants. In this study, the phytochemical study of leaves and culms of sugar cane (Saccharum × officinarum) led to the identification of N-(3-oxo-octanoyl)homoserine lactone. Since the absolute configuration of the natural product could not be determined, both R and S enantiomers of N-(3-oxo-octanoyl)homoserine lactone were synthesized and tested in sugar cane culms. The enantiomers caused changes in the mass and length of buds and roots when used at micromolar concentrations. Using the sugar cane RB96-6928 variety, the S enantiomer increased sprouting of roots more effectively than the R enantiomer. Furthermore, scanning electron microscopy showed that both the R and S enantiomers led to more stretched root cells compared with the control. PMID:27192014

  17. Probing the Impact of Ligand Binding on the Acyl-Homoserine Lactone-Hindered Transcription Factor EsaR of Pantoea stewartii subsp. stewartii ▿

    Daniel J Schu; Ramachandran, Revathy; Jared S Geissinger; Stevens, Ann M.

    2011-01-01

    The quorum-sensing regulator EsaR from Pantoea stewartii subsp. stewartii is a LuxR homologue that is inactivated by acyl-homoserine lactone (AHL). In the corn pathogen P. stewartii, production of exopolysaccharide (EPS) is repressed by EsaR at low cell densities. However, at high cell densities when high concentrations of its cognate AHL signal are present, EsaR is inactivated and derepression of EPS production occurs. Thus, EsaR responds to AHL in a manner opposite to that of most LuxR fami...

  18. Stereochemical insignificance discovered in Acinetobacter baumannii quorum sensing.

    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.

  19. Rhodococcus erythropolis and Its γ-Lactone Catabolic Pathway: An Unusual Biocontrol System That Disrupts Pathogen Quorum Sensing Communication

    Xavier Latour

    2013-12-01

    Full Text Available Rhodococcus erythropolis is an environmental Gram-positive Actinobacterium with a versatile metabolism involved in various bioconversions and degradations. Rhodococci are best known for their great potential in numerous decontamination and industrial processes. However, they can also prevent plant disease by disrupting quorum sensing-based communication of Gram-negative soft-rot bacteria, by degrading N-acyl-homoserine lactone signaling molecules. Such biocontrol activity results partly from the action of the γ-lactone catabolic pathway. This pathway is responsible for cleaving the lactone bond of a wide range of compounds comprising a γ-butyrolactone ring coupled to an alkyl or acyl chain. The aliphatic products of this hydrolysis are then activated and enter fatty acid metabolism. This short pathway is controlled by the presence of the γ-lactone, presumably sensed by a TetR-like transcriptional regulator, rather than the presence of the pathogen or the plant-host in the environment of the Rhodococci. Both the density and biocontrol activity of R. erythropolis may be boosted in crop systems. Treatment with a cheap γ-lactone stimulator, for example, the food flavoring γ-caprolactone, induces the activity in the biocontrol agent, R. erythropolis, of the pathway degrading signaling molecules; such treatments thus promote plant protection.

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

    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.

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

    Maurilio L. Martins

    2014-09-01

    Full Text Available 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.

  2. Triazole-containing N-acyl homoserine lactones targeting the quorum sensing system in Pseudomonas aeruginosa

    Hansen, Mette Reimert; Jakobsen, Tim H.; Bang, Claus Gunnar;

    2015-01-01

    pathogenesis and antibiotic tolerance of a bacterial biofilm. To identify the structural elements important for antagonistic or agonistic activity against the Pseudomonas aeruginosa LasR protein, we report the synthesis and screening of new triazole-containing mimics of natural N-acyl homoserine lactones. A...... series of azide- and alkyne-containing homoserine lactone building blocks was used to prepare an expanded set of 123 homoserine lactone analogues through a combination of solution- and solid-phase synthesis methods. The resulting compounds were subjected to cell-based quorum sensing screening assays...

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

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

    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 m...

  4. Quorum sensing signal molecules (acylated homoserine lactones) in Gram-negative fish pathogenic bacteria

    Bruhn, Jesper Bartholin; Dalsgaard, Inger; Nielsen, K.F.; Buchholtz, C.; Larsen, J.L.; Gram, Lone

    2005-01-01

    samples were further characterized by high performance liquid chromatography-high resolution mass spectrometry (HPLC-HR-MS). AHLs were produced by all strains of Aeromonas salmonicida, Aeromonas hydrophila, Yersinia ruckeri, Vibrio salmonicida, and Vibrio vulnificus. Some strains of atypical Aeromonas...... salmonicida and Vibrio splendidus were also positive. Aeromonas species produced N-butanoyl homoserine lactone (BHL) and N-hexanoyl homoserine lactone (HHL) and 1 additional product, whereas N-3-oxo-hexanoyl homoserine lactone (OHHL) and HHL were detected in Vibrio salmonicida. N-3-oxo-octanoyl homoserine...

  5. Quorum Sensing Controls Swarming Motility of Burkholderia glumae through Regulation of Rhamnolipids.

    Arvin Nickzad

    Full Text Available Burkholderia glumae is a plant pathogenic bacterium that uses an acyl-homoserine lactone-mediated quorum sensing system to regulate protein secretion, oxalate production and major virulence determinants such as toxoflavin and flagella. B. glumae also releases surface-active rhamnolipids. In Pseudomonas aeruginosa and Burkholderia thailandensis, rhamnolipids, along with flagella, are required for the social behavior called swarming motility. In the present study, we demonstrate that quorum sensing positively regulates the production of rhamnolipids in B. glumae and that rhamnolipids are necessary for swarming motility also in this species. We show that a rhlA- mutant, which is unable to produce rhamnolipids, loses its ability to swarm, and that this can be complemented by providing exogenous rhamnolipids. Impaired rhamnolipid production in a quorum sensing-deficient B. glumae mutant is the main factor responsible for its defective swarming motility behaviour.

  6. Quorum Sensing Controls Swarming Motility of Burkholderia glumae through Regulation of Rhamnolipids.

    Nickzad, Arvin; Lépine, François; Déziel, Eric

    2015-01-01

    Burkholderia glumae is a plant pathogenic bacterium that uses an acyl-homoserine lactone-mediated quorum sensing system to regulate protein secretion, oxalate production and major virulence determinants such as toxoflavin and flagella. B. glumae also releases surface-active rhamnolipids. In Pseudomonas aeruginosa and Burkholderia thailandensis, rhamnolipids, along with flagella, are required for the social behavior called swarming motility. In the present study, we demonstrate that quorum sensing positively regulates the production of rhamnolipids in B. glumae and that rhamnolipids are necessary for swarming motility also in this species. We show that a rhlA- mutant, which is unable to produce rhamnolipids, loses its ability to swarm, and that this can be complemented by providing exogenous rhamnolipids. Impaired rhamnolipid production in a quorum sensing-deficient B. glumae mutant is the main factor responsible for its defective swarming motility behaviour. PMID:26047513

  7. Rapid acyl-homoserine lactone quorum signal biodegradation in diverse soils.

    Wang, Ya-Juan; Leadbetter, Jared Renton

    2005-03-01

    Signal degradation impacts all communications. Although acyl-homoserine lactone (acyl-HSL) quorum-sensing signals are known to be degraded by defined laboratory cultures, little is known about their stability in nature. Here, we show that acyl-HSLs are biodegraded in soils sampled from diverse U.S. sites and by termite hindgut contents. When amended to samples at physiologically relevant concentrations, 14C-labeled acyl-HSLs were mineralized to 14CO2 rapidly and, at most sites examined, without lag. A lag-free turf soil activity was characterized in further detail. Heating or irradiation of the soil prior to the addition of radiolabel abolished mineralization, whereas protein synthesis inhibitors did not. Mineralization exhibited an apparent Km of 1.5 microM acyl-HSL, ca. 1,000-fold lower than that reported for a purified acyl-HSL lactonase. Under optimal conditions, acyl-HSL degradation proceeded at a rate of 13.4 nmol x h(-1) x g of fresh weight soil(-1). Bioassays established that the final extent of signal inactivation was greater than for its full conversion to CO2 but that the two processes were well coupled kinetically. A most probable number of 4.6 x 10(5) cells . g of turf soil(-1) degraded physiologically relevant amounts of hexanoyl-[1-14C]HSL to 14CO2. It would take chemical lactonolysis months to match the level of signal decay achieved in days by the observed biological activity. Rapid decay might serve either to quiet signal cross talk that might otherwise occur between spatially separated microbial aggregates or as a full system reset. Depending on the context, biological signal decay might either promote or complicate cellular communications and the accuracy of population density-based controls on gene expression in species-rich ecosystems. PMID:15746331

  8. Quorum Sensing Activity of Hafnia alvei Isolated from Packed Food

    Jia-Yi Tan

    2014-04-01

    Full Text Available Quorum sensing (QS is a mechanism adopted by bacteria to regulate expression of genes according to population density. N-acylhomoserine lactones (AHLs are a type of QS signalling molecules commonly found in Gram-negative bacteria which have been reported to play a role in microbial spoilage of foods and pathogenesis. In this study, we isolated an AHL-producing Hafnia alvei strain (FB1 from spherical fish pastes. Analysis via high resolution triple quadrupole liquid chromatography/mass spectrometry (LC/MS on extracts from the spent supernatant of H. alvei FB1 revealed the existence of two short chain AHLs: N-(3-oxohexanoyl homoserine lactone (3-oxo-C6-HSL and N-(3-oxo- octanoyl homoserine lactone (3-oxo-C8-HSL. To our knowledge, this is the first report of the production of AHLs, especially 3-oxo-C8-HSL, by H. alvei.

  9. Proteomic Analysis of the Quorum-Sensing Regulon in Pantoea stewartii and Identification of Direct Targets of EsaR

    Ramachandran, Revathy; Stevens, Ann M.

    2013-01-01

    The proteobacterium Pantoea stewartii subsp. stewartii causes Stewart's wilt disease in maize when it colonizes the xylem and secretes large amounts of stewartan, an exopolysaccharide. The success of disease pathogenesis lies in the timing of bacterial virulence factor expression through the different stages of infection. Regulation is achieved through a quorum-sensing (QS) system consisting of the acyl-homoserine lactone (AHL) synthase, EsaI, and the transcription regulator EsaR. At low cell...

  10. The Plant Pathogen Pantoea ananatis Produces N-Acylhomoserine Lactone and Causes Center Rot Disease of Onion by Quorum Sensing▿

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

    2007-01-01

    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-rec...

  11. The cep quorum-sensing system of Burkholderia cepacia H111 controls biofilm formation and swarming motility

    Huber, B.; Riedel, K.; Hentzer, Morten; Heydorn, Arne; Gotschlich, A.; Givskov, Michael Christian; Molin, Søren; Eberl, Leo

    2001-01-01

    rapidly colonize appropriate substrata. Evidence is provided that swarming motility of B. cepacia is quorum-sensing-regulated, possibly through the control of biosurfactant production. Complementation of the cepR mutant H111-R with different biosurfactants restored swarming motility while biofilm...... demonstrated that one of these mutants no longer produces N-acylhomoserine lactones (AHLs) due to an inactivation of the cepR gene. cepR and the cepI AHL synthase gene together constitute the cep quorum-sensing system of B. cepacia. By using a gene replacement method, two defined mutants, H111-I and H111-R......, were constructed in which cepI and cepR, respectively, had been inactivated. These mutants were used to demonstrate that biofilm formation by B. cepacia H111 requires a functional cep quorum-sensing system. A detailed quantitative analysis of the biofilm structures formed by wild-type and mutant...

  12. The BlcC (AttM) Lactonase of Agrobacterium tumefaciens Does Not Quench the Quorum-Sensing System That Regulates Ti Plasmid Conjugative Transfer ▿ †

    Khan, Sharik R.; Farrand, Stephen K.

    2008-01-01

    The conjugative transfer of Agrobacterium plasmids is controlled by a quorum-sensing system consisting of TraR and its acyl-homoserine lactone (HSL) ligand. The acyl-HSL is essential for the TraR-mediated activation of the Ti plasmid Tra genes. Strains A6 and C58 of Agrobacterium tumefaciens produce a lactonase, BlcC (AttM), that can degrade the quormone, leading some to conclude that the enzyme quenches the quorum-sensing system. We tested this hypothesis by examining the effects of the muta...

  13. GacS-dependent regulation of enzymic and antifungal activities and synthesis of N-acylhomoserine lactones in rhizospheric strain Pseudomonas chlororaphis 449.

    Veselova, M; Lipasova, V; Protsenko, M A; Buza, N; Khmel, I A

    2009-09-01

    Pseudomonas chlororaphis strain 449 isolated from the rhizosphere of maize suppresses numerous plant pathogens in vitro. The strain produces phenazine antibiotics and synthesizes at least three types of quorum sensing signaling molecules, N-acylhomoserine lactones. Here we have shown that the rhizospheric P. chlororaphis strains 449, well known strain 30-84 as well as two other P. chlororaphis strains exhibit polygalacturonase activity. Using mini-Tn5 transposon mutagenesis, four independent mutants of strain P. chlororaphis 449 with insertion of mini-Tn5 Km2 in gene gacS of two-component GacA-GacS system of global regulation were selected. All these mutant strains were deficient in production of extracellular proteinase(s), phenazines, N-acylhomoserine lactones synthesis, and did not inhibit the growth of G(+) bacteria in comparison with the wild type strain. The P. chlororaphis 449-06 gacS (-) mutant studied in greater detail was deficient in polygalacturonase, pectin methylesterase activities, swarming motility and antifungal activity. It is the first time the involvement of GacA-GacS system in the regulation of enzymes of pectin metabolism, polygalacturonase and pectin methylesterase, was demonstrated in fluorescent pseudomonads. PMID:19937212

  14. Production of N-acylhomoserine lactone signal molecules by gram-negative soil-borne and plant-associated bacteria.

    Veselova, M; Kholmeckaya, M; Klein, S; Voronina, E; Lipasova, V; Metlitskaya, A; Mayatskaya, A; Lobanok, E; Khmel, I; Chernin, L

    2003-01-01

    Quorum-sensing control mediated by N-acylhomoserine lactone (AHL) signal molecules has been established as a key feature in the regulation of various metabolic traits in many bacteria. Approximately 300 strains representing 6 genera and 18 species of soil-borne and plant-associated Gram-negative bacteria isolated in various regions of the former USSR using two reporter systems were screened for AHL production. The production was observed in 17.5% of the screened bacterial strains. Positive response was detected in all of the 14 tested strains of Erwinia herbicola, in 41 of the 239 strains of Pseudomonas species; in all 5 strains of Xanthomonas ampelina, X. campestris pv. malvacearum, pv. translucens, pv. vesicatoria and in one strain of Pantoea stewartii. AHL assay of 41 strains of X. maltophilia (syn. Stenotrophomonas maltophilia) isolated from soils with Chromobacterium violaceum reporter has revealed no strains synthesizing these signal molecules; 26 strains analyzed with Agrobacterium tumefaciens reporter showed the same result. PMID:15058194

  15. Response of Arabidopsis thaliana to N-hexanoyl-DL-homoserine-lactone, a bacterial quorum sensing molecule produced in the rhizosphere

    von Rad, U.; Klein, I.; Dobrev, Petre; Kottová, Jana; Zažímalová, Eva; Fekete, A.; Hartmann, A.; Schmitt-Kopplin, P.; Durner, J.

    2008-01-01

    Roč. 229, č. 1 (2008), s. 73-85. ISSN 0032-0935 R&D Projects: GA MŠk(CZ) LC06034 Institutional research plan: CEZ:AV0Z50380511 Keywords : Quorum sensing * Plant defense * Plant hormones * Rhizosphere Subject RIV: ED - Physiology Impact factor: 3.088, year: 2008

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

    Harshad Lade

    2014-01-01

    Full Text Available 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.

  17. Haemodynamic effects of the bacterial quorum sensing signal molecule, N-(3-oxododecanoyl)-L-homoserine lactone, in conscious, normal and endotoxaemic rats

    Gardiner, S. M.; Chhabra, S.R.; Harty, C; Williams, P; Pritchard, D I; Bycroft, B W; Bennett, T.

    2001-01-01

    N-acylhomoserine lactones (AHLs) are small, diffusible signalling molecules, employed by Gram-negative bacteria to coordinate gene expression with cell population density. Recent in vitro findings indicate that AHLs may function as virulence determinants per se, through modification of cytokine production by eukaryotic cells, and by stimulating the relaxation of blood vessels.In the present study, we assessed the influence of AHLs on cardiovascular function in conscious rats, and draw attenti...

  18. Classifying the Topology of AHL-Driven Quorum Sensing Circuits in Proteobacterial Genomes

    Sándor Pongor

    2012-04-01

    Full Text Available Virulence and adaptability of many Gram-negative bacterial species are associated with an N-acylhomoserine lactone (AHL gene regulation mechanism called quorum sensing (QS. The arrangement of quorum sensing genes is variable throughout bacterial genomes, although there are unifying themes that are common among the various topological arrangements. A bioinformatics survey of 1,403 complete bacterial genomes revealed characteristic gene topologies in 152 genomes that could be classified into 16 topological groups. We developed a concise notation for the patterns and show that the sequences of LuxR regulators and LuxI autoinducer synthase proteins cluster according to the topological patterns. The annotated topologies are deposited online with links to sequences and genome annotations at http://bacteria.itk.ppke.hu/QStopologies/.

  19. Transsexuality in the Rhizosphere: Quorum Sensing Reversibly Converts Agrobacterium tumefaciens from Phenotypically Female to Male▿

    Cho, Hongbaek; Pinto, Uelinton M.; Winans, Stephen C.

    2009-01-01

    Conjugative plasmids generally encode proteins that block the conjugative entry of identical or similar plasmids into the host cell, a phenomenon known as entry exclusion. Here, we demonstrate that two Ti plasmids of Agrobacterium tumefaciens encode robust entry exclusion functions. Two proteins, TrbJ and TrbK, can each mediate entry exclusion and act synergistically. The trbJ and trbK genes are included within the trb operon, which is tightly regulated by the quorum-sensing regulator TraR and the cognate acylhomoserine lactone. In the absence of quorum-sensing signals, these proteins are not significantly expressed, and cells lacking TrbJ and TrbK are efficient Ti plasmid recipients. In the presence of these signals, these strains block the entry of Ti plasmids and instead become efficient conjugal donors. PMID:19304847

  20. Transsexuality in the rhizosphere: quorum sensing reversibly converts Agrobacterium tumefaciens from phenotypically female to male.

    Cho, Hongbaek; Pinto, Uelinton M; Winans, Stephen C

    2009-05-01

    Conjugative plasmids generally encode proteins that block the conjugative entry of identical or similar plasmids into the host cell, a phenomenon known as entry exclusion. Here, we demonstrate that two Ti plasmids of Agrobacterium tumefaciens encode robust entry exclusion functions. Two proteins, TrbJ and TrbK, can each mediate entry exclusion and act synergistically. The trbJ and trbK genes are included within the trb operon, which is tightly regulated by the quorum-sensing regulator TraR and the cognate acylhomoserine lactone. In the absence of quorum-sensing signals, these proteins are not significantly expressed, and cells lacking TrbJ and TrbK are efficient Ti plasmid recipients. In the presence of these signals, these strains block the entry of Ti plasmids and instead become efficient conjugal donors. PMID:19304847

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

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

    2015-01-01

    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...... concentration of N-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...... on bacterial antiphage strategies and their regulation is essential for understanding the role of phages as drivers of bacterial evolution and diversity. In an applied context, development of successful phage-based control of bacterial pathogens also requires detailed understanding of the mechanisms...

  2. Bacteriocin small of Rhizobium leguminosarum belongs to the class of N-acyl-L-homoserine lactone molecules, known as autoinducers and as quorum sensing co-transcription factors.

    Schripsema, J; de Rudder, K E; van Vliet, T B; Lankhorst, P P; de Vroom, E; Kijne, J W; van Brussel, A A

    1996-01-01

    Small bacteriocin was isolated from the culture broth of the gram-negative bacterium Rhizobium leguminosarum, which forms symbiotic nitrogen-fixing root nodules on a number of leguminous plants. The structure of the molecule was elucidated by spectroscopic methods and identified as N-(3R-hydroxy-7-cis-tetradecanoyl)-L-homoserine lactone. The absolute configuration of both asymmetric carbon atoms in the molecule was determined by the use of the chiral solvating agents S-(+)- and R-(-)-2,2,2-trifluoro-1-(9-anthryl)-ethanol. small bacteriocin is structurally related to the quorum sensing co-transcription factors for genes from other bacteria such as Vibrio fischeri, Pseudomonas aeruginosa, Erwinia carotovora, and Agrobacterium tumefaciens which are involved in animal-microbe or plant-microbe interactions. The mechanism of regulation of such interactions by this kind of co-transcription factors is still unknown in R. leguminosarum. PMID:8550454

  3. Development of Methods for Structural Characterization of Pantoea stewartii Quorum-Sensing Regulator EsaR

    Pennerman, Kayla Kara

    2014-01-01

    The LuxR family of proteins serves as quorum-sensing transcriptional regulators in proteobacteria. At high population densities, a small acyl-homoserine lactone (AHL) molecule, produced by a LuxI homologue, accumulates in the environment. The LuxR proteins bind to their respective AHL when the ligand accumulates to sufficient levels. Once bound to AHL, the holoproteins usually become functional as transcriptional activators. However, there is a subset of LuxR homologues, the EsaR subfamily, w...

  4. Caffeine as a Potential Quorum Sensing Inhibitor

    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.

  5. Specificity of Acyl-Homoserine Lactone Synthases Examined by Mass Spectrometry

    Gould, Ty A.; Herman, Jake; Krank, Jessica; Robert C. Murphy; Mair E A Churchill

    2006-01-01

    Many gram-negative bacteria produce a specific set of N-acyl-l-homoserine-lactone (AHL) signaling molecules for the purpose of quorum sensing, which is a means of regulating coordinated gene expression in a cell-density-dependent manner. AHLs are produced from acylated acyl-carrier protein (acyl-ACP) and S-adenosyl-l-methionine by the AHL synthase enzyme. The appearance of specific AHLs is due in large part to the intrinsic specificity of the enzyme for subsets of acyl-ACP substrates. Structu...

  6. Profiling acylated homoserine lactones in Yersinia ruckeri and influence of exogenous acyl homoserine lactones and known quorum-sensing inhibitors on protease production

    Kastbjerg, Vicky Gaedt; Nielsen, Kristian Fog; Dalsgaard, Inger;

    2007-01-01

    To profile the quorum-sensing (QS) signals in Yersinia ruckeri and to examine the possible regulatory link between QS signals and a typical QS-regulated virulence phenotype, a protease. Methods and Results: Liquid chromatography-high resolution mass spectrometry (HPLC-HRMS) showed that Y. ruckeri...

  7. Acylhomoserine lactone production and degradation by the fish pathogen Tenacibaculum maritimum, a member of the Cytophaga-Flavobacterium-Bacteroides (CFB) group.

    Romero, Manuel; Avendaño-Herrera, Rubén; Magariños, Beatriz; Cámara, Miguel; Otero, Ana

    2010-03-01

    Tenacibaculum maritimum (formerly Flexibacter maritimus) is a filamentous, biofilm-forming member of the Cytophaga-Flavobacterium-Bacteroides group (or Bacteroidetes), which causes the widely distributed marine fish disease tenacibaculosis. A search for N-acylhomoserine lactones (AHLs) quorum-sensing (QS) signals in the culture media of nine representative strains of this species using different biosensor strains revealed the presence of short-type AHL activity in all of them. N-butyryl-L-homoserine lactone (C4-HSL) was identified in T. maritimum NCIMB2154(T) by LC-MS. A degradation activity for long-acyl AHLs (C10-HSL) was subsequently demonstrated in T. maritimum NCIMB2154(T). The acidification of the culture medium after degradation did not allow the recovery of C10-HSL, which indicates a possible acylase-type degradation activity. Even though the physiological processes under the control of AHL-mediated QS in T. maritimum need to be further characterized, this discovery extends the paradigm of AHL-mediated QS signalling beyond the Proteobacteria and reinforces its ecological significance. PMID:20377642

  8. Paraoxonase 2 modulates a proapoptotic function in LS174T cells in response to quorum sensing molecule N-(3-oxododecanoyl)-L-homoserine lactone.

    Tao, Shiyu; Luo, Yanwen; Bin He; Liu, Jie; Qian, Xi; Ni, Yingdong; Zhao, Ruqian

    2016-01-01

    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. PMID:27364593

  9. Quorum Sensing Activity of Serratia fonticola Strain RB-25 Isolated from an Ex-landfill Site

    Robson Ee

    2014-03-01

    Full Text Available Quorum sensing is a unique bacterial communication system which permits bacteria to synchronize their behaviour in accordance with the population density. The operation of this communication network involves the use of diffusible autoinducer molecules, termed N-acylhomoserine lactones (AHLs. Serratia spp. are well known for their use of quorum sensing to regulate the expression of various genes. In this study, we aimed to characterized the AHL production of a bacterium designated as strain RB-25 isolated from a former domestic waste landfill site. It was identified as Serratia fonticola using matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF mass spectrometry analysis and this was confirmed by 16S ribosomal DNA sequencing. High resolution triple quadrupole liquid chromatography-mass spectrometry analysis of S. fonticola strain RB-25 spent culture supernatant indicated the existence of three AHLs namely: N-butyryl-L-homoserine lactone (C4-HSL, N-hexanoyl-L-homoserine lactone (C6-HSL and N-(3-oxohexanoyl homoserine-lactone (3-oxo-C6 HSL. This is the first report of the production of these AHLs in S. fonticola.

  10. Pseudomonas aeruginosa Quorum Sensing Molecule N-(3-Oxododecanoyl)-L-Homoserine-Lactone Induces HLA-G Expression in Human Immune Cells.

    Bortolotti, Daria; LeMaoult, Joel; Trapella, Claudio; Di Luca, Dario; Carosella, Edgardo D; Rizzo, Roberta

    2015-10-01

    HLA-G is a nonclassical class I human leukocyte antigen (HLA) involved in mechanisms of immune tolerance. The objective of this study was to determine whether N-(3-oxododecanoyl)-l-homoserine lactone (3O-C12-HSL), a quorum sensing molecule produced by Pseudomonas aeruginosa, could modify HLA-G expression to control the host immune response. We evaluated the ability of 3O-C12-HSL to induce HLA-G expression in primary immune cells, monocytes (U937 and THP1), and T-cell lines (Jurkat) in vitro and analyzed the cellular pathway responsible for HLA-G expression. We studied the HLA-G promoter with a luciferase assay and interleukin-10 (IL-10) and p38/CREB signaling with enzyme-linked immunosorbent assay and immunofluorescence, respectively. We observed that 3O-C12-HSL is able to induce HLA-G expression in human monocytes and T cells. We showed that the induction of HLA-G by 3O-C12-HSL is p38/CREB and IL-10 dependent. 3O-C12-HSL treatment is able to arrest only the U937 cell cycle, possibly due to the peculiar expression of the ILT2 receptor in the U937 cell line. Our observations suggest HLA-G as a mechanism to create a protected niche for the bacterial reservoir, similar to the role of HLA-G molecules during viral infections. PMID:26195547

  11. A proteomic analysis of Arabidopsis thaliana seedling responses to 3-oxo-octanoyl-homoserine lactone, a bacterial quorum-sensing signal

    Highlights: ► 3OC8-HSL can change the expression of diverse proteins in Arabidopsis. ► 3OC8-HSL responsive proteins were identified using MALDI-TOF-MS. ► Plant could have an extensive range of functional responses to bacterial AHL. -- Abstract: N-acyl-homoserine lactones (AHLs) are a class of bacterial quorum-sensing (QS) signals that are commonly used by Gram-negative bacteria for cell-to-cell communication. Recently, it has become evident that AHLs can regulate plant root growth and trigger plant defense responses; however, little is known about the plant response mechanisms to bacterial QS signals. In this study, we used a proteomic approach to investigate the responses of Arabidopsis thaliana seedlings to N-3-oxo-octanoyl-homoserine lactone (3OC8-HSL), a bacterial QS signal. The results revealed that the abundance of 53 protein spots was significantly altered; two thirds of these proteins were found to be up-regulated after 3OC8-HSL treatment. Thirty-four proteins were identified using MALDI-TOF-MS. These 3OC8-HSL-responsive proteins, in addition to one protein of unknown function, are implicated in a variety of physiological processes, including metabolism of carbohydrate and energy, protein biosynthesis and quality control systems, defense response and signal transduction and cytoskeleton remodeling. Our bioinformatic analysis indicated that the chloroplasts are the intracellular organelles most influenced by the exposure to 3OC8-HSL. Our data indicate that plants have an extensive range of functional responses to bacterial AHLs that may play important roles in the interaction between plants and bacteria.

  12. A proteomic analysis of Arabidopsis thaliana seedling responses to 3-oxo-octanoyl-homoserine lactone, a bacterial quorum-sensing signal

    Miao, Chunjuan, E-mail: chunjuanjay@163.com [Biology Institute, Hebei Academy of Sciences, Shijiazhuang 050051 (China); Hebei Engineering and Technology Center of Microbiological Control on Main Crop Disease, Shijiazhuang 050051 (China); Liu, Fang, E-mail: liufang830818@126.com [Biology Institute, Hebei Academy of Sciences, Shijiazhuang 050051 (China); Hebei Engineering and Technology Center of Microbiological Control on Main Crop Disease, Shijiazhuang 050051 (China); Zhao, Qian, E-mail: zhqbluesea@163.com [Biology Institute, Hebei Academy of Sciences, Shijiazhuang 050051 (China); Hebei Engineering and Technology Center of Microbiological Control on Main Crop Disease, Shijiazhuang 050051 (China); Jia, Zhenhua, E-mail: zhenhuaj@hotmail.com [Biology Institute, Hebei Academy of Sciences, Shijiazhuang 050051 (China); Hebei Engineering and Technology Center of Microbiological Control on Main Crop Disease, Shijiazhuang 050051 (China); Song, Shuishan, E-mail: shuishans@hotmail.com [Biology Institute, Hebei Academy of Sciences, Shijiazhuang 050051 (China); Hebei Engineering and Technology Center of Microbiological Control on Main Crop Disease, Shijiazhuang 050051 (China)

    2012-10-19

    Highlights: Black-Right-Pointing-Pointer 3OC8-HSL can change the expression of diverse proteins in Arabidopsis. Black-Right-Pointing-Pointer 3OC8-HSL responsive proteins were identified using MALDI-TOF-MS. Black-Right-Pointing-Pointer Plant could have an extensive range of functional responses to bacterial AHL. -- Abstract: N-acyl-homoserine lactones (AHLs) are a class of bacterial quorum-sensing (QS) signals that are commonly used by Gram-negative bacteria for cell-to-cell communication. Recently, it has become evident that AHLs can regulate plant root growth and trigger plant defense responses; however, little is known about the plant response mechanisms to bacterial QS signals. In this study, we used a proteomic approach to investigate the responses of Arabidopsis thaliana seedlings to N-3-oxo-octanoyl-homoserine lactone (3OC8-HSL), a bacterial QS signal. The results revealed that the abundance of 53 protein spots was significantly altered; two thirds of these proteins were found to be up-regulated after 3OC8-HSL treatment. Thirty-four proteins were identified using MALDI-TOF-MS. These 3OC8-HSL-responsive proteins, in addition to one protein of unknown function, are implicated in a variety of physiological processes, including metabolism of carbohydrate and energy, protein biosynthesis and quality control systems, defense response and signal transduction and cytoskeleton remodeling. Our bioinformatic analysis indicated that the chloroplasts are the intracellular organelles most influenced by the exposure to 3OC8-HSL. Our data indicate that plants have an extensive range of functional responses to bacterial AHLs that may play important roles in the interaction between plants and bacteria.

  13. Acyl-homoserine lactones produced by Pantoea sp. isolated from the "maize white spot" foliar disease.

    Pomini, Armando M; Paccola-Meirelles, Luzia D; Marsaioli, Anita J

    2007-02-21

    The "maize white spot" foliar disease is a problem of increasing importance to Brazilian maize crops. A bacterium isolated from water-soaked lesions from infected maize leaves was pathogenic in biological assays in vivo. It was identified as a Gram-negative, nonsporulating, facultative anaerobic bacterium, belonging to the genus Pantoea. Chemical study of the extracts from bacterial cultivation media allowed the identification of (S)-(-)-N-butanoyl-homoserine lactone and trace amounts of N-hexanoyl-homoserine lactone, widely recognized quorum-sensing signaling substances employed in cell-to-cell communication systems. The absolute configuration of natural (S)-(-)-N-butanoyl-homoserine lactone was determined by gas chromatography-flame ionization detection with a chiral stationary phase and by comparison of circular dichroism spectroscopic data with enantiopure synthetic substances. Biological evaluations with reporter Agrobacterium tumefaciens NTL4(pZLR4) were carried out with synthetic and natural products and also with extracts from maize leaves contaminated with the isolated bacterium, as well as from healthy leaves. PMID:17256964

  14. The Pseudomonas aeruginosa quorum sensing signal molecule N-(3-oxododecanoyl) homoserine lactone enhances keratinocyte migration and induces Mmp13 gene expression in vitro

    Paes, Camila, E-mail: camilaquinetti@gmail.com [University of Tokyo, Department of Gerontological Nursing/Wound Care Management, Graduate School of Medicine, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Nakagami, Gojiro, E-mail: gojiron-tky@umin.ac.jp [University of Tokyo, Department of Gerontological Nursing/Wound Care Management, Graduate School of Medicine, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Minematsu, Takeo, E-mail: tminematsu-tky@umin.ac.jp [University of Tokyo, Department of Gerontological Nursing/Wound Care Management, Graduate School of Medicine, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Nagase, Takashi, E-mail: tnagase@fb3.so-net.ne.jp [University of Tokyo, Department of Gerontological Nursing/Wound Care Management, Graduate School of Medicine, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Huang, Lijuan, E-mail: koureikenhlj@gmail.com [University of Tokyo, Department of Gerontological Nursing/Wound Care Management, Graduate School of Medicine, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Sari, Yunita, E-mail: yunita-tky@umin.ac.jp [University of Tokyo, Department of Gerontological Nursing/Wound Care Management, Graduate School of Medicine, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Sanada, Hiromi, E-mail: hsanada-tky@umin.ac.jp [University of Tokyo, Department of Gerontological Nursing/Wound Care Management, Graduate School of Medicine, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)

    2012-10-19

    Highlights: Black-Right-Pointing-Pointer An evidence of the positive effect of AHL on epithelialization process is provided. Black-Right-Pointing-Pointer AHL enhances keratinocyte's ability to migrate in an in vitro scratch wound model. Black-Right-Pointing-Pointer AHL induces the expression of Mmp13. Black-Right-Pointing-Pointer Topical application of AHL represents a possible strategy to treat chronic wounds. -- Abstract: Re-epithelialization is an essential step of wound healing involving three overlapping keratinocyte functions: migration, proliferation and differentiation. While quorum sensing (QS) is a cell density-dependent signaling system that enables bacteria to regulate the expression of certain genes, the QS molecule N-(3-oxododecanoyl) homoserine lactone (AHL) exerts effects also on mammalian cells in a process called inter-kingdom signaling. Recent studies have shown that AHL improves epithelialization in in vivo wound healing models but detailed understanding of the molecular and cellular mechanisms are needed. The present study focused on the AHL as a candidate reagent to improve wound healing through direct modulation of keratinocyte's activity in the re-epithelialization process. Results indicated that AHL enhances the keratinocyte's ability to migrate in an in vitro scratch wound healing model probably due to the high Mmp13 gene expression analysis after AHL treatment that was revealed by real-time RT-PCR. Inhibition of activator protein 1 (AP-1) signaling pathway completely prevented the migration of keratinocytes, and also resulted in a diminished Mmp13 gene expression, suggesting that AP-1 might be essential in the AHL-induced migration. Taken together, these results imply that AHL is a promising candidate molecule to improve re-epithelialization through the induction of migration of keratinocytes. Further investigation is needed to clarify the mechanism of action and molecular pathway of AHL on the keratinocyte migration

  15. The Pseudomonas aeruginosa quorum sensing signal molecule N-(3-oxododecanoyl) homoserine lactone enhances keratinocyte migration and induces Mmp13 gene expression in vitro

    Highlights: ► An evidence of the positive effect of AHL on epithelialization process is provided. ► AHL enhances keratinocyte’s ability to migrate in an in vitro scratch wound model. ► AHL induces the expression of Mmp13. ► Topical application of AHL represents a possible strategy to treat chronic wounds. -- Abstract: Re-epithelialization is an essential step of wound healing involving three overlapping keratinocyte functions: migration, proliferation and differentiation. While quorum sensing (QS) is a cell density-dependent signaling system that enables bacteria to regulate the expression of certain genes, the QS molecule N-(3-oxododecanoyl) homoserine lactone (AHL) exerts effects also on mammalian cells in a process called inter-kingdom signaling. Recent studies have shown that AHL improves epithelialization in in vivo wound healing models but detailed understanding of the molecular and cellular mechanisms are needed. The present study focused on the AHL as a candidate reagent to improve wound healing through direct modulation of keratinocyte’s activity in the re-epithelialization process. Results indicated that AHL enhances the keratinocyte’s ability to migrate in an in vitro scratch wound healing model probably due to the high Mmp13 gene expression analysis after AHL treatment that was revealed by real-time RT-PCR. Inhibition of activator protein 1 (AP-1) signaling pathway completely prevented the migration of keratinocytes, and also resulted in a diminished Mmp13 gene expression, suggesting that AP-1 might be essential in the AHL-induced migration. Taken together, these results imply that AHL is a promising candidate molecule to improve re-epithelialization through the induction of migration of keratinocytes. Further investigation is needed to clarify the mechanism of action and molecular pathway of AHL on the keratinocyte migration process.

  16. Synthesis and biological evaluation of triazole-containing N-acyl homoserine lactones as quorum sensing modulators

    Stacy, Danielle M.; Le Quement, Sebastian T.; Hansen, Casper L.; Clausen, Janie W.; Tolker-Nielsen, Tim; Brummond, Jacob W.; Givskov, Michael; Nielsen, Thomas Eiland; Blackwell, Helen E.

    2013-01-01

    triazole-containing analogs of natural N-acyl l-homoserine lactone (AHL) signals as non-native QS agonists and antagonists in Gram-negative bacteria. We synthesized 72 triazole derivatives of five broad structure types in high yields and purities using efficient Cu(i)-catalyzed azide–alkyne couplings....... These compounds were evaluated for their ability to activate or inhibit two QS receptors from two prevalent pathogens – LasR from Pseudomonas aeruginosa and AbaR from Acinetobacter baumannii – using bacterial reporter strains. Several triazole derivatives were identified that were capable of strongly...

  17. Chemical mechanism and substrate specificity of RhlI, an acylhomoserine lactone synthase from Pseudomonas aeruginosa.

    Raychaudhuri, Aniruddha; Jerga, Agoston; Tipton, Peter A

    2005-03-01

    The enzyme RhlI catalyzes the formation of N-butyrylhomoserine lactone from S-adenosylmethionine and N-butyrylacyl carrier protein. N-Butyrylhomoserine lactone serves as a quorum-sensing signal molecule in Pseudomonas aeruginosa, and is implicated in the regulation of many processes involved in bacterial virulence and infectivity. The P. aeruginosa genome contains three genes encoding acyl carrier proteins. We have cloned all three genes, expressed the acyl carrier proteins, and characterized each as a substrate for RhlI. A continuous, spectrophotometric assay was developed to facilitate kinetic and mechanistic studies of RhlI. Acp1, which has not been characterized previously, was a good substrate for RhlI, with a K(m) of 7 microM; the reaction proceeded with a k(cat) value of 0.35 s(-1). AcpP, which supports fatty acid biosynthesis, was also a good substrate in the RhlI reaction, where k(cat) was 0.46 s(-1), and the K(m) for AcpP was 6 microM. The third acyl carrier protein, Acp3, was a poor substrate for RhlI, with a K(m) of 280 microM; k(cat) was 0.03 s(-1). Taken together with microarray data from the literature which show that expression of the gene encoding Acp1 is under the control of the quorum-sensing system, our data suggest that Acp1 is likely to be the substrate for RhlI in vivo. Isotope labeling studies were conducted to investigate the chemical mechanism of the RhlI-catalyzed lactonization reaction. Solvent deuterons were not incorporated into product, which implicates a direct attack mechanism in which the carboxylate oxygen of the presumptive N-butyryl-SAM intermediate attacks the methylene carbon adjacent to the sulfonium ion. Alternative mechanisms, in which N-butyrylvinylglycine is formed via elimination of methylthioadenosine, were ruled out on the basis of the observation that RhlI failed to convert authentic N-butyrylvinylglycine to N-butyryl-L-homoserine lactone. PMID:15723540

  18. Quorum sensing in gram-negative bacteria

    Wu, H.; Song, Z.J.; Høiby, N.; Givskov, Michael Christian

    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 and...

  19. Detection of the quorum sensing signal molecule N-Dodecanoyl-DL-homoserine lactone below 1 nanomolarconcentrations using surface enhanced Raman spectroscopy

    Claussen, Anetta; Abdali, Salim; Berg, Rolf W.;

    2013-01-01

    To the best of our knowledge we here for the first time demonstrate surface enhanced Raman spectroscopy (SERS) to detect a quorum sensing (QS) signal molecule below 1 nM concentration in both ultrapure water and under physiological conditions. Based on our results, SERS shows promise as a highly ...

  20. PA0305 of Pseudomonas aeruginosa is a quorum quenching acylhomoserine lactone acylase belonging to the Ntn hydrolase superfamily

    Wahjudi, Mariana; Papaioannou, Evelina; Hendrawati, Oktavia; van Assen, Aart H. G.; van Merkerk, Ronald; Cool, Robbert H.; Poelarends, Gerrit J.; Quax, Wim

    2011-01-01

    The Pseudomonas aeruginosa PAO1 genome has at least two genes, pvdQ and quiP, encoding acylhomoserine lactone (AHL) acylases. Two additional genes, pa 1893 and pa0305, have been predicted to encode penicillin acylase proteins, but have not been characterized. Initial studies on a pa0305 transposon i

  1. Probing the impact of ligand binding on the acyl-homoserine lactone-hindered transcription factor EsaR of Pantoea stewartii subsp. stewartii.

    Schu, Daniel J; Ramachandran, Revathy; Geissinger, Jared S; Stevens, Ann M

    2011-11-01

    The quorum-sensing regulator EsaR from Pantoea stewartii subsp. stewartii is a LuxR homologue that is inactivated by acyl-homoserine lactone (AHL). In the corn pathogen P. stewartii, production of exopolysaccharide (EPS) is repressed by EsaR at low cell densities. However, at high cell densities when high concentrations of its cognate AHL signal are present, EsaR is inactivated and derepression of EPS production occurs. Thus, EsaR responds to AHL in a manner opposite to that of most LuxR family members. Depending on the position of its binding site within target promoters, EsaR serves as either a repressor or activator in the absence rather than in the presence of its AHL ligand. The effect of AHL on LuxR homologues has been difficult to study in vitro because AHL is required for purification and stability. EsaR, however, can be purified without AHL enabling an in vitro analysis of the response of the protein to ligand. Western immunoblots and pulse-chase experiments demonstrated that EsaR is stable in vivo in the absence or presence of AHL. Limited in vitro proteolytic digestions of a biologically active His-MBP tagged version of EsaR highlighted intradomain and interdomain conformational changes that occur in the protein in response to AHL. Gel filtration chromatography of the full-length fusion protein and cross-linking of the N-terminal domain both suggest that this conformational change does not impact the multimeric state of the protein. These findings provide greater insight into the diverse mechanisms for AHL responsiveness found within the LuxR family. PMID:21949066

  2. Functional characterization of a soybean growth stimulator Bradyrhizobium sp. strain SR-6 showing acylhomoserine lactone production.

    Ali, Amanat; Ayesha; Hameed, Sohail; Imran, Asma; Iqbal, Mazhar; Iqbal, Javed; Oresnik, Ivan J

    2016-09-01

    A soybean nodule endophytic bacterium Bradyrhizobium sp. strain SR-6 was characterized for production of acyl homoserine lactones (AHLs) as quorum sensing molecules. Mass spectrometry analysis of AHLs revealed the presence of C6-HSL, 3OH-C6-HSL, C8-HSL, C10-HSL, 3oxoC10-HSL, 3oxo-C12-HSL and 3OH-C12-HSL which are significantly different from those reported earlier in soybean symbionts. Purified AHL extracts significantly improved wheat and soybean seedling growth and root hair development along with increased soybean nodulation under axenic conditions. A positive correlation was observed among in vivo nitrogenase and catalase enzyme activities of the strain SR-6. Transmission electron microscopic analysis showed the cytochemical localization of catalase activity within the bacteroids, specifically attached to the peribacteroidal membrane. Root and nodule colonization proved rhizosphere competence of SR-6. The inoculation of SR-6 resulted in increased shoot length (13%), plant dry matter (50%), grain weight (16%), seed yield (20%) and N-uptake (14%) as compared to non-inoculated soybean plants. The symbiotic bacterium SR-6 has potential to improve soybean growth and yield in sub-humid climate of Azad Jammu and Kashmir region of Pakistan. The production and mass spectrometric profiling of AHLs as well as in vivo cytochemical localization of catalase enzyme activity in soybean Bradyrhizobium sp. have never been reported earlier elsewhere before our these investigations. PMID:27242370

  3. Quorum Sensing Activity in Pandoraea pnomenusa RB38

    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.

