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

DEFF Research Database (Denmark)

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

2002-01-01

Novel molecular tools have been constructed which allow for in situ detection of N-acyl homoserine lactone (AHL)-mediated quorum sensing in Pseudomonas aeruginosa biofilms. The reporter responds to AHL activation of LasR lay expression of an unstable version of the green-fluorescent protein (Gfp...

Flagellin and F4 fimbriae have opposite effects on biofilm formation and quorum sensing in F4ac+ enterotoxigenic Escherichia coli.

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Zhou, Mingxu; Guo, Zhiyan; Yang, Yang; Duan, Qiangde; Zhang, Qi; Yao, Fenghua; Zhu, Jun; Zhang, Xinjun; Hardwidge, Philip R; Zhu, Guoqiang

2014-01-10

Bacteria that form biofilms are often highly resistant to antibiotics and are capable of evading the host immune system. To evaluate the role of flagellin and F4 fimbriae on biofilm formation by enterotoxigenic Escherichia coli (ETEC), we deleted the fliC (encoding the major flagellin protein) and/or the faeG (encoding the major subunit of F4 fimbriae) genes from ETEC C83902. Biofilm formation was reduced in the fliC mutant but increased in the faeG mutant, as compared with the wild-type strain. The expression of AI-2 quorum sensing associated genes was regulated in the fliC and faeG mutants, consistent with the biofilm formation of these strains. But, deleting fliC and/or faeG also inhibited AI-2 quorum sensing activity. Copyright © 2013 Elsevier B.V. All rights reserved.

Streptococcus gordonii LuxS/autoinducer-2 quorum-sensing system modulates the dual-species biofilm formation with Streptococcus mutans.

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Wang, Xiao; Li, Xiaolan; Ling, Junqi

2017-07-01

Dental plaques are mixed-species biofilms that are related to the development of dental caries. Streptococcus mutans (S. mutans) is an important cariogenic bacterium that forms mixed-species biofilms with Streptococcus gordonii (S. gordonii), an early colonizer of the tooth surface. The LuxS/autoinducer-2(AI-2) quorum sensing system is involved in the regulation of mixed-species biofilms, and AI-2 is proposed as a universal signal for the interaction between bacterial species. In this work, a S. gordonii luxS deficient strain was constructed to investigate the effect of the S. gordonii luxS gene on dual-species biofilm formed by S. mutans and S. gordonii. In addition, AI-2 was synthesized in vitro by incubating recombinant LuxS and Pfs enzymes of S. gordonii together. The effect of AI-2 on S. mutans single-species biofilm formation and cariogenic virulence gene expression were also assessed. The results showed that luxS disruption in S. gordonii altered dual-species biofilm formation, architecture, and composition, as well as the susceptibility to chlorhexidine. And the in vitro synthesized AI-2 had a concentration-dependent effect on S. mutans biofilm formation and virulence gene expression. These findings indicate that LuxS/AI-2 quorum-sensing system of S. gordonii plays a role in regulating the dual-species biofilm formation with S. mutans. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Influence of Nutrient Availability and Quorum Sensing on the Formation of Metabolically Inactive Microcolonies Within Structurally Heterogeneous Bacterial Biofilms: An Individual-Based 3D Cellular Automata Model.

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Machineni, Lakshmi; Rajapantul, Anil; Nandamuri, Vandana; Pawar, Parag D

2017-03-01

The resistance of bacterial biofilms to antibiotic treatment has been attributed to the emergence of structurally heterogeneous microenvironments containing metabolically inactive cell populations. In this study, we use a three-dimensional individual-based cellular automata model to investigate the influence of nutrient availability and quorum sensing on microbial heterogeneity in growing biofilms. Mature biofilms exhibited at least three structurally distinct strata: a high-volume, homogeneous region sandwiched between two compact sections of high heterogeneity. Cell death occurred preferentially in layers in close proximity to the substratum, resulting in increased heterogeneity in this section of the biofilm; the thickness and heterogeneity of this lowermost layer increased with time, ultimately leading to sloughing. The model predicted the formation of metabolically dormant cellular microniches embedded within faster-growing cell clusters. Biofilms utilizing quorum sensing were more heterogeneous compared to their non-quorum sensing counterparts, and resisted sloughing, featuring a cell-devoid layer of EPS atop the substratum upon which the remainder of the biofilm developed. Overall, our study provides a computational framework to analyze metabolic diversity and heterogeneity of biofilm-associated microorganisms and may pave the way toward gaining further insights into the biophysical mechanisms of antibiotic resistance.

Effect of salinity and incubation time of planktonic cells on biofilm formation, motility, exoprotease production, and quorum sensing of Aeromonas hydrophila.

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Jahid, Iqbal Kabir; Mizan, Md Furkanur Rahaman; Ha, Angela J; Ha, Sang-Do

2015-08-01

The aim of this study was to determine the effect of salinity and age of cultures on quorum sensing, exoprotease production, and biofilm formation by Aeromonas hydrophila on stainless steel (SS) and crab shell as substrates. Biofilm formation was assessed at various salinities, from fresh (0%) to saline water (3.0%). For young and old cultures, planktonic cells were grown at 30 °C for 24 h and 96 h, respectively. Biofilm formation was assessed on SS, glass, and crab shell; viable counts were determined in R2A agar for SS and glass, but Aeromonas-selective media was used for crab shell samples to eliminate bacterial contamination. Exoprotease activity was assessed using a Fluoro™ protease assay kit. Quantification of acyl-homoserine lactone (AHL) was performed using the bioreporter strain Chromobacterium violaceum CV026 and the concentration was confirmed using high-performance liquid chromatography (HPLC). The concentration of autoinducer-2 (AI-2) was determined with Vibrio harveyi BB170. The biofilm structure at various salinities (0-3 %) was assessed using field emission electron microscopy (FESEM). Young cultures of A. hydrophila grown at 0-0.25% salinity showed gradual increasing of biofilm formation on SS, glass and crab shell; swarming and swimming motility; exoproteases production, AHL and AI-2 quorum sensing; while all these phenotypic characters reduced from 0.5 to 3.0% salinity. The FESEM images also showed that from 0 to 0.25% salinity stimulated formation of three-dimensional biofilm structures that also broke through the surface by utilizing the chitin surfaces of crab, while 3% salinity stimulated attachment only for young cultures. However, in marked contrast, salinity (0.1-3%) had no effect on the stimulation of biofilm formation or on phenotypic characters for old cultures. However, all concentrations reduced biofilm formation, motility, protease production and quorum sensing for old culture. Overall, 0-0.25% salinity enhanced biofilm formation

Inhibition of biofilm formation, quorum sensing and infection in Pseudomonas aeruginosa by natural products-inspired organosulfur compounds.

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Nathaniel C Cady

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

Characterization of type 2 quorum sensing in Klebsiella pneumoniae and relationship with biofilm formation

DEFF Research Database (Denmark)

Balestrino, D.; Haagensen, Janus Anders Juul; Rich, C.

2005-01-01

Quorum sensing is a process by which bacteria communicate by using secreted chemical signaling molecules called autoinducers. Many bacterial species modulate the expression of a wide variety of physiological functions in response to changes in population density by this mechanism. In this study, ...... steps of biofilm formation. These data suggest that a LuxS-dependent signal plays a role in the early stages of biofilm formation by K. pneumoniae....... observed in minimal medium supplemented with glycerol. To determine the potential role of luxS in colonization processes, a K. pneumoniae luxS isogenic mutant was constructed and tested for its capacity to form biofilms in vitro on an abiotic surface and to colonize the intestinal tract in a murine model....... No difference was observed in the level of intestinal colonization between the wild-type strain and the luxS mutant. Microscopic analysis of biofilm structures revealed that the luxS mutant was able to form a mature biofilm but with reduced capacities in the development of microcolonies, mostly in the early...

Quorum signaling and sensing by nontypeable Haemophilus influenzae.

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Swords, W Edward

2012-01-01

Quorum signals are diffusible factors produced by bacteria that coordinate communal responses. For nontypeable Haemophilus influenzae (NTHi), a series of recent papers indicate that production and sensing of quorum signals are determinants of biofilm formation/maturation and persistence in vivo. In this mini-review I will summarize the current knowledge about quorum signaling/sensing by this organism, and identify specific topics for additional study.

Quorum signaling and sensing by nontypeable Haemophilus influenzae

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W Edward Swords

2012-07-01

Full Text Available Quorum signals are diffusible factors produced by bacteria that coordinate communal responses. For Haemophilus influenzae, a series of recent papers indicate that production and sensing of quorum signals are determinants of biofilm formation/maturation and persistence in vivo. In this mini-review I will summarize the current knowledge about quorum signaling/sensing by H. influenzae, and identify specific topics for additional study.

Passive control of quorum sensing: prevention of Pseudomonas aeruginosa biofilm formation by imprinted polymers.

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Piletska, Elena V; Stavroulakis, Georgios; Larcombe, Lee D; Whitcombe, Michael J; Sharma, Anant; Primrose, Sandy; Robinson, Gary K; Piletsky, Sergey A

2011-04-11

Here we present the first molecular imprinted polymer (MIP) that is able to attenuate the biofilm formation of the opportunistic human pathogen Pseudomonas aeruginosa through specific sequestration of its signal molecule N-(3-oxododecanoyl)-L-homoserine lactone (3-oxo-C(12)-AHL). The MIP was rationally designed using computational modeling, and its capacity and specificity and that of a corresponding blank polymer toward signal molecule of P. aeruginosa (3-oxo-C(12)-AHL) and its analogue were tested. The biofilm formation in the presence of polymers and without polymers was studied using scanning confocal laser microscopy. Staining with crystal violet dye was used for the quantification of the biofilm formation. A significant reduction of the biofilm growth was observed in the presence of MIP (>80%), which was superior to that of the resin prepared without template, which showed a reduction of 40% in comparison with biofilm, which was grown without polymer addition. It was shown that 3-oxo-C(12)-AHL-specific MIP prevented the development of quorum-sensing-controlled phenotypes (in this case, biofilm formation) from being up-regulated. The developed MIP could be considered as a new tool for the elimination of life-threatening infections in a multitude of practical applications; it could, for example, be grafted on the surface of medical devices such as catheters and lenses, be a component of paints, or be used as a wound adsorbent.

Novel linear polymers able to inhibit bacterial quorum sensing.

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Cavaleiro, Eliana; Duarte, Ana Sofia; Esteves, Ana Cristina; Correia, António; Whitcombe, Michael J; Piletska, Elena V; Piletsky, Sergey A; Chianella, Iva

2015-05-01

Bacterial phenotypes, such as biofilm formation, antibiotic resistance and virulence expression, are associated with quorum sensing. Quorum sensing is a density-dependent regulatory system of gene expression controlled by specific signal molecules, such as N-acyl homoserine lactones (AHLs), produced and released by bacteria. This study reports the development of linear polymers capable to attenuate quorum sensing by adsorption of AHLs. Linear polymers were synthesized using MMA as backbone monomer and methacrylic acid and itaconic acid as functional monomers. Two different quorum sensing-controlled phenotypes, Vibrio fischeri bioluminescence and Aeromonas hydrophila biofilm formation, were evaluated to test the polymers' efficiency. Results showed that both phenotypes were significantly affected by the polymers, with the itaconic acid-containing material being more effective than the methacrylic acid one. The polymer inhibitory effects were reverted by the addition of lactones, confirming attenuation of quorum sensing through sequestration of signal molecules. The polymers also showed no cytotoxicity when tested using a mammalian cell line. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Quorum Sensing of Periodontal Pathogens

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Darije Plančak

2015-01-01

Full Text Available The term ‘quorum sensing’ describes intercellular bacterial communication which regulates bacterial gene expression according to population cell density. Bacteria produce and secrete small molecules, named autoinducers, into the intercellular space. The concentration of these molecules increases as a function of population cell density. Once the concentration of the stimulatory threshold is reached, alteration in gene expression occurs. Gram-positive and Gram-negative bacteria possess different types of quorum sensing systems. Canonical LuxI/R-type/acyl homoserine lactone mediated quorum sensing system is the best studied quorum sensing circuit and is described in Gram-negative bacteria which employ it for inter-species communication mostly. Grampositive bacteria possess a peptide-mediated quorum sensing system. Bacteria can communicate within their own species (intra-species but also between species (inter-species, for which they employ an autoinducer-2 quorum sensing system which is called the universal language of the bacteria. Periodontal pathogenic bacteria possess AI-2 quorum sensing systems. It is known that they use it for regulation of biofilm formation, iron uptake, stress response and virulence factor expression. A better understanding of bacterial communication mechanisms will allow the targeting of quorum sensing with quorum sensing inhibitors to prevent and control disease.

The symbiotic biofilm of Sinorhizobium fredii SMH12, necessary for successful colonization and symbiosis of Glycine max cv Osumi, is regulated by Quorum Sensing systems and inducing flavonoids via NodD1.

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Francisco Pérez-Montaño

Full Text Available Bacterial surface components, especially exopolysaccharides, in combination with bacterial Quorum Sensing signals are crucial for the formation of biofilms in most species studied so far. Biofilm formation allows soil bacteria to colonize their surrounding habitat and survive common environmental stresses such as desiccation and nutrient limitation. This mode of life is often essential for survival in bacteria of the genera Mesorhizobium, Sinorhizobium, Bradyrhizobium, and Rhizobium. The role of biofilm formation in symbiosis has been investigated in detail for Sinorhizobium meliloti and Bradyrhizobium japonicum. However, for S. fredii this process has not been studied. In this work we have demonstrated that biofilm formation is crucial for an optimal root colonization and symbiosis between S. fredii SMH12 and Glycine max cv Osumi. In this bacterium, nod-gene inducing flavonoids and the NodD1 protein are required for the transition of the biofilm structure from monolayer to microcolony. Quorum Sensing systems are also required for the full development of both types of biofilms. In fact, both the nodD1 mutant and the lactonase strain (the lactonase enzyme prevents AHL accumulation are defective in soybean root colonization. The impairment of the lactonase strain in its colonization ability leads to a decrease in the symbiotic parameters. Interestingly, NodD1 together with flavonoids activates certain quorum sensing systems implicit in the development of the symbiotic biofilm. Thus, S. fredii SMH12 by means of a unique key molecule, the flavonoid, efficiently forms biofilm, colonizes the legume roots and activates the synthesis of Nod factors, required for successfully symbiosis.

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

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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

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

DEFF Research Database (Denmark)

Fong, July; Zhang, Chaodong; Yang, Renliang

2018-01-01

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

Auto Poisoning of the Respiratory Chain by a Quorum Sensing Regulated Molecule Favors Biofilm Formation and Antibiotic Tolerance

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Hazan, Ronen; Que, Yok Ai; Maura, Damien; Strobel, Benjamin; Majcherczyk, Paul Anthony; Hopper, Laura Rose; Wilbur, David J.; Hreha, Teri N.; Barquera, Blanca; Rahme, Laurence G.

2015-01-01

Summary Bacterial programmed cell death and quorum sensing are direct examples of prokaryote group behaviors, wherein cells coordinate their actions to function cooperatively like one organism for the benefit of the whole culture. We demonstrate here that 2-n-heptyl-4-hydroxyquinoline-N-oxide (HQNO), a Pseudomonas aeruginosa quorum sensing -regulated low-molecular-weight excreted molecule, and triggers autolysis by self-perturbing the electron transfer reactions of the cytochrome bc1 complex. HQNO induces specific self-poisoning by disrupting the flow of electrons through the respiratory chain at the cytochrome bc1 complex, causing a leak of reducing equivalents to O2 whereby electrons that would normally be passed to cytochrome c are donated directly to O2. The subsequent mass production of reactive oxygen species (ROS) reduces membrane potential and disrupts membrane integrity, causing bacterial cell autolysis and DNA release. DNA subsequently promotes biofilm formation and increases antibiotic tolerance to beta-lactams, suggesting that HQNO-dependent cell autolysis is advantageous to the bacterial populations. These data both identify a new programmed cell death system, and a novel role for HQNO as a critical-inducer of biofilm formation and antibiotic tolerance. This newly identified pathway suggests intriguing mechanistic similarities with the initial mitochondrial-mediated steps of eukaryotic apoptosis. PMID:26776731

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

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Vincent eLeung

2015-10-01

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

Interference in Bacterial Quorum Sensing: A Biopharmaceutical Perspective

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Benjamin Rémy

2018-03-01

Full Text Available Numerous bacteria utilize molecular communication systems referred to as quorum sensing (QS to synchronize the expression of certain genes regulating, among other aspects, the expression of virulence factors and the synthesis of biofilm. To achieve this process, bacteria use signaling molecules, known as autoinducers (AIs, as chemical messengers to share information. Naturally occurring strategies that interfere with bacterial signaling have been extensively studied in recent years, examining their potential to control bacteria. To interfere with QS, bacteria use quorum sensing inhibitors (QSIs to block the action of AIs and quorum quenching (QQ enzymes to degrade signaling molecules. Recent studies have shown that these strategies are promising routes to decrease bacterial pathogenicity and decrease biofilms, potentially enhancing bacterial susceptibility to antimicrobial agents including antibiotics and bacteriophages. The efficacy of QSIs and QQ enzymes has been demonstrated in various animal models and are now considered in the development of new medical devices against bacterial infections, including dressings, and catheters for enlarging the therapeutic arsenal against bacteria.

Size of quorum sensing communities

DEFF Research Database (Denmark)

Ferkinghoff-Borg, Jesper; Sams, Thomas

2014-01-01

Ensembles of bacteria are able to coordinate their phenotypic behavior in accordance with the size, density, and growth state of the ensemble. This is achieved through production and exchange of diffusible signal molecules in a cell–cell regulatory system termed quorum sensing. In the generic....... For a disk-shaped biofilm the geometric factor is the horizontal dimension multiplied by the height, and the square of the height of the biofilm if there is significant flow above the biofilm. A remarkably simple factorized expression for the size is obtained, which separates the all-or-none ignition caused...

In vitro antibiofilm efficacy of Piper betle against quorum sensing mediated biofilm formation of luminescent Vibrio harveyi.

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Srinivasan, Ramanathan; Santhakumari, Sivasubramanian; Ravi, Arumugam Veera

2017-09-01

Vibrio harveyi is a potent biofilm former, which confers resistance to multiple antimicrobials, disinfectants, chemicals and biocides. The prevalence of biofilm mediated antibiotic resistance among aquatic bacterial pathogens stresses the search for novel alternative approach to treat vibriosis in aquaculture. Exploring suitable therapeutics from natural resources could be a novel area of research. Therefore, this work was executed to evaluate the inhibitory effect of Piper betle ethyl acetate extract (PBE) on bioluminescence production and biofilm formation of V. harveyi. Minimal inhibitory concentration (MIC) of PBE against planktonic V. harveyi was found to be 1600 μg ml -1 ; furthermore, PBE inhibited the quorum sensing (QS) mediated bioluminescence production and biofilm formation in V. harveyi upto 98 and 74% respectively, at its sub-MIC concentration of 400 μg ml -1 without affecting their cell viability. Similar results were obtained for exopolysaccharides production and swimming motility related to biofilm formation of V. harveyi, where PBE reduced EPS production upto 64%. Light and confocal laser scanning microscopic analyses further confirmed that the PBE effectively prevented the initial attachment as well as microcolonies formation of V. harveyi biofilm, when compared to their untreated controls. This study demonstrates the promising antibiofilm activity of PBE and confirms the ethnopharmacological potential of this plant against V. harveyi infections. Copyright © 2017 Elsevier Ltd. All rights reserved.

The CpAL quorum sensing system regulates production of hemolysins CPA and PFO to build Clostridium perfringens biofilms.

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Vidal, Jorge E; Shak, Joshua R; Canizalez-Roman, Adrian

2015-06-01

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. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

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

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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

Effect of organic acids on biofilm formation and quorum signaling of pathogens from fresh fruits and vegetables.

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Amrutha, Balagopal; Sundar, Kothandapani; Shetty, Prathapkumar Halady

2017-10-01

Organic acids are known to be used as food preservatives due to their antimicrobial potential. This study evaluated the ability of three organic acids, namely, acetic acid, citric acid and lactic acid to manage E. coli and Salmonella sp. from fresh fruits and vegetables. Effect of these organic acids on biofilm forming ability and anti-quorum potential was also investigated. The effect of organic acids on inactivation of E. coli and Salmonella sp. on the surface of a selected vegetable (cucumber) was determined. The minimum inhibitory concentration of the organic acids were found to be 1.5, 2 and 0.2% in E. coli while it was observed to be 1, 1.5 and 1% in Salmonella sp. for acetic, citric and lactic acids respectively. Maximum inhibition of biofilm formation was recorded at 39.13% with lactic acid in E. coli and a minimum of 22.53% with citric acid in Salmonella sp. EPS production was affected in E. coli with lactic acid showing reduction by 13.42% while citric acid and acetic acid exhibited only 6.25% and 10.89% respectively. Swimming and swarming patterns in E. coli was notably affected by both acetic and lactic acids. Lactic and acetic acids showed higher anti-quorum sensing (QS) potential when compared to citric acid. 2% lactic acid showed a maximum inhibition of violacein production by 37.7%. Organic acids can therefore be used as potential quorum quenching agents in food industry. 2% lactic acid treatment on cucumber demonstrated that it was effective in inactivating E. coli and Salmonella sp. There was 1 log reduction in microbial count over a period of 6 days after the lactic acid treatment. Thus, organic acids can act as effective potential sanitizers in reducing the microbial load associated with fresh fruits and vegetables. Copyright © 2017 Elsevier Ltd. All rights reserved.

En rejse ind i dental biofilm

DEFF Research Database (Denmark)

Schlafer, Sebastian

Som klinkassistent og tandplejer arbejder man hver dag med bakteriel biofilm på tandoverfladerne – plak. Alle ved udmærket, at denne biofilm er ansvarlig for mundhulens hyppigste sygdomme, caries og parodontitis. Vi renser patienternes tænder for biofilm og opfordrer dem til at fjerne biofilmen...... mindst to gange om dagen, så grundigt de kan. Desuden bruges der en lang række antibakterielle tilsætningsstoffer i både tandpasta og mundskyllevæsker, hvis hovedformål er at dræbe bakterierne i dental biofilm. Men er biofilmen virkelig kun farlig? Nyere forskning har vist, at mennesket faktisk i høj...... grad er afhængig af de bakterier, der koloniserer kroppen. Hvorfor gælder dette tilsyneladende ikke for mundhulen? I løbet af præsentationen vil jeg tage tilhørerne med på en rejse ind i dental biofilm. Jeg vil belyse den komplekse bakterielle arkitektur, som kendetegner biofilmen, og vil analysere de...

Antimicrobial properties of Kalanchoe blossfeldiana: a focus on drug resistance with particular reference to quorum sensing-mediated bacterial biofilm formation.

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Sarkar, Ratul; Mondal, Chaitali; Bera, Rammohan; Chakraborty, Sumon; Barik, Rajib; Roy, Paramita; Kumar, Alekh; Yadav, Kirendra K; Choudhury, Jayanta; Chaudhary, Sushil K; Samanta, Samir K; Karmakar, Sanmoy; Das, Satadal; Mukherjee, Pulok K; Mukherjee, Joydeep; Sen, Tuhinadri

2015-07-01

This study attempts to investigate the antimicrobial properties of Kalanchoe blossfeldiana with a particular reference to quorum sensing (QS)-mediated biofilm formation. The methanol extract of K. blossfeldiana leaves (MEKB) was evaluated for antimicrobial properties including QS-controlled production of biofilm (including virulence factor, motility and lactone formation) in Pseudomonas aeruginosa. Methanol extract of K. blossfeldiana was also evaluated for anti-cytokine (tumour necrosis factor-alpha, interleukin-6 and interleukin-1 beta) properties in peripheral blood mononuclear cells (PBMC). Methanol extract of K. blossfeldiana exhibited antimicrobial effect on clinical isolates, as well as standard reference strains. Pseudomonas aeruginosa exposed to MEKB (subminimum inhibitory concentration (MIC)) displayed reduced biofilm formation, whereas supra-MIC produced destruction of preformed biofilms. Methanol extract of K. blossfeldiana reduced the secretion of virulence factors (protease and pyoverdin) along with generation of acyl homoserine lactone (AHL). Confocal laser scanning microscopy images indicate reduction of biofilm thickness. The extract also reduced cytokine formation in lipopolysaccharide-stimulated PBMC. Kalanchoe blossfeldiana was found to interfere with AHL production, which in turn may be responsible for downregulating QS-mediated production of biofilm and virulence. This first report on the antibiofilm and anticytokine properties of this plant may open up new vistas for future exploration of this plant for combating biofilm-related resistant infections. © 2015 Royal Pharmaceutical Society.

2-Furaldehyde diethyl acetal from tender coconut water (Cocos nucifera) attenuates biofilm formation and quorum sensing-mediated virulence of Chromobacterium violaceum and Pseudomonas aeruginosa.

Science.gov (United States)

Sethupathy, Sivasamy; Nithya, Chari; Pandian, Shunmugiah Karutha

2015-01-01

The aim of this study was to evaluate the anti-biofilm and quorum sensing inhibitory (QSI) potential of tender coconut water (TCW) against Chromobacterium violaceum and Pseudomonas aeruginosa. TCW significantly inhibited the QS regulated violacein, virulence factors and biofilm production without affecting their growth. qRT-PCR analysis revealed the down-regulation of autoinducer synthase, transcriptional regulator and virulence genes. Mass-spectrometric analysis of a petroleum ether extract of the TCW hydrolyte revealed that 2-furaldehyde diethyl acetal (2FDA) and palmitic acid (PA) are the major compounds. In vitro bioassays confirmed the ability of 2FDA to inhibit the biofilm formation and virulence factors. In addition, the combination of PA with 2FDA resulted in potent inhibition of biofilm formation and virulence factors. The results obtained strongly suggest that TCW can be exploited as a base for designing a novel antipathogenic drug formulation to treat biofilm mediated infections caused by P. aeruginosa.

Cold Plasma Inactivation of Bacterial Biofilms and Reduction of Quorum Sensing Regulated Virulence Factors.

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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

Quorum sensing and bacterial pathogenicity: From molecules to disease

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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.

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

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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.

Insights into the Quorum Sensing Regulon of the Acidophilic Acidithiobacillus ferrooxidans Revealed by Transcriptomic in the Presence of an Acyl Homoserine Lactone Superagonist Analogue

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Sigde Mamani

2016-09-01

Full Text Available While a functional quorum sensing system has been identified in the acidophilic chemolithoautotroph Acidithiobacillus ferrooxidans ATCC 23270T and shown to modulate cell adhesion to solid substrates, nothing is known about the genes it regulates. To address the question of how quorum sensing controls biofilm formation in At. ferrooxidansT, the transcriptome of this organism in conditions in which quorum sensing response is stimulated by a synthetic superagonist AHL analogue has been studied. First, the effect on biofilm formation of a synthetic AHL tetrazolic analogue, tetrazole 9c, known for its agonistic QS activity, was assessed by fluorescence and electron microscopy experiments. A faster adherence of At. ferrooxidansT cells on sulfur coupons was observed. Then, tetrazole 9c was used in DNA microarray experiments that allowed the identification of genes regulated by quorum sensing signalling, and more particularly, those involved in early biofilm formation. Interestingly, afeI gene, encoding the AHL synthase, but not the At. ferrooxidans quorum sensing transcriptional regulator AfeR encoding gene, was shown to be regulated by quorum sensing. Data indicated that QS network represents at least 4.5 % (141 genes of the ATCC 23270T genome of which 42.5 % (60 genes are related to biofilm formation. Finally, AfeR was shown to bind specifically to the regulatory region of the afeI gene at the level of the palindromic sequence predicted to be the AfeR binding site. Our results give new insights on the response of At. ferrooxidans to quorum sensing and on biofilm biogenesis, opening new biological/chemical alternatives for bioleaching development and managing acid Mine/Rock drainage environmental damages.

The contribution of cell-cell signaling and motility to bacterial biofilm formation

DEFF Research Database (Denmark)

Shrout, Joshua D; Tolker-Nielsen, Tim; Givskov, Michael

2011-01-01

Many bacteria grow attached to a surface as biofilms. Several factors dictate biofilm formation, including responses by the colonizing bacteria to their environment. Here we review how bacteria use cell-cell signaling (also called quorum sensing) and motility during biofilm formation. Specifically...... gene expression important to the production of polysaccharides, rhamnolipid, and other virulence factors. Surface motility affects the assembly and architecture of biofilms, and some aspects of motility are also influenced by quorum sensing. While some genes and their function are specific to P....... aeruginosa, many aspects of biofilm development can be used as a model system to understand how bacteria differentially colonize surfaces....

Microbial Biofilm as a Smart Material

DEFF Research Database (Denmark)

Garde, Christian; Welch, Martin; Ferkinghoff-Borg, Jesper

2015-01-01

Microbial biofilm colonies will in many cases form a smart material capable of responding to external threats dependent on their size and internal state. The microbial community accordingly switches between passive, protective, or attack modes of action. In order to decide which strategy to employ......, it is essential for the biofilm community to be able to sense its own size. The sensor designed to perform this task is termed a quorum sensor, since it only permits collective behaviour once a sufficiently large assembly of microbes have been established. The generic quorum sensor construct involves two genes...

Effects of Iron on DNA Release and Biofilm Development by Pseudomonas Aeruginosa

DEFF Research Database (Denmark)

Yang, Liang; Barken, Kim Bundvig; Skindersø, Mette Elena

2007-01-01

Extracellular DNA is one of the major matrix components in Pseudomonas aeruginosa biofilms. It functions as an intercellular connector and plays a role in stabilization of the biofilms. Evidence that DNA release in P. aeruginosa PAO1 biofilms is controlled by the las-rhl and pqs quorum-sensing sy......Extracellular DNA is one of the major matrix components in Pseudomonas aeruginosa biofilms. It functions as an intercellular connector and plays a role in stabilization of the biofilms. Evidence that DNA release in P. aeruginosa PAO1 biofilms is controlled by the las-rhl and pqs quorum......-sensing systems has been previously presented. This paper provides evidence that DNA release in P. aeruginosa PAO1 biofilms is also under iron regulation. Experiments involving cultivation of P. aeruginosa in microtitre trays suggested that pqs expression, DNA release and biofilm formation were favoured in media...

Recent progresses on AI-2 bacterial quorum sensing inhibitors.

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Zhu, Peng; Li, Minyong

2012-01-01

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

Design, Synthesis and Biological Evaluation of Quorum Sensing Modulators

DEFF Research Database (Denmark)

Hansen, Mette Reimert

to intercept the communication system by synthetic non-native ligands and thereby lower the pathogenesis and antibiotic tolerance of a bacterial biofilm. To identify new ligands with quorum sensing modulating activities, three types of AHL analogs were synthesized using different synthetic strategies....... Overall, 17 compounds were identified as quorum sensing activators with EC50 values in the low micromolar range. Two build/couple/pair strategies for the synthesis of structurally diverse small molecules are presented. In the first strategy, the Petasis 3-component reaction (Petasis 3-CR) of hydrazides...

Recent Advances in the Study of Marine Microbial Biofilm: From the Involvement of Quorum Sensing in Its Production up to Biotechnological Application of the Polysaccharide Fractions

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Paola Di Donato

2016-05-01

Full Text Available The present review will explore the most relevant findings on marine microbial biofilm, with particular attention towards its polysaccharide fraction, namely exopolysaccharide (EPS. EPSs of microbial origin are ubiquitous in nature, possess unique properties and can be isolated from the bacteria living in a variety of habitats, including fresh water or marine environments, extreme environments or different soil ecosystems. These biopolymers have many application in the field of biotechnology. Several studies showed that the biofilm formation is closely related to quorum sensing (QS systems, which is a mechanism relying on the production of small molecules defined as “autoinducers” that bacteria release in the surrounding environment where they accumulate. In this review, the involvement of microbial chemical communication, by QS mechanism, in the formation of marine biofilm will also be discussed.

Biogenic synthesis of Zinc oxide nanostructures from Nigella sativa seed: Prospective role as food packaging material inhibiting broad-spectrum quorum sensing and biofilm.

Science.gov (United States)

Al-Shabib, Nasser A; Husain, Fohad Mabood; Ahmed, Faheem; Khan, Rais Ahmad; Ahmad, Iqbal; Alsharaeh, Edreese; Khan, Mohd Shahnawaz; Hussain, Afzal; Rehman, Md Tabish; Yusuf, Mohammad; Hassan, Iftekhar; Khan, Javed Masood; Ashraf, Ghulam Md; Alsalme, Ali Mohammed; Al-Ajmi, Mohamed F; Tarasov, Vadim V; Aliev, Gjumrakch

2016-12-05

Bacterial spoilage of food products is regulated by density dependent communication system called quorum sensing (QS). QS control biofilm formation in numerous food pathogens and Biofilms formed on food surfaces act as carriers of bacterial contamination leading to spoilage of food and health hazards. Agents inhibiting or interfering with bacterial QS and biofilm are gaining importance as a novel class of next-generation food preservatives/packaging material. In the present study, Zinc nanostructures were synthesised using Nigella sativa seed extract (NS-ZnNPs). Synthesized nanostructures were characterized hexagonal wurtzite structure of size ~24 nm by UV-visible, XRD, FTIR and TEM. NS-ZnNPs demonstrated broad-spectrum QS inhibition in C. violaceum and P. aeruginosa biosensor strains. Synthesized nanostructures inhibited QS regulated functions of C. violaceum CVO26 (violacein) and elastase, protease, pyocyanin and alginate production in PAO1 significantly. NS-ZnNPs at sub-inhibitory concentrations inhibited the biofilm formation of four-food pathogens viz. C. violaceum 12472, PAO1, L. monocytogenes, E. coli. Moreover, NS-ZnNPs was found effective in inhibiting pre-formed mature biofilms of the four pathogens. Therefore, the broad-spectrum inhibition of QS and biofilm by biogenic Zinc oxide nanoparticles and it is envisaged that these nontoxic bioactive nanostructures can be used as food packaging material and/or as food preservative.