  4. Specificity of acyl-homoserine lactone synthases examined by mass spectrometry.

    Gould, Ty A; Herman, Jake; Krank, Jessica; Murphy, Robert C; Churchill, Mair E A

    2006-01-01

    Many gram-negative bacteria produce a specific set of N-acyl-L-homoserine-lactone (AHL) signaling molecules for the purpose of quorum sensing, which is a means of regulating coordinated gene expression in a cell-density-dependent manner. AHLs are produced from acylated acyl-carrier protein (acyl-ACP) and S-adenosyl-L-methionine by the AHL synthase enzyme. The appearance of specific AHLs is due in large part to the intrinsic specificity of the enzyme for subsets of acyl-ACP substrates. Structural studies of the Pantoea stewartii enzyme EsaI and AHL-sensitive bioassays revealed that threonine 140 in the acyl chain binding pocket directs the enzyme toward production of 3-oxo-homoserine lactones. Mass spectrometry was used to examine the range of AHL molecular species produced by AHL synthases under a variety of conditions. An AHL selective normal-phase chromatographic purification with addition of a deuterated AHL internal standard was followed by reverse-phase liquid chromatography-tandem mass spectrometry in order to obtain estimates of the relative amounts of different AHLs from biological samples. The AHLs produced by wild-type and engineered EsaI and LasI AHL synthases show that intrinsic specificity and different cellular conditions influence the production of AHLs. The threonine at position 140 in EsaI is important for the preference for 3-oxo-acyl-ACPs, but the role of the equivalent threonine in LasI is less clear. In addition, LasI expressed in Escherichia coli produces a high proportion of unusual AHLs with acyl chains consisting of an odd number of carbons. Furthermore, these studies offer additional methods that will be useful for surveying and quantitating AHLs from different sources. PMID:16385066

  5. Profile of the culturable microbiome capable of producing acyl-homoserine lactone in the tobacco phyllosphere

    Di Lv; Anzhou Ma; Xuanming Tang; Zhihui Bai; Hongyan Qi; Guoqiang Zhuang

    2013-01-01

    Bacterial populations coexisting in the phyllosphere niche have important effects on plant health.Quorum sensing (QS) allows bacteria to communicate via diffusible signal molecules,but QS-dependent behaviors in phyllosphere bacterial populations are poorly understood.We investigate the dense and diverse N-acyl-homoserine lactone (AHL)-producing phyllosphere bacteria living on tobacco leaf surfaces via a culture-dependent method and 16S rRNA gene sequencing.Our results indicated that approximately 7.9%-11.7%of the culturable leaf-associated bacteria have the ability to produce AHL based on the assays using whole-cell biosensors.Sequencing of the 16S rRNA gene assigned the AHL-producing strains to two phylogenetic groups,with Gammaproteobacteria (93%) as the predominant group,followed by Alphaproteobacteria.All of the AHL-producing Alphaproteobacteria were affiliated with the genus Rhizobium,whereas the AHL-producing bacteria belonging to the Gammaproteobacteria mainly fell within the genera Pseudomonas,Acinetobacter,Citrobacter,Enterobacter,Pantoea and Serratia.The bioassays of supernatant extracts revealed that a portion of the strains have a remarkable AHL profile for AHL induction activity using the two different biosensors,and one compound in the active extract of a representative isolate,NTL223,corresponded to 3-oxo-hexanoyl-homoserine lactone.A large population size and diversity of bacteria capable of AHL-driven QS were found to cohabit on leaves,implying that cross-communication based AHL-type QS may be common in the phyllosphere.Furthermore,this study provides a general snapshot of a potential valuable application of AHL-producing bacteria inhabiting leaves for their presumable ecological roles in the phyllosphere.

  6. Identification of Quorum-Sensing Signal Molecules and a Biosynthetic Gene in Alicycliphilus sp. Isolated from Activated Sludge.

    Morohoshi, Tomohiro; Okutsu, Noriya; Xie, Xiaonan; Ikeda, Tsukasa

    2016-01-01

    Activated sludge is a complicated mixture of various microorganisms that is used to treat sewage and industrial wastewater. Many bacteria produce N-acylhomoserine lactone (AHL) as a quorum-sensing signal molecule to regulate the expression of the exoenzymes used for wastewater treatment. Here, we isolated an AHL-producing bacteria from an activated sludge sample collected from an electronic component factory, which we named Alicycliphilus sp. B1. Clone library analysis revealed that Alicycliphilus was a subdominant genus in this sample. When we screened the activated sludge sample for AHL-producing strains, 12 of 14 the AHL-producing isolates were assigned to the genus Alicycliphilus. A putative AHL-synthase gene, ALISP_0667, was cloned from the genome of B1 and transformed into Escherichia coli DH5α. The AHLs were extracted from the culture supernatants of the B1 strain and E. coli DH5α cells harboring the ALISP_0667 gene and were identified by liquid chromatography-mass spectrometry as N-(3-hydroxydecanoyl)-l-homoserine lactone and N-(3-hydroxydodecanoyl)-l-homoserine lactone. The results of comparative genomic analysis suggested that the quorum-sensing genes in the B1 strain might have been acquired by horizontal gene transfer within activated sludge. PMID:27490553

  7. A Strategy for Antagonizing Quorum Sensing

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

    2011-12-31

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

  8. Bacterial quorum sensing and nitrogen cycling in rhizosphere soil

    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.

  9. Long-chain acyl-homoserine lactones from Methylobacterium mesophilicum: synthesis and absolute configuration.

    Pomini, Armando M; Cruz, Pedro L R; Gai, Cláudia; Araújo, Welington L; Marsaioli, Anita J

    2009-12-01

    The acyl-homoserine lactones (acyl-HSLs) produced by Methylobacterium mesophilicum isolated from orange trees infected with the citrus variegated chlorosis (CVC) disease have been studied, revealing the occurrence of six long-chain acyl-HSLs, i.e., the saturated homologues (S)-N-dodecanoyl (1) and (S)-N-tetradecanoyl-HSL (5), the uncommon odd-chain N-tridecanoyl-HSL (3), the new natural product (S)-N-(2E)-dodecenoyl-HSL (2), and the rare unsaturated homologues (S)-N-(7Z)-tetradecenoyl (4) and (S)-N-(2E,7Z)-tetradecadienyl-HSL (6). The absolute configurations of all HSLs were determined as 3S. Compounds 2 and 6 were synthesized for the first time. Antimicrobial assays with synthetic acyl-HSLs against Gram-positive bacterial endophytes co-isolated with M. mesophilicum from CVC-infected trees revealed low or no antibacterial activity. PMID:19919062

  10. Towards Predictive Modeling of Information Processing in Microbial Ecosystems With Quorum-Sensing Interactions

    Yusufaly, Tahir; Boedicker, James

    Bacteria communicate using external chemical signals in a process known as quorum sensing. However, the efficiency of this communication is reduced by both limitations on the rate of diffusion over long distances and potential interference from neighboring strains. Therefore, having a framework to quantitatively predict how spatial structure and biodiversity shape information processing in bacterial colonies is important, both for understanding the evolutionary dynamics of natural microbial ecosystems, and for the rational design of synthetic ecosystems with desired computational properties. As a first step towards these goals, we implement a reaction-diffusion model to study the dynamics of a LuxI/LuxR quorum sensing circuit in a growing bacterial population. The spatiotemporal concentration profile of acyl-homoserine lactone (AHL) signaling molecules is analyzed, and used to define a measure of physical and functional signaling network connectivity. From this, we systematically investigate how different initial distributions of bacterial populations influence the subsequent efficiency of collective long-range signal propagation in the population. We compare our results with known experimental data, and discuss limitations and extensions to our modeling framework.-/abstract-

  11. Quorum sensing in Gram-negative bacteria

    WU Hong; SONG Zhijun; Niels HФIBY; Michael GIVSKOV

    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 and particularly higher organisms,covering a variety of functions ranging from pathogenic to symbiotic interactions.The detailed knowledge of these bacterial communication systems has opened completely new perspectives for controlling undesired microbial activities.

  12. Effects of quorum sensing autoinducer degradation gene on virulence and biofilm formation of Pseudomonas aeruginosa

    2007-01-01

    The aiiA gene from Bacillus thuringiensis was cloned into the Pseudomonas/E. coli shuttle vector and transformed into Pseudomonas aeruginosa strain PAO1. Western blotting showed that the AiiA protein was expressed in PAO1. After induction by IPTG for 6 h and 18 h, expression of the aiiA gene in PAO1 completely degraded the quorum sensing autoinducers N-acylhomoserine lactones (AHLs): N-oxododecanoyl-L-homoserine lactone (OdDHL) and N-butyryl-L-homoserine lactone (BHL). The re- duced amount of AHLs in PAO1 was also correlated with decreased expression and production of several virulence factors such as elastase and pyocyanin. AiiA expression also influenced bacterial swarming motility. Most importantly, our studies indicated that aiiA played significant roles in P. aeruginosa biofilm formation and dispersion, as observed by the differences of the biofilm formation on liquid and solid surfaces, and biofilm structures under a scanning electron microscope.

  13. Effects of quorum sensing autoinducer degradation gene on virulence and biofilm formation of Pseudomonas aeruginosa

    WANG Yao; DAI Yue; ZHANG Yong; HU YangBo; YANG BaoYu; CHEN ShiYun

    2007-01-01

    The aiiA gene from Bacillus thuringiensis was cloned into the Pseudomonas/E. coli shuttle vector and transformed into Pseudomonas aeruginosa strain PAO1. Western blotting showed that the AiiA protein was expressed in PAO1. After induction by IPTG for 6 h and 18 h, expression of the aiiA gene in PAO1completely degraded the quorum sensing autoinducers N-acylhomoserine lactones (AHLs):N-oxododecanoyI-L-homoserine lactone (OdDHL) and N-butyryI-L-homoserine lactone (BHL). The reduced amount of AHLs in PAO1 was also correlated with decreased expression and production of several virulence factors such as elastase and pyocyanin. AiiA expression also influenced bacterial swarming motility. Most importantly, our studies indicated that aiiA played significant roles in P.aeruginosa biofilm formation and dispersion, as observed by the differences of the biofilm formation on liquid and solid surfaces, and biofilm structures under a scanning electron microscope.

  14. Quorum sensing en la asociación beneficiosa de las bacterias con las plantas

    Marcia M. Rojas Badía

    2012-06-01

    Full Text Available Título en ingles: Quorum sensing in beneficial plant-bacteria associations ResumenSe conoce que el quorum sensing es un atributo común de muchas especies bacterianas y que puede ser un carácter universal de las bacterias. Actualmente se están describiendo a un paso más rápido nuevas señales y nuevos sistemas de regulación por quorum sensing y se han desarrollado las investigaciones acerca de la comunicación célula-célula en bacterias basada en el mecanismo de quorum sensing. En los ambientes naturales existen muchas bacterias que viven juntas y utilizan varias clases de moléculas señales. Dentro de las señales especie específicas predominan las acilhomoserín lactonas (AHLs, pero ya se han descrito una amplia diversidad de moléculas involucradas en la señalización célula-célula. Numerosos bioensayos y sistemas sensores se han desarrollado para la detección, caracterización y cuantificación de las AHLs. Se han obtenido evidencias de la acción de estas moléculas señales en la colonización de la rizosfera, el swarming, las interacciones simbióticas y la capacidad de interrumpir el proceso de señalización de otras bacterias que convivan en el mismo ambiente. Todas estas potencialidades de las bacterias que involucran el mecanismo de quorum sensing, pudieran ser utilizadas para fortalecerla acción estimuladora del crecimiento vegetal y el control biológico de patógenos en los agroecosistemas sostenibles. Palabras clave: comunicación celular; PGPB; control biológico; moléculas señal AbstractThe quorum sensing is a common attribute in some bacterial species. Currently, several signals and new regulation systems are describing and the researchers are very interested in the cell-cell communication based on quorum sensing mechanism. In the natural environments several bacteria are living together, then several types of signal molecules are using. The acylhomoserines lactones (AHLs, are predominant, but a wide range

  15. Quorum sensing inhibitors

    Rasmussen, Thomas Bovbjerg; Givskov, Michael Christian

    2006-01-01

    essential for growth of the bacteria, inhibition of QS does not impose harsh selective pressure for development of resistance as with antibiotics. Numerous chemical libraries of both natural and synthetic origin have been screened and several QS-inhibitory compounds have been identified. In animal pulmonary......Many opportunistic pathogenic bacteria rely on quorum sensing (QS) circuits as central regulators of virulence expression. In Pseudomonas aeruginosa, QS-regulated gene expression contributes to the formation and maintenance of biofilms and their tolerance to conventional antimicrobials and the host...

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

    Hansen, Mette Reimert

    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. The...... effect of replacing the acyl chain of the natural AHL ligand with a dipeptide was investigated. An in silico screening of N-dipeptido homoserine lactones against the protein responsible for the control of quorum sensing in P. aeruginosa identified a number of hits. The best hits were synthesized using a...

  17. Quorum Sensing Inhibition, Relevance to Periodontics

    Yada, Sudheer; B Kamalesh; Sonwane, Siddharth; Guptha, Indra; Swetha, R K

    2015-01-01

    Quorum sensing helps bacteria to communicate with each other and in coordinating their behavior. Many diseases of human beings, plants, and animals are mediated by quorum sensing. Various approaches are being tried to inhibit this communication to control the diseases caused by bacteria. Periodontal pathogens also communicate through quorum sensing and new approaches to treat periodontal disease using quorum sensing inhibition need to explored.

  18. Deducing receptor signaling parameters from in vivo analysis: LuxN/AI-1 quorum sensing in Vibrio harveyi

    Swem, Lee R.; Swem, Danielle L.; Wingreen, Ned S.; Bassler, Bonnie L.

    2008-01-01

    Summary Quorum sensing, a process of bacterial cell-cell communication, relies on production, detection, and response to autoinducer signaling molecules. Here we focus on LuxN, a nine transmembrane domain protein from Vibrio harveyi, and the founding example of membrane-bound receptors for acyl-homoserine lactone (AHL) autoinducers. Previously, nothing was known about signal recognition by membrane-bound AHL receptors. We used mutagenesis and suppressor analyses to identify the AHL-binding domain of LuxN, and discovered LuxN mutants that confer decreased and increased AHL sensitivity. Our analysis of dose-response curves of multiple LuxN mutants pins these inverse phenotypes on quantifiable opposing shifts in the free-energy bias of LuxN for its kinase and phosphatase states. To extract signaling parameters, we exploited a strong LuxN antagonist, one of fifteen small-molecule antagonists we identified. We find that quorum-sensing-mediated communication can be manipulated positively and negatively to control bacterial behavior, and that signaling parameters can be deduced from in vivo data. PMID:18692469

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

    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.

  20. LuxR homolog-independent gene regulation by acyl-homoserine lactones in Pseudomonas aeruginosa.

    Chugani, Sudha; Greenberg, Everett Peter

    2010-06-01

    Pseudomonas aeruginosa quorum control of gene expression involves three LuxR-type signal receptors LasR, RhlR, and QscR that respond to the LasI- and RhlI-generated acyl-homoserine lactone (acyl-HSL) signals 3OC12-HSL and C4-HSL. We found that a LasR-RhlR-QscR triple mutant responds to acyl-HSLs by regulating at least 37 genes. LuxR homolog-independent activation of the representative genes antA and catB also occurs in the wild type. Expression of antA was influenced the most by C10-HSL and to a lesser extent by other acyl-HSLs, including the P. aeruginosa 3OC12-HSL and C4-HSL signals. The ant and cat operons encode enzymes for the degradation of anthranilate to tricarboxylic acid cycle intermediates. Our results indicate that LuxR homolog-independent acyl-HSL control of the ant and cat operons occurs via regulation of antR, which codes for the transcriptional activator of the ant operon. Although P. aeruginosa has multiple pathways for anthranilate synthesis, one pathway-the kynurenine pathway for tryptophan degradation-is required for acyl-HSL activation of the ant operon. The kynurenine pathway is also the critical source of anthranilate for energy metabolism via the antABC gene products, as well as the source of anthranilate for synthesis of the P. aeruginosa quinolone signal. Our discovery of LuxR homolog-independent responses to acyl-HSLs provides insight into acyl-HSL signaling. PMID:20498077

  1. AHL-type quorum sensing and its regulation on symplasmata formation in Pantoea agglomerans YS19.

    Jiang, Jing; Wu, Suisui; Wang, Jieru; Feng, Yongjun

    2015-05-01

    Pantoea agglomerans YS19, an endophytic diazotrophic bacterium isolated from rice, is characterized by the formation of multicellular aggregate structure called symplasmata, which not only bestow the strong stress-resistance of the bacterium, but also contribute to the specific adaptation in the endophyte-host association. Acyl-homoserine lactones (AHLs), as the important signal molecule in the quorum sensing (QS) system of gram-negative bacteria, were demonstrated to regulate motility, cell-aggregation, and other bacterial behaviors. Here, the production of AHL by P. agglomerans YS19 and its regulation on the symplasmata formation were studied. It was revealed that the production of AHL by YS19 was initiated at the exponential growth stage and from then on, reached the peak values at the stationary growth stage in LB medium. The AHL was identified as N-3-oxooctanoyl-L-homoserine lactone (OOHL) by MALDI-TOF-MS analysis. The AHL synthesis gene pagI and receptor gene pagR in YS19 were cloned and phylogenetic analysis showed that they were high conservative among strains in species of P. agglomerans. It was revealed that AHL promoted the bacterial growth and symplasmata formation of YS19. Meanwhile, the colonization ability and growth-promoting effect of YS19 on the host plant were also enhanced by AHL. These results strongly suggest the pleiotropic effects of the AHL-type QS system in endophytic life of the strain. PMID:25283544

  2. Pseudomonas aeruginosa quorum-sensing signal molecules interfere with dendritic cell-induced T-cell proliferation

    Skindersø, Mette Elena; Zeuthen, Louise; Pedersen, Susanne Brix;

    2009-01-01

    -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...

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

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

    2003-02-01

    N-Acyl-L-homoserine-lactone-producing Serratia species are frequently encountered in spoiling foods of vegetable and protein origin. The role of quorum sensing in the food spoiling properties of these bacteria is currently being investigated. A set of luxR luxI homologous genes encoding a putative quorum sensor was identified in the N-(3-oxo-hexanoyl)-L-homoserine lactone (3-oxo-C6-HSL)-producing Serratia proteamaculans strain B5a. The 3-oxo-C6-HSL synthase SprI showed 79 % similarity with EsaI from Pantoea stewartii and the putative regulatory protein SprR was 86 % similar to the SpnR of Serratia 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. PMID:12624209

  4. Identification and characterization of an N-acylhomoserine lactone-dependent quorum-sensing system in Pseudomonas putida strain IsoF

    Steidle, A.; Allesen-Holm, M.; Riedel, K.;

    2002-01-01

    cloned a genomic region of the plant growth-promoting P. putida strain IsoF that, when present in trans, provoked induction of a bioluminescent AHL reporter plasmid. Sequence analysis identified a gene cluster consisting of four genes: ppuI and ppuR, whose predicted amino acid sequences are highly...

  5. Transcriptional Control during Quorum Sensing by LuxR and LuxR Homologues

    Faini, Marie Annette

    2003-01-01

    Quorum sensing is a mechanism used by many proteobacteria to regulate expression of target genes in a population-dependent manner. The quorum sensing system of Vibrio fischeri activates the luminescence (lux) operon when the autoinducer signaling molecule (N-3-oxohexanoyl homoserine lactone) is recognized and bound by the activator protein LuxR. LuxR subsequently binds to the lux box centered at à 42.5 bp upstream of the transcription initiation site and activates transcription from the lux...

  6. A negative regulator mediates quorum-sensing control of exopolysaccharide production in Pantoea stewartii subsp. stewartii

    von Bodman, Susanne Beck; Majerczak, Doris R.; Coplin, David L.

    1998-01-01

    Classical quorum-sensing (autoinduction) regulation, as exemplified by the lux system of Vibrio fischeri, requires N-acyl homoserine lactone (AHL) signals to stimulate cognate transcriptional activators for the cell density-dependent expression of specific target gene systems. For Pantoea stewartii subsp. stewartii, a bacterial pathogen of sweet corn and maize, the extracellular polysaccharide (EPS) stewartan is a major virulence factor, and its production is controlled by quorum sensing in a...

  7. N,N’-alkylated Imidazolium-Derivatives Act as Quorum-Sensing Inhibitors Targeting the Pectobacterium atrosepticum-Induced Symptoms on Potato Tubers

    Valérie Hélias

    2013-10-01

    Full Text Available Bacteria belonging to the Pectobacterium genus are the causative agents of the blackleg and soft-rot diseases that affect potato plants and tubers worldwide. In Pectobacterium, the expression of the virulence genes is controlled by quorum-sensing (QS and N-acylhomoserine lactones (AHLs. In this work, we screened a chemical library of QS-inhibitors (QSIs and AHL-analogs to find novel QSIs targeting the virulence of Pectobacterium. Four N,N’-bisalkylated imidazolium salts were identified as QSIs; they were active at the µM range. In potato tuber assays, two of them were able to decrease the severity of the symptoms provoked by P. atrosepticum. This work extends the range of the QSIs acting on the Pectobacterium-induced soft-rot disease.

  8. N,N'-alkylated Imidazolium-derivatives act as quorum-sensing inhibitors targeting the Pectobacterium atrosepticum-induced symptoms on potato tubers.

    des Essarts, Yannick Raoul; Sabbah, Mohamad; Comte, Arnaud; Soulère, Laurent; Queneau, Yves; Dessaux, Yves; Hélias, Valérie; Faure, Denis

    2013-01-01

    Bacteria belonging to the Pectobacterium genus are the causative agents of the blackleg and soft-rot diseases that affect potato plants and tubers worldwide. In Pectobacterium, the expression of the virulence genes is controlled by quorum-sensing (QS) and N-acylhomoserine lactones (AHLs). In this work, we screened a chemical library of QS-inhibitors (QSIs) and AHL-analogs to find novel QSIs targeting the virulence of Pectobacterium. Four N,N'-bisalkylated imidazolium salts were identified as QSIs; they were active at the µM range. In potato tuber assays, two of them were able to decrease the severity of the symptoms provoked by P. atrosepticum. This work extends the range of the QSIs acting on the Pectobacterium-induced soft-rot disease. PMID:24108370

  9. Bacterial quorum sensing and biofilm formation

    Quorum sensing is a cell density-dependent signaling system by which bacteria can regulate gene expression through the production, secretion, and subsequent detection of extracellular signaling molecules called autoinducers. Bacteria use quorum sensing to regulate various physiological activities, ...

  10. Quorum-sensing regulates biofilm formation in Vibrio scophthalmi

    García-Aljaro Cristina

    2012-12-01

    Full Text Available Abstract Background In a previous study, we demonstrated that Vibrio scophthalmi, the most abundant Vibrio species among the marine aerobic or facultatively anaerobic bacteria inhabiting the intestinal tract of healthy cultured turbot (Scophthalmus maximus, contains at least two quorum-sensing circuits involving two types of signal molecules (a 3-hydroxy-dodecanoyl-homoserine lactone and the universal autoinducer 2 encoded by luxS. The purpose of this study was to investigate the functions regulated by these quorum sensing circuits in this vibrio by constructing mutants for the genes involved in these circuits. Results The presence of a homologue to the Vibrio harveyi luxR gene encoding a main transcriptional regulator, whose expression is modulated by quorum–sensing signal molecules in other vibrios, was detected and sequenced. The V. scophthalmi LuxR protein displayed a maximum amino acid identity of 82% with SmcR, the LuxR homologue found in Vibrio vulnificus. luxR and luxS null mutants were constructed and their phenotype analysed. Both mutants displayed reduced biofilm formation in vitro as well as differences in membrane protein expression by mass-spectrometry analysis. Additionally, a recombinant strain of V. scophthalmi carrying the lactonase AiiA from Bacillus cereus, which causes hydrolysis of acyl homoserine lactones, was included in the study. Conclusions V. scophthalmi shares two quorum sensing circuits, including the main transcriptional regulator luxR, with some pathogenic vibrios such as V. harveyi and V. anguillarum. However, contrary to these pathogenic vibrios no virulence factors (such as protease production were found to be quorum sensing regulated in this bacterium. Noteworthy, biofilm formation was altered in luxS and luxR mutants. In these mutants a different expression profile of membrane proteins were observed with respect to the wild type strain suggesting that quorum sensing could play a role in the regulation of

  11. Structural elucidation and biological activity of acyl-homoserine lactones from the phytopathogen Pantoea ananatis Serrano 1928.

    Pomini, Armando M; Araújo, Welington L; Marsaioli, Anita J

    2006-08-01

    In Gram-negative bacteria, the acyl-homoserine lactones (acyl-HSLs) are the main signaling substances employed in cell-to-cell communication systems. This paper describes the chemical characterization of acyl-HSLs produced by the worldwide-spread phytopathogen Pantoea ananatis (Serrano 1928) by using gas chromatography-electron impact mass spectrometry. The absolute configuration of the major identified substance, (S)-(--)-N-hexanoyl-HSL, was determined with gas chromatography-flame ionization detection with a chiral capillary column. Biological activities of extracts, fractions, and synthetic products were evaluated with the specific reporter Agrobacterium tumefaciensNTL4(pZLR4) in beta-galactosidase expression assays. PMID:16900431

  12. Chemical Composition and Disruption of Quorum Sensing Signaling in Geographically Diverse United States Propolis

    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.

  13. Dynamics of AHL mediated quorum sensing under flow and non-flow conditions

    Quorum sensing (QS) describes the capability of microbes to communicate with each other by the aid of small molecules. Here we investigate the dynamics of QS-regulated gene expression induced by acylhomoserine lactones (AHLs) in Pseudomonas putida IsoF containing a green fluorescent protein-based AHL reporter. The fluorescence time course of individual colonies is monitored following the external addition of a defined AHL concentration to cells which had previously reached the QS-inactive state in AHL-free medium. Using a microfluidic setup the experiment is performed both under flow and non-flow conditions. We find that without supplying external AHL gene expression is induced without flow while flow suppresses the induction. Both without and with flow, at a low AHL concentration the fluorescence onset is significantly delayed while fluorescence starts to increase directly upon the addition of AHL at a high concentration. The differences between no flow and flow can be accounted for using a two-compartment model. This indicates AHL accumulation in a volume which is not affected by the flow. The experiments furthermore show significant cell-to-cell and colony-to-colony variability which is discussed in the context of a compartmentalized QS mechanism. (paper)

  14. Exploiting Quorum Sensing Interfering Strategies in Gram-Negative Bacteria for the Enhancement of Environmental Applications.

    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. PMID:26779175

  15. Genome sequence of Enterobacter sp. ST3, a quorum sensing bacterium associated with marine dinoflagellate

    Jin Zhou

    2016-03-01

    Full Text Available Phycosphere environment is a typical marine niche, harbor diverse populations of microorganisms, which are thought to play a critical role in algae host and influence mutualistic and competitive interactions. Understanding quorum sensing-based acyl-homoserine lactone (AHL language may shed light on the interaction between algal-associated microbial communities in the native environment. In this work, we isolated an epidermal bacterium (was tentatively named Enterobacter sp. ST3, and deposited in SOA China, the number is MCCC1K02277-ST3 from the marine dinoflagellate Scrippsiella trochoidea, and found it has the ability to produce short-chain AHL signal. In order to better understand its communication information at molecular level, the genomic map was investigated. The genome size was determined to be 4.81 Mb with a G + C content of 55.59%, comprising 6 scaffolds of 75 contigs containing 4647 protein-coding genes. The functional proteins were predicted, and 3534 proteins were assigned to COG functional categories. An AHL-relating gene, LuxR, was found in upstream position at contig 1. This genome data may provide clues to increase understanding of the chemical characterization and ecological behavior of strain ST3 in the phycosphere microenvironment.

  16. Potential Emergence of Multi-quorum Sensing Inhibitor Resistant (MQSIR) Bacteria.

    Koul, Shikha; Prakash, Jyotsana; Mishra, Anjali; Kalia, Vipin Chandra

    2016-03-01

    Expression of certain bacterial genes only at a high bacterial cell density is termed as quorum-sensing (QS). Here bacteria use signaling molecules to communicate among themselves. QS mediated genes are generally involved in the expression of phenotypes such as bioluminescence, biofilm formation, competence, nodulation, and virulence. QS systems (QSS) vary from a single in Vibrio spp. to multiple in Pseudomonas and Sinorhizobium species. The complexity of QSS is further enhanced by the multiplicity of signals: (1) peptides, (2) acyl-homoserine lactones, (3) diketopiperazines. To counteract this pathogenic behaviour, a wide range of bioactive molecules acting as QS inhibitors (QSIs) have been elucidated. Unlike antibiotics, QSIs don't kill bacteria and act at much lower concentration than those of antibiotics. Bacterial ability to evolve resistance against multiple drugs has cautioned researchers to develop QSIs which may not generate undue pressure on bacteria to develop resistance against them. In this paper, we have discussed the implications of the diversity and multiplicity of QSS, in acting as an arsenal to withstand attack from QSIs and may use these as reservoirs to develop multi-QSI resistance. PMID:26843692

  17. Inhibition of quorum sensing, biofilm, and spoilage potential in Shewanella baltica by green tea polyphenols.

    Zhu, Junli; Huang, Xuzheng; Zhang, Fang; Feng, Lifang; Li, Jianrong

    2015-12-01

    We investigated the quorum sensing (QS) system of Shewanella baltica and the anti-QS related activities of green tea polyphenols (TP) against spoilage bacteria in refrigerated large yellow croaker. Autoinducer-2 (AI-2) and the diketopiperazines (DKPs) cyclo-(L-Pro-L-Leu) and cyclo-(L-Pro-L-Phe) were detected in the culture extract of S. baltica XH2, however, no N-acylhomoserine lactones (AHLs) activity was observed. Green TP at sub-inhibitory concentrations interfered with AI-2 and DKPs activities of S. baltica without inhibiting cell growth and promoted degradation of AI-2. The green TP treatment inhibited biofilm development, exopolysaccharide production and swimming motility of S. baltica in a concentration- dependent manner. In addition, green TP decreased extracellular protease activities and trimethylamine production in S. baltica. A transcriptional analysis showed that green TP repressed the luxS and torA genes in S. baltica, which agreed with the observed reductions in QS activity and the spoilage phenotype. Epigallocatechin gallate (EGCG)-enriched in green TP significantly inhibited AI-2 activity of S. baltica. These findings strongly suggest that green TP could be developed as a new QS inhibitor for seafood preservation to enhance shelf life. PMID:26626353

  18. Nanomachine Computing by Quorum Sensing

    Wiedermann, Jiří

    Berlin: Springer, 2011 - (Kelemen, J.; Kelemenová, A.), s. 203-215. (Lecture Notes in Computer Science. 6610). ISBN 978-3-642-19999-8 R&D Projects: GA ČR GAP202/10/1333 Institutional research plan: CEZ:AV0Z10300504 Keywords : nanomachine computing * quorum sensing * nanomachines * molecular communication Subject RIV: IN - Informatics, Computer Science

  19. Genome Sequence of Dyella japonica Strain A8, a Quorum-Quenching Bacterium That Degrades N-Acylhomoserine Lactones, Isolated from Malaysian Tropical Soil

    Chen, Jian-Woon; Chan, Kok-Gan

    2012-01-01

    Dyella japonica strain A8 is a Malaysian tropical soil bacterial strain which shows N-acylhomoserine lactone-degrading activity. Here, we present its draft genome sequence. A putative quorum-quenching gene was identified based on the genome sequence analysis of strain A8. To the best of our knowledge, this is the first genome announcement of a member from the genus of Dyella, and this is also the first work that reports the quorum-quenching activity of Dyella japonica.

  20. A quorum-sensing-induced bacteriophage defense mechanism

    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...... sensing plays an important role in determining the susceptibility of E. coli to infection by bacteriophages ¿ and ¿. On the basis of our findings in the classical Escherichia coli-¿ model system, we suggest that quorum sensing may serve as a general strategy to protect bacteria specifically under...... 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...

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

    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

  2. Quorum Sensing Activity of Enterobacter asburiae Isolated from Lettuce Leaves

    Kok-Gan Chan

    2013-10-01

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

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

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

    2007-01-01

    Many pathogens control production of virulence factors by self-produced signals in a process called quorum sensing (QS). We demonstrate that acyl homoserine lactone (AHL) signals, which enable bacteria to express certain phenotypes in relation to cell density, are produced by a wide spectrum 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...

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

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

    2013-02-01

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

  5. Quorum Sensing in Extreme Environments

    Brendan P. Burns

    2013-01-01

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

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

    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...... 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 of...

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

    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.

  8. Quorum sensing mechanisms in fungi

    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.

  9. Quorum Sensing in Gram-Negative Bacteria

    BOŞGELMEZ-TINAZ, Gülgün

    2003-01-01

    It has become increasingly and widely recognised that bacteria do not live as isolated entities but instead exist as communities that exploit elaborate systems of intercellular communication to facilitate their adaptation to changing environmental conditions. A well-characterised example of such intercellular communication is quorum sensing. Quorum sensing depends on the production of diffusible signal molecules termed autoinducers or pheromones, which enable a bacterium to monitor its own ce...

  10. The BlcC (AttM) lactonase of Agrobacterium tumefaciens does not quench the quorum-sensing system that regulates Ti plasmid conjugative transfer.

    Khan, Sharik R; Farrand, Stephen K

    2009-02-01

    The conjugative transfer of Agrobacterium plasmids is controlled by a quorum-sensing system consisting of TraR and its acyl-homoserine lactone (HSL) ligand. The acyl-HSL is essential for the TraR-mediated activation of the Ti plasmid Tra genes. Strains A6 and C58 of Agrobacterium tumefaciens produce a lactonase, BlcC (AttM), that can degrade the quormone, leading some to conclude that the enzyme quenches the quorum-sensing system. We tested this hypothesis by examining the effects of the mutation, induction, or mutational derepression of blcC on the accumulation of acyl-HSL and on the conjugative competence of strain C58. The induction of blc resulted in an 8- to 10-fold decrease in levels of extracellular acyl-HSL but in only a twofold decrease in intracellular quormone levels, a measure of the amount of active intracellular TraR. The induction or mutational derepression of blc as well as a null mutation in blcC had no significant effect on the induction of or continued transfer of pTiC58 from donors in any stage of growth, including stationary phase. In matings performed in developing tumors, wild-type C58 transferred the Ti plasmid to recipients, yielding transconjugants by 14 to 21 days following infection. blcC-null donors yielded transconjugants 1 week earlier, but by the following week, transconjugants were recovered at numbers indistinguishable from those of the wild type. Donors mutationally derepressed for blcC yielded transconjugants in planta at numbers 10-fold lower than those for the wild type at weeks 2 and 3, but by week 4, the two donors showed no difference in recoverable transconjugants. We conclude that BlcC has no biologically significant effect on Ti plasmid transfer or its regulatory system. PMID:19011037

  11. Proteomic analysis of the quorum-sensing regulon in Pantoea stewartii and identification of direct targets of EsaR.

    Ramachandran, Revathy; Stevens, Ann M

    2013-10-01

    The proteobacterium Pantoea stewartii subsp. stewartii causes Stewart's wilt disease in maize when it colonizes the xylem and secretes large amounts of stewartan, an exopolysaccharide. The success of disease pathogenesis lies in the timing of bacterial virulence factor expression through the different stages of infection. Regulation is achieved through a quorum-sensing (QS) system consisting of the acyl-homoserine lactone (AHL) synthase, EsaI, and the transcription regulator EsaR. At low cell densities, EsaR represses transcription of itself and of rcsA, an activator of the stewartan biosynthesis operon; it also activates esaS, which encodes a small RNA (sRNA). Repression or activation ceases at high cell densities when EsaI synthesizes sufficient levels of the AHL ligand N-3-oxo-hexanoyl-L-homoserine lactone to bind and inactivate EsaR. This study aims to identify other genes activated or repressed by EsaR during the QS response. Proteomic analysis identified a QS regulon of more than 30 proteins. Electrophoretic mobility shift assays of promoters of genes encoding differentially expressed proteins distinguished direct targets of EsaR from indirect targets. Additional quantitative reverse transcription-PCR (qRT-PCR) and DNA footprinting analysis established that EsaR directly regulates the promoters of dkgA, glpF, and lrhA. The proteins encoded by dkgA, glpF, and lrhA are a 2,5-diketogluconate reductase, glycerol facilitator, and transcriptional regulator of chemotaxis and motility, respectively, indicating a more global QS response in P. stewartii than previously recognized. PMID:23913428

  12. Inhibition of Quorum Sensing-Controlled Virulence Factor Production in Pseudomonas aeruginosa PAO1 by Ayurveda Spice Clove (Syzygium Aromaticum Bud Extract

    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.

  13. Interfering with Bacterial Quorum Sensing.

    Reuter, Kerstin; Steinbach, Anke; Helms, Volkhard

    2016-01-01

    Quorum sensing (QS) describes the exchange of chemical signals in bacterial populations to adjust the bacterial phenotypes according to the density of bacterial cells. This serves to express phenotypes that are advantageous for the group and ensure bacterial survival. To do so, bacterial cells synthesize autoinducer (AI) molecules, release them to the environment, and take them up. Thereby, the AI concentration reflects the cell density. When the AI concentration exceeds a critical threshold in the cells, the AI may activate the expression of virulence-associated genes or of luminescent proteins. It has been argued that targeting the QS system puts less selective pressure on these pathogens and should avoid the development of resistant bacteria. Therefore, the molecular components of QS systems have been suggested as promising targets for developing new anti-infective compounds. Here, we review the QS systems of selected gram-negative and gram-positive bacteria, namely, Vibrio fischeri, Pseudomonas aeruginosa, and Staphylococcus aureus, and discuss various antivirulence strategies based on blocking different components of the QS machinery. PMID:26819549

  14. Quorum-Sensing of Bacteria and Its Application

    JIANG Guoliang; SU Mingxia

    2009-01-01

    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.

  15. Quorum Sensing Is Accompanied by Global Metabolic Changes in the Opportunistic Human Pathogen Pseudomonas aeruginosa

    Davenport, Peter W.; Griffin, Julian L.; Welch, Martin

    2015-01-01

    Pseudomonas aeruginosa uses N-acyl-homoserine lactone (AHL)-dependent quorum sensing (QS) systems to control the expression of secreted effectors. These effectors can be crucial to the ecological fitness of the bacterium, playing roles in nutrient acquisition, microbial competition, and virulence. In this study, we investigated the metabolic consequences of AHL-dependent QS by monitoring the metabolic profile(s) of a lasI rhlI double mutant (unable to make QS signaling molecules) and its wild...

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

    Stickler, David J.; Morris, Nicola S.; McLean, Robert J. C.; Fuqua, Clay

    1998-01-01

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

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

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

    2011-01-01

    The influence of basis of quorum sensing molecules on Proteus strains is much less known as compared to Pseudomonas or Escherichia. We have previously shown that a series of acylated homoserine lactones (acyl-HSL) does not influence the ureolytic, proteolytic, or hemolytic abilities, and that the swarming motility of Proteus mirabilis rods is strain specific. The aim of the presented study was to find out if the presence of a series of acyl-HSL influences biofilm formation of P. mirabilis lab...

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

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

    2013-01-01

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

  19. Quorum sensing Inhibitors as anti-pathogenic drugs

    Rasmussen, Thomas Bovbjerg; Givskov, Michael Christian

    Quorum-sensing (QS) signalling systems of pathogens are central regulators for the expression of virulence factors and represent highly attractive targets for the development of novel therapeutics. In Pseudomonas aeruginosa, QS systems are also involved in elevated antibiotic tolerance of biofilms...... as well as elevated tolerance to the activity of the innate immune system. Gram-negative bacteria commonly use N-acyl homoserine lactones (AHL) as QS signal molecules. The use of signal molecule based drugs to attenuate bacterial pathogenecity rather than bacterial growth is attractive for several...... (QSI) have been identified. Promising QSI compounds have been shown to make biofilms more susceptible to antimicrobial treatments, and are capable of reducing mortality and virulence as well as promoting clearance of bacteria in experimental animal models of infection....

  20. 2(5H-Furanone: a prospective strategy for biofouling-control in membrane biofilm bacteria by quorum sensing inhibition

    Kannan Ponnusamy

    2010-03-01

    Full Text Available Biofouling of membranes demands costly periodic cleaning and membrane replacement. A sustainable and environmentally friendly solution for maintenance is not available and would be of great interest for many purposes including economical. As complex biofilm formation by environmental strains is the major cause of biofouling and biofilm formation in most cases are controlled by N-Acylhomoserine lactone (AHLmediated Quorum Sensing (QS. An effort was made to understand the appropriateness of 2(5H-furanone, to use against biofouling of membranes. QS inhibition activity by 2(5H-furanone was studied using bioindicator strains and known AHLs of different acyl chain lengths. The biofilm inhibition was studied by growth analysis on polystyrene plate of Aeromonas hyrdrophila, an environmental biofilm strain isolated from a bio-fouled reverse osmosis (RO membrane. Results showed a QS inhibition activity against a wide range of AHLs and also biofilm formation by 2(5H-furanone, which is believed to act as a potential quorum inhibition agent in a bacterial biofilm community.

  1. Prediction of mixture toxicity from the hormesis of a single chemical: A case study of combinations of antibiotics and quorum-sensing inhibitors with gram-negative bacteria.

    Wang, Ting; Wang, Dali; Lin, Zhifen; An, Qingqing; Yin, Chunsheng; Huang, Qinghui

    2016-05-01

    The 50% effect level of a single chemical in the real environment is almost impossible to determine at the low exposure concentration, and the prediction of the concentration of a mixture at the 50% effect level from the concentration of a single chemical at the low effect level is even more difficult. The current literature does not address this problem. Thus, to determine solutions for this question, single/mixture chronic toxicities of sulfonamides (SAs) and quorum-sensing inhibitors (QSIs) were determined using Gram-negative bacteria (Vibrio fischeri and E. coli.) and Gram-positive bacteria (B. subtilis) as the target organisms. The results showed that the joint effects of SAs and QSIs were primarily antagonistic responses. In addition, the toxicity mechanisms of mixtures of SAs and QSIs were investigated further, and the results revealed that the chronic joint effects were primarily an antagonistic response due to the QSI competing against acyl-homoserine lactones (AHL) for luxR in V. fischeri and SdiA in E. coli generated by the SAs, leading to negative effects exerted by the QSI-luxR or QSI-SdiA complexes on luxI in V. fischeri or FtsZ in E. coli. This phenomenon eventually weakened the stimulatory effect caused by the SAs. Based on the mixture toxicity mechanism, the relationship between the mixture toxicity and the simulation effect was formulated. PMID:26901472

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

    Wu, H.; Song, Z.; Hentzer, Morten; Andersen, Jens Bo; Molin, Søren; Givskov, Michael Christian; Høiby, N.

    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 to...... lung infection by targeting bacterial quorum-sensing without directly killing bacteria or inhibiting their growth. Methods: Study I. Mice with Escherichia coli MT102 [luxR-PluxI-gfp(ASV)] lung infection were injected intravenously with N-acyl homoserine lactones with or without furanones to test the...

  3. Quorum Sensing Regulation in Aeromonas hydrophila

    Garde, Christian; Bjarnsholt, Thomas; Givskov, Michael; Jakobsen, Tim Holm; Hentzer, Morten; Claussen, Anetta; Sneppen, Kim; Ferkinghoff-Borg, Jesper; Sams, Thomas

    2010-01-01

    We present detailed results on the C4-HSL-mediated quorum sensing (QS) regulatory system of the opportunistic Gram-negative bacterium Aeromonas hydrophila. This bacterium contains a particularly simple QS system that allows for a detailed modeling of kinetics. In a model system (i.e., the...

  4. Transcriptome of the quorum-sensing signal-degrading Rhodococcus erythropolis responds differentially to virulent and avirulent Pectobacterium atrosepticum.

    Kwasiborski, A; Mondy, S; Chong, T-M; Barbey, C; Chan, K-G; Beury-Cirou, A; Latour, X; Faure, D

    2015-05-01

    Social bacteria use chemical communication to coordinate and synchronize gene expression via the quorum-sensing (QS) regulatory pathway. In Pectobacterium, a causative agent of the blackleg and soft-rot diseases on potato plants and tubers, expression of the virulence factors is collectively controlled by the QS-signals N-acylhomoserine lactones (NAHLs). Several soil bacteria, such as the actinobacterium Rhodococcus erythropolis, are able to degrade NAHLs, hence quench the chemical communication and virulence of Pectobacterium. Here, next-generation sequencing was used to investigate structural and functional genomics of the NAHL-degrading R. erythropolis strain R138. The R. erythropolis R138 genome (6.7 Mbp) contained a single circular chromosome, one linear (250 kbp) and one circular (84 kbp) plasmid. Growth of R. erythropolis and P. atrosepticum was not altered in mixed-cultures as compared with monocultures on potato tuber slices. HiSeq-transcriptomics revealed that no R. erythropolis genes were differentially expressed when R. erythropolis was cultivated in the presence vs absence of the avirulent P. atrosepticum mutant expI, which is defective for QS-signal synthesis. By contrast 50 genes (<1% of the R. erythropolis genome) were differentially expressed when R. erythropolis was cultivated in the presence vs absence of the NAHL-producing virulent P. atrosepticum. Among them, quantitative real-time reverse-transcriptase-PCR confirmed that the expression of some alkyl-sulfatase genes decreased in the presence of a virulent P. atrosepticum, as well as deprivation of organic sulfur such as methionine, which is a key precursor in the synthesis of NAHL by P. atrosepticum. PMID:25585922

  5. Prevalence of LuxR- and LuxI-type quorum sensing circuits in members of the Populus deltoides microbiome

    Schaefer, Amy L [University of Washington, Seattle; Lappala, Colin [University of Washington, Seattle; Morlen, Ryan [University of Washington, Seattle; Pelletier, Dale A [ORNL; Lu, Tse-Yuan [ORNL; Lankford, Patricia K [ORNL; Harwood, Caroline S [University of Washington, Seattle; Greenberg, E. Peter [University of Washington, Seattle

    2013-01-01

    We are interested in the root microbiome of the fast-growing Eastern cottonwood tree, Populus 25 deltoides. There is a large bank of bacterial isolates from P. deltoides and there are 44 draft 26 genomes of bacterial endophyte and rhizosphere isolates. As a first step in efforts to understand 27 the roles of bacterial communication and plant-bacterial signaling in P. deltoides we focused on 28 the prevalence of acyl-homoserine lactone (AHL) quorum sensing signal production and 29 reception in members of the P. deltoides microbiome. We screened 129 bacterial isolates for 30 AHL production using a broad-spectrum bioassay that responds to many but not all AHLs, and 31 we queried the available genome sequences of microbiome isolates for homologs of AHL 32 synthase and receptor genes. AHL signal production was detected in 40% of 129 strains tested. 33 Positive isolates included -, - and -Proteobacteria. Members of the luxI family of AHL 34 synthases were identified in 18 of 39 Proteobacteria genomes including genomes of some 35 isolates that tested negative in the bioassay. Members of the luxR family of transcription factors, 36 that include AHL-responsive factors, were more abundant than luxI homologs. There were 72 in 37 the 39 Proteobacteria genomes. Some of the luxR homologs appear to be members of a 38 subfamily of LuxRs that respond to as yet unknown plant signals rather than bacterial AHLs. 39 Apparently, there is a substantial capacity for AHL cell-to-cell communication in Proteobacteria 40 of the P. deltoides microbiota and there are also Proteobacteria with LuxR homologs of the type 41 hypothesized to respond to plant signals or cues.