Qualitative and Quantitative Determination of Quorum Sensing Inhibition In Vitro

DEFF Research Database (Denmark)

Jakobsen, Tim Holm; Alhede, Maria; Hultqvist, Louise Dahl

2018-01-01

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 effic...

Fluoride in dental biofilm and saliva

DEFF Research Database (Denmark)

Larsen, Line Staun

Dette ph.d.-projekt bidrager med ny viden om fordelingen af fluorid i dental biofilm og saliva. For at udforske koncentrationen af fluorid i naturlig (in vivo) biofilmvæske, biofilmsediment og i saliva, blev der udført to meget forskellige kliniske studier. Resultaterne fra tværsnitsstudiet (Studie...... I), hos en stor gruppe mennesker (n=42) der konsulterede en tandklinik for behandling, bekræfter tidligere viden, at der findes en naturlig biologisk variation i fluoridkoncentrationerne i biofilm fra forskellige intra-orale regioner samt mellem biofilmvæske, biofilmsediment og saliva...... fluoridkoncentrationer i underkæbefronten, intermediære koncentrationer i alle tre overkæberegioner og de laveste koncentrationer i underkæbemolarregionerne. Begge studier viser at biofilmsedimentet indeholder størstedelen af fluorid i biofilm. Set i et bredere perspektiv viser fundene at der er et omvendt forhold...

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

DEFF Research Database (Denmark)

Yang, Liang; Liu, Yang; Sternberg, Claus

2010-01-01

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

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

KAUST Repository

Scarascia, Giantommaso; Wang, Tiannyu; Hong, Pei-Ying

2016-01-01

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

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

KAUST Repository

Scarascia, Giantommaso

2016-12-15

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

Garlic as an inhibitor of Pseudomonas aeruginosa quorum sensing in cystic fibrosis--a pilot randomized controlled trial

DEFF Research Database (Denmark)

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...

Indirect pathogenicity of Haemophilus influenzae and Moraxella catarrhalis in polymicrobial otitis media occurs via interspecies quorum signaling.

Science.gov (United States)

Armbruster, Chelsie E; Hong, Wenzhou; Pang, Bing; Weimer, Kristin E D; Juneau, Richard A; Turner, James; Swords, W Edward

2010-07-06

Otitis media (OM) is among the leading diseases of childhood and is caused by opportunists that reside within the nasopharynx, such as Haemophilus influenzae and Moraxella catarrhalis. As with most airway infections, it is now clear that OM infections involve multiple organisms. This study addresses the hypothesis that polymicrobial infection alters the course, severity, and/or treatability of OM disease. The results clearly show that coinfection with H. influenzae and M. catarrhalis promotes the increased resistance of biofilms to antibiotics and host clearance. Using H. influenzae mutants with known biofilm defects, these phenotypes were shown to relate to biofilm maturation and autoinducer-2 (AI-2) quorum signaling. In support of the latter mechanism, chemically synthesized AI-2 (dihydroxypentanedione [DPD]) promoted increased M. catarrhalis biofilm formation and resistance to antibiotics. In the chinchilla infection model of OM, polymicrobial infection promoted M. catarrhalis persistence beyond the levels seen in animals infected with M. catarrhalis alone. Notably, no such enhancement of M. catarrhalis persistence was observed in animals infected with M. catarrhalis and a quorum signaling-deficient H. influenzae luxS mutant strain. We thus conclude that H. influenzae promotes M. catarrhalis persistence within polymicrobial biofilms via interspecies quorum signaling. AI-2 may therefore represent an ideal target for disruption of chronic polymicrobial infections. Moreover, these results strongly imply that successful vaccination against the unencapsulated H. influenzae strains that cause airway infections may also significantly impact chronic M. catarrhalis disease by removing a reservoir of the AI-2 signal that promotes M. catarrhalis persistence within biofilm.

Establishing bacterial communities by 'word of mouth': LuxS and autoinducer 2 in biofilm development.

Science.gov (United States)

Hardie, Kim Rachael; Heurlier, Karin

2008-08-01

Multicellular bacterial communities (biofilms) abound in nature, and their successful formation and survival is likely to require cell-cell communication--including quorum sensing--to co-ordinate appropriate gene expression. The only mode of quorum sensing that is shared by both Gram-positive and Gram-negative bacteria involves the production of the signalling molecule autoinducer 2 by LuxS. A survey of the current literature reveals that luxS contributes to biofilm development in some bacteria. However, inconsistencies prevent biofilm development being attributed to the production of AI2 in all cases.

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

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Giantommaso Scarascia

2016-12-01

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

Regulation of Nicotine Tolerance by Quorum Sensing and High Efficiency of Quorum Quenching Under Nicotine Stress in Pseudomonas aeruginosa PAO1

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Huiming Tang

2018-03-01

Full Text Available Quorum sensing (QS regulates the behavior of bacterial populations and promotes their adaptation and survival under stress. As QS is responsible for the virulence of vast majority of bacteria, quorum quenching (QQ, the interruption of QS, has become an attractive therapeutic strategy. However, the role of QS in stress tolerance and the efficiency of QQ under stress in bacteria are seldom explored. In this study, we demonstrated that QS-regulated catalase (CAT expression and biofilm formation help Pseudomonas aeruginosa PAO1 resist nicotine stress. CAT activity and biofilm formation in wild type (WT and ΔrhlR strains are significantly higher than those in the ΔlasR strain. Supplementation of ΔlasI strain with 3OC12-HSL showed similar CAT activity and biofilm formation as those of the WT strain. LasIR circuit rather than RhlIR circuit is vital to nicotine tolerance. Acylase I significantly decreased the production of virulence factors, namely elastase, pyocyanin, and pyoverdine under nicotine stress compared to the levels observed in the absence of nicotine stress. Thus, QQ is more efficient under stress. To our knowledge, this is the first study to report that QS contributes to nicotine tolerance in P. aeruginosa. This work facilitates a better application of QQ for the treatment of bacterial infections, especially under stress.

Regulation of Nicotine Tolerance by Quorum Sensing and High Efficiency of Quorum Quenching Under Nicotine Stress in Pseudomonas aeruginosa PAO1.

Science.gov (United States)

Tang, Huiming; Zhang, Yunyun; Ma, Yifan; Tang, Mengmeng; Shen, Dongsheng; Wang, Meizhen

2018-01-01

Quorum sensing (QS) regulates the behavior of bacterial populations and promotes their adaptation and survival under stress. As QS is responsible for the virulence of vast majority of bacteria, quorum quenching (QQ), the interruption of QS, has become an attractive therapeutic strategy. However, the role of QS in stress tolerance and the efficiency of QQ under stress in bacteria are seldom explored. In this study, we demonstrated that QS-regulated catalase (CAT) expression and biofilm formation help Pseudomonas aeruginosa PAO1 resist nicotine stress. CAT activity and biofilm formation in wild type (WT) and Δ rhlR strains are significantly higher than those in the Δ lasR strain. Supplementation of Δ lasI strain with 3OC12-HSL showed similar CAT activity and biofilm formation as those of the WT strain. LasIR circuit rather than RhlIR circuit is vital to nicotine tolerance. Acylase I significantly decreased the production of virulence factors, namely elastase, pyocyanin, and pyoverdine under nicotine stress compared to the levels observed in the absence of nicotine stress. Thus, QQ is more efficient under stress. To our knowledge, this is the first study to report that QS contributes to nicotine tolerance in P. aeruginosa . This work facilitates a better application of QQ for the treatment of bacterial infections, especially under stress.

Isolate-specific effects of patulin, penicillic Acid and EDTA on biofilm formation and growth of dental unit water line biofilm isolates.

Science.gov (United States)

Liaqat, Iram; Bachmann, Robert Thomas; Sabri, Anjum Nasim; Edyvean, Robert G J

2010-08-01

Dental unit water line (DUWL) contamination by opportunistic pathogens has its significance in nosocomial infection of patients, health care workers, and life-threatening infections to immunocompromized persons. Recently, the quorum sensing (QS) system of DUWL isolates has been found to affect their biofilm-forming ability, making it an attractive target for antimicrobial therapy. In this study, the effect of two quorum-sensing inhibitory compounds (patulin; PAT, penicillic acid; PA) and EDTA on planktonic growth, AI-2 signalling and in vitro biofilm formation of Pseudomonas aeruginosa, Achromobacter xylosoxidans and Achromobacter sp. was monitored. Vibrio harveyi BB170 bioassay and crystal violet staining methods were used to detect the AI-2 monitoring and biofilm formation in DUWL isolates, respectively. The V. harveyi BB170 bioassay failed to induce bioluminescence in A. xylosoxidans and Achromobacter sp., while P. aeruginosa showed AI-2 like activity suggesting the need of some pretreatments prior to bioassay. All strains were found to form biofilms within 72 h of incubation. The QSIs/EDTA combination have isolate-specific effects on biofilm formation and in some cases it stimulated biofilm formation as often as it was inhibited. However, detailed information about the anti-biofilm effect of these compounds is still lacking.

Scaffold of Selenium Nanovectors and Honey Phytochemicals for Inhibition of Pseudomonas aeruginosa Quorum Sensing and Biofilm Formation

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Prateeksha

2017-03-01

Full Text Available Honey is an excellent source of polyphenolic compounds that are effective in attenuating quorum sensing (QS, a chemical process of cell-to-cell communication system used by the opportunistic pathogen Pseudomonas aeruginosa to regulate virulence and biofilm formation. However, lower water solubility and inadequate bioavailability remains major concerns of these therapeutic polyphenols. Its therapeutic index can be improved by using nano-carrier systems to target QS signaling potently. In the present study, we fabricated a unique drug delivery system comprising selenium nanoparticles (SeNPs; non-viral vectors and polyphenols of honey (HP for enhancement of anti-QS activity of HP against P. aeruginosa PAO1. The developed selenium nano-scaffold showed superior anti-QS activity, anti-biofilm efficacy, and anti-virulence potential in both in-vitro and in-vivo over its individual components, SeNPs and HP. LasR is inhibited by selenium nano-scaffold in-vitro. Using computational molecular docking studies, we have also demonstrated that the anti-virulence activity of selenium nano-scaffold is reliant on molecular binding that occurs between HP and the QS receptor LasR through hydrogen bonding and hydrophobic interactions. Our preliminary investigations with selenium-based nano-carriers hold significant promise to improve anti-virulence effectiveness of phytochemicals by enhancing effective intracellular delivery.

Flavonoids Suppress Pseudomonas aeruginosa Virulence through Allosteric Inhibition of Quorum-sensing Receptors*

Science.gov (United States)

Paczkowski, Jon E.; Mukherjee, Sampriti; McCready, Amelia R.; Cong, Jian-Ping; Aquino, Christopher J.; Kim, Hahn; Henke, Brad R.; Smith, Chari D.; Bassler, Bonnie L.

2017-01-01

Quorum sensing is a process of cell-cell communication that bacteria use to regulate collective behaviors. Quorum sensing depends on the production, detection, and group-wide response to extracellular signal molecules called autoinducers. In many bacterial species, quorum sensing controls virulence factor production. Thus, disrupting quorum sensing is considered a promising strategy to combat bacterial pathogenicity. Several members of a family of naturally produced plant metabolites called flavonoids inhibit Pseudomonas aeruginosa biofilm formation by an unknown mechanism. Here, we explore this family of molecules further, and we demonstrate that flavonoids specifically inhibit quorum sensing via antagonism of the autoinducer-binding receptors, LasR and RhlR. Structure-activity relationship analyses demonstrate that the presence of two hydroxyl moieties in the flavone A-ring backbone are essential for potent inhibition of LasR/RhlR. Biochemical analyses reveal that the flavonoids function non-competitively to prevent LasR/RhlR DNA binding. Administration of the flavonoids to P. aeruginosa alters transcription of quorum sensing-controlled target promoters and suppresses virulence factor production, confirming their potential as anti-infectives that do not function by traditional bacteriocidal or bacteriostatic mechanisms. PMID:28119451

Synergistic antibacterial efficacy of early combination treatment with tobramycin and quorum-sensing inhibitors against Pseudomonas aeruginosa in an intraperitoneal foreign-body infection mouse model

DEFF Research Database (Denmark)

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...

Pseudomonas aeruginosa Biofilms

DEFF Research Database (Denmark)

Alhede, Maria; Bjarnsholt, Thomas; Givskov, Michael

2014-01-01

biofilms, which protect the aggregated, biopolymer-embedded bacteria from the detrimental actions of antibiotic treatments and host immunity. A key component in the protection against innate immunity is rhamnolipid, which is a quorum sensing (QS)-regulated virulence factor. QS is a cell-to-cell signaling...... mechanism used to coordinate expression of virulence and protection of aggregated biofilm cells. Rhamnolipids are known for their ability to cause hemolysis and have been shown to cause lysis of several cellular components of the human immune system, for example, macrophages and polymorphonuclear leukocytes...

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

Digital Repository Service at National Institute of Oceanography (India)

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

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

Microbial Biofilm as a Smart Material

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Christian Garde

2015-02-01

Full Text Available Microbial biofilm colonies will in many cases form a smart material capable of responding to external threats dependent on their size and internal state. The microbial community accordingly switches between passive, protective, or attack modes of action. In order to decide which strategy to employ, it is essential for the biofilm community to be able to sense its own size. The sensor designed to perform this task is termed a quorum sensor, since it only permits collective behaviour once a sufficiently large assembly of microbes have been established. The generic quorum sensor construct involves two genes, one coding for the production of a diffusible signal molecule and one coding for a regulator protein dedicated to sensing the signal molecules. A positive feedback in the signal molecule production sets a well-defined condition for switching into the collective mode. The activation of the regulator involves a slow dimerization, which allows low-pass filtering of the activation of the collective mode. Here, we review and combine the model components that form the basic quorum sensor in a number of Gram-negative bacteria, e.g., Pseudomonas aeruginosa.

Designer cells programming quorum-sensing interference with microbes.

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Sedlmayer, Ferdinand; Hell, Dennis; Müller, Marius; Ausländer, David; Fussenegger, Martin

2018-05-08

Quorum sensing is a promising target for next-generation anti-infectives designed to address evolving bacterial drug resistance. The autoinducer-2 (AI-2) is a key quorum-sensing signal molecule which regulates bacterial group behaviors and is recognized by many Gram-negative and Gram-positive bacteria. Here we report a synthetic mammalian cell-based microbial-control device that detects microbial chemotactic formyl peptides through a formyl peptide sensor (FPS) and responds by releasing AI-2. The microbial-control device was designed by rewiring an artificial receptor-based signaling cascade to a modular biosynthetic AI-2 production platform. Mammalian cells equipped with the microbial-control gene circuit detect formyl peptides secreted from various microbes with high sensitivity and respond with robust AI-2 production, resulting in control of quorum sensing-related behavior of pathogenic Vibrio harveyi and attenuation of biofilm formation by the human pathogen Candida albicans. The ability to manipulate mixed microbial populations through fine-tuning of AI-2 levels may provide opportunities for future anti-infective strategies.

Development of Topical Treatment for Pseudomonas aeruginosa Wound Infections by Quorum-Sensing Inhibitors Mediated by Poly(amidoamine) (PAMAM) Dendrimers

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2013-01-01

dendrimers would provide added benefits as a delivery vehicle of QSI compounds to inhibit PA biofilms, by both increasing the transport of QSI as drug...Pseudomonas aeruginosa Wound Infections by Quorum-Sensing Inhibitors Mediated by Poly(amidoamine) (PAMAM) Dendrimers PRINCIPAL INVESTIGATOR...Development of Topical Treatment for Pseudomonas aeruginosa Wound Infections by Quorum-Sensing Inhibitors Mediated by Poly(amidoamine) (PAMAM) Dendrimers

Antibiotic resistance in Pseudomonas aeruginosa biofilms: towards the development of novel anti-biofilm therapies.

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Taylor, Patrick K; Yeung, Amy T Y; Hancock, Robert E W

2014-12-10

The growth of bacteria as structured aggregates termed biofilms leads to their protection from harsh environmental conditions such as physical and chemical stresses, shearing forces, and limited nutrient availability. Because of this highly adapted ability to survive adverse environmental conditions, bacterial biofilms are recalcitrant to antibiotic therapies and immune clearance. This is particularly problematic in hospital settings where biofilms are a frequent cause of chronic and device-related infections and constitute a significant burden on the health-care system. The major therapeutic strategy against infections is the use of antibiotics, which, due to adaptive resistance, are often insufficient to clear biofilm infections. Thus, novel biofilm-specific therapies are required. Specific features of biofilm development, such as surface adherence, extracellular matrix formation, quorum sensing, and highly regulated biofilm maturation and dispersal are currently being studied as targets to be exploited in the development of novel biofilm-specific treatments. Using Pseudomonas aeruginosa for illustrative purposes, this review highlights the antibiotic resistance mechanisms of biofilms, and discusses current research into novel biofilm-specific therapies. Copyright © 2014 Elsevier B.V. All rights reserved.

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

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Bjarnsholt, Thomas; Jensen, P. Ø.; Rasmussen, Thomas Bovbjerg

2005-01-01

The opportunistic human pathogen Pseudomonas aeruginosa is the predominant micro-organism of chronic lung infections in cystic fibrosis patients. P. aeruginosa colonizes the lungs by forming biofilm microcolonies throughout the lung. Quorum sensing (QS) renders the biofilm bacteria highly tolerant......-treated biofilm. Garlic extract was administered as treatment for a mouse pulmonary infection model. Mice were treated with garlic extract or placebo for 7 days, with the initial 2 days being prophylactic before P. aeruginosa was instilled in the left lung of the mice. Bacteriology, mortality, histopathology...... and phagocytosis by PMNs, as well as leading to an improved outcome of pulmonary infections....

Heterogeneity of biofilms formed by nonmucoid Pseudomonas aeruginosa isolates from patients with cystic fibrosis

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Lee, Baoleri; Haagensen, Janus Anders Juul; Ciofu, O.

2005-01-01

lactone quorum-sensing molecules). Compared with wild-type strain PAO 1, most P. aeruginosa isolates demonstrated different degrees of reduction of adherence on polystyrene surfaces. The in vitro biofilm formation of isolates was investigated in a hydrodynamic flow system. Confocal laser scanning...... to phenotypic changes and in vitro biofilm formation. The physiological alterations were associated with a loss of motility (35% were nonmotile) and with decreased production of virulence factors (pyocyanin, proteases) and quorum-sensing molecules (45% of the isolates were unable to produce 3-O-C(12)-homoserine...

Experimental and Theoretical Investigation of Multispecies Oral Biofilm Resistance to Chlorhexidine Treatment

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Shen, Ya; Zhao, Jia; de La Fuente-Núñez, César; Wang, Zhejun; Hancock, Robert E. W.; Roberts, Clive R.; Ma, Jingzhi; Li, Jun; Haapasalo, Markus; Wang, Qi

2016-06-01

We investigate recovery of multispecies oral biofilms following chlorhexidine gluconate (CHX) and CHX with surface modifiers (CHX-Plus) treatment. Specifically, we examine the percentage of viable bacteria in the biofilms following their exposure to CHX and CHX-Plus for 1, 3, and 10 minutes, respectively. Before antimicrobial treatment, the biofilms are allowed to grow for three weeks. We find that (a). CHX-Plus kills bacteria in biofilms more effectively than the regular 2% CHX does, (b). cell continues to be killed for up to one week after exposure to the CHX solutions, (c). the biofilms start to recover after two weeks, the percentage of the viable bacteria recovers in the 1 and 3 minutes treatment groups but not in the 10 minutes treatment group after five weeks, and the biofilms fully return to the pretreatment levels after eight weeks. To understand the mechanism, a mathematical model for multiple bacterial phenotypes is developed, adopting the notion that bacterial persisters exist in the biofilms together with regulatory quorum sensing molecules and growth factor proteins. The model reveals the crucial role played by the persisters, quorum sensing molecules, and growth factors in biofilm recovery, accurately predicting the viable bacterial population after CHX treatment.

Experimental and Theoretical Investigation of Multispecies Oral Biofilm Resistance to Chlorhexidine Treatment

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Shen, Ya; Zhao, Jia; de la Fuente-Núñez, César; Wang, Zhejun; Hancock, Robert E. W.; Roberts, Clive R.; Ma, Jingzhi; Li, Jun; Haapasalo, Markus; Wang, Qi

2016-01-01

We investigate recovery of multispecies oral biofilms following chlorhexidine gluconate (CHX) and CHX with surface modifiers (CHX-Plus) treatment. Specifically, we examine the percentage of viable bacteria in the biofilms following their exposure to CHX and CHX-Plus for 1, 3, and 10 minutes, respectively. Before antimicrobial treatment, the biofilms are allowed to grow for three weeks. We find that (a). CHX-Plus kills bacteria in biofilms more effectively than the regular 2% CHX does, (b). cell continues to be killed for up to one week after exposure to the CHX solutions, (c). the biofilms start to recover after two weeks, the percentage of the viable bacteria recovers in the 1 and 3 minutes treatment groups but not in the 10 minutes treatment group after five weeks, and the biofilms fully return to the pretreatment levels after eight weeks. To understand the mechanism, a mathematical model for multiple bacterial phenotypes is developed, adopting the notion that bacterial persisters exist in the biofilms together with regulatory quorum sensing molecules and growth factor proteins. The model reveals the crucial role played by the persisters, quorum sensing molecules, and growth factors in biofilm recovery, accurately predicting the viable bacterial population after CHX treatment. PMID:27325010

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

DEFF Research Database (Denmark)

Bjarnsholt, Thomas; Jensen, P.O.; Burmolle, M.

2005-01-01

to otherwise lethal doses of antibiotics and are protected from bactericidal activity of polymorphonuclear leukocytes (PMNs). P. aeruginosa controls the expression of many of its virulence factors by means of a cell-cell communication system termed quorum sensing (QS). In the present report it is demonstrated...... that biofilm bacteria in which QS is blocked either by mutation or by administration of QS inhibitory drugs are sensitive to treatment with tobramycin and H2O2, and are readily phagocytosed by PMNs, in contrast to bacteria with functional QS systems. In contrast to the wild-type, QS-deficient biofilms led...... to an immediate respiratory-burst activation of the PMNs in vitro. In vivo QS-deficient mutants provoked a higher degree of inflammation. It is suggested that quorum signals and QS-inhibitory drugs play direct and opposite roles in this process. Consequently, the faster and highly efficient clearance of QS-deficient...

Development of Quorum-Based Anti-Virulence Therapeutics Targeting Gram-Negative Bacterial Pathogens

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Wen Shan Yew

2013-08-01

Full Text Available Quorum sensing is a cell density-dependent signaling phenomenon used by bacteria for coordination of population-wide phenotypes, such as expression of virulence genes, antibiotic resistance and biofilm formation. Lately, disruption of bacterial communication has emerged as an anti-virulence strategy with enormous therapeutic potential given the increasing incidences of drug resistance in pathogenic bacteria. The quorum quenching therapeutic approach promises a lower risk of resistance development, since interference with virulence generally does not affect the growth and fitness of the bacteria and, hence, does not exert an associated selection pressure for drug-resistant strains. With better understanding of bacterial communication networks and mechanisms, many quorum quenching methods have been developed against various clinically significant bacterial pathogens. In particular, Gram-negative bacteria are an important group of pathogens, because, collectively, they are responsible for the majority of hospital-acquired infections. Here, we discuss the current understanding of existing quorum sensing mechanisms and present important inhibitory strategies that have been developed against this group of pathogenic bacteria.

Biofilm production by clinical isolates of Pseudomonas aeruginosa and structural changes in LasR protein of isolates non biofilm-producing

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Jailton Lobo da Costa Lima

2018-03-01

Full Text Available Introduction: Biofilm production is an important mechanism for the survival of Pseudomonas aeruginosa and its relationship with antimicrobial resistance represents a challenge for patient therapeutics. P. aeruginosa is an opportunistic pathogen frequently associated to nosocomial infections, especially in imunocompromised hosts. Objectives: Analyze the phenotypic biofilm production in P. aeruginosa isolates, describe clonal profiles, and analyze quorum sensing (QS genes and the occurrence of mutations in the LasR protein of non-biofilm producing isolates. Methods: Isolates were tested for biofilm production by measuring cells adherence to the microtiter plates. Clonal profile analysis was carried out through ERIC-PCR, QS genes were by specific PCR. Results: The results showed that 77.5% of the isolates were considered biofilm producers. The results of genotyping showed 38 distinct genetic profiles. As for the occurrence of the genes, 100% of the isolates presented the lasR, rhlI and rhlR genes, and 97.5%, presented the lasI gene. In this study nine isolates were not biofilm producers. However, all presented the QS genes. Amplicons related to genes were sequenced in three of the nine non-biofilm-producing isolates (all presenting different genetic similarity profile and aligned to the sequences of those genes in P. aeruginosa strain PAO1 (standard biofilm-producing strain. Alignment analysis showed an insertion of three nucleotides (T, C and G causing the addition of an amino acid valine in the sequence of the LasR protein, in position 53. Conclusion: The modeling of the resulting LasR protein showed a conformational change in its structure, suggesting that this might be the reason why these isolates are unable to produce biofilm. Keywords: Pseudomonas aeruginosa, Biofilm, Multiresistance, Quorum sensing (QS

Direct evaluation of Pseudomonas aeruginosa biofilm mediators in a chronic infection model.

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Byrd, Matthew S; Pang, Bing; Hong, Wenzhou; Waligora, Elizabeth A; Juneau, Richard A; Armbruster, Chelsie E; Weimer, Kristen E D; Murrah, Kyle; Mann, Ethan E; Lu, Haiping; Sprinkle, April; Parsek, Matthew R; Kock, Nancy D; Wozniak, Daniel J; Swords, W Edward

2011-08-01

Biofilms contribute to Pseudomonas aeruginosa persistence in a variety of diseases, including cystic fibrosis, burn wounds, and chronic suppurative otitis media. However, few studies have directly addressed P. aeruginosa biofilms in vivo. We used a chinchilla model of otitis media, which has previously been used to study persistent Streptococcus pneumoniae and Haemophilus influenzae infections, to show that structures formed in vivo are biofilms of bacterial and host origin within a matrix that includes Psl, a P. aeruginosa biofilm polysaccharide. We evaluated three biofilm and/or virulence mediators of P. aeruginosa known to affect biofilm formation in vitro and pathogenesis in vivo--bis-(3',5')-cyclic dimeric GMP (c-di-GMP), flagella, and quorum sensing--in a chinchilla model. We show that c-di-GMP overproduction has a positive impact on bacterial persistence, while quorum sensing increases virulence. We found no difference in persistence attributed to flagella. We conclude from these studies that a chinchilla otitis media model provides a means to evaluate pathogenic mediators of P. aeruginosa and that in vitro phenotypes should be examined in multiple infection systems to fully understand their role in disease.

Leaf Extracts of Mangifera indica L. Inhibit Quorum Sensing – Regulated Production of Virulence Factors and Biofilm in Test Bacteria

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Iqbal Ahmad

2017-04-01

Full Text Available Quorum sensing (QS is a global gene regulatory mechanism in bacteria for various traits including virulence factors. Disabling QS system with anti-infective agent is considered as a potential strategy to prevent bacterial infection. Mangifera indica L. (mango has been shown to possess various biological activities including anti-QS. This study investigates the efficacy of leaf extracts on QS-regulated virulence factors and biofilm formation in Gram negative pathogens. Mango leaf (ML extract was tested for QS inhibition and QS-regulated virulence factors using various indicator strains. It was further correlated with the biofilm inhibition and confirmed by electron microscopy. Phytochemical analysis was carried out using ultra performance liquid chromatography (UPLC and gas chromatography–mass spectrometry (GC-MS analysis. In vitro evaluation of anti-QS activity of ML extracts against Chromobacterium violaceum revealed promising dose-dependent interference in violacein production, by methanol extract. QS inhibitory activity is also demonstrated by reduction in elastase (76%, total protease (56%, pyocyanin (89%, chitinase (55%, exopolysaccharide production (58% and swarming motility (74% in Pseudomonas aeruginosa PAO1 at 800 μg/ml concentration. Biofilm formation by P. aeruginosa PAO1 and Aeromonas hydrophila WAF38 was reduced considerably (36–82% over control. The inhibition of biofilm was also observed by scanning electron microscopy. Moreover, ML extracts significantly reduced mortality of Caenorhabditis elegans pre-infected with PAO1 at the tested concentration. Phytochemical analysis of active extracts revealed very high content of phenolics in methanol extract and a total of 14 compounds were detected by GC-MS and UPLC. These findings suggest that phytochemicals from the ML could provide bioactive anti-infective and needs further investigation to isolate and uncover their therapeutic efficacy.

Leaf Extracts of Mangifera indica L. Inhibit Quorum Sensing – Regulated Production of Virulence Factors and Biofilm in Test Bacteria

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Husain, Fohad M.; Ahmad, Iqbal; Al-thubiani, Abdullah S.; Abulreesh, Hussein H.; AlHazza, Ibrahim M.; Aqil, Farrukh

2017-01-01

Quorum sensing (QS) is a global gene regulatory mechanism in bacteria for various traits including virulence factors. Disabling QS system with anti-infective agent is considered as a potential strategy to prevent bacterial infection. Mangifera indica L. (mango) has been shown to possess various biological activities including anti-QS. This study investigates the efficacy of leaf extracts on QS-regulated virulence factors and biofilm formation in Gram negative pathogens. Mango leaf (ML) extract was tested for QS inhibition and QS-regulated virulence factors using various indicator strains. It was further correlated with the biofilm inhibition and confirmed by electron microscopy. Phytochemical analysis was carried out using ultra performance liquid chromatography (UPLC) and gas chromatography–mass spectrometry (GC-MS) analysis. In vitro evaluation of anti-QS activity of ML extracts against Chromobacterium violaceum revealed promising dose-dependent interference in violacein production, by methanol extract. QS inhibitory activity is also demonstrated by reduction in elastase (76%), total protease (56%), pyocyanin (89%), chitinase (55%), exopolysaccharide production (58%) and swarming motility (74%) in Pseudomonas aeruginosa PAO1 at 800 μg/ml concentration. Biofilm formation by P. aeruginosa PAO1 and Aeromonas hydrophila WAF38 was reduced considerably (36–82%) over control. The inhibition of biofilm was also observed by scanning electron microscopy. Moreover, ML extracts significantly reduced mortality of Caenorhabditis elegans pre-infected with PAO1 at the tested concentration. Phytochemical analysis of active extracts revealed very high content of phenolics in methanol extract and a total of 14 compounds were detected by GC-MS and UPLC. These findings suggest that phytochemicals from the ML could provide bioactive anti-infective and needs further investigation to isolate and uncover their therapeutic efficacy. PMID:28484444

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

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

2017-04-01

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

The small nucleoid protein Fis is involved in Vibrio cholerae quorum sensing.

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Lenz, Derrick H; Bassler, Bonnie L

2007-02-01

Quorum sensing is a process of cell-cell communication that bacteria use to relay information to one another about the cell density and species composition of the bacterial community. Quorum sensing involves the production, secretion and population-wide detection of small signalling molecules called autoinducers. This process allows bacteria to synchronize group behaviours and act as multicellular units. The human pathogen, Vibrio cholerae, uses quorum sensing to co-ordinate such complex behaviours as pathogenicity and biofilm formation. The quorum-sensing circuit of V. cholerae consists of two autoinducer/sensor systems, CAI-1/CqsS and AI-2/LuxPQ, and the VarS/A-CsrA/BCD growth-phase regulatory system. Genetic analysis suggests that an additional regulatory arm involved in quorum sensing exists in V. cholerae. All of these systems channel information into the histidine phosphotransfer protein, LuxU, and/or the response regulator, LuxO. LuxO, when phosphorylated, activates the expression of four genes encoding the Qrr (quorum regulatory RNAs) small RNAs (sRNAs). The Qrr sRNAs destabilize the hapR transcript encoding the master regulator of quorum sensing, HapR. Here we identify the nucleoid protein Fis as playing a major role in the V. cholerae quorum-sensing circuit. Fis fulfils the predictions required to be the putative additional component that inputs information into the cascade: its expression is regulated in a growth phase-dependent manner; it requires LuxO but acts independently of LuxU, and it regulates all four qrr genes and, in turn, HapR by directly binding to the qrr gene promoters and modulating their expression.

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

DEFF Research Database (Denmark)

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

2004-01-01

Introduction: Antibiotics are used to treat bacterial infections by killing the bacteria or inhibiting their growth, but resistance to antibiotics can develop readily. The discovery that bacterial quorum-sensing regulates bacterial virulence as well as the formation of biofilms opens up new ways...... 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...

Interference of Pseudomonas aeruginosa signalling and biofilm formation for infection control

DEFF Research Database (Denmark)

Bjarnsholt, Thomas; Tolker-Nielsen, Tim; Høiby, Niels

2010-01-01

Pseudomonas aeruginosa is the best described bacterium with regards to quorum sensing (QS), in vitro biofilm formation and the development of antibiotic tolerance. Biofilms composed of P. aeruginosa are thought to be the underlying cause of many chronic infections, including those in wounds...... and in the lungs of patients with cystic fibrosis. In this review, we provide an overview of the molecular mechanisms involved in QS, QS-enabled virulence, biofilm formation and biofilm-enabled antibiotic tolerance. We now have substantial knowledge of the multicellular behaviour of P. aeruginosa in vitro. A major...

Bacterial signaling ecology and potential applications during aquatic biofilm construction.

Science.gov (United States)

Vega, Leticia M; Alvarez, Pedro J; McLean, Robert J C

2014-07-01

In their natural environment, bacteria and other microorganisms typically grow as surface-adherent biofilm communities. Cell signal processes, including quorum signaling, are now recognized as being intimately involved in the development and function of biofilms. In contrast to their planktonic (unattached) counterparts, bacteria within biofilms are notoriously resistant to many traditional antimicrobial agents and so represent a major challenge in industry and medicine. Although biofilms impact many human activities, they actually represent an ancient mode of bacterial growth as shown in the fossil record. Consequently, many aquatic organisms have evolved strategies involving signal manipulation to control or co-exist with biofilms. Here, we review the chemical ecology of biofilms and propose mechanisms whereby signal manipulation can be used to promote or control biofilms.

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

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

2015-05-01

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

Biofilm ved kronisk rhinosinuitis og cystisk fibrose

DEFF Research Database (Denmark)

Fisker, Jacob; Buchwald, Christian von; Johansen, Helle Krogh

2011-01-01

Microbial biofilms are known to cause persistent foreign-body infections and have recently been acknowledged as involved in more than 65% of all human infections. Microbial biofilms have been detected in chronic rhinosinusitis, and chronic rhinosinusitis is mandatory in patients with cystic...

Characterisation of two quorum sensing systems in the endophytic Serratia plymuthica strain G3: differential control of motility and biofilm formation according to life-style.

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Liu, Xiaoguang; Jia, Jinli; Popat, Roman; Ortori, Catherine A; Li, Jun; Diggle, Stephen P; Gao, Kexiang; Cámara, Miguel

2011-02-01

N-acylhomoserine lactone (AHL)-based quorum sensing (QS) systems have been described in many plant-associated Gram-negative bacteria to control certain beneficial phenotypic traits, such as production of biocontrol factors and plant growth promotion. However, the role of AHL-mediated signalling in the endophytic strains of plant-associated Serratia is still poorly understood. An endophytic Serratia sp. G3 with biocontrol potential and high levels of AHL signal production was isolated from the stems of wheat and the role of QS in this isolate was determined. Strain G3 classified as Serratia plymuthica based on 16S rRNA was subjected to phylogenetic analysis. Using primers to conserved sequences of luxIR homologues from the Serratia genus, splIR and spsIR from the chromosome of strain G3 were cloned and sequenced. AHL profiles from strain G3 and Escherichia coli DH5α expressing splI or spsI from recombinant plasmids were identified by liquid chromatography-tandem mass spectrometry. This revealed that the most abundant AHL signals produced by SplI in E. coli were N-3-oxo-hexanoylhomoserine lactone (3-oxo-C6-HSL), N-3-oxo-heptanoylhomoserine lactone (3-oxo-C7-HSL), N-3-hydroxy-hexanoylhomoserine lactone (3-hydroxy-C6-HSL), N-hexanoylhomoserine lactone (C6-HSL), and N-heptanoyl homoserine lactone (C7-HSL); whereas SpsI was primarily responsible for the synthesis of N-butyrylhomoserine lactone (C4-HSL) and N-pentanoylhomoserine lactone (C5-HSL). Furthermore, a quorum quenching analysis by heterologous expression of the Bacillus A24 AiiA lactonase in strain G3 enabled the identification of the AHL-regulated biocontrol-related traits. Depletion of AHLs with this lactonase resulted in altered adhesion and biofilm formation using a microtiter plate assay and flow cells coupled with confocal laser scanning microscopy respectively. This was different from the closely related S. plymuthica strains HRO-C48 and RVH1, where biofilm formation for both strains is AHL

Characterisation of two quorum sensing systems in the endophytic Serratia plymuthica strain G3: differential control of motility and biofilm formation according to life-style

Directory of Open Access Journals (Sweden)

Li Jun

2011-02-01

Full Text Available Abstract Background N-acylhomoserine lactone (AHL-based quorum sensing (QS systems have been described in many plant-associated Gram-negative bacteria to control certain beneficial phenotypic traits, such as production of biocontrol factors and plant growth promotion. However, the role of AHL-mediated signalling in the endophytic strains of plant-associated Serratia is still poorly understood. An endophytic Serratia sp. G3 with biocontrol potential and high levels of AHL signal production was isolated from the stems of wheat and the role of QS in this isolate was determined. Results Strain G3 classified as Serratia plymuthica based on 16S rRNA was subjected to phylogenetic analysis. Using primers to conserved sequences of luxIR homologues from the Serratia genus, splIR and spsIR from the chromosome of strain G3 were cloned and sequenced. AHL profiles from strain G3 and Escherichia coli DH5α expressing splI or spsI from recombinant plasmids were identified by liquid chromatography-tandem mass spectrometry. This revealed that the most abundant AHL signals produced by SplI in E. coli were N-3-oxo-hexanoylhomoserine lactone (3-oxo-C6-HSL, N-3-oxo-heptanoylhomoserine lactone (3-oxo-C7-HSL, N-3-hydroxy-hexanoylhomoserine lactone (3-hydroxy-C6-HSL, N-hexanoylhomoserine lactone (C6-HSL, and N-heptanoyl homoserine lactone (C7-HSL; whereas SpsI was primarily responsible for the synthesis of N-butyrylhomoserine lactone (C4-HSL and N-pentanoylhomoserine lactone (C5-HSL. Furthermore, a quorum quenching analysis by heterologous expression of the Bacillus A24 AiiA lactonase in strain G3 enabled the identification of the AHL-regulated biocontrol-related traits. Depletion of AHLs with this lactonase resulted in altered adhesion and biofilm formation using a microtiter plate assay and flow cells coupled with confocal laser scanning microscopy respectively. This was different from the closely related S. plymuthica strains HRO-C48 and RVH1, where biofilm formation

[Biofilms and their significance in medical microbiology].

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Cernohorská, L; Votava, M

2002-11-01

Microorganisms are able to adhere to various surfaces and to form there a three-dimensional structure known as biofilm. In biofilms, microbial cells show characteristics and behaviours different from those of plankton cells. Intercellular signalizations of the quorum-sensing type regulate interaction between members of the biofilm. Bacteria embedded in the biofilm can escape and form well known planktonic forms, that are obviously only a part of the bacterial life cycle. Bacteria adhere also to medically important surfaces such as catheters, either urinary or intravenous ones, artificial heart valves, orthopedic implants and so on and contribute to device-related infections like cystitis, catheter-related sepsis, endocarditis etc. Once a biofilm has been established on a surface, the bacteria harboured inside are less exposed to the host's immune response and less susceptible to antibiotics. As an important cause of nosocomial infections the biofilm must remain in the centre of the microbiologist's attention.

Pseudomonas aeruginosa forms Biofilms in Acute InfectionIndependent of Cell-to-Cell Signaling

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Schaber, J. Andy; Triffo, W.J.; Suh, Sang J.; Oliver, Jeffrey W.; Hastert, Mary C.; Griswold, John A.; Auer, Manfred; Hamood, Abdul N.; Rumbaugh, Kendra P.

2006-09-20

Biofilms are bacterial communities residing within a polysaccharide matrix that are associated with persistence and antibiotic resistance in chronic infections. We show that the opportunistic pathogen Pseudomonas aeruginosa forms biofilms within 8 hours of infection in thermally-injured mice, demonstrating that biofilms contribute to bacterial colonization in acute infections. P. aeruginosa biofilms were visualized within burned tissue surrounding blood vessels and adipose cells. Although quorum sensing (QS), a bacterial signaling mechanism, coordinates differentiation of biofilms in vitro, wild type and QS-deficient P. aeruginosa formed similar biofilms in vivo. Our findings demonstrate that P. aeruginosa forms biofilms on specific host tissues independent of QS.

Patterned biofilm formation reveals a mechanism for structural heterogeneity in bacterial biofilms.

Science.gov (United States)

Gu, Huan; Hou, Shuyu; Yongyat, Chanokpon; De Tore, Suzanne; Ren, Dacheng

2013-09-03

Bacterial biofilms are ubiquitous and are the major cause of chronic infections in humans and persistent biofouling in industry. Despite the significance of bacterial biofilms, the mechanism of biofilm formation and associated drug tolerance is still not fully understood. A major challenge in biofilm research is the intrinsic heterogeneity in the biofilm structure, which leads to temporal and spatial variation in cell density and gene expression. To understand and control such structural heterogeneity, surfaces with patterned functional alkanthiols were used in this study to obtain Escherichia coli cell clusters with systematically varied cluster size and distance between clusters. The results from quantitative imaging analysis revealed an interesting phenomenon in which multicellular connections can be formed between cell clusters depending on the size of interacting clusters and the distance between them. In addition, significant differences in patterned biofilm formation were observed between wild-type E. coli RP437 and some of its isogenic mutants, indicating that certain cellular and genetic factors are involved in interactions among cell clusters. In particular, autoinducer-2-mediated quorum sensing was found to be important. Collectively, these results provide missing information that links cell-to-cell signaling and interaction among cell clusters to the structural organization of bacterial biofilms.

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

DEFF Research Database (Denmark)

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

2015-01-01

of the outcome of phage-bacterial encounters in the fish pathogen Vibrio anguillarum is bacterial cell-cell communication, known as quorum sensing. Specifically, V. anguillarum PF430-3 cells locked in the low-cell-density state (ΔvanT mutant) express high levels of the phage receptor OmpK, resulting in a high...... susceptibility to phage KVP40, but achieve protection from infection by enhanced biofilm formation. By contrast, cells locked in the high-cell-density state (ΔvanΟ mutant) are almost completely unsusceptible due to quorum-sensing-mediated downregulation of OmpK expression. The phenotypes of the two quorum......-sensing mutant strains are accurately reflected in the behavior of wild-type V. anguillarum, which (i) displays increased OmpK expression in aggregated cells compared to free-living variants in the same culture, (ii) displays a clear inverse correlation between ompK mRNA levels and the concentration of N...

An update on Pseudomonas aeruginosa biofilm formation, tolerance, and dispersal

DEFF Research Database (Denmark)

Harmsen, Morten; Yang, Liang; Pamp, Sünje Johanna

2010-01-01

We review the recent advances in the understanding of the Pseudomonas aeruginosa biofilm lifestyle from studies using in vitro laboratory setups such as flow chambers and microtiter trays. Recent work sheds light on the role of nutrients, motility, and quorum sensing in structure formation in P....... aeruginosa biofilms. The second messenger, c-di-GMP, is established as an important regulator of the synthesis of polysaccharide and protein components of the biofilm matrix. Extracellular DNA is shown to be an essential component of the biofilm matrix. It has become apparent that biofilm formation involves...... interactions between different subpopulations. The molecular mechanisms underlying the tolerance of biofilm bacteria to antimicrobial agents are beginning to be unraveled, and new knowledge has been obtained regarding the environmental cues and regulatory mechanisms involved in biofilm dispersal....

Extracellular DNA Shields against Aminoglycosides in Pseudomonas aeruginosa Biofilms

DEFF Research Database (Denmark)

Chiang, Wen-Chi; Nilsson, Martin; Jensen, Peter Østrup

2013-01-01

Within recent years, it has been established that extracellular DNA is a key constituent of the matrix of microbial biofilms. In addition, it has recently been demonstrated that DNA binds positively charged antimicrobials such as aminoglycosides and antimicrobial peptides. In the present study, we...... provide evidence that extracellular DNA shields against aminoglycosides in Pseudomonas aeruginosa biofilms. We show that exogenously supplemented DNA integrates into P. aeruginosa biofilms and increases their tolerance toward aminoglycosides. We provide evidence that biofilms formed by a DNA release......-deficient P. aeruginosa quorum-sensing mutant are more susceptible to aminoglycoside treatment than wild-type biofilms but become rescued from the detrimental action of aminoglycosides upon supplementation with exogenous DNA. Furthermore, we demonstrate that exposure to lysed polymorphonuclear leukocytes...

Bacterial biofilm and associated infections

Directory of Open Access Journals (Sweden)

Muhsin Jamal

2018-01-01

Full Text Available Microscopic entities, microorganisms that drastically affect human health need to be thoroughly investigated. A biofilm is an architectural colony of microorganisms, within a matrix of extracellular polymeric substance that they produce. Biofilm contains microbial cells adherent to one-another and to a static surface (living or non-living. Bacterial biofilms are usually pathogenic in nature and can cause nosocomial infections. The National Institutes of Health (NIH revealed that among all microbial and chronic infections, 65% and 80%, respectively, are associated with biofilm formation. The process of biofilm formation consists of many steps, starting with attachment to a living or non-living surface that will lead to formation of micro-colony, giving rise to three-dimensional structures and ending up, after maturation, with detachment. During formation of biofilm several species of bacteria communicate with one another, employing quorum sensing. In general, bacterial biofilms show resistance against human immune system, as well as against antibiotics. Health related concerns speak loud due to the biofilm potential to cause diseases, utilizing both device-related and non-device-related infections. In summary, the understanding of bacterial biofilm is important to manage and/or to eradicate biofilm-related diseases. The current review is, therefore, an effort to encompass the current concepts in biofilm formation and its implications in human health and disease.

Screening of Natural Product Derivatives Identifies Two Structurally Related Flavonoids as Potent Quorum Sensing Inhibitors against Gram-Negative Bacteria

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Suvi Manner

2018-05-01

Full Text Available Owing to the failure of conventional antibiotics in biofilm control, alternative approaches are urgently needed. Inhibition of quorum sensing (QS represents an attractive target since it is involved in several processes essential for biofilm formation. In this study, a compound library of natural product derivatives (n = 3040 was screened for anti-quorum sensing activity using Chromobacterium violaceum as reporter bacteria. Screening assays, based on QS-mediated violacein production and viability, were performed in parallel to identify non-bactericidal QS inhibitors (QSIs. Nine highly active QSIs were identified, while 328 compounds were classified as moderately actives and 2062 compounds as inactives. Re-testing of the highly actives at a lower concentration against C. violaceum, complemented by a literature search, led to the identification of two flavonoid derivatives as the most potent QSIs, and their impact on biofilm maturation in Escherichia coli and Pseudomonas aeruginosa was further investigated. Finally, effects of these leads on swimming and swarming motility of P. aeruginosa were quantified. The identified flavonoids affected all the studied QS-related functions at micromolar concentrations. These compounds can serve as starting points for further optimization and development of more potent QSIs as adjunctive agents used with antibiotics in the treatment of biofilms.

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

Science.gov (United States)

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

2015-09-01

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

Reduced intracellular c-di-GMP content increases expression of quorum sensing-regulated genes in Pseudomonas aeruginosa

DEFF Research Database (Denmark)

Chua, Song Lin; Liu, Yang; Li, Yingying

2017-01-01

Cyclic-di-GMP (c-di-GMP) is an intracellular secondary messenger which controls the biofilm life cycle in many bacterial species. High intracellular c-di-GMP content enhances biofilm formation via the reduction of motility and production of biofilm matrix, while low c-di-GMP content in biofilm...... cells leads to increased motility and biofilm dispersal. While the effect of high c-di-GMP levels on bacterial lifestyles is well studied, the physiology of cells at low c-di-GMP levels remains unclear. Here, we showed that Pseudomonas aeruginosa cells with high and low intracellular c-di-GMP contents...... possessed distinct transcriptome profiles. There were 535 genes being upregulated and 432 genes downregulated in cells with low c-di-GMP, as compared to cells with high c-di-GMP. Interestingly, both rhl and pqs quorum-sensing (QS) operons were expressed at higher levels in cells with low intracellular c-di-GMP...

Baicalin inhibits biofilm formation, attenuates the quorum sensing-controlled virulence and enhances Pseudomonas aeruginosa clearance in a mouse peritoneal implant infection model.

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Jing Luo

Full Text Available The quorum sensing (QS circuit plays a role in the precise regulation of genes controlling virulence factors and biofilm formation in Pseudomonas aeruginosa. QS-controlled biofilm formation by Pseudomonas aeruginosa in clinical settings has remained controversial due to emerging drug resistance; therefore, screening diverse compounds for anti-biofilm or anti-QS activities is important. This study demonstrates the ability of sub-minimum inhibitory concentrations (sub-MICs of baicalin, an active natural compound extracted from the traditional Chinese medicinal Scutellaria baicalensis, to inhibit the formation of Pseudomonas aeruginosa biofilms and enhance the bactericidal effects of various conventional antibiotics in vitro. In addition, baicalin exerted dose-dependent inhibitory effects on virulence phenotypes (LasA protease, LasB elastase, pyocyanin, rhamnolipid, motilities and exotoxin A regulated by QS in Pseudomonas aeruginosa. Moreover, the expression levels of QS-regulatory genes, including lasI, lasR, rhlI, rhlR, pqsR and pqsA, were repressed after sub-MIC baicalin treatment, resulting in significant decreases in the QS signaling molecules 3-oxo-C12-HSL and C4-HSL, confirming the ability of baicalin-mediated QS inhibition to alter gene and protein expression. In vivo experiments indicated that baicalin treatment reduces Pseudomonas aeruginosa pathogenicity in Caenorhabditis elegans. Greater worm survival in the baicalin-treated group manifested as an increase in the LT50 from 24 to 96 h. In a mouse peritoneal implant infection model, baicalin treatment enhanced the clearance of Pseudomonas aeruginosa from the implants of mice infected with Pseudomonas aeruginosa compared with the control group. Moreover, the combination of baicalin and antibiotics significantly reduced the numbers of colony-forming units in the implants to a significantly greater degree than antibiotic treatment alone. Pathological and histological analyses revealed

Role of Streptococcus mutans surface proteins for biofilm formation

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Michiyo Matsumoto-Nakano

2018-02-01

Full Text Available Summary: Streptococcus mutans has been implicated as a primary causative agent of dental caries in humans. An important virulence property of the bacterium is its ability to form biofilm known as dental plaque on tooth surfaces. In addition, this organism also produces glucosyltransferases, multiple glucan-binding proteins, protein antigen c, and collagen-binding protein, surface proteins that coordinate to produce dental plaque, thus inducing dental caries. Bacteria utilize quorum-sensing systems to modulate environmental stress responses. A major mechanism of response to signals is represented by the so called two-component signal transduction system, which enables bacteria to regulate their gene expression and coordinate activities in response to environmental stress. As for S. mutans, a signal peptide-mediated quorum-sensing system encoded by comCDE has been found to be a regulatory system that responds to cell density and certain environmental stresses by excreting a peptide signal molecule termed CSP (competence-stimulating peptide. One of its principal virulence factors is production of bacteriocins (peptide antibiotics referred to as mutacins. Two-component signal transduction systems are commonly utilized by bacteria to regulate bacteriocin gene expression and are also related to biofilm formation by S. mutans. Keywords: Streptococcus mutans, Surface proteins, Biofilm, Signal transduction

Characterization of Acinetobacter baumannii biofilm associated components

Science.gov (United States)

Brossard, Kari A.

Acinetobacter baumannii is a Gram-negative aerobic coccobaccillus that is a major cause of nosocomial infections worldwide. Infected individuals may develop pneumonia, urinary tract, wound, and other infections that are associated with the use of indwelling medical devices such as catheters and mechanical ventilation. Treatment is difficult because many A. baumannii isolates have developed multi-drug resistance and the bacterium can persist on abiotic surfaces. Persistence and resistance may be due to formation of biofilms, which leads to long-term colonization, evasion of the host immune system and resistance to treatment with antibiotics and disinfectants. While biofilms are complex multifaceted structures, two bacterial components that have been shown to be important in formation and stability are exopolysaccharides (EPS) and the biofilm-associated protein (Bap). An EPS, poly-beta-1,6-N-acetylglucosamine, PNAG, has been described for E. coli and S. epidermidis. PNAG acts as an intercellular adhesin. Production of this adhesin is dependent on the pga/icaABCD locus. We have identified a homologous locus in A. baumannii 307-0294 that is involved in production of an exopolysaccharide, recognized by an anti-PNAG antibody. We hypothesized that the A. baumannii pgaABCD locus plays a role in biofilm formation, and protection against host innate defenses and disinfectants suggesting that PNAG is a possible virulence factor for the organism. The first aim of this thesis will define the pgaABCD locus. We have previously identified Bap, a protein with similarity to those described for S. aureus and we have demonstrated that this protein is involved in maintaining the stability of biofilms on glass. We hypothesized that A. baumannii Bap plays a role in persistence and pathogenesis and is regulated by quorum sensing. In our second aim we will examine the role of Bap in attachment and biofilm formation on medically relevant surfaces and also determine if Bap is involved in

Biofilms in Infections of the Eye

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Paulo J. M. Bispo

2015-03-01

Full Text Available The ability to form biofilms in a variety of environments is a common trait of bacteria, and may represent one of the earliest defenses against predation. Biofilms are multicellular communities usually held together by a polymeric matrix, ranging from capsular material to cell lysate. In a structure that imposes diffusion limits, environmental microgradients arise to which individual bacteria adapt their physiologies, resulting in the gamut of physiological diversity. Additionally, the proximity of cells within the biofilm creates the opportunity for coordinated behaviors through cell–cell communication using diffusible signals, the most well documented being quorum sensing. Biofilms form on abiotic or biotic surfaces, and because of that are associated with a large proportion of human infections. Biofilm formation imposes a limitation on the uses and design of ocular devices, such as intraocular lenses, posterior contact lenses, scleral buckles, conjunctival plugs, lacrimal intubation devices and orbital implants. In the absence of abiotic materials, biofilms have been observed on the capsule, and in the corneal stroma. As the evidence for the involvement of microbial biofilms in many ocular infections has become compelling, developing new strategies to prevent their formation or to eradicate them at the site of infection, has become a priority.

Inhibition of Serratia marcescens Smj-11 biofilm formation by Alcaligenes faecalis STN17 crude extract

International Nuclear Information System (INIS)

Lutfi, Zainal; Ahmad, Asmat; Usup, Gires

2014-01-01

Serratia marcescens biofilms are formed when they are bound to surfaces in aqueous environments. S. marcescens utilizes N-acylhomoserine lactone (AHL) as its quorum sensing signal molecule. The accumulation of AHL indicates the bacteria to produce matrices to form biofilms. Prodigiosin (2-methyl-3-pentyl-6-methoxyprodigiosin), which causes red pigmentation in the colonies, are also produced when the AHL reaches a certain threshold. The Alcaligenes faecalis STN17 crude extract is believed to inhibit quorum sensing in the S. marcescens Smj-11 and, thus, impedes its biofilm formation ability. A. faecalis STN17 was grown in marine broth, and ethyl acetate extraction was carried out. The crude compound of A. faecalis STN17 was diluted at high concentration (0.2-6.4 mg/mL) and was taken to confirm anti-biofilm activity through the crystal violet method in 96-wells plate. Then, the crude extract underwent purification using simple solvents partitioning test to discern the respective compounds that had the anti-biofilm activity under the crystal violet method. The crystal violet test showed that the crude did have anti-biofilm activity on S. marcescens Smj-11, but did not kill the cells. This finding signifies that the suppression of biofilm formation in S. marcescens by A. faecalis STN17 has a strong correlation. The partitioning test showed that A. faecalis STN17 crude extract has several compounds and only the compound(s) in chloroform showed activities. In conclusion, the crude extract of A. faecalis STN17 has the ability to inhibit S. marcescens Smj-11 biofilm formation

Inhibition of Serratia marcescens Smj-11 biofilm formation by Alcaligenes faecalis STN17 crude extract

Energy Technology Data Exchange (ETDEWEB)

Lutfi, Zainal; Ahmad, Asmat [School of Biosciences and Biotechnology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia (UKM), 43600 Bangi, Selangor (Malaysia); Usup, Gires [School of Environmental and Natural Resources Sciences, Faculty of Science and Technology, Universiti Kebangsaan Malaysia (UKM), 43600 Bangi, Selangor (Malaysia)

2014-09-03

Serratia marcescens biofilms are formed when they are bound to surfaces in aqueous environments. S. marcescens utilizes N-acylhomoserine lactone (AHL) as its quorum sensing signal molecule. The accumulation of AHL indicates the bacteria to produce matrices to form biofilms. Prodigiosin (2-methyl-3-pentyl-6-methoxyprodigiosin), which causes red pigmentation in the colonies, are also produced when the AHL reaches a certain threshold. The Alcaligenes faecalis STN17 crude extract is believed to inhibit quorum sensing in the S. marcescens Smj-11 and, thus, impedes its biofilm formation ability. A. faecalis STN17 was grown in marine broth, and ethyl acetate extraction was carried out. The crude compound of A. faecalis STN17 was diluted at high concentration (0.2-6.4 mg/mL) and was taken to confirm anti-biofilm activity through the crystal violet method in 96-wells plate. Then, the crude extract underwent purification using simple solvents partitioning test to discern the respective compounds that had the anti-biofilm activity under the crystal violet method. The crystal violet test showed that the crude did have anti-biofilm activity on S. marcescens Smj-11, but did not kill the cells. This finding signifies that the suppression of biofilm formation in S. marcescens by A. faecalis STN17 has a strong correlation. The partitioning test showed that A. faecalis STN17 crude extract has several compounds and only the compound(s) in chloroform showed activities. In conclusion, the crude extract of A. faecalis STN17 has the ability to inhibit S. marcescens Smj-11 biofilm formation.

Towards rational design of redox-stratified biofilms

DEFF Research Database (Denmark)

Lackner, Susanne

Biologisk kvælstoffjernelse er en central proces indenfor avanceret spildevandsrensning. Denne afhandling beskriver anvendelsen af beluftede membran biofilm reaktorer (eng: MABRs) til fuld autotrof kvælstoffjernelse. Denne ret nye kvælstofomsætningsvej baseres på delvis omdannelse af ammonium til....... Som illustreret ved modelundersøgelserne, kan biofilm afrivning påvirke rektorfunktionen alvorligt. Den udførte forsøg for at vurdere om kemisk modificering af biofilmoverfladen kan øge dens modstandsdygtighed overfor afrivning og give forbedret biofilm tykkelseskontrol. Alt i alt kan MABR, hvor ilt...

Prediction by promoter logic in bacterial quorum sensing.

Directory of Open Access Journals (Sweden)

Navneet Rai

2012-01-01

Full Text Available Quorum-sensing systems mediate chemical communication between bacterial cells, coordinating cell-density-dependent processes like biofilm formation and virulence-factor expression. In the proteobacterial LuxI/LuxR quorum sensing paradigm, a signaling molecule generated by an enzyme (LuxI diffuses between cells and allosterically stimulates a transcriptional regulator (LuxR to activate its cognate promoter (pR. By expressing either LuxI or LuxR in positive feedback from pR, these versatile systems can generate smooth (monostable or abrupt (bistable density-dependent responses to suit the ecological context. Here we combine theory and experiment to demonstrate that the promoter logic of pR - its measured activity as a function of LuxI and LuxR levels - contains all the biochemical information required to quantitatively predict the responses of such feedback loops. The interplay of promoter logic with feedback topology underlies the versatility of the LuxI/LuxR paradigm: LuxR and LuxI positive-feedback systems show dramatically different responses, while a dual positive/negative-feedback system displays synchronized oscillations. These results highlight the dual utility of promoter logic: to probe microscopic parameters and predict macroscopic phenotype.

Involvement of Shewanella oneidensis MR-1 LuxS in Biofilm Development and Sulfur Metabolism

Energy Technology Data Exchange (ETDEWEB)

Learman, Deric R.; Yi, Haakrho; Brown, Steven D.; Martin, Stanton L.; Geesey, Gill G.; Stevens, Ann M.; Hochella, Michael F.

2009-01-05

The role of LuxS in Shewanella oneidensis MR-1 has been examined by transcriptomic profiling, biochemical, and physiological experiments. The results indicate that a mutation in luxS alters biofilm development, not by altering quorum-sensing abilities but by disrupting the activated methyl cycle (AMC). The S. oneidensis wild type can produce a luminescence response in the AI-2 reporter strain Vibrio harveyi MM32. This luminescence response is abolished upon the deletion of luxS. The deletion of luxS also alters biofilm formations in static and flowthrough conditions. Genetic complementation restores the mutant biofilm defect, but the addition of synthetic AI-2 has no effect. These results suggest that AI-2 is not used as a quorum-sensing signal to regulate biofilm development in S. oneidensis. Growth on various sulfur sources was examined because of the involvement of LuxS in the AMC. A mutation in luxS produced a reduced ability to grow with methionine as the sole sulfur source. Methionine is a key metabolite used in the AMC to produce a methyl source in the cell and to recycle homocysteine. These data suggest that LuxS is important to metabolizing methionine and the AMC in S. oneidensis.

Mitigation of membrane biofouling by a quorum quenching bacterium for membrane bioreactors.

Science.gov (United States)

Ham, So-Young; Kim, Han-Shin; Cha, Eunji; Park, Jeong-Hoon; Park, Hee-Deung

2018-06-01

In this study, a quorum-quenching (QQ) bacterium named HEMM-1 was isolated at a membrane bioreactor (MBR) plant. HEMM-1 has diplococcal morphology and 99% sequence identity to Enterococcus species. The HEMM-1 cell-free supernatant (CFS) showed higher QQ activities than the CFS of other QQ bacteria, mostly by degrading N-acyl homoserine lactones (AHLs) with short acyl chains. Instrumental analyses revealed that HEMM-1 CFS degraded AHLs via lactonase activity. Under static, flow, and shear conditions, the HEMM-1 CFS was effective in reducing bacterial and activated-sludge biofilms formed on membrane surfaces. In conclusion, the HEMM-1 isolate is a QQ bacterium applicable to the control of biofouling in MBRs via inhibition of biofilm formation on membrane surfaces. Copyright © 2018 Elsevier Ltd. All rights reserved.

The Effect of Novel Heterocyclic Compounds on Cryptococcal Biofilm

Science.gov (United States)

Korem, Maya; Kagan, Sarah

2017-01-01

Biofilm formation by microorganisms depends on their communication by quorum sensing, which is mediated by small diffusible signaling molecules that accumulate in the extracellular environment. During human infection, the pathogenic yeast Cryptococcus neoformans can form biofilm on medical devices, which protects the organism and increases its resistance to antifungal agents. The aim of this study was to test two novel heterocyclic compounds, S-8 (thiazolidinedione derivative, TZD) and NA-8 (succinimide derivative, SI), for their anti-biofilm activity against strains of Cryptococcus neoformans and Cryptococcus gattii. Biofilms were formed in a defined medium in 96-well polystyrene plates and 8-well micro-slides. The effect of sub-inhibitory concentrations of S-8 and NA-8 on biofilm formation was measured after 48 h by a metabolic reduction assay and by confocal laser microscopy analysis using fluorescent staining. The formation and development of cryptococcal biofilms was inhibited significantly by these compounds in concentrations below the minimum inhibitory concentration (MIC) values. These compounds may have a potential role in preventing fungal biofilm development on indwelling medical devices or even as a therapeutic measure after the establishment of biofilm. PMID:29371559

New weapons to fight old enemies: novel strategies for the (biocontrol of bacterial biofilms in the food industry

Directory of Open Access Journals (Sweden)

Laura Maria Coughlan

2016-10-01

Full Text Available Biofilms are microbial communities characterized by their adhesion to solid surfaces and the production of a matrix of exopolymeric substances (EPS, consisting of polysaccharides, proteins, DNA and lipids, which surround the microorganisms lending structural integrity and a unique biochemical profile to the biofilm. Biofilm formation enhances the ability of the producer/s to persist in a given environment. Pathogenic and spoilage bacterial species capable of forming biofilms are a significant problem for the healthcare and food industries, as their biofilm-forming ability protects them from common cleaning processes and allows them to remain in the environment post-sanitation. In the food industry, persistent bacteria colonize the inside of mixing tanks, vats and tubing, compromising food safety and quality. Strategies to overcome bacterial persistence through inhibition of biofilm formation or removal of mature biofilms are therefore necessary. Current biofilm control strategies employed in the food industry (cleaning and disinfection, material selection and surface preconditioning, plasma treatment, ultrasonication, etc., although effective to a certain point, fall short of biofilm control. Efforts have been explored, mainly with a view to their application in pharmaceutical and healthcare settings, which focus on targeting molecular determinants regulating biofilm formation. Their application to the food industry would greatly aid efforts to eradicate undesirable bacteria from food processing environments and, ultimately, from food products. These approaches, in contrast to bactericidal approaches, exert less selective pressure which in turn would reduce the likelihood of resistance development. A particularly interesting strategy targets quorum sensing systems, which regulate gene expression in response to fluctuations in cell-population density governing essential cellular processes including biofilm formation. This review article discusses

Identification of Pathways Critical to Quorum Sensing and Virulence Induction

Energy Technology Data Exchange (ETDEWEB)

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

2009-02-27

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

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

DEFF Research Database (Denmark)

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...

New Weapons to Fight Old Enemies: Novel Strategies for the (Bio)control of Bacterial Biofilms in the Food Industry.