  6. Characterization of quorum sensing and quorum quenching soil bacteria isolated from Malaysian tropical montane forest.

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

    2012-01-01

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

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

    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 to...... control certain bacterial infections. Furanone compounds capable of inhibiting bacterial quorum-sensing systems have been isolated from the marine macro alga Delisea pulchra. Objectives: Two synthetic furanones were tested for their ability to attenuate bacterial virulence in the mouse models of chronic...... lung infection by targeting bacterial quorum-sensing without directly killing bacteria or inhibiting their growth. Methods: Study I. Mice with Escherichia coli MT102 [luxR-PluxI-gfp(ASV)] lung infection were injected intravenously with N-acyl homoserine lactones with or without furanones to test the...

  8. A negative regulator mediates quorum-sensing control of exopolysaccharide production in Pantoea stewartii subsp. stewartii.

    von Bodman, S B; Majerczak, D R; Coplin, D L

    1998-06-23

    Classical quorum-sensing (autoinduction) regulation, as exemplified by the lux system of Vibrio fischeri, requires N-acyl homoserine lactone (AHL) signals to stimulate cognate transcriptional activators for the cell density-dependent expression of specific target gene systems. For Pantoea stewartii subsp. stewartii, a bacterial pathogen of sweet corn and maize, the extracellular polysaccharide (EPS) stewartan is a major virulence factor, and its production is controlled by quorum sensing in a population density-dependent manner. Two genes, esaI and esaR, encode essential regulatory proteins for quorum sensing. EsaI is the AHL signal synthase, and EsaR is the cognate gene regulator. esaI, DeltaesaR, and DeltaesaI-esaR mutations were constructed to establish the regulatory role of EsaR. We report here that strains containing an esaR mutation produce high levels of EPS independently of cell density and in the absence of the AHL signal. Our data indicate that quorum-sensing regulation in P. s. subsp. stewartii, in contrast to most other described systems, uses EsaR to repress EPS synthesis at low cell density, and that derepression requires micromolar amounts of AHL. In addition, derepressed esaR strains, which synthesize EPS constitutively at low cell densities, were significantly less virulent than the wild-type parent. This finding suggests that quorum sensing in P. s. subsp. stewartii may be a mechanism to delay the expression of EPS during the early stages of infection so that it does not interfere with other mechanisms of pathogenesis. PMID:9636211

  9. Detection of Quorum Sensing Signals in Gram-Negative Bacteria by Using Reporter Strain CV026

    Ahmad Humayan KABIR

    2010-12-01

    Full Text Available Quorum sensing signals are referred to as acylated homoserine lactones (AHL that are mainly found in Gram-negative bacteria. It implies the ability of certain bacteria of producing different AHL molecules. The bacteria Pseudomonas aureofaciens and Xenorhabdus nematophila were cultured in Luria-Bertani (LB10 media and CV026 was used as a reporter strain to detect the presence of AHLs produced by the cultured bacteria. In this study, the reporter strain has revealed the quorum sensing ability of P. aureofaciens and X. nematophila by producing the purple pigment violacein in the supply of external AHLs molecules. Thin layer chromatography (TLC bioassay having four controls was conducted to detect specific AHL molecule supplied by P. aureofaciens and X. nematophila. The specific AHL molecule was observed to be migrated according to their polarity on the TLC plate.

  10. Role of quorum sensing in bacterial infections

    Castillo-Juárez, Israel; Maeda, Toshinari; Mandujano-Tinoco, Edna Ayerim; Tomás, María; Pérez-Eretza, Berenice; García-Contreras, Silvia Julieta; Wood, Thomas K.; García-Contreras, Rodolfo

    2015-01-01

    Quorum sensing (QS) is cell communication that is widely used by bacterial pathogens to coordinate the expression of several collective traits, including the production of multiple virulence factors, biofilm formation, and swarming motility once a population threshold is reached. Several lines of evidence indicate that QS enhances virulence of bacterial pathogens in animal models as well as in human infections; however, its relative importance for bacterial pathogenesis is still incomplete. I...

  11. Characterization of quorum sensing signals in coral-associated bacteria.

    Golberg, Karina; Eltzov, Evgeni; Shnit-Orland, Maya; Marks, Robert S; Kushmaro, Ariel

    2011-05-01

    Marine environment habitats, such as the coral mucus layer, are abundant in nutrients and rich with diverse populations of microorganisms. Since interactions among microorganisms found in coral mucus can be either mutualistic or competitive, understanding quorum sensing-based acyl homoserine lactone (AHL) language may shed light on the interaction between coral-associated microbial communities in the native host. More than 100 bacterial isolates obtained from different coral species were screened for their ability to produce AHL. When screening the isolated coral bacteria for AHL induction activity using the reporter strains Escherichia coli K802NR-pSB1075 and Agrobacterium tumefaciens KYC55, we found that approximately 30% of the isolates tested positive. Thin layer chromatography separation of supernatant extracts revealed different AHL profiles, with detection of at least one active compound in the supernatant of those bacterial extracts being able to induce AHL activity in the two different bioreporter strains. The active extract of bacterial isolate 3AT 1-10-4 was subjected to further analysis by preparative thin layer chromatography and liquid chromatography tandem mass spectrometry. One of the compounds was found to correspond with N-(3-hydroxydecanoyl)-L-homoserine lactone. 16S rRNA gene sequencing of the isolates with positive AHL activity affiliated them with the Vibrio genus. Understanding the ecological role of AHL in the coral environment and its regulatory circuits in the coral holobiont-associated microbial community will further expand our knowledge of such interactions. PMID:21523464

  12. Tandem Mass Spectrometry Detection of Quorum Sensing Activity in Multidrug Resistant Clinical Isolate Acinetobacter baumannii

    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.

  13. The Pseudomonas aeruginosa autoinducer dodecanoyl-homoserine lactone inhibits the putrescine synthesis in human cells

    Kristiansen, S.; Bjarnsholt, Thomas; Adeltoft, D.;

    2008-01-01

    Pseudomonas aeruginosa uses acyl-homoserine lactones to coordinate gene transcription in a process called quorum sensing (QS). The QS molecules C-4-HSL and C-12-oxo-HSL are synthesized from the universal precursor S-adenosyl methionine, which is also a precursor of polyamines in human cells....... Polyamines are required for mitotic cell division and peak during this phase. The polyamine putrescine is synthesized by ornithine decarboxylase (ODC) as a rate-limiting step. The ODC enzyme concentration also peaks during the mitotic phase. This peak is mediated by translation of ODC mRNA by the ITAF45...... protein, which translocates from the nuclear compartment to the cytoplasm in a phosphorylation-dependent manner. We observed that C-12-HSL-treated human epidermal cells had a higher cytoplasm-to-nuclear ITAF45 protein concentration and this translocation was dependent on the dephosphorylation of ITAF45...

  14. Ambroxol interferes with Pseudomonas aeruginosa quorum sensing.

    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. PMID:20580207

  15. Fremmedlegemeinfektioner--nyt om biofilm og quorum sensing

    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...

  16. Quorum Sensing Enhances the Stress Response in Vibrio cholerae▿

    Joelsson, Adam; Kan, Biao; Jun ZHU

    2007-01-01

    Vibrio cholerae lives in aquatic environments and causes cholera. Here, we show that quorum sensing enhances V. cholerae viability under certain stress conditions by upregulating the expression of RpoS, and this regulation acts through HapR, suggesting that a quorum-sensing-enhanced stress response plays a role in V. cholerae environmental survival.

  17. Targeting quorum sensing in Pseudomonas aeruginosa biofilms

    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...... 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...

  18. Bacterial biofilms. Bacteria Quorum sensing in biofilms

    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.

  19. GABA controls the level of quorum-sensing signal in Agrobacterium tumefaciens

    Chevrot, Romain; Rosen, Ran; Haudecoeur, Elise; Cirou, Amélie; Shelp, Barry J.; Ron, Eliora; Faure, Denis

    2006-01-01

    The concentration of GABA increases rapidly in wounded plant tissues, but the implication of this GABA pulse for plant–bacteria interactions is not known. Here we reveal that GABA stimulated the inactivation of the N-(3-oxooctanoyl)homoserine lactone (OC8-HSL) quorum-sensing signal (or “quormone”) by the Agrobacterium lactonase AttM. GABA induced the expression of the attKLM operon, which was correlated to a decrease in OC8-HSL concentration in Agrobacterium tumefaciens cultures. The Agrobact...

  20. Quorum Sensing Regulation of Adhesion in Serratia Marcescens MG1 is surface dependent

    Labbate, M.; Zhu, H.; Thung, L.;

    2007-01-01

    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 in ...... and the outer membrane protein OmpX. We concluded that S. marcescens MG1 utilizes different regulatory systems and adhesins in attachment to biotic and abiotic surfaces and that QS is a main regulatory pathway in adhesion to an abiotic surface but not in adhesion to a biotic surface....

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

    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.

  2. In vitro screens for quorum sensing inhibitors and in vivo confirmation of their effect

    Bjarnsholt, Thomas; van Gennip, Maria; Jakobsen, Tim H;

    2010-01-01

    aim of disabling the expression of virulence and reduction of antibiotic tolerance. Here we present protocols for screening and testing for acyl-homoserine lactone (AHL)-dependent QS inhibition. We also present protocols for the in vivo validation of QSIs as possible drug candidates. The presented...

  3. Croceicoccus naphthovorans sp. nov., a polycyclic aromatic hydrocarbons-degrading and acylhomoserine-lactone-producing bacterium isolated from marine biofilm, and emended description of the genus Croceicoccus.

    Huang, Yili; Zeng, Yanhua; Feng, Hao; Wu, Yuehong; Xu, Xuewei

    2015-05-01

    A polycyclic aromatic hydrocarbons-degrading and acylhomoserine-lactone-producing marine bacterium, designated strain PQ-2(T), was isolated from marine biofilm collected from a boat shell at a harbour of Zhoushan island in Zhejiang Province, PR China. Strain PQ-2(T) is Gram-stain-negative, yellow-pigmented, non-motile and short rod-shaped. Optimal growth of strain PQ-2(T) was observed at 32 °C, at pH 7.0 and in 2% (w/v) NaCl. The 16S rRNA gene sequence of strain PQ-2(T) showed highest similarity to Croceicoccus marinus E4A9(T) (96.3%) followed by Novosphingobium malaysiense MUSC 273(T) (95.6%) and Altererythrobacter marinus H32(T) (95.6%). Phylogenetic analysis with all species of the family Erythrobacteraceae with validly published names revealed that strain PQ-2(T) formed a phyletic line with Croceicoccus marinus E4A9(T) that was distinct from other members of the family Erythrobacteraceae . The sole respiratory quinone was ubiquinone 10 (Q-10). The predominant fatty acids were C18 : 1ω7c, C17 : 1ω6c and summed feature 3 (C16 : 1ω7c and/or iso-C15 : 0 2-OH). The genomic DNA G+C content was 61.7 mol%. In the polar lipid profile, phosphatidylethanolamine, phosphatidylcholine, phosphatidylglycerol, one unidentified phospholipid and one sphingoglycolipid were the major compounds; and another sphingoglycolipid was present in a minor amount. Based on the genotypic and phenotypic data, strain PQ-2(T) represents a novel species of the genus Croceicoccus , for which the name Croceicoccus naphthovorans sp. nov. is proposed. The type strain is PQ-2(T) ( =CGMCC 1.12805(T) =NBRC 110381(T)). In addition, emended descriptions for the genus Croceicoccus and the species C. marinus are given. PMID:25713040

  4. Zingerone silences quorum sensing and attenuates virulence of Pseudomonas aeruginosa.

    Kumar, Lokender; Chhibber, Sanjay; Kumar, Rajnish; Kumar, Manoj; Harjai, Kusum

    2015-04-01

    Quorum sensing in Pseudomonas aeruginosa plays an imperative role in virulence factor, biofilm formation and antimicrobial resistance. Blocking quorum sensing pathways are viewed as viable anti-virulent therapy in association with traditional antimicrobial therapy. Anti-quorum sensing dietary phytochemicals with may prove to be a safe and viable choice as anti-virulent drug candidates. Previously, our lab proved zingerone as potent anti-biofilm agent hence; further its anti-virulent and anti-quorum activities were evaluated. Zingerone, besides decreasing swimming, swarming and twitching phenotypes of P. aeruginosa PAO1, reduced biofilm forming capacity and production of virulence factors including rhamnolipid, elastase, protease, pyocyanin, cell free and cell bound hemolysin (pproduction of quorum sensing signal molecules by clinical isolates of P. aeruginosa but also showed significant interference with the activation of QS reporter strains. To study the mechanism of blocking quorum sensing cascade, in silico analysis was carried out. Anti-QS activity was attributed to interference with the ligand receptor interaction of zingerone with QS receptors (TraR, LasR, RhlR and PqsR). Zingerone showed a good comparative docking score to respective autoinducer molecules which was even higher than that of vanillin, a proven anti-quorum sensing phytochemical. The results of the present study revealed the anti-quorum sensing activity of zingerone targeting ligand-receptor interaction, hence proposing zingerone as a suitable anti-virulent drug candidate against P. aeruginosa infections. PMID:25704369

  5. Social Evolution Selects for Redundancy in Bacterial Quorum Sensing.

    Even-Tov, Eran; Omer Bendori, Shira; Valastyan, Julie; Ke, Xiaobo; Pollak, Shaul; Bareia, Tasneem; Ben-Zion, Ishay; Bassler, Bonnie L; Eldar, Avigdor

    2016-02-01

    Quorum sensing is a process of chemical communication that bacteria use to monitor cell density and coordinate cooperative behaviors. Quorum sensing relies on extracellular signal molecules and cognate receptor pairs. While a single quorum-sensing system is sufficient to probe cell density, bacteria frequently use multiple quorum-sensing systems to regulate the same cooperative behaviors. The potential benefits of these redundant network structures are not clear. Here, we combine modeling and experimental analyses of the Bacillus subtilis and Vibrio harveyi quorum-sensing networks to show that accumulation of multiple quorum-sensing systems may be driven by a facultative cheating mechanism. We demonstrate that a strain that has acquired an additional quorum-sensing system can exploit its ancestor that possesses one fewer system, but nonetheless, resume full cooperation with its kin when it is fixed in the population. We identify the molecular network design criteria required for this advantage. Our results suggest that increased complexity in bacterial social signaling circuits can evolve without providing an adaptive advantage in a clonal population. PMID:26927849

  6. Functional Characterization of the Quorum Sensing Regulator RsaL in the Plant-Beneficial Strain Pseudomonas putida WCS358

    Rampioni, Giordano; Bertani, Iris; Pillai, Cejoice Ramachandran; Venturi, Vittorio; Zennaro, Elisabetta; Leoni, Livia

    2012-01-01

    In many bacteria, quorum sensing (QS) systems rely on a signal receptor and a synthase producing N-acyl-homoserine lactone(s) as the signal molecule(s). In some species, the rsaL gene, located between the signal receptor and synthase genes, encodes a repressor limiting signal synthase expression and hence signal molecule production. Here we investigate the molecular mechanism of action of the RsaL protein in the plant growth-promoting rhizobacterium Pseudomonas putida WCS358 (RsaLWCS). In P. ...

  7. Sub-MICs of Mentha piperita essential oil and menthol inhibits AHL mediated quorum sensing and biofilm of Gram negative bacteria

    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.

  8. Quorum sensing in plant-pathogenic bacteria.

    Von Bodman, Susanne B; Bauer, W Dietz; Coplin, David L

    2003-01-01

    Quorum sensing (QS) allows bacteria to assess their local population density and/or physical confinement via the secretion and detection of small, diffusible signal molecules. This review describes how phytopathogenic bacteria have incorporated QS mechanisms into complex regulatory cascades that control genes for pathogenicity and colonization of host surfaces. Traits regulated by QS include the production of extracellular polysaccharides, degradative enzymes, antibiotics, siderophores, and pigments, as well as Hrp protein secretion, Ti plasmid transfer, motility, biofilm formation, and epiphytic fitness. Since QS regulatory systems are often required for pathogenesis, interference with QS signaling may offer a means of controlling bacterial diseases of plants. Several bacterial pathogens of plants that have been intensively studied and have revealed information of both fundamental and practical importance are reviewed here: Agrobacterium tumefaciens, Pantoea stewartii, Erwinia carotovora, Ralstonia solanacearum, Pseudomonas syringae, Pseudomonas aeruginosa, and Xanthomonas campestris. PMID:12730390

  9. Novel Pseudomonas aeruginosa Quorum-Sensing Inhibitors Identified in an Ultra-High-Throughput Screen▿ †

    Müh, Ute; Schuster, Martin; Heim, Roger; Singh, Ashvani; Olson, Eric R.; Greenberg, E. Peter

    2006-01-01

    The opportunistic pathogen Pseudomonas aeruginosa has two complete acyl-homoserine lactone (acyl-HSL) signaling systems, LasR-LasI and RhlR-RhlI. LasI catalyzes the synthesis of N-3-oxododecanoyl homoserine lactone (3OC12-HSL), and LasR is a transcription factor that requires 3OC12-HSL as a ligand. RhlI catalyzes the synthesis of N-butanoyl homoserine lactone (C4), and RhlR is a transcription factor that responds to C4. LasR and RhlR control the transcription of hundreds of P. aeruginosa gene...

  10. Quorum sensing regulates the osmotic stress response in Vibrio harveyi.

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

    2015-01-01

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

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

    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...... challenge experiments, thus avoiding selection for resistance. To elucidate the mechanism of disease control by furanone C-30, we determined its effect on the bacterial proteome, motility, and respiration. No effects were seen of furanone C-30 in any of these experiments. Although no cytotoxic effect on He...

  12. Mathematical Modelling of Quorum Sensing and Bioluminescence in Bacteria

    Sarangam Majumdar

    2012-09-01

    Full Text Available Different types of Quorum Sensing in Bacteria, both intra-species and inter-species, have been analyzed over the last decade. A number of Mathematical Models has been proposed to explain the process of Quorum Sensing which depends on a threshold concentration of autoinducers (or QSM reflecting high bacterial density. Stability of the solution of the differential equations of such an intra-species model for Vibrio fischeri is discussed in this paper.

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

    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.

  14. Role of quorum sensing in bacterial infections.

    Castillo-Juárez, Israel; Maeda, Toshinari; Mandujano-Tinoco, Edna Ayerim; Tomás, María; Pérez-Eretza, Berenice; García-Contreras, Silvia Julieta; Wood, Thomas K; García-Contreras, Rodolfo

    2015-07-16

    Quorum sensing (QS) is cell communication that is widely used by bacterial pathogens to coordinate the expression of several collective traits, including the production of multiple virulence factors, biofilm formation, and swarming motility once a population threshold is reached. Several lines of evidence indicate that QS enhances virulence of bacterial pathogens in animal models as well as in human infections; however, its relative importance for bacterial pathogenesis is still incomplete. In this review, we discuss the present evidence from in vitro and in vivo experiments in animal models, as well as from clinical studies, that link QS systems with human infections. We focus on two major QS bacterial models, the opportunistic Gram negative bacteria Pseudomonas aeruginosa and the Gram positive Staphylococcus aureus, which are also two of the main agents responsible of nosocomial and wound infections. In addition, QS communication systems in other bacterial, eukaryotic pathogens, and even immune and cancer cells are also reviewed, and finally, the new approaches proposed to combat bacterial infections by the attenuation of their QS communication systems and virulence are also discussed. PMID:26244150

  15. Quorum sensing regulation in Aeromonas hydrophila.

    Garde, Christian; Bjarnsholt, Thomas; Givskov, Michael; Jakobsen, Tim Holm; Hentzer, Morten; Claussen, Anetta; Sneppen, Kim; Ferkinghoff-Borg, Jesper; Sams, Thomas

    2010-03-01

    We present detailed results on the C4-HSL-mediated quorum sensing (QS) regulatory system of the opportunistic Gram-negative bacterium Aeromonas hydrophila. This bacterium contains a particularly simple QS system that allows for a detailed modeling of kinetics. In a model system (i.e., the Escherichia coli monitor strain MH205), the C4-HSL production of A. hydrophila is interrupted by fusion of gfp(ASV). In the present in vitro study, we measure the response of the QS regulatory ahyRI locus in the monitor strain to predetermined concentrations of C4-HSL signal molecules. A minimal kinetic model describes the data well. It can be solved analytically, providing substantial insight into the QS mechanism: at high concentrations of signal molecules, a slow decay of the activated regulator sets the timescale for the QS regulation loop. Slow saturation ensures that, in an A. hydrophila cell, the QS system is activated only by signal molecules produced by other A. hydrophila cells. Separate information on the ahyR and ahyI loci can be extracted, thus allowing the probe to be used in identifying the target when testing QS inhibitors. PMID:20064524

  16. Quorum Sensing Inhibition and Structure-Activity Relationships of β-Keto Esters.

    Forschner-Dancause, Stephanie; Poulin, Emily; Meschwitz, Susan

    2016-01-01

    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. PMID:27463706

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

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

    2015-01-01

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

  18. Quorum Sensing Inhibition and Structure–Activity Relationships of β-Keto Esters

    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.

  19. IMPACT OF BACTERIAL QUORUM SENSING SYSTEM ON CHANGES OF ORGANOLEPTIC MARKERS OF STORAGE CABBAGE

    Kamila Myszka

    2015-04-01

    Full Text Available The regulation of phenotypes of vegetable-associated bacteria can be mediated through the production of acylated homoserine lactones (AHLs. This knowledge is essential for successful control of bacterial diseases of vegetable. The purpose of these investigations was to define the AHL patterns of gram-negative bacteria presented in storage cabbage by LC/MS technique. The phenomenon of regulating the pectinolytic activity and the exopolysaccharide (EPS production by AHLs that are associated with microbial spoilage of cabbage was also examined. Among 100 strains isolated from storage cabbage, 47 isolates produced AHLs. The results of the 16S rDNA sequence analysis indicated that selected microflora was highly closely related to Pantoea agglomerans, Rahnella aquatilis, Pseudomonas fluorescens, Pseudomonas syringae, and Pseudomonas cedrina (approximately 98%-99% confidence. The chemical nature of AHLs produced by selected microflora differ from species to species. The pattern of AHLs of Ps. cedrina consisting of C8-HSL, 3-oxo-C10-HSL, and 3-hydroxy-C14-HSL, has not been previously reported. The present study demonstrates that bacterial spoilage of storage cabbage is influenced by quorum sensing. Application of furanone C-30 that acts as quorum sensing inhibitor, caused the significant reduction in the production of EPS and pectinolytic enzymes by examined bacteria.

  20. Quorum Sensing in the Squid-Vibrio Symbiosis

    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.

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

    Høyland-Kroghsbo, Nina Molin

    behavior genes. Quorum sensing controls important bacterial behaviors, including bioluminescence, biofilm formation, and virulence. Inter- and intraspecies quorum sensing signals enable bacteria to estimate the abundance and species complexity of a microbial community. A long standing question...

  2. Panax ginseng has anti-infective activity against opportunistic pathogen Pseudomonas aeruginosa by inhibiting quorum sensing, a bacterial communication process critical for establishing infection

    Song, Z.; Kong, K.F; Wu, H; Maricic, N.; Ramalingam, B.; Priestap, H.; Quirke, J.M.E.; Høiby, N.; Mathee, K

    2010-01-01

    Virulent factors produced by pathogens play an important role in the infectious process, which is regulated by a cell-to-cell communication mechanism called quorum sensing (QS). Pseudomonas aeruginosa is an important opportunistic human pathogen, which causes infections in patients with compromised immune systems and cystic fibrosis. The QS systems of P. aeruginosa use N-acylated homoserine lactone (AHL) as signal molecules. Previously we have demonstrated that Panax ginseng treatment allowed...

  3. Structure/Function Analysis of the Pantoea stewartii Quorum-Sensing Regulator EsaR as an Activator of Transcription▿

    Daniel J Schu; Carlier, Aurelien L; Jamison, Katherine P.; von Bodman, Susanne; Stevens, Ann M.

    2009-01-01

    In Pantoea stewartii subsp. stewartii, two regulatory proteins are key to the process of cell-cell communication known as quorum sensing: the LuxI and LuxR homologues EsaI and EsaR. Most LuxR homologues function as activators of transcription in the presence of their cognate acylated homoserine lactone (AHL) signal. However, EsaR was initially found to function as a repressor in the absence of AHL. Previous studies demonstrated that, in the absence of AHL, EsaR retains the ability to function...

  4. The Quorum-Sensing Negative Regulator RsaL of Pseudomonas aeruginosa Binds to the lasI Promoter

    Rampioni, Giordano; Bertani, Iris; Zennaro, Elisabetta; Polticelli, Fabio; Venturi, Vittorio; Leoni, Livia

    2006-01-01

    A mutation in the rsaL gene of Pseudomonas aeruginosa produces dramatically higher amounts of N-acyl homoserine lactone with respect to the wild type, highlighting the key role of this negative regulator in controlling quorum sensing (QS) in this opportunistic pathogen. The DNA binding site of the RsaL protein on the rsaL-lasI bidirectional promoter partially overlaps the binding site of the LasR protein, consistent with the hypothesis that RsaL and LasR could be in binding competition on thi...

  5. The Evolution of Quorum Sensing as a Mechanism to Infer Kinship

    Schluter, Jonas; Schoech, Armin P.; Foster, Kevin R.; Mitri, Sara

    2016-01-01

    Bacteria regulate many phenotypes via quorum sensing systems. Quorum sensing is typically thought to evolve because the regulated cooperative phenotypes are only beneficial at certain cell densities. However, quorum sensing systems are also threatened by non-cooperative “cheaters” that may exploit quorum-sensing regulated cooperation, which begs the question of how quorum sensing systems are maintained in nature. Here we study the evolution of quorum sensing using an individual-based model that captures the natural ecology and population structuring of microbial communities. We first recapitulate the two existing observations on quorum sensing evolution: density-dependent benefits favor quorum sensing but competition and cheating will destabilize it. We then model quorum sensing in a dense community like a biofilm, which reveals a novel benefit to quorum sensing that is intrinsically evolutionarily stable. In these communities, competing microbial genotypes gradually segregate over time leading to positive correlation between density and genetic similarity between neighboring cells (relatedness). This enables quorum sensing to track genetic relatedness and ensures that costly cooperative traits are only activated once a cell is safely surrounded by clonemates. We hypothesize that under similar natural conditions, the benefits of quorum sensing will not result from an assessment of density but from the ability to infer kinship. PMID:27120081

  6. The Evolution of Quorum Sensing as a Mechanism to Infer Kinship.

    Schluter, Jonas; Schoech, Armin P; Foster, Kevin R; Mitri, Sara

    2016-04-01

    Bacteria regulate many phenotypes via quorum sensing systems. Quorum sensing is typically thought to evolve because the regulated cooperative phenotypes are only beneficial at certain cell densities. However, quorum sensing systems are also threatened by non-cooperative "cheaters" that may exploit quorum-sensing regulated cooperation, which begs the question of how quorum sensing systems are maintained in nature. Here we study the evolution of quorum sensing using an individual-based model that captures the natural ecology and population structuring of microbial communities. We first recapitulate the two existing observations on quorum sensing evolution: density-dependent benefits favor quorum sensing but competition and cheating will destabilize it. We then model quorum sensing in a dense community like a biofilm, which reveals a novel benefit to quorum sensing that is intrinsically evolutionarily stable. In these communities, competing microbial genotypes gradually segregate over time leading to positive correlation between density and genetic similarity between neighboring cells (relatedness). This enables quorum sensing to track genetic relatedness and ensures that costly cooperative traits are only activated once a cell is safely surrounded by clonemates. We hypothesize that under similar natural conditions, the benefits of quorum sensing will not result from an assessment of density but from the ability to infer kinship. PMID:27120081

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

    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...

  8. [Research progress of new antibacterial drugs that target bacterial quorum sensing systems].

    Yin, Shou-Liang; Chang, Ya-Jing; Deng, Su-Ping; Wang, Qing-Chi; Yu, Wen-Gong; Gong, Qian-Hong

    2011-06-01

    In recent years, antibiotic resistance of bacteria has become a global health crisis. Especially, the new class of "superbug" was found in South Asia, which is resistant to almost known antibiotics and causes worldwide alarm. Through the underlying mechanisms of bacterial pathogenecity, the expression of many pathogen virulence factors is regulated by the process of quorum sensing. Screening efficient quorum sensing inhibitors is an especially compelling approach to the future treatment of bacterial infections and antibiotic resistance. This article focuses on bacterial quorum sensing system, quorum sensing screening model for in vitro and evaluation of animal models in vivo, recent research of quorum sensing inhibitors and so on. PMID:21882519

  9. Attenuation of Pseudomonas aeruginosa virulence by quorum sensing inhibitors

    Hentzer, Morten; Wu, H.; Andersen, Jens Bo; Riedel, K.; Rasmussen, Thomas Bovbjerg; Bagge, N.; Kumar, N.; Schembri, Mark; Song, Z.J.; Kristoffersen, Peter; Manefield, M.; Costerton, J.W.; Molin, Søren; Eberl, Leo; Steinberg, P.; Kjelleberg, S.; Høiby, N.; Givskov, Michael Christian

    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 h...

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

    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

  11. Enterobacter asburiae Strain L1: Complete Genome and Whole Genome Optical Mapping Analysis of a Quorum Sensing Bacterium

    Yin Yin Lau

    2014-07-01

    Full Text Available Enterobacter asburiae L1 is a quorum sensing bacterium isolated from lettuce leaves. In this study, for the first time, the complete genome of E. asburiae L1 was sequenced using the single molecule real time sequencer (PacBio RSII and the whole genome sequence was verified by using optical genome mapping (OpGen technology. In our previous study, E. asburiae L1 has been reported to produce AHLs, suggesting the possibility of virulence factor regulation which is quorum sensing dependent. This evoked our interest to study the genome of this bacterium and here we present the complete genome of E. asburiae L1, which carries the virulence factor gene virK, the N-acyl homoserine lactone-based QS transcriptional regulator gene luxR and the N-acyl homoserine lactone synthase gene which we firstly named easI. The availability of the whole genome sequence of E. asburiae L1 will pave the way for the study of the QS-mediated gene expression in this bacterium. Hence, the importance and functions of these signaling molecules can be further studied in the hope of elucidating the mechanisms of QS-regulation in E. asburiae. To the best of our knowledge, this is the first documentation of both a complete genome sequence and the establishment of the molecular basis of QS properties of E. asburiae.

  12. Enterobacter asburiae strain L1: complete genome and whole genome optical mapping analysis of a quorum sensing bacterium.

    Lau, Yin Yin; Yin, Wai-Fong; Chan, Kok-Gan

    2014-01-01

    Enterobacter asburiae L1 is a quorum sensing bacterium isolated from lettuce leaves. In this study, for the first time, the complete genome of E. asburiae L1 was sequenced using the single molecule real time sequencer (PacBio RSII) and the whole genome sequence was verified by using optical genome mapping (OpGen) technology. In our previous study, E. asburiae L1 has been reported to produce AHLs, suggesting the possibility of virulence factor regulation which is quorum sensing dependent. This evoked our interest to study the genome of this bacterium and here we present the complete genome of E. asburiae L1, which carries the virulence factor gene virK, the N-acyl homoserine lactone-based QS transcriptional regulator gene luxR and the N-acyl homoserine lactone synthase gene which we firstly named easI. The availability of the whole genome sequence of E. asburiae L1 will pave the way for the study of the QS-mediated gene expression in this bacterium. Hence, the importance and functions of these signaling molecules can be further studied in the hope of elucidating the mechanisms of QS-regulation in E. asburiae. To the best of our knowledge, this is the first documentation of both a complete genome sequence and the establishment of the molecular basis of QS properties of E. asburiae. PMID:25196111

  13. The hydrocarbon-degrading marine bacterium Cobetia sp. strain MM1IDA2H-1 produces a biosurfactant that interferes with quorum sensing of fish pathogens by signal hijacking.

    Ibacache-Quiroga, C; Ojeda, J; Espinoza-Vergara, G; Olivero, P; Cuellar, M; Dinamarca, M A

    2013-07-01

    Biosurfactants are produced by hydrocarbon-degrading marine bacteria in response to the presence of water-insoluble hydrocarbons. This is believed to facilitate the uptake of hydrocarbons by bacteria. However, these diffusible amphiphilic surface-active molecules are involved in several other biological functions such as microbial competition and intra- or inter-species communication. We report the isolation and characterization of a marine bacterial strain identified as Cobetia sp. MM1IDA2H-1, which can grow using the sulfur-containing heterocyclic aromatic hydrocarbon dibenzothiophene (DBT). As with DBT, when the isolated strain is grown in the presence of a microbial competitor, it produces a biosurfactant. Because the obtained biosurfactant was formed by hydroxy fatty acids and extracellular lipidic structures were observed during bacterial growth, we investigated whether the biosurfactant at its critical micelle concentration can interfere with bacterial communication systems such as quorum sensing. We focused on Aeromonas salmonicida subsp. salmonicida, a fish pathogen whose virulence relies on quorum sensing signals. Using biosensors for quorum sensing based on Chromobacterium violaceum and Vibrio anguillarum, we showed that when the purified biosurfactant was mixed with N-acyl homoserine lactones produced by A. salmonicida, quorum sensing was inhibited, although bacterial growth was not affected. In addition, the transcriptional activities of A. salmonicida virulence genes that are controlled by quorum sensing were repressed by both the purified biosurfactant and the growth in the presence of Cobetia sp. MM1IDA2H-1. We propose that the biosurfactant, or the lipid structures interact with the N-acyl homoserine lactones, inhibiting their function. This could be used as a strategy to interfere with the quorum sensing systems of bacterial fish pathogens, which represents an attractive alternative to classical antimicrobial therapies in fish aquaculture. PMID

  14. Ellagic acid derivatives from Terminalia chebula Retz. downregulate the expression of quorum sensing genes to attenuate Pseudomonas aeruginosa PAO1 virulence.

    Sajal Sarabhai

    Full Text Available BACKGROUND: Burgeoning antibiotic resistance in Pseudomonas aeruginosa has necessitated the development of anti pathogenic agents that can quench acylhomoserine lactone (AHL mediated QS with least risk of resistance. This study explores the anti quorum sensing potential of T. chebula Retz. and identification of probable compounds(s showing anti QS activity and the mechanism of attenuation of P. aeruginosa PAO1 virulence factors. METHODS AND RESULTS: Methanol extract of T. chebula Retz. fruit showed anti QS activity using Agrobacterium tumefaciens A136. Bioactive fraction (F7, obtained by fractionation of methanol extract using Sephadex LH20, showed significant reduction (p<0.001 in QS regulated production of extracellular virulence factors in P. aeruginosa PAO1. Biofilm formation and alginate were significantly (p<0.05 reduced with enhanced (20% susceptibility to tobramycin. Real Time PCR of F7 treated P. aeruginosa showed down regulation of autoinducer synthase (lasI and rhlI and their cognate receptor (lasR and rhlR genes by 89, 90, 90 and 93%, respectively. Electrospray Ionization Mass Spectrometry also showed 90 and 64% reduction in the production of 3-oxo-C(12HSL and C(4HSL after treatment. Decrease in AHLs as one of the mechanisms of quorum quenching by F7 was supported by the reversal of inhibited swarming motility in F7-treated P. aeruginosa PAO1 on addition of C(4HSL. F7 also showed antagonistic activity against 3-oxo-C(12HSL-dependent QS in E. coli bioreporter. C. elegans fed on F7-treated P. aeruginosa showed enhanced survival with LT50 increasing from 24 to 72 h. LC-ESI-MS of F7 revealed the presence of ellagic acid derivatives responsible for anti QS activity in T. chebula extract. CONCLUSIONS: This is the first report on anti QS activity of T. chebula fruit linked to EADs which down regulate the expression of lasIR and rhlIR genes with concomitant decrease in AHLs in P. aeruginosa PAO1 causing attenuation of its virulence factors

  15. Quorum-sensing in yeast and its potential in wine making.

    Avbelj, Martina; Zupan, Jure; Raspor, Peter

    2016-09-01

    This mini-review synthesises the present knowledge of microbial quorum-sensing, with a specific focus on quorum-sensing in yeast, and especially in wine yeast. In vine and wine ecosystems, yeast co-interact with a large variety of microorganisms, thereby affecting the fermentation process and, consequently, the flavour of the wine. The precise connections between microbial interactions and quorum-sensing remain unclear, but we describe here how and when some species start to produce quorum-sensing molecules to synchronously adapt their collective behaviour to new conditions. In Saccharomyces cerevisiae, the quorum-sensing molecules were identified as 2-phenylethanol and tryptophol. However, it was recently shown that also a quorum-sensing molecule formerly identified only in Candida albicans, tyrosol, appears to be regulated in S. cerevisiae according to cell density. This review describes the methods for detection and quantification of those quorum-sensing molecules, their underlying mechanisms of action, and their genetic background. It also examines the external stimuli that evoke the quorum-sensing mechanism in the wine-processing environment. The review closes with insight into the biotechnological applications that are already making use of the advantages of quorum-sensing systems and indicates the important questions that still need to be addressed in future research into quorum-sensing. PMID:27507587

  16. In vitro anti-quorum sensing activity of phytol.

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

    2015-01-01

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

  17. Attenuation of Pseudomonas aeruginosa virulence by quorum sensing inhibitors

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

    2003-01-01

    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 of...... systems 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......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...

  18. Improved quorum sensing capacity by culturing Vibrio harveyi in microcapsules.

    Gao, Meng; Song, Huiyi; Liu, Xiudong; Yu, Weiting; Ma, Xiaojun

    2016-04-01

    Microcapsule entrapped low density cells with culture (ELDCwc), different from free cell culture, conferred stronger stress resistance and improved cell viability of microorganisms. In this paper, the quorum sensing (QS) system of Vibrio harveyi was used to investigate changes when cells were cultured in microcapsules. Cells in ELDCwc group grew into cell aggregates, which facilitated cell-cell communication and led to increased bioluminescence intensity. Moreover, the luxS-AI-2 system, a well-studied QS signal pathway, was detected as both luxS gene and the AI-2 signaling molecule, and the results were analyzed with respect to QS capacity of unit cell. The V. harveyi of ELDCwc also showed higher relative gene expression and stronger quorum sensing capacity when compared with free cells. In conclusion, the confined microcapsule space can promote the cell aggregates formation, reduce cell-cell communication distance and increase local concentration of signal molecule, which are beneficial to bacterial QS. PMID:26364746

  19. Biomimicry of quorum sensing using bacterial lifecycle model

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

    2013-01-01

    Background Recent microbiologic studies have shown that quorum sensing mechanisms, which serve as one of the fundamental requirements for bacterial survival, exist widely in bacterial intra- and inter-species cell-cell communication. Many simulation models, inspired by the social behavior of natural organisms, are presented to provide new approaches for solving realistic optimization problems. Most of these simulation models follow population-based modelling approaches, where all the individu...

  20. Quorum-sensing and cheating in bacterial biofilms

    Popat, Roman; Shanika A. Crusz; Messina, Marco; Willams, Paul; West, Stuart A.; Diggle, Stephen P.

    2012-01-01

    The idea from human societies that self-interest can lead to a breakdown of cooperation at the group level is sometimes termed the public goods dilemma. We tested this idea in the opportunistic bacterial pathogen, Pseudomonas aeruginosa, by examining the influence of putative cheats that do not cooperate via cell-to-cell signalling (quorum-sensing, QS). We found that: (i) QS cheating occurs in biofilm populations owing to exploitation of QS-regulated public goods; (ii) the thickness and densi...

  1. Synergistic activation of quorum sensing in Vibrio harveyi.

    Mandabi, Aviad; Ganin, Hadas; Meijler, Michael M

    2015-09-15

    Autoinducer-2 (AI-2) has been suggested to serve as a ubiquitous quorum sensing (QS) signal that mediates intra- and interspecies cross-talk between bacteria. To add tools for the study of its function in bacterial communication, we present a new and an improved synthetic route to AI-2 and aromatic analogues. We used this strategy to prepare naphthyl-DPD, and observed remarkably high synergistic activity at low nanomolar concentrations for this analogue in Vibrio harveyi. PMID:26248803

  2. Presence of quorum sensing signal molecules in minced beef stored under various temperature and packaging conditions.

    Blana, Vasiliki A; Nychas, George-John E

    2014-03-01

    The presence of acylated homoserine lactones (AHLs) and autoinducer-2 (AI-2)-like activity was observed in meat stored under various temperatures (0, 5, 10 and 15°C) and packaging (air, modified atmospheres and modified atmospheres with oregano essential oil) conditions, and correlated with the ephemeral spoilage organisms that comprise the microbial community generally associated with this product. Quorum sensing signal molecules were found to be affected by the packaging conditions e.g. temperature and atmosphere used for meat preservation as a consequence of the development of a distinct microbial community. AHL signal molecules were detected at all incubation temperatures in minced beef samples, both stored aerobically and under modified atmospheres, when both pseudomonads and Enterobacteriaceae populations ranged from 10(7) to 10(9)CFU/g, but no signal molecules were detected in minced beef stored under modified atmospheres in the presence of volatile compounds of oregano essential oil, where both these groups failed to grow in high numbers. Additionally, no significant AI-2 activity was observed in the tested cell-free meat extracts (CFME), regardless of the indigenous bacterial populations. The presence of N-(β-ketocaproyl)-homoserine lactone was confirmed with TLC analysis of CFME. PMID:24380750

  3. Negative Feedback in the Vibrio harveyi Quorum-Sensing Circuit

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

    2010-03-01

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

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

    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 quencher of quorum sensing. In the presence of amikacin and carbenicillin, A. baumannii formed 0.07 and 0.02% persister cells, which increased 4- and 3-fold, respectively, in the presence of 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. PMID:24891106

  5. Marine-Derived Quorum-Sensing Inhibitory Activities Enhance the Antibacterial Efficacy of Tobramycin against Pseudomonas aeruginosa

    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.

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

    Rutherford, Steven T.; Bassler, Bonnie L

    2012-01-01

    Quorum sensing is a process of cell–cell communication that allows bacteria to share information about cell density and adjust gene expression accordingly. This process enables bacteria to express energetically expensive processes as a collective only when the impact of those processes on the environment or on a host will be maximized. Among the many traits controlled by quorum sensing is the expression of virulence factors by pathogenic bacteria. Here we review the quorum-sensing circuits of...

  7. A probable aculeacin A acylase from the Ralstonia solanacearum GMI1000 is N-acyl-homoserine lactone acylase with quorum-quenching activity

    Liao Chen-Ting

    2009-05-01

    Full Text Available Abstract Background The infection and virulence functions of diverse plant and animal pathogens that possess quorum sensing systems are regulated by N-acylhomoserine lactones (AHLs acting as signal molecules. AHL-acylase is a quorum quenching enzyme and degrades AHLs by removing the fatty acid side chain from the homoserine lactone ring of AHLs. This blocks AHL accumulation and pathogenic phenotypes in quorum sensing bacteria. Results An aac gene of undemonstrated function from Ralstonia solanacearum GMI1000 was cloned, expressed in Escherichia coli; it inactivated four AHLs that were tested. The sequence of the 795 amino acid polypeptide was considerably similar to the AHL-acylase from Ralstonia sp. XJ12B with 83% identity match and shared 39% identity with an aculeacin A acylase precursor from the gram-positive actinomycete Actinoplanes utahensis. Aculeacin A is a neutral lipopeptide antibiotic and an antifungal drug. An electrospray ionisation mass spectrometry (ESI-MS analysis verified that Aac hydrolysed the amide bond of AHL, releasing homoserine lactone and the corresponding fatty acids. However, ESI-MS analysis demonstrated that the Aac could not catalyze the hydrolysis of the palmitoyl moiety of the aculeacin A. Moreover, the results of MIC test of aculeacin A suggest that Aac could not deacylate aculeacin A. The specificity of Aac for AHLs showed a greater preference for long acyl chains than for short acyl chains. Heterologous expression of the aac gene in Chromobacterium violaceum CV026 effectively inhibited violacein and chitinase activity, both of which were regulated by the quorum-sensing mechanism. These results indicated that Aac could control AHL-dependent pathogenicity. Conclusion This is the first study to find an AHL-acylase in a phytopathogen. Our data provide direct evidence that the functioning of the aac gene (NP520668 of R. solanacearum GMI1000 is via AHL-acylase and not via aculeacin A acylase. Since Aac is a

  8. Homoserine Lactones, Methyl Oligohydroxybutyrates, and Other Extracellular Metabolites of Macroalgae-Associated Bacteria of the Roseobacter Clade: Identification and Functions.