Science.gov (United States)

Coughlan, Laura M; Cotter, Paul D; Hill, Colin; Alvarez-Ordóñez, Avelino

2016-01-01

Biofilms are microbial communities characterized by their adhesion to solid surfaces and the production of a matrix of exopolymeric substances, consisting of polysaccharides, proteins, DNA and lipids, which surround the microorganisms lending structural integrity and a unique biochemical profile to the biofilm. Biofilm formation enhances the ability of the producer/s to persist in a given environment. Pathogenic and spoilage bacterial species capable of forming biofilms are a significant problem for the healthcare and food industries, as their biofilm-forming ability protects them from common cleaning processes and allows them to remain in the environment post-sanitation. In the food industry, persistent bacteria colonize the inside of mixing tanks, vats and tubing, compromising food safety and quality. Strategies to overcome bacterial persistence through inhibition of biofilm formation or removal of mature biofilms are therefore necessary. Current biofilm control strategies employed in the food industry (cleaning and disinfection, material selection and surface preconditioning, plasma treatment, ultrasonication, etc.), although effective to a certain point, fall short of biofilm control. Efforts have been explored, mainly with a view to their application in pharmaceutical and healthcare settings, which focus on targeting molecular determinants regulating biofilm formation. Their application to the food industry would greatly aid efforts to eradicate undesirable bacteria from food processing environments and, ultimately, from food products. These approaches, in contrast to bactericidal approaches, exert less selective pressure which in turn would reduce the likelihood of resistance development. A particularly interesting strategy targets quorum sensing systems, which regulate gene expression in response to fluctuations in cell-population density governing essential cellular processes including biofilm formation. This review article discusses the problems associated

Proteomics of the bacterial cross-talk by quorum sensing.

Science.gov (United States)

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

2011-01-01

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

Cross-feeding and interkingdom communication in dual-species biofilms of Streptococcus mutans and Candida albicans

Science.gov (United States)

Sztajer, Helena; Szafranski, Szymon P; Tomasch, Jürgen; Reck, Michael; Nimtz, Manfred; Rohde, Manfred; Wagner-Döbler, Irene

2014-01-01

Polymicrobial biofilms are of large medical importance, but relatively little is known about the role of interspecies interactions for their physiology and virulence. Here, we studied two human pathogens co-occuring in the oral cavity, the opportunistic fungus Candida albicans and the caries-promoting bacterium Streptococcus mutans. Dual-species biofilms reached higher biomass and cell numbers than mono-species biofilms, and the production of extracellular polymeric substances (EPSs) by S. mutans was strongly suppressed, which was confirmed by scanning electron microscopy, gas chromatography–mass spectrometry and transcriptome analysis. To detect interkingdom communication, C. albicans was co-cultivated with a strain of S. mutans carrying a transcriptional fusion between a green fluorescent protein-encoding gene and the promoter for sigX, the alternative sigma factor of S. mutans, which is induced by quorum sensing signals. Strong induction of sigX was observed in dual-species biofilms, but not in single-species biofilms. Conditioned media from mixed biofilms but not from C. albicans or S. mutans cultivated alone activated sigX in the reporter strain. Deletion of comS encoding the synthesis of the sigX-inducing peptide precursor abolished this activity, whereas deletion of comC encoding the competence-stimulating peptide precursor had no effect. Transcriptome analysis of S. mutans confirmed induction of comS, sigX, bacteriocins and the downstream late competence genes, including fratricins, in dual-species biofilms. We show here for the first time the stimulation of the complete quorum sensing system of S. mutans by a species from another kingdom, namely the fungus C. albicans, resulting in fundamentally changed virulence properties of the caries pathogen. PMID:24824668

Evaluation of the Enterococcus faecalis Biofilm-Associated Virulence Factors AhrC and Eep in Rat Foreign Body Osteomyelitis and In Vitro Biofilm-Associated Antimicrobial Resistance.

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Kristi L Frank

Full Text Available Enterococcus faecalis can cause healthcare-associated biofilm infections, including those of orthopedic devices. Treatment of enterococcal prosthetic joint infection is difficult, in part, due to biofilm-associated antimicrobial resistance. We previously showed that the E. faecalis OG1RF genes ahrC and eep are in vitro biofilm determinants and virulence factors in animal models of endocarditis and catheter-associated urinary tract infection. In this study, we evaluated the role of these genes in a rat acute foreign body osteomyelitis model and in in vitro biofilm-associated antimicrobial resistance. Osteomyelitis was established for one week following the implantation of stainless steel orthopedic wires inoculated with E. faecalis strains OG1RF, ΩahrC, and ∆eep into the proximal tibiae of rats. The median bacterial loads recovered from bones and wires did not differ significantly between the strains at multiple inoculum concentrations. We hypothesize that factors present at the infection site that affect biofilm formation, such as the presence or absence of shear force, may account for the differences in attenuation in the various animal models we have used to study the ΩahrC and ∆eep strains. No differences among the three strains were observed in the planktonic and biofilm antimicrobial susceptibilities to ampicillin, vancomycin, daptomycin, linezolid, and tetracycline. These findings suggest that neither ahrC nor eep directly contribute to E. faecalis biofilm-associated antimicrobial resistance. Notably, the experimental evidence that the biofilm attachment mutant ΩahrC displays biofilm-associated antimicrobial resistance suggests that surface colonization alone is sufficient for E. faecalis cells to acquire the biofilm antimicrobial resistance phenotype.

Piper betle and its bioactive metabolite phytol mitigates quorum sensing mediated virulence factors and biofilm of nosocomial pathogen Serratia marcescens in vitro.

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Srinivasan, Ramanathan; Devi, Kannan Rama; Kannappan, Arunachalam; Pandian, Shunmugiah Karutha; Ravi, Arumugam Veera

2016-12-04

Piper betle, a tropical creeper plant belongs to the family Piperaceae. The leaves of this plant have been well known for their therapeutic, religious and ceremonial value in South and Southeast Asia. It has also been reported to possess several biological activities including antimicrobial, antioxidant, antinociceptive, antidiabetic, insecticidal and gastroprotective activities and used as a common ingredient in indigenous medicines. In Indian system of ayurvedic medicine, P. betle has been well recognized for its antiseptic properties and is commonly applied on wounds and lesions for its healing effects. To evaluate the anti-quorum sensing (anti-QS) and antibiofilm efficacy of P. betle and its bioactive metabolite phytol against Serratia marcescens. The P. betle ethyl acetate extract (PBE) was evaluated for its anti-QS efficacy against S. marcescens by assessing the prodigiosin and lipase production at 400 and 500µgml -1 concentrations. In addition, the biofilm biomass quantification assay was performed to evaluate the antibiofilm activity of PBE against S. marcescens. Besides, the influence of PBE on bacterial biofilm formation was assessed through microscopic techniques. The biofilm related phenomenons like exopolysaccharides (EPS) production, hydrophobicity and swarming motility were also examined to support the antibiofilm activity of PBE. Transcriptional analysis of QS regulated genes in S. marcescens was also done. Characterization of PBE was done by separation through column chromatography and identification of active metabolites by gas chromatography -mass spectrometry. The major compounds of active fractions such as hexadecanoic acid, eugenol and phytol were assessed for their anti-QS activity against S. marcescens. Further, the in vitro bioassays such as protease, biofilm and HI quantification were also carried out to confirm the anti-QS and antibiofilm potential of phytol in PBE. PBE inhibits QS mediated prodigiosin pigment production in S. marcescens

Bacterial Biofilm Control by Perturbation of Bacterial Signaling Processes

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Tim Holm Jakobsen

2017-09-01

Full Text Available The development of effective strategies to combat biofilm infections by means of either mechanical or chemical approaches could dramatically change today’s treatment procedures for the benefit of thousands of patients. Remarkably, considering the increased focus on biofilms in general, there has still not been invented and/or developed any simple, efficient and reliable methods with which to “chemically” eradicate biofilm infections. This underlines the resilience of infective agents present as biofilms and it further emphasizes the insufficiency of today’s approaches used to combat chronic infections. A potential method for biofilm dismantling is chemical interception of regulatory processes that are specifically involved in the biofilm mode of life. In particular, bacterial cell to cell signaling called “Quorum Sensing” together with intracellular signaling by bis-(3′-5′-cyclic-dimeric guanosine monophosphate (cyclic-di-GMP have gained a lot of attention over the last two decades. More recently, regulatory processes governed by two component regulatory systems and small non-coding RNAs have been increasingly investigated. Here, we review novel findings and potentials of using small molecules to target and modulate these regulatory processes in the bacterium Pseudomonas aeruginosa to decrease its pathogenic potential.

Bacillus subtilis biofilm extends Caenorhabditis elegans longevity through downregulation of the insulin-like signalling pathway

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Donato, Verónica; Ayala, Facundo Rodríguez; Cogliati, Sebastián; Bauman, Carlos; Costa, Juan Gabriel; Leñini, Cecilia; Grau, Roberto

2017-01-01

Beneficial bacteria have been shown to affect host longevity, but the molecular mechanisms mediating such effects remain largely unclear. Here we show that formation of Bacillus subtilis biofilms increases Caenorhabditis elegans lifespan. Biofilm-proficient B. subtilis colonizes the C. elegans gut and extends worm lifespan more than biofilm-deficient isogenic strains. Two molecules produced by B. subtilis — the quorum-sensing pentapeptide CSF and nitric oxide (NO) — are sufficient to extend C. elegans longevity. When B. subtilis is cultured under biofilm-supporting conditions, the synthesis of NO and CSF is increased in comparison with their production under planktonic growth conditions. We further show that the prolongevity effect of B. subtilis biofilms depends on the DAF-2/DAF-16/HSF-1 signalling axis and the downregulation of the insulin-like signalling (ILS) pathway. PMID:28134244

Effect of alcohols on filamentation, growth, viability and biofilm development in Candida albicans.

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Chauhan, Nitin M; Shinde, Ravikumar B; Karuppayil, S Mohan

2013-12-01

In this study we report the potential of alcohols as morphogenetic regulators in Candida albicans. All the alcohols tested influenced various modes of growth like planktonic as well as biofilm forms. Viability was affected at high concentrations. Among the alcohols, the response of C. albicans to amyl alcohol (pentanol) was noteworthy. Amyl alcohol at a concentration 0.5% which was not inhibitory to growth and viability specifically inhibited morphogenetic switching from yeast to hyphal forms. It also inhibited normal biofilm development favoring yeast dominated biofilms. Based on this study we hypothesize that alcohols produced under anaerobic conditions may not favor biofilm development and support dissemination of yeast cells. Since anaerobic conditions are not found to favor production of quorum sensing molecules like farnesol, the alcohols may play a role in morphogenetic regulation.

Whole transcriptome analysis of Acinetobacter baumannii assessed by RNA-sequencing reveals different mRNA expression profiles in biofilm compared to planktonic cells.

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Soraya Rumbo-Feal

Full Text Available Acinetobacterbaumannii has emerged as a dangerous opportunistic pathogen, with many strains able to form biofilms and thus cause persistent infections. The aim of the present study was to use high-throughput sequencing techniques to establish complete transcriptome profiles of planktonic (free-living and sessile (biofilm forms of A. baumannii ATCC 17978 and thereby identify differences in their gene expression patterns. Collections of mRNA from planktonic (both exponential and stationary phase cultures and sessile (biofilm cells were sequenced. Six mRNA libraries were prepared following the mRNA-Seq protocols from Illumina. Reads were obtained in a HiScanSQ platform and mapped against the complete genome to describe the complete mRNA transcriptomes of planktonic and sessile cells. The results showed that the gene expression pattern of A. baumannii biofilm cells was distinct from that of planktonic cells, including 1621 genes over-expressed in biofilms relative to stationary phase cells and 55 genes expressed only in biofilms. These differences suggested important changes in amino acid and fatty acid metabolism, motility, active transport, DNA-methylation, iron acquisition, transcriptional regulation, and quorum sensing, among other processes. Disruption or deletion of five of these genes caused a significant decrease in biofilm formation ability in the corresponding mutant strains. Among the genes over-expressed in biofilm cells were those in an operon involved in quorum sensing. One of them, encoding an acyl carrier protein, was shown to be involved in biofilm formation as demonstrated by the significant decrease in biofilm formation by the corresponding knockout strain. The present work serves as a basis for future studies examining the complex network systems that regulate bacterial biofilm formation and maintenance.

Strategies for combating bacterial biofilms: A focus on anti-biofilm agents and their mechanisms of action

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Roy, Ranita; Tiwari, Monalisa; Donelli, Gianfranco; Tiwari, Vishvanath

2018-01-01

ABSTRACT Biofilm refers to the complex, sessile communities of microbes found either attached to a surface or buried firmly in an extracellular matrix as aggregates. The biofilm matrix surrounding bacteria makes them tolerant to harsh conditions and resistant to antibacterial treatments. Moreover, the biofilms are responsible for causing a broad range of chronic diseases and due to the emergence of antibiotic resistance in bacteria it has really become difficult to treat them with efficacy. Furthermore, the antibiotics available till date are ineffective for treating these biofilm related infections due to their higher values of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC), which may result in in-vivo toxicity. Hence, it is critically important to design or screen anti-biofilm molecules that can effectively minimize and eradicate biofilm related infections. In the present article, we have highlighted the mechanism of biofilm formation with reference to different models and various methods used for biofilm detection. A major focus has been put on various anti-biofilm molecules discovered or tested till date which may include herbal active compounds, chelating agents, peptide antibiotics, lantibiotics and synthetic chemical compounds along with their structures, mechanism of action and their respective MICs, MBCs, minimum biofilm inhibitory concentrations (MBICs) as well as the half maximal inhibitory concentration (IC50) values available in the literature so far. Different mode of action of anti biofilm molecules addressed here are inhibition via interference in the quorum sensing pathways, adhesion mechanism, disruption of extracellular DNA, protein, lipopolysaccharides, exopolysaccharides and secondary messengers involved in various signaling pathways. From this study, we conclude that the molecules considered here might be used to treat biofilm-associated infections after significant structural modifications, thereby

Selective labelling and eradication of antibiotic-tolerant bacterial populations in Pseudomonas aeruginosa biofilms

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Chua, Song Lin; Yam, Joey Kuok Hoong; Hao, Piliang; Adav, Sunil S.; Salido, May Margarette; Liu, Yang; Givskov, Michael; Sze, Siu Kwan; Tolker-Nielsen, Tim; Yang, Liang

2016-01-01

Drug resistance and tolerance greatly diminish the therapeutic potential of antibiotics against pathogens. Antibiotic tolerance by bacterial biofilms often leads to persistent infections, but its mechanisms are unclear. Here we use a proteomics approach, pulsed stable isotope labelling with amino acids (pulsed-SILAC), to quantify newly expressed proteins in colistin-tolerant subpopulations of Pseudomonas aeruginosa biofilms (colistin is a ‘last-resort' antibiotic against multidrug-resistant Gram-negative pathogens). Migration is essential for the formation of colistin-tolerant biofilm subpopulations, with colistin-tolerant cells using type IV pili to migrate onto the top of the colistin-killed biofilm. The colistin-tolerant cells employ quorum sensing (QS) to initiate the formation of new colistin-tolerant subpopulations, highlighting multicellular behaviour in antibiotic tolerance development. The macrolide erythromycin, which has been previously shown to inhibit the motility and QS of P. aeruginosa, boosts biofilm eradication by colistin. Our work provides insights on the mechanisms underlying the formation of antibiotic-tolerant populations in bacterial biofilms and indicates research avenues for designing more efficient treatments against biofilm-associated infections. PMID:26892159

Selective labelling and eradication of antibiotic-tolerant bacterial populations in Pseudomonas aeruginosa biofilms.

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Chua, Song Lin; Yam, Joey Kuok Hoong; Hao, Piliang; Adav, Sunil S; Salido, May Margarette; Liu, Yang; Givskov, Michael; Sze, Siu Kwan; Tolker-Nielsen, Tim; Yang, Liang

2016-02-19

Drug resistance and tolerance greatly diminish the therapeutic potential of antibiotics against pathogens. Antibiotic tolerance by bacterial biofilms often leads to persistent infections, but its mechanisms are unclear. Here we use a proteomics approach, pulsed stable isotope labelling with amino acids (pulsed-SILAC), to quantify newly expressed proteins in colistin-tolerant subpopulations of Pseudomonas aeruginosa biofilms (colistin is a 'last-resort' antibiotic against multidrug-resistant Gram-negative pathogens). Migration is essential for the formation of colistin-tolerant biofilm subpopulations, with colistin-tolerant cells using type IV pili to migrate onto the top of the colistin-killed biofilm. The colistin-tolerant cells employ quorum sensing (QS) to initiate the formation of new colistin-tolerant subpopulations, highlighting multicellular behaviour in antibiotic tolerance development. The macrolide erythromycin, which has been previously shown to inhibit the motility and QS of P. aeruginosa, boosts biofilm eradication by colistin. Our work provides insights on the mechanisms underlying the formation of antibiotic-tolerant populations in bacterial biofilms and indicates research avenues for designing more efficient treatments against biofilm-associated infections.

In vitro and in vivo effect of 2,6-Di-tert-butyl-4-methylphenol as an antibiofilm agent against quorum sensing mediated biofilm formation of Vibrio spp.

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Santhakumari, Sivasubramanian; Jayakumar, Rengarajan; Logalakshmi, Ravichandran; Prabhu, Narayanan Marimuthu; Abdul Nazar, Abdul Kuthus; Karutha Pandian, Shunmugiah; Veera Ravi, Arumugam

2018-05-25

This study unveils the in vitro and in vivo antibiofilm potential of 2,6-Di-tert-butyl-4-methylphenol (DTBMP) from Chroococcus turgidus against Vibrio spp. In the preliminary study, cell free culture supernatant (CFCS) of C. turgidus inhibited the violacein production in biomarker strain Chromobacterium violaceum and its mutant strain CV026 in a dose dependent manner. The effective biofilm inhibitory concentration (BIC) of pure compound DTBMP from C. turgidus was identified as 250 μg/ml concentration in tested Vibrio species. Furthermore, DTBMP proved to effectively inhibit the bioluminescence production in V. harveyi and other biofilm related virulence traits such as exopolysaccharides (EPS) production, hydrophobicity index, swimming and swarming motility at its BIC concentration in three major pathogenic vibrios: V. harveyi, V. parahaemolyticus and V. vulnificus. The antibiofilm potential of DTBMP was validated through light, confocal laser scanning and scanning electron microscopic analyses. In addition, the non-bactericidal effect of DTBMP was determined through growth curve and 2,3-bis (2-methyloxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) assay. Real-time PCR studies revealed the down-regulation of master quorum sensing (QS) regulator genes of V. harveyi such as luxR, luxS, luxP, luxQ and luxO on treatment with DTBMP. In vivo results confirmed that DTBMP augmented the survival rate of Litopenaeus vannamei larvae up to 75, 88 and 66% upon infection with V. harveyi, V. parahaemolyticus and V. vulnificus, respectively. The results of this study ascertain the promising effects of DTBMP as an antibiofilm agent, which could be positively explored to treat biofilm-associated vibrios infections in aquaculture. Copyright © 2018 Elsevier B.V. All rights reserved.

Nutrient transitions are a source of persisters in Escherichia coli biofilms.

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Stephanie M Amato

Full Text Available Chronic and recurrent infections have been attributed to persisters in biofilms, and despite this importance, the mechanisms of persister formation in biofilms remain unclear. The plethora of biofilm characteristics that could give rise to persisters, including slower growth, quorum signaling, oxidative stress, and nutrient heterogeneity, have complicated efforts to delineate formation pathways that generate persisters during biofilm development. Here we sought to specifically determine whether nutrient transitions, which are a common metabolic stress encountered within surface-attached communities, stimulate persister formation in biofilms and if so, to then identify the pathway. To accomplish this, we established an experimental methodology where nutrient availability to biofilm cells could be controlled exogenously, and then used that method to discover that diauxic carbon source transitions stimulated persister formation in Escherichia coli biofilms. Previously, we found that carbon source transitions stimulate persister formation in planktonic E. coli cultures, through a pathway that involved ppGpp and nucleoid-associated proteins, and therefore, tested the functionality of that pathway in biofilms. Biofilm persister formation was also found to be dependent on ppGpp and nucleoid-associated proteins, but the importance of specific proteins and enzymes between biofilm and planktonic lifestyles was significantly different. Data presented here support the increasingly appreciated role of ppGpp as a central mediator of bacterial persistence and demonstrate that nutrient transitions can be a source of persisters in biofilms.

Nutrient transitions are a source of persisters in Escherichia coli biofilms.

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Amato, Stephanie M; Brynildsen, Mark P

2014-01-01

Chronic and recurrent infections have been attributed to persisters in biofilms, and despite this importance, the mechanisms of persister formation in biofilms remain unclear. The plethora of biofilm characteristics that could give rise to persisters, including slower growth, quorum signaling, oxidative stress, and nutrient heterogeneity, have complicated efforts to delineate formation pathways that generate persisters during biofilm development. Here we sought to specifically determine whether nutrient transitions, which are a common metabolic stress encountered within surface-attached communities, stimulate persister formation in biofilms and if so, to then identify the pathway. To accomplish this, we established an experimental methodology where nutrient availability to biofilm cells could be controlled exogenously, and then used that method to discover that diauxic carbon source transitions stimulated persister formation in Escherichia coli biofilms. Previously, we found that carbon source transitions stimulate persister formation in planktonic E. coli cultures, through a pathway that involved ppGpp and nucleoid-associated proteins, and therefore, tested the functionality of that pathway in biofilms. Biofilm persister formation was also found to be dependent on ppGpp and nucleoid-associated proteins, but the importance of specific proteins and enzymes between biofilm and planktonic lifestyles was significantly different. Data presented here support the increasingly appreciated role of ppGpp as a central mediator of bacterial persistence and demonstrate that nutrient transitions can be a source of persisters in biofilms.

Regulatory and Metabolic Networks for the Adaptation of Pseudomonas aeruginosa Biofilms to Urinary Tract-Like Conditions

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Dohnt, Katrin; Haddad, Isam; Jänsch, Lothar; Klein, Johannes; Narten, Maike; Pommerenke, Claudia; Scheer, Maurice; Schobert, Max; Schomburg, Dietmar; Thielen, Bernhard; Jahn, Dieter

2013-01-01

Biofilms of the Gram-negative bacterium Pseudomonas aeruginosa are one of the major causes of complicated urinary tract infections with detrimental outcome. To develop novel therapeutic strategies the molecular adaption strategies of P. aeruginosa biofilms to the conditions of the urinary tract were investigated thoroughly at the systems level using transcriptome, proteome, metabolome and enzyme activity analyses. For this purpose biofilms were grown anaerobically in artificial urine medium (AUM). Obtained data were integrated bioinformatically into gene regulatory and metabolic networks. The dominating response at the transcriptome and proteome level was the adaptation to iron limitation via the broad Fur regulon including 19 sigma factors and up to 80 regulated target genes or operons. In agreement, reduction of the iron cofactor-dependent nitrate respiratory metabolism was detected. An adaptation of the central metabolism to lactate, citrate and amino acid as carbon sources with the induction of the glyoxylate bypass was observed, while other components of AUM like urea and creatinine were not used. Amino acid utilization pathways were found induced, while fatty acid biosynthesis was reduced. The high amounts of phosphate found in AUM explain the reduction of phosphate assimilation systems. Increased quorum sensing activity with the parallel reduction of chemotaxis and flagellum assembly underscored the importance of the biofilm life style. However, reduced formation of the extracellular polysaccharide alginate, typical for P. aeruginosa biofilms in lungs, indicated a different biofilm type for urinary tract infections. Furthermore, the obtained quorum sensing response results in an increased production of virulence factors like the extracellular lipase LipA and protease LasB and AprA explaining the harmful cause of these infections. PMID:23967252

Regulatory and metabolic networks for the adaptation of Pseudomonas aeruginosa biofilms to urinary tract-like conditions.

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Petra Tielen

Full Text Available Biofilms of the Gram-negative bacterium Pseudomonas aeruginosa are one of the major causes of complicated urinary tract infections with detrimental outcome. To develop novel therapeutic strategies the molecular adaption strategies of P. aeruginosa biofilms to the conditions of the urinary tract were investigated thoroughly at the systems level using transcriptome, proteome, metabolome and enzyme activity analyses. For this purpose biofilms were grown anaerobically in artificial urine medium (AUM. Obtained data were integrated bioinformatically into gene regulatory and metabolic networks. The dominating response at the transcriptome and proteome level was the adaptation to iron limitation via the broad Fur regulon including 19 sigma factors and up to 80 regulated target genes or operons. In agreement, reduction of the iron cofactor-dependent nitrate respiratory metabolism was detected. An adaptation of the central metabolism to lactate, citrate and amino acid as carbon sources with the induction of the glyoxylate bypass was observed, while other components of AUM like urea and creatinine were not used. Amino acid utilization pathways were found induced, while fatty acid biosynthesis was reduced. The high amounts of phosphate found in AUM explain the reduction of phosphate assimilation systems. Increased quorum sensing activity with the parallel reduction of chemotaxis and flagellum assembly underscored the importance of the biofilm life style. However, reduced formation of the extracellular polysaccharide alginate, typical for P. aeruginosa biofilms in lungs, indicated a different biofilm type for urinary tract infections. Furthermore, the obtained quorum sensing response results in an increased production of virulence factors like the extracellular lipase LipA and protease LasB and AprA explaining the harmful cause of these infections.

Regulatory and metabolic networks for the adaptation of Pseudomonas aeruginosa biofilms to urinary tract-like conditions.

Science.gov (United States)

Tielen, Petra; Rosin, Nathalie; Meyer, Ann-Kathrin; Dohnt, Katrin; Haddad, Isam; Jänsch, Lothar; Klein, Johannes; Narten, Maike; Pommerenke, Claudia; Scheer, Maurice; Schobert, Max; Schomburg, Dietmar; Thielen, Bernhard; Jahn, Dieter

2013-01-01

Biofilms of the Gram-negative bacterium Pseudomonas aeruginosa are one of the major causes of complicated urinary tract infections with detrimental outcome. To develop novel therapeutic strategies the molecular adaption strategies of P. aeruginosa biofilms to the conditions of the urinary tract were investigated thoroughly at the systems level using transcriptome, proteome, metabolome and enzyme activity analyses. For this purpose biofilms were grown anaerobically in artificial urine medium (AUM). Obtained data were integrated bioinformatically into gene regulatory and metabolic networks. The dominating response at the transcriptome and proteome level was the adaptation to iron limitation via the broad Fur regulon including 19 sigma factors and up to 80 regulated target genes or operons. In agreement, reduction of the iron cofactor-dependent nitrate respiratory metabolism was detected. An adaptation of the central metabolism to lactate, citrate and amino acid as carbon sources with the induction of the glyoxylate bypass was observed, while other components of AUM like urea and creatinine were not used. Amino acid utilization pathways were found induced, while fatty acid biosynthesis was reduced. The high amounts of phosphate found in AUM explain the reduction of phosphate assimilation systems. Increased quorum sensing activity with the parallel reduction of chemotaxis and flagellum assembly underscored the importance of the biofilm life style. However, reduced formation of the extracellular polysaccharide alginate, typical for P. aeruginosa biofilms in lungs, indicated a different biofilm type for urinary tract infections. Furthermore, the obtained quorum sensing response results in an increased production of virulence factors like the extracellular lipase LipA and protease LasB and AprA explaining the harmful cause of these infections.

Atomic force microscopy reveals a morphological differentiation of chromobacterium violaceum cells associated with biofilm development and directed by N-hexanoyl-L-homoserine lactone.

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Anara A Kamaeva

Full Text Available Chromobacterium violaceum abounds in soil and water ecosystems in tropical and subtropical regions and occasionally causes severe and often fatal human and animal infections. The quorum sensing (QS system and biofilm formation are essential for C. violaceum's adaptability and pathogenicity, however, their interrelation is still unknown. C. violaceum's cell and biofilm morphology were examined by atomic force microscopy (AFM in comparison with growth rates, QS-dependent violacein biosynthesis and biofilm biomass quantification. To evaluate QS regulation of these processes, the wild-type strain C. violaceum ATCC 31532 and its mini-Tn5 mutant C. violaceum NCTC 13274, cultivated with and without the QS autoinducer N-hexanoyl-L-homoserine lactone (C6-HSL, were used. We report for the first time the unusual morphological differentiation of C. violaceum cells, associated with biofilm development and directed by the QS autoinducer. AFM revealed numerous invaginations of the external cytoplasmic membrane of wild-type cells, which were repressed in the mutant strain and restored by exogenous C6-HSL. With increasing bacterial growth, polymer matrix extrusions formed in place of invaginations, whereas mutant cells were covered with a diffusely distributed extracellular substance. Thus, quorum sensing in C. violaceum involves a morphological differentiation that organises biofilm formation and leads to a highly differentiated matrix structure.

Atomic force microscopy reveals a morphological differentiation of chromobacterium violaceum cells associated with biofilm development and directed by N-hexanoyl-L-homoserine lactone.

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Kamaeva, Anara A; Vasilchenko, Alexey S; Deryabin, Dmitry G

2014-01-01

Chromobacterium violaceum abounds in soil and water ecosystems in tropical and subtropical regions and occasionally causes severe and often fatal human and animal infections. The quorum sensing (QS) system and biofilm formation are essential for C. violaceum's adaptability and pathogenicity, however, their interrelation is still unknown. C. violaceum's cell and biofilm morphology were examined by atomic force microscopy (AFM) in comparison with growth rates, QS-dependent violacein biosynthesis and biofilm biomass quantification. To evaluate QS regulation of these processes, the wild-type strain C. violaceum ATCC 31532 and its mini-Tn5 mutant C. violaceum NCTC 13274, cultivated with and without the QS autoinducer N-hexanoyl-L-homoserine lactone (C6-HSL), were used. We report for the first time the unusual morphological differentiation of C. violaceum cells, associated with biofilm development and directed by the QS autoinducer. AFM revealed numerous invaginations of the external cytoplasmic membrane of wild-type cells, which were repressed in the mutant strain and restored by exogenous C6-HSL. With increasing bacterial growth, polymer matrix extrusions formed in place of invaginations, whereas mutant cells were covered with a diffusely distributed extracellular substance. Thus, quorum sensing in C. violaceum involves a morphological differentiation that organises biofilm formation and leads to a highly differentiated matrix structure.

Enhanced biofiltration of O&G produced water comparing granular activated carbon and nutrients.

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Riley, Stephanie M; Ahoor, Danika C; Cath, Tzahi Y

2018-05-31

Large volumes of water are required for the development of unconventional oil and gas (O&G) wells. Water scarcity coupled with seismicity induced by deep-well disposal promote new O&G wastewater management strategies, specifically treatment and reuse. One technology that has been proven effective for removal of organic matter and solids is biologically active filtration (BAF) with granular active carbon (GAC); however, further optimization is needed to enhance BAF performance. This study evaluated three GAC media (one spent and two new) and two nutrient-mix supplements for enhanced removal of chemical oxygen demand (COD) and dissolved organic carbon (DOC). Biofilm development was also monitored and correlated to BAF performance. The spent GAC with extant biofilm quickly acclimated to PW and demonstrated up to 92% DOC removal (81% COD) in 24h, while little impact by nutrient addition was observed. In addition, virgin GAC was slow to establish a biofilm, indicating that appropriate GAC selection and pre-developed biofilm is critical for efficient BAF performance. Furthermore, the production of high quality BAF effluent (less than 20mg/L DOC) presents the opportunity to apply BAF as a pretreatment for subsequent desalination-expanding the potential for reuse applications of PW. Copyright © 2017. Published by Elsevier B.V.

Quorum sensing: a quantum perspective.

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Majumdar, Sarangam; Pal, Sukla

2016-09-01

Quorum sensing is the efficient mode of communication in the bacterial world. After a lot of advancements in the classical theory of quorum sensing few basic questions of quorum sensing still remain unanswered. The sufficient progresses in quantum biology demands to explain these questions from the quantum perspective as non trivial quantum effects already have manifested in various biological processes like photosynthesis, magneto-reception etc. Therefore, it's the time to review the bacterial communications from the quantum view point. In this article we carefully accumulate the latest results and arguments to strengthen quantum biology through the addition of quorum sensing mechanism in the light of quantum mechanics.

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

DEFF Research Database (Denmark)

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

2015-01-01

the 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...

General theory for integrated analysis of growth, gene, and protein expression in biofilms.

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Zhang, Tianyu; Pabst, Breana; Klapper, Isaac; Stewart, Philip S

2013-01-01

A theory for analysis and prediction of spatial and temporal patterns of gene and protein expression within microbial biofilms is derived. The theory integrates phenomena of solute reaction and diffusion, microbial growth, mRNA or protein synthesis, biomass advection, and gene transcript or protein turnover. Case studies illustrate the capacity of the theory to simulate heterogeneous spatial patterns and predict microbial activities in biofilms that are qualitatively different from those of planktonic cells. Specific scenarios analyzed include an inducible GFP or fluorescent protein reporter, a denitrification gene repressed by oxygen, an acid stress response gene, and a quorum sensing circuit. It is shown that the patterns of activity revealed by inducible stable fluorescent proteins or reporter unstable proteins overestimate the region of activity. This is due to advective spreading and finite protein turnover rates. In the cases of a gene induced by either limitation for a metabolic substrate or accumulation of a metabolic product, maximal expression is predicted in an internal stratum of the biofilm. A quorum sensing system that includes an oxygen-responsive negative regulator exhibits behavior that is distinct from any stage of a batch planktonic culture. Though here the analyses have been limited to simultaneous interactions of up to two substrates and two genes, the framework applies to arbitrarily large networks of genes and metabolites. Extension of reaction-diffusion modeling in biofilms to the analysis of individual genes and gene networks is an important advance that dovetails with the growing toolkit of molecular and genetic experimental techniques.

[Effect of luxS overexpression on biofilm formation by Streptococcus mutans].

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He, Zhiyan; Wang, Yuxia; Huang, Zhengwei

2015-09-01

To evaluate the effect of quorum sensing luxS gene on biofilm formation through construction of a luxS overexpression strain by Streptococcus mutans (Sm). In order to construct pIB-luxS plasmid, the luxS gene fragment amplified by PCR was inserted into the shuttle plasmid pIB169 by corresponding double digests. The pIB-luxS plasmid was linearized electro-transformed into Sm cell and the overexpression strain was selected on chloramphenicol plate and testified by electrophoresis and western blot. The growth rate of both Sm wild type strain and its luxS overexpression strain were observed. Methyl thiazolyl tetrazolium (MTT) assay method was used to compare the biofilm formation quantification by both strains at different time points and containing different sucrose. The structures of the biofilms were observed by using confocal laser scanning microscopy, and biofilm-related gene expressions were investigated by real-time PCR. All experiments were performed in triplicate. The luxS overexpression strain was successfully constructed and confirmed by electrophoresis and Western blotting. The planktonic growth mode of the wild-type and luxS overexpression strain showed no difference, but biofilm formed by Sm overexpression strain was 0.400 ± 0.009 and 0.609 ± 0.041 at 14 and 24 h, higher than the wild type strain biofilm at the same time point (0.352 ± 0.028 and 0.533 ± 0.014, respectively, P overexpression strain raised to 1.041 ± 0.038, higher than that by the wild type strain (0.831 ± 0.020, P overexpression strain aggregated into distinct clusters on structure, genes expression including gtfB, ftf, gbpB, relA, brpA, smu630, comDE, vicR were increased (6.10 ± 0.12, 3.34 ± 0.07, 8.75 ± 0.13, 2.96 ± 0.04, 5.20 ± 0.19, 2.20 ± 0.06, 2.32 ± 0.07 and 10.67 ± 0.57 fold) compared to the wild-type strain (P < 0.05). Quorum sensing luxS gene can promote the biofilm formation of Sm.

Inhibitory effect of farnesol on biofilm formation by Candida tropicalis

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E Zibafar

2009-03-01

Full Text Available ABSTRACT Background: Candidiasis associated with indwelling medical devices is especially problematic since they can act as substrates for biofilm growth which are highly resistant to antifungal drugs. Farnesol is a quorum-sensing molecule that inhibits filamentation and biofilm formation in Candida albicans. Since in recent years Candida tropicalis have been reported as an important and common non-albicans Candida species with high drug resistance pattern, the inhibitory effect of farnesol on biofilm formation by Candida tropicalis was evaluated. Methods: Five Candida tropicalis strains were treated with different concentration of farnesol (0, 30 and 300 µM after 0, 1 and 4 hrs of adherence and then they were maintained under biofilm formation condition in polystyrene, 96-well microtiter plates at 37°C for 48 hrs. Biofilm formation was measured by a semiquantitative colorimetric technique based on reduction assay of 2,3- bis  -2H-tetrazolium- 5- carboxanilide (XTT. Results: The results indicated that the initial adherence time had no effect on biofilm formation and low concentration of farnesol (30 µM could not inhibit biofilm formation. However the presence of non-adherent cells increased biofilm formation significantly and the high concentration of farnesol (300 µM could inhibit biofilm formation. Conclusion: Results of this study showed that the high concentration of farnesol could inhibit biofilm formation and may be used as an adjuvant in prevention and in therapeutic strategies with antifungal drugs.

Control of Biofilms with the Fatty Acid Signaling Molecule cis-2-Decenoic Acid

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Cláudia N. H. Marques

2015-11-01

Full Text Available Biofilms are complex communities of microorganisms in organized structures attached to surfaces. Importantly, biofilms are a major cause of bacterial infections in humans, and remain one of the most significant challenges to modern medical practice. Unfortunately, conventional therapies have shown to be inadequate in the treatment of most chronic biofilm infections based on the extraordinary innate tolerance of biofilms to antibiotics. Antagonists of quorum sensing signaling molecules have been used as means to control biofilms. QS and other cell-cell communication molecules are able to revert biofilm tolerance, prevent biofilm formation and disrupt fully developed biofilms, albeit with restricted effectiveness. Recently however, it has been demonstrated that Pseudomonas aeruginosa produces a small messenger molecule cis-2-decenoic acid (cis-DA that shows significant promise as an effective adjunctive to antimicrobial treatment of biofilms. This molecule is responsible for induction of the native biofilm dispersion response in a range of Gram-negative and Gram-positive bacteria and in yeast, and has been shown to reverse persistence, increase microbial metabolic activity and significantly enhance the cidal effects of conventional antimicrobial agents. In this manuscript, the use of cis-2-decenoic acid as a novel agent for biofilm control is discussed. Stimulating the biofilm dispersion response as a novel antimicrobial strategy holds significant promise for enhanced treatment of infections and in the prevention of biofilm formation.

Biofilm Formation Derived from Ambient Air and the Characteristics of Apparatus

International Nuclear Information System (INIS)

Kanematsu, H; Kougo, H; Kuroda, D; Itho, H; Ogino, Y; Yamamoto, Y

2013-01-01

Biofilm is a kind of thin film on solidified matters, being derived from bacteria. Generally, planktonic bacteria float in aqueous environments, soil or air, most of which can be regarded as oligotrophic environments. Since they have to survive by instinct, they seek for nutrients that would exist on materials surfaces as organic matters. Therefore, bacteria attach materials surfaces reversibly. The attachment and detachment repeat for a while and finally, they attach on them irreversibly and the number of bacteria on them increases. At a threshold number, bacteria produce polymeric matters at the same time by quorum sensing mechanism and the biofilm produces on material surfaces. The biofilm produced in that way generally contains water (more than 80%), EPS (Exopolymeric Substance) and bacteria themselves. And they might bring about many industrial problems, fouling, corrosion etc. Therefore, it is very important for us to control and prevent the biofilm formation properly. However, it is generally very hard to produce biofilm experimentally and constantly in ambient atmosphere on labo scale. The authors invented an apparatus where biofilm could form on specimen's surfaces from house germs in the ambient air. In this experiment, we investigated the basic characteristics of the apparatus, reproducibility, the change of biofilm with experimental time, the quality change of water for biofilm formation and their significance for biofilm research.

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

DEFF Research Database (Denmark)

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

2012-01-01

of traditional antibiotics to treat infections caused by bacterial biofilms and multidrug-resistant bacteria. Several QSIs of natural origin have been identified, and in this study, several common food products and plants were extracted and screened for QSI activity in an attempt to isolate and characterize...... to transcend problems with selective pressures for antibiotic resistance, is to interrupt bacterial communication, also known as quorum sensing (QS), by means of signal antagonists, the so-called QS inhibitors (QSIs). Furthermore, QSI agents offer a potential solution to the deficiencies associated with use......-diode array detector-mass spectrometry (LC-DAD-MS) and nuclear magnetic resonance (NMR) spectroscopy as iberin—an isothiocyanate produced by many members of the Brassicaceae family. Real-time PCR (RT-PCR) and DNA microarray studies showed that iberin specifically blocks expression of QS-regulated genes in P...

Roles of Extracellular Polysaccharides and Biofilm Formation in Heavy Metal Resistance of Rhizobia

OpenAIRE

Natalia Nocelli; Pablo C. Bogino; Erika Banchio; Walter Giordano

2016-01-01

Bacterial surface components and extracellular compounds, particularly flagella, lipopolysaccharides (LPSs), and exopolysaccharides (EPSs), in combination with environmental signals and quorum-sensing signals, play crucial roles in bacterial autoaggregation, biofilm development, survival, and host colonization. The nitrogen-fixing species Sinorhizobium meliloti (S. meliloti) produces two symbiosis-promoting EPSs: succinoglycan (or EPS I) and galactoglucan (or EPS II). Studies of the S. melilo...

Anti-Biofilm and Antivirulence Activities of Metabolites from Plectosphaerella cucumerina against Pseudomonas aeruginosa

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Jinwei Zhou

2017-05-01

Full Text Available This study reported the efficacy of the metabolites of Plectosphaerella cucumerina, one phyllosphere fungus from Orychophragmus violaceus, against Pseudomonas aeruginosa quorum sensing (QS and QS-regulated biofilms. The minimum inhibitory concentration (MIC of the ethyl acetate (EtOAc extract from P. cucumerina against P. aeruginosa PAO1 was 1.25 mg mL−1. At sub-MIC concentrations, P. cucumerina extract (0.25–1 mg mL−1 not only inhibited biofilm formation but also disrupted preformed biofilms of P. aeruginosa PAO1 without affecting its growth. Fluorescence and scanning electron microscope (SEM showed architectural disruption of the biofilms when treated with P. cucumerina metabolites. Further investigation demonstrated that metabolites in P. cucumerina attenuated the QS-dependent virulence factors. LC-MS/MS spectra coupled with experimentally standard samples suggested that patulin and emodin might act as the principal components possessing anti-biofilm and antivirulence activities. This is the first report of (1 the isolation of P. cucumerina from the phyllosphere of O. violaceus and (2 anti-biofilm, antivirulence, and biofilm disruption activities of this fungus. Thus, this study provides fascinating new pathways for screening antipathogenic agents.

Revealing strategies of quorum sensing in Azospirillum brasilense strains Ab-V5 and Ab-V6.

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Fukami, Josiane; Abrantes, Julia Laura Fernandes; Del Cerro, Pablo; Nogueira, Marco Antonio; Ollero, Francisco Javier; Megías, Manuel; Hungria, Mariangela

2018-01-01

Azospirillum brasilense is an important plant-growth promoting bacterium (PGPB) that requires several critical steps for root colonization, including biofilm and exopolysaccharide (EPS) synthesis and cell motility. In several bacteria these mechanisms are mediated by quorum sensing (QS) systems that regulate the expression of specific genes mediated by the autoinducers N-acyl-homoserine lactones (AHLs). We investigated QS mechanisms in strains Ab-V5 and Ab-V6 of A. brasilense, which are broadly used in commercial inoculants in Brazil. Neither of these strains carries a luxI gene, but there are several luxR solos that might perceive AHL molecules. By adding external AHLs we verified that biofilm and EPS production and cell motility (swimming and swarming) were regulated via QS in Ab-V5, but not in Ab-V6. Differences were observed not only between strains, but also in the specificity of LuxR-type receptors to AHL molecules. However, Ab-V6 was outstanding in indole acetic acid (IAA) synthesis and this molecule might mimic AHL signals. We also applied the quorum quenching (QQ) strategy, obtaining transconjugants of Ab-V5 and Ab-V6 carrying a plasmid with acyl-homoserine lactonase. When maize (Zea mays L.) was inoculated with the wild-type and transconjugant strains, plant growth was decreased with the transconjugant of Ab-V5-confirming the importance of an AHL-mediated QS system-but did not affect plant growth promotion by Ab-V6.

CdTe–TiO2 nanocomposite: an impeder of bacterial growth and biofilm

International Nuclear Information System (INIS)

Gholap, Haribhau; Yadav, Prasad; Ogale, Satishchandra; Patil, Rajendra; Gade, Wasudeo; Banpurkar, Arun

2013-01-01

The resurgence of infectious diseases and associated issues related to antibiotic resistance has raised enormous challenges which may possibly be confronted primarily by nanotechnology routes. One key need of critical significance in this context is the development of an agent capable of inhibiting quorum sensing mediated biofilm formation in pathogenic organisms. In this work we examine the possible use of a nanocomposite, CdTe–TiO 2 , as an impeder of growth and biofilm. In the presence of CdTe–TiO 2 , scanning electron microscopy (SEM) analysis shows exposed cells without the surrounding matrix. Confocal laser scanning microscopy shows spatially distributed fluorescence, a typical indication of an impeded biofilm, as opposed to the control which shows matrix-covered cells and continuous fluorescence, typical of biofilm formation. Quantitatively, the inhibition of biofilm was ∼57%. CdTe–TiO 2 also exhibits good antibacterial properties against Gram positive and Gram negative organisms by virtue of the generation of reactive oxygen species inside the cells, reflected by a ruptured appearance in the SEM analysis. (paper)

Quorum Quenching Revisited—From Signal Decays to Signalling Confusion

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Kok-Gan Chan

2012-04-01

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

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

DEFF Research Database (Denmark)

Huber, B.; Riedel, K.; Hentzer, Morten

2001-01-01

Burkholderia cepacia and Pseudomonas aeruginosa often co-exist as mixed biofilms in the lungs of patients suffering from cystic fibrosis (CF). Here, the isolation of random mini-Tn5 insertion mutants of B. cepacia H111 defective in biofilm formation on an abiotic surface is reported. It is demons......Burkholderia cepacia and Pseudomonas aeruginosa often co-exist as mixed biofilms in the lungs of patients suffering from cystic fibrosis (CF). Here, the isolation of random mini-Tn5 insertion mutants of B. cepacia H111 defective in biofilm formation on an abiotic surface is reported...

Nanoparticles as Efflux Pump and Biofilm Inhibitor to Rejuvenate Bactericidal Effect of Conventional Antibiotics

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Gupta, Divya; Singh, Ajeet; Khan, Asad U.

2017-07-01

The universal problem of bacterial resistance to antibiotic reflects a serious threat for physicians to control infections. Evolution in bacteria results in the development of various complex resistance mechanisms to neutralize the bactericidal effect of antibiotics, like drug amelioration, target modification, membrane permeability reduction, and drug extrusion through efflux pumps. Efflux pumps acquire a wide range of substrate specificity and also the tremendous efficacy for drug molecule extrusion outside bacterial cells. Hindrance in the functioning of efflux pumps may rejuvenate the bactericidal effect of conventional antibiotics. Efflux pumps also play an important role in the exclusion or inclusion of quorum-sensing biomolecules responsible for biofilm formation in bacterial cells. This transit movement of quorum-sensing biomolecules inside or outside the bacterial cells may get interrupted by impeding the functioning of efflux pumps. Metallic nanoparticles represent a potential candidate to block efflux pumps of bacterial cells. The application of nanoparticles as efflux pump inhibitors will not only help to revive the bactericidal effect of conventional antibiotics but will also assist to reduce biofilm-forming capacity of microbes. This review focuses on a novel and fascinating application of metallic nanoparticles in synergy with conventional antibiotics for efflux pump inhibition.

Heterogeneity in quorum sensing-regulated bioluminescence of Vibrio harveyi.

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Anetzberger, Claudia; Pirch, Torsten; Jung, Kirsten

2009-07-01

Quorum sensing (QS) refers to the ability of bacterial populations to read out the local environment for cell density and to collectively activate gene expression. Vibrio harveyi, one of the best characterized model organisms in QS, was used to address the question how single cells behave within a QS-activated community in a homogeneous environment. Analysis of the QS-regulated bioluminescence of a wild type strain revealed that even at high cell densities only 69% of the cells of the population produced bioluminescence, 25% remained dark and 6% were dead. Moreover, light intensities greatly varied from cell to cell at high population density. Addition of autoinducer to a bright liquid culture of V. harveyi increased the percentage of luminescent cells up to 98%, suggesting that V. harveyi produces and/or keeps the autoinducers at non-saturating concentrations. In contrast, all living cells of a constitutive QS-active mutant (DeltaluxO) produced light. We also found that QS affects biofilm formation in V. harveyi. Our data provide first evidence that a heterogeneous population produces more biofilm than a homogeneous one. It is suggested that even a QS-committed population of V. harveyi takes advantage of heterogeneity, which extends the current view of QS-regulated uniformity.

Long-Chain 4-Aminoquinolines as Quorum Sensing Inhibitors in Serratia marcescens and Pseudomonas aeruginosa.

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Aleksić, Ivana; Šegan, Sandra; Andrić, Filip; Zlatović, Mario; Moric, Ivana; Opsenica, Dejan M; Senerovic, Lidija

2017-05-19

Antibiotic resistance has become a serious global threat to public health; therefore, improved strategies and structurally novel antimicrobials are urgently needed to combat infectious diseases. Here we report a new type of highly potent 4-aminoquinoline derivatives as quorum sensing inhibitors in Serratia marcescens and Pseudomonas aeruginosa, exhibiting weak bactericidal activities (minimum inhibitory concentration (MIC) > 400 μM). Through detailed structure-activity study, we have identified 7-Cl and 7-CF 3 substituted N-dodecylamino-4-aminoquinolines (5 and 10) as biofilm formation inhibitors with 50% biofilm inhibition at 69 μM and 63 μM in S. marcescens and P. aeruginosa, respectively. These two compounds, 5 and 10, are the first quinoline derivatives with anti-biofilm formation activity reported in S. marcescens. Quantitative structure-activity relationship (QSAR) analysis identified structural descriptors such as Wiener indices, hyper-distance-path index (HDPI), mean topological charge (MTC), topological charge index (TCI), and log D(o/w) exp as the most influential in biofilm inhibition in this bacterial species. Derivative 10 is one of the most potent quinoline type inhibitors of pyocyanin production described so far (IC 50 = 2.5 μM). While we have demonstrated that 5 and 10 act as Pseudomonas quinolone system (PQS) antagonists, the mechanism of inhibition of S. marcescens biofilm formation with these compounds remains open since signaling similar to P. aeruginosa PQS system has not yet been described in Serratia and activity of these compounds on acylhomoserine lactone (AHL) signaling has not been detected. Our data show that 7-Cl and 7-CF 3 substituted N-dodecylamino-4-aminoquinolines present the promising scaffolds for developing antivirulence and anti-biofilm formation agents against multidrug-resistant bacterial species.

In Situ Molecular Imaging of the Biofilm and Its Matrix

Energy Technology Data Exchange (ETDEWEB)

Ding, Yuanzhao; Zhou, Yufan; Yao, Juan; Szymanski, Craig J.; Fredrickson, Jim K.; Shi, Liang; Cao, B.; Zhu, Zihua; Yu, Xiao-Ying

2016-11-15

Molecular mapping of live biofilms at submicron resolution presents a grand challenge. Here, we present the first chemical mapping results of biofilm extracellular polymeric sub-stance (EPS) components in biofilms using correlative imaging be-tween super resolution florescence microscopy and liquid time-of-flight secondary ion mass spectrometry (ToF-SIMS). Shewanella oneidensis is used as a model organism. Heavy metal anions chro-mate (Cr2O72-) consisting of chromium Cr (VI) was a model envi-ronmental stressor used to treat the biofilms. Of particular interest, biologically relevant water clusters have been first observed in the biofilms. Characteristic fragments of biofilm matrix components such as proteins, polysaccharides, and lipids can be spatially im-aged. Furthermore, characteristic fatty acids (e.g., palmitic acid), quinolone signal, and riboflavin fragments are found to respond af-ter the biofilm is treated with Cr (VI), leading to biofilm dispersion. Significant changes in water clusters and quorum sensing signals indicative of intercellular communication in the aqueous environ-ment are observed, suggesting that they might result in fatty acid synthesis and inhibit riboflavin production. The Cr (VI) reduction seems to follow the Mtr pathway leading to Cr (III) formation. Our approach potentially opens a new avenue for mechanistic insight of microbial community processes and communications using in situ imaging mass spectrometry and superresolution optical micros-copy.

Analysis of the biofilm proteome of Xylella fastidiosa

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Labate Carlos A

2011-09-01

related to quorum sensing, proving the existence of communication between cells, and thus the development of structuring the biofilm (mature biofilm leading to obstruction of vessels and development of disease. This paper reports a first proteomic analysis of mature biofilm of X. fastidiosa, opening new perspectives for understanding the biochemistry of mature biofilm growth in a plant pathogen.

Global Analysis of the Burkholderia thailandensis Quorum Sensing-Controlled Regulon

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

2014-01-01

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

Global analysis of the Burkholderia thailandensis quorum sensing-controlled regulon.

Science.gov (United States)

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

2014-04-01

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

Study on E. coli and Salmonella biofilms from fresh fruits and vegetables.

Science.gov (United States)

Amrutha, Balagopal; Sundar, Kothandapani; Shetty, Prathapkumar Halady

2017-04-01

Foodborne outbreaks associated with fresh fruits and vegetables are on the rise worldwide. Biofilm formation is one of the important traits of pathogens making them strongly attached to substrates as well as express virulence phenotypes. Present study investigates the biofilm forming ability of E. coli and Salmonella sp. isolated from fresh fruits and vegetables. A total of 53 strains, including 35 E. coli and 18 Salmonella sp. isolated from different fruit and vegetable samples were taken into account for the study. Initial screening for biofilm formation was done using Congo Red agar plate test. Results revealed that 22.8% E. coli and 22.2% Salmonella sp. were potential biofilm formers. However, the MTP (Micro-Titre Plate) assay suggested more isolates of both E. coli and Salmonella sp. were moderate to strong biofilm producers. Agar plate diffusion assay with Agrobacterium tumefaciens NTL-4 showed the production of quorum signaling molecules (AHLs) by three isolates of E. coli and one Salmonella sp. Two E. coli isolates showed a significant amount of EPS production indicating higher biofilm forming potential. The Presence of LUX R homologue gene ( sdi A) in two of the Salmonella isolates were confirmed by PCR which demonstrated their potential pathogenicity. Results of the work underline the biofilm forming and potentially virulent capacities of isolates from the surface of fruits and vegetables.

Probiotic Lactobacillus sp. inhibit growth, biofilm formation and gene expression of caries-inducing Streptococcus mutans.

Science.gov (United States)

Wasfi, Reham; Abd El-Rahman, Ola A; Zafer, Mai M; Ashour, Hossam M

2018-03-01

Streptococcus mutans contributes significantly to dental caries, which arises from homoeostasic imbalance between host and microbiota. We hypothesized that Lactobacillus sp. inhibits growth, biofilm formation and gene expression of Streptococcus mutans. Antibacterial (agar diffusion method) and antibiofilm (crystal violet assay) characteristics of probiotic Lactobacillus sp. against Streptococcus mutans (ATCC 25175) were evaluated. We investigated whether Lactobacillus casei (ATCC 393), Lactobacillus reuteri (ATCC 23272), Lactobacillus plantarum (ATCC 14917) or Lactobacillus salivarius (ATCC 11741) inhibit expression of Streptococcus mutans genes involved in biofilm formation, quorum sensing or stress survival using quantitative real-time polymerase chain reaction (qPCR). Growth changes (OD600) in the presence of pH-neutralized, catalase-treated or trypsin-treated Lactobacillus sp. supernatants were assessed to identify roles of organic acids, peroxides and bacteriocin. Susceptibility testing indicated antibacterial (pH-dependent) and antibiofilm activities of Lactobacillus sp. against Streptococcus mutans. Scanning electron microscopy revealed reduction in microcolony formation and exopolysaccharide structural changes. Of the oral normal flora, L. salivarius exhibited the highest antibiofilm and peroxide-dependent antimicrobial activities. All biofilm-forming cells treated with Lactobacillus sp. supernatants showed reduced expression of genes involved in exopolysaccharide production, acid tolerance and quorum sensing. Thus, Lactobacillus sp. can inhibit tooth decay by limiting growth and virulence properties of Streptococcus mutans. © 2018 The Authors. Journal of Cellular and Molecular Medicine published by John Wiley & Sons Ltd and Foundation for Cellular and Molecular Medicine.

Inhibition and dispersal of Agrobacterium tumefaciens biofilms by a small diffusible Pseudomonas aeruginosa exoproduct(s).

Science.gov (United States)

Hibbing, Michael E; Fuqua, Clay

2012-06-01

Environmental biofilms often contain mixed populations of different species. In these dense communities, competition between biofilm residents for limited nutrients such as iron can be fierce, leading to the evolution of competitive factors that affect the ability of competitors to grow or form biofilms. We have discovered a compound(s) present in the conditioned culture fluids of Pseudomonas aeruginosa that disperses and inhibits the formation of biofilms produced by the facultative plant pathogen Agrobacterium tumefaciens. The inhibitory activity is strongly induced when P. aeruginosa is cultivated in iron-limited conditions, but it does not function through iron sequestration. In addition, the production of the biofilm inhibitory activity is not regulated by the global iron regulatory protein Fur, the iron-responsive extracytoplasmic function σ factor PvdS, or three of the recognized P. aeruginosa quorum-sensing systems. In addition, the compound(s) responsible for the inhibition and dispersal of A. tumefaciens biofilm formation is likely distinct from the recently identified P. aeruginosa dispersal factor, cis-2-decenoic acid (CDA), as dialysis of the culture fluids showed that the inhibitory compound was larger than CDA and culture fluids that dispersed and inhibited biofilm formation by A. tumefaciens had no effect on biofilm formation by P. aeruginosa.

THE FORMATION OF BIOFILMS BY PSEUDOMONAS AERUGINOSA STRAINS, AND METHODS OF ITS CONTROL (REVIEW

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Sarkis-Ivanova VV

2017-03-01

Full Text Available The majority of natural bacterial populations exist in the form of biofilms, highly-structured multicellular communities incorporated in extracellular polymer matrix of own production. For a considerable part of clinically significant species this form of existence provides optimal conditions for reaching of pathogenic and colonizational potential, and also encourages saving of metabolically inactive part of population which is characterized by a low level of sensitivity to antibiotics impact. The latter plays a significant role in formation of chronic persistent infections resistant to antibiotics treatment. Members of microbial group are united basing on the principle which excludes antagonism, determines their nutritional, energetic and another connections between them and environment. Such a connection of microorganisms community behavior received a special definition of “quorum sensing”. Quorum sensing is an ability of some bacteria (probably, also another microorganisms to communicate and coordinate their behavior through secretion of substances which are the signals for coordination of certain behavior or interaction between bacteria of the same type or subtype depending on their growth tightness. When the concentration of excreted signaling agents reaches a borderline value the group of bacteria starts working as a single organism. Furthermore, signaling agents for Gram-negative and Gram-positive microorganisms differ. For instance, for Pseudomonas aeruginosa microorganism a signaling molecule of quorum sensing is acyl homoserine lactone, and biofilm created by this pathogen produces pyocyanin which functions as an electronic transporter in current generation. A large-scale investigation of P.aeruginosa biofilm morphology, mechanisms of its production and degradation, peculiarities of formation under different conditions and impact of various factors are at the infancy stage. According to undivided opinion of scientists who

Relative contributions of Vibrio polysaccharide and quorum sensing to the resistance of Vibrio cholerae to predation by heterotrophic protists.

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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.

Quorum decision-making in foraging fish shoals.

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Ashley J W Ward

Full Text Available Quorum responses provide a means for group-living animals to integrate and filter disparate social information to produce accurate and coherent group decisions. A quorum response may be defined as a steep increase in the probability of group members performing a given behaviour once a threshold minimum number of their group mates already performing that behaviour is exceeded. In a previous study we reported the use of a quorum response in group decision-making of threespine sticklebacks (Gasterosteus aculeatus under a simulated predation threat. Here we examine the use of quorum responses by shoals of sticklebacks in first locating and then leaving a foraging patch. We show that a quorum rule explains movement decisions by threespine sticklebacks toward and then away from a food patch. Following both to and from a food patch occurred when a threshold number of initiators was exceeded, with the threshold being determined by the group size.

Global Analysis of the Burkholderia thailandensis Quorum Sensing-Controlled Regulon

OpenAIRE

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

2014-01-01

Burkholderia thailandensis contains three acyl-homoserine lactone quorum sensing circuits and has two additional LuxR homologs. To identify B. thailandensis quorum sensing-controlled genes, we carried out transcriptome sequencing (RNA-seq) analyses of quorum sensing mutants and their parent. The analyses were grounded in the fact that we identified genes coding for factors shown previously to be regulated by quorum sensing among a larger set of quorum-controlled genes. We also found that gene...

Essential roles and regulation of the Legionella pneumophila collagen-like adhesin during biofilm formation.

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Julia Mallegol

Full Text Available Legionellosis is mostly caused by Legionella pneumophila (Lp and is defined by a severe respiratory illness with a case fatality rate ranging from 5 to 80%. In a previous study, we showed that a glycosaminoglycan (GAG-binding adhesin of Lp, named Lcl, is produced during legionellosis and is unique to the L. pneumophila species. Importantly, a mutant depleted in Lcl (Δlpg2644 is impaired in adhesion to GAGs and epithelial cells and in biofilm formation. Here, we examine the molecular function(s of Lcl and the transcriptional regulation of its encoding gene during different stages of the biofilm development. We show that the collagen repeats and the C-terminal domains of Lcl are crucial for the production of biofilm. We present evidence that Lcl is involved in the early step of surface attachment but also in intercellular interactions. Furthermore, we address the relationship between Lcl gene regulation during biofilm formation and quorum sensing (QS. In a static biofilm assay, we show that Lcl is differentially regulated during growth phases and biofilm formation. Moreover, we show that the transcriptional regulation of lpg2644, mediated by a prototype of QS signaling homoserine lactone (3OC12-HSL, may play a role during the biofilm development. Thus, transcriptional down-regulation of lpg2644 may facilitate the dispersion of Lp to reinitiate biofilm colonization on a distal surface.

Role and regulation of the orphan AphA protein of quorum sensing in pathogenic Vibrios.

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Lu, Renfei; Osei-Adjei, George; Huang, Xinxiang; Zhang, Yiquan

2018-03-01

Quorum sensing (QS), a cell-to-cell communication process, is widely distributed in the bacterial kingdom. Bacteria use QS to control gene expression in response to cell density by detecting the signal molecules called autoinducers. AphA protein is the master QS regulator of vibrios operating at low cell density. It regulates the expression of a variety of genes, especially those encoding virulence factors, flagella/motility and biofilm formation. The role and regulation of AphA in vibrios, especially in human pathogenic vibrios, are summarized in this review. Clarification of the roles of AphA will help us to understand the pathogenesis of vibrios.

AI-2 of Aggregatibacter actinomycetemcomitans Inhibits Candida albicans Biofilm Formation

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Endang W. Bachtiar

2014-07-01

Full Text Available Aggregatibacter actinomycetemcomitans, a Gram-negative bacterium, and Candida albicans, a polymorphic fungus, are both commensals of the oral cavity but both are opportunistic pathogens that can cause oral diseases. A. actinomycetemcomitans produces a quorum-sensing molecule called autoinducer-2 (AI-2, synthesized by LuxS, that plays an important role in expression of virulence factors, in intra- but also in interspecies communication. The aim of this study was to investigate the role of AI-2 based signaling in the interactions between C. albicans and A. actinomycetemcomitans. A. actinomycetemcomitans adhered to C. albicans and inhibited biofilm formation by means of a molecule that was secreted during growth. C. albicans biofilm formation increased significantly when co-cultured with A. actinomycetemcomitans luxS, lacking AI-2 production. Addition of wild-type-derived spent medium or synthetic AI-2 to spent medium of the luxS strain, restored inhibition of C. albicans biofilm formation to wild-type levels. Addition of synthetic AI-2 significantly inhibited hypha formation of C. albicans possibly explaining the inhibition of biofilm formation. AI-2 of A. actinomycetemcomitans is synthesized by LuxS, accumulates during growth and inhibits C. albicans hypha- and biofilm formation. Identifying the molecular mechanisms underlying the interaction between bacteria and fungi may provide important insight into the balance within complex oral microbial communities.

Flavonoids from Piper delineatum modulate quorum-sensing-regulated phenotypes in Vibrio harveyi.

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Martín-Rodríguez, Alberto J; Ticona, Juan C; Jiménez, Ignacio A; Flores, Ninoska; Fernández, José J; Bazzocchi, Isabel L

2015-09-01

Quorum sensing (QS), or bacterial cell-to-cell communication, is a key process for bacterial colonization of substrata through biofilm formation, infections, and production of virulence factors. In an ongoing investigation of bioactive secondary metabolites from Piper species, four new flavonoids (1-4), along with five known ones (5-9) were isolated from the leaves of Piper delineatum. Their stereostructures were established by spectroscopic and spectrometric methods, including 1D and 2D NMR experiments, and comparison with data reported in the literature. The compounds were screened for their ability to interfere with QS signaling in the bacterial model Vibrio harveyi. Four compounds from this series (2, 3, 6, and 7) exhibited remarkable activity in the micromolar range, being compounds 3 and 7 particularly attractive since they did not affect bacterial growth. The results suggest that these flavonoids disrupt QS-mediated bioluminescence by interaction with elements downstream LuxO in the QS circuit of V. harveyi, and also, they exhibited a strong dose-dependent inhibition of biofilm formation. The present findings shed light on the QS inhibition mechanisms of flavonoids, underlining their potential applications. Copyright © 2015 Elsevier Ltd. All rights reserved.

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

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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.

Coral-associated bacteria, quorum sensing disrupters, and the regulation of biofouling.

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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

Attenuation of Pseudomonas aeruginosa virulence by quorum sensing inhibitors

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

2003-01-01

Traditional treatment of infectious diseases is based on compounds that kill or inhibit growth of bacteria. A major concern with this approach is the frequent development of resistance to antibiotics. The discovery of communication systems (quorum sensing systems) regulating bacterial virulence has...... of natural furanone compounds can act as a potent antagonist of bacterial quorum sensing. We employed GeneChip((R)) microarray technology to identify furanone target genes and to map the quorum sensing regulon. The transcriptome analysis showed that the furanone drug specifically targeted quorum sensing...

Qualitative and quantitative determination of quorum sensing inhibition in vitro

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

2011-01-01

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...... efficacy of potential quorum sensing inhibitors (QSIs). Work on Pseudomonas aeruginosa has shown that chemical blockage of QS is a promising new antimicrobial strategy. Several live bacterial reporter systems been developed to screen extracts and pure compounds for QSI activity. Here we describe the usage...... 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 various QSI...