    Ziesche, Lisa; Bruns, Hilke; Dogs, Marco; Wolter, Laura; Mann, Florian; Wagner-Döbler, Irene; Brinkhoff, Thorsten; Schulz, Stefan

    2015-09-21

    Twenty-four strains of marine Roseobacter clade bacteria were isolated from macroalgae and investigated for the production of quorum-sensing autoinducers, N-acylhomoserine lactones (AHLs). GC/MS analysis of the extracellular metabolites allowed us to evaluate the release of other small molecules as well. Nineteen strains produced AHLs, ranging from 3-OH-C10:0-HSL (homoserine lactone) to (2E,11Z)-C18:2-HSL, but no specific phylogenetic or ecological pattern of individual AHL occurrence was observed when cluster analysis was performed. Other identified compounds included indole, tropone, methyl esters of oligomers of 3-hydroxybutyric acid, and various amides, such as N-9-hexadecenoylalanine methyl ester (9-C16:1-NAME), a structural analogue of AHLs. Several compounds were tested for their antibacterial and antialgal activity on marine isolates likely to occur in the habitat of the macroalgae. Both AHLs and 9-C16:1-NAME showed high antialgal activity against Skeletonema costatum, whereas their antibacterial activity was low. PMID:26212108

  9. Inhibition of Quorum Sensing Mediated Virulence Factors Production in Urinary Pathogen Serratia marcescens PS1 by Marine Sponges.

    Annapoorani, Angusamy; Jabbar, Abdul Karim Kamil Abdul; Musthafa, Syed Khadar Syed; Pandian, Shunmugiah Karutha; Ravi, Arumugam Veera

    2012-06-01

    The focal intent of this study was to find out an alternative strategy for the antibiotic usage against bacterial infections. The quorum sensing inhibitory (QSI) activity of marine sponges collected from Palk Bay, India was evaluated against acyl homoserine lactone (AHL) mediated violacein production in Chromobacterium violaceum (ATCC 12472), CV026 and virulence gene expressions in clinical isolate Serratia marcescens PS1. Out of 29 marine sponges tested, the methanol extracts of Aphrocallistes bocagei (TS 8), Haliclona (Gellius) megastoma (TS 25) and Clathria atrasanguinea (TS 27) inhibited the AHL mediated violacein production in C. violaceum (ATCC 12472) and CV026. Further, these sponge extracts inhibited the AHL dependent prodigiosin pigment, virulence enzymes such as protease, hemolysin production and biofilm formation in S. marcescens PS1. However, these sponge extracts were not inhibitory to bacterial growth, which reveals the fact that the QSI activity of these extracts was not related to static or killing effects on bacteria. Based on the obtained results, it is envisaged that the marine sponges could pave the way to prevent quorum sensing (QS) mediated bacterial infections. PMID:23729876

  10. N-Acetylglucosamine Inhibits LuxR, LasR and CviR Based Quorum Sensing Regulated Gene Expression Levels.

    Kimyon, Önder; Ulutürk, Zehra I; Nizalapur, Shashidhar; Lee, Matthew; Kutty, Samuel K; Beckmann, Sabrina; Kumar, Naresh; Manefield, Mike

    2016-01-01

    N-acetyl glucosamine, the monomer of chitin, is an abundant source of carbon and nitrogen in nature as it is the main component and breakdown product of many structural polymers. Some bacteria use N-acyl-L-homoserine lactone (AHL) mediated quorum sensing (QS) to regulate chitinase production in order to catalyze the cleavage of chitin polymers into water soluble N-acetyl-D-glucosamine (NAG) monomers. In this study, the impact of NAG on QS activities of LuxR, LasR, and CviR regulated gene expression was investigated by examining the effect of NAG on QS regulated green fluorescent protein (GFP), violacein and extracellular chitinase expression. It was discovered that NAG inhibits AHL dependent gene transcription in AHL reporter strains within the range of 50-80% reduction at low millimolar concentrations (0.25-5 mM). Evidence is presented supporting a role for both competitive inhibition at the AHL binding site of LuxR type transcriptional regulators and catabolite repression. Further, this study shows that NAG down-regulates CviR induced violacein production while simultaneously up-regulating CviR dependent extracellular enzymes, suggesting that an unknown NAG dependent regulatory component influences phenotype expression. The quorum sensing inhibiting activity of NAG also adds to the list of compounds with known quorum sensing inhibiting activities. PMID:27602027

  11. Pseudomonas aeruginosa mutations in lasl and rhll quorum sensing systems result in milder chronic lung infection

    Wu, H.; Song, Z.J.; Givskov, Michael Christian;

    2001-01-01

    To understand the importance of quorum sensing in chronic Pseudomonas aeruginosa lung infection, the in vivo pathogenic effects of the wild-type P aeruginosa PAO1 and its double mutant, PAO1 lasI rhlI, in which the signal-generating parts of the quorum sensing systems are defective were compared...

  12. Lichen secondary metabolite evernic acid as potential quorum sensing inhibitor against Pseudomonas aeruginosa.

    Gökalsın, Barış; Sesal, Nüzhet Cenk

    2016-09-01

    Cystic Fibrosis is a genetic disease and it affects the respiratory and digestive systems. Pseudomonas aeruginosa infections in Cystic Fibrosis are presented as the main cause for high mortality and morbidity rates. Pseudomonas aeruginosa populations can regulate their virulence gene expressions via the bacterial communication system: quorum sensing. Inhibition of quorum sensing by employing quorum sensing inhibitors can leave the bacteria vulnerable. Therefore, determining natural sources to obtain potential quorum sensing inhibitors is essential. Lichens have ethnobotanical value for their medicinal properties and it is possible that their secondary metabolites have quorum sensing inhibitor properties. This study aims to investigate an alternative treatment approach by utilizing lichen secondary metabolite evernic acid to reduce the expressions of Pseudomonas aeruginosa virulence factors by inhibiting quorum sensing. For this purpose, fluorescent monitor strains were utilized for quorum sensing inhibitor screens and quantitative reverse-transcriptase PCR analyses were conducted for comparison. Results indicate that evernic acid is capable of inhibiting Pseudomonas aeruginosa quorum sensing systems. PMID:27465850

  13. Gene dosage compensation calibrates four regulatory RNAs to control Vibrio cholerae quorum sensing

    Svenningsen, Sine L; Tu, Kimberly C; Bassler, Bonnie L

    2009-01-01

    Quorum sensing is a mechanism of cell-to-cell communication that allows bacteria to coordinately regulate gene expression in response to changes in cell-population density. At the core of the Vibrio cholerae quorum-sensing signal transduction pathway reside four homologous small RNAs (sRNAs), named...

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

    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...

  15. Novel AI-2 quorum sensing inhibitors in Vibrio harveyi identified through structure-based virtual screening.

    Zhu, Peng; Peng, Hanjing; Ni, Nanting; Wang, Binghe; Li, Minyong

    2012-10-15

    In this letter, a high-throughput virtual screening was accomplished to identify potent inhibitors against AI-2 quorum sensing on the basis of Vibrio harveyi LuxPQ crystal structure. Seven compounds were found to inhibit AI-2 quorum sensing with IC(50) values in the micromolar range, and presented low cytotoxicity or no cytotoxicity in V. harveyi. PMID:22963763

  16. Quorum Sensing Regulates Type III Secretion in Vibrio harveyi and Vibrio parahaemolyticus

    Henke, Jennifer M.; Bassler, Bonnie L.

    2004-01-01

    In a process known as quorum sensing, bacteria communicate with one another by producing, releasing, detecting, and responding to signal molecules called autoinducers. Vibrio harveyi, a marine pathogen, uses two parallel quorum-sensing circuits, each consisting of an autoinducer-sensor pair, to control the expression of genes required for bioluminescence and a number of other target genes. Genetic screens designed to discover autoinducer-regulated targets in V. harveyi have revealed genes encoding components of a putative type III secretion (TTS) system. Using transcriptional reporter fusions and TTS protein localization studies, we show that the TTS system is indeed functional in V. harveyi and that expression of the genes encoding the secretion machinery requires an intact quorum-sensing signal transduction cascade. The newly completed genome of the closely related marine bacterium Vibrio parahaemolyticus, which is a human pathogen, shows that it possesses the genes encoding both of the V. harveyi-like quorum-sensing signaling circuits and that it also has a TTS system similar to that of V. harveyi. We show that quorum sensing regulates TTS in V. parahaemolyticus. Previous reports connecting quorum sensing to TTS in enterohemorrhagic and enteropathogenic Escherichia coli show that quorum sensing activates TTS at high cell density. Surprisingly, we find that at high cell density (in the presence of autoinducers), quorum sensing represses TTS in V. harveyi and V. parahaemolyticus. PMID:15175293

  17. Genetic Analysis of the Quorum Sensing Regulator EsaR

    Koziski, Jessica Marie

    2008-01-01

    Pantoea stewartii subsp. stewartii is the causative agent of Stewartâ s wilt disease in maize plants. The bacteria are injected into the plant by corn flea beetles during feeding. They colonize the xylem and overproduce a capsular exopolysaccharide (EPS) at high cell densities. The production of EPS is regulated by an EsaI/EsaR quorum sensing mechanism, homologous to the LuxI/R system. Although activation of the EPS encoding genes by EsaR occurs after it complexes to the AHL (3-oxo-C6-HSL), ...

  18. Quorum sensing Inhibitors as anti-pathogenic drugs

    Rasmussen, Thomas Bovbjerg; Givskov, Michael Christian

    2006-01-01

    reasons, particularly considering the emergence of increasingly antibiotic-resistant bacteria. Compounds capable of this type of interference have been termed anti-pathogenic drugs. A large variety of synthetic AHL analogues and natural products libraries have been screened and a number of QS inhibitors......Quorum-sensing (QS) signalling systems of pathogens are central regulators for the expression of virulence factors and represent highly attractive targets for the development of novel therapeutics. In Pseudomonas aeruginosa, QS systems are also involved in elevated antibiotic tolerance of biofilms...

  19. Glycation Reactivity of a Quorum-Sensing Signaling Molecule.

    Tsuchikama, Kyoji; Gooyit, Major; Harris, Tyler L; Zhu, Jie; Globisch, Daniel; Kaufmann, Gunnar F; Janda, Kim D

    2016-03-14

    Reported herein is that (4S)-4,5-dihydroxy-2,3-pentanedione (DPD) can undergo a previously undocumented non-enzymatic glycation reaction. Incubation of DPD with viral DNA or the antibiotic gramicidin S resulted in significant biochemical alterations. A protein-labeling method was consequently developed that facilitated the identification of unrecognized glycation targets of DPD in a prokaryotic system. These results open new avenues toward tracking and understanding the fate and function of the elusive quorum-sensing signaling molecule. PMID:26890076

  20. Vibrio harveyi quorum sensing: a coincidence detector for two autoinducers controls gene expression

    Mok, Kenny C.; Wingreen, Ned S.; Bassler, Bonnie L.

    2003-01-01

    In a process called quorum sensing, bacteria communicate with one another by exchanging chemical signals called autoinducers. In the bioluminescent marine bacterium Vibrio harveyi, two different auto inducers (AI-1 and AI-2) regulate light emission. Detection of and response to the V.harveyi autoinducers are accomplished through two two-component sensory relay systems: AI-1 is detected by the sensor LuxN and AI-2 by LuxPQ. Here we further define the V.harveyi quorum-sensing regulon by identifying 10 new quorum-sensing-controlled target genes. Our examination of signal processing and integration in the V.harveyi quorum-sensing circuit suggests that AI-1 and AI-2 act synergistically, and that the V.harveyi quorum-sensing circuit may function exclusively as a ‘coincidence detector’ that discriminates between conditions in which both autoinducers are present and all other conditions. PMID:12574123

  1. Bacterial quorum sensing: its role in virulence and possibilities for its control.

    Rutherford, Steven T; Bassler, Bonnie L

    2012-11-01

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

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

    Jakobsen, Tim Holm; Bragason, Steinn Kristinn; Phipps, Richard Kerry;

    2012-01-01

    traditional antibiotics to treat infections caused by bacterial biofilms and multidrug-resistant bacteria. Several QSIs of natural origin have been identified, and in this study, several common food products and plants were extracted and screened for QSI activity in an attempt to isolate and characterize...... transcend problems with selective pressures for antibiotic resistance, is to interrupt bacterial communication, also known as quorum sensing (QS), by means of signal antagonists, the so-called QS inhibitors (QSIs). Furthermore, QSI agents offer a potential solution to the deficiencies associated with use of...

  3. Quorum sensing communication between bacteria and human cells: signals, targets and functions

    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.

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

    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.

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

    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. PMID:24688531

  6. Discovery of new diketopiperazines inhibiting Burkholderia cenocepacia quorum sensing in vitro and in vivo.

    Scoffone, Viola C; Chiarelli, Laurent R; Makarov, Vadim; Brackman, Gilles; Israyilova, Aygun; Azzalin, Alberto; Forneris, Federico; Riabova, Olga; Savina, Svetlana; Coenye, Tom; Riccardi, Giovanna; Buroni, Silvia

    2016-01-01

    Burkholderia cenocepacia, an opportunistic respiratory pathogen particularly relevant for cystic fibrosis patients, is difficult to eradicate due to its high level of resistance to most clinically relevant antimicrobials. Consequently, the discovery of new antimicrobials as well as molecules capable of inhibiting its virulence is mandatory. In this regard quorum sensing (QS) represents a good target for anti-virulence therapies, as it has been linked to biofilm formation and is important for the production of several virulence factors, including proteases and siderophores. Here, we report the discovery of new diketopiperazine inhibitors of the B. cenocepacia acyl homoserine lactone synthase CepI, and report their anti-virulence properties. Out of ten different compounds assayed against recombinant CepI, four were effective inhibitors, with IC50 values in the micromolar range. The best compounds interfered with protease and siderophore production, as well as with biofilm formation, and showed good in vivo activity in a Caenorhabditis elegans infection model. These molecules were also tested in human cells and showed very low toxicity. Therefore, they could be considered for in vivo combined treatments with established or novel antimicrobials, to improve the current therapeutic strategies against B. cenocepacia. PMID:27580679

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

    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.

  8. Discovery of new diketopiperazines inhibiting Burkholderia cenocepacia quorum sensing in vitro and in vivo

    Scoffone, Viola C.; Chiarelli, Laurent R.; Makarov, Vadim; Brackman, Gilles; Israyilova, Aygun; Azzalin, Alberto; Forneris, Federico; Riabova, Olga; Savina, Svetlana; Coenye, Tom; Riccardi, Giovanna; Buroni, Silvia

    2016-01-01

    Burkholderia cenocepacia, an opportunistic respiratory pathogen particularly relevant for cystic fibrosis patients, is difficult to eradicate due to its high level of resistance to most clinically relevant antimicrobials. Consequently, the discovery of new antimicrobials as well as molecules capable of inhibiting its virulence is mandatory. In this regard quorum sensing (QS) represents a good target for anti-virulence therapies, as it has been linked to biofilm formation and is important for the production of several virulence factors, including proteases and siderophores. Here, we report the discovery of new diketopiperazine inhibitors of the B. cenocepacia acyl homoserine lactone synthase CepI, and report their anti-virulence properties. Out of ten different compounds assayed against recombinant CepI, four were effective inhibitors, with IC50 values in the micromolar range. The best compounds interfered with protease and siderophore production, as well as with biofilm formation, and showed good in vivo activity in a Caenorhabditis elegans infection model. These molecules were also tested in human cells and showed very low toxicity. Therefore, they could be considered for in vivo combined treatments with established or novel antimicrobials, to improve the current therapeutic strategies against B. cenocepacia. PMID:27580679

  9. Quorum sensing positively regulates flagellar motility in pathogenic Vibrio harveyi.

    Yang, Qian; Defoirdt, Tom

    2015-04-01

    Vibrios belonging to the Harveyi clade are among the major pathogens of aquatic organisms. Quorum sensing (QS) is essential for virulence of V. harveyi towards different hosts. However, most virulence factors reported to be controlled by QS to date are negatively regulated by QS, therefore suggesting that their impact on virulence is limited. In this study, we report that QS positively regulates flagellar motility. We found that autoinducer synthase mutants showed significantly lower swimming motility than the wild type, and the swimming motility could be restored by adding synthetic signal molecules. Further, motility of a luxO mutant with inactive QS (LuxO D47E) was significantly lower than that of the wild type and of a luxO mutant with constitutively maximal QS activity (LuxO D47A). Furthermore, we found that the expression of flagellar genes (both early, middle and late genes) was significantly lower in the luxO mutant with inactive QS when compared with wild type and the luxO mutant with maximal QS activity. Motility assays and gene expression also revealed the involvement of the quorum-sensing master regulator LuxR in the QS regulation of motility. Finally, the motility inhibitor phenamil significantly decreased the virulence of V. harveyi towards gnotobiotic brine shrimp larvae. PMID:24528485

  10. [Quorum sensing systems of regulation, synthesis of phenazine antibiotics, and antifungal (corrected) activity in rhizospheric bacterium Pseudomonas chlororaphis 449].

    Veselova, M a; Klein, Sh; Bass, I A; Lipasova, V A; Metlitskaia, A Z; Ovadis, M I; Chernin, L S; Khmel', I A

    2008-12-01

    Strain Pseudomonas chlororaphis 449, an antagonist of a broad spectrum of phytopathogenic microorganisms isolated from the maize rhizosphere, was shown to produce three phenazine antibiotics: phenazine-1-carboxylic acid (PCA), 2-hydroxylphenazine-1-carboxylic acid (2-OH-PCA), and 2-hydroxylphenazine (2-OH-PHZ). Two Quorum Sensing (QS) systems of regulation were identified: PhzIR and CsaI/R. Genes phzI and csaI were cloned and sequenced. Cells of strain 449 synthesize at least three types of AHL: N-butanoyl-L-homoserine lactone (C4-AHL), N-hexanoyl-L-homoserine lactone (C6-AHL), and N-(3-oxo-hexanoyl)-L-homoserine lactone (30C6-AHL). Transposon mutagenesis was used to generate mutants of strain 449 deficient in synthesis of phenazines, which carried inactivated phzA and phzB genes of the phenazine operon and gene phzO. Mutations phzA- and phzB-caused a drastic reduction in the antagonistic activity of bacteria toward phytopathogenic fungi. Both mutants lost the ability to protect cucumber and leguminous plants against phytopathogenic fungi Rhizoctonia solani and Sclerotinia sclerotiorum. These results suggest a significant role of phenazines in the antagonistic activity of P. chlororaphis 449. PMID:19178080

  11. Multiple small RNAs act additively to integrate sensory information and control quorum sensing in Vibrio harveyi

    Tu, Kimberly C.; Bassler, Bonnie L.

    2007-01-01

    Quorum sensing is a cell–cell communication mechanism that bacteria use to collectively regulate gene expression and, at a higher level, to coordinate group behavior. In the bioluminescent marine bacterium Vibrio harveyi, sensory information from three independent quorum-sensing systems converges on the shared response regulator LuxO. When LuxO is phosphorylated, it activates the expression of a putative repressor that destabilizes the mRNA encoding the master quorum-sensing transcriptional regulator LuxR. In the closely related species Vibrio cholerae, this repressor was revealed to be the RNA chaperone Hfq together with four small regulatory RNAs (sRNAs) called Qrr1–4 (quorum regulatory RNA). Here, we identify five Qrr sRNAs that control quorum sensing in V. harveyi. Mutational analysis reveals that only four of the five Qrrs are required for destabilization of the luxR mRNA. Surprisingly, unlike in V. cholerae where the sRNAs act redundantly, in V. harveyi, the Qrr sRNAs function additively to control quorum sensing. This latter mechanism produces a gradient of LuxR that, in turn, enables differential regulation of quorum-sensing target genes. Other regulators appear to be involved in control of V. harveyi qrr expression, allowing the integration of additional sensory information into the regulation of quorum-sensing gene expression. PMID:17234887

  12. Computer-Aided Identification of Recognized Drugs as Pseudomonas aeruginosa Quorum-Sensing Inhibitors▿ †

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

    2009-01-01

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

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

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

    2009-06-01

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

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

    Defoirdt, Tom; Sorgeloos, Patrick

    2012-12-01

    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

  15. Quorum sensing signal-response systems in Gram-negative bacteria.

    Papenfort, Kai; Bassler, Bonnie L

    2016-08-11

    Bacteria use quorum sensing to orchestrate gene expression programmes that underlie collective behaviours. Quorum sensing relies on the production, release, detection and group-level response to extracellular signalling molecules, which are called autoinducers. Recent work has discovered new autoinducers in Gram-negative bacteria, shown how these molecules are recognized by cognate receptors, revealed new regulatory components that are embedded in canonical signalling circuits and identified novel regulatory network designs. In this Review we examine how, together, these features of quorum sensing signal-response systems combine to control collective behaviours in Gram-negative bacteria and we discuss the implications for host-microbial associations and antibacterial therapy. PMID:27510864

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

    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. Homoserine lactones: Do plants really listen to bacterial talk?

    Klein, Ilona; von Rad, Uta; Durner, Jörg

    2009-01-01

    The bacterial quorum sensing signals N-acyl-L-homoserine lactones (AHL) enable bacterial cells to regulate gene expression depending on population density, which eventually leads to invasion of hosts. Only little is known about the molecular ways of plants reacting to these bacterial signals. Recently, we showed that the contact of Arabidopsis thaliana roots with N-hexanoyl-DL-homoserine-lactone (HHL) resulted in distinct transcriptional changes in roots and shoots, respectively. In addition,...

  18. Synchronization and quorum sensing in a swarm of humanoid robots

    Bechon, Patrick

    2012-01-01

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

  19. Fine-Tuning Covalent Inhibition of Bacterial Quorum Sensing.

    Amara, Neri; Gregor, Rachel; Rayo, Josep; Dandela, Rambabu; Daniel, Erik; Liubin, Nina; Willems, H Marjo E; Ben-Zvi, Anat; Krom, Bastiaan P; Meijler, Michael M

    2016-05-01

    Emerging antibiotic resistance among human pathogens has galvanized efforts to find alternative routes to combat bacterial virulence. One new approach entails interfering with the ability of bacteria to coordinate population-wide gene expression, or quorum sensing (QS), thus inhibiting the production of virulence factors and biofilm formation. We have recently developed such a strategy by targeting LasR, the master regulator of QS in the opportunistic human pathogen Pseudomonas aeruginosa, through the rational design of covalent inhibitors closely based on the core structure of the native ligand. We now report several groups of new inhibitors, one of which, fluoro-substituted ITC-12, displayed complete covalent modification of LasR, as well as effective QS inhibition in vitro and promising in vivo results. In addition to their potential clinical relevance, this series of synthetic QS modulators can be used as a tool to further unravel the complicated QS regulation in P. aeruginosa. PMID:26840534

  20. Qualitative and quantitative determination of quorum sensing inhibition in vitro

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

    2011-01-01

    The formation of biofilms in conjunction with quorum sensing (QS)-regulated expression of virulence by opportunistic pathogens contributes significantly to immune evasion and tolerance to a variety of antimicrobial treatments. The present protocol describes methods to determine the in vitro...... of reporter strains consisting of a lasB-gfp or rhlA-gfp fusion in P. aeruginosa for qualitative and quantitative evaluation of the inhibition of the two major QS pathways, monitored as reduced expression of green fluorescence. By the use of an in vitro flow cell system it is possible to study the...... QSI activity by monitoring its ability to interfere with the protective functions of bacterial biofilm. For evaluation of the global effects of QSI compounds, we present a protocol for the DNA microarray-based transcriptomics. Using these in vitro methods it is possible to evaluate the potential of...

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

    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. PMID:27483473

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

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

    2015-01-01

    Pantoea stewartii strain M073a is a Gram-negative bacterium isolated from a tropical waterfall. This strain exhibits quorum-sensing activity. Here, the assembly and annotation of its genome are presented. PMID:25700398

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

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

    2015-01-01

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

  4. Active regulation of receptor ratios controls integration of quorum-sensing signals in Vibrio harveyi

    Teng, Shu-Wen; Schaffer, Jessica N; Tu, Kimberly C; Mehta, Pankaj; Lu, Wenyun; Ong, N P; Bassler, Bonnie L; Wingreen, Ned S

    2011-01-01

    Quorum sensing is a chemical signaling mechanism used by bacteria to communicate and orchestrate group behaviors. Multiple feedback loops exist in the quorum-sensing circuit of the model bacterium Vibrio harveyi. Using fluorescence microscopy of individual cells, we assayed the activity of the quorum-sensing circuit, with a focus on defining the functions of the feedback loops. We quantitatively investigated the signaling input–output relation both in cells with all feedback loops present as well as in mutants with specific feedback loops disrupted. We found that one of the feedback loops regulates receptor ratios to control the integration of multiple signals. Together, the feedback loops affect the input–output dynamic range of signal transmission and the noise in the output. We conclude that V. harveyi employs multiple feedback loops to simultaneously control quorum-sensing signal integration and to ensure signal transmission fidelity. PMID:21613980

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

    Zhang, Lianbo; Gao, Qingguo; Chen, Wanying;

    2013-01-01

    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...

  6. Treatment of Staphylococcus aureus Biofilm Infection by the Quorum-Sensing Inhibitor RIP▿

    Balaban, Naomi; Cirioni, Oscar; Giacometti, Andrea; Ghiselli, Roberto; Braunstein, Joel B.; Silvestri, Carmela; Mocchegiani, Federico; Saba, Vittorio; Scalise, Giorgio

    2007-01-01

    The quorum-sensing inhibitor RIP inhibits staphylococcal TRAP/agr systems and both TRAP- and agr-negative strains are deficient in biofilm formation in vivo, indicating the importance of quorum sensing to biofilms in the host. RIP injected systemically into rats has been found to have strong activity in preventing methicillin-resistant Staphylococcus aureus graft infections, suggesting that RIP can be used as a therapeutic agent.

  7. Antibiotic Resistance Profiles and Quorum Sensing-Dependent Virulence Factors in Clinical Isolates of Pseudomonas Aeruginosa

    Wang, Huafu; Tu, Faping; Gui, Zhihong; Lu, Xianghong; Chu, Weihua

    2013-01-01

    Pseudomonas aeruginosa produces multiple virulence factors that have been associated with quorum sensing. The aim of this study was to evaluate the prevalence of drug resistant profiles and quorum sensing related virulence factors. Pseudomonas aeruginosa were collected from different patients hospitalized in China, the isolates were tested for their susceptibility to different common antimicrobial drugs and detected QS-related virulence factors. We identified 170 isolates displaying impaired ...

  8. Effect of Candida albicans and Candida dubliniensis planktonic/biofilm quorum sensing molecules on yeast morphogenesis

    Henriques, Mariana; Martins, M.; Azeredo, Joana; Oliveira, Rosário

    2006-01-01

    One of the aims of this work was to study the effect of farnesol, a quorum sensing molecule for Candida albicans, on morphologic inhibition of Candida dubliniensis. The second goal of this work was to confirm if Candida dubliniensis also excreted quorum sensing molecules, on both planktonic and biofilm forms. The results clearly demonstrate that Candida dubliniensis undergoes morphological alterations triggered by farnesol. It was also found that supernatants of Candida dubliniensis and Ca...

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

    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

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

    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

  11. A quorum-sensing inhibitor blocks Pseudomonas aeruginosa virulence and biofilm formation

    O’Loughlin, Colleen T.; Miller, Laura C.; Siryaporn, Albert; Drescher, Knut; Semmelhack, Martin F.; Bassler, Bonnie L.

    2013-01-01

    In this study, we prepare synthetic molecules and analyze them for inhibition of the Pseudomonas quorum-sensing receptors LasR and RhlR. Our most effective compound, meta-bromo-thiolactone, not only prevents virulence factor expression and biofilm formation but also protects Caenorhabditis elegans and human A549 lung epithelial cells from quorum-sensing–mediated killing by Pseudomonas aeruginosa. This anti–quorum-sensing molecule is capable of influencing P. aeruginosa virulence in tissue cul...

  12. Computer-Aided Identification of Recognized Drugs as Pseudomonas aeruginosa Quorum-Sensing Inhibitors▿ †

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

    2009-01-01

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

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

    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.

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

    Vincent Leung

    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.

  15. Directed evolution of the quorum-sensing regulator EsaR for increased signal sensitivity.

    Shong, Jasmine; Huang, Yao-Ming; Bystroff, Christopher; Collins, Cynthia H

    2013-04-19

    The use of cell-cell communication or "quorum sensing (QS)" elements from Gram-negative Proteobacteria has enabled synthetic biologists to begin engineering systems composed of multiple interacting organisms. However, additional tools are necessary if we are to progress toward synthetic microbial consortia that exhibit more complex, dynamic behaviors. EsaR from Pantoea stewartii subsp. stewartii is a QS regulator that binds to DNA as an apoprotein and releases the DNA when it binds to its cognate signal molecule, 3-oxohexanoyl-homoserine lactone (3OC6HSL). In the absence of 3OC6HSL, EsaR binds to DNA and can act as either an activator or a repressor of transcription. Gene expression from P(esaR), which is repressed by wild-type EsaR, requires 100- to 1000-fold higher concentrations of signal than commonly used QS activators, such as LuxR and LasR. Here we have identified EsaR variants with increased sensitivity to 3OC6HSL using directed evolution and a dual ON/OFF screening strategy. Although we targeted EsaR-dependent derepression of P(esaR), our EsaR variants also showed increased 3OC6HSL sensitivity at a second promoter, P(esaS), which is activated by EsaR in the absence of 3OC6HSL. Here, the increase in AHL sensitivity led to gene expression being turned off at lower concentrations of 3OC6HSL. Overall, we have increased the signal sensitivity of EsaR more than 70-fold and generated a set of EsaR variants that recognize 3OC6HSL concentrations ranging over 4 orders of magnitude. QS-dependent transcriptional regulators that bind to DNA and are active in the absence of a QS signal represent a new set of tools for engineering cell-cell communication-dependent gene expression. PMID:23363022

  16. Inhibition of quorum sensing-controlled virulence factors in Pseudomonas aeruginosa by human serum paraoxonase.

    Aybey, Aynur; Demirkan, Elif

    2016-02-01

    The role of quorum sensing (QS) in the regulation of virulence factor production in Pseudomonas aeruginosa is well established. Increased antibiotic resistance in this bacterium has led to the search for new treatment options, and inhibition of the QS system has been explored for potential therapeutic benefits. If the use of QS inhibitory agents were to lead to a reduction in bacterial virulence, new approaches in the treatment of P. aeruginosa infections could be further developed. Accordingly, we examined whether human serum paraoxonase 1 (hPON1), which uses lactonase activity to hydrolyse N-acyl homoserine lactones, could cleave P. aeruginosa-derived signalling molecules. hPON1 was purified using ammonium sulfate precipitation and hydrophobic interaction chromatography (Sepharose 4B-L-tyrosine-1-naphthylamine). Different concentrations of hPON1 were found to reduce various virulence factors including pyocyanin, rhamnolipid, elastase, staphylolytic LasA protease and alkaline protease. Although treatment with 0.1-10 mg hPON1 ml(-1) did not show a highly inhibitory effect on elastase and staphylolytic LasA protease production, it resulted in good inhibitory effects on alkaline protease production at concentrations as low as 0.1 mg ml(-1). hPON1 also reduced the production of pyocyanin and rhamnolipid at a concentration of 1.25 mg ml(-1 )(within a range of 0.312-5 mg ml(-1)). In addition, rhamnolipid, an effective biosurfactant reported to stimulate the biodegradation of hydrocarbons, was able to degrade oil only in the absence of hPON1. PMID:26654051

  17. Quorum Sensing Inhibiting Activity of Streptomyces coelicoflavus Isolated from Soil

    Hassan, Ramadan; Shaaban, Mona I.; Abdel Bar, Fatma M.; El-Mahdy, Areej M.; Shokralla, Shadi

    2016-01-01

    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 anti

  18. Where antibiotic resistance mutations meet quorum-sensing

    Rok Krašovec

    2014-06-01

    Full Text Available We do not need to rehearse the grim story of the global rise of antibiotic resistant microbes. But what if it were possible to control the rate with which antibiotic resistance evolves by de novo mutation? It seems that some bacteria may already do exactly that: they modify the rate at which they mutate to antibiotic resistance dependent on their biological environment. In our recent study [Krašovec, et al. Nat. Commun. (2014, 5, 3742] we find that this modification depends on the density of the bacterial population and cell-cell interactions (rather than, for instance, the level of stress. Specifically, the wild-type strains of Escherichia coli we used will, in minimal glucose media, modify their rate of mutation to rifampicin resistance according to the density of wild-type cells. Intriguingly, the higher the density, the lower the mutation rate (Figure 1. Why this novel density-dependent ‘mutation rate plasticity’ (DD-MRP occurs is a question at several levels. Answers are currently fragmentary, but involve the quorum-sensing gene luxS and its role in the activated methyl cycle.

  19. Quorum sensing in water and wastewater treatment biofilms.

    Feng, Lin; Wu, Zhuoying; Yu, Xin

    2013-04-01

    Fixed film processes and activated sludge processes are two main families of wastewater treatment systems which all refer to the heterogeneous microbial communities. Meanwhile, biofilms in drinking water distribution systems (DWDS) and biofouling in membrane systems are significant problems in the water and wastewater treatment which reduce the microbial quality of drinking water and limit the development of membrane system respectively. Since biofilms and quorum sensing (QS) as two microbial social behaviors have been inextricably linked, a number of studies have focused on the role of QS signaling and QS inhibition in the processes of water and wastewater treatment, which will help us engineer these biological treatment processes successfully and develop promising approaches for control of microbial adhesion, colonization and biofilm formation. This review gives a summary of recent known QS mechanisms and their role in biofilm formation for different species. Particular attentions are dedicated to the signaling molecules involved in some microbial granulation processes and the potential applications by some of their natural and synthetic analogues in the treatment of membrane biofouling. PMID:24620615

  20. Parallel quorum sensing signaling pathways in Vibrio cholerae.

    Jung, Sarah A; Hawver, Lisa A; Ng, Wai-Leung

    2016-05-01

    Quorum sensing (QS) is a microbial signaling process for monitoring population density and complexity. Communication among bacterial cells via QS relies on the production, secretion, and detection of small molecules called autoinducers. Many bacteria have evolved their QS systems with different network architectures to incorporate information from multiple signals. In the human pathogen Vibrio cholerae, at least four parallel signaling pathways converge to control the activity of a single regulator to modulate its QS response. By integrating multiple signal inputs, it is believed that Vibrio species can survey intra-species, intra-genus, and inter-species populations and program their gene expression accordingly. Our recent studies suggest that this "many-to-one" circuitry is also important for maintaining the integrity of the input-output relationship of the system and minimizes premature commitment to QS due to signal perturbation. Here we discuss the implications of this specific parallel network setup for V. cholerae intercellular communication and how this system arrangement affects our approach to manipulate the QS response of this clinically important pathogen. PMID:26545759

  1. Fungal quorum sensing molecules: Role in fungal morphogenesis and pathogenicity.

    Wongsuk, Thanwa; Pumeesat, Potjaman; Luplertlop, Natthanej

    2016-05-01

    When microorganisms live together in high numbers, they need to communicate with each other. To achieve cell-cell communication, microorganisms secrete molecules called quorum-sensing molecules (QSMs) that control their biological activities and behaviors. Fungi secrete QSMs such as farnesol, tyrosol, phenylethanol, and tryptophol. The role of QSMs in fungi has been widely studied in both yeasts and filamentous fungi, for example in Candida albicans, C. dubliniensis, Aspergillus niger, A. nidulans, and Fusarium graminearum. QSMs impact fungal morphogenesis (yeast-to-hypha formation) and also play a role in the germination of macroconidia. QSMs cause fungal cells to initiate programmed cell death, or apoptosis, and play a role in fungal pathogenicity. Several types of QSMs are produced during stages of biofilm development to control cell population or morphology in biofilm communities. This review article emphasizes the role of fungal QSMs, especially in fungal morphogenesis, biofilm formation, and pathogenicity. Information about QSMs may lead to improved measures for controlling fungal infection. PMID:26972663

  2. Quorum Sensing: An Under-Explored Phenomenon in the Phylum Actinobacteria

    Polkade, Ashish V.; Mantri, Shailesh S.; Patwekar, Umera J.; Jangid, Kamlesh

    2016-01-01

    Quorum sensing is known to play a major role in the regulation of secondary metabolite production, especially, antibiotics, and morphogenesis in the phylum Actinobacteria. Although it is one of the largest bacterial phylum, only 25 of the 342 genera have been reported to use quorum sensing. Of these, only nine have accompanying experimental evidence; the rest are only known through bioinformatic analysis of gene/genome sequences. It is evident that this important communication mechanism is not extensively explored in Actinobacteria. In this review, we summarize the different quorum sensing systems while identifying the limitations of the existing screening strategies and addressing the improvements that have taken place in this field in recent years. The γ-butyrolactone system turned out to be almost exclusively limited to this phylum. In addition, methylenomycin furans, AI-2 and other putative AHL-like signaling molecules are also reported in Actinobacteria. The lack of existing screening systems in detecting minute quantities and of a wider range of signaling molecules was a major reason behind the limited information available on quorum sensing in this phylum. However, recent improvements in screening strategies hold a promising future and are likely to increase the discovery of new signaling molecules. Further, the quorum quenching ability in many Actinobacteria has a great potential in controlling the spread of plant and animal pathogens. A systematic and coordinated effort is required to screen and exploit the enormous potential that quorum sensing in the phylum Actinobacteria has to offer for human benefit. PMID:26904007

  3. Anti-quorum sensing potential of Adenanthera pavonina

    Halkare Suryanarayana Vasavi

    2015-01-01

    Full Text Available Background: Quorum sensing (QS in Pseudomonas aeruginosa plays a key role in virulence factor production, biofilm formation and antimicrobial resistance. Because of emerging antimicrobial resistance in P. aeruginosa, there is a need to find an alternate nonantibiotic agent for the control of infections caused by this organism. Objective: To evaluate anti-QS activity of Adenanthera pavonina L., a medicinal plant used in traditional medicine. Materials and Methods: Preliminary screening for anti-QS activity of ethanol extract of A. pavonina was carried out using Chromobacterium violaceum CV026 biosensor strain and inhibition of QS-regulated violacein production was quantified using C. violaceum ATCC12472. Bioassay guided fractionation of ethanol extract resulted in ethyl acetate fraction (AEF with strong anti-QS activity and AEF was evaluated for inhibition of QS-regulated pyocyanin production, proteolytic, elastolytic activity, swarming motility and biofilm formation in P. aeruginosaPAO1. Results: AEF, at 0.5 mg/ml, inhibited pyocyanin production completely and at 1 mg/ml of AEF, complete inhibition of proteolytic and elastolytic activities were observed. However, viability of P. aeruginosa PAO1 was not affected at the tested concentrations of AEF as observed by cell count. Swarming motility was inhibited at the concentration of 0.1 mg/ml of AEF. Thin layer chromatography and biosensor overlay of AEF showed violacein inhibition zone at Rf value 0.63. Conclusion: From the results of this study, it can be concluded that A. pavonina extracts can be used as effective anti-QS agents.

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

    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.

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

    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.

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

    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. PMID:26787913

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

    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,

  8. Pseudomonas aeruginosa mutations in lasI and rhlI quorum sensing systems result in milder chronic lung infection

    Wu, H; Song, Z; Givskov, Michael;

    2001-01-01

    To understand the importance of quorum sensing in chronic Pseudomonas aeruginosa lung infection, the in vivo pathogenic effects of the wild-type P. aeruginosa PAO1 and its double mutant, PAO1 lasI rhlI, in which the signal-generating parts of the quorum sensing systems are defective were compared...

  9. Synthesis of furanone-based natural product analogues with quorum sensing antagonist activity

    Hjelmgaard, Thomas; Persson, T.; Rasmussen, Thomas Bovbjerg;

    2003-01-01

    The synthesis of 5- and 3-(1'-hydroxyalkyl)-substituted 5H-furan-2-ones 4a-d and 8a-d as well as 5-alkylidene-5H-furan-2-ones 5a-d is described. A study of the structure-activity relationship of these furanone-based natural product analogues towards two different quorum sensing systems is reported....... Although the synthesized compounds are not as potent quorum sensing inhibitors as some natural counterparts and a synthetic analogue hereof, interesting structure-activity relationships are seen....

  10. Pharmacological inhibition of quorum sensing for the treatment of chronic bacterial infections

    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...... mechanisms and potential antipathogenic drugs that specifically target quorum-sensing systems in a manner unlikely to pose a selective pressure for the development of resistant mutants....

  11. A model for signal transduction during quorum sensing in Vibrio harveyi

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

    2009-12-01

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

  12. A model for signal transduction during quorum sensing in Vibrio harveyi

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

  13. Structure/function analysis of the Pantoea stewartii quorum-sensing regulator EsaR as an activator of transcription.

    Schu, Daniel J; Carlier, Aurelien L; Jamison, Katherine P; von Bodman, Susanne; Stevens, Ann M

    2009-12-01

    In Pantoea stewartii subsp. stewartii, two regulatory proteins are key to the process of cell-cell communication known as quorum sensing: the LuxI and LuxR homologues EsaI and EsaR. Most LuxR homologues function as activators of transcription in the presence of their cognate acylated homoserine lactone (AHL) signal. However, EsaR was initially found to function as a repressor in the absence of AHL. Previous studies demonstrated that, in the absence of AHL, EsaR retains the ability to function as a weak activator of the lux operon in recombinant Escherichia coli. Here it is shown that both the N-terminal and the C-terminal domains of EsaR are necessary for positive regulation. A site-directed mutagenesis study, guided by homology modeling to LuxR and TraR, has revealed three critical residues in EsaR that are involved in activation of RNA polymerase. In addition, a native EsaR-activated promoter has been identified, which controls expression of a putative regulatory sRNA in P. stewartii. PMID:19820098

  14. Isolation and Molecular Characterization of Biofouling Bacteria and Profiling of Quorum Sensing Signal Molecules from Membrane Bioreactor Activated Sludge

    Harshad Lade

    2014-02-01

    Full Text Available The formation of biofilm in a membrane bioreactor depends on the production of various signaling molecules like N-acyl homoserine lactones (AHLs. In the present study, a total of 200 bacterial strains were isolated from membrane bioreactor activated sludge and screened for AHLs production using two biosensor systems, Chromobacterium violaceum CV026 and Agrobacterium tumefaciens A136. A correlation between AHLs production and biofilm formation has been made among screened AHLs producing strains. The 16S rRNA gene sequence analysis revealed the dominance of Aeromonas and Enterobacter sp. in AHLs production; however few a species of Serratia, Leclercia, Pseudomonas, Klebsiella, Raoultella and Citrobacter were also identified. The chromatographic characterization of sludge extract showed the presence of a broad range of quorum sensing signal molecules. Further identification of sludge AHLs by thin layer chromatography bioassay and high performance liquid chromatography confirms the presence of C4-HSL, C6-HSL, C8-HSL, 3-oxo-C8-HSL, C10-HSL, C12-HSL, 3-oxo-C12-HSL and C14-HSL. The occurrence of AHLs in sludge extract and dominance of Aeromonas and Enterobacter sp. in activated sludge suggests the key role of these bacterial strains in AHLs production and thereby membrane fouling.

  15. Isolation and Molecular Characterization of Biofouling Bacteria and Profiling of Quorum Sensing Signal Molecules from Membrane Bioreactor Activated Sludge

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

    2014-01-01

    The formation of biofilm in a membrane bioreactor depends on the production of various signaling molecules like N-acyl homoserine lactones (AHLs). In the present study, a total of 200 bacterial strains were isolated from membrane bioreactor activated sludge and screened for AHLs production using two biosensor systems, Chromobacterium violaceum CV026 and Agrobacterium tumefaciens A136. A correlation between AHLs production and biofilm formation has been made among screened AHLs producing strains. The 16S rRNA gene sequence analysis revealed the dominance of Aeromonas and Enterobacter sp. in AHLs production; however few a species of Serratia, Leclercia, Pseudomonas, Klebsiella, Raoultella and Citrobacter were also identified. The chromatographic characterization of sludge extract showed the presence of a broad range of quorum sensing signal molecules. Further identification of sludge AHLs by thin layer chromatography bioassay and high performance liquid chromatography confirms the presence of C4-HSL, C6-HSL, C8-HSL, 3-oxo-C8-HSL, C10-HSL, C12-HSL, 3-oxo-C12-HSL and C14-HSL. The occurrence of AHLs in sludge extract and dominance of Aeromonas and Enterobacter sp. in activated sludge suggests the key role of these bacterial strains in AHLs production and thereby membrane fouling. PMID:24499972

  16. Biosynthesis of the antifungal haterumalide, oocydin A, in Serratia, and its regulation by quorum sensing, RpoS and Hfq.