RbsB (NTHI_0632) mediates quorum signal uptake in nontypeable Haemophilus influenzae strain 86-028NP.

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Armbruster, Chelsie E; Pang, Bing; Murrah, Kyle; Juneau, Richard A; Perez, Antonia C; Weimer, Kristin E D; Swords, W Edward

2011-11-01

Nontypeable Haemophilus influenzae (NTHI) is a respiratory commensal and opportunistic pathogen, which persists within biofilms on airway mucosal surfaces. For many species, biofilm formation is impacted by quorum signalling. Our prior work shows that production of autoinducer-2 (AI-2) promotes biofilm development and persistence for NTHI 86-028NP. NTHI 86-028NP encodes an ABC transporter annotated as a ribose transport system that includes a protein (RbsB) with similarity to the Escherichia coli LsrB and Aggregatibacter actinomycetemcomitans RbsB proteins that bind AI-2. In this study, inactivation of rbsB significantly reduced uptake of AI-2 and the AI-2 precursor dihydroxypentanedione (DPD) by NTHI 86-028NP. Moreover, DPD uptake was not competitively inhibited by ribose or other pentose sugars. Transcript levels of rbsB increased in response to DPD and as bacteria approached stationary-phase growth. The NTHI 86-028NP rbsB mutant also formed biofilms with significantly reduced thickness and total biomass and reduced surface phosphorylcholine, similar to a luxS mutant. Infection studies revealed that loss of rbsB impaired bacterial persistence in the chinchilla middle ear, similar to our previous results with luxS mutants. Based on these data, we conclude that in NTHI 86-028NP, RbsB is a LuxS/AI-2 regulated protein that is required for uptake of and response to AI-2. © 2011 Blackwell Publishing Ltd.

Development of a biofilm inhibitor molecule against multidrug resistant Staphylococcus aureus associated with gestational urinary tract infections

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Balamurugan eP

2015-08-01

Full Text Available Urinary Tract Infection (UTI is a globally widespread human infection caused by an infestation of uropathogens. Eventhough, Escherichia coli is often quoted as being the chief among them, Staphylococcus aureus involvement in UTI especially in gestational UTI is often understated. Staphylococcal accessory regulator A (SarA is a quorum regulator of S. aureus that controls the expression of various virulence and biofilm phenotypes. Since SarA had been a focussed target for antibiofilm agent development, the study aims to develop a potential drug molecule targeting the SarA of S. aureus to combat biofilm associated infections in which it is involved. In our previous studies, we have reported the antibiofilm activity of SarA based biofilm inhibitor, (SarABI with a 50% minimum biofilm inhibitory concentration (MBIC50 value of 200 µg/mL against S. aureus associated with vascular graft infections and also the antibiofilm activity of the root ethanolic extracts of Melia dubia against uropathogenic E. coli. In the present study, in silico design of a hybrid molecule composed of a molecule screened from M. dubia root ethanolic extracts and a modified SarA based inhibitor (SarABIM was undertaken. SarABIM is a modified form of SarABI where the fluorine groups are absent in SarABIM. Chemical synthesis of the hybrid molecule, 4-(Benzylaminocyclohexyl 2-hydroxycinnamate (henceforth referred to as UTI Quorum-Quencher, UTIQQ was then performed, followed by in vitro and in vivo validation. The MBIC¬50 and MBIC90 of UTIQQ were found to be 15 µg/mL and 65 µg/mL respectively. Confocal laser scanning microscopy (CLSM images witnessed biofilm reduction and bacterial killing in either UTIQQ or in combined use of antibiotic gentamicin and UTIQQ. Similar results were observed with in vivo studies of experimental UTI in rat model. So, we propose that the drug UTIQQ would be a promising candidate when used alone or, in combination with an antibiotic for staphylococcal

Inhibiting effects of Streptococcus salivarius on competence-stimulating peptide-dependent biofilm formation by Streptococcus mutans.

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Tamura, S; Yonezawa, H; Motegi, M; Nakao, R; Yoneda, S; Watanabe, H; Yamazaki, T; Senpuku, H

2009-04-01

The effects of Streptococcus salivarius on the competence-stimulating peptide (CSP)-dependent biofilm formation by Streptococcus mutans were investigated. Biofilms were grown on 96-well microtiter plates coated with salivary components in tryptic soy broth without dextrose supplemented with 0.25% sucrose. Biofilm formations were stained using safranin and quantification of stained biofilms was performed by measuring absorbance at 492 nm. S. mutans formed substantial biofilms, whereas biofilms of S. salivarius were formed poorly in the medium conditions used. Furthermore, in combination cultures, S. salivarius strongly inhibited biofilm formation when cultured with S. mutans. This inhibition occurred in the early phase of biofilm formation and was dependent on inactivation of the CSP of S. mutans, which is associated with competence, biofilm formation, and antimicrobial activity of the bacterium, and is induced by expression of the comC gene. Comparisons between the S. mutans clinical strains FSC-3 and FSC-3DeltaglrA in separate dual-species cultures with S. salivarius indicated that the presence of the bacitracin transport ATP-binding protein gene glrA caused susceptibility to inhibition of S. mutans biofilm formation by S. salivarius, and was also associated with the regulation of CSP production by com gene-dependent quorum sensing systems. It is considered that regulation of CSP by glrA in S. mutans and CSP inactivation by S. salivarius are important functions for cell-to-cell communication between biofilm bacteria and oral streptococci such as S. salivarius. Our results provide useful information for understanding the ecosystem of oral streptococcal biofilms, as well as the competition between and coexistence of multiple species in the oral cavity.

Biomolecular Mechanisms of Pseudomonas aeruginosa and Escherichia coli Biofilm Formation

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Laverty, Garry; Gorman, Sean P.; Gilmore, Brendan F.

2014-01-01

Pseudomonas aeruginosa and Escherichia coli are the most prevalent Gram-negative biofilm forming medical device associated pathogens, particularly with respect to catheter associated urinary tract infections. In a similar manner to Gram-positive bacteria, Gram-negative biofilm formation is fundamentally determined by a series of steps outlined more fully in this review, namely adhesion, cellular aggregation, and the production of an extracellular polymeric matrix. More specifically this review will explore the biosynthesis and role of pili and flagella in Gram-negative adhesion and accumulation on surfaces in Pseudomonas aeruginosa and Escherichia coli. The process of biofilm maturation is compared and contrasted in both species, namely the production of the exopolysaccharides via the polysaccharide synthesis locus (Psl), pellicle Formation (Pel) and alginic acid synthesis in Pseudomonas aeruginosa, and UDP-4-amino-4-deoxy-l-arabinose and colonic acid synthesis in Escherichia coli. An emphasis is placed on the importance of the LuxR homologue sdiA; the luxS/autoinducer-II; an autoinducer-III/epinephrine/norepinephrine and indole mediated Quorum sensing systems in enabling Gram-negative bacteria to adapt to their environments. The majority of Gram-negative biofilms consist of polysaccharides of a simple sugar structure (either homo- or heteropolysaccharides) that provide an optimum environment for the survival and maturation of bacteria, allowing them to display increased resistance to antibiotics and predation. PMID:25438014

Biomolecular Mechanisms of Pseudomonas aeruginosa and Escherichia coli Biofilm Formation

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Garry Laverty

2014-07-01

Full Text Available Pseudomonas aeruginosa and Escherichia coli are the most prevalent Gram-negative biofilm forming medical device associated pathogens, particularly with respect to catheter associated urinary tract infections. In a similar manner to Gram-positive bacteria, Gram-negative biofilm formation is fundamentally determined by a series of steps outlined more fully in this review, namely adhesion, cellular aggregation, and the production of an extracellular polymeric matrix. More specifically this review will explore the biosynthesis and role of pili and flagella in Gram-negative adhesion and accumulation on surfaces in Pseudomonas aeruginosa and Escherichia coli. The process of biofilm maturation is compared and contrasted in both species, namely the production of the exopolysaccharides via the polysaccharide synthesis locus (Psl, pellicle Formation (Pel and alginic acid synthesis in Pseudomonas aeruginosa, and UDP-4-amino-4-deoxy-l-arabinose and colonic acid synthesis in Escherichia coli. An emphasis is placed on the importance of the LuxR homologue sdiA; the luxS/autoinducer-II; an autoinducer-III/epinephrine/norepinephrine and indole mediated Quorum sensing systems in enabling Gram-negative bacteria to adapt to their environments. The majority of Gram-negative biofilms consist of polysaccharides of a simple sugar structure (either homo- or heteropolysaccharides that provide an optimum environment for the survival and maturation of bacteria, allowing them to display increased resistance to antibiotics and predation.

The natural antimicrobial carvacrol inhibits quorum sensing in Chromobacterium violaceum and reduces bacterial biofilm formation at sub-lethal concentrations

NARCIS (Netherlands)

Burt, Sara A|info:eu-repo/dai/nl/140114432; Ojo-Fakunle, Victoria T A; Woertman, Jenifer; Veldhuizen, Edwin J A|info:eu-repo/dai/nl/19545264X

2014-01-01

The formation of biofilm by bacteria confers resistance to biocides and presents problems in medical and veterinary clinical settings. Here we report the effect of carvacrol, one of the major antimicrobial components of oregano oil, on the formation of biofilms and its activity on existing biofilms.

Optimal census by quorum sensing

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Taillefumier, Thibaud

Bacteria regulate their gene expression in response to changes in local cell density in a process called quorum sensing. To synchronize their gene-expression programs, these bacteria need to glean as much information as possible about local density. Our study is the first to physically model the flow of information in a quorum-sensing microbial community, wherein the internal regulator of the individual's response tracks the external cell density via an endogenously generated shared signal. Combining information theory and Lagrangian optimization, we find that quorum-sensing systems can improve their information capabilities by tuning circuit feedbacks. At the population level, external feedback adjusts the dynamic range of the shared input to individuals' detection channels. At the individual level, internal feedback adjusts the regulator's response time to dynamically balance output noise reduction and signal tracking ability. Our analysis suggests that achieving information benefit via feedback requires dedicated systems to control gene expression noise, such as sRNA-based regulation.

SaeRS Is Responsive to Cellular Respiratory Status and Regulates Fermentative Biofilm Formation in Staphylococcus aureus.

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Mashruwala, Ameya A; Gries, Casey M; Scherr, Tyler D; Kielian, Tammy; Boyd, Jeffrey M

2017-08-01

Biofilms are multicellular communities of microorganisms living as a quorum rather than as individual cells. The bacterial human pathogen Staphylococcus aureus uses oxygen as a terminal electron acceptor during respiration. Infected human tissues are hypoxic or anoxic. We recently reported that impaired respiration elicits a p rogrammed c ell l ysis (PCL) phenomenon in S. aureus leading to the release of cellular polymers that are utilized to form biofilms. PCL is dependent upon the AtlA murein hydrolase and is regulated, in part, by the SrrAB two-component regulatory system (TCRS). In the current study, we report that the SaeRS TCRS also governs fermentative biofilm formation by positively influencing AtlA activity. The SaeRS-modulated factor fibronectin-binding protein A (FnBPA) also contributed to the fermentative biofilm formation phenotype. SaeRS-dependent biofilm formation occurred in response to changes in cellular respiratory status. Genetic evidence presented suggests that a high cellular titer of phosphorylated SaeR is required for biofilm formation. Epistasis analyses found that SaeRS and SrrAB influence biofilm formation independently of one another. Analyses using a mouse model of orthopedic implant-associated biofilm formation found that both SaeRS and SrrAB govern host colonization. Of these two TCRSs, SrrAB was the dominant system driving biofilm formation in vivo We propose a model wherein impaired cellular respiration stimulates SaeRS via an as yet undefined signal molecule(s), resulting in increasing expression of AtlA and FnBPA and biofilm formation. Copyright © 2017 American Society for Microbiology.

Quorum sensing molecules production by nosocomial and soil isolates Acinetobacter baumannii.

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Erdönmez, Demet; Rad, Abbas Yousefi; Aksöz, Nilüfer

2017-12-01

Acinetobacter species remain alive in hospitals on various surfaces, both dry and moist, forming an important source of hospital infections. These bacteria are naturally resistant to many antibiotic classes. Although the role of the quorum sensing system in regulating the virulence factors of Acinetobacter species has not been fully elucidated, it has been reported that they play a role in bacterial biofilm formation. The biofilm formation helps them to survive under unfavorable growth conditions and antimicrobial treatments. It is based on the accumulation of bacterial communication signal molecules in the area. In this study, we compared the bacterial signal molecules of 50 nosocomial Acinetobacter baumannii strain and 20 A. baumannii strain isolated from soil. The signal molecules were detected by the biosensor bacteria (Chromobacterium violaceum 026, Agrobacterium tumefaciens A136, and Agrobacterium tumefaciens NTL1) and their separation was determined by thin-layer chromatography. As a result, it has been found that soil-borne isolates can produce 3-oxo-C8-AHL and C8-AHL, whereas nosocomial-derived isolates can produce long-chain signals such as C10-AHL, C12-AHL, C14-AHL and C16-AHL. According to these results, it is possible to understand that these signal molecules are found in the infection caused by A. baumannii. The inhibition of this signaling molecules in a communication could use to prevent multiple antibiotic resistance of these bacteria.

Social- og sundhedsprofessioner, videnskab, teknologier og nye udfordringer

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Larsen, Kristian

2015-01-01

mere bredt i samfundet. Konkret er her tale om studier af faggrupperne fysioterapi, sygepleje, socialrådgivere og jordemødre, der alle udgør dele af velfærdsstatens reproduktive arbejdsområder. Fire af de fem artikler der indgår i temanummeret har udspring i det norsk-danske forskningsprojekt...... universiteter, professionshøjskoler, hospitaler og kommuner, se den danske (www.phlegethon.net) eller norske hjemmeside (http://www.hioa.no/Research-and-Development/Our-research/Helse-omsorg-og-velferd-HOV/Phlegethon-nettverket2).De fire artikler (Højbjerg et al; Sandholm et al; Sandholm et al; Søbjerg et al...... sammenhænge og med forskellige professionelle baggrunde og med inddragelse af supplerende teorier og metodiske tilgange, men med en vis fælles sociologisk inspireret epistemologi som udgangspunkt. De fire artikler har på forskellig måde og dybde gjort brug af Bourdieu og hans tænkning omkring felt, habitus og...

The LuxS/AI-2 Quorum-Sensing System of Streptococcus pneumoniae Is Required to Cause Disease, and to Regulate Virulence- and Metabolism-Related Genes in a Rat Model of Middle Ear Infection

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Mukesh K. Yadav

2018-05-01

Full Text Available Objective:Streptococcus pneumoniae colonizes the nasopharynx of children, and from nasopharynx it could migrate to the middle ear and causes acute otitis media (AOM. During colonization and AOM, the pneumococcus forms biofilms. In vitro biofilm formation requires a functional LuxS/AI-2 quorum-sensing system. We investigated the role of LuxS/AI-2 signaling in pneumococcal middle ear infection, and identified the genes that are regulated by LuxS/AI-2 during pneumococcal biofilm formation.Methods:Streptococcus pneumoniae D39 wild-type and an isogenic D39ΔluxS strain were utilized to evaluate in vitro biofilm formation, and in vivo colonization and epithelial damage using a microtiter plate assay and a rat model of pneumococcal middle ear infection, respectively. Biofilm structures and colonization and epithelial damage were evaluated at the ultrastructural level by scanning electron microscopy and confocal microscopy. Microarrays were used to investigate the global genes that were regulated by LuxS/AI-2 during biofilm formation.Results: The biofilm biomass and density of D39ΔluxS were significantly (p < 0.05 lower than those of D39 wild-type. SEM and confocal microscopy revealed that D39ΔluxS formed thin biofilms in vitro compared with D39 wild-type. The in vivo model of middle ear infection showed that D39ΔluxS resulted in ~60% less (p < 0.05 bacterial colonization than the wild-type. SEM analysis of the rat middle ears revealed dense biofilm-like cell debris deposited on the cilia in wild-type D39-infected rats. However, little cell debris was deposited in the middle ears of the D39ΔluxS-inoculated rats, and the cilia were visible. cDNA-microarray analysis revealed 117 differentially expressed genes in D39ΔluxS compared with D39 wild-type. Among the 66 genes encoding putative proteins and previously characterized proteins, 60 were significantly downregulated, whereas 6 were upregulated. Functional annotation revealed that genes involved in

Phosphoenolpyruvate phosphotransferase system components positively regulate Klebsiella biofilm formation

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Yu-Tze Horng

2018-04-01

Full Text Available Background/Purpose: Klebsiella pneumoniae is one of the leading causes of device-related infections (DRIs, which are associated with attachment of bacteria to these devices to form a biofilm. The latter is composed of not only bacteria but also extracellular polymeric substances (EPSes consisting of extracellular DNAs, polysaccharides, and other macromolecules. The phosphoenolpyruvate (PEP:carbohydrate phosphotransferase system (PTS regulates diverse processes of bacterial physiology. In the genome of K. pneumoniae MGH 78578, we found an uncharacterized enzyme II complex homolog of PTS: KPN00353 (EIIA homolog, KPN00352 (EIIB homolog, and KPN00351 (EIIC homolog. The aim of this study was to characterize the potential physiological role of KPN00353, KPN00352, and KPN00351 in biofilm formation by K. pneumoniae. Methods/Results: We constructed the PTS mutants and recombinant strains carrying the gene(s of PTS. The recombinant K. pneumoniae strain overexpressing KPN00353–KPN00352–KPN00351 produced more extracellular matrix than did the vector control according to transmission and scanning electron microscopy. Judging by quantification of biofilm formation, of extracellular DNA (eDNA, and of capsular polysaccharide, the recombinant strain overexpressing KPN00353-KPN00352-KPN00351 produced more biofilm and capsular polysaccharide after overnight culture and more eDNA in the log phase as compared to the vector control. Conclusion: The genes, KPN00353–KPN00352–KPN00351, encode a putative enzyme II complex in PTS and positively regulate biofilm formation by enhancing production of eDNA and capsular polysaccharide in K. pneumoniae. Five proteins related to chaperones, to the citric acid cycle, and to quorum sensing are upregulated by the KPN00353–KPN00352–KPN00351 system. Keywords: Klebsiella, PTS, Biofilm, eDNA, Polysaccharide

Inhibiting effects of fructanase on competence-stimulating peptide-dependent quorum sensing system in Streptococcus mutans.

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Suzuki, Yusuke; Nagasawa, Ryo; Senpuku, Hidenobu

2017-09-01

Streptococcus mutans produces glucosyltransferases encoded by the gtfB and gtfC genes, which synthesize insoluble glucan, and both insoluble and soluble glucans by conversion of sucrose, and are known as principal agents to provide strong biofilm formation and demineralization on tooth surfaces. S. mutans possess a Com-dependent quorum sensing (QS) system, which is important for survival in severe conditions. The QS system is stimulated by the interaction between ComD {Receptor to competence-stimulating peptide (CSP)} encoded by the comD and CSP encoded by the comC, and importantly associated with bacteriocin production and genetic competence. Previously, we found enzyme fructanase (FruA) as a new inhibitor for the glucan-dependent biofilm formation. In the present study, inhibiting effects by FruA on glucan-independent biofilm formation of S. mutans UA159, UA159.gtfB - , UA159.gtfC - , and UA159.gtfBC - were observed in sucrose and no sucrose sugars-supplemented conditions using the plate assay. The reduction of UA159.comC - and UA159.comD - biofilm formation were also observed as compared with UA159 in same conditions. These results suggested that inhibitions of glucan-independent and Com-dependent biofilm formation were involved in the inhibiting mechanism by FruA. To more thoroughly investigate effects by FruA on the QS system, we examined on CSP-stimulated and Com-dependent bacteriocin production and genetic transformation. FruA inhibited bacteriocin production in collaboration with CSP and genetic transformation in bacterial cell conditions treated with FruA. Our findings show that FruA has multiple effects that inhibit survival functions of S. mutans, including biofilm formation and CSP-dependent QS responses, indicating its potential use as an agent for prevention of dental caries. Copyright © 2017 Japanese Society of Chemotherapy and The Japanese Association for Infectious Diseases. Published by Elsevier Ltd. All rights reserved.

The organophosphate malathion disturbs gut microbiome development and the quorum-Sensing system.

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Gao, Bei; Chi, Liang; Tu, Pengcheng; Bian, Xiaoming; Thomas, Jesse; Ru, Hongyu; Lu, Kun

2018-02-01

The gut microbiome has tremendous potential to impact health and disease. Various environmental toxicants, including insecticides, have been shown to alter gut microbiome community structures. However, the mechanism that compositionally and functionally regulates gut microbiota remains unclear. Quorum sensing is known to modulate intra- and interspecies gene expression and coordinate population responses. It is unknown whether quorum sensing is disrupted when environmental toxicants cause perturbations in the gut microbiome community structure. To reveal the response of the quorum-sensing system to environmental exposure, we use a combination of Illumina-based 16S rRNA gene amplicon and shotgun metagenome sequencing to examine the impacts of a widely used organophosphate insecticide, malathion, on the gut microbiome trajectory, quorum sensing system and behaviors related to quorum sensing, such as motility and pathogenicity. Our results demonstrated that malathion perturbed the gut microbiome development, quorum sensing and quorum sensing related behaviors. These findings may provide a novel mechanistic understanding of the role of quorum-sensing in the gut microbiome toxicity of malathion. Copyright © 2017. Published by Elsevier B.V.

Thiazolidinedione-8 alters symbiotic relationship in C. albicans-S. mutans dual species biofilm

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Mark eFeldman

2016-02-01

Full Text Available The small molecule, thiazolidinedione-8 (S-8 was shown to impair biofilm formation of various microbial pathogens, including the fungus Candida albicans and Streptococcus mutans. Previously, we have evaluated the specific molecular mode of S-8 action against C. albicans biofilm-associated pathogenicity. In this study we investigated the influence of S-8 on dual species, C. albicans-S. mutans biofilm. We show that in the presence of S-8 a reduction of the co-species biofilm formation occurred with a major effect on C. albicans. Biofilm biomass and exopolysaccharide (EPS production were significantly reduced by S-8. Moreover, the agent caused oxidative stress associated with a strong induction of reactive oxygen species (ROS and hydrogen peroxide uptake inhibition by a mixed biofilm. In addition, S-8 altered symbiotic relationship between these species by a complex mechanism. Streptococcal genes associated with quorum sensing (comDE and luxS, EPS production (gtfBCD and gbpB, as well as genes related to protection against oxidative stress (nox and sodA were markedly upregulated by S-8. In contrast, fungal genes related to hyphae formation (hwp1, adhesion (als3, hydrophobicity (csh1 and oxidative stress response (sod1, sod2 and cat1 were downregulated in the presence of S-8. In addition, ywp1 gene associated with yeast form of C. albicans was induced by S-8, which is correlated with appearance of mostly yeast cells in S-8 treated dual species biofilms. We concluded that S-8 disturbs symbiotic balance between C. albicans and S. mutans in dual species biofilm.

Low Concentrations of Vitamin C Reduce the Synthesis of Extracellular Polymers and Destabilize Bacterial Biofilms

KAUST Repository

Pandit, Santosh

2017-12-26

Extracellular polymeric substances (EPS) produced by bacteria form a matrix supporting the complex three-dimensional architecture of biofilms. This EPS matrix is primarily composed of polysaccharides, proteins and extracellular DNA. In addition to supporting the community structure, the EPS matrix protects bacterial biofilms from the environment. Specifically, it shields the bacterial cells inside the biofilm, by preventing antimicrobial agents from getting in contact with them, thereby reducing their killing effect. New strategies for disrupting the formation of the EPS matrix can therefore lead to a more efficient use of existing antimicrobials. Here we examined the mechanism of the known effect of vitamin C (sodium ascorbate) on enhancing the activity of various antibacterial agents. Our quantitative proteomics analysis shows that non-lethal concentrations of vitamin C inhibit bacterial quorum sensing and other regulatory mechanisms underpinning biofilm development. As a result, the EPS biosynthesis in reduced, and especially the polysaccharide component of the matrix is depleted. Once the EPS content is reduced beyond a critical point, bacterial cells get fully exposed to the medium. At this stage, the cells are more susceptible to killing, either by vitamin C-induced oxidative stress as reported here, or by other antimicrobials or treatments.

Low Concentrations of Vitamin C Reduce the Synthesis of Extracellular Polymers and Destabilize Bacterial Biofilms

KAUST Repository

Pandit, Santosh; Ravikumar, Vaishnavi; Abdel-Haleem, Alyaa M.; Derouiche, Abderahmane; Mokkapati, V. R. S. S.; Sihlbom, Carina; Mineta, Katsuhiko; Gojobori, Takashi; Gao, Xin; Westerlund, Fredrik; Mijakovic, Ivan

2017-01-01

Extracellular polymeric substances (EPS) produced by bacteria form a matrix supporting the complex three-dimensional architecture of biofilms. This EPS matrix is primarily composed of polysaccharides, proteins and extracellular DNA. In addition to supporting the community structure, the EPS matrix protects bacterial biofilms from the environment. Specifically, it shields the bacterial cells inside the biofilm, by preventing antimicrobial agents from getting in contact with them, thereby reducing their killing effect. New strategies for disrupting the formation of the EPS matrix can therefore lead to a more efficient use of existing antimicrobials. Here we examined the mechanism of the known effect of vitamin C (sodium ascorbate) on enhancing the activity of various antibacterial agents. Our quantitative proteomics analysis shows that non-lethal concentrations of vitamin C inhibit bacterial quorum sensing and other regulatory mechanisms underpinning biofilm development. As a result, the EPS biosynthesis in reduced, and especially the polysaccharide component of the matrix is depleted. Once the EPS content is reduced beyond a critical point, bacterial cells get fully exposed to the medium. At this stage, the cells are more susceptible to killing, either by vitamin C-induced oxidative stress as reported here, or by other antimicrobials or treatments.

Repurposing metformin as a quorum sensing inhibitor in ...

African Journals Online (AJOL)

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

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

Directory of Open Access Journals (Sweden)

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.

Phage-mediated dispersal of biofilm and distribution of bacterial virulence genes is induced by quorum sensing.

Directory of Open Access Journals (Sweden)

Friederike S Rossmann

2015-02-01

Full Text Available The microbiome and the phage meta-genome within the human gut are influenced by antibiotic treatments. Identifying a novel mechanism, here we demonstrate that bacteria use the universal communication molecule AI-2 to induce virulence genes and transfer them via phage release. High concentrations (i.e. 100 μM of AI-2 promote dispersal of bacteria from already established biofilms, and is associated with release of phages capable of infecting other bacteria. Enterococcus faecalis V583ΔABC harbours 7 prophages in its genome, and a mutant deficient in one of these prophages (i.e. prophage 5 showed a greatly reduced dispersal of biofilm. Infection of a probiotic E. faecalis strain without lytic prophages with prophage 5 resulted in increased biofilm formation and also in biofilm dispersal upon induction with AI-2. Infection of the probiotic E. faecalis strain with phage-containing supernatants released through AI-2 from E. faecalis V583ΔABC resulted in a strong increase in pathogenicity of this strain. The polylysogenic probiotic strain was also more virulent in a mouse sepsis model and a rat endocarditis model. Both AI-2 and ciprofloxacin lead to phage release, indicating that conditions in the gastrointestinal tract of hospitalized patients treated with antibiotics might lead to distribution of virulence genes to apathogenic enterococci and possibly also to other commensals or even to beneficial probiotic strains.

How to desynchronize quorum-sensing networks

Science.gov (United States)

Russo, Giovanni

2017-04-01

In this paper we investigate how so-called quorum-sensing networks can be desynchronized. Such networks, which arise in many important application fields, such as systems biology, are characterized by the fact that direct communication between network nodes is superimposed to communication with a shared, environmental variable. In particular, we provide a new sufficient condition ensuring that the trajectories of these quorum-sensing networks diverge from their synchronous evolution. Then, we apply our result to study two applications.

39 CFR 6.6 - Quorum and voting.

Science.gov (United States)

2010-07-01

... 39 Postal Service 1 2010-07-01 2010-07-01 false Quorum and voting. 6.6 Section 6.6 Postal Service....6 Quorum and voting. As provided by 39 U.S.C. 205(c), the Board acts by resolution upon a majority... the compensation and benefits of the Postmaster General and Deputy Postmaster General, 39 U.S.C. 205(c...

Quorum quenching properties of Actinobacteria isolated from Malaysian tropical soils.

Science.gov (United States)

Devaraj, Kavimalar; Tan, Geok Yuan Annie; Chan, Kok-Gan

2017-08-01

In this study, a total of 147 soil actinobacterial strains were screened for their ability to inhibit response of Chromobacterium violaceum CV026 to short chain N-acyl homoserine lactone (AHL) which is a quorum sensing molecule. Of these, three actinobacterial strains showed positive for violacein inhibition. We further tested these strains for the inhibition of Pseudomonas aeruginosa PAO1 quorum sensing-regulated phenotypes, namely, swarming and pyocyanin production. The three strains were found to inhibit at least one of the quorum sensing-regulated phenotypes of PAO1. Phylogenetic analysis of the 16S rRNA gene sequences indicated that these strains belong to the genera Micromonospora, Rhodococcus and Streptomyces. This is the first report presenting quorum quenching activity by a species of the genus Micromonospora. Our data suggest that Actinobacteria may be a rich source of active compounds that can act against bacterial quorum sensing system.

Et Forsknings- og Udviklingsprojekt om Marjattas Skole- og Behandlingshjem

DEFF Research Database (Denmark)

Kristensen, Kasper Andreas

2011-01-01

Forskning og udviklingsrapport om rytmer og kunstneriske processer i Marjattas Rudolf Steiner inspirerede specialpædagogik......Forskning og udviklingsrapport om rytmer og kunstneriske processer i Marjattas Rudolf Steiner inspirerede specialpædagogik...

Facework og mikrosociologi

DEFF Research Database (Denmark)

Hougaard, Tina Thode

2014-01-01

Troværdighed og tillid er alfa og omega, når virksomheder, organisationer og myndigheder kommunikerer med brugerne, men hvordan skabes denne troværdighed i de sociale medier - og hvordan opretholdes den?......Troværdighed og tillid er alfa og omega, når virksomheder, organisationer og myndigheder kommunikerer med brugerne, men hvordan skabes denne troværdighed i de sociale medier - og hvordan opretholdes den?...

Quorum Sensing Disruption in Vibrio harveyi Bacteria by Clay Materials.

Science.gov (United States)

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

2018-01-10

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

Danskerne og besættelsen. Holdninger og meninger 1939-1945

DEFF Research Database (Denmark)

Roslyng-Jensen, Palle

På grundlag af dagbøger og rapporter fra danske og udenlandske myndigheder undersøges opinion og meningsdannelse under besættelsen med særlig henblik på synet på besættelsen og på krigen. Udviklingen i opinionen karakteriseres og struktureres i forhold til relevante opinionskategorier og graden a...

Biogenic synthesis of silver nanoparticles using Piper betle aqueous extract and evaluation of its anti-quorum sensing and antibiofilm potential against uropathogens with cytotoxic effects: an in vitro and in vivo approach.

Science.gov (United States)

Srinivasan, Ramanathan; Vigneshwari, Loganathan; Rajavel, Tamilselvam; Durgadevi, Ravindran; Kannappan, Arunachalam; Balamurugan, Krishnaswamy; Pandima Devi, Kasi; Veera Ravi, Arumugam

2018-04-01

Urinary tract infections are the utmost common bacterial infections caused by Proteus mirabilis, Pseudomonas aeruginosa, Escherichia coli, and Serratia marcescens. These uropathogens resist the action of several antibiotics due to their ability to form biofilms. Most of these bacterial pathogens use the quorum sensing (QS) machinery to co-ordinate their cells and regulate several virulence factors and biofilm formation. On the other hand, the anti-quorum sensing (anti-QS) and antibiofilm potential of silver nanoparticles have been well reported against certain bacterial pathogens, but to the best of our knowledge, no report is available against the pathogenicity of uropathogens in particular S. marcescens and P. mirabilis. Therefore, the present study is primarily focused on the anti-QS and antibiofilm potential of Piper betle-based synthesized silver nanoparticles (PbAgNPs) against S. marcescens and P. mirabilis. Initially, the silver nanoparticles were synthesized by the aqueous extract of P. betle and characterized by UV-absorbance spectroscopy, XRD, FT-IR, SEM, TEM, and DLS. The synthesized silver nanoparticles were assessed for their anti-QS activity and the obtained results revealed that the PbAgNPs inhibited the QS-mediated virulence factors such as prodigiosin, protease, biofilm formation, exopolysaccharides and hydrophobicity productions in uropathogens. The gene expression analysis divulged the downregulation of fimA, fimC, flhD, and bsmB genes in S. marcescens and flhB, flhD, and rsbA genes in P. mirabilis, respectively. The in vivo Caenorhabditis elegans assays revealed the non-toxic and anti-adherence efficiency of PbAgNPs. Furthermore, the non-toxic effect of PbAgNPs was also confirmed through peripheral blood mononuclear cells and normal lung epithelial cells. Therefore, the contemporary study demonstrates the use of PbAgNPs as a possible alternative toward conventional antibiotics in controlling QS and biofilm-related uropathogen infections.