    Matilla, Miguel A; Leeper, Finian J; Salmond, George P C

    2015-08-01

    Polyketides represent an important class of bioactive natural products with a broad range of biological activities. We identified recently a large trans-acyltransferase (AT) polyketide synthase gene cluster responsible for the biosynthesis of the antifungal, anti-oomycete and antitumor haterumalide, oocydin A (ooc). Using genome sequencing and comparative genomics, we show that the ooc gene cluster is widespread within biocontrol and phytopathogenic strains of the enterobacteria, Serratia and Dickeya. The analysis of in frame deletion mutants confirmed the role of a hydroxymethylglutaryl-coenzyme A synthase cassette, three flavin-dependent tailoring enzymes, a free-standing acyl carrier protein and two hypothetical proteins in oocydin A biosynthesis. The requirement of the three trans-acting AT domains for the biosynthesis of the macrolide was also demonstrated. Expression of the ooc gene cluster was shown to be positively regulated by an N-acyl-L-homoserine lactone-based quorum sensing system, but operating in a strain-dependent manner. At a post-transcriptional level, the RNA chaperone, Hfq, plays a key role in oocydin A biosynthesis. The Hfq-dependent regulation is partially mediated by the stationary phase sigma factor, RpoS, which was also shown to positively regulate the synthesis of the macrolide. Our results reveal differential regulation of the divergently transcribed ooc transcriptional units, highlighting the complexity of oocydin A production. PMID:25753587

  17. Investigation of quorum sensing-dependent gene expression in Burkholderia gladioli BSR3 through RNA-seq analyses.

    Kim, Sunyoung; Park, Jungwook; Choi, Okhee; Kim, Jinwoo; Seo, Young-Su

    2014-12-28

    The plant pathogen Burkholderia gladioli, which has a broad host range that includes rice and onion, causes bacterial panicle blight and sheath rot. Based on the complete genome sequence of B. gladioli BSR3 isolated from infected rice sheaths, the genome of B. gladioli BSR3 contains the luxI/luxR family of genes. Members of this family encode N-acyl-homoserine lactone (AHL) quorum sensing (QS) signal synthase and the LuxR-family AHL signal receptor, which are similar to B. glumae BGR1. In B. glumae, QS has been shown to play pivotal roles in many bacterial behaviors. In this study, we compared the QS-dependent gene expression between B. gladioli BSR3 and a QS-defective B. gladioli BSR3 mutant in two different culture states (10 and 24 h after incubation, corresponding to an exponential phase and a stationary phase) using RNA sequencing (RNA-seq). RNA-seq analyses including gene ontology and pathway enrichment revealed that the B. gladioli BSR3 QS system regulates genes related to motility, toxin production, and oxalogenesis, which were previously reported in B. glumae. Moreover, the uncharacterized polyketide biosynthesis is activated by QS, which was not detected in B. glumae. Thus, we observed not only common QS-dependent genes between B. glumae BGR1 and B. gladioli BSR3, but also unique QS-dependent genes in B. gladioli BSR3. PMID:25223327

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

    Singh, Ravindra Pal; Baghel, Ravi S; Reddy, C R K; Jha, Bhavanath

    2015-01-01

    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 (QS) 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. PMID:25788899

  19. The autoregulatory role of EsaR, a quorum-sensing regulator in Pantoea stewartii ssp. stewartii: evidence for a repressor function.

    Minogue, Timothy D; Wehland-von Trebra, Markus; Bernhard, Frank; von Bodman, Susanne B

    2002-06-01

    Capsular polysaccharide synthesis and virulence in the plant pathogenic bacterium Pantoea stewartii ssp. stewartii requires the quorum-sensing regulatory proteins, EsaR and EsaI, and the diffusible inducer N-(3-oxo-hexanoyl)-L-homoserine lactone. Prior mutational studies suggested that EsaR might function as a repressor of quorum sensing in the control of capsular polysaccharide synthesis. Further, a lux box-like palindromic sequence coinciding with the putative -10 element of the esaR promoter suggested a possible negative autoregulatory role for EsaR. This report presents genetic evidence that EsaR represses the esaR gene under inducer-limiting conditions, and that addition of inducer promotes rapid, dose-dependent derepression. DNA mobility-shift assays and analyses by surface plasmon resonance refractometry show that EsaR binds target DNAs in a ligand-free state, and that inducer alters the binding characteristics of EsaR. Physical measurements indicate that the EsaR protein binds N-(3-oxo-hexanoyl)-L-homoserine lactone, in a 1:1 protein:ligand ratio, and that inducer binding enhances the thermal stability of the EsaR protein. These combined genetic and biochemical data establish that EsaR regulates its own expression by signal-independent repression and signal-dependent derepression. Additionally, we provide evidence that EsaR does not govern the expression of the linked esaI gene, thus EsaR has no role in controlling coinducer synthesis. PMID:12067349

  20. Structure and Inhibition of Quorum Sensing Target from Streptococcus pneumoniae

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

    2006-01-01

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

  1. Effect of the synthetic cannabinoid HU-210 on quorum sensing and on the production of quorum sensing-mediated virulence factors by Vibrio harveyi

    Soni, Divya; Smoum, Reem; Breuer, Aviva; Mechoulam, Raphael; Steinberg, Doron

    2015-01-01

    Background Bacterial populations communicate through the cell density-dependent mechanism of quorum sensing (QS). Vibrio harveyi, one of the best studied model organisms for QS, was used to explore effects of the synthetic cannabinoid HU-210 on QS and different QS-regulated physiological processes in bacteria. Results Analysis of QS-regulated bioluminescence in wild-type and mutant strains of V. harveyi revealed that HU-210 affects the autoinducer-2 (AI-2) pathway, one of three known QS casca...

  2. Plant phenolic acids affect the virulence of Pectobacterium aroidearum and P. carotovorum ssp. brasiliense via quorum sensing regulation.

    Joshi, Janak Raj; Burdman, Saul; Lipsky, Alexander; Yariv, Shaked; Yedidia, Iris

    2016-05-01

    Several studies have reported effects of the plant phenolic acids cinnamic acid (CA) and salicylic acid (SA) on the virulence of soft rot enterobacteria. However, the mechanisms involved in these processes are not yet fully understood. Here, we investigated whether CA and SA interfere with the quorum sensing (QS) system of two Pectobacterium species, P. aroidearum and P. carotovorum ssp. brasiliense, which are known to produce N-acyl-homoserine lactone (AHL) QS signals. Our results clearly indicate that both phenolic compounds affect the QS machinery of the two species, consequently altering the expression of bacterial virulence factors. Although, in control treatments, the expression of QS-related genes increased over time, the exposure of bacteria to non-lethal concentrations of CA or SA inhibited the expression of QS genes, including expI, expR, PC1_1442 (luxR transcriptional regulator) and luxS (a component of the AI-2 system). Other virulence genes known to be regulated by the QS system, such as pecS, pel, peh and yheO, were also down-regulated relative to the control. In agreement with the low levels of expression of expI and expR, CA and SA also reduced the level of the AHL signal. The effects of CA and SA on AHL signalling were confirmed in compensation assays, in which exogenous application of N-(β-ketocaproyl)-l-homoserine lactone (eAHL) led to the recovery of the reduction in virulence caused by the two phenolic acids. Collectively, the results of gene expression studies, bioluminescence assays, virulence assays and compensation assays with eAHL clearly support a mechanism by which CA and SA interfere with Pectobacterium virulence via the QS machinery. PMID:26177258

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

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

    2002-01-01

    of important virulence factors, indicating a general effect on target genes of the las quorum sensing circuit. The furanone was applied to P. aeruginosa biofilms established in biofilm flow chambers. The Gfp-based analysis reveals that the compound penetrates microcolonies and blocks cell signalling and quorum...

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

    Rasmussen, T B; Manefield, M; Andersen, J B;

    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...

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

    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.

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

    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. PMID:27020680

  7. Chemical Talking with Living Systems: Molecular Switches Steer Quorum Sensing in Bacteria.

    Schweighauser, Luca; Wegner, Hermann A

    2015-08-17

    New avenues in bacterial engineering: An azobenzene molecular switch has been incorporated into an autoinducer for quorum sensing (QS) in bacteria. The authors demonstrated that irradiation with different wavelengths of light influences the QS system thereby controlling gene expression as well as the phenotype, as exemplified by pyocyanin production. PMID:26078043

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

    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...

  9. The Vibrio harveyi quorum-sensing system uses shared regulatory components to discriminate between multiple autoinducers

    Waters, Christopher M.; Bassler, Bonnie L.

    2006-01-01

    The quorum-sensing bacterium Vibrio harveyi produces and responds to three autoinducers (AIs), and this sensory information converges to control the expression of bioluminescence, biofilm formation, type III secretion (TTS), and protease production. The AIs are detected by cognate sensor histidine kinases that all relay phosphate to the shared response regulator LuxO. LuxO indirectly represses the master regulator of quorum sensing, LuxR, through the activation of multiple genes encoding small regulatory RNAs (called qrr genes for Quorum Regulatory RNA). Here we use differential fluorescence induction to identify 50 quorum-sensing-controlled promoters. Some promoters only showed significant responses in the simultaneous presence of all three AIs, while others displayed substantial responses to the individual AIs. A differential response to each AI input state was also observed for qrr and luxR expression and LuxR protein production. Individual cell analyses revealed that, in each case, all the bacteria in the population respond in unison to the various AI inputs. We propose that the V. harveyi quorum-sensing transition is not switch-like but rather operates in a graded manner, and that this signaling arrangement, which uses shared regulatory proteins, nonetheless provides V. harveyi a mechanism to respond uniquely to different AI input states. PMID:17015436

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

    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 on...

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

    Valiente, E.; Bruhn, Jesper Bartholin; Nielsen, Kristian Fog; Larsen, Jens Lauritz; Roig, F. J.; Gram, Lone; Amaro, C.

    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) has...

  12. Ligand Binding Kinetics of the Quorum Sensing Regulator PqsR

    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 and...

  13. Quorum-sensing-regulated virulence factors in Pseudomonas aeruginosa are toxic to Lucilia sericata maggots

    Andersen, A S; Jørgensen, Bo; Bjarnsholt, T;

    2010-01-01

    PAO1 in a simple assay with emphasis on the quorum-sensing (QS)-regulated virulence. The maggots were challenged with GFP-tagged P. aeruginosa wild-type (WT) PAO1 and a GFP-tagged P. aeruginosa DeltalasR rhlR (DeltaRR) QS-deficient mutant in different concentrations. Maggots were killed in the...

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

    Hentzer, Morten; Riedel, K.; Rasmussen, Thomas Bovbjerg; Heydorn, Arne; Andersen, Jens Bo; Parsek, M.R.; Rice, S.A.; Eberl, L.; Molin, Søren; Høiby, N.; Kjelleberg, S.; Givskov, Michael Christian

    2002-01-01

    ). 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...

  15. Quorum sensing-controlled biofilm development in Serratia liquefaciens MG1

    Labbate, M.; Queek, S.Y.; Koh, K.S.; Rice, S.A.; Givskov, Michael Christian; Kjelleberg, S.

    2004-01-01

    aggregates and differentiated cell chains. Signal-based complementation of this mutant resulted in a biofilm with the wild-type architecture. Two quorum-sensing-regulated genes (bsmA and bsmB) involved in biofilm development were identified, and we propose that these genes are engaged in fine-tuning the...

  16. N-acyl-L-homoserine lactone-mediated regulation of the Lip secretion system in Serratia liquefaciens MG1

    Riedel, K.; Ohnesorg, T.; Krogfelt, K.A.;

    2001-01-01

    The analysis of Serratia liquefaciens MG1 'luxAB insertion mutants that are responsive to N-butanoyl-L-homoserine lactone revealed that expression of lipB is controlled by the swr quorum-sensing system. LipB is part of the Lip exporter, a type I secretion system, which is responsible for the secr...

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

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

    2008-01-01

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

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

    Zeena E Nackerdien

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

  19. Maniwamycins: new quorum-sensing inhibitors against Chromobacterium violaceum CV026 were isolated from Streptomyces sp. TOHO-M025.

    Fukumoto, Atsushi; Murakami, Chikana; Anzai, Yojiro; Kato, Fumio

    2016-05-01

    Quorum sensing is an important microbial signaling system that controls the expression of many virulence genes. Maniwamycins C-F, new compounds and quorum-sensing inhibitors, were isolated from the culture broth of Streptomyces sp. TOHO-M025 using a silica gel column and preparative HPLC. The structures of maniwamycins were elucidated by spectroscopic analyses, including NMR. The compounds each have an azoxy moiety. All maniwamycins inhibited violacein synthesis, which is controlled by quorum sensing, in Chromobacterium violaceum CV026. PMID:26648117

  20. A Nitric Oxide-Responsive Quorum Sensing Circuit in Vibrio harveyi Regulates Flagella Production and Biofilm Formation

    Yueming Xu

    2013-08-01

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

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

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

    2013-01-01

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

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

    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

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

    Ruwandeepika, HA 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...

  4. Agaricus Blazei Hot Water Extract Shows Anti Quorum Sensing Activity in the Nosocomial Human Pathogen Pseudomonas Aeruginosa

    Marina Soković; Ana Ćirić; Jasmina Glamočlija; Miloš Nikolić; Van Griensven, Leo 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, biofilm formation and survival of many pathogenic bacteria, including the Gram negative Pseudomonas aeruginosa, and is considered as a novel and promising target for anti-infectious agents. In thi...

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

    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...

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

    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

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

    Arevalo-Ferro, C.; Hentzer, Morten; Reil, G.; Gorg, A.; Kjelleberg, S.; Givskov, Michael Christian; Riedel, K.; Eberl, L.

    2003-01-01

    I double mutant by means of two-dimensional gel electrophoresis (2-DE). This analysis showed that the intensities of 23.7% of all detected protein spots differed more than 2.5-fold between the two strains. We only considered those protein spots truly QS regulated that were changed in the mutant in the......-characterized virulence factors. For one of the identified proteins, the serine protease PrpL, a biochemical assay was established to verify that expression of this factor is indeed QS regulated. Furthermore, it is shown that the quorum-sensing blocker C-30 specifically interferes with the expression of 67% of the AHL......-controlled protein spots of the surface fraction, confirming the high specificity of the compound. Importantly, 20 novel QS-regulated proteins were identified, many of which are involved in iron utilization, suggesting a link between quorum sensing and the iron regulatory system. Two of these proteins, PhuR and Has...

  8. Repellent and Anti-quorum Sensing Activity of Six Aromatic Plants Occurring in Colombia.

    Cervantes-Ceballos, Leonor; Caballero-Gallardo, Karina; Olivero-Verbel, Jesus

    2015-10-01

    Essential oils (EOs) are widely used as biopesticides and to control bacterial infections. This study describes the ability of six EOs isolated from plants cultivated in Colombia to perform as repellents against Ulomoides dermestoides and as quorum sensing (QS) inhibitors. EOs from Aloysia triphylla, Cymbopogon nardus, Lippia origanoides, Hyptis suaveolens, Swinglea glutinosa and Eucalyptus globulus were repellents classified as Class IV, IV, IV, III, II, and II, respectively, whereas the commercial repellent IR3535 only reached Class II after 2 h exposure. All EOs presented small, but significant inhibitory properties against the QS system in Escherichia coli (pJBA132) at 25 μg/mL after 4 h exposure. These data suggest evaluated EOs from Colombia are sustainable, promising new sources of natural repellents and could be important as anti-quorum sensing molecules. PMID:26669119

  9. Quorum-sensing regulation governs bacterial adhesion, biofilm development, and host colonization in Pantoea stewartii subspecies stewartii.

    Koutsoudis, Maria D; Tsaltas, Dimitrios; Minogue, Timothy D; von Bodman, Susanne B

    2006-04-11

    The phytopathogenic bacterium Pantoea stewartii subsp. stewartii synthesizes stewartan exo/capsular polysaccharide (EPS) in a cell density-dependent manner governed by the EsaI/EsaR quorum-sensing (QS) system. This study analyzes biofilm development and host colonization of the WT and QS regulatory mutant strains of P. stewartii. First, we show that the cell density-dependent synthesis of stewartan EPS, governed by the EsaI/EsaR QS system, is required for proper bacterial adhesion and development of spatially defined, 3D biofilms. Second, a nonvirulent mutant lacking the esaI gene adheres strongly to surfaces and develops densely packed, less structurally defined biofilms in vitro. This strain appears to be arrested in a low cell density developmental mode. Exposure of this strain to exogenous N-acyl-homoserine lactone counteracts this adhesion phenotype. Third, QS mutants lacking the EsaR repressor attach poorly to surfaces and form amorphous biofilms heavily enmeshed in excess EPS. Fourth, the WT strain disseminates efficiently within the xylem, primarily in a basipetal direction. In contrast, the two QS mutant strains remain largely localized at the site of infection. Fifth, and most significantly, epifluorescence microscopic imaging of infected leaf tissue and excised xylem vessels reveals that the bacteria colonize the xylem with unexpected specificity, particularly toward the annular rings and spiral secondary wall thickenings of protoxylem, as opposed to indiscriminate growth to fill the xylem lumen. These observations are significant to bacterial plant pathogenesis in general and may reveal targets for disease control. PMID:16585516

  10. Transcriptome-based analysis of the Pantoea stewartii quorum-sensing regulon and identification of EsaR direct targets.

    Ramachandran, Revathy; Burke, Alison Kernell; Cormier, Guy; Jensen, Roderick V; Stevens, Ann M

    2014-09-01

    Pantoea stewartii subsp. stewartii is a proteobacterium that causes Stewart's wilt disease in corn plants. The bacteria form a biofilm in the xylem of infected plants and produce capsule that blocks water transport, eventually causing wilt. At low cell densities, the quorum-sensing (QS) regulatory protein EsaR is known to directly repress expression of esaR itself as well as the genes for the capsular synthesis operon transcription regulator, rcsA, and a 2,5-diketogluconate reductase, dkgA. It simultaneously directly activates expression of genes for a putative small RNA, esaS, the glycerol utilization operon, glpFKX, and another transcriptional regulator, lrhA. At high bacterial cell densities, all of this regulation is relieved when EsaR binds an acylated homoserine lactone signal, which is synthesized constitutively over growth. QS-dependent gene expression is critical for the establishment of disease in the plant. However, the identity of the full set of genes controlled by EsaR/QS is unknown. A proteomic approach previously identified around 30 proteins in the QS regulon. In this study, a whole-transcriptome, next-generation sequencing analysis of rRNA-depleted RNA from QS-proficient and -deficient P. stewartii strains was performed to identify additional targets of EsaR. EsaR-dependent transcriptional regulation of a subset of differentially expressed genes was confirmed by quantitative reverse transcription-PCR (qRT-PCR). Electrophoretic mobility shift assays demonstrated that EsaR directly bound 10 newly identified target promoters. Overall, the QS regulon of P. stewartii orchestrates three major physiological responses: capsule and cell envelope biosynthesis, surface motility and adhesion, and stress response. PMID:25015891

  11. Analysis of quorum sensing-dependent virulence factor production and its relationship with antimicrobial susceptibility in Pseudomonas aeruginosa respiratory isolates.

    Karatuna, O; Yagci, A

    2010-12-01

    Pseudomonas aeruginosa is an opportunistic pathogen causing severe respiratory infections. The pathogenesis of these infections is multifactorial and the production of many virulence factors is regulated by quorum sensing (QS), a cell-to-cell communication mechanism. The two well defined QS systems in P. aeruginosa, the las and rhl systems, rely on N-acyl homoserine lactone signal molecules, also termed autoinducers. We assessed the activity of QS-dependent virulence factors (including elastase, alkaline protease, pyocyanin and biofilm production) in respiratory isolates of P. aeruginosa and their relationship with antimicrobial susceptibility. We identified sixteen isolates displaying impaired phenotypic activity; among them, eleven isolates were also defective in autoinducer production, and therefore considered QS-deficient. Six of the QS-deficient isolates failed to amplify one or more of the four QS regulatory genes (lasI, lasR, rhlI, rhlR) with PCR: one isolate was negative for rhlR, two isolates were negative for rhlI and rhlR and three isolates were negative for all four genes. The isolates that were negative for virulence factor production were generally less susceptible to the antimicrobials and statistically significant correlations were observed between the lack of elastase production and resistance to piperacillin and ceftazidime; between failure in alkaline protease production and resistance to tobramycin, piperacillin, piperacillin-tazobactam, cefepime, imipenem and ciprofloxacin; and between failure in pyocyanin production and resistance to amikacin, tobramycin, ceftazidime, ciprofloxacin and ofloxacin. The results obtained indicate that, despite the pivotal role of QS in the pathogenesis of P. aeruginosa respiratory infections, QS-deficient strains are still capable of causing infections and tend to be less susceptible to antimicrobials. PMID:20132256

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

    Diggle, Stephen P.; Gardner, Andy; West, Stuart A.; Griffin, Ashleigh S.

    2007-01-01

    The term quorum sensing (QS) is used to describe the communication between bacterial cells, whereby a coordinated population response is controlled by diffusible molecules produced by individuals. QS has not only been described between cells of the same species (intraspecies), but also between species (interspecies) and between bacteria and higher organisms (inter-kingdom). The fact that QS-based communication appears to be widespread among microbes is strange, considering that explaining bot...

  13. Bioinformatic Prediction of Gene Functions Regulated by Quorum Sensing in the Bioleaching Bacterium Acidithiobacillus ferrooxidans

    Alvaro Banderas; Nicolas Guiliani

    2013-01-01

    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 bioinforma...

  14. Small Molecules that Modulate Quorum Sensing and Control Virulence in Pseudomonas aeruginosa

    Mattmann, Margrith E.; Blackwell, Helen E.

    2010-01-01

    Bacteria use small molecule signals to access their local population densities in a process called quorum sensing (QS). Once a threshold signal concentration is reached, and therefore a certain number of bacteria have assembled, bacteria use QS to change gene expression levels and initiate behaviors that benefit the group. These group processes play central roles in both bacterial virulence and symbiosis, and can have significant impacts on human health, agriculture, and the environment. The ...

  15. Evidence for Autoinduction and Quorum Sensing in White Band Disease-Causing Microbes on Acropora cervicornis

    Certner, Rebecca H.; Steven V Vollmer

    2015-01-01

    Coral reefs have entered a state of global decline party due to an increasing incidence of coral disease. However, the diversity and complexity of coral-associated bacterial communities has made identifying the mechanisms underlying disease transmission and progression extremely difficult. This study explores the effects of coral cell-free culture fluid (CFCF) and autoinducer (a quorum sensing signaling molecule) on coral-associated bacterial growth and on coral tissue loss respectively. All ...

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

    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.

  17. Quorum sensing communication between bacteria and human cells: signals, targets, and functions

    Holm, Angelika; Vikström, Elena

    2014-01-01

    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...

  18. THE QUORUM SENSING AND THE NODULATION COMPETITIVENESS OF Rhizobia DURING INFECTION OF LEGUMINOUS PLANTS

    N.I. VOROBYOV; N.A. PROVOROV

    2015-01-01

    A basic property of Rhizobia is the ability to compete for nodule formation under a multi strain inoculation. Its regulation remains poorly understood, thus limiting advances in biotechnological studies to improve the effectiveness of Rhizobia microbial preparations. The mathematical model of Rhizobia Nodulation Competitiveness (RNC) for describing a multi strains inoculation of leguminous plants is created (RNC-model). In the RNC-model we took into account that under Quorum Sensing regulatio...

  19. EFFECTS OF PSYCHOTROPIC DRUGS AS BACTERIAL EFFLUX PUMP INHIBITORS ON QUORUM SENSING REGULATED BEHAVIORS

    Aynur Aybey; Alev Usta; Elif Demirkan

    2014-01-01

    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 aga...

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

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

    2005-01-01

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

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

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

    2010-05-19

    Quorum-sensing is the mechanism by which bacteria communicate and synchronize group behaviors. Quantitative information on parameters such as the copy number of particular quorum-sensing proteins should contribute strongly to understanding how the quorum-sensing network functions. Here, we show that the copy number of the master regulator protein LuxR in Vibrio harveyi can be determined in vivo by exploiting small-number fluctuations of the protein distribution when cells undergo division. When a cell divides, both its volume and LuxR protein copy number, N, are partitioned with slight asymmetries. We measured the distribution functions describing the partitioning of the protein fluorescence and the cell volume. The fluorescence distribution is found to narrow systematically as the LuxR population increases, whereas the volume partitioning is unchanged. Analyzing these changes statistically, we determined that N = 80-135 dimers at low cell density and 575 dimers at high cell density. In addition, we measured the static distribution of LuxR over a large (3000) clonal population. Combining the static and time-lapse experiments, we determine the magnitude of the Fano factor of the distribution. This technique has broad applicability as a general in vivo technique for measuring protein copy number and burst size. PMID:20441767

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

    Henke, Jennifer M.; Bassler, Bonnie L.

    2004-01-01

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

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

    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.

  4. 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.

    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. PMID:24268182

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

    Malott Rebecca J

    2009-09-01

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

  6. Quorum sensing in the probiotic bacterium Escherichia coli Nissle 1917 (Mutaflor) – evidence that furanosyl borate diester (AI-2) is influencing the cytokine expression in the DSS colitis mouse model

    Jacobi Christoph A; Grundler Stefanie; Hsieh Chih-Jen; Frick Julia Stefanie; Adam Patrick; Lamprecht Georg; Autenrieth Ingo B; Gregor Michael; Malfertheiner Peter

    2012-01-01

    Abstract Background “Quorum sensing” (QS) is the phenomenon which allows single bacterial cells to measure the concentration of bacterial signal molecules. Two principle different QS systems are known, the Autoinducer 1 system (AI-1) for the intraspecies communication using different Acyl-homoserine lactones (AHL) and AI-2 for the interspecies communication. Aim of this study was to investigate QS of Escherichia coli Nissle 1917 (Mutaflor). Results While E. coli Nissle is producing AI-2 in a ...

  7. Involvement of quorum sensing genes in biofilm development and degradation of polycyclic aromatic hydrocarbons by a marine bacterium Pseudomonas aeruginosa N6P6.

    Mangwani, Neelam; Kumari, Supriya; Das, Surajit

    2015-12-01

    Biofilm-forming and acyl homoserine lactone (AHL) synthase-positive Pseudomonas aeruginosa N6P6 was isolated from seawater after selective enrichment with two polycyclic aromatic hydrocarbons (PAHs), viz. phenanthrene and pyrene. AHL synthesis was detected qualitatively using bioreporter strains. This marine bacterium putatively synthesized N-(3-oxododecanoyl)-L-homoserine lactone and N-butyryl-L-homoserine lactone, which were identified by TLC, GC-MS, and HPLC. Two quorum sensing (QS) genes coding for AHL synthase, i.e., lasI and rhlI, were identified in the bacterium. lasI and rhlI gene expression was studied during biofilm mode of growth at different phases using quantitative real-time PCR (qRT-PCR). The expression of lasI increased with increase in biofilm growth. In contrast, the expression of rhlI decreased during log phase of biofilm growth. The changes in lasI/rhlI expression level had significant effects (Pbiofilm architecture and subsequent PAH degradation rate. Degradation of phenanthrene and pyrene by P. aeruginosa N6P6 was affected by biofilm growth and lasI expression. The respective phenanthrene degradation for 15, 24, 48, and 72 h old biofilm after 7 days was 21.5, 54.2, 85.6, and 85.7%. However, the corresponding pyrene degradation was 15, 18.28, 47.56, and 46.48%, respectively, after 7 days. A significant positive correlation (Pbiofilm formation, and pyocyanin production reduced significantly which confirmed the pivotal role of QS in biodegradation of PAHs. The findings suggest that AHLs play a pivotal role during biofilm development and subsequent bioremediation of PAHs. PMID:26245683

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

    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

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

    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.

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

    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

  11. Pantoea sp. Isolated from Tropical Fresh Water Exhibiting N-Acyl Homoserine Lactone Production

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

    2014-01-01

    N-Acyl homoserine lactone (AHL) serves as signaling molecule for quorum sensing (QS) in Gram-negative bacteria to regulate various physiological activities including pathogenicity. With the aim of isolating freshwater-borne bacteria that can cause outbreak of disease in plants and portrayed QS properties, environmental water sampling was conducted. Here we report the preliminary screening of AHL production using Chromobacterium violaceum CV026 and Escherichia coli [pSB401] as AHL biosensors. ...

  12. Quorum-sensing-regulated virulence factors in Pseudomonas aeruginosa are toxic to Lucilia sericata maggots

    Andersen, A S; Joergensen, B.; Bjarnsholt, T.; Johansen, H; Karlsmark, T.; Givskov, M; Krogfelt, K A

    2010-01-01

    Maggot debridement therapy (MDT) is widely used for debridement of chronic infected wounds; however, for wounds harbouring specific bacteria limited effect or failure of the treatment has been described. Here we studied the survival of Lucilia sericata maggots encountering Pseudomonas aeruginosa PAO1 in a simple assay with emphasis on the quorum-sensing (QS)-regulated virulence. The maggots were challenged with GFP-tagged P. aeruginosa wild-type (WT) PAO1 and a GFP-tagged P. aeruginosa ΔlasR ...

  13. Transsexuality in the Rhizosphere: Quorum Sensing Reversibly Converts Agrobacterium tumefaciens from Phenotypically Female to Male▿

    Cho, Hongbaek; Pinto, Uelinton M.; Winans, Stephen C.

    2009-01-01

    Conjugative plasmids generally encode proteins that block the conjugative entry of identical or similar plasmids into the host cell, a phenomenon known as entry exclusion. Here, we demonstrate that two Ti plasmids of Agrobacterium tumefaciens encode robust entry exclusion functions. Two proteins, TrbJ and TrbK, can each mediate entry exclusion and act synergistically. The trbJ and trbK genes are included within the trb operon, which is tightly regulated by the quorum-sensing regulator TraR an...

  14. Estudio de protocolos de comunicación bacterianos: conjugación y quorum sensing.

    Pardilla Mata, Diego

    2011-01-01

    Los conjuntos bacterianos son sistemas dinámicos complejos, y gracias la interacción que hay, las bacterias coexisten, colaboran, compiten intercambian información. El resultado de estas interconexiones hace que surjan propiedades que no pueden explicarse a partir de una sola célula aislada. Estos comportamientos se denominan propiedades emergentes del sistema. Algunas de las maneras que tienen de interactuar las bacterias son la detección de quórum o quorum sensing y la conjugación. El quoru...

  15. Quorum-sensing signals in the microbial community of the cabbage white butterfly larval midgut

    Borlee, Bradley R; Geske, Grant D.; Robinson, Courtney J.; Blackwell, Helen E.; Handelsman, Jo

    2008-01-01

    The overall goal of this study was to examine the role of quorum-sensing (QS) signals in a multispecies microbial community. Toward this aim, we studied QS signals produced by an indigenous member and an invading pathogen of the microbial community of the cabbage white butterfly (CWB) larval midgut (Pieris rapae). As an initial step, we characterized the QS system in Pantoea CWB304, which was isolated from the larval midgut. A luxI homolog, designated panI, is necessary for the production of ...

  16. Solonamide B Inhibits Quorum Sensing and Reduces Staphylococcus aureus Mediated Killing of Human Neutrophils

    Nielsen, Anita; Månsson, Maria; Bojer, Martin S.;

    2014-01-01

    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.......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...

  17. Piper nigrum, Piper betle and Gnetum gnemon- Natural Food Sources with Anti-Quorum Sensing Properties

    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...

  18. Structure/Function Analysis of the Quorum-sensing Regulator EsaR from the Plant Pathogen Pantoea stewartii

    Schu, Daniel Joseph

    2009-01-01

    Pantoea stewartii subsp. stewarti is the causative agent of Stewartâ s wilt disease in maize. Disease symptoms develop after the bacteria grow to high cell densities in the plant xylem and secrete an abundance of exopolysaccharide (EPS). EPS production is regulated by quorum sensing. Two regulatory proteins are key to the process of quorum sensing, the LuxI and LuxR homologues EsaI and EsaR. Most LuxR homologues function as activators of transcription in the presence of their cognate acylate...

  19. Enterobacter asburiae Strain L1: Complete Genome and Whole Genome Optical Mapping Analysis of a Quorum Sensing Bacterium

    Yin Yin Lau; Wai-Fong Yin; Kok-Gan Chan

    2014-01-01

    Enterobacter asburiae L1 is a quorum sensing bacterium isolated from lettuce leaves. In this study, for the first time, the complete genome of E. asburiae L1 was sequenced using the single molecule real time sequencer (PacBio RSII) and the whole genome sequence was verified by using optical genome mapping (OpGen) technology. In our previous study, E. asburiae L1 has been reported to produce AHLs, suggesting the possibility of virulence factor regulation which is quorum sensing dependent. This...

  20. The AHL- and BDSF-dependent quorum sensing systems control specific and overlapping sets of genes in Burkholderia cenocepacia H111.

    Nadine Schmid

    Full Text Available Quorum sensing in Burkholderia cenocepacia H111 involves two signalling systems that depend on different signal molecules, namely N-acyl homoserine lactones (AHLs and the diffusible signal factor cis-2-dodecenoic acid (BDSF. Previous studies have shown that AHLs and BDSF control similar phenotypic traits, including biofilm formation, proteolytic activity and pathogenicity. In this study we mapped the BDSF stimulon by RNA-Seq and shotgun proteomics analysis. We demonstrate that a set of the identified BDSF-regulated genes or proteins are also controlled by AHLs, suggesting that the two regulons partially overlap. The detailed analysis of two mutually regulated operons, one encoding three lectins and the other one encoding the large surface protein BapA and its type I secretion machinery, revealed that both AHLs and BDSF are required for full expression, suggesting that the two signalling systems operate in parallel. In accordance with this, we show that both AHLs and BDSF are required for biofilm formation and protease production.

  1. Analyzing the Transcriptomes of Two Quorum-Sensing Controlled Transcription Factors, RcsA and LrhA, Important for Pantoea stewartii Virulence.

    Alison Kernell Burke

    Full Text Available The Gram-negative proteobacterium Pantoea stewartii subsp. stewartii causes wilt disease in corn plants. Wilting is primarily due to bacterial exopolysaccharide (EPS production that blocks water transport in the xylem during the late stages of infection. EsaR, the master quorum-sensing (QS regulator in P. stewartii, modulates EPS levels. At low cell densities EsaR represses or activates expression of a number of genes in the absence of its acyl homoserine lactone (AHL ligand. At high cell densities, binding of AHL inactivates EsaR leading to derepression or deactivation of its direct targets. Two of these direct targets are the key transcription regulators RcsA and LrhA, which in turn control EPS production and surface motility/adhesion, respectively. In this study, RNA-Seq was used to further examine the physiological impact of deleting the genes encoding these two second-tier regulators. Quantitative reverse transcription PCR (qRT-PCR was used to validate the regulation observed in the RNA-Seq data. A GFP transcriptional fusion reporter confirmed the existence of a regulatory feedback loop in the system between LrhA and RcsA. Plant virulence assays carried out with rcsA and lrhA deletion and complementation strains demonstrated that both transcription factors play roles during establishment of wilt disease in corn. These efforts further define the hierarchy of the QS-regulated network controlling plant virulence in P. stewartii.

  2. Analyzing the Transcriptomes of Two Quorum-Sensing Controlled Transcription Factors, RcsA and LrhA, Important for Pantoea stewartii Virulence.

    Kernell Burke, Alison; Duong, Duy An; Jensen, Roderick V; Stevens, Ann M

    2015-01-01

    The Gram-negative proteobacterium Pantoea stewartii subsp. stewartii causes wilt disease in corn plants. Wilting is primarily due to bacterial exopolysaccharide (EPS) production that blocks water transport in the xylem during the late stages of infection. EsaR, the master quorum-sensing (QS) regulator in P. stewartii, modulates EPS levels. At low cell densities EsaR represses or activates expression of a number of genes in the absence of its acyl homoserine lactone (AHL) ligand. At high cell densities, binding of AHL inactivates EsaR leading to derepression or deactivation of its direct targets. Two of these direct targets are the key transcription regulators RcsA and LrhA, which in turn control EPS production and surface motility/adhesion, respectively. In this study, RNA-Seq was used to further examine the physiological impact of deleting the genes encoding these two second-tier regulators. Quantitative reverse transcription PCR (qRT-PCR) was used to validate the regulation observed in the RNA-Seq data. A GFP transcriptional fusion reporter confirmed the existence of a regulatory feedback loop in the system between LrhA and RcsA. Plant virulence assays carried out with rcsA and lrhA deletion and complementation strains demonstrated that both transcription factors play roles during establishment of wilt disease in corn. These efforts further define the hierarchy of the QS-regulated network controlling plant virulence in P. stewartii. PMID:26699719

  3. Potent and Selective Modulation of the RhlR Quorum Sensing Receptor by Using Non-native Ligands: An Emerging Target for Virulence Control in Pseudomonas aeruginosa.

    Eibergen, Nora R; Moore, Joseph D; Mattmann, Margrith E; Blackwell, Helen E

    2015-11-01

    Pseudomonas aeruginosa uses N-acylated L-homoserine lactone signals and a triumvirate of LuxR-type receptor proteins--LasR, RhlR, and QscR--for quorum sensing (QS). Each of these receptors can contribute to QS activation or repression and, thereby, the control of myriad virulence phenotypes in this pathogen. LasR has traditionally been considered to be at the top of the QS receptor hierarchy in P. aeruginosa; however, recent reports suggest that RhlR plays a more prominent role in infection than originally predicted, in some circumstances superseding that of LasR. Herein, we report the characterization of a set of synthetic, small-molecule agonists and antagonists of RhlR. Using E. coli reporter strains, we demonstrated that many of these compounds can selectively activate or inhibit RhlR instead of LasR and QscR. Moreover, several molecules maintain their activities in P. aeruginosa at concentrations analogous to native RhlR signal levels. These compounds represent useful chemical probes to study the role of RhlR in the complex QS circuitry of P. aeruginosa, its direct (and indirect) effects on virulence, and its overall merit as a target for anti-infective therapy. PMID:26460240

  4. Time-dependent hormesis of chemical mixtures: A case study on sulfa antibiotics and a quorum-sensing inhibitor of Vibrio fischeri.

    You, Ruirong; Sun, Haoyu; Yu, Yan; Lin, Zhifen; Qin, Mengnan; Liu, Ying

    2016-01-01

    Sulfa antibiotics (SAs) and quorum-sensing inhibitor (QSI) may pose potential ecological risks because mixed using of them has been proposed to inhibit bacteria from generating antibiotic resistance. This study investigated the time-dependent hormesis of single and binary mixtures of QSI and SAs of Vibrio fischeri (V. fischeri) for 0-24 h. Although the low-dose SAs stimulated the expression of LuxR protein, the high-dose SAs could inhibit bacteria growth by competitively binding to dihydropteroate synthase. Moreover, AinR protein was bound to Benzofuran-3(2H)-one (B3O) with low concentration, thus the N-octanoyl homoserine lactone signal molecules (C8) has chance to bind to LuxR protein to promote light emission. The hormesis effect induced by the mixtures could be deduced that SAs promoted the expression of LuxR protein and B3O increases the chance of C8 binding to LuxR. Our findings facilitate new insight into the mechanistic study of hormesis and ecological risks of the chemical mixtures. PMID:26645135

  5. Sub-MICs of Mentha piperita essential oil and menthol inhibits AHL mediated quorum sensing and biofilm of Gram-negative bacteria.

    Husain, Fohad M; Ahmad, Iqbal; Khan, Mohammad S; Ahmad, Ejaz; Tahseen, Qudisa; Khan, Mohd Shahnawaz; Alshabib, Nasser A

    2015-01-01

    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 (PMO) at sub-Minimum Inhibitory Concentrations (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 QS inhibitory activity exhibited by PMO to menthol. Assessment of ability of menthol to interfere with QS 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 Escherichia coli biosensors, MG4/pKDT17 and pEAL08-2, we also confirmed that menthol inhibited both the las and pqs QS 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 QS inhibitor. PMID:26029178

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

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

    2009-01-01

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

  7. Antibiotic resistance profiles and quorum sensing-dependent virulence factors in clinical isolates of pseudomonas aeruginosa.

    Wang, Huafu; Tu, Faping; Gui, Zhihong; Lu, Xianghong; Chu, Weihua

    2013-06-01

    Pseudomonas aeruginosa produces multiple virulence factors that have been associated with quorum sensing. The aim of this study was to evaluate the prevalence of drug resistant profiles and quorum sensing related virulence factors. Pseudomonas aeruginosa were collected from different patients hospitalized in China, the isolates were tested for their susceptibility to different common antimicrobial drugs and detected QS-related virulence factors. We identified 170 isolates displaying impaired phenotypic activity, approximately 80 % of the isolates were found to exhibit the QS-dependent phenotypes, among them, 12 isolates were defective in AHLs production, and therefore considered QS-deficient strains. Resistance was most often observed to Cefazolin (81.2 %), followed by trimethoprim-sulfamethoxazole (73.5 %), ceftriaxone (62.4 %) and Cefotaxime, Levofloxacin, Ciprofloxacin (58.8 %), and to a lesser extent Meropenem (20.0 %), Cefepime (18.8 %), and Cefoperazone/sulbactam (2.4 %) The QS-deficient isolates that were negative for virulence factor production were generally less susceptible to the antimicrobials. The results showed a high incidences of antibiotic resistance and virulence properties in P. aeruginosa, and indicate that the clinical use of QS-inhibitory drugs that appear superior to conventional antimicrobials by not exerting any selective pressure on resistant strains. PMID:24426103

  8. Effect of the quorum-sensing luxS gene on biofilm formation by Enterococcus faecalis.

    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. PMID:27080421

  9. Anti-quorum sensing activity of essential oils from Colombian plants.

    Jaramillo-Colorado, Beatriz; Olivero-Verbel, Jesus; Stashenko, Elena E; Wagner-Döbler, Irene; Kunze, Brigitte

    2012-01-01

    Essential oils from Colombian plants were characterised by GC-MS, and assayed for anti-quorum sensing activity in bacteria sensor strains. Two major chemotypes were found for Lippia alba, the limonene-carvone and the citral (geranial-neral). For other species, the main components included α-pinene (Ocotea sp.), β-pinene (Swinglea glutinosa), cineol (Elettaria cardamomun), α-zingiberene (Zingiber officinale) and pulegone (Minthostachys mollis). Several essential oils presented promising inhibitory properties for the short chain AHL quorum sensing (QS) system, in Escherichia coli containing the biosensor plasmid pJBA132, in particular Lippia alba. Moderate activity as anti-QS using the same plasmid, were also found for selected constituents of essential oils studied here, such as citral, carvone and α-pinene, although solely at the highest tested concentration (250 µg mL(-1)). Only citral presented some activity for the long chain AHL QS system, in Pseudomonas putida containing the plasmid pRK-C12. In short, essential oils from Colombian flora have promising properties as QS modulators. PMID:21936639

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

    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.

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

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

    2004-01-01

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

  12. Manipulation of the Quorum Sensing Signal AI-2 Affects the Antibiotic-Treated Gut Microbiota

    Jessica Ann Thompson

    2015-03-01

    Full Text Available The mammalian gut microbiota harbors a diverse ecosystem where hundreds of bacterial species interact with each other and their host. Given that bacteria use signals to communicate and regulate group behaviors (quorum sensing, we asked whether such communication between different commensal species can influence the interactions occurring in this environment. We engineered the enteric bacterium, Escherichia coli, to manipulate the levels of the interspecies quorum sensing signal, autoinducer-2 (AI-2, in the mouse intestine and investigated the effect upon antibiotic-induced gut microbiota dysbiosis. E. coli that increased intestinal AI-2 levels altered the composition of the antibiotic-treated gut microbiota, favoring the expansion of the Firmicutes phylum. This significantly increased the Firmicutes/Bacteroidetes ratio, to oppose the strong effect of the antibiotic, which had almost cleared the Firmicutes. This demonstrates that AI-2 levels influence the abundance of the major phyla of the gut microbiota, the balance of which is known to influence human health.

  13. Hydnophytum formicarum Jack ethanol extract modulates quorum sensing-controlled pathogenicity in Pseudomonas aeruginosa.

    Hertiani, Triana; Pratiwi, Sylvia Utami Tunjung

    2015-09-01

    The discovery of new mechanism to control microbial pathogenicity by quorum sensing modulation has generated the search for quorum sensing inhibitor from natural resources. The objective of this research was to evaluate the ability of Hydnophytum formicarum Jack (Rubiaceae) ethanol extract to antagonize cell-to cell communication. Pulverized H. formicarum tuber was macerated in ethyl alcohol 96% and evaporated to yield ethanol extract. A dillution technique using Luria-Bertani (LB) medium was used to observe the capability of the extract to reduce the violacein production in Chromobacterium violaceum. Samples in two-fold dilution were prepared to obtain 2 - 0.0625 mg/mL concentration. The effects on swimming, swarming and twitching motility as well as the formation of biofilm towards Pseudomonas aeruginosa PAO1 were recorded over control. All experiments were done in triplicate. The architecture of Ps. aeruginosa biofilm treated with samples was examined by CLSM (Confocal Laser Scanning Microscopy) . Our results suggested that the ethanol extract of H. formicarum caused violacein production inhibition. Furthermore, inhibition of Ps. aeruginosa motility and biofilm formation were recorded to be significant over control in a concentration dependent manner. H. formicarum serves as a potential source for new QS-based antibacterial drugs towards Ps. aeruginosa. PMID:26408889

  14. EFFECTS OF PSYCHOTROPIC DRUGS AS BACTERIAL EFFLUX PUMP INHIBITORS ON QUORUM SENSING REGULATED BEHAVIORS

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

    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

  16. Interference with the germination and growth of Ulva zoospores by quorum-sensing molecules from Ulva-associated epiphytic bacteria.

    Twigg, Matthew S; Tait, Karen; Williams, Paul; Atkinson, Steve; Cámara, Miguel

    2014-02-01

    Ulva zoospores preferentially settle on N-acylhomoserine lactone (AHL) producing marine bacterial biofilms. To investigate whether AHL signal molecules also affect the success and rate of zoospore germination in addition to zoospore attraction, the epiphytic bacteria associated with mature Ulva linza were characterized and bacterial isolates representative of this community tested for the ability to produce AHLs. Two of these AHL-producing isolates, Sulfitobacter spp. 376 and Shewanella spp. 79, were transformed with plasmids expressing the Bacillus spp. AHL lactonase gene aiiA to generate AHL-deficient variants. The germination and growth of U. linza zoospores was studied in the presence of these AHL-deficient strains and their AHL-producing counterparts. This revealed that the AHLs produced by Sulfitobacter spp. and Shewanella spp. or the bacterial products they regulate have a negative impact on both zoospore germination and the early growth of the Ulva germling. Further experiments with Escherichia coli biofilms expressing recombinant AHL synthases and synthetic AHLs provide data to demonstrate that zoospores germinated and grown in the absence of AHLs were significantly longer than those germinated in the presence of AHLs. These results reveal an additional role for AHLs per se in the interactive relationships between marine bacteria and Ulva zoospores. PMID:23879807

  17. Integration host factor and LuxR synergistically bind DNA to coactivate quorum-sensing genes in Vibrio harveyi.

    Chaparian, Ryan R; Olney, Stephen G; Hustmyer, Christine M; Rowe-Magnus, Dean A; van Kessel, Julia C

    2016-09-01

    The cell-cell signaling process called quorum sensing allows bacteria to control behaviors in response to changes in population density. In Vibrio harveyi, the master quorum-sensing transcription factor LuxR is a member of the TetR family of transcription factors that both activates and represses genes to coordinate group behaviors, including bioluminescence. Here, we show that integration host factor (IHF) is a key coactivator of the luxCDABE bioluminescence genes that is required together with LuxR for precise timing and expression levels of bioluminescence during quorum sensing. IHF binds to multiple sites in the luxCDABE promoter and bends the DNA in vitro. IHF and LuxR synergistically bind luxCDABE promoter DNA at overlapping, essential binding sites that are required for maximal gene expression in vivo. RNA-seq analysis demonstrated that IHF regulates 300 genes in V. harveyi, and among these are a core set of 19 genes that are also directly bound and regulated by LuxR. We validated these global analyses by demonstrating that both IHF and LuxR are required for transcriptional activation of the osmotic stress response genes betIBA-proXWV. These data suggest that IHF plays an integral role in one mechanism of transcriptional activation by the LuxR-type family of quorum-sensing regulators in vibrios. PMID:27191515

  18. Small RNA target genes and regulatory connections in the Vibrio cholerae quorum sensing system

    Hammer, Brian K; Svenningsen, Sine Lo

    2011-01-01

    The two-component quorum sensing (QS) system, first described in the marine bacterium Vibrio harveyi and evolutionarily conserved among members of the genus Vibrio, has been best studied in the human pathogen Vibrio cholerae (1, 2). In the V. cholerae QS system, the response to the accumulation of...

  19. Complete Genome Sequence of Pandoraea pnomenusa 3kgm, a Quorum-Sensing Strain Isolated from a Former Landfill Site

    Chan, Kok-Gan; Yin, Wai-Fong; Goh, Share-Yuan

    2014-01-01

    Pandoraea pnomenusa strain 3kgm has been identified as a quorum-sensing strain isolated from soil. Here, we report the complete genome sequence of P. pnomenusa strain 3kgm by using the Pacific Biosciences single-molecule real-time (PacBio RS SMRT) sequencer high-resolution technology.

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

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

    2014-01-01

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

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

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

    2014-01-01

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

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

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

    2014-01-01

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

  3. 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.

    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

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

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

    2014-01-01

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

  5. Garlic blocks quorum sensing and promotes rapid clearing of pulmonary Pseudomonas aeruginosa infections

    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...... garlic-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 cytokine production were used as indicators. The garlic treatment initially provoked a higher degree of inflammation, and significantly improved clearing of the infecting bacteria. The results indicate that a QS-inhibitory extract of garlic renders P. aeruginosa sensitive to tobramycin...

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

    Shen, Jian-Wei

    2011-03-01

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

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

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

  8. Antibiotic-mediated selection of quorum-sensing-negative Staphylococcus aureus

    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 and......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...

  9. In silico structural analysis of quorum sensing genes in Vibrio fischeri

    Mohammed Z Al-khayyat

    2015-09-01

    Full Text Available Quorum sensing controls the luminescence of Vibrio fischeri through the transcriptional activator LuxR and the specific autoinducer signal produced by luxI. Amino acid sequences of these two genes were analyzed using bioinformatics tools. LuxI consists of 193 amino acids and appears to contain five α-helices and six ß-sheets when analyzed by SSpro8. LuxI belongs to the autoinducer synthetase family and contains an acetyltransferase domain extending from residues 24 to 110 as MOTIF predicted. LuxR, on the other hand, contains 250 amino acids and has ten α-helices and four ß-sheets. MOTIF predicted LuxR to possess functional motifs; the inducer binding site extending from amino acid residues 23 to 147 and the LuxR activator site extending between amino acids 182 and 236. The InterProScan5 server identified a winged helix-turn-helix DNA binding motif.

  10. Piper nigrum, Piper betle and Gnetum gnemon- Natural Food Sourcewith Anti-Quorum Sensing Properties

    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.

  11. Herbs, Spices and Medicinal Plants Used In Hispanic Traditional Medicine Can Decrease Quorum Sensing Dependent Virulence in Pseudomonas aeruginosa

    V Huerta

    2008-06-01

    Full Text Available Summary: Inhibition of quorum sensing (QS, a cell density dependent regulation of bacterial virulent gene expression by autoinducers (AI is an attractive strategy for the discovery of novel antimicrobials and overcome antibiotic resistance. Pseudomonas aeruginosa (PAO1, an opportunistic pathogen in immune compromised patients is under the regulation of the LasR-RhlR system for its QS mediated development of virulence. Natural products have recently become a promising source for deriving molecules that can potentially inhibit quorum sensing.  Herbs, Spices and Medicinal Plants (HSMP used in Hispanic cultures have been used for treating common ailments for many centuries. However, few studies have investigated its QS related antivirulent activities. Our objective was to determine the ability of 25 popular Hispanic HSMP on the expression of QS regulated virulence factors in PAO1. Effect of these extracts on QS mediated PAO1 virulent factors pyocyanin, elastase, and total proteolytic activity were quantified by standard protocols. Results indicated that several extracts reduced pyocyanin synthesis, with some extracts completely inhibiting its formation and secretion. The extracts that decreased the pyocyanin formation also decreased the expression and activity of elastase and other proteolytic enzymes important for the virulence. We observed that HSMP from Central/South American countries can inhibit QS dependent and independent virulent processes in PA-O1. Further research into the exact mechanism of action can lead to better understanding and discovery of new category of drugs and strategies for the management of PAO1 infections and antimicrobial resistance.   Industrial relevance: Quorum sensing is an important process involved in bacterial survival and infections, recent research has focused on the development of therapeutic agents which prevent or manage bacterial pathogenesis by inhibiting bacterial QS. Inhibition of quorum sensing offers an

  12. Quorum Sensing-Disrupting Brominated Furanones Protect the Gnotobiotic Brine Shrimp Artemia franciscana from Pathogenic Vibrio harveyi, Vibrio campbellii, and Vibrio parahaemolyticus Isolates†

    Defoirdt, Tom; Crab, Roselien; Wood, Thomas K.; Sorgeloos, Patrick; Verstraete, Willy; Bossier, Peter

    2006-01-01

    Autoinducer 2 (AI-2) quorum sensing was shown before to regulate the virulence of Vibrio harveyi towards the brine shrimp Artemia franciscana. In this study, several different pathogenic V. harveyi, Vibrio campbellii, and Vibrio parahaemolyticus isolates were shown to produce AI-2. Furthermore, disruption of AI-2 quorum sensing by a natural and a synthetic brominated furanone protected gnotobiotic Artemia from the pathogenic isolates in in vivo challenge tests.

  13. Quorum Sensing-Disrupting Brominated Furanones Protect the Gnotobiotic Brine Shrimp Artemia franciscana from Pathogenic Vibrio harveyi, Vibrio campbellii, and Vibrio parahaemolyticus Isolates†

    Defoirdt, Tom; Crab, Roselien; Wood, Thomas K.; Sorgeloos, Patrick; Verstraete, Willy; Bossier, Peter

    2006-01-01

    Autoinducer 2 (AI-2) quorum sensing was shown before to regulate the virulence of Vibrio harveyi towards the brine shrimp Artemia franciscana. In this study, several different pathogenic V. harveyi, Vibrio campbellii, and Vibrio parahaemolyticus isolates were shown to produce AI-2. Furthermore, disruption of AI-2 quorum sensing by a natural and a synthetic brominated furanone protected gnotobiotic Artemia from the pathogenic isolates in in vivo challenge tests. PMID:16957276

  14. Solid‐Phase Synthesis and Biological Evaluation of N‐Dipeptido L‐Homoserine Lactones as Quorum Sensing Activators

    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...... released through an efficient acid‐mediated cyclative release mechanism. Subsequent screening for modulation of QS in Pseudomonas aeruginosa and E. coli identified six moderately strong activators. A follow‐up library designed from the preliminary derived structure–activity relationships was synthesized...

  15. A simple model for the early events of quorum sensing in Pseudomonas aeruginosa: modeling bacterial swarming as the movement of an "activation zone"

    Venturi Vittorio

    2009-02-01

    Full Text Available Abstract Background Quorum sensing (QS is a form of gene regulation based on cell-density that depends on inter-cellular communication. While there are a variety of models for bacterial colony morphology, there is little work linking QS genes to movement in an open system. Results The onset of swarming in environmental P. aeruginosa PUPa3 was described with a simplified computational model in which cells in random motion communicate via a diffusible signal (representing N-acyl homoserine lactones, AHL as well as diffusible, secreted factors (enzymes, biosurfactans, i.e. "public goods" that regulate the intensity of movement and metabolism in a threshold-dependent manner. As a result, an "activation zone" emerges in which nutrients and other public goods are present in sufficient quantities, and swarming is the spontaneous displacement of this high cell-density zone towards nutrients and/or exogenous signals. The model correctly predicts the behaviour of genomic knockout mutants in which the QS genes responsible either for the synthesis (lasI, rhlI or the sensing (lasR, rhlR of AHL signals were inactivated. For wild type cells the model predicts sustained colony growth that can however be collapsed by the overconsumption of nutrients. Conclusion While in more complex models include self-orienting abilities that allow cells to follow concentration gradients of nutrients and chemotactic agents, in this model, displacement towards nutrients or environmental signals is an emergent property of the community that results from the action of a few, well-defined QS genes and their products. Still the model qualitatively describes the salient properties of QS bacteria, i.e. the density-dependent onset of swarming as well as the response to exogenous signals or cues. Reviewers This paper was reviewed by Gáspár Jékely, L. Aravind, Eugene V. Koonin and Artem Novozhilov (nominated by Eugene V. Koonin.

  16. Inhibition of biofilm development and spoilage potential of Shewanella baltica by quorum sensing signal in cell-free supernatant from Pseudomonas fluorescens.

    Zhao, Aifei; Zhu, Junli; Ye, Xiaofeng; Ge, Yangyang; Li, Jianrong

    2016-08-01

    The objective of this study was to in vitro evaluate the effect of a cell-free supernatant (CFS) containing quorum sensing (QS) signal of Pseudomonas fluorescens on the growth, biofilm development and spoilage potential of Shewanella baltica, and preliminarily assess the interactive influences of various chemically synthesized autoinducers on spoilage phenotypes of S. baltica. PF01 strain isolated from spoiled Pseudosciaen crocea was identified P. fluorescens. The addition of 25% and 50% CFS to S. baltica culture had no effect on the growth rate during the lag and exponential phase, however, caused cell decline during the stationary phase. The presence of CFS from P. fluorescens significantly inhibited biofilm development, and greatly decreased the production of trimethylamine (TMA) and biogenic amino in S. baltica. Various signal molecules of QS in the CFS of P. fluorescens culture were detected, including seven N-acyl-l-homoserine lactones (AHLs), autoinducer-2 (AI-2) and two diketopiperazines (DKPs). Exogenous supplement of synthesized seven AHLs containing in the CFS decreased biofilm formation and TMA production in S. baltica, while exposure to exogenous cyclo-(l-Pro-l-Leu) was showed to promote spoilage potential, which revealed that S. baltica also sense the two QS molecules. Furthermore, the stimulating effect of cyclo-(l-Pro-l-Leu) was affected when AHL was simultaneously added, suggesting that the inhibitory activity of spoilage phenotypes in S. baltica might be attributed to a competitive effect of these QS compounds in the CFS of P. fluorescens. The present studies provide a good basis for future research on the role of QS in the regulation of spoilage microbial flora. PMID:27149651

  17. The Crystal Structure of Burkholderia cenocepacia DfsA Provides Insights into Substrate Recognition and Quorum Sensing Fatty Acid Biosynthesis.

    Spadaro, Francesca; Scoffone, Viola C; Chiarelli, Laurent R; Fumagalli, Marco; Buroni, Silvia; Riccardi, Giovanna; Forneris, Federico

    2016-06-14

    Burkholderia cenocepacia is a major concern among respiratory tract infections in cystic fibrosis patients. This pathogen is particularly difficult to treat because of its high level of resistance to the clinically relevant antimicrobial agents. In B. cenocepacia, the quorum sensing cell-cell communication system is involved in different processes that are important for bacterial virulence, such as biofilm formation and protease and siderophore production. Targeting the enzymes involved in this process represents a promising therapeutic approach. With the aim of finding effective quorum sensing inhibitors, we have determined the three-dimensional structure of B. cenocepacia diffusible factor synthase A, DfsA. This bifunctional crotonase (dehydratase/thioesterase) produces the characteristic quorum sensing molecule of B. cenocepacia, cis-2-dodecenoic acid or BDSF, starting from 3-hydroxydodecanoyl-acyl carrier protein. Unexpectedly, the crystal structure revealed the presence of a lipid molecule in the catalytic site of the enzyme, which was identified as dodecanoic acid. Our biochemical characterization shows that DfsA is able to use dodecanoyl-acyl carrier protein as a substrate, demonstrating that dodecanoic acid, the product of this reaction, is released very slowly from the DfsA active site, therefore acting as a DfsA inhibitor. This molecule shows an unprecedented conformational arrangement inside the DfsA active site. In contrast with previous hypotheses, our data illustrate how DfsA and closely related homologous enzymes can recognize long hydrophobic substrates without large conformational changes or assistance by additional regulator molecules. The elucidation of the substrate binding mode in DfsA provides the starting point for structure-based drug discovery studies targeting B. cenocepacia quorum sensing-assisted virulence. PMID:27198181

  18. Effect of Cinnamon Oil on Quorum Sensing-Controlled Virulence Factors and Biofilm Formation in Pseudomonas aeruginosa

    Manmohit Kalia; Vivek Kumar Yadav; Pradeep Kumar Singh; Deepmala Sharma; Himanshu Pandey; Shahid Suhail Narvi; Vishnu Agarwal

    2015-01-01

    Quorum sensing (QS) is a system of stimuli and responses in bacterial cells governed by their population density, through which they regulate genes that control virulence factors and biofilm formation. Despite considerable research on QS and the discovery of new antibiotics, QS-controlled biofilm formation by microorganisms in clinical settings has remained a problem because of nascent drug resistance, which requires screening of diverse compounds for anti-QS activities. Cinnamon is a dietary...

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

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

    2008-01-01

    Background The light-emitting Vibrios provide excellent material for studying the interaction of cellular communication with growth rate because bioluminescence is a convenient marker for quorum sensing. However, the use of bioluminescence as a marker is complicated because bioluminescence itself may affect growth rate, e.g. by diverting energy. Methodology/Principal Findings The marker effect was explored via growth rate studies in isogenic Vibrio harveyi (Vh) strains altered in quorum sensi...

  20. Quorum Sensing Signaling Molecules Produced by Reference and Emerging Soft-Rot Bacteria (Dickeya and Pectobacterium spp.)

    Crepin, Alexandre; Barbey, Corinne; Beury-Cirou, Amelie; Hélias, Valerie; Taupin, Laure; Reverchon, Sylvie; Nasser, William; Faure, Denis; Dufour, Alain; Orange, Nicole; Feuilloley, Marc; Heurlier, Karin; Burini, Jean-Francois; Latour, Xavier

    2012-01-01

    Background: Several small diffusible molecules are involved in bacterial quorum sensing and virulence. The production of autoinducers-1 and -2, quinolone, indole and gamma-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 c...

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

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

    2008-01-01

    BACKGROUND: The light-emitting Vibrios provide excellent material for studying the interaction of cellular communication with growth rate because bioluminescence is a convenient marker for quorum sensing. However, the use of bioluminescence as a marker is complicated because bioluminescence itself may affect growth rate, e.g. by diverting energy. METHODOLOGY/PRINCIPAL FINDINGS: The marker effect was explored via growth rate studies in isogenic Vibrio harveyi (Vh) strains altered in quorum sen...

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

    Singh, Ravindra Pal; Baghel, Ravi S.; Reddy, C. R. K.; Jha, Bhavanath

    2015-01-01

    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 (QS) 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 w...

  3. Biopelículas como expresión del mecanismo de quorum sensing: Una revisión Biofilms like expression of quorum sensing mechanism: A revision

    A.J. Díaz Caballero

    2011-12-01

    Full Text Available En la periodoncia moderna, el concepto de biopelículas viene en un progreso tan abrumador que la capacidad de discusión se hace necesaria y completamente indispensable, de forma que se pueda actualizar y cambiar de una idea de placa bacteriana a un concepto mucho más complejo, dinámico y de intercambio génico que lo que se viene estableciendo. Las biopelículas muestran una organización no al azar, con una forma de crecimiento y de sostenibilidad muy avanzada y estructurada que facilita la supervivencia de los patógenos incluidos dentro de estas formas de asociación. El presente artículo es una revisión narrativa de los mecanismos de como el quórum sensing y las biopelículas se relacionan con las enfermedades periodontales que afectan a tantas personas en todas las latitudes a nivel mundial. Se exploran diversos conceptos y campos de investigación biomédicas con posibles aplicaciones a nivel experimental.In modern periodontics, we must check continuously many concepts that are driving some time, which does not allow the progress and development of many structures of thinking in solving problems such as periodontal disease in all its various forms presentation. The concept of biofilms is in progress so overwhelming that the ability of discussion is completely necessary and indispensable, so that you can update and change a plaque idea to a concept much more complex, dynamic, and that genetic exchange what has been established to date. Biofilms are a non-random, is a form of growth and sustainability quite advanced and structured to facilitate the survival of the pathogens included in these partnerships. This article is a narrative review, mechanisms such as quorum sensing, biofilms and the relationship of these with periodontal diseases that affect many people at all latitudes worldwide. It explores various concepts and research areas with potential application in biomedical experimentation level.

  4. Characterization of phenotype variations of luminescent and non-luminescent variants of Vibrio harveyi wild type and quorum sensing mutants.

    Hong, N T X; Baruah, K; Vanrompay, D; Bossier, P

    2016-03-01

    Vibrio harveyi, a luminescent Gram-negative motile marine bacterium, is an important pathogen responsible for causing severe diseases in shrimp, finfish and molluscs leading to severe economic losses. Non-luminescent V. harveyi obtained by culturing luminescent strains under static and dark condition were reported to alter the levels of virulence factors and metalloprotease gene and luxR expression when compared to their luminescent variants. Presently, we conducted an in vitro study aiming at the characterization of virulence-related phenotypic traits of the wild-type V. harveyi BB120 strain and its isogenic quorum sensing mutants before and after switching to the non-luminescent status. We measured the production of caseinase, haemolysin and elastase and examined swimming motility and biofilm formation. Our results showed that switching from the bioluminescent to the non-luminescent state changed the phenotypic physiology or behaviour of V. harveyi resulting in alterations in caseinase and haemolytic activities, swimming motility and biofilm formation. The switching capacity was to a large extent independent from the quorum sensing status, in that quorum sensing mutants were equally capable of making the phenotypic switch. PMID:25865123

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

    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. PMID:26789904

  6. Oxidative DNA damage protective activity, antioxidant and anti-quorum sensing potentials of Moringa oleifera.

    Singh, Brahma N; Singh, B R; Singh, R L; Prakash, D; Dhakarey, R; Upadhyay, G; Singh, H B

    2009-06-01

    The aqueous extract of leaf (LE), fruit (FE) and seed (SE) of Moringa oleifera was assessed to examine the ability to inhibit the oxidative DNA damage, antioxidant and anti-quorum sensing (QS) potentials. It was found that these extracts could significantly inhibit the OH-dependent damage of pUC18 plasmid DNA and also inhibit synergistically with trolox, with an activity sequence of LE > FE > SE. HPLC and MS/MS analysis was carried out, which showed the presence of gallic acid, chlorogenic acid, ellagic acid, ferulic acid, kaempferol, quercetin and vanillin. The LE was with comparatively higher total phenolics content (105.04 mg gallic acid equivalents (GAE)/g), total flavonoids content (31.28 mg quercetin equivalents (QE)/g), and ascorbic acid content (106.95 mg/100 g) and showed better antioxidant activity (85.77%), anti-radical power (74.3), reducing power (1.1 ascorbic acid equivalents (ASE)/ml), inhibition of lipid peroxidation, protein oxidation, OH-induced deoxyribose degradation, and scavenging power of superoxide anion and nitric oxide radicals than did the FE, SE and standard alpha-tocopherol. Eventually, LE and FE were found to inhibit violacein production, a QS-regulated behavior in Chromobacterium violaceum 12472. PMID:19425184

  7. Surface enhanced Raman scattering for detection of Pseudomonas aeruginosa quorum sensing compounds

    Thrift, Will; Bhattacharjee, Arunima; Darvishzadeh-Varcheie, Mahsa; Lu, Ying; Hochbaum, Allon; Capolino, Filippo; Whiteson, Katrine; Ragan, Regina

    2015-08-01

    Pseudomonas aeruginosa (PA), a biofilm forming bacterium, commonly affects cystic fibrosis, burn victims, and immunocompromised patients. PA produces pyocyanin, an aromatic, redox active, secondary metabolite as part of its quorum sensing signaling system activated during biofilm formation. Surface enhanced Raman scattering (SERS) sensors composed of Au nanospheres chemically assembled into clusters on diblock copolymer templates were fabricated and the ability to detect pyocyanin to monitor biofilm formation was investigated. Electromagnetic full wave simulations of clusters observed in scanning electron microcopy images show that the localized surface plasmon resonance wavelength is 696 nm for a dimer with a gap spacing of 1 nm in an average dielectric environment of the polymer and analyte; the local electric field enhancement is on the order of 400 at resonance, relative to free space. SERS data acquired at 785 nm excitation from a monolayer of benzenethiol on fabricated samples was compared with Raman data of pure benzenethiol and enhancement factors as large as 8×109 were calculated that are consistent with simulated field enhancements. Using this system, the limit of detection of pyocyanin in pure gradients was determined to be 10 parts per billion. In SERS data of the supernatant from the time dependent growth of PA shaking cultures, pyocyanin vibrational modes were clearly observable during the logarithmic growth phase corresponding to activation of genes related to biofilm formation. These results pave the way for the use of SERS sensors for the early detection of biofilm formation, leading to reduced healthcare costs and better patient outcomes.

  8. Bioinformatic Prediction of Gene Functions Regulated by Quorum Sensing in the Bioleaching Bacterium Acidithiobacillus ferrooxidans

    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.

  9. Evidence for Autoinduction and Quorum Sensing in White Band Disease-Causing Microbes on Acropora cervicornis

    Certner, Rebecca H.; Vollmer, Steven V.

    2015-06-01

    Coral reefs have entered a state of global decline party due to an increasing incidence of coral disease. However, the diversity and complexity of coral-associated bacterial communities has made identifying the mechanisms underlying disease transmission and progression extremely difficult. This study explores the effects of coral cell-free culture fluid (CFCF) and autoinducer (a quorum sensing signaling molecule) on coral-associated bacterial growth and on coral tissue loss respectively. All experiments were conducted using the endangered Caribbean coral Acropora cervicornis. Coral-associated microbes were grown on selective media infused with CFCF derived from healthy and white band disease-infected A. cervicornis. Exposure to diseased CFCF increased proliferation of Cytophaga-Flavobacterium spp. while exposure to healthy CFCF inhibited growth of this group. Exposure to either CFCF did not significantly affect Vibrio spp. growth. In order to test whether disease symptoms can be induced in healthy corals, A. cervicornis was exposed to bacterial assemblages supplemented with exogenous, purified autoinducer. Incubation with autoinducer resulted in complete tissue loss in all corals tested in less than one week. These findings indicate that white band disease in A. cervicornis may be caused by opportunistic pathogenesis of resident microbes.

  10. The LuxS based quorum sensing governs lactose induced biofilm formation by Bacillus subtilis

    Danielle eDuanis-Assaf

    2016-01-01

    Full Text Available Bacillus species present a major concern in the dairy industry as they can form biofilms in pipelines and on surfaces of equipment and machinery used in the entire line of production. These biofilms represent a continuous hygienic problem and can lead to serious economic losses due to food spoilage and equipment impairment. Biofilm formation by Bacillus subtilis is apparently dependent on LuxS quorum sensing (QS by Autoinducer-2 (AI-2. However, the link between sensing environmental cues and AI-2 induced biofilm formation remains largely unknown. The aim of this study is to investigate the role of lactose, the primary sugar in milk, on biofilm formation by B. subtilis and its possible link to QS processes. Our phenotypic analysis shows that lactose induces formation of biofilm bundles as well as formation of colony type biofilms. Furthermore, using reporter strain assays, we observed an increase in AI-2 production by B. subtilis in response to lactose in a dose dependent manner. Moreover, we found that expression of eps and tapA operons, responsible for extracellular matrix synthesis in B. subtilis, were notably up-regulated in response to lactose. Importantly, we also observed that LuxS is essential for B. subtilis biofilm formation in the presence of lactose. Overall, our results suggest that lactose may induce biofilm formation by B. subtilis through the LuxS pathway.

  11. Structure, Regulation, and Inhibition of the Quorum-Sensing Signal Integrator LuxO.

    Boyaci, Hande; Shah, Tayyab; Hurley, Amanda; Kokona, Bashkim; Li, Zhijie; Ventocilla, Christian; Jeffrey, Philip D; Semmelhack, Martin F; Fairman, Robert; Bassler, Bonnie L; Hughson, Frederick M

    2016-05-01

    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. PMID:27219477

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

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

    2014-02-01

    Device-related infection remains a major barrier to the use of biomaterial implants as life-saving devices. This study aims to examine the effectiveness and mechanism of action of surface attached dihydropyrrolones (DHPs), a quorum sensing (QS) inhibitor, against bacterial colonization. DHPs were covalently attached on glass surfaces via copper-catalyzed azide-alkyne 1,3-dipolar cycloaddition (CuAAC) click reaction. The covalent attachment of DHP surfaces was confirmed by X-ray photoelectron spectroscopy (XPS) and contact angle measurements, and the antimicrobial efficacy of the DHP coatings was assessed by confocal laser scanning microscopy (CLSM) and image analysis. The results demonstrated that covalently bound DHP compounds are effective in reducing the adhesion by up to 97% (p technology, it is demonstrated that surface attached DHPs were able to repress the expression of a lasB-gfp reporter fusion of P. aeruginosa by 72% (p viability. This demonstrates the ability of the covalently bound QS inhibitor to inhibit QS and suggests the existence of a membrane-based pathway(s) for QS inhibition. Hence, strategies based on incorporation of QS inhibitors such as DHPs represent a potential approach for prevention of device-related infections. PMID:24345737

  13. Synthetic Quorum Sensing and Induced Aggregation in Model Microcapsule Colonies with Repressilator Feedback

    Shum, Henry; Yashin, Victor; Balazs, Anna

    We model a system of synthetic microcapsules that communicate chemically by releasing nanoparticles or signaling molecules. These signaling species bind to receptors on the shells of capsules and modulate the target shell's permeability, thereby controlling nanoparticle release from the target capsule. Using the repressilator regulatory network motif, whereby three species suppress the production of the next in a cyclic fashion, we show that large amplitude oscillations in nanoparticle release can emerge when many capsules are close together. This exemplifies quorum sensing, which is the ability of cells to gauge their population density and collectively initiate a new behavior once a critical density is reached. We present a physically realizable model in which the oscillations exhibited in crowded populations induce aggregation of the microcapsules, mimicking complex biological behavior of the slime mold Dictyostelium discoideum with only simple, synthetic components. We also show that the clusters can be dispersed and reformed repeatedly and controllably by addition of chemical stimuli, demonstrating possible applications in creating reconfigurable or programmable materials.

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

    SHEN Jian-Wei

    2011-01-01

    Bacterial quorum sensing (QS) has attracted much interests and it is an important process of cell communication.Recently, Bassler et al.studied the phenomena of QS regulated by small RNAs and the experimental data showed that small RNAs played important role in the QS of Vibrio harveyi and it can permit the fine-tuning of gene regulation and maintenance of homeostasis.According to Michaelis-Menten kinetics and mass action law in this paper,we construct a mathematical model to investigate the mechanism induced QS by coexist of small RNA and signal molecular (Al) and show that there are periodic oscillation when the time delay and Hill coefficient exceed a critical value and the periodic oscillation produces the change of concentration and induces QS.These results are fit to the experimental results.In the meanwhile, we also get some theoretical value of Hopf Bifurcation on time deday.In addition, we also find this network is robust against noise.PACS numbers: 05.45.-a

  15. Structure, Regulation, and Inhibition of the Quorum-Sensing Signal Integrator LuxO

    Hurley, Amanda; Li, Zhijie; Ventocilla, Christian; Jeffrey, Philip D.; Semmelhack, Martin F.; Fairman, Robert; Bassler, Bonnie L.; Hughson, Frederick M.

    2016-01-01

    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. PMID:27219477

  16. Understanding of aerobic granulation enhanced by starvation in the perspective of quorum sensing.

    Liu, Xiang; Sun, Supu; Ma, Buyun; Zhang, Chen; Wan, Chunli; Lee, Duu-Jong

    2016-04-01

    Three sequencing batch reactors (M1, M2, and M3) were set up to investigate the influence of different lengths of starvation time (3, 5, and 7 h) on aerobic granulation in the perspective of quorum sensing (QS). Autoinducer-2 (AI-2) level was quantified to evaluate the QS ability of aerobic granules. The results indicated that AI-2 level increased steadily during a cycle of sequencing batch reactors, suggesting that starvation was closely related to AI-2 secretion. In the long-term operation, aerobic granules cultivated using a prolonged starvation period had a better integrity and a higher level of cell adhesiveness despite a slower formation speed. With the extension of the starvation period, the total amount of extracellular polymeric substances (EPS) displayed an increasing tendency. EPS with large molecular weight (MW) also reached a higher level using a prolonged starvation period. However, a higher level of AI-2 and cell adhesiveness was observed in M2, which might be related to more stable granules. The results implied that the starvation period could trigger AI-2 secretion and promoted the production of large MW EPS, leading to cell adhesiveness enhancement and granule formation. Therefore, a combination of different starvation periods was proposed in this study in order to improve aerobic granulation. PMID:26695156

  17. Bioinformatic prediction of gene functions regulated by quorum sensing in the bioleaching bacterium Acidithiobacillus ferrooxidans.

    Banderas, Alvaro; Guiliani, Nicolas

    2013-01-01

    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. PMID:23959118

  18. Programmed Lab Experiments for Biochemical Investigation of Quorum-Sensing Signal Molecules in Rhizospheric Soil Bacteria.

    Nievas, Fiorela L; Bogino, Pablo C; Giordano, Walter

    2016-05-01

    Biochemistry courses in the Department of Molecular Biology at the National University of Río Cuarto, Argentina, are designed for undergraduate students in biology, microbiology, chemistry, agronomy, and veterinary medicine. Microbiology students typically have previous coursework in general, analytical, and organic chemistry. Programmed sequences of lab experiments allow these students to investigate biochemical problems whose solution is feasible within the context of their knowledge and experience. We previously designed and reported a programmed lab experiment that familiarizes microbiology students with techniques for detection and characterization of quorum-sensing (QS) and quorum-quenching (QQ) signal molecules. Here, we describe a sequence of experiments designed to expand the understanding and capabilities of biochemistry students using techniques for extraction and identification of QS and QQ signal molecules from peanut rhizospheric soil bacteria, including culturing and manipulation of bacteria under sterile conditions. The program provides students with an opportunity to perform useful assays, draw conclusions from their results, and discuss possible extensions of the study. © 2016 by The International Union of Biochemistry and Molecular Biology, 44:256-262, 2016. PMID:27027267

  19. Inhibition of Bacterial Quorum Sensing by Extracts from Aquatic Fungi: First Report from Marine Endophytes

    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.

  20. Microbiome shifts and the inhibition of quorum sensing by Black Band Disease cyanobacteria.

    Meyer, Julie L; Gunasekera, Sarath P; Scott, Raymond M; Paul, Valerie J; Teplitski, Max

    2016-05-01

    Disruption of the microbiome often correlates with the appearance of disease symptoms in metaorganisms such as corals. In Black Band Disease (BBD), a polymicrobial disease consortium dominated by the filamentous cyanobacterium Roseofilum reptotaenium displaces members of the epibiotic microbiome. We examined both normal surface microbiomes and BBD consortia on Caribbean corals and found that the microbiomes of healthy corals were dominated by Gammaproteobacteria, in particular Halomonas spp., and were remarkably stable across spatial and temporal scales. In contrast, the microbial community structure in black band consortia was more variable and more diverse. Nevertheless, deep sequencing revealed that members of the disease consortium were present in every sampled surface microbiome of Montastraea, Orbicella and Pseudodiploria corals, regardless of the health status. Within the BBD consortium, we identified lyngbic acid, a cyanobacterial secondary metabolite. It strongly inhibited quorum sensing (QS) in the Vibrio harveyi QS reporters. The effects of lyngbic acid on the QS reporters depended on the presence of the CAI-1 receptor CqsS. Lyngbic acid inhibited luminescence in native coral Vibrio spp. that also possess the CAI-1-mediated QS. The effects of this naturally occurring QS inhibitor on bacterial regulatory networks potentially contribute to the structuring of the interactions within BBD consortia. PMID:26495995

  1. Genes as early responders regulate quorum-sensing and control bacterial cooperation in Pseudomonas aeruginosa.

    Kelei Zhao

    Full Text Available Quorum-sensing (QS allows bacterial communication to coordinate the production of extracellular products essential for population fitness at higher cell densities. It has been generally accepted that a significant time duration is required to reach appropriate cell density to activate the relevant quiescent genes encoding these costly but beneficial public goods. Which regulatory genes are involved and how these genes control bacterial communication at the early phases are largely un-explored. By determining time-dependent expression of QS-related genes of the opportunistic pathogen Pseudomonas aerugionsa, we show that the induction of social cooperation could be critically influenced by environmental factors to optimize the density of population. In particular, small regulatory RNAs (RsmY and RsmZ serving as early responders, can promote the expression of dependent genes (e.g. lasR to boost the synthesis of intracellular enzymes and coordinate instant cooperative behavior in bacterial cells. These early responders, acting as a rheostat to finely modulate bacterial cooperation, which may be quickly activated under environment threats, but peter off when critical QS dependent genes are fully functional for cooperation. Our findings suggest that RsmY and RsmZ critically control the timing and levels of public goods production, which may have implications in sociomicrobiology and infection control.

  2. Quorum sensing protects bacterial co-operation from exploitation by cheats.

    Allen, Richard C; McNally, Luke; Popat, Roman; Brown, Sam P

    2016-07-01

    Quorum sensing (QS) is a cell-cell communication system found in many bacterial species, commonly controlling secreted co-operative traits, including extracellular digestive enzymes. We show that the canonical QS regulatory architecture allows bacteria to sense the genotypic composition of high-density populations, and limit co-operative investments to social environments enriched for co-operators. Using high-density populations of the opportunistic pathogen Pseudomonas aeruginosa we map per-capita signal and co-operative enzyme investment in the wild type as a function of the frequency of non-responder cheats. We demonstrate mathematically and experimentally that the observed response rule of 'co-operate when surrounded by co-operators' allows bacteria to match their investment in co-operation to the composition of the group, therefore allowing the maintenance of co-operation at lower levels of population structuring (that is, lower relatedness). Similar behavioural responses have been described in vertebrates under the banner of 'generalised reciprocity'. Our results suggest that mechanisms of reciprocity are not confined to taxa with advanced cognition, and can be implemented at the cellular level via positive feedback circuits. PMID:26744811

  3. Single cell analysis of Vibrio harveyi uncovers functional heterogeneity in response to quorum sensing signals

    Anetzberger Claudia

    2012-09-01

    Full Text Available Abstract Background Vibrio harveyi and closely related species are important pathogens in aquaculture. A complex quorum sensing cascade involving three autoinducers controls bioluminescence and several genes encoding virulence factors. Single cell analysis of a V. harveyi population has already indicated intercellular heterogeneity in the production of bioluminescence. This study was undertaken to analyze the expression of various autoinducer-dependent genes in individual cells. Results Here we used reporter strains bearing promoter::gfp fusions to monitor the induction/repression of three autoinducer-regulated genes in wild type conjugates at the single cell level. Two genes involved in pathogenesis - vhp and vscP, which code for an exoprotease and a component of the type III secretion system, respectively, and luxC (the first gene in the lux operon were chosen for analysis. The lux operon and the exoprotease gene are induced, while vscP is repressed at high cell density. As controls luxS and recA, whose expression is not dependent on autoinducers, were examined. The responses of the promoter::gfp fusions in individual cells from the same culture ranged from no to high induction. Importantly, simultaneous analysis of two autoinducer induced phenotypes, bioluminescence (light detection and exoproteolytic activity (fluorescence of a promoter::gfp fusion, in single cells provided evidence for functional heterogeneity within a V. harveyi population. Conclusions Autoinducers are not only an indicator for cell density, but play a pivotal role in the coordination of physiological activities within the population.

  4. Flavonoids from Piper delineatum modulate quorum-sensing-regulated phenotypes in Vibrio harveyi.

    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. PMID:26070141

  5. Negative Feedback Loops Involving Small Regulatory RNAs Precisely Control the Vibrio harveyi Quorum-Sensing Response

    Tu, Kimberly C.; Long, Tao; Svenningsen, Sine L.; Wingreen, Ned S.; Bassler, Bonnie L.

    2010-01-01

    Summary Quorum sensing (QS) bacteria assess population density through secretion and detection of molecules called autoinducers (AIs). We identify and characterize two Vibrio harveyi negative feedback loops that facilitate precise transitions between low-cell-density (LCD) and high-cell-density (HCD) states. The QS central regulator LuxO autorepresses its own transcription and the Qrr small regulatory RNAs (sRNAs) posttranscriptionally repress luxO. Disrupting feedback increases the concentration of AIs required for cells to transit from LCD to HCD QS modes. Thus, the two cooperative negative feedback loops determine the point at which V. harveyi has reached a quorum and control the range of AIs over which the transition occurs. Negative feedback regulation also constrains the range of QS output – by preventing sRNA levels from becoming too high and preventing luxO mRNA levels from reaching zero. We suggest that sRNA-mediated feedback regulation is a network design feature that permits fine-tuning of gene regulation and maintenance of homeostasis. PMID:20188674

  6. Discovery of a nitric oxide responsive quorum sensing circuit in Vibrio harveyi.

    Henares, Bernadette M; Higgins, Kate E; Boon, Elizabeth M

    2012-08-17

    Bacteria use small molecules to assess the density and identity of nearby organisms and formulate a response. This process, called quorum sensing (QS), commonly regulates bioluminescence, biofilm formation, and virulence. Vibrio harveyi have three described QS circuits. Each involves the synthesis of a molecule that regulates phosphorylation of its cognate receptor kinase. Each receptor exchanges phosphate with a common phosphorelay protein, LuxU, which ultimately regulates bioluminescence. Here, we show that another small molecule, nitric oxide (NO), participates in QS through LuxU. V. harveyi display a NO concentration-dependent increase in bioluminescence that is regulated by an hnoX gene. We demonstrate that H-NOX is a NO sensor and NO/H-NOX regulates phosphorylation of a kinase that transfers phosphate to LuxU. This study reveals the discovery of a fourth QS pathway in V. harveyi and suggests that bacteria use QS to integrate not only the density of bacteria but also other diverse information about their environment into decisions about gene expression. PMID:22606970

  7. A small-RNA-mediated negative feedback loop controls quorum-sensing dynamics in Vibrio harveyi

    Tu, Kimberly C; Waters, Christopher M; Svenningsen, Sine L; Bassler, Bonnie L

    2008-01-01

    The bioluminescent marine bacterium Vibrio harveyi uses a cell-to-cell communication process called quorum sensing (QS) to co-ordinate behaviours in response to changes in population density. QS is accomplished through the secretion and detection of extracellular signalling molecules called autoinducers. At the centre of the V. harveyi QS circuit are five small regulatory RNAs called Qrr1–5 which destabilize the mRNA of luxR, encoding LuxR, the master transcriptional regulator of QS target genes. Here we show that LuxR directly activates transcription of qrr2, qrr3 and qrr4, leading to the rapid downregulation of luxR. The LuxR-binding sites in the promoters of qrr2, qrr3 and qrr4 were identified and mutated to determine the consequences of this regulatory loop on QS dynamics. Disruption of the loop delays the transition from high to low cell density, and more significantly, decreases the cell density at which the population reaches a quorum. Our results suggest that feedback is essential for optimizing the dynamics of the transitions between individual and group behaviours. PMID:18808382

  8. Broad spectrum pro-quorum-sensing molecules as inhibitors of virulence in vibrios.

    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. PMID:22761573

  9. Broad spectrum pro-quorum-sensing molecules as inhibitors of virulence in vibrios.

    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.

  10. Synthetic Quorum Sensing and Cell-Cell Communication in Gram-Positive Bacillus megaterium.

    Marchand, Nicholas; Collins, Cynthia H

    2016-07-15

    The components of natural quorum-sensing (QS) systems can be used to engineer synthetic communication systems that regulate gene expression in response to chemical signals. We have used the machinery from the peptide-based agr QS system from Staphylococcus aureus to engineer a synthetic QS system in Bacillus megaterium to enable autoinduction of a target gene at high cell densities. Growth and gene expression from these synthetic QS cells were characterized in both complex and minimal media. We also split the signal production and sensing components between two strains of B. megaterium to produce sender and receiver cells and characterized the resulting communication in liquid media and on semisolid agar. The system described in this work represents the first synthetic QS and cell-cell communication system that has been engineered to function in a Gram-positive host, and it has the potential to enable the generation of dynamic gene regulatory networks in B. megaterium and other Gram-positive organisms. PMID:26203497

  11. Inhibition of quorum sensing regulated biofilm formation in Serratia marcescens causing nosocomial infections.

    Bakkiyaraj, Dhamodharan; Sivasankar, Chandran; Pandian, Shunmugiah Karutha

    2012-05-01

    Serratia marcescens is an opportunistic pathogen causing severe urinary tract infections in hospitalized individuals. Infections of S. marcescens are of great concern because of its increasing resistance towards conventional antibiotics. Quorum sensing (QS)-a cell to cell communication-system of S. marcescens acts as a global regulator of almost all the virulence factors and majorly its biofilm formation. Since, the QS system of S. marcescens directly accords to its pathogenesis, targeting QS system will provide an improved strategy to combat drug resistant pathogens. In the present study, QS system of S. marcescens has been used as target and its inhibition has been studied upon exposure to bioactives from coral associated bacteria (CAB). This study also emphasises the potential of CAB in producing bioactive agents with anti-QS and antibiofilm properties. Two CAB isolates CAB 23 and 41 have shown to inhibit biofilm formation and the production of QS dependent virulence factors like prodigiosin, protease, lipase and swarming motility. The study, on the whole explicates the potential of QS system as a target to treat drug resistant bacterial infections. PMID:22487181

  12. The transcriptional regulator CzcR modulates antibiotic resistance and quorum sensing in Pseudomonas aeruginosa.

    Dieppois, Guennaëlle; Ducret, Véréna; Caille, Olivier; Perron, Karl

    2012-01-01

    The opportunistic pathogen Pseudomonas aeruginosa responds to zinc, cadmium and cobalt by way of the CzcRS two-component system. In presence of these metals the regulatory protein CzcR induces the expression of the CzcCBA efflux pump, expelling and thereby inducing resistance to Zn, Cd and Co. Importantly, CzcR co-regulates carbapenem antibiotic resistance by repressing the expression of the OprD porin, the route of entry for these antibiotics. This unexpected co-regulation led us to address the role of CzcR in other cellular processes unrelated to the metal response. We found that CzcR affected the expression of numerous genes directly involved in the virulence of P. aeruginosa even in the absence of the inducible metals. Notably the full expression of quorum sensing 3-oxo-C12-HSL and C4-HSL autoinducer molecules is impaired in the absence of CzcR. In agreement with this, the virulence of the czcRS deletion mutant is affected in a C. elegans animal killing assay. Additionally, chromosome immunoprecipitation experiments allowed us to localize CzcR on the promoter of several regulated genes, suggesting a direct control of target genes such as oprD, phzA1 and lasI. All together our data identify CzcR as a novel regulator involved in the control of several key genes for P. aeruginosa virulence processes. PMID:22666466

  13. The transcriptional regulator CzcR modulates antibiotic resistance and quorum sensing in Pseudomonas aeruginosa.

    Guennaëlle Dieppois

    Full Text Available The opportunistic pathogen Pseudomonas aeruginosa responds to zinc, cadmium and cobalt by way of the CzcRS two-component system. In presence of these metals the regulatory protein CzcR induces the expression of the CzcCBA efflux pump, expelling and thereby inducing resistance to Zn, Cd and Co. Importantly, CzcR co-regulates carbapenem antibiotic resistance by repressing the expression of the OprD porin, the route of entry for these antibiotics. This unexpected co-regulation led us to address the role of CzcR in other cellular processes unrelated to the metal response. We found that CzcR affected the expression of numerous genes directly involved in the virulence of P. aeruginosa even in the absence of the inducible metals. Notably the full expression of quorum sensing 3-oxo-C12-HSL and C4-HSL autoinducer molecules is impaired in the absence of CzcR. In agreement with this, the virulence of the czcRS deletion mutant is affected in a C. elegans animal killing assay. Additionally, chromosome immunoprecipitation experiments allowed us to localize CzcR on the promoter of several regulated genes, suggesting a direct control of target genes such as oprD, phzA1 and lasI. All together our data identify CzcR as a novel regulator involved in the control of several key genes for P. aeruginosa virulence processes.

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

    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.