Quorum Systems

DEFF Research Database (Denmark)

Wattenhofer, Roger; Förster, Klaus-Tycho

2016-01-01

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

Processer og procesledelse

DEFF Research Database (Denmark)

Madsen, Benedicte

Bogen udfolder, nuancerer og konkretiserer procesledelse ift. mentale, relationelle og organisatoriske processer. Eksempler på kapitel-overskrifter: Procesbegrebet, Rammesætning, Kontraktredskabet, Mødeledelse, Samtaler, Reflekterende positioner og processer, Konflikthåndtering og teamudvikling......, Invitation til det dialogiske rum - om at arbejde over og under stregen, og Mentale omstruktureringer....

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

DEFF Research Database (Denmark)

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

2009-01-01

R, and a quorum-sensing receptor agonist. Six top-ranking compounds, all recognized drugs, were identified and tested for quorum-sensing-inhibitory activity. Three compounds, salicylic acid, nifuroxazide, and chlorzoxazone, showed significant inhibition of quorum-sensing-regulated gene expression and related...

Extracts of Cordia gilletii de wild (Boraginaceae) quench the quorum sensing of Pseudomonas aeruginosa PAO1.

Science.gov (United States)

Okusa, Philippe N; Rasamiravaka, Tsiry; Vandeputte, Olivier; Stévigny, Caroline; Jaziri, Mondher El; Duez, Pierre

2014-01-01

The fight against infectious diseases and antimicrobial resistances needs the exploration of new active compounds with new proprieties like disrupting quorum sensing (QS) mechanisms, which is a cell-to-cell communication that regulates bacterial virulence factors. In this work, leaves and root barks extracts of a Congolese medicinal plant, Cordia gilletii, were investigated for their effect on the production of Pseudomonas aeruginosa major virulence factors regulated by QS. The effect of C. gilletii extracts on virulence factors of P. aeruginosa PAO1 was studied by the evaluation of the production of pyocyanine, elastase and biofilm; and by the measurement of the expression of QS-related genes. The dichloromethane extract from root barks was found to quench the production of pyocyanin, a QS-dependent virulence factor in P. aeruginosa PAO1. Moreover, this extract specifically inhibits the expression of several QS-regulated genes (i.e. lasB, rhlA, lasI, lasR, rhlI, and rhlR) and reduces biofilm formation by PAO1. This study contributes to explain the efficacy of C. gilletii in the traditional treatment of infectious diseases caused by P. aeruginosa.

Extracts of Cordia gilletii de wild (Boraginaceae) quench the quorum sensing of Pseudomonas aeruginosa PAO1

Science.gov (United States)

Okusa, Philippe N.; Rasamiravaka, Tsiry; Vandeputte, Olivier; Stévigny, Caroline; Jaziri, Mondher El; Duez, Pierre

2014-01-01

Aim: The fight against infectious diseases and antimicrobial resistances needs the exploration of new active compounds with new proprieties like disrupting quorum sensing (QS) mechanisms, which is a cell-to-cell communication that regulates bacterial virulence factors. In this work, leaves and root barks extracts of a Congolese medicinal plant, Cordia gilletii, were investigated for their effect on the production of Pseudomonas aeruginosa major virulence factors regulated by QS. Materials and Methods: The effect of C. gilletii extracts on virulence factors of P. aeruginosa PAO1 was studied by the evaluation of the production of pyocyanine, elastase and biofilm; and by the measurement of the expression of QS-related genes. Results: The dichloromethane extract from root barks was found to quench the production of pyocyanin, a QS-dependent virulence factor in P. aeruginosa PAO1. Moreover, this extract specifically inhibits the expression of several QS-regulated genes (i.e. lasB, rhlA, lasI, lasR, rhlI, and rhlR) and reduces biofilm formation by PAO1. Conclusion: This study contributes to explain the efficacy of C. gilletii in the traditional treatment of infectious diseases caused by P. aeruginosa. PMID:26401363

Magt og anerkendelse

DEFF Research Database (Denmark)

Olesen, Carsten Frank

2014-01-01

Kapitlet omhandler dilemmaer i relation til døgnanbringelse af et barn, og samarbejdet/modarbejdet mellem familie og professionelle/system, hvor magt og anerkendelse er de analytiske nøglebegreber. Barnets reform og efterfølgende lovgivning til og med 2013 inddrages i relation, og søger at illust...

The possible role of bacterial signal molecules N-acyl homoserine lactones in the formation of diatom-biofilm (Cylindrotheca sp.)

International Nuclear Information System (INIS)

Yang, Cuiyun; Fang, Shengtao; Chen, Dehui; Wang, Jianhua; Liu, Fanghua; Xia, Chuanhai

2016-01-01

Bacterial quorum sensing signal molecules N-acyl homoserine lactones (AHLs) (C10-HSL, 3-OXO-C10-HSL and 3-OH-C10-HSL) as possible chemical cues were employed to investigate the role in the formation of fouling diatom-biofilm (Cylindrotheca sp.). Results showed that AHLs promoted Chlorophyll a (Chl.a) and extracellular polymeric substance (EPS) contents in the diatom-biofilm. In the presence of AHLs-inhibitor 3, 4-Dibromo-2(5)H-furanone, which was used to avoid the possible interference of AHLs from bacteria, AHLs also increased the Chl.a and EPS contents. Scanning electron microscope and confocal laser scanning microscope analysis further demonstrated that AHLs promoted the formation of the diatom-biofilm. Non-invasive micro-test technique showed that AHLs promoted Ca 2+ efflux in Cylindrotheca sp., which implied that Ca 2+ might be correlated with AHLs-induced positive effect on the formation of diatom-biofilm. This study provides direct evidences that AHLs play an important role in developing the diatom-biofilm and AHLs-inhibitors might be promising active agents in marine antifouling. - Highlights: •AHLs effectively increase Chl.a and EPS contents in diatom-biofilm. •SEM and CLSM further demonstrate that AHLs promote the formation of diatom-biofilm. •AHLs trigger algal cellular Ca 2+ efflux. •AHLs-inhibitors might be promising active agents in marine antifouling.

Melodrama, temporalitet og genkendelse: amerikansk og russisk stumfilm.

Directory of Open Access Journals (Sweden)

Mary Ann Doane

1990-08-01

Full Text Available Mary Ann Doanes artikel om det tidlige amerikanske og russiske me- lodrama fra stumfilmsperioden kan måske synes at have et meget eksotisk tema her i 1990. Men hun beskæftiger sig for det første med en genre, melodramaet, som indtager en enestående central plads i både filmens og TV-mediets historie, og hvis historiske rødder derfor har stor aktualitet. Desuden kaster hun et kønsteoretisk aspekt ind- over genre-diskussionen i sin beskæftigelse med sammenhængen mellem kønsroller på lærredet og i den virkelighed, som publikum og filmene befandt sig i. Endelig rummer hendes artikel en central pointe i en generel genre- diskussion: genrerne er i høj grad bundet til deres sociale, kulturelle og historiske produktionssammenhæng - de er ikke ontologiske, over- historiske skabeloner. Det amerikanske og det russiske melodrama er to meget forskellige udgaver af en basal, melodramatiske oplevel- sesmåde. (Artiklen er oversat af Ib Bondebjerg og er i sin engelske udgave trykt i "East-West Film Journal", vol.4, no.2, juni 1990.

Erving Goffman og Axel Honneth - Anerkendelse og krænkelse

OpenAIRE

Hansen, Annemette E

2006-01-01

En kombination af Erving Goffmans teorier om stigma og rollespil og Axel Honneths anerkendelsesteori En kombination af Erving Goffmans teorier om stigma og rollespil og Axel Honneths anerkendelsesteori

Videnarbejde og stress

DEFF Research Database (Denmark)

Buch, Anders; Andersen, Vibeke; Sørensen, Ole Henning

. Videnarbejde kan for den enkelte være vejen til selvrealisering og begejstring, men rummer også i sig kimen til stress og udbrændthed. Og det er netop i spændingsfeltet - i kampen - mellem begejstring og belastning, at bogen ser stress i det moderne arbejdsliv, som en uoverensstemmelse mellem ydre krav og...

Professionel kompetence og uddannelse

DEFF Research Database (Denmark)

Hedegaard, Karen Marie

Specialet behandler forholdet mellem professionel kompetence og uddannelse gennem en undersøgelse og diskussion af teorier og forskning om professionsbegrebet i sociologien historisk og aktuelt, bl.a. Talcott Parsons, MaxWeber og Thomas Mathiesen, og diskuterer forskellige forståelser af professi......Specialet behandler forholdet mellem professionel kompetence og uddannelse gennem en undersøgelse og diskussion af teorier og forskning om professionsbegrebet i sociologien historisk og aktuelt, bl.a. Talcott Parsons, MaxWeber og Thomas Mathiesen, og diskuterer forskellige forståelser af...

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

DEFF Research Database (Denmark)

Høyland-Kroghsbo, Nina Molin

in the bacterial cell-cell communication field is why E. coli harbors SdiA, an orphan quorum sensing receptor that is activated in response to AHL quorum sensing molecules produced by other Gram-negative species. The overall aim of this PhD thesis was to investigate to what degree AHL quorum sensing signals...... are exploited by E. coli to increase its chances of surviving potential environmental threats. This thesis uncovers the first quorum sensing-regulated bacteriophage defense mechanism, which serves to protect E. coli against infection by the bacteriophage viruses λ and χ. Investigating the regulatory mechanism...... underlying the quorum sensing regulated defense mechanism, led to the discovery that AHL activates expression of cnu, encoding an Hha-family protein that interacts with the global regulatory protein H-NS, and potentially modifies its functions. Inspired by the discovery that AHL protects E. coli from...

Biomimicry of quorum sensing using bacterial lifecycle model.

Science.gov (United States)

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

2013-01-01

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

Universitetet er også for pædagoger og sygeplejersker

DEFF Research Database (Denmark)

Larsen, Kristian

2014-01-01

-teoretiske opgaveforløb, er det en fordel at have kontakter til f.eks. institutioner (skoler, børnehaver, hospitaler etc.), når der skal foretages observationsstudier, interview med videre. Professionsbachelorerne vil ofte have let ved at gennemføre f.eks. observationer og interview, der kræver direkte kontakt med...... liv, institutionerne og professionerne indefra, og samtidig formår at objektivere og kigge på det kendte udefra. De har mødt hjemløshed som lugt, afsavn, smerte, kulde og afmagt, og teorier bliver nu relevante som redskaber til at beskrive, forstå og forklare fænomenerne. Vi påberåber os at være et...... videnssamfund, at alle er entreprenører i eget liv, at vi skal være livslangt under uddannelse. At kreativitet, mobilitet og udvikling er væsentligt for individ og samfund. Der er godt med plads til professionsbachelorerne på universiteterne, og de har masser at komme med, men det går ikke af sig selv – det...

Teamarbejde og samspillet mellem medarbejdere og organisation

DEFF Research Database (Denmark)

Jeppesen, Hans Jeppe; Jønsson, Thomas

2008-01-01

Gennem det seneste årti har brug af teams som en måde at organisere arbejdet på været i hastig fremmarch. Det er baggrunden for forskningsprojektet ”Team-organiseringens betydning for participation og organisatoriske relationer”, der er et multiple case-studie af seks organisationers brug af...... teamwork. Bag projektet står professor Hans Jeppe Jeppesen, cand.psych. og ph.d. Thomas Rasmussen samt adjunkt Thomas Jønsson. I denne klumme gives en forskningsbaseret introduktion til teamarbejdet og dets betydning for samspillet mellem medarbejdere og organisation. Med udgangspunkt i egen forskning...

Inhibition of quorum sensing-mediated virulence in Serratia marcescens by Bacillus subtilis R-18.

Science.gov (United States)

Devi, Kannan Rama; Srinivasan, Subramaniyan; Ravi, Arumugam Veera

2018-04-13

Serratia marcescens is an opportunistic human pathogen causing various nosocomial infections, most importantly urinary tract infections (UTIs). It exhibits increased resistance towards the conventional antibiotics. This study was aimed to evaluate the anti-virulence effect of a rhizosphere soil bacterium Bacillus subtilis strain R-18 against the uropathogen S. marcescens. First, the bacterial cell-free culture supernatant (CFCS) of B. subtilis strain R-18 was evaluated for its quorum sensing inhibitory (QSI) potential against biomarker strain Chromobacterium violaceum and the test pathogen S. marcescens. The B. subtilis R-18 CFCS effectively inhibited the quorum sensing (QS)-mediated violacein pigment production in C. violaceum and prodigiosin pigment production in S. marcescens. Furthermore, B. subtilis R-18 CFCS was successively extracted with different solvent systems. Of these solvents, B. subtilis R-18 petroleum ether (PE) extract showed inhibition in biofilm formation, protease, lipase, and hemolysin productions in S. marcescens. Fourier transform infrared spectroscopic (FT-IR) analysis revealed the alterations in the cellular components of bacterial cell pellets obtained from B. subtilis R-18 PE extract treated and untreated S. marcescens. The differential gene expression study further validated the downregulation of virulence-associated genes. Characterization of the active principle in B. subtilis R-18 PE extract by gas chromatography-mass spectrometry (GC-MS) analysis showed the presence of multiple compounds with therapeutic values, which could possibly reduce the QS-dependent phenotypes in S. marcescens. Copyright © 2018. Published by Elsevier Ltd.

The physical basis of bacterial quorum communication

CERN Document Server

2015-01-01

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

Quorum sensing in gram-negative bacteria

DEFF Research Database (Denmark)

Wu, H.; Song, Z.J.; Høiby, N.

2004-01-01

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

Quorum Sensing Regulation in Aeromonas hydrophila

DEFF Research Database (Denmark)

Garde, Christian; Bjarnsholt, Thomas; Givskov, Michael

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 Escheri......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...

Frukt og grønt i mat og helsefaget. En casestudie

OpenAIRE

Kristoffersen, Mirjam

2016-01-01

Masteroppgave i fysisk aktivitet og kosthold i et skolemiljø Bakgrunn og hensikt: Studier viser at barn og unge har et for lavt inntak av frukt og grønt i forhold til hva som er anbefalt. Skolen er en arena hvor en kan nå mange med kunnskap om hvorfor en bør spise mer frukt og grønnsaker. Spesielt faget mat og helse kan bidra til å belyse temaet gjennom undervisningen. Hensikten med denne studien er å bidra med kunnskap om hva som blir brukt av frukt og grønnsaker og hvordan det blir benyt...

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

Directory of Open Access Journals (Sweden)

Kok-Gan Chan

2013-05-01

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

Quorum sensing negatively regulates chitinase in Vibrio harveyi.

Science.gov (United States)

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

2010-02-01

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

Residence of Streptococcus pneumoniae and Moraxella catarrhalis within polymicrobial biofilm promotes antibiotic resistance and bacterial persistence in vivo.

Science.gov (United States)

Perez, Antonia C; Pang, Bing; King, Lauren B; Tan, Li; Murrah, Kyle A; Reimche, Jennifer L; Wren, John T; Richardson, Stephen H; Ghandi, Uma; Swords, W Edward

2014-04-01

Otitis media (OM) is an extremely common pediatric ailment caused by opportunists that reside within the nasopharynx. Inflammation within the upper airway can promote ascension of these opportunists into the middle ear chamber. OM can be chronic/recurrent in nature, and a wealth of data indicates that in these cases, the bacteria persist within biofilms. Epidemiological data demonstrate that most cases of OM are polymicrobial, which may have significant impact on antibiotic resistance. In this study, we used in vitro biofilm assays and rodent infection models to examine the impact of polymicrobial infection with Moraxella catarrhalis and Streptococcus pneumoniae (pneumococcus) on biofilm resistance to antibiotic treatment and persistence in vivo. Consistent with prior work, M. catarrhalis conferred beta-lactamase-dependent passive protection from beta-lactam killing to pneumococci within polymicrobial biofilms. Moreover, pneumococci increased resistance of M. catarrhalis to macrolide killing in polymicrobial biofilms. However, pneumococci increased colonization in vivo by M. catarrhalis in a quorum signal-dependent manner. We also found that co-infection with M. catarrhalis affects middle ear ascension of pneumococci in both mice and chinchillas. Therefore, we conclude that residence of M. catarrhalis and pneumococci within the same biofilm community significantly impacts resistance to antibiotic treatment and bacterial persistence in vivo. © 2014 Federation of European Microbiological Societies. Published by John Wiley & Sons Ltd. All rights reserved.

Udfordringerne fra globalisering og migration:Interaktion mellem kønslighed og kulturel mangfoldighed

OpenAIRE

Siim, Birte

2008-01-01

Globalisering og migration har forøget mamgfoldighed og uligheder inden for og mellem nationerne og har skabt nye problemer for offentlige politikker og nye behov for at regulere politiske og socio-økonomiske problemer nationalt og globalt. Artiklen behandler disse udfordringer med særlig fokus på samspillet mellem køn og mangfoldighed. Det dobbelte formål er først at nyvurdere begreber om medborgerskab, nationalitet og tilhørsforhold i lyset af lokale og globale relationer og multikulturalis...

GI og GISc

DEFF Research Database (Denmark)

Brande-Lavridsen, Hanne

Udviklingen inden for kort- og geodataverdenen ligner udviklingen inden for alle andre erhverv, hvor globaliseringen spiller en stor rolle. Her kan man vælge de negative tilgang og se udviklingen som uoverskuelig og foruroligende. Eller man kan vælge en positiv og se udviklingen som udfordrende og...

Web-nyheder og tv-nyheder på DR og TV2

DEFF Research Database (Denmark)

Bang, Jørgen

2008-01-01

Artiklen undersøger forholdet med web-nyheder og tv-nyheder i danske public service (DR1 og TV2). Ud fra analyser af web-nyhederne og og tv-nyhederne i uge 4 og 17 sammenholdt med analyser af net-brugerne og tv-seerene i samme tidsrum påpeger artiklen at net-brugerne på de to stationer kun udgør ca...

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

Science.gov (United States)

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

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

Somatisk embryogense og kryopræservering af eg og bøg

DEFF Research Database (Denmark)

MMH Kristensen, Michel; Find, Jens; Krogstrup, Peter

Somatisk embryogenese og kryopræservering af eg og bøg Traditionel vegetativ formering af eg og bøg er vanskeligt, dyrt og har ingen større praktisk anvendelse i skovbruget. Opbevaring af agern og bog i frøbanker erligeledesproblematiskidetspiringsevnenfalderdramatiskalleredeiløbetafdetoførsteåre......Somatisk embryogenese og kryopræservering af eg og bøg Traditionel vegetativ formering af eg og bøg er vanskeligt, dyrt og har ingen større praktisk anvendelse i skovbruget. Opbevaring af agern og bog i frøbanker...... holdbarheden er flere hundrede år. Arbejdet med eg og bøg er en del af et større projekt, Videreudvikling af bioteknologiske metoder, med henblik på forædling og opbevaring af plantegenetiske ressourcer for skovtræer i Danmark 2003- 2006. Det overordnede formål med projektet var at udvikle metoder til...

PH og modernismen

DEFF Research Database (Denmark)

Ahnfeldt-Mollerup, Merete

2012-01-01

Artiklen kaster et kritisk blik på Poul Henningsens samfundsanalyse og dennes sammenhæng med hans design. PH ses i en bredere national og international sammenhæng. Diskussion af designmetoder, æstetik og Bauhaus.......Artiklen kaster et kritisk blik på Poul Henningsens samfundsanalyse og dennes sammenhæng med hans design. PH ses i en bredere national og international sammenhæng. Diskussion af designmetoder, æstetik og Bauhaus....

Investigation of N-acyl homoserine lactone (AHL) molecule production in Gram-negative bacteria isolated from cooling tower water and biofilm samples.

Science.gov (United States)

Haslan, Ezgi; Kimiran-Erdem, Ayten

2013-09-01

In this study, 99 Gram-negative rod bacteria were isolated from cooling tower water, and biofilm samples were examined for cell-to-cell signaling systems, N-acyl homoserine lactone (AHL) signal molecule types, and biofilm formation capacity. Four of 39 (10 %) strains isolated from water samples and 14 of 60 (23 %) strains isolated from biofilm samples were found to be producing a variety of AHL signal molecules. It was determined that the AHL signal molecule production ability and the biofilm formation capacity of sessile bacteria is higher than planktonic bacteria, and there was a statistically significant difference between the AHL signal molecule production of these two groups (p cooling tower water and biofilm samples produced different types of AHL signal molecules and that there were different types of AHL signal molecules in an AHL extract of bacteria. In the present study, it was observed that different isolates of the same strains did not produce the same AHLs or did not produce AHL molecules, and bacteria known as AHL producers did not produce AHL. These findings suggest that detection of signal molecules in bacteria isolated from cooling towers may contribute to prevention of biofilm formation, elimination of communication among bacteria in water systems, and blockage of quorum-sensing controlled virulence of these bacteria.

Meningsskabelse og meningstab

DEFF Research Database (Denmark)

Olsén, Peter; Hagedorn-Rasmussen, Peter

2008-01-01

Meningsfulde forandringsprocesser i arbejdslivet kræver, at der skabes rum til at fokusere på både indhold og betingelser i arbejdet. At man mestrer arbejdet, og at arbejde og produkt har kvalitet og nytte, er omdrejningspunkt i en positiv oplevelse af arbejdet - og drivkraft i ny meningsskabelse...

Pigebilleder og drengestreger

DEFF Research Database (Denmark)

Nielsen, Anne Maj

Med udgangspunkt i børns tegninger gøres der i bogen rede for børns billedsmæssige udvikling og billedsocialisation, for personlige, lokale og kulturelle betydninger i børns billeder i form af forskellige symbollag samt for ligheder og forskelle i piger og drenges billeder og billedsocialisation....

Farestrategier og trampolinleg

DEFF Research Database (Denmark)

Karoff, Helle Skovbjerg

Vild og farlig leg på havetrampoliner udfordrer børns sikkerhed og tryghed og er samtidig både udviklende og udfordrende. Børn kan lære at håndtere risici, når de leger på trampolinen. Helle Skovbjerg Karoff er adjunkt ved Aalborg Universitet/København og knyttet til forskningslaboratoriet for IT...

Exploring the Anti-quorum Sensing and Antibiofilm Efficacy of Phytol against Serratia marcescens Associated Acute Pyelonephritis Infection in Wistar Rats

Science.gov (United States)

Srinivasan, Ramanathan; Mohankumar, Ramar; Kannappan, Arunachalam; Karthick Raja, Veeramani; Archunan, Govindaraju; Karutha Pandian, Shunmugiah; Ruckmani, Kandasamy; Veera Ravi, Arumugam

2017-01-01

Quorum Sensing (QS) mechanism, a bacterial density-dependent gene expression system, governs the Serratia marcescens pathogenesis through the production of virulence factors and biofilm formation. The present study demonstrates the anti-quorum sensing (anti-QS), antibiofilm potential and in vivo protective effect of phytol, a diterpene alcohol broadly utilized as food additive and in therapeutics fields. In vitro treatment of phytol (5 and 10 μg/ml) showed decreasing level of biofilm formation, lipase and hemolysin production in S. marcescens compared to their respective controls. More, microscopic analyses confirmed the antibiofilm potential of phytol. The biofilm related phenomenons such as swarming motility and exopolysccharide productions were also inhibited by phytol. Furthermore, the real-time analysis elucidated the molecular mechanism of phytol which showed downregulation of fimA, fimC, flhC, flhD, bsmB, pigP, and shlA gene expressions. On the other hand, the in vivo rescue effect of phytol was assessed against S. marcescens associated acute pyelonephritis in Wistar rat. Compared to the infected and vehicle controls, the phytol treated groups (100 and 200 mg/kg) showed decreased level of bacterial counts in kidney, bladder tissues and urine samples on the 5th post infection day. As well, the phytol treatment showed reduced level of virulence enzymes such as lipase and protease productions compared to the infected and vehicle controls. Further, the infected and vehicle controls showed increasing level of inflammatory markers such as malondialdehyde (MDA), nitric oxide (NO) and myeloperoxidase (MPO) productions. In contrast, the phytol treatment showed decreasing level of inflammatory markers. In histopathology, the uninfected animal showed normal kidney and bladder structure, wherein, the infected animals showed extensive infiltration of neutrophils in kidney and bladder tissues. In contrast, the phytol treatment showed normal kidney and bladder tissues

Case03: BIM hos driftsherre og byg- og driftsherrerådgiver

DEFF Research Database (Denmark)

Vestergaard, Flemming; Karlshøj, Jan; Hauch, Peter

Casen repræsenterer et koncept, hvor både byg- og driftsherren og en byg- og driftsherrerådgiver er aktive i anvendelsen af en BIM-orienteret arbejdsmetode og modelbaserede værktøjer, som omfatter følgende aktiviteter: Design, Projektering, Udbud/tilbud, produktionsforberedelse, Udførelse og Drift...

Islam og Islamisme

DEFF Research Database (Denmark)

Simonsen, Jørgen Bæk

2010-01-01

En præsentation og en kritik af nyere international forskning i islam og islamisme Udgivelsesdato: Februar......En præsentation og en kritik af nyere international forskning i islam og islamisme Udgivelsesdato: Februar...

Kultur og sundhed

DEFF Research Database (Denmark)

kunst- og kulturaktiviteter benyttes på sundhedsområdet? Antologien "Kultur og sundhed" præsenterer en bred platform af forskellige praksisser, bidrager til vidensgrundlaget og diskursen i feltet og skaber inspiration til fremtidige, sundhedsfremmende tilbud i Danmark ved at afsøge muligheder i...... krydsfeltet mellem sundhed, trivsel og kunst- og kulturaktiviteter. Bogen er opdelt i tre dele hvor den første del fokuserer på en række af de forståelser, begreber, tilgange, vidensgrundlag og mekanismer der er i spil i det tværfaglige felt. Bogens anden del er koncentreret om en bred præsentation af feltets...

Etik og kommunikation

Directory of Open Access Journals (Sweden)

Uwe Geist

1996-09-01

Full Text Available "Det er ikke helt tilfældigt, at etik og PR ekspanderer voldsomt i 80´ernes Europa, og PR nærmer sig etikken. Begge dele er affødt af dybtgående forandringer i livsbetingelserne, som er beskrevet mange steder. Forurening, globalisering, polarisering mellem rig og fattig, genmanipulation og informationseksplosion er de gennemgå- ende motiver og et truende kaos det gennemgående tema". Det er på den baggrund, at Uwe Geist, der er ansat på Roskilde Universitets- centers Dansk/PR-uddannelse, i artiklen prøver at komme bag om et modeord, som i de senere år har hærget både samfundet i almindelig- hed og PR-branchen i særdeleshed. I artiklen sætter han først begre- bet "etik" op imod beslægtede begreber som "moral", "høflighed" og "ret". Dernæst diskuterer han etikkens nødvendighed, på den ene side inden for Habermas´ teori om kommunikativ handlen og diskurs, livs- verden og systemverden, hvor etik ikke handler om faste normer for godt og ondt, men om gensidigheden som grundnorm; på den anden side inden for Luhmanns systemteori, hvor gensidighed ganske vist er funktions- og effektivitetsorienteret, men ikke kan undvære mekanis- men og ressourcen "tillid". Fordi artiklen omhyggeligt forklarer de cen- trale begreber, den diskuterer, kan den både fungere begrebsintrodu- cerende for læsere uden omfattende forudsætninger på feltet, og be- grebsafklarende for mere indviede læsere.

Viden, virkning og virke

DEFF Research Database (Denmark)

traditioner og vante tænkemåder. Relationerne mellem politiske og administrative beslutningstagere, sundhedsprofessionelle og patienter/borgere og deres foreninger forandres, og viden, politik og sundhed mødes og brydes på nye måder.   Har vi bevæget os fra en velfærdsstat til en konkurrencestat? Hvad betyder...

Flow og fordybelse

DEFF Research Database (Denmark)

Andersen, Frans Ørsted

2010-01-01

Artiklen handler om flow og fordybelse i et nyt tværfagligt / naturfagligt undervisningskoncept, "Overvågningens dilemma", til brug i folkeskolens 7.-9.kl. og på gymnasiale uddannelser. Konceptet sætter fokus på den overvågning der foregår og er mulig i nutidens IT og hi-tec samfund og der arbejd...

[Formation of the Pseudomonas aeruginosa PAO1 biofilms in the presence of hydrogen peroxide; the effect of the AiiA gene].

Science.gov (United States)

Pliuta, V A; Andreenko, Iu V; Kuznetsov, A E; Khmel', I A

2013-01-01

In the natural ecosystems, most bacteria exist as specifically organized biofilms attached to various surfaces; the biofilms have a complex architecture and are surrounded by an exopolymeric matrix. The bacteria in the biofilms are extremely resistant to antibacterial agents. The ability of the pathogenic bacteria to produce biofilms causes serious problems in medicine. Therefore, the study of the action of different compounds with antibacterial activity is of great interest. In this work, we studied the effect of the hydrogen peroxide (H2O2) on the formation of biofilms by Pseudomonas aeruginosa PAO1. It was shown that H2O2 in concentrations that do not suppress bacterial growth (or suppress it only weakly) stimulates the formation of the biofilms. At higher concentrations, H2O2 inhibits the formation of the biofilms. In order to determine if the stimulation of the biofilm formation depends on Quorum Sensing (QS) regulation, the plasmid pME6863 containing the heterologous gene aiiA encoding the N-acyl-homoserine lactonase AiiA was introduced into P. aeruginosa PAO1. The synthesis by cells of this enzyme degrading N-acyl-homoserine lactones (AHL), signaling molecules of the QS systems, led to the absence of the stimulation of the biofilm formation by the action of H2O2. This fact indicates that the stimulation of the biofilm formation in the presence of H2O2 depends on the functioning of the QS systems of the gene expression regulation of P. aeruginosa PAO1.

Searching the ASRS Database Using QUORUM Keyword Search, Phrase Search, Phrase Generation, and Phrase Discovery

Science.gov (United States)

McGreevy, Michael W.; Connors, Mary M. (Technical Monitor)

2001-01-01

To support Search Requests and Quick Responses at the Aviation Safety Reporting System (ASRS), four new QUORUM methods have been developed: keyword search, phrase search, phrase generation, and phrase discovery. These methods build upon the core QUORUM methods of text analysis, modeling, and relevance-ranking. QUORUM keyword search retrieves ASRS incident narratives that contain one or more user-specified keywords in typical or selected contexts, and ranks the narratives on their relevance to the keywords in context. QUORUM phrase search retrieves narratives that contain one or more user-specified phrases, and ranks the narratives on their relevance to the phrases. QUORUM phrase generation produces a list of phrases from the ASRS database that contain a user-specified word or phrase. QUORUM phrase discovery finds phrases that are related to topics of interest. Phrase generation and phrase discovery are particularly useful for finding query phrases for input to QUORUM phrase search. The presentation of the new QUORUM methods includes: a brief review of the underlying core QUORUM methods; an overview of the new methods; numerous, concrete examples of ASRS database searches using the new methods; discussion of related methods; and, in the appendices, detailed descriptions of the new methods.

[Involvement of the global regulators GrrS, RpoS, and SplIR in formation of biofilms in Serratia plymuthica].

Science.gov (United States)

Zaĭtseva, Iu V; Voloshina, P V; Liu, X; Ovadis, M I; Berg, G; Chernin, L S; Khmel', I A

2010-05-01

Most bacteria exist in the natural environment as biofilms, multicellular communities attached to hard surfaces. Biofilms have a characteristic architecture and are enclosed in the exopolymer matrix. Bacterial cells in biofilms are extremely resistant to antibacterial factors. It was shown in this work that the GrrA/GrrS system of global regulators of gene expression and the sigma S subunit of RNA polymerase (RpoS) play a significant role in positive regulation of biofilm formation in the rhizospheric bacterium Serratia plymuthica IC1270. Inactivation of grrS and rpoS genes resulted in an up to six-to-sevenfold and four-to-fivefold reduction in biofilm formation, respectively. Mutations in the grrS gene decreased the capacity of the bacterium for swarming motility. The splIR Quorum Sensing (QS) system was shown to negatively influence the biofilm formation. Transfer of the recombinant plasmid containing cloned genes splI/splR of S. plymuthica HRO-C48 into S. plymuthica IC1270 cells led to a twofold decrease of their ability to form biofilms. Inactivation of the splI gene coding for the synthase of N-acyl-homoserine lactones in S. plymuthica HRO-C48 resulted in a 2-2.5-fold increase in the level of biofilm formation, whereas the inclusion of plasmid carrying the cloned splI/splR genes into these mutant cells restored the biofilm formation to the normal level. The results obtained demonstrate that the formation of biofilms in S. plymuthica is positively regulated by the GrrA/GrrS and RpoS global regulators and is negatively regulated by the SplIR QS system.

Sekularisering og religion

DEFF Research Database (Denmark)

Andersen, Kirsten Margrethe

2015-01-01

Sammendrag: Sekularisering og religion: En studie i fortællingens nøglerolle i folkeskolens religionsundervisning Kirsten M. Andersen Ph.d. afhandling, indleveret ved institut for Uddannelse og Pædagogik, Aarhus Universitet, d. 23. oktober 2014 Indledning Afhandlingens sigte er at bidrage til en...... fortsat udvikling af religionsundervisningen i skolen ud fra en almen pædagogisk interesse. Skolen har sit eget formål og derfor må religion ombrydes, så den gøres pædagogisk. Religionshistorisk, religionssociologisk og antropologisk opfattes religion og kultur i et kontinuum. Det betyder, at religion...... fænomenologiske overvejelser over, hvorfor filosofien har behov for at formulere en religionshermeneutik med henblik på en almen pædagogisk begrundelse for skolens religionsundervisning. I Del: Kap. 2: Afhandlingen indledes med at indkredse og definere både religion og sekularisering som kulturelle og kollektive...

The effect of environmental conditions on biofilm formation of Burkholderia pseudomallei clinical isolates.