  15. A quorum sensing small volatile molecule promotes antibiotic tolerance in bacteria.

    Yok-Ai Que

    Full Text Available Bacteria can be refractory to antibiotics due to a sub-population of dormant cells, called persisters that are highly tolerant to antibiotic exposure. The low frequency and transience of the antibiotic tolerant "persister" trait has complicated elucidation of the mechanism that controls antibiotic tolerance. In this study, we show that 2' Amino-acetophenone (2-AA, a poorly studied but diagnostically important small, volatile molecule produced by the recalcitrant gram-negative human pathogen Pseudomonas aeruginosa, promotes antibiotic tolerance in response to quorum-sensing (QS signaling. Our results show that 2-AA mediated persister cell accumulation occurs via alteration of the expression of genes involved in the translational capacity of the cell, including almost all ribosomal protein genes and other translation-related factors. That 2-AA promotes persisters formation also in other emerging multi-drug resistant pathogens, including the non 2-AA producer Acinetobacter baumannii implies that 2-AA may play an important role in the ability of gram-negative bacteria to tolerate antibiotic treatments in polymicrobial infections. Given that the synthesis, excretion and uptake of QS small molecules is a common hallmark of prokaryotes, together with the fact that the translational machinery is highly conserved, we posit that modulation of the translational capacity of the cell via QS molecules, may be a general, widely distributed mechanism that promotes antibiotic tolerance among prokaryotes.

  16. Individual and combined roles of the master regulators AphA and LuxR in control of the Vibrio harveyi quorum-sensing regulon.

    van Kessel, Julia C; Rutherford, Steven T; Shao, Yi; Utria, Alan F; Bassler, Bonnie L

    2013-02-01

    Bacteria use a chemical communication process called quorum sensing to control transitions between individual and group behaviors. In the Vibrio harveyi quorum-sensing circuit, two master transcription factors, AphA and LuxR, coordinate the quorum-sensing response. Here we show that AphA regulates 167 genes, LuxR regulates 625 genes, and they coregulate 77 genes. LuxR strongly controls genes at both low cell density and high cell density, suggesting that it is the major quorum-sensing regulator. In contrast, AphA is absent at high cell density and acts to fine-tune quorum-sensing gene expression at low cell density. We examined two loci as case studies of coregulation by AphA and LuxR. First, AphA and LuxR directly regulate expression of the genes encoding the quorum-regulatory small RNAs Qrr2, Qrr3, and Qrr4, the consequence of which is a specifically timed transition between the individual and the group life-styles. Second, AphA and LuxR repress type III secretion system genes but at different times and to different extents. The consequence of this regulation is that type III secretion is restricted to a peak at mid-cell density. Thus, the asymmetric production of AphA and LuxR coupled with differences in their strengths and timing of target gene regulation generate a precise temporal pattern of gene expression. PMID:23204455

  17. Cold Plasma Inactivation of Bacterial Biofilms and Reduction of Quorum Sensing Regulated Virulence Factors.

    Dana Ziuzina

    Full Text Available The main objectives of this work were to investigate the effect of atmospheric cold plasma (ACP against a range of microbial biofilms commonly implicated in foodborne and healthcare associated human infections and against P. aeruginosa quorum sensing (QS-regulated virulence factors, such as pyocyanin, elastase (Las B and biofilm formation capacity post-ACP treatment. The effect of processing factors, namely treatment time and mode of plasma exposure on antimicrobial activity of ACP were also examined. Antibiofilm activity was assessed for E. coli, L. monocytogenes and S. aureus in terms of reduction of culturability and retention of metabolic activity using colony count and XTT assays, respectively. All samples were treated 'inpack' using sealed polypropylene containers with a high voltage dielectric barrier discharge ACP generated at 80 kV for 0, 60, 120 and 300 s and a post treatment storage time of 24 h. According to colony counts, ACP treatment for 60 s reduced populations of E. coli to undetectable levels, whereas 300 s was necessary to significantly reduce populations of L. monocytogenes and S. aureus biofilms. The results obtained from XTT assay indicated possible induction of viable but non culturable state of bacteria. With respect to P. aeruginosa QS-related virulence factors, the production of pyocyanin was significantly inhibited after short treatment times, but reduction of elastase was notable only after 300 s and no reduction in actual biofilm formation was achieved post-ACP treatment. Importantly, reduction of virulence factors was associated with reduction of the cytotoxic effects of the bacterial supernatant on CHO-K1 cells, regardless of mode and duration of treatment. The results of this study point to ACP technology as an effective strategy for inactivation of established biofilms and may play an important role in attenuation of virulence of pathogenic bacteria. Further investigation is warranted to propose direct evidence

  18. Cold Plasma Inactivation of Bacterial Biofilms and Reduction of Quorum Sensing Regulated Virulence Factors

    Ziuzina, Dana; Boehm, Daniela; Patil, Sonal; Cullen, P. J.; Bourke, Paula

    2015-01-01

    The main objectives of this work were to investigate the effect of atmospheric cold plasma (ACP) against a range of microbial biofilms commonly implicated in foodborne and healthcare associated human infections and against P. aeruginosa quorum sensing (QS)-regulated virulence factors, such as pyocyanin, elastase (Las B) and biofilm formation capacity post-ACP treatment. The effect of processing factors, namely treatment time and mode of plasma exposure on antimicrobial activity of ACP were also examined. Antibiofilm activity was assessed for E. coli, L. monocytogenes and S. aureus in terms of reduction of culturability and retention of metabolic activity using colony count and XTT assays, respectively. All samples were treated ‘inpack’ using sealed polypropylene containers with a high voltage dielectric barrier discharge ACP generated at 80 kV for 0, 60, 120 and 300 s and a post treatment storage time of 24 h. According to colony counts, ACP treatment for 60 s reduced populations of E. coli to undetectable levels, whereas 300 s was necessary to significantly reduce populations of L. monocytogenes and S. aureus biofilms. The results obtained from XTT assay indicated possible induction of viable but non culturable state of bacteria. With respect to P. aeruginosa QS-related virulence factors, the production of pyocyanin was significantly inhibited after short treatment times, but reduction of elastase was notable only after 300 s and no reduction in actual biofilm formation was achieved post-ACP treatment. Importantly, reduction of virulence factors was associated with reduction of the cytotoxic effects of the bacterial supernatant on CHO-K1 cells, regardless of mode and duration of treatment. The results of this study point to ACP technology as an effective strategy for inactivation of established biofilms and may play an important role in attenuation of virulence of pathogenic bacteria. Further investigation is warranted to propose direct evidence for the

  19. Quorum sensing coordinates brute force and stealth modes of infection in the plant pathogen Pectobacterium atrosepticum.

    Hui Liu

    2008-06-01

    Full Text Available Quorum sensing (QS in vitro controls production of plant cell wall degrading enzymes (PCWDEs and other virulence factors in the soft rotting enterobacterial plant pathogen Pectobacterium atrosepticum (Pba. Here, we demonstrate the genome-wide regulatory role of QS in vivo during the Pba-potato interaction, using a Pba-specific microarray. We show that 26% of the Pba genome exhibited differential transcription in a QS (expI- mutant, compared to the wild-type, suggesting that QS may make a greater contribution to pathogenesis than previously thought. We identify novel components of the QS regulon, including the Type I and II secretion systems, which are involved in the secretion of PCWDEs; a novel Type VI secretion system (T6SS and its predicted substrates Hcp and VgrG; more than 70 known or putative regulators, some of which have been demonstrated to control pathogenesis and, remarkably, the Type III secretion system and associated effector proteins, and coronafacoyl-amide conjugates, both of which play roles in the manipulation of plant defences. We show that the T6SS and a novel potential regulator, VirS, are required for full virulence in Pba, and propose a model placing QS at the apex of a regulatory hierarchy controlling the later stages of disease progression in Pba. Our findings indicate that QS is a master regulator of phytopathogenesis, controlling multiple other regulators that, in turn, co-ordinately regulate genes associated with manipulation of host defences in concert with the destructive arsenal of PCWDEs that manifest the soft rot disease phenotype.

  20. Chemical Inhibition of Kynureninase Reduces Pseudomonas aeruginosa Quorum Sensing and Virulence Factor Expression.

    Kasper, Stephen H; Bonocora, Richard P; Wade, Joseph T; Musah, Rabi Ann; Cady, Nathaniel C

    2016-04-15

    The opportunistic pathogen Pseudomonas aeruginosa utilizes multiple quorum sensing (QS) pathways to coordinate an arsenal of virulence factors. We previously identified several cysteine-based compounds inspired by natural products from the plant Petiveria alliacea which are capable of antagonizing multiple QS circuits as well as reducing P. aeruginosa biofilm formation. To understand the global effects of such compounds on virulence factor production and elucidate their mechanism of action, RNA-seq transcriptomic analysis was performed on P. aeruginosa PAO1 exposed to S-phenyl-l-cysteine sulfoxide, the most potent inhibitor from the prior study. Exposure to this inhibitor down-regulated expression of several QS-regulated virulence operons (e.g., phenazine biosynthesis, type VI secretion systems). Interestingly, many genes that were differentially regulated pertain to the related metabolic pathways that yield precursors of pyochelin, tricarboxylic acid cycle intermediates, phenazines, and Pseudomonas quinolone signal (PQS). Activation of the MexT-regulon was also indicated, including the multidrug efflux pump encoded by mexEF-oprN, which has previously been shown to inhibit QS and pathogenicity. Deeper investigation of the metabolites involved in these systems revealed that S-phenyl-l-cysteine sulfoxide has structural similarity to kynurenine, a precursor of anthranilate, which is critical for P. aeruginosa virulence. By supplementing exogenous anthranilate, the QS-inhibitory effect was reversed. Finally, it was shown that S-phenyl-l-cysteine sulfoxide competitively inhibits P. aeruginosa kynureninase (KynU) activity in vitro and reduces PQS production in vivo. The kynurenine pathway has been implicated in P. aeruginosa QS and virulence factor expression; however, this is the first study to show that targeted inhibition of KynU affects P. aeruginosa gene expression and QS, suggesting a potential antivirulence strategy. PMID:26785289

  1. Development of a mimotope vaccine targeting the Staphylococcus aureus quorum sensing pathway.

    John P O'Rourke

    Full Text Available A major hurdle in vaccine development is the difficulty in identifying relevant target epitopes and then presenting them to the immune system in a context that mimics their native conformation. We have engineered novel virus-like-particle (VLP technology that is able to display complex libraries of random peptide sequences on a surface-exposed loop in the coat protein without disruption of protein folding or VLP assembly. This technology allows us to use the same VLP particle for both affinity selection and immunization, integrating the power of epitope discovery and epitope mimicry of traditional phage display with the high immunogenicity of VLPs. Previously, we showed that using affinity selection with our VLP platform identifies linear epitopes of monoclonal antibodies and subsequent immunization generates the proper antibody response. To test if our technology could identify immunologic mimotopes, we used affinity selection on a monoclonal antibody (AP4-24H11 that recognizes the Staphylococcus aureus autoinducing peptide 4 (AIP4. AIP4 is a secreted eight amino acid, cyclized peptide produced from the S. aureus accessory gene regulator (agrIV quorum-sensing operon. The agr system coordinates density dependent changes in gene expression, leading to the upregulation of a host of virulence factors, and passive transfer of AP4-24H11 protects against S. aureus agrIV-dependent pathogenicity. In this report, we identified a set of peptides displayed on VLPs that bound with high specificity to AP4-24H11. Importantly, similar to passive transfer with AP4-24H11, immunization with a subset of these VLPs protected against pathogenicity in a mouse model of S. aureus dermonecrosis. These data are proof of principle that by performing affinity selection on neutralizing antibodies, our VLP technology can identify peptide mimics of non-linear epitopes and that these mimotope based VLP vaccines provide protection against pathogens in relevant animal models.

  2. Development of a mimotope vaccine targeting the Staphylococcus aureus quorum sensing pathway.

    O'Rourke, John P; Daly, Seth M; Triplett, Kathleen D; Peabody, David; Chackerian, Bryce; Hall, Pamela R

    2014-01-01

    A major hurdle in vaccine development is the difficulty in identifying relevant target epitopes and then presenting them to the immune system in a context that mimics their native conformation. We have engineered novel virus-like-particle (VLP) technology that is able to display complex libraries of random peptide sequences on a surface-exposed loop in the coat protein without disruption of protein folding or VLP assembly. This technology allows us to use the same VLP particle for both affinity selection and immunization, integrating the power of epitope discovery and epitope mimicry of traditional phage display with the high immunogenicity of VLPs. Previously, we showed that using affinity selection with our VLP platform identifies linear epitopes of monoclonal antibodies and subsequent immunization generates the proper antibody response. To test if our technology could identify immunologic mimotopes, we used affinity selection on a monoclonal antibody (AP4-24H11) that recognizes the Staphylococcus aureus autoinducing peptide 4 (AIP4). AIP4 is a secreted eight amino acid, cyclized peptide produced from the S. aureus accessory gene regulator (agrIV) quorum-sensing operon. The agr system coordinates density dependent changes in gene expression, leading to the upregulation of a host of virulence factors, and passive transfer of AP4-24H11 protects against S. aureus agrIV-dependent pathogenicity. In this report, we identified a set of peptides displayed on VLPs that bound with high specificity to AP4-24H11. Importantly, similar to passive transfer with AP4-24H11, immunization with a subset of these VLPs protected against pathogenicity in a mouse model of S. aureus dermonecrosis. These data are proof of principle that by performing affinity selection on neutralizing antibodies, our VLP technology can identify peptide mimics of non-linear epitopes and that these mimotope based VLP vaccines provide protection against pathogens in relevant animal models. PMID:25379726

  3. Quorum sensing-regulated chitin metabolism provides grazing resistance to Vibrio cholerae biofilms.

    Sun, Shuyang; Tay, Qi Xiang Martin; Kjelleberg, Staffan; Rice, Scott A; McDougald, Diane

    2015-08-01

    Association of Vibrio cholerae with chitinous surfaces of zooplankton is important for its persistence in marine environments, as it provides accessibility to nutrients and resistance to stresses. Predation by heterotrophic protists has a major impact on the survival of V. cholerae. V. cholerae forms biofilms as its main defensive strategy, and quorum sensing (QS) additionally regulates the production of antiprotozoal factors. The role of chitin and QS regulation in V. cholerae grazing resistance was investigated by exposing V. cholerae wild-type (WT) and QS mutant biofilms grown on chitin flakes to the bacteriotrophic, surface-feeding flagellate Rhynchomonas nasuta. V. cholerae formed more biofilm biomass on chitin flakes compared with nonchitinous surfaces. The growth of R. nasuta was inhibited by WT biofilms grown on chitin flakes, whereas the inhibition was attenuated in QS mutant biofilms. The chitin-dependent toxicity was also observed when the V. cholerae biofilms were developed under continuous flow or grown on a natural chitin source, the exoskeleton of Artemia. In addition, the antiprotozoal activity and ammonium concentration of V. cholerae biofilm supernatants were quantified. The ammonium levels (3.5 mM) detected in the supernatants of V. cholerae WT biofilms grown on chitin flakes were estimated to reduce the number of R. nasuta by >80% in add-back experiments, and the supernatant of QS mutant biofilms was less toxic owing to a decrease in ammonium production. Transcriptomic analysis revealed that the majority of genes involved in chitin metabolism and chemotaxis were significantly downregulated in QS mutant biofilms when grown on chitin compared with the WT biofilms. PMID:25615438

  4. Interference of quorum sensing in urinary pathogen Serratia marcescens by Anethum graveolens.

    Salini, Ramesh; Pandian, Shunmugiah Karutha

    2015-08-01

    Serratia marcescens is an opportunistic turned obligate pathogen frequently associated with urinary tract infections (UTI) and are multidrug resistant at most instances. Quorum sensing (QS) system, a population-dependent global regulatory system, controls the pathogenesis machinery of S. marcescens as it does in other pathogens. In the present study, methanol extract of a common herb and spice, Anethum graveolens (AGME) was assessed for its anti-QS potential against the clinical isolate of S. marcescens. AGME notably reduced the biofilm formation and QS-dependent virulence factors production in a concentration-dependent manner (64-1024 μg mL(-1)). The light and confocal microscopic images clearly evidenced the antibiofilm activity of AGME (256 μg mL(-1)) at its minimal biofilm inhibitory concentration. Besides, in support of biochemical assays, the expression analysis of QS-regulated genes fimC, bsmA and flhD which are crucial for initial adhesion and motility confirmed their downregulation upon exposure to AGME. LC-MS analysis of AGME revealed 3-O-methyl ellagic acid (3-O-ME) as one of its active principles having nearly similar antibiofilm activity and a reduced inhibition of prodigiosin (27%) and protease (15%) compared to AGME [prodigiosin (47%) and protease (50%)]. UFLC analysis revealed that 0.355 mg g(-1) of 3-O-ME was present in the AGME. AGME and the 3-O-ME significantly interfered the QS system of a QS model strain S. marcescens MG1 and its mutant S. marcescens MG44 which in turn corroborates the anti-QS mechanism of AGME. PMID:26013821

  5. Quercetin sensitizes fluconazole-resistant candida albicans to induce apoptotic cell death by modulating quorum sensing.

    Singh, B N; Upreti, D K; Singh, B R; Pandey, G; Verma, S; Roy, S; Naqvi, A H; Rawat, A K S

    2015-04-01

    Quorum sensing (QS) regulates group behaviors of Candida albicans such as biofilm, hyphal growth, and virulence factors. The sesquiterpene alcohol farnesol, a QS molecule produced by C. albicans, is known to regulate the expression of virulence weapons of this fungus. Fluconazole (FCZ) is a broad-spectrum antifungal drug that is used for the treatment of C. albicans infections. While FCZ can be cytotoxic at high concentrations, our results show that at much lower concentrations, quercetin (QC), a dietary flavonoid isolated from an edible lichen (Usnea longissima), can be implemented as a sensitizing agent for FCZ-resistant C. albicans NBC099, enhancing the efficacy of FCZ. QC enhanced FCZ-mediated cell killing of NBC099 and also induced cell death. These experiments indicated that the combined application of both drugs was FCZ dose dependent rather than QC dose dependent. In addition, we found that QC strongly suppressed the production of virulence weapons-biofilm formation, hyphal development, phospholipase, proteinase, esterase, and hemolytic activity. Treatment with QC also increased FCZ-mediated cell death in NBC099 biofilms. Interestingly, we also found that QC enhances the anticandidal activity of FCZ by inducing apoptotic cell death. We have also established that this sensitization is reliant on the farnesol response generated by QC. Molecular docking studies also support this conclusion and suggest that QC can form hydrogen bonds with Gln969, Thr1105, Ser1108, Arg1109, Asn1110, and Gly1061 in the ATP binding pocket of adenylate cyclase. Thus, this QS-mediated combined sensitizer (QC)-anticandidal agent (FCZ) strategy may be a novel way to enhance the efficacy of FCZ-based therapy of C. albicans infections. PMID:25645848

  6. Endophytic Bacteria Isolated from Common Bean (Phaseolus vulgaris) Exhibiting High Variability Showed Antimicrobial Activity and Quorum Sensing Inhibition.

    Lopes, Ralf Bruno Moura; Costa, Leonardo Emanuel de Oliveira; Vanetti, Maria Cristina Dantas; de Araújo, Elza Fernandes; de Queiroz, Marisa Vieira

    2015-10-01

    Endophytic bacteria play a key role in the biocontrol of phytopathogenic microorganisms. In this study, genotypic diversity was analyzed via repetitive element PCR (rep-PCR) of endophytic isolates of the phylum Actinobacteria that were previously collected from leaves of cultivars of common bean (Phaseolus vulgaris). Considerable variability was observed, which has not been reported previously for this phylum of endophytic bacteria of the common bean. Furthermore, the ethanol extracts from cultures of various isolates inhibited the growth of pathogenic bacteria in vitro, especially Gram-positive pathogens. Extracts from cultures of Microbacterium testaceum BAC1065 and BAC1093, which were both isolated from the 'Talismã' cultivar, strongly inhibited most of the pathogenic bacteria tested. Bean endophytic bacteria were also demonstrated to have the potential to inhibit the quorum sensing of Gram-negative bacteria. This mechanism may regulate the production of virulence factors in pathogens. The ability to inhibit quorum sensing has also not been reported previously for endophytic microorganisms of P. vulgaris. Furthermore, M. testaceum with capacity to inhibit quorum sensing appears to be widespread in common bean. The genomic profiles of M. testaceum were also analyzed via pulsed-field gel electrophoresis, and greater differentiation was observed using this method than rep-PCR; in general, no groups were formed based on the cultivar of origin. This study showed for the first time that endophytic bacteria from common bean plants exhibit high variability and may be useful for the development of strategies for the biological control of diseases in this important legume plant. PMID:26202846

  7. Quorum sensing in Escherichia coli, Salmonella typhimurium, and Vibrio harveyi: A new family of genes responsible for autoinducer production

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

    1999-01-01

    In bacteria, the regulation of gene expression in response to changes in cell density is called quorum sensing. Quorum-sensing bacteria produce, release, and respond to hormone-like molecules (autoinducers) that accumulate in the external environment as the cell population grows. In the marine bacterium Vibrio harveyi two parallel quorum-sensing systems exist, and each is composed of a sensor–autoinducer pair. V. harveyi reporter strains capable of detecting only autoinducer 1 (AI-1) or autoinducer 2 (AI-2) have been constructed and used to show that many species of bacteria, including Escherichia coli MG1655, E. coli O157:H7, Salmonella typhimurium 14028, and S. typhimurium LT2 produce autoinducers similar or identical to the V. harveyi system 2 autoinducer AI-2. However, the domesticated laboratory strain E. coli DH5α does not produce this signal molecule. Here we report the identification and analysis of the gene responsible for AI-2 production in V. harveyi, S. typhimurium, and E. coli. The genes, which we have named luxSV.h., luxSS.t., and luxSE.c. respectively, are highly homologous to one another but not to any other identified gene. E. coli DH5α can be complemented to AI-2 production by the introduction of the luxS gene from V. harveyi or E. coli O157:H7. Analysis of the E. coli DH5α luxSE.c. gene shows that it contains a frameshift mutation resulting in premature truncation of the LuxSE.c. protein. Our results indicate that the luxS genes define a new family of autoinducer-production genes. PMID:9990077

  8. Marine organisms as source of extracts to disrupt bacterial communication: bioguided isolation and identification of quorum sensing inhibitors from Ircinia felix

    Jairo Quintana

    2015-06-01

    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. Quorum-sensing regulation governs bacterial adhesion, biofilm development, and host colonization in Pantoea stewartii subspecies stewartii

    Koutsoudis, Maria D.; Tsaltas, Dimitrios; Minogue, Timothy D.; von Bodman, Susanne B.

    2006-01-01

    The phytopathogenic bacterium Pantoea stewartii subsp. stewartii synthesizes stewartan exo/capsular polysaccharide (EPS) in a cell density-dependent manner governed by the EsaI/EsaR quorum-sensing (QS) system. This study analyzes biofilm development and host colonization of the WT and QS regulatory mutant strains of P. stewartii. First, we show that the cell density-dependent synthesis of stewartan EPS, governed by the EsaI/EsaR QS system, is required for proper bacterial adhesion and develop...

  10. Transcriptome-Based Analysis of the Pantoea stewartii Quorum-Sensing Regulon and Identification of EsaR Direct Targets

    Ramachandran, Revathy; Burke, Alison Kernell; Cormier, Guy; Jensen, Roderick V.; Stevens, Ann M.

    2014-01-01

    Pantoea stewartii subsp. stewartii is a proteobacterium that causes Stewart's wilt disease in corn plants. The bacteria form a biofilm in the xylem of infected plants and produce capsule that blocks water transport, eventually causing wilt. At low cell densities, the quorum-sensing (QS) regulatory protein EsaR is known to directly repress expression of esaR itself as well as the genes for the capsular synthesis operon transcription regulator, rcsA, and a 2,5-diketogluconate reductase, dkgA...

  11. Impact of Pseudomonas aeruginosa quorum sensing on biofilm persistence in an in vivo intraperitoneal foreign-body infection model

    Christensen, Louise D; Moser, Claus; Jensen, Peter Ø; Rasmussen, Thomas B; Christophersen, Lars; Kjelleberg, Staffan; Kumar, Naresh; Høiby, Niels; Givskov, Michael Christian; Bjarnsholt, Thomas

    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...

  12. The Pseudomonas Quorum-Sensing Regulator RsaL Belongs to the Tetrahelical Superclass of H-T-H Proteins▿

    Rampioni, Giordano; Polticelli, Fabio; Bertani, Iris; Righetti, Karima; Venturi, Vittorio; Zennaro, Elisabetta; Leoni, Livia

    2006-01-01

    In the opportunistic human pathogen Pseudomonas aeruginosa, quorum sensing (QS) is crucial for virulence. The RsaL protein directly represses the transcription of lasI, the synthase gene of the main QS signal molecule. On the basis of sequence homology, RsaL cannot be predicted to belong to any class of characterized DNA-binding proteins. In this study, an in silico model of the RsaL structure was inferred showing that RsaL belongs to the tetrahelical superclass of helix-turn-helix proteins. ...

  13. The Quorum-Sensing Hybrid Histidine Kinase LuxN of Vibrio harveyi Contains a Periplasmically Located N Terminus▿

    Jung, Kirsten; Odenbach, Tina; Timmen, Melanie

    2007-01-01

    Hydropathy profile analyses of the amino acid sequence of the quorum-sensing hybrid histidine kinase LuxN of Vibrio harveyi predict a periplasmic location of the N terminus. To test this, two-hybrid proteins consisting of LuxN and an N-terminally fused maltose-binding protein with or without a leader sequence were analyzed with regard to the enzymatic activities of LuxN, protease accessibility, and complementation of an Escherichia coli malE mutant. The results strongly support a periplasmic location of the N terminus, implying that LuxN is anchored with nine transmembrane domains in the cytoplasmic membrane. PMID:17259316

  14. Quorum Sensing in Bacillus thuringiensis Is Required for Completion of a Full Infectious Cycle in the Insect

    Leyla Slamti; Stéphane Perchat; Eugénie Huillet; Didier Lereclus

    2014-01-01

    Bacterial cell-cell communication or quorum sensing (QS) is a biological process commonly described as allowing bacteria belonging to a same pherotype to coordinate gene expression to cell density. In Gram-positive bacteria, cell-cell communication mainly relies on cytoplasmic sensors regulated by secreted and re-imported signaling peptides. The Bacillus quorum sensors Rap, NprR, and PlcR were previously identified as the first members of a new protein family called RNPP. Except for the Rap p...

  15. Halogenated furanones inhibit quorum sensing through accelerated LuxR turnover

    Manefield, M.; Rasmussen, Thomas Bovbjerg; Henzter, M.; Andersen, Jens Bo; Steinberg, P.; Kjelleberg, S.; Givskov, Michael Christian

    2002-01-01

    N-acyl-L-homoserine lactones (AHLs) are co-regulatory ligands required for control of the expression of genes encoding virulence traits in many Gram-negative bacterial species. Recent studies have indicated that AHLs modulate the cellular concentrations of LuxR-type regulatory proteins by binding...

  16. Genome Sequence of the Pectobacterium atrosepticum Strain CFBP6276, Causing Blackleg and Soft Rot Diseases on Potato Plants and Tubers

    Kwasiborski, Anthony; Mondy, Samuel; Beury-Cirou, Amélie; Faure, Denis

    2013-01-01

    Pectobacterium atrosepticum strain CFBP6276 is a pectinolytic enterobacterium causing blackleg and soft rot of the stem and tuber of Solanum tuberosum. Its virulence is under the control of quorum sensing, with N-acylhomoserine lactones as communication signals. Here, we report the genome sequence of P. atrosepticum strain CFBP6276.

  17. Draft Genome Sequence of the Moderately Halophilic Gammaproteobacterium Halomonas anticariensis FP35T

    Tahrioui, Ali; Quesada, Emilia; Llamas, Inmaculada

    2013-01-01

    Halomonas anticariensis strain FP35T is a moderately halophilic bacterium isolated from a soil sample taken from Fuente de Piedra, a saline wetland in the province of Málaga (Spain), which produces an exopolysaccharide and quorum-sensing signaling molecules of the type N-acylhomoserine lactone. We report here the draft genome sequence of this gammaproteobacterium.

  18. 粘质沙雷氏菌AS-1中SpnR功能及卤化呋喃对其群体感应的抑制%The function of SpnR and the inhibitory effects by halogenated furanone on quorum sensing in Serratia marcescens AS-1

    陶寅璐; 诸星知宏; 加藤纪弘; 池田宰; 庄惠生

    2008-01-01

    By secretion and detection of a series of signaling molecules,bacteria are able to Coordinate gene expression as a community,to regulate a variety of important phenotypes,from virulence factor production to biofilm formation to symbiosis related behaviours such as bioluminescence.This widespread signaling mechanism is called quorum sensing.There are several quorum sensing systems described in Serratia.Serratia marcescens AS-1,isolated from soil,had the LuxI/LuxR homologues called SpnI/SpnR.S. marcescens AS-1 produced two kinds of N-acyl-L-homoserine lactones,N-hexanoyl-L-homoserine lactone and N-(3-oxohexanoyl)-L-homoserine lactone as signal molecules,which involved in quorum sensing to control the gene expression in response to increased cell density.By gene replacement method,the spnR mutant was constructed,named S.marcescens AS-1R.SpnR acted as a negative regulator for the production of prodigiosin,swarming motility and biofilm formation,which were regulated by quorum sensing.Halogenated furanone,known as a natural inhibitor of quorum sensing,could effectively inhibit the quorum sensing of S.marcescens AS-1 but without interrupting AHL-SpnR interaction.All results will be helpful to understand the mechanisms of halogenated furanone inhibition on quorum sensing and the potential application of halogenated furanone in effectively preventing infection disease caused by Serratia strains.%通过分泌和感知一系列信号分子,细菌能够根据自身菌体密度的变化调控基因的表达,从而控制一系列重要的表现型,包括毒力因子的产生,生物膜的形成以及菌体发光等.这种广泛存在的信号机制被称为群体感应.在沙雷氏菌种中已经发现了多套群体感应机制.粘质沙雷氏菌AS-1从土壤中分离,其中含有LuxI/LuxR的同类蛋白,被称为SpnI/SpnR.粘质沙雷氏菌AS-1合成AHLs分子N-hexanoy1-L-homoserinelactone(C6-HSL)和N-(3.oxohexanoyl)-L-homoserine lactone(3-oxo-C6-HSL)作为其信号分子,通

  19. Agaricus Blazei Hot Water Extract Shows Anti Quorum Sensing Activity in the Nosocomial Human Pathogen Pseudomonas Aeruginosa

    Marina Soković

    2014-04-01

    Full Text Available 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, biofilm formation and survival of many pathogenic bacteria, including the Gram negative Pseudomonas aeruginosa, and is considered as a novel and promising target for anti-infectious agents. In this study, the effect of the sub-MICs of Agaricus blazei water extract on QS regulated virulence factors and biofilm formation was evaluated against P. aeruginosa PAO1. Sub-MIC concentrations of the extract which did not kill P. aeruginosa nor inhibited its growth, demonstrated a statistically significant reduction of virulence factors of P. aeruginosa, such as pyocyanin production, twitching and swimming motility. The biofilm forming capability of P. aeruginosa was also reduced in a concentration-dependent manner at sub-MIC values. Water extract of A. blazei is a promising source of antiquorum sensing and antibacterial compounds.

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

    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. Systematic Design of a Quorum Sensing-Based Biosensor for Enhanced Detection of Metal Ion in Escherichia Coli.

    Hsu, Chih-Yuan; Chen, Bing-Kun; Hu, Rei-Hsing; Chen, Bor-Sen

    2016-06-01

    With the recent industrial expansion, heavy metals and other pollutants have increasingly contaminated our living surroundings. The non-degradability of heavy metals may lead to accumulation in food chains and the resulting toxicity could cause damage in organisms. Hence, detection techniques have gradually received attention. In this study, a quorum sensing (QS)-based amplifier is introduced to improve the detection performance of metal ion biosensing. The design utilizes diffusible signal molecules, which freely pass through the cell membrane into the environment to communicate with others. Bacteria cooperate via the cell-cell communication process, thereby displaying synchronous behavior, even if only a minority of the cells detect the metal ion. In order to facilitate the design, the ability of the engineered biosensor to detect metal ion is described in a steady state model. The design can be constructed according to user-oriented specifications by selecting adequate components from corresponding libraries, with the help of a genetic algorithm (GA)-based design method. The experimental results validate enhanced efficiency and detection performance of the quorum sensing-based biosensor of metal ions. PMID:26800545

  2. Sequence and Function of LuxU: a Two-Component Phosphorelay Protein That Regulates Quorum Sensing in Vibrio harveyi

    Freeman, Jeremy A.; Bassler, Bonnie L.

    1999-01-01

    Vibrio harveyi regulates the expression of bioluminescence (lux) in response to cell density, a phenomenon known as quorum sensing. In V. harveyi, two independent quorum-sensing systems exist, and each produces, detects, and responds to a specific cell density-dependent autoinducer signal. The autoinducers are recognized by two-component hybrid sensor kinases called LuxN and LuxQ, and sensory information from both systems is transduced by a phosphorelay mechanism to the response regulator protein LuxO. Genetic evidence suggests that LuxO-phosphate negatively regulates the expression of luminescence at low cell density in the absence of autoinducers. At high cell density, interaction of the sensors with their cognate autoinducers results in dephosphorylation and inactivation of the LuxO repressor. In the present report, we show that LuxN and LuxQ channel sensory information to LuxO via a newly identified phosphorelay protein that we have named LuxU. LuxU shows sequence similarity to other described phosphorelay proteins, including BvgS, ArcB, and Ypd1. A critical His residue (His 58) of LuxU is required for phosphorelay function. PMID:9922254

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

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

    2014-01-01

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

  4. Quorum-Sensing Synchronization of Synthetic Toggle Switches: A Design Based on Monotone Dynamical Systems Theory.

    Nikolaev, Evgeni V; Sontag, Eduardo D

    2016-04-01

    Synthetic constructs in biotechnology, biocomputing, and modern gene therapy interventions are often based on plasmids or transfected circuits which implement some form of "on-off" switch. For example, the expression of a protein used for therapeutic purposes might be triggered by the recognition of a specific combination of inducers (e.g., antigens), and memory of this event should be maintained across a cell population until a specific stimulus commands a coordinated shut-off. The robustness of such a design is hampered by molecular ("intrinsic") or environmental ("extrinsic") noise, which may lead to spontaneous changes of state in a subset of the population and is reflected in the bimodality of protein expression, as measured for example using flow cytometry. In this context, a "majority-vote" correction circuit, which brings deviant cells back into the required state, is highly desirable, and quorum-sensing has been suggested as a way for cells to broadcast their states to the population as a whole so as to facilitate consensus. In this paper, we propose what we believe is the first such a design that has mathematically guaranteed properties of stability and auto-correction under certain conditions. Our approach is guided by concepts and theory from the field of "monotone" dynamical systems developed by M. Hirsch, H. Smith, and others. We benchmark our design by comparing it to an existing design which has been the subject of experimental and theoretical studies, illustrating its superiority in stability and self-correction of synchronization errors. Our stability analysis, based on dynamical systems theory, guarantees global convergence to steady states, ruling out unpredictable ("chaotic") behaviors and even sustained oscillations in the limit of convergence. These results are valid no matter what are the values of parameters, and are based only on the wiring diagram. The theory is complemented by extensive computational bifurcation analysis, performed for a

  5. Quorum-Sensing Synchronization of Synthetic Toggle Switches: A Design Based on Monotone Dynamical Systems Theory

    Nikolaev, Evgeni V.

    2016-01-01

    Synthetic constructs in biotechnology, biocomputing, and modern gene therapy interventions are often based on plasmids or transfected circuits which implement some form of “on-off” switch. For example, the expression of a protein used for therapeutic purposes might be triggered by the recognition of a specific combination of inducers (e.g., antigens), and memory of this event should be maintained across a cell population until a specific stimulus commands a coordinated shut-off. The robustness of such a design is hampered by molecular (“intrinsic”) or environmental (“extrinsic”) noise, which may lead to spontaneous changes of state in a subset of the population and is reflected in the bimodality of protein expression, as measured for example using flow cytometry. In this context, a “majority-vote” correction circuit, which brings deviant cells back into the required state, is highly desirable, and quorum-sensing has been suggested as a way for cells to broadcast their states to the population as a whole so as to facilitate consensus. In this paper, we propose what we believe is the first such a design that has mathematically guaranteed properties of stability and auto-correction under certain conditions. Our approach is guided by concepts and theory from the field of “monotone” dynamical systems developed by M. Hirsch, H. Smith, and others. We benchmark our design by comparing it to an existing design which has been the subject of experimental and theoretical studies, illustrating its superiority in stability and self-correction of synchronization errors. Our stability analysis, based on dynamical systems theory, guarantees global convergence to steady states, ruling out unpredictable (“chaotic”) behaviors and even sustained oscillations in the limit of convergence. These results are valid no matter what are the values of parameters, and are based only on the wiring diagram. The theory is complemented by extensive computational bifurcation

  6. Coral-associated bacteria, quorum sensing disrupters, and the regulation of biofouling.

    Golberg, Karina; Pavlov, Valentina; Marks, Robert S; Kushmaro, Ariel

    2013-01-01

    Marine biofouling, the settlement of microorganisms and macroorganisms on structures submerged in seawater, although economically detrimental, is a successful strategy for survival in hostile environments, where coordinated bacterial communities establish biofilms via the regulation of quorum sensing (QS) communication systems. The inhibition of QS activity among bacteria isolated from different coral species was investigated to gain further insight into its potency in the attenuation, or even the prevention, of undesirable biofouling on marine organisms. It is hypothesized that coral mucus/microorganism interactions are competitive, suggesting that the dominant communities secrete QS disruptive compounds. One hundred and twenty bacterial isolates were collected from healthy coral species and screened for their ability to inhibit QS using three bioreporter strains. Approximately 12, 11, and 24% of the isolates exhibited anti-QS activity against Escherichia coli pSB1075, Chromobacterium violaceum CV026, and Agrobacterium tumefaciens KYC55 indicator strains, respectively. Isolates with positive activity against the bioluminescent monitor strains were scanned via a cytotoxic/genotoxic, E. coli TV1061 and DPD2794 antimicrobial panel. Isolates detected by C. violaceum CV026 and A. tumefaciens KYC55 reporter strains were tested for their ability to inhibit the growth of these reporter strains, which were found to be unaffected. Tests of the Favia sp. coral isolate Fav 2-50-7 (>98% similarity to Vibrio harveyi) for its ability to attenuate the formation of biofilm showed extensive inhibitory activity against biofilms of Pseudomonas aeruginosa and Acinetobacter baumannii. To ascertain the stability and general structure of the active compound, cell-free culture supernatants exposed to an increasing temperature gradient or to digestion by proteinase K, were shown to maintain potent QS attenuation and the ability to inhibit the growth of biofilms. Mass spectrometry confirmed

  7. Quorum-Sensing Synchronization of Synthetic Toggle Switches: A Design Based on Monotone Dynamical Systems Theory.

    Evgeni V Nikolaev

    2016-04-01

    Full Text Available Synthetic constructs in biotechnology, biocomputing, and modern gene therapy interventions are often based on plasmids or transfected circuits which implement some form of "on-off" switch. For example, the expression of a protein used for therapeutic purposes might be triggered by the recognition of a specific combination of inducers (e.g., antigens, and memory of this event should be maintained across a cell population until a specific stimulus commands a coordinated shut-off. The robustness of such a design is hampered by molecular ("intrinsic" or environmental ("extrinsic" noise, which may lead to spontaneous changes of state in a subset of the population and is reflected in the bimodality of protein expression, as measured for example using flow cytometry. In this context, a "majority-vote" correction circuit, which brings deviant cells back into the required state, is highly desirable, and quorum-sensing has been suggested as a way for cells to broadcast their states to the population as a whole so as to facilitate consensus. In this paper, we propose what we believe is the first such a design that has mathematically guaranteed properties of stability and auto-correction under certain conditions. Our approach is guided by concepts and theory from the field of "monotone" dynamical systems developed by M. Hirsch, H. Smith, and others. We benchmark our design by comparing it to an existing design which has been the subject of experimental and theoretical studies, illustrating its superiority in stability and self-correction of synchronization errors. Our stability analysis, based on dynamical systems theory, guarantees global convergence to steady states, ruling out unpredictable ("chaotic" behaviors and even sustained oscillations in the limit of convergence. These results are valid no matter what are the values of parameters, and are based only on the wiring diagram. The theory is complemented by extensive computational bifurcation analysis

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

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

    2014-01-01

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

  9. Dissection of quorum-sensing genes in Burkholderia glumae reveals non-canonical regulation and the new regulatory gene tofM for toxoflavin production.

    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.

  10. Isolation and characterization of N-acylhomoserine lactonase from the thermophilic bacterium, Geobacillus caldoxylosilyticus YS-8.

    Seo, Myung-Ji; Lee, Beom-Seon; Pyun, Yu-Ryang; Park, Hoon

    2011-01-01

    Geobacillus caldoxylosilyticus YS-8, which was isolated from volcanic soil in Indonesia, was found to degrade various N-acylhomoserine lactones (AHLs) with different lengths and acyl side-chain substitutions over a wide temperature range of 30-70 °C. The purified AHL-degrading enzyme showed a single band of 32 kDa, and its N-terminal amino acid sequence was determined to be ANVIKARPKLYVMDN, tentatively suggesting that the AHL-degrading enzyme was AHL lactonase. The AHL-degrading activity of the purified enzyme was maximized at pH 7.5 and 50 °C, and it retained about 50% of its activity even after a heat treatment at 60 °C for 3 h, exhibiting properties consistent with a thermostable enzyme. The mass spectrometric analysis demonstrated that the AHL-degrading enzyme catalyzed lactone ring opening of N-3-oxohexanoyl-L-homoserine lactone and N-hexanoyl-L-homoserine lactone by hydrolyzing the lactones and working as an AHL lactonase. PMID:21897031

  11. Synergistic antibacterial efficacy of early combination treatment with tobramycin and quorum-sensing inhibitors against Pseudomonas aeruginosa in an intraperitoneal foreign-body infection mouse model

    Christensen, Louise; van Gennip, Maria; Jakobsen, Tim H;

    2012-01-01

    Quorum sensing (QS)-deficient Pseudomonas aeruginosa biofilms formed in vitro are more susceptible to tobramycin than QS-proficient P. aeruginosa biofilms, and combination treatment with a QS inhibitor (QSI) and tobramycin shows synergistic effects on the killing of in vitro biofilms. We extended...

  12. The rcsA promoter of Pantoea stewartii subsp. stewartii features a low-level constitutive promoter and an EsaR quorum-sensing-regulated promoter.

    Carlier, Aurelien L; von Bodman, S B

    2006-06-01

    The upstream region of the Pantoea stewartii rcsA gene features two promoters, one for constitutive basal-level expression and a second autoregulated promoter for induced expression. The EsaR quorum-sensing repressor binds to a site centered between the two promoters, blocking transcription elongation from the regulated promoter under noninducing conditions. PMID:16740966

  13. The rcsA Promoter of Pantoea stewartii subsp. stewartii Features a Low-Level Constitutive Promoter and an EsaR Quorum-Sensing-Regulated Promoter

    Carlier, Aurelien L; von Bodman, S B

    2006-01-01

    The upstream region of the Pantoea stewartii rcsA gene features two promoters, one for constitutive basal-level expression and a second autoregulated promoter for induced expression. The EsaR quorum-sensing repressor binds to a site centered between the two promoters, blocking transcription elongation from the regulated promoter under noninducing conditions.

  14. Two homologous Agr-like quorum-sensing systems cooperatively control adherence, cell morphology, and cell viability properties in Lactobacillus plantarum WCFS1

    Fujii, T.; Ingham, C.J.; Nakayama, J.; Beerthuyzen, M.M.; Kunuki, R.; Molenaar, D.; Sturme, M.H.J.; Vaughan, E.E.; Kleerebezem, M.; Vos, de W.M.

    2008-01-01

    A two-component regulatory system of Lactobacillus plantarum, encoded by genes designated lamK and lamR (hpk10 and rrp10), was studied. The lamK and lamR genes encode proteins which are highly homologous to the quorum-sensing histidine kinase LamC and the response regulator LamA, respectively. Trans

  15. The Vibrio harveyi bioassay used routinely to detect AI-2 quorum sensing inhibition is confounded by inconsistent normalization across marine matrices.

    Blair, Walter M; Doucette, Gregory J

    2013-03-01

    The Vibrio harveyi autoinducer-2 (AI-2) bioassay is used routinely to screen for inhibition of the AI-2 quorum sensing system. The present study utilizes three well-described bacterial strains to demonstrate that inconsistent normalization across matrices undermines the assay's use in screening marine samples for AI-2 inhibition. PMID:23305926

  16. Genome Sequence of the Sponge-Associated Ruegeria halocynthiae Strain MOLA R1/13b, a Marine Roseobacter with Two Quorum-Sensing-Based Communication Systems.

    Doberva, Margot; Sanchez-Ferandin, Sophie; Ferandin, Yoan; Intertaglia, Laurent; Croué, Julie; Suzuki, Marcelino; Lebaron, Philippe; Lami, Raphaël

    2014-01-01

    Ruegeria halocynthiae MOLA R1/13b is an alphaproteobacterium isolated from the Mediterranean sea sponge Crambe crambe. We report here the genome sequence and its annotation, revealing the presence of quorum-sensing genes. This is the first report of the full genome of a Ruegeria halocynthiae strain. PMID:25301648

  17. Genome Sequence of the Sponge-Associated Ruegeria halocynthiae Strain MOLA R1/13b, a Marine Roseobacter with Two Quorum-Sensing-Based Communication Systems

    Doberva, Margot; Sanchez-Ferandin, Sophie; Ferandin, Yoan; Intertaglia, Laurent; Croué, Julie; Suzuki, Marcelino; Lebaron, Philippe; Lami, Raphaël

    2014-01-01

    International audience Ruegeria halocynthiae MOLA R1/13b is an alphaproteobacterium isolated from the Mediterranean sea sponge Crambe crambe. We report here the genome sequence and its annotation, revealing the presence of quorum-sensing genes. This is the first report of the full genome of a Ruegeria halocynthiae strain.

  18. IMPACT OF BACTERIAL QUORUM SENSING SYSTEM ON CHANGES OF ORGANOLEPTIC MARKERS OF STORAGE CABBAGE

    Kamila Myszka; Mariola Olkowicz; Elżbieta Radziejewska-Kubzdela; Olejnik-Schmidt, Agnieszka K.; Katarzyna Czaczyk

    2015-01-01

    The regulation of phenotypes of vegetable-associated bacteria can be mediated through the production of acylated homoserine lactones (AHLs). This knowledge is essential for successful control of bacterial diseases of vegetable. The purpose of these investigations was to define the AHL patterns of gram-negative bacteria presented in storage cabbage by LC/MS technique. The phenomenon of regulating the pectinolytic activity and the exopolysaccharide (EPS) production by AHLs that are associated w...

  19. The quorum sensing transcriptional regulator TraR has separate binding sites for DNA and the anti-activator

    Zheng, Zhida; Fuqua, Clay [Department of Molecular and Cellular Biochemistry, 212 S. Hawthorne Dr. Simon Hall 400A, Indiana University, Bloomington, IN 47405 (United States); Chen, Lingling, E-mail: linchen@indiana.edu [Department of Molecular and Cellular Biochemistry, 212 S. Hawthorne Dr. Simon Hall 400A, Indiana University, Bloomington, IN 47405 (United States)

    2012-02-10

    Highlights: Black-Right-Pointing-Pointer Quorum sensing transcription factor TraR is inhibited by forming TraR-TraM complex. Black-Right-Pointing-Pointer K213 is a key DNA binding residue, but not involved in interaction with TraM. Black-Right-Pointing-Pointer Mutations of TraM-interacting TraR residues did not affect DNA-binding of TraR. Black-Right-Pointing-Pointer Mutations of TraR residues reduced the TraR-TraM interaction more than those of TraM. Black-Right-Pointing-Pointer TraM inhibition on DNA-binding of TraR is driven by thermodynamics. -- Abstract: Quorum sensing represents a mechanism by which bacteria control their genetic behaviors via diffusible signals that reflect their population density. TraR, a quorum sensing transcriptional activator in the Rhizobiaceae family, is regulated negatively by the anti-activator TraM via formation of a TraR-TraM heterocomplex. Prior structural analysis suggests that TraM and DNA bind to TraR in distinct sites. Here we combined isothermal titration calorimetry (ITC) and electrophoretic mobility shift assays (EMSA) to investigate roles of TraR residues from Rhizobium sp. NGR234 in binding of both TraM and DNA. We found that K213A mutation of TraR{sub NGR} abolished DNA binding, however, did not alter TraM binding. Mutations of TraM-interfacing TraR{sub NGR} residues decreased the TraR-TraM interaction, but did not affect the DNA-binding activity of TraR{sub NGR}. Thus, our biochemical studies support the independent binding sites on TraR for TraM and DNA. We also found that point mutations in TraR{sub NGR} appeared to decrease the TraR-TraM interaction more effectively than those in TraM{sub NGR}, consistent with structural observations that individual TraR{sub NGR} residues contact with more TraM{sub NGR} residues than each TraM{sub NGR} residues with TraR{sub NGR} residues. Finally, we showed that TraM inhibition on DNA-binding of TraR was driven thermodynamically. We discussed subtle mechanistic differences in Tra

  20. Tropodithietic Acid Production in Phaeobacter gallaeciensis Is Regulated by N-Acyl Homoserine Lactone-Mediated Quorum Sensing▿

    Berger, Martine; Neumann, Alexander; Schulz, Stefan; Simon, Meinhard; Brinkhoff, Thorsten

    2011-01-01

    The production of N-acyl homoserine lactones (AHLs) is widely distributed within the marine Roseobacter clade, and it was proposed that AHL-mediated quorum sensing (QS) is one of the most common cell-to-cell communication mechanisms in roseobacters. The traits regulated by AHL-mediated QS are yet not known for members of the Roseobacter clade, but production of the antibiotic tropodithietic acid (TDA) was supposed to be controlled by AHL-mediated QS in Phaeobacter spp. We describe here for th...

  1. Ndk, a novel host-responsive regulator, negatively regulates bacterial virulence through quorum sensing in Pseudomonas aeruginosa

    Yu, Hua; Xiong, Junzhi; Zhang, Rong; Hu, Xiaomei; Qiu, Jing; Zhang, Di; Xu, Xiaohui; Xin, Rong; He, Xiaomei; Xie, Wei; Sheng, Halei; Chen, Qian; Zhang, Le; Rao, Xiancai; Zhang, Kebin

    2016-01-01

    Pathogenic bacteria could adjust gene expression to enable their survival in the distinct host environment. However, the mechanism by which bacteria adapt to the host environment is not well described. In this study, we demonstrated that nucleoside diphosphate kinase (Ndk) of Pseudomonas aeruginosa is critical for adjusting the bacterial virulence determinants during infection. Ndk expression was down-regulated in the pulmonary alveoli of a mouse model of acute pneumonia. Knockout of ndk up-regulated transcription factor ExsA-mediated T3S regulon expression and decreased exoproduct-related gene expression through the inhibition of the quorum sensing hierarchy. Moreover, in vitro and in vivo studies demonstrated that the ndk mutant exhibits enhanced cytotoxicity and host pathogenicity by increasing T3SS proteins. Taken together, our data reveal that ndk is a critical novel host-responsive gene required for coordinating P. aeruginosa virulence upon acute infection. PMID:27345215

  2. Garlic as an inhibitor of Pseudomonas aeruginosa quorum sensing in cystic fibrosis--a pilot randomized controlled trial

    Smyth, Alan R; Cifelli, Paramita M; Ortori, Catharine A;

    2010-01-01

    Pseudomonas aeruginosa forms biofilms in the cystic fibrosis lung. Quorum sensing (QS) controls biofilm maturation, immune evasion, antibiotic tolerance and virulence factor production. Garlic shows QS inhibitory activity in vitro and in animal models. We report the first clinical trial in man of a...... QS inhibitor.We randomized 34 patients to garlic or olive oil capsules (both 656 mg daily). Clinical outcomes and safety bloods were measured at baseline and after 8 weeks treatment. In this exploratory study, analysis was per protocol.Eight patients withdrew, leaving 26 for analysis (13 garlic...... the garlic group, seven patients had IV antibiotics versus five placebo. There was a highly significant correlation between plasma and sputum measurements of the QS molecule 3-oxo-C12-HSL (Pearson correlation coefficient = 0.914, P = 0.004). At the end of treatment five patients in each group had...

  3. Impact of Pseudomonas aeruginosa quorum sensing on biofilm persistence in an in vivo intraperitoneal foreign-body infection model

    Christensen, Louise Dahl; Moser, Claus; Jensen, Peter Ø;

    2007-01-01

    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......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...... the placebo-treated group. These results were obtained with both an inbred (BALB/c) and an outbred (NMRI) mouse strain. The present results support a model by which functional QS systems play a pivotal role in the ability of bacteria to resist clearing by the innate immune system and strongly suggest...

  4. Ndk, a novel host-responsive regulator, negatively regulates bacterial virulence through quorum sensing in Pseudomonas aeruginosa.

    Yu, Hua; Xiong, Junzhi; Zhang, Rong; Hu, Xiaomei; Qiu, Jing; Zhang, Di; Xu, Xiaohui; Xin, Rong; He, Xiaomei; Xie, Wei; Sheng, Halei; Chen, Qian; Zhang, Le; Rao, Xiancai; Zhang, Kebin

    2016-01-01

    Pathogenic bacteria could adjust gene expression to enable their survival in the distinct host environment. However, the mechanism by which bacteria adapt to the host environment is not well described. In this study, we demonstrated that nucleoside diphosphate kinase (Ndk) of Pseudomonas aeruginosa is critical for adjusting the bacterial virulence determinants during infection. Ndk expression was down-regulated in the pulmonary alveoli of a mouse model of acute pneumonia. Knockout of ndk up-regulated transcription factor ExsA-mediated T3S regulon expression and decreased exoproduct-related gene expression through the inhibition of the quorum sensing hierarchy. Moreover, in vitro and in vivo studies demonstrated that the ndk mutant exhibits enhanced cytotoxicity and host pathogenicity by increasing T3SS proteins. Taken together, our data reveal that ndk is a critical novel host-responsive gene required for coordinating P. aeruginosa virulence upon acute infection. PMID:27345215

  5. Quorum sensing in Aeromonas salmonicida subsp. achromogenes and the effect of the autoinducer synthase AsaI on bacterial virulence

    Schwenteit, Johanna; Gram, Lone; Nielsen, Kristian Fog;

    2011-01-01

    Ideficient mutant was 20-fold higher than that of the isogenic wt strain and the mean day to death of the mutant was significantly prolonged. Furthermore, the expression of two virulence factors (a toxic protease, AsaP1, and a cytotoxic factor) and a brown pigment were reduced in the mutant. AsaP1 productionwas...... an important virulence factor, AsaP1, without affecting bacterial growth, makes A. salmonicida subsp. achromogenes an interesting target organism to study the effects of QS in disease development and QSI in disease control.......The Gram-negative fish pathogenic bacterium Aeromonas salmonicida possesses the LuxIRtype quorum sensing (QS) system, termed AsaIR. In this study the role of QS in A. salmonicida subsp. achromogenes virulence and pigment production was investigated. Five wild-type Asa strains induced the N...

  6. Involvement of Acylated Homoserine Lactones (AHLs) of Aeromonas sobria in Spoilage of Refrigerated Turbot (Scophthalmus maximus L.).

    Li, Tingting; Cui, Fangchao; Bai, Fengling; Zhao, Guohua; Li, Jianrong

    2016-01-01

    One quorum sensing strain was isolated from spoiled turbot. The species was determined by 16S rRNA gene analysis and classical tests, named Aeromonas sobria AS7. Quorum-sensing (QS) signals (N-acyl homoserine lactones (AHLs)) were detected by report strains and their structures were further determined by GC-MS. The activity changes of AHLs on strain growth stage as well as the influence of different culture conditions on secretion activity of AHLs were studied by the punch method. The result indicated that strain AS7 could induce report strains to produce typical phenotypic response. N-butanoyl-dl-homoserine lactone (C₄-HSL), N-hexanoyl-dl-homoserine lactone (C₆-HSL), N-octanoyl-dl-homoserine lactone (C₈-HSL), N-decanoyl-dl-homoserine lactone (C10-HSL), N-dodecanoyl-dl-homoserine lactone (C12-HSL) could be detected. The activities of AHLs were density-dependent and the max secretion level was at pH 8, sucrose culture, 1% NaCl and 32 h, respectively. The production of siderophore in strain AS7 was regulated by exogenous C₈-HSL, rather than C₆-HSL. Exogenous C₄-HSL and C₈-HSL accelerated the growth rate and population density of AS7 in turbot samples under refrigerated storage. However, according to the total viable counts and total volatile basic nitrogen (TVB-N) values of the fish samples, exogenous C₆-HSL did not cause spoilage of the turbot fillets. In conclusion, our results suggested that QS was involved in the spoilage of refrigerated turbot. PMID:27420072

  7. Quorum sensing-disrupting brominated furanones protect the gnotobiotic brine shrimp Artemia franciscana from pathogenic Vibrio harveyi, Vibrio campbellii, and Vibrio parahaemolyticus isolates

    Defoirdt, T; Crab, R.; Wood, T. K.; Sorgeloos, P.; Verstraete, W; P. Bossier

    2006-01-01

    Autoinducer 2 (AI-2) quorum sensing was shown before to regulate the virulence of Vibrio harveyi towards the brine shrimp Artemia franciscana. In this study, several different pathogenic V. harveyi, Vibrio campbellii, and Vibrio parahaemolyticus isolates were shown to produce AI-2. Furthermore, disruption of AI-2 quorum sensing by a natural and a synthetic brominated furanone protected gnotobiotic Artemia from the pathogenic isolates in in vivo challenge tests.

  8. Turing Patterning Using Gene Circuits with Gas-Induced Degradation of Quorum Sensing Molecules

    Hasty, Jeff; Tsimring, Lev

    2016-01-01

    The Turing instability was proposed more than six decades ago as a mechanism leading to spatial patterning, but it has yet to be exploited in a synthetic biology setting. Here we characterize the Turing instability in a specific gene circuit that can be implemented in vitro or in populations of clonal cells producing short-range activator N-Acyl homoserine lactone (AHL) and long-range inhibitor hydrogen peroxide (H2O2) gas. Slowing the production rate of the AHL-degrading enzyme, AiiA, generates stable fixed states, limit cycle oscillations and Turing patterns. Further tuning of signaling parameters determines local robustness and controls the range of unstable wavenumbers in the patterning regime. These findings provide a roadmap for optimizing spatial patterns of gene expression based on familiar quorum and gas sensitive E. coli promoters. The circuit design and predictions may be useful for (re)programming spatial dynamics in synthetic and natural gene expression systems. PMID:27148743

  9. Turing Patterning Using Gene Circuits with Gas-Induced Degradation of Quorum Sensing Molecules.

    Borek, Bartłomiej; Hasty, Jeff; Tsimring, Lev

    2016-01-01

    The Turing instability was proposed more than six decades ago as a mechanism leading to spatial patterning, but it has yet to be exploited in a synthetic biology setting. Here we characterize the Turing instability in a specific gene circuit that can be implemented in vitro or in populations of clonal cells producing short-range activator N-Acyl homoserine lactone (AHL) and long-range inhibitor hydrogen peroxide (H2O2) gas. Slowing the production rate of the AHL-degrading enzyme, AiiA, generates stable fixed states, limit cycle oscillations and Turing patterns. Further tuning of signaling parameters determines local robustness and controls the range of unstable wavenumbers in the patterning regime. These findings provide a roadmap for optimizing spatial patterns of gene expression based on familiar quorum and gas sensitive E. coli promoters. The circuit design and predictions may be useful for (re)programming spatial dynamics in synthetic and natural gene expression systems. PMID:27148743

  10. Identification and characterization of a GDSL esterase gene located proximal to the swr quorum-sensing system of Serratia liquefaciens MG1

    Riedel, K.; Talker-Huiber, D.; Givskov, Michael Christian; Schwab, H.; Eberl, L.

    2003-01-01

    Serratia liquefaciens MG1 employs the swr quorum-sensing system to control various functions, including production of extracellular enzymes and swarming motility. Here we report the sequencing of the swr flanking DNA regions. We identified a gene upstream of swrR and transcribed in the same...... direction, designated estA, which encodes an esterase that belongs to family II of lipolytic enzymes. EstA was heterologously expressed in Escherichia coli, and the substrate specificity of the enzyme was determined in crude extracts. With the aid of zymograms visualizing EstA on polyacrylamide gels and by...... the analysis of a transcriptional fusion of the estA promoter to the promoterless lux4B genes, we showed that expression of the esterase is not regulated by the swr quorum-sensing system. An estA mutant was generated and was found to exhibit growth defects on minimal medium containing Tween 20 or...

  11. The quorum sensing luxS gene is induced in Lactobacillus acidophilus NCFM in response to Listeria monocytogenes

    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- and......-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...... 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...

  12. Role of the Agr-Like Quorum-Sensing System in Regulating Toxin Production by Clostridium perfringens Type B Strains CN1793 and CN1795

    Chen, Jianming; McClane, Bruce A.

    2012-01-01

    Clostridium perfringens type B causes enteritis and enterotoxemia in domestic animals. By definition, these bacteria must produce alpha toxin (CPA), beta toxin (CPB) and epsilon toxin (ETX) although most type B strains also produce perfringolysin O (PFO) and beta2 toxin (CPB2). A recently identified Agr-like quorum-sensing (QS) system in C. perfringens controls all toxin production by surveyed type A, C, and D strains, but whether this QS is involved in regulating toxin production by type B s...

  13. From in vitro to in vivo : establishment of a test system for the biological evaluation of novel quorum sensing inhibitors as anti-infectives against Pseudomonas aeruginosa

    Maurer, Christine Katharina

    2015-01-01

    Innovative, efficient anti-infectives are needed because of increasing antibiotic resistance. Thus, strategies have been proposed interfering with bacterial pathogenicity instead of viability such as inhibition of quorum sensing. This intercellular communication system uses signal molecules to coordinate virulence and biofilm formation. Pseudomonas aeruginosa uses unique signal molecules such as 2-heptyl-3-hydroxy-4-(1H)-quinolone (PQS). Therefore, compounds should be developed blocking their...

  14. Sub-MICs of Mentha piperita essential oil and menthol inhibits AHL mediated quorum sensing and biofilm of Gram negative bacteria

    Fohad Mabood Husain; Iqbal eAhmad; Mohammad Shavez Khan; Ejaz eAhmad; Mohammad Shahnawaz Khan; Qudsia eTahseen; Nasser Abdul latif Alshabib

    2015-01-01

    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 investigatio...

  15. Sub-MICs of Mentha piperita essential oil and menthol inhibits AHL mediated quorum sensing and biofilm of Gram-negative bacteria

    Husain, Fohad M.; Ahmad, Iqbal; Khan, Mohammad S.; Ahmad, Ejaz; Tahseen, Qudisa; Khan, Mohd Shahnawaz; Alshabib, Nasser A.

    2015-01-01

    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 ...

  16. Raw cow’s milk relatively inhibits quorum sensing activity of Cromobacterium violaceum in comparison to raw she-camel’s milk

    Moawad, A.A.; Garbaj, A.M.; S.K. Abolghait

    2011-01-01

    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 comp...

  17. Directed Evolution of a Thermostable Quorum-quenching Lactonase from the Amidohydrolase Superfamily*

    Chow, Jeng Yeong; Xue, Bo; Lee, Kang Hao; Tung, Alvin; Wu, Long; Robinson, Robert C.; Yew, Wen Shan

    2010-01-01

    A thermostable quorum-quenching lactonase from Geobacillus kaustophilus HTA426 (GI: 56420041) was used as an initial template for in vitro directed evolution experiments. This enzyme belongs to the phosphotriesterase-like lactonase (PLL) group of enzymes within the amidohydrolase superfamily that hydrolyze N-acylhomoserine lactones (AHLs) that are involved in virulence pathways of quorum-sensing pathogenic bacteria. Here we have determined the N-butyryl-l-homoserine lactone-liganded structure...

  18. A mathematical model and quantitative comparison of the small RNA circuit in the Vibrio harveyi and Vibrio cholerae quorum sensing systems

    Hunter, G. A. M.; Guevara Vasquez, F.; Keener, J. P.

    2013-08-01

    Quorum sensing is the process by which bacteria regulate their gene expression based on the local cell-population density. The quorum sensing systems of Vibrio harveyi and Vibrio cholerae are comprised of a phosphorelay cascade coupled to a small RNA (sRNA) circuit. The sRNA circuit contains multiple quorum regulated small RNA (Qrr) that regulate expression of the homologous master transcriptional regulators LuxR (in V. harveyi) and HapR (in V. cholerae). Their quorum sensing systems are topologically similar and homologous thereby making it difficult to understand why repression of HapR is more robust than LuxR to changes in Qrr. In this work we formulate and parameterize a novel mathematical model of the V. harveyi and V. cholerae sRNA circuit. We parameterize the model by fitting it to a variety of empirical data from both species. We show that we can distinguish all of the parameters and that the parameterizations (one for each species) are robust to errors in the data. We then use our model to propose some experiments to identify and explain kinetic differences between the species. We find that V. cholerae Qrr are more abundant and more sensitive to changes in LuxO than V. harveyi Qrr and argue that this is why expression of HapR is more robust than LuxR to changes in Qrr.

  19. A mathematical model and quantitative comparison of the small RNA circuit in the Vibrio harveyi and Vibrio cholerae quorum sensing systems

    Quorum sensing is the process by which bacteria regulate their gene expression based on the local cell-population density. The quorum sensing systems of Vibrio harveyi and Vibrio cholerae are comprised of a phosphorelay cascade coupled to a small RNA (sRNA) circuit. The sRNA circuit contains multiple quorum regulated small RNA (Qrr) that regulate expression of the homologous master transcriptional regulators LuxR (in V. harveyi) and HapR (in V. cholerae). Their quorum sensing systems are topologically similar and homologous thereby making it difficult to understand why repression of HapR is more robust than LuxR to changes in Qrr. In this work we formulate and parameterize a novel mathematical model of the V. harveyi and V. cholerae sRNA circuit. We parameterize the model by fitting it to a variety of empirical data from both species. We show that we can distinguish all of the parameters and that the parameterizations (one for each species) are robust to errors in the data. We then use our model to propose some experiments to identify and explain kinetic differences between the species. We find that V. cholerae Qrr are more abundant and more sensitive to changes in LuxO than V. harveyi Qrr and argue that this is why expression of HapR is more robust than LuxR to changes in Qrr. (paper)

  20. N-Acyl Homoserine Lactones in Diverse Pectobacterium and Dickeya Plant Pathogens: Diversity, Abundance, and Involvement in Virulence

    Denis Faure

    2012-03-01

    Full Text Available Soft-rot bacteria Pectobacterium and Dickeya use N-acyl homoserine lactones (NAHSLs as diffusible signals for coordinating quorum sensing communication. The production of NAHSLs was investigated in a set of reference strains and recently-collected isolates, which belong to six species and share the ability to infect the potato host plant. All the pathogens produced different NAHSLs, among which the 3-oxo-hexanoyl- and the 3-oxo-octanoyl-L-homoserine lactones represent at least 90% of total produced NAHSL-amounts. The level of NAHSLs varied from 0.6 to 2 pg/cfu. The involvement of NAHSLs in tuber maceration was investigated by electroporating a quorum quenching vector in each of the bacterial pathogen strains. All the NAHSL-lactonase expressing strains produced a lower amount of NAHSLs as compared to those harboring the empty vector. Moreover, all except Dickeya dadantii 3937 induced a lower level of symptoms in potato tuber assay. Noticeably, aggressiveness appeared to be independent of both nature and amount of produced signals. This work highlights that quorum sensing similarly contributed to virulence in most of the tested Pectobacterium and Dickeya, even the strains had been isolated recently or during the past decades. Thus, these key regulatory-molecules appear as credible targets for developing anti-virulence strategies against these plant pathogens.

  1. Synthesis of N-Acyl Homoserine Lactone Analogues Reveals Strong Activators of SdiA, the Salmonella enterica Serovar Typhimurium LuxR Homologue▿ †

    Janssens, Joost C. A.; Metzger, Kristine; Daniels, Ruth; Ptacek, Dave; Verhoeven, Tine; Habel, Lothar W.; Vanderleyden, Jos; De Vos, Dirk E.; De Keersmaecker, Sigrid C.J.

    2006-01-01

    N-Acyl homoserine lactones (AHLs) are molecules that are synthesized and detected by many gram-negative bacteria to monitor the population density, a phenomenon known as quorum sensing. Salmonella enterica serovar Typhimurium is an exceptional species since it does not synthesize its own AHLs, while it does encode a LuxR homologue, SdiA, which enables this bacterium to detect AHLs that are produced by other species. To obtain more information about the specificity of the ligand binding by Sdi...

  2. The quorum sensing luxS gene is induced in Lactobacillus acidophilus NCFM in response to Listeria monocytogenes.

    Moslehi-Jenabian, Saloomeh; Vogensen, Finn Kvist; Jespersen, Lene

    2011-10-01

    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- 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 during exponential growth in L. acidophilus cells with the highest level in the late-exponential growth phase, decreasing in the stationary phase. Following co-cultivation with L. monocytogenes, the transcriptional level of luxS increased significantly in mid-exponential growing cells of L. acidophilus after incubation with viable L. monocytogenes cells and by addition of cell-free culture supernatant of L. monocytogenes, whereas incubation with heat killed cells of L. monocytogenes had no effect on the transcriptional level. This could indicate that the up-regulation of luxS is due to a response to a secreted compound produced by L. monocytogenes cells. PMID:21784546

  3. Cis-2-dodecenoic acid signal modulates virulence of Pseudomonas aeruginosa through interference with quorum sensing systems and T3SS

    2013-01-01

    Background Cis-2-dodecenoic acid (BDSF) is well known for its important functions in intraspecies signaling in Burkholderia cenocepacia. Previous work has also established an important role of BDSF in interspecies and inter-kingdom communications. It was identified that BDSF modulates virulence of Pseudomonas aeruginosa. However, how BDSF interferes with virulence of P. aeruginosa is still not clear. Results We report here that BDSF mediates the cross-talk between B. cenocepacia and P. aeruginosa through interference with quorum sensing (QS) systems and type III secretion system (T3SS) of P. aeruginosa. Bioassay results revealed that exogenous addition of BDSF not only reduced the transcriptional expression of the regulator encoding gene of QS systems, i.e., lasR, pqsR, and rhlR, but also simultaneously decreased the production of QS signals including 3-oxo-C12-HSL, Pseudomonas quinolone signal (PQS) and C4-HSL, consequently resulting in the down-regulation of biofilm formation and virulence factor production of P. aeruginosa. Furthermore, BDSF and some of its derivatives are also capable of inhibiting T3SS of P. aeruginosa at a micromolar level. Treatment with BDSF obviously reduced the virulence of P. aeruginosa in both HeLa cell and zebrafish infection models. Conclusions These results depict that BDSF modulates virulence of P. aeruginosa through interference with QS systems and T3SS. PMID:24134835

  4. Two-Component Regulatory Systems – implication in the quorum sensing mechanisms and bacteriocin production in lactic acid bacteria

    Lia–Mara Ditu

    2014-08-01

    Full Text Available For lactic acid bacteria, the mechanisms of quorum sensing and response are mediated by peptides or pheromones that interfere with the synthesis of antimicrobial peptides (AMP called bacteriocins, when these molecules reach a certain critical level of concentration. Generally, the synthesis and activity of pheromones is adjusted by means of a two-component regulatory system. The observation that some microorganisms, in particular lactic acid bacteria, produce bacteriocins according to the cell density, has led to the discovery of the involvement of QS mechanisms in the synthesis of these peptides. Bacteriocins synthesis is inducible, the process requiring the extracellular accumulation of peptides that functions as chemical messengers activators of bacteriocins synthesis. This minireview presents the molecular architecture and functions of two-component regulatory systems and ABC transporters implicated in the synthesis and secretion of nisin, one of the most studied bacteriocin. The elucidation of the intimate mechanisms of bacteriocins synthesis is equally of biotechnological and medical importance, opening interesting perspectives for the development of improved technologies for the production of bacteriocins with good yields, and also, for increasing the beneficial anti-infective roles of probiotic bacteria when administered in vivo.

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

    Anton Hartmann

    2013-01-01

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

  6. Fungal dimorphism in the entomopathogenic fungus Metarhizium rileyi: Detection of an in vivo quorum-sensing system.

    Boucias, D; Liu, S; Meagher, R; Baniszewski, J

    2016-05-01

    This investigation documents the expression of the in vivo dimorphic program exhibited by the insect mycopathogen Metarhizium rileyi. This insect mycopathogen represents the key mortality factor regulating various caterpillar populations in legumes, including subtropical and tropical soybeans. Using two hosts and M. rileyi isolates, we have measured M. rileyi growth rates under in vivo and in vitro conditions and have assessed the pathogen's impact on host fitness. Significantly, the hyphal bodies-to-mycelia transition that occurs at the late infection stage is regulated by a quorum-sensing molecule(s) (QSM) that triggers hyphal bodies (Hb) to synchronously switch to the tissue-invasive mycelia. Within hours of this transition, the host insect succumbs to mycosis. The production of the QS chemical(s) occurs when a quorum of Hb is produced in the hemolymph (late-stage infection). Furthermore, the QS activity detected in late-stage infected sera is unique and is unrelated to any known fungal QSM. The lack of similar QS activity from conditioned media of M. rileyi suggests that the chemical signal(s) that mediates the dimorphic switch is produced by host tissues in response to a quorum of hyphal bodies produced in the host hemolymph. The serum-based QS activity is retained after lyophilization, mild heat treatment, and proteinase digestion. However, attempts to extract/identify the QSM have been unsuccessful. Results suggest that the observed hyphal body-to-mycelia transition is a multi-step process involving more than one chemical signal. PMID:27018146

  7. Influence of clove oil on certain quorum-sensing-regulated functions and biofilm of Pseudomonas aeruginosa and Aeromonas hydrophila

    Fohad Mabood Husain; Iqbal Ahmad; Mohammad Asif; Qudsia Tahseen

    2013-12-01

    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 regulated virulence factors and biofilm formation was evaluated against P. aeruginosa PAO1 and Aeromonas hydrophila WAF-38 strain. Sub-inhibitory concentrations of the clove oil demonstrated statistically significant reduction of las- and rhl-regulated virulence factors such as LasB, total protease, chitinase and pyocyanin production, swimming motility and exopolysaccharide production. The biofilm forming capability of PAO1 and A. hydrophila WAF-38 was also reduced in a concentration-dependent manner at all tested sub-MIC values. Further, the PAO1-preinfected Caenorhabditis elegans displayed an enhanced survival when treated with 1.6% v/v of clove oil. The above findings highlight the promising anti-QS-dependent therapeutic function of clove oil against P. aeruginosa.

  8. The DSF type quorum sensing signalling system RpfF/R regulates diverse phenotypes in the opportunistic pathogen Cronobacter.

    Suppiger, Angela; Eshwar, Athmanya Konegadde; Stephan, Roger; Kaever, Volkhard; Eberl, Leo; Lehner, Angelika

    2016-01-01

    Several bacterial pathogens produce diffusible signal factor (DSF)-type quorum sensing (QS) signals to control biofilm formation and virulence. Previous work showed that in Burkholderia cenocepacia the RpfFBc/RpfR system is involved in sensing and responding to DSF signals and that this signal/sensor gene pair is highly conserved in several bacterial species including Cronobacter spp. Here we show that C. turicensis LMG 23827(T) possesses a functional RpfF/R system that is involved in the regulation of various phenotypes, including colony morphology, biofilm formation and swarming motility. In vivo experiments using the zebrafish embryo model revealed a role of this regulatory system in virulence of this opportunistic pathogen. We provide evidence that the RpfF/R system modulates the intracellular c-di-GMP level of the organism, an effect that may underpin the alteration in phenotype and thus the regulated phenotypes may be a consequence thereof. This first report on an RpfF/R-type QS system of an organism outside the genus Burkholderia revealed that both the underlying molecular mechanisms as well as the regulated functions show a high degree of conservation. PMID:26725701

  9. Quorum Sensing in Bacillus thuringiensis Is Required for Completion of a Full Infectious Cycle in the Insect

    Leyla Slamti

    2014-07-01

    Full Text Available Bacterial cell-cell communication or quorum sensing (QS is a biological process commonly described as allowing bacteria belonging to a same pherotype to coordinate gene expression to cell density. In Gram-positive bacteria, cell-cell communication mainly relies on cytoplasmic sensors regulated by secreted and re-imported signaling peptides. The Bacillus quorum sensors Rap, NprR, and PlcR were previously identified as the first members of a new protein family called RNPP. Except for the Rap proteins, these RNPP regulators are transcription factors that directly regulate gene expression. QS regulates important biological functions in bacteria of the Bacillus cereus group. PlcR was first characterized as the main regulator of virulence in B. thuringiensis and B. cereus. More recently, the PlcR-like regulator PlcRa was characterized for its role in cysteine metabolism and in resistance to oxidative stress. The NprR regulator controls the necrotrophic properties allowing the bacteria to survive in the infected host. The Rap proteins negatively affect sporulation via their interaction with a phosphorelay protein involved in the activation of Spo0A, the master regulator of this differentiation pathway. In this review we aim at providing a complete picture of the QS systems that are sequentially activated during the lifecycle of B. cereus and B. thuringiensis in an insect model of infection.

  10. Quorum sensing in Bacillus thuringiensis is required for completion of a full infectious cycle in the insect.

    Slamti, Leyla; Perchat, Stéphane; Huillet, Eugénie; Lereclus, Didier

    2014-08-01

    Bacterial cell-cell communication or quorum sensing (QS) is a biological process commonly described as allowing bacteria belonging to a same pherotype to coordinate gene expression to cell density. In Gram-positive bacteria, cell-cell communication mainly relies on cytoplasmic sensors regulated by secreted and re-imported signaling peptides. The Bacillus quorum sensors Rap, NprR, and PlcR were previously identified as the first members of a new protein family called RNPP. Except for the Rap proteins, these RNPP regulators are transcription factors that directly regulate gene expression. QS regulates important biological functions in bacteria of the Bacillus cereus group. PlcR was first characterized as the main regulator of virulence in B. thuringiensis and B. cereus. More recently, the PlcR-like regulator PlcRa was characterized for its role in cysteine metabolism and in resistance to oxidative stress. The NprR regulator controls the necrotrophic properties allowing the bacteria to survive in the infected host. The Rap proteins negatively affect sporulation via their interaction with a phosphorelay protein involved in the activation of Spo0A, the master regulator of this differentiation pathway. In this review we aim at providing a complete picture of the QS systems that are sequentially activated during the lifecycle of B. cereus and B. thuringiensis in an insect model of infection. PMID:25089349

  11. Regulation of acylated homoserine lactones (AHLs) in beef by spice marination.

    Gopu, Venkadesaperumal; Shetty, Prathapkumar Halady

    2016-06-01

    Quorum sensing (QS) is a signaling mechanism used by bacteria to communicate each other through the release of auto-inducing signaling molecules. Despite the fact that bacteria regulate its phenotypes by QS mechanism, their potential role in meat spoilage is not yet elucidated. In the current study, beef samples were analyzed for its microbial association and for the presence of N-acyl-homoserine-lactone (AHLs) throughout the storage experiments. Isolates were screened for AHLs production and selected spices were screened for their quorum sensing inhibitory (QSI) activity. In addition, effect of spices on AHLs production of Y. enterocolitica was quantified through high performance thin layer chromatography (HP-TLC). Outcome showed that microbial association of beef mainly consists of lactic acid bacteria (LAB) and Enterobacteriaceae. Samples stored at both aerobic and modified atmospheric packaging (MAP) exhibited higher counts whereas; marinated samples stored at MAP exhibited the lowest. It was found that out of 35 isolates Y. enterocolitica induced reporter strain CV026 and its cell-free supernatant contained 26.36 nM/100 ml of AHLs when compared to standard. Among the tested spices, C. cyminum exhibited pronounced results by significantly reducing the AHLs concentration up to 47.75 %. Findings revealed the presence of quorum molecules (AHLs) in beef meat throughout the spoilage process and spices can acts as quorum quenchers to influence the spoilage rate by reducing AHLs production. PMID:27478224

  12. Homoserine Lactones Influence the Reaction of Plants to Rhizobia

    Karl-Heinz Kogel

    2013-08-01

    Full Text Available Bacterial quorum sensing molecules not only grant the communication within bacterial communities, but also influence eukaryotic hosts. N-acyl-homoserine lactones (AHLs produced by pathogenic or beneficial bacteria were shown to induce diverse reactions in animals and plants. In plants, the reaction to AHLs depends on the length of the lipid side chain. Here we investigated the impact of two bacteria on Arabidopsis thaliana, which usually enter a close symbiosis with plants from the Fabaceae (legumes family and produce a long-chain AHL (Sinorhizobium meliloti or a short-chain AHL (Rhizobium etli. We demonstrate that, similarly to the reaction to pure AHL molecules, the impact, which the inoculation with rhizosphere bacteria has on plants, depends on the type of the produced AHL. The inoculation with oxo-C14-HSL-producing S. meliloti strains enhanced plant resistance towards pathogenic bacteria, whereas the inoculation with an AttM lactonase-expressing S. meliloti strain did not. Inoculation with the oxo-C8-HSL-producing R. etli had no impact on the resistance, which is in agreement with our previous hypothesis. In addition, plants seem to influence the availability of AHLs in the rhizosphere. Taken together, this report provides new insights in the role of N-acyl-homoserine lactones in the inter-kingdom communication at the root surface.

  13. Relative contributions of Vibrio polysaccharide and quorum sensing to the resistance of Vibrio cholerae to predation by heterotrophic protists.

    Shuyang Sun

    Full Text Available Protozoan grazing is a major mortality factor faced by bacteria in the environment. Vibrio cholerae, the causative agent of the disease cholera, is a natural inhabitant of aquatic ecosystems, and its survival depends on its ability to respond to stresses, such as predation by heterotrophic protists. Previous results show that grazing pressure induces biofilm formation and enhances a smooth to rugose morphotypic shift, due to increased expression of Vibrio polysaccharide (VPS. In addition to negatively controlling vps genes, the global quorum sensing (QS regulator, HapR, plays a role in grazing resistance as the ΔhapR strain is efficiently consumed while the wild type (WT is not. Here, the relative and combined contributions of VPS and QS to grazing resistance were investigated by exposing VPS and HapR mutants and double mutants in VPS and HapR encoding genes at different phases of biofilm development to amoeboid and flagellate grazers. Data show that the WT biofilms were grazing resistant, the VPS mutants were less resistant than the WT strain, but more resistant than the QS mutant strain, and that QS contributes to grazing resistance mainly in mature biofilms. In addition, grazing effects on biofilms of mixed WT and QS mutant strains were investigated. The competitive fitness of each strain in mixed biofilms was determined by CFU and microscopy. Data show that protozoa selectively grazed the QS mutant in mixed biofilms, resulting in changes in the composition of the mixed community. A small proportion of QS mutant cells which comprised 4% of the mixed biofilm biovolume were embedded in grazing resistant WT microcolonies and shielded from predation, indicating the existence of associational protection in mixed biofilms.

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

    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.

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

    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

  16. Tobramycin at subinhibitory concentration inhibits the RhlI/R quorum sensing system in a Pseudomonas aeruginosa environmental isolate

    Venturi Vittorio

    2010-06-01

    Full Text Available Abstract Background Antibiotics are not only small molecules with therapeutic activity in killing or inhibiting microbial growth, but can also act as signaling molecules affecting gene expression in bacterial communities. A few studies have demonstrated the effect of tobramycin as a signal molecule on gene expression at the transcriptional level and its effect on bacterial physiology and virulence. These have shown that subinhibitory concentrations (SICs of tobramycin induce biofilm formation and enhance the capabilities of P. aeruginosa to colonize specific environments. Methods Environmental P. aeruginosa strain PUPa3 was grown in the presence of different concentrations of tobramycin and it was determined at which highest concentration SIC, growth, total protein levels and translation efficiency were not affected. At SIC it was then established if phenotypes related to cell-cell signaling known as quorum sensing were altered. Results In this study it was determined whether tobramycin sensing/response at SICs was affecting the two independent AHL QS systems in an environmental P. aeruginosa strain. It is reasonable to assume that P. aeruginosa encounters tobramycin in nature since it is produced by niche mate Streptomyces tenebrarius. It was established that SICs of tobramycin inhibited the RhlI/R system by reducing levels of C4-HSL production. This effect was not due to a decrease of rhlI transcription and required tobramycin-ribosome interaction. Conclusions Tobramycin signaling in P. aeruginosa occurs and different strains can have a different response. Understanding the tobramycin response by an environmental P. aeruginosa will highlight possible inter-species signalling taking place in nature and can possible also have important implications in the mode of utilization for human use of this very important antibiotic.

  17. A novel pheromone quorum-sensing system controls the development of natural competence in Streptococcus thermophilus and Streptococcus salivarius.

    Fontaine, Laetitia; Boutry, Céline; de Frahan, Marie Henry; Delplace, Brigitte; Fremaux, Christophe; Horvath, Philippe; Boyaval, Patrick; Hols, Pascal

    2010-03-01

    In streptococcal species, the key step of competence development is the transcriptional induction of comX, which encodes the alternative sigma factor sigma(X), which positively regulates genes necessary for DNA transformation. In Streptococcus species belonging to the mitis and mutans groups, induction of comX relies on the activation of a three-component system consisting of a secreted pheromone, a histidine kinase, and a response regulator. In Streptococcus thermophilus, a species belonging to the salivarius group, the oligopeptide transporter Ami is essential for comX expression under competence-inducing conditions. This suggests a different regulation pathway of competence based on the production and reimportation of a signal peptide. The objective of our work was to identify the main actors involved in the early steps of comX induction in S. thermophilus LMD-9. Using a transcriptomic approach, four highly induced early competence operons were identified. Among them, we found a Rgg-like regulator (Ster_0316) associated with a nonannotated gene encoding a 24-amino-acid hydrophobic peptide (Shp0316). Through genetic deletions, we showed that these two genes are essential for comX induction. Moreover, addition to the medium of synthetic peptides derived from the C-terminal part of Shp0316 restored comX induction and transformation of a Shp0316-deficient strain. These peptides also induced competence in S. thermophilus and Streptococcus salivarius strains that are poorly transformable or not transformable. Altogether, our results show that Ster_0316 and Shp0316, renamed ComRS, are the two members of a novel quorum-sensing system responsible for comX induction in species from the salivarius group, which differs from the classical phosphorelay three-component system identified previously in streptococci. PMID:20023010

  18. A Novel Pheromone Quorum-Sensing System Controls the Development of Natural Competence in Streptococcus thermophilus and Streptococcus salivarius▿ †

    Fontaine, Laetitia; Boutry, Céline; de Frahan, Marie Henry; Delplace, Brigitte; Fremaux, Christophe; Horvath, Philippe; Boyaval, Patrick; Hols, Pascal

    2010-01-01

    In streptococcal species, the key step of competence development is the transcriptional induction of comX, which encodes the alternative sigma factor σX, which positively regulates genes necessary for DNA transformation. In Streptococcus species belonging to the mitis and mutans groups, induction of comX relies on the activation of a three-component system consisting of a secreted pheromone, a histidine kinase, and a response regulator. In Streptococcus thermophilus, a species belonging to the salivarius group, the oligopeptide transporter Ami is essential for comX expression under competence-inducing conditions. This suggests a different regulation pathway of competence based on the production and reimportation of a signal peptide. The objective of our work was to identify the main actors involved in the early steps of comX induction in S. thermophilus LMD-9. Using a transcriptomic approach, four highly induced early competence operons were identified. Among them, we found a Rgg-like regulator (Ster_0316) associated with a nonannotated gene encoding a 24-amino-acid hydrophobic peptide (Shp0316). Through genetic deletions, we showed that these two genes are essential for comX induction. Moreover, addition to the medium of synthetic peptides derived from the C-terminal part of Shp0316 restored comX induction and transformation of a Shp0316-deficient strain. These peptides also induced competence in S. thermophilus and Streptococcus salivarius strains that are poorly transformable or not transformable. Altogether, our results show that Ster_0316 and Shp0316, renamed ComRS, are the two members of a novel quorum-sensing system responsible for comX induction in species from the salivarius group, which differs from the classical phosphorelay three-component system identified previously in streptococci. PMID:20023010

  19. Identification and characterization of naturally occurring DSF-family quorum sensing signal turnover system in the phytopathogen Xanthomonas.

    Zhou, Lian; Wang, Xing-Yu; Sun, Shuang; Yang, Li-Chao; Jiang, Bo-Le; He, Ya-Wen

    2015-11-01

    Molecules of the diffusible signal factor (DSF)-family are a class of quorum sensing (QS) signals used by the phytopathogens Xanthomonas. Studies during the last decade have outlined how Xanthomonas cells enter the QS phase. However, information on the mechanism underlying its exit from the QS phase is limited. RpfB has recently been reported as a fatty acyl-CoA ligase (FCL) that activates a wide range of fatty acids to their CoA esters in vitro. Here, we establish an improved quantification assay for DSF-family signals using liquid chromatography-mass spectrometry in X. campestris pv. campestris (Xcc). We first demonstrated that RpfB represents a naturally occurring DSF-family signal turnover system. RpfB effectively turns over DSF-family signals DSF and BDSF in vivo. RpfB FCL enzymatic activity is required for DSF and BDSF turnover. Deletion of rpfB slightly increased Xcc virulence in the Chinese radish and overexpression of rpfB significantly decreased virulence. We further showed that the expression of rpfB is growth phase-dependent, and its expression is significantly enhanced when Xcc cells enter the stationary phase. DSF regulates rpfB expression in a concentration-dependent manner. rpfB expression is also negatively regulated by the DSF signalling components RpfC, RpfG and Clp. The global transcription factor Clp directly binds to the AATGC-tgctgc-GCATC motif in the promoter region of rpfB to repress its expression. Finally, RpfB-dependent signal turnover system was detected in a wide range of bacterial species, suggesting that it is a conserved mechanism. PMID:26234930

  20. Structural and Molecular Mechanism of CdpR Involved in Quorum-Sensing and Bacterial Virulence in Pseudomonas aeruginosa.

    Jingru Zhao

    2016-04-01

    Full Text Available Although quorum-sensing (QS systems are important regulators of virulence gene expression in the opportunistic human pathogen Pseudomonas aeruginosa, their detailed regulatory mechanisms have not been fully characterized. Here, we show that deletion of PA2588 resulted in increased production of pyocyanin and biofilm, as well as enhanced pathogenicity in a mouse model. To gain insights into the function of PA2588, we performed a ChIP-seq assay and identified 28 targets of PA2588, including the intergenic region between PA2588 and pqsH, which encodes the key synthase of Pseudomonas quinolone signal (PQS. Though the C-terminal domain was similar to DNA-binding regions of other AraC family members, structural studies revealed that PA2588 has a novel fold at the N-terminal region (NTR, and its C-terminal HTH (helix-turn-helix domain is also unique in DNA recognition. We also demonstrated that the adaptor protein ClpS, an essential regulator of ATP-dependent protease ClpAP, directly interacted with PA2588 before delivering CdpR to ClpAP for degradation. We named PA2588 as CdpR (ClpAP-degradation and pathogenicity Regulator. Moreover, deletion of clpP or clpS/clpA promotes bacterial survival in a mouse model of acute pneumonia infection. Taken together, this study uncovered that CdpR is an important QS regulator, which can interact with the ClpAS-P system to regulate the expression of virulence factors and pathogenicity.