Directory of Open Access Journals (Sweden)

Nur Siti K Ramli

Full Text Available Burkholderia pseudomallei, a Gram-negative saprophytic bacterium, is the causative agent of the potentially fatal melioidosis disease in humans. In this study, environmental parameters including temperature, nutrient content, pH and the presence of glucose were shown to play a role in in vitro biofilm formation by 28 B. pseudomallei clinical isolates, including four isolates with large colony variants (LCVs and small colony variants (SCVs morphotypes. Enhanced biofilm formation was observed when the isolates were tested in LB medium, at 30 °C, at pH 7.2, and in the presence of as little as 2 mM glucose respectively. It was also shown that all SVCs displayed significantly greater capacity to form biofilms than the corresponding LCVs when cultured in LB at 37 °C. In addition, octanoyl-homoserine lactone (C(8-HSL, a quorum sensing molecule, was identified by mass spectrometry analysis in bacterial isolates referred to as LCV CTH, LCV VIT, SCV TOM, SCV CTH, 1 and 3, and the presence of other AHL's with higher masses; decanoyl-homoserine lactone (C(10-HSL and dodecanoyl-homoserine lactone (C(12-HSL were also found in all tested strain in this study. Last but not least, we had successfully acquired two Bacillus sp. soil isolates, termed KW and SA respectively, which possessed strong AHLs degradation activity. Biofilm formation of B. pseudomallei isolates was significantly decreased after treated with culture supernatants of KW and SA strains, demonstrating that AHLs may play a role in B. pseudomallei biofilm formation.

Praksisteori og arbejdslivsforskning

DEFF Research Database (Denmark)

Buch, Anders

2017-01-01

Praksisteori er en lang og bred human- og socialvidenskabelig tradition, der forsøger at forstå mennesker, arbejde og samfund med udgangspunkt i aktivitet og handling. I denne artikel gøres der rede for praksisteoriens grundlæggende antagelser og begreber. Artiklen fokuserer på, hvordan nyere...... praksisteori – her Theodore Schatzkis teori om socialt liv – udvikler begreber til at forstå, hvordan det sociale liv er organiseret igennem praksisser, og hvordan normativitet i praksisser bidrager til at bestemme handlinger. Der argumenteres for, at den praksisteoretiske tilgang kan tilbyde...

Portfolio, refleksion og feedback

DEFF Research Database (Denmark)

Hansen, Jens Jørgen; Qvortrup, Ane; Christensen, Inger-Marie F.

2017-01-01

Denne leder definerer indledningsvist begrebet portfolio og gør rede for anvendelsesmuligheder i en uddannelseskontekst. Dernæst behandles portfoliometodens kvalitet og effekt for læring og undervisning og de centrale begreber refleksion, progression og feedback præsenteres og diskuteres. Herefter...

Curcumin Quantum Dots Mediated Degradation of Bacterial Biofilms

Directory of Open Access Journals (Sweden)

Ashish K. Singh

2017-08-01

Full Text Available Bacterial biofilm has been reported to be associated with more than 80% of bacterial infections. Curcumin, a hydrophobic polyphenol compound, has anti-quorum sensing activity apart from having antimicrobial action. However, its use is limited by its poor aqueous solubility and rapid degradation. In this study, we attempted to prepare quantum dots of the drug curcumin in order to achieve enhanced solubility and stability and investigated for its antimicrobial and antibiofilm activity. We utilized a newer two-step bottom up wet milling approach to prepare Curcumin Quantum Dots (CurQDs using acetone as a primary solvent. Minimum inhibitory concentration against select Gram-positive and Gram-negative bacteria was performed. The antibiofilm assay was performed at first using 96-well tissue culture plate and subsequently validated by Confocal Laser Scanning Microscopy. Further, biofilm matrix protein was isolated using formaldehyde sludge and TCA/Acetone precipitation method. Protein extracted was incubated with varying concentration of CurQDs for 4 h and was subjected to SDS–PAGE. Molecular docking study was performed to observe interaction between curcumin and phenol soluble modulins as well as curli proteins. The biophysical evidences obtained from TEM, SEM, UV-VIS, fluorescence, Raman spectroscopy, and zeta potential analysis confirmed the formation of curcumin quantum dots with increased stability and solubility. The MICs of curcumin quantum dots, as observed against both select gram positive and negative bacterial isolates, was observed to be significantly lower than native curcumin particles. On TCP assay, Curcumin observed to be having antibiofilm as well as biofilm degrading activity. Results of SDS–PAGE and molecular docking have shown interaction between biofilm matrix proteins and curcumin. The results indicate that aqueous solubility and stability of Curcumin can be achieved by preparing its quantum dots. The study also demonstrates

Quorum sensing alters the microbial community of electrode-respiring bacteria and hydrogen scavengers toward improving hydrogen yield in microbial electrolysis cells

International Nuclear Information System (INIS)

Cai, Weiwei; Zhang, Zhaojing; Ren, Ge; Shen, Qiuxuan; Hou, Yanan; Ma, Anzhou; Deng, Ye; Wang, Aijie; Liu, Wenzong

2016-01-01

Highlights: • Enhanced hydrogen yield has been achieved with addition of AHL. • AHL regulated exoelectrogens resulting in electrochemical activity enhancement. • Microbial community shift in cathodic biofilm inhibited hydrogen loss. - Abstract: Quorum sensing has been widely applied to enhance the energy recovery of bioelectrochemical system as a sustainable pathway to enhance communication between cells and electrodes. However, how signalling molecules (acyl-homoserine lactones, AHLs) regulate the microbial community to improve hydrogen generation in microbial electrolysis cells (MECs) is not well understood, especially the subsequent influence on interspecies relationships among not only electrode-respiring bacteria but also hydrogen scavengers. Understanding AHL regulation in a complicated and actual biofilm system will be valuable for future applications of microbial electrochemical technology. Herein, we added short-chain AHLs (3OC6) to regulate the biofilm community on bio-electrodes in MECs. As a result, hydrogen yields were enhanced with AHL addition, increasing by 5.57%, 38.68%, and 81.82% with varied external voltages (0.8 V, 0.6 V, and 0.4 V, respectively). Accordingly, overall reactor performance was enhanced, including coulombic efficiency, electron recovery efficiency, and energy efficiency. Based on an electrochemical impedance spectra analysis, the structured biofilm under simple nutrient conditions (acetate) showed a lower internal resistance with AHL addition, indicating that the microbial communities were altered to enhance electron transfer between the biofilm and electrode. The change in the cathodic microbial structure with more electrochemically active bacteria and fewer hydrogen scavengers could contribute to a higher electron recovery and hydrogen yield with AHL addition. The regulation of the microbial community structure by AHLs represents a potential strategy to enhance electron transfer and hydrogen generation in

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

OpenAIRE

Koh, Chong-Lek; Sam, Choon-Kook; Yin, Wai-Fong; Tan, Li Ying; Krishnan, Thiba; Chong, Yee Meng; Chan, Kok-Gan

2013-01-01

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 selec...

Medier og digital kultur

DEFF Research Database (Denmark)

Christiansen, René Boyer; Hestbech, Astrid Margrethe; Jørnø, Rasmus Leth Vergmann

ser en film eller er til en koncert. Børn og unge bliver ikke længere betragtet som novicer, men mere som forbrugere og kunder, der kræver at blive engageret og underholdt. Også i pædagogisk praksis må man derfor tage højde for, at børn, unge og brugere generelt kommer med nye forventninger og...... målbeskrivelser og krav til metodevalget, og der findes nu et modul, der indholdsmæssigt fokuserer på netop medier og digital kultur. Der er derfor behov for et samlet værk, der fagligt funderet diskuterer den nyeste viden om medier i pædagogisk praksis ud fra kravene om fokuseret og reflekteret arbejde med mål...

Selen og vitamin E til søer og pattegrise

DEFF Research Database (Denmark)

Nielsen, H. E.; Danielsen, V.; Simesen, M. G.

1977-01-01

Formålet med dette forsøg var at undersøge virkningen af foderets selen- og vitamin E indhold på søernes frugtbarhed og pattegrisenes levedygtighed og vækst. Endvidere at undersøge koncentrationen af selen (Se) og vitamin E i råmælk, somælk og blod i relation til foderet. Der forekom enkelte...... dødsfald blandt grisene, som kunne sættes i forbindelse med enten lavt Se-indhold eller lavt vitamin E indhold i foderet. Der blev desuden konstateret flere brunst- og drægtighedsproblemer hos søer, derfik foder med det lave indhold af vitamin E end hos søer i de andre grupper. En forøgelse af Se......-indholdet fra 30 til 60 µg pr. kg foder gav en fordobling af indholdet i råmælk og i somælk. En forøgelse af vitamin E indholdet i foderet fra ca. 20 mg til ca. 45 mg pr. kg foder gav 4 gange forøgelse i råmælk og somælk. Der blev konstateret tilsvarende virkninger af Se og vitamin E i foderet på indholdet i...

Normalitet og afvigelse

DEFF Research Database (Denmark)

Holst, Jesper

2009-01-01

Anmeldelse ad Ivar Morkens bog:" Normalitet og afvigelse", der tager udgangspunkt i kontrasten mellem visionerne om inklusion, empowerment og anerkendelse og de faktiske forhold, hvor menneskelig afvig stadig diagnosticeres. Kontrasterne defineres og forsøges imødegået med forskellige former for ...

Relationer mellem teori og praksis i pædagogisk og lærerfagligt arbejde

DEFF Research Database (Denmark)

Knudsen, Lars Emmerik Damgaard

måder, og de hver af disse understøtter bestemte opfattelser af pædagogik og undervisning. Denne bog forsøger derfor give svar på, hvordan du kan forstå og omsætte relationerne mellem teori og praksis i dine pædagogiske studier og aktiviteter. Bogen giver dig viden om: • Hvordan og hvorfor teori og......Forbindelsen mellem teori og praksis er en grundlægende udfordring. Det gælder alle fag og professioner men ikke mindst for lærer- og pædagogstuderende, som netop formidler viden og som denne bog derfor adresserer. Den grundlæggende idé er, at teori og praksis kan relateres på flere forskellige...... praksis relaterer sig til hinanden som forskellige vidensformer, og hvordan disse forskellige former for viden ofte knytter sig til den kultur, som de optræder i. • Hvordan du kan analysere og syntetisere den måde, du i dit eget pædagogiske arbejde relaterer teori og praksis på, så du dermed også kan...

Quorum sensing: an under-explored phenomenon in the phylum Actinobacteria

Directory of Open Access Journals (Sweden)

Ashish Vasant Polkade

2016-02-01

Full Text Available 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.

Print og netaviser i Danmark, USA og Frankrig

DEFF Research Database (Denmark)

Ørsten, Mark; Willig, Ida

2013-01-01

Denne artikel undersøger forskelle og ligheder mellem print og netaviser i Danmark, USA og Frankrig, både på tværs af platforme og på tværs af de tre analyserede lande. Den komparative analyse sker med udgangspunkt i mediesystemteori, hvor Danmark er placeret i den korporative/demokratiske model,...... vinde indpas på bekostning af de andre modeller. Denne artikels resultater peger dog på, at kommercielle aspekter muligvis har større indflydelse på tværs af alle tre modeller, når det komparative fokus skifter fra print til net....

Dokumentation og forskning

DEFF Research Database (Denmark)

Ridder, Hanne Mette Ochsner

2018-01-01

Nyt fra Forskerprogrammet i musikterapi. Review-artikler vedr. musikterapi og onkologi og demens. Særnummer i Approaches om Europæisk GIM forening. Bogudgivelse: Lindvang & Beck (Red). Musik, krop og følelser. Neuroaffektive processer i musikterapi samt Jensen (Red.) Kultur og Sundhed. TV-serie s...

Professionalitet og medlemsdemokrati

DEFF Research Database (Denmark)

Nielsen, Anette; Johannsen, Gundi Schrötter

2017-01-01

begreb om udspændthed (Kofoed 2003 & Neidel 2011) samt Erving Goffmans begreber om frontstage og backstage (Jacobsen & Kristiansen 2014). Analyserne viser en kompleks praksis udspændt mellem forskelligrettede krav og forventninger og med stadige forhandlinger, som både medarbejdere og medlemmer må...

The Small Molecule DAM Inhibitor, Pyrimidinedione, Disrupts Streptococcus pneumoniae Biofilm Growth In Vitro.

Directory of Open Access Journals (Sweden)

Mukesh Kumar Yadav

Full Text Available Streptococcus pneumoniae persist in the human nasopharynx within organized biofilms. However, expansion to other tissues may cause severe infections such as pneumonia, otitis media, bacteremia, and meningitis, especially in children and the elderly. Bacteria within biofilms possess increased tolerance to antibiotics and are able to resist host defense systems. Bacteria within biofilms exhibit different physiology, metabolism, and gene expression profiles than planktonic cells. These differences underscore the need to identify alternative therapeutic targets and novel antimicrobial compounds that are effective against pneumococcal biofilms. In bacteria, DNA adenine methyltransferase (Dam alters pathogenic gene expression and catalyzes the methylation of adenine in the DNA duplex and of macromolecules during the activated methyl cycle (AMC. In pneumococci, AMC is involved in the biosynthesis of quorum sensing molecules that regulate competence and biofilm formation. In this study, we examine the effect of a small molecule Dam inhibitor, pyrimidinedione, on Streptococcus pneumoniae biofilm formation and evaluate the changes in global gene expression within biofilms via microarray analysis. The effects of pyrimidinedione on in vitro biofilms were studied using a static microtiter plate assay, and the architecture of the biofilms was viewed using confocal and scanning electron microscopy. The cytotoxicity of pyrimidinedione was tested on a human middle ear epithelium cell line by CCK-8. In situ oligonucleotide microarray was used to compare the global gene expression of Streptococcus pneumoniae D39 within biofilms grown in the presence and absence of pyrimidinedione. Real-time RT-PCR was used to study gene expression. Pyrimidinedione inhibits pneumococcal biofilm growth in vitro in a concentration-dependent manner, but it does not inhibit planktonic cell growth. Confocal microscopy analysis revealed the absence of organized biofilms, where cell

Emergens og transkulturalitet

DEFF Research Database (Denmark)

Simonsen, Karen-Margrethe

2009-01-01

Artiklen handler om, hvordan latinamerikansk litteratur og især magisk realisme udveksler med verden og hvordan den læses og brandes uden for Latinamerika. Jeg argumenterer for, at begreberne "emergens" (Wlad Godzich) og "transkulturation" (Fernando Ortiz) er gode til at beskrive nogle af de...

Samtalekarismaet og symmetriproblemet

Directory of Open Access Journals (Sweden)

Tobias Dam Hede

2011-12-01

Full Text Available Artiklen argumenterer for at coachingdiskursen ikke primært har sin oprindelse i sporten, men derimod i en fleksibel model for sammenhængen mellem ledelse, subjektivitet og erkendelse. Med inspiration fra Michel Foucault udvikles en analysestrategi - truth game analysis - der kan operere på to niveauer, som ellers kan være svære at forene: det genealogiske niveau og det empiriske niveau. Det centrale tema i analysen er udviklingen af teknikker og praksisser for, hvordan en professionel samtalepartner kan bistå et andet menneske med at vende sig imod det, der er særligt væsentligt for den enkelte selv og det fællesskab, han definerer sig i forhold til. Dermed bliver coachingforløbet forpligtet på en "sandhedskontrakt", hvor "vendingerne imod det væsentlige" bliver de afgørende sandhedsproducerende momenter for samtalens udvikling og resultat. Artiklen konstruerer begrebet samtalekarismaet som den betegnelse for den effekt, hvor coachee i kraft af samtalen oplever at få del i en rigere forståelse af sig selv og sine muligheder. Problemet er at erkendelsesarbejdet i samtalen er betinget af en række udfordringer, som har med samtalens socialitet og interaktion at gøre, dvs. samtalens praktiske tilegnelse på trods af og ved hjælp af: Ulige fordeling af magt, frihed, position og autoritet, ulige fordeling af rettigheder og pligter til at spørge og svare; blandede motiver i forhold til, hvad den ene vil opnå af den anden og omvendt - og altså alt det, der hører til det projektive univers som grundvilkår for samtalens udvikling, vedligeholdelse - og mulige sammenbrud. Disse udfordringer håndteres under samtalebetegnelsen symmetriproblemet, som samtidig bygger på en antagelse (jeg-du-hypotesen om at samtalens effektivitet som strategi for subjektivitet og erkendelse forudsætter udviklingen af en særlig relationel kvalitet imellem de samtalende, som går på tværs af samtalens komplekse fordeling af strategiske ressourcer

Bevægelser i og på tværs af ekstreme grupper og bande- og rockermiljøet

DEFF Research Database (Denmark)

Christensen, Tina Wilchen; Mørck, Line Lerche

/ekstreme grupper og netværk. Denne rapport giver således et billede af de komplekse bevægelsesmønstre i og på tværs af kriminelle netværk, bander, rockere og ekstreme grupper. Den giver en nuanceret forståelse af de veje ind, processer og perspektiver, der er nødvendige at begribe, når man skal udvikle og arbejde...... udsagn og handling. Når ”Cross-over” bygger videre på disse etablerede antagelser risikerer vi, at antagelserne med tiden etableres som forklaringer. Den etablerede ”Cross-over” kategori kan derved utilsigtet medvirke til, at vi overser de komplekse dynamikker, der er på spil i og på tværs af kriminelle...

Menneskerettighederne og Holocaust

DEFF Research Database (Denmark)

Wæhrens, Anne

2012-01-01

Menneskerettighederne er i dag et centralt element i de fleste demokratiske staters opbygning, og de er afgørende for staternes forståelse af sig selv. Holocaust og menneskerettighederne bliver ofte set som forbundne, men er de det? Hvor står menneskerettighederne i dag? Og hvad gør man for at fo......Menneskerettighederne er i dag et centralt element i de fleste demokratiske staters opbygning, og de er afgørende for staternes forståelse af sig selv. Holocaust og menneskerettighederne bliver ofte set som forbundne, men er de det? Hvor står menneskerettighederne i dag? Og hvad gør man...

Smagsoplevelse og Fordybelse

DEFF Research Database (Denmark)

Brodersen, Peter

2017-01-01

Smag og smagsoplevelser har en selvstændig plads i faget madkundskab, og som sådan er de sigtekorn for dannelsesforestillinger. Med afsæt i teorien om kategorial dannelse drøfter kapitlet, hvordan fordybelse gennem sansebaserede og æstetiske smagsoplevelser på den ene side og analytiske aktivitet...

Mord og metafysik

DEFF Research Database (Denmark)

Hansen, Kim Toft

Krimien er traditionelt indskrevet i en moderne samfundsramme, hvor opklaringen sker ved hjælp af rationelle og empiriske hjælpemidler. Derfor har krimien gennem mange år været kritisk over for metafysik, religion og det overnaturlige. Mord og metafysik viser, at skellet mellem krimi og metafysik...

Kamp og status

DEFF Research Database (Denmark)

Hansen, Christian Sandbjerg; Dahl, Hanne Marlene; Eklund Hansen, Anette

Dette bind er det første af to om børnehavens og pædagogprofessionens historie og aktualitet. Bind 2, Kald og kundskab, går tæt på indholdet i småbørnspædagogikken og i uddannelserne fra 1870 til i dag....

Musik og folkesundhed

DEFF Research Database (Denmark)

Bonde, Lars Ole; Ekholm, Ola

2015-01-01

Præsentation af undersøgelsen "Musik og folkesundhed", som er blevet til i et samarbejde mellem Musikterapi AAU og Statens Institut for Folkesundhed......Præsentation af undersøgelsen "Musik og folkesundhed", som er blevet til i et samarbejde mellem Musikterapi AAU og Statens Institut for Folkesundhed...

Quorum sensing regulates the osmotic stress response in Vibrio harveyi.

Science.gov (United States)

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. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Lyset og livet

DEFF Research Database (Denmark)

Oxenvad, Carsten Michael

2003-01-01

Beskrivelse af Øster Aaby Friskole og friskoler generelt. Blandt bidragyderne: Susanne Eskildsen, Holger Henriksen, Margrethe Vestager, John Iversen, Thorstein Balle og Poul Erik Søe......Beskrivelse af Øster Aaby Friskole og friskoler generelt. Blandt bidragyderne: Susanne Eskildsen, Holger Henriksen, Margrethe Vestager, John Iversen, Thorstein Balle og Poul Erik Søe...

Politik og organisation, organisation og politik

DEFF Research Database (Denmark)

Christensen, Jørgen Grønnegård

2006-01-01

Artiklen beskæftiger isg med samspillet mellem politiske og organisatoriske variable i analysen af administrativ adfærd. Gennem tre casestudier beslyses situationer, hvor skift i politiske præferencer og politisk dagsorden sklår umiddelbart igennem i administrativ praksis (Udlændingestyrelsen), h...

Teorien om alt og andre artikler om sprog og filosofi

DEFF Research Database (Denmark)

Artikelsamling i anledning af Peter Widells 60-års fødselsdag, med emnerne: 1. Stilistik og litteraturvidenskab  (7 artikler), 2. Leksikografi, semantik og grammatik (10 artikler), 3. Sprogfilosofi, sprogpsykologi og metaforteori (10 artikler)....

Supervisand og supervisor

DEFF Research Database (Denmark)

Jacobsen, Claus Haugaard

2007-01-01

Kapitlet redegør for aspekter ved det komplekse forhold mellem supervisand og supervisor, og der anlægges en række forskellige perspektiver. Først beskrives forholdet fra supervisandens perspektiv. At indtræde i rollen som supervisand er, foruden at være lærerigt og fagligt udviklende, ofte også ...

Lean og arbejdsmiljø

DEFF Research Database (Denmark)

Jensen, Kenneth

Bogen tager udgangspunkt i en undersøgelse af 10 private og offentlige virksomheders erfaringer med lean. Undersøgelsen viser at der ikke findes entydige sammenhænge mellem lean og det psykosociale arbejdsmiljø. Bogen forholder sig til sammenhængen mellem lean og ledelse, lean og medarbejderens...... rolle, lean og lean og forandringsprocessen. Bogen kommer desuden med anbefalinger til hvorledes virksomheden kan gribe dialogen an for at opnå et godt lean forløb der inddrager hensynet til og effekterne af et godt psykosocialt arbejdsmiljø....

Social innovation og aktionsforskning

DEFF Research Database (Denmark)

Andersen, John; Bilfeldt, Annette

2014-01-01

Formålet med dette kapitel er at vise, hvordan aktionsforskning kan bidrage til social innovation og empowerment i velfærds- og kulturinstitutioner (plejehjem og biblioteker) på en måde, der fremmer marginaliserede medborgere og lokalområders magtposition og skaber muligheder for positiv forandring....... Kapitlet præsenterer først mere overordnet de kritiske begreber om empowerment, aktionsforskning og social innovation og disse tilganges rødder i kritisk teori. Efterfølgende gennemgås to forskellige metodiske varianter af aktionsforskning i to forskellige kontekster....

Mindfulness og nærværende opmærksomhed i skole og daginstitution

DEFF Research Database (Denmark)

Nielsen, Anne Maj; Herskind, Mia

Mindfulness og nærværende opmærksomhed i skole og daginstitution Vi præsenterer resultater fra undersøgelser af, hvordan lærere og pædagoger lærer mindfulness og hvordan det får betydning for deres praksis og forholdemåder i pædagogik og undervisning. Undersøgelserne er kvalitative og i...

Urbanitet, lyd og kunst

DEFF Research Database (Denmark)

2012-01-01

designere med lyd og kunst i byrummet? Med dette fokus ønsker vi at definere og diskutere fremkomsten nye relationer mellem byen og den auditive kultur, hvor stedsspecificitet, byens kvalitative og æstetiske lyde og det offentlige rums uforudsigelighed tages op. Vi har inviteret danske såvel som...

Turtelduer?: Medier, stat og politik i Central- og Østeuropa. Medieforandring i Central- og Østeuropa: Udvikling af en analysemodel

Directory of Open Access Journals (Sweden)

Karol Jacubowicz

1996-09-01

Full Text Available Den polske medieforsker, Karol Jakubowicz, tager os med på en rundtur i de tidligere kommunistiske lande i Øst- og Centraleuropa. Hvordan går det med pressefriheden og mediernes løsrivelse fra staten? spørger han. Han opstiller følgende kriterier for frie medier: Differentiering, professiona- lisering af journalister, demonopolisering, decentralisering og en grad af demokratisering. Ifølge Jakubowicz er der en tæt sammenhæng mellem de politiske og økonomiske reformer, et land har gennemgået, og medier- nes frigørelsesproces. De tidligere kommunistiske lande grupperes efter, hvilket stade medieudviklingen er nået til og de politiske og økonomiske forhindringer for medieudviklingen opregnes. Den gennemgående tendens i det østeuropæiske medielandskab er "italienske tilstande", dvs. udbredt statslig kontrol med medierne, stærke partitilhørsforhold og integration mellem medier og den politiske elite, konkluderer Jakubowicz. Artiklen har før været publiceret i tidsskriftet Javnost/The Public.

Ytringsfrihed og blasfemi

DEFF Research Database (Denmark)

Schaumburg-Müller, Sten

2009-01-01

En redegørelse for forholdet mellem blasfemi, ytringsfrihed og religionsforhånelse. Der argumenteres endvidere for at blasfemibestemmelsen i den danske straffelov ikke udtrykker gældende ret, at det stedse er vanskeligt at finde en balance mellem den vigtige ytringsfrihed og de nødvendige indskræ...... indskrænkninger (såsom børneporne, opfordringer til vold og folkemord) og at beskyttelse af religion ikke har noget med menneskerettigheder at gøre og at forbud mod religionsforhånelse risikerer at stride mod menneskerettighederne....

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

Directory of Open Access Journals (Sweden)

Christopher N LaRock

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

Mutation of the cyclic di-GMP phosphodiesterase gene in Burkholderia lata SK875 attenuates virulence and enhances biofilm formation.

Science.gov (United States)

Jung, Hae-In; Kim, Yun-Jung; Lee, Yun-Jung; Lee, Hee-Soo; Lee, Jung-Kee; Kim, Soo-Ki

2017-10-01

Burkholderia sp. is a gram-negative bacterium that commonly exists in the environment, and can cause diseases in plants, animals, and humans. Here, a transposon mutant library of a Burkholderia lata isolate from a pig with swine respiratory disease in Korea was screened for strains showing attenuated virulence in Caenorhabditis elegans. One such mutant was obtained, and the Tn5 insertion junction was mapped to rpfR, a gene encoding a cyclic di-GMP phosphodiesterase that functions as a receptor. Mutation of rpfR caused a reduction in growth on CPG agar and swimming motility as well as a rough colony morphology on Congo red agar. TLC analysis showed reduced AHL secretion, which was in agreement with the results from plate-based and bioluminescence assays. The mutant strain produced significantly more biofilm detected by crystal violet staining than the parent strain. SEM of the mutant strain clearly showed that the overproduced biofilm contained a filamentous structure. These results suggest that the cyclic di-GMP phosphodiesterase RpfR plays an important role in quorum sensing modulation of the bacterial virulence and biofilm formation.

Dokumentation og forskning

DEFF Research Database (Denmark)

Ridder, Hanne Mette Ochsner

2012-01-01

Udover en liste over de nyeste specialeafhandlinger er der Nyt fra Forskerprogrammet i musikterapi, og bl.a. omtale af effekt-undersøgelser vedr. musik og autisme, immunsystemet samt astma.......Udover en liste over de nyeste specialeafhandlinger er der Nyt fra Forskerprogrammet i musikterapi, og bl.a. omtale af effekt-undersøgelser vedr. musik og autisme, immunsystemet samt astma....

Ford og fordismen

DEFF Research Database (Denmark)

Wagner, Michael

Fordismen var et epokegørende, nybrydende og vidtspændende globalt fænomen, som opstod i begyndelsen af det 20. århundrede. I sit udspring byggede ophavsmanden til fordismen, automobilkongen Henry Ford, på et utroligt solidt, billigt og driftsikkert produkt, nemlig automobilet Ford Model T....... Fordismen udvikler en helt ny industriel produktionsmåde beregnet til masseproduktion af varige forbrugsgoder og en samfundsfilosofi. Fordismens epoke skabte en helt ny økonomisk teori om massekonsumets betydning i samfundet. Henry Ford dikterede på grundlag af sin store og iøjnefaldende succes en totalitær...... fra 1908, hvor produktionen af Ford Model T blev indledt, og frem til efteråret 1929, da børsen i Wall Street krakkede og trak hele verdensøkonomien ind i en dyb og langvarig krise. Produktionen af Ford Model T var blevet indstillet to år forinden; da havde man rundet et antal på 15 millioner...

Investigation of Pseudomonas aeruginosa quorum-sensing signaling system for identifying multiple inhibitors using molecular docking and structural analysis methodology.

Science.gov (United States)

Soheili, Vahid; Bazzaz, Bibi Sedigheh Fazly; Abdollahpour, Nooshin; Hadizadeh, Farzin

2015-12-01

Pseudomonas aeruginosa is an opportunistic human pathogen and a common Gram-negative bacterium in hospital-acquired infections. It causes death in many burn victims, cystic-fibrosis and neutropenic-cancer patients. It is known that P. aeruginosa biofilm maturation and production of cell-associated and extracellular virulence factors such as pyocyanin, elastase and rhamnolipids are under the control of a quorum-sensing (QS) system. Among several proteins involved in the Pseudomonas QS mechanism, LasR and PqsE play an important role in its cascade signaling system. They can cause increases in QS factors, biofilm maturation, and the production of virulence factors. Therefore, inhibition of these proteins can reduce the pathogenicity of P. aeruginosa. According to the structure of corresponding auto-inducers bound to these proteins, in silico calculations were performed with some non-steroidal anti-inflammatory drugs (NSAIDs) to estimate possible interactions and find the co-inhibitors of LasR and PqsE. The results showed that oxicams (Piroxicam and Meloxicam) can interact well with active sites of both proteins with the Ki of 119.43 nM and 4.0 μM for Meloxicam and 201.39 nM and 4.88 μM against LasR and PqsE, respectively. These findings suggested that Piroxicam and Meloxicam can be used as potential inhibitors for control of the P. aeruginosa QS signaling system and biofilm formation, and may be used in the design of multiple inhibitors. Copyright © 2015 Elsevier Ltd. All rights reserved.

Folkedans, elitekultur og nationalisme

DEFF Research Database (Denmark)

Østergaard, Uffe

2017-01-01

Historisk set. Begreberne folkedans og folkemusik blev i løbet af 1900-tallet overtaget af de udøvende, og samtidig ændredes dansens sociale funktion og rituelle betydning. Folkedansen er ikke blevet til et nationalt symbol.......Historisk set. Begreberne folkedans og folkemusik blev i løbet af 1900-tallet overtaget af de udøvende, og samtidig ændredes dansens sociale funktion og rituelle betydning. Folkedansen er ikke blevet til et nationalt symbol....

Om musik og multimedier

DEFF Research Database (Denmark)

Knakkergaard, Martin

1998-01-01

Artiklen søger, gennem eksemplificering og diskussion, at problematisere forholdet musik og multimedia. Der er ikke tale om et forsøg på at nå til nogen endegyldig afgrænsning og bestemmelse af de karakteristika og betingelser, der kendetegner feltet. Formålet er derimod at belyse og præcisere...

Eg høyrer og eg gløymer, eg ser og eg huskar, eg gjer og eg forstår

OpenAIRE

Liavåg, Sturla Sætre

2017-01-01

Høgskulen på Vestlandet Avdeling for helsefag/ Institutt for sjukepleie/Campus Førde Slik som sjukepleiaryrket utviklar seg no til dags får sjukepleiaren meir og meir ansvar. Dette gjeld både sjukepleiarar som yrkesgruppe men og som enkeltpersonar. Ein kan oppleve å gå rett frå sjukepleiarstudiet og inn på ein arbeidsplass, og der oppleve å vere einaste sjukepleiar, og med stort ansvar. Som sjukepleiar stiller samfunnet både formelle og uformelle krav til kva ein skal site inne me...

Landskabskaraktermetoden og kommunerne

DEFF Research Database (Denmark)

Caspersen, Ole H.; Føns, Christina; Ginsbak, Anette

2010-01-01

Seks sydjyske kommuner, By- og Landskabsstyrelsen, KL samt Skov & Landskab har i 2010 gennemført et projekt med henblik på videre udvikling og tilpasning af landskabskaraktermetoden. Målet var at tilpasse metoden til kommunernes behov og at gøre den mere operationel og overskuelig. Dette videnbla...... er det første af fire, der redegør for resultaterne fra projektet....

Eksistens og natur

DEFF Research Database (Denmark)

Pahuus, Mogens

Eksistens og Natur er et centralt stykke livsfilosofi skrevet af en af dansk filosofis grand old men. Professor emeritus fra Aalborg Universitet Mogens Pahuus præsenterer her den grundidé om mennesket, at ethvert individ er formet i en dobbelthed mellem det givne i os - naturen - og det, at vi fo...... forholder os til det givne - eksistensen. Mogens Pahuus sammenfatter i denne bog sin livsfilosofiske tænkning, og han tør give sig i kast med en stor og systematisk fremstilling af menneskets væsen. Bogen er et modent værk med overskud og overblik....

Norlichexanthone Reduces Virulence Gene Expression and Biofilm Formation in Staphylococcus aureus

DEFF Research Database (Denmark)

Baldry, Mara; Nielsen, Anita; Bojer, Martin S.

2016-01-01

Staphylococcus aureus is a serious human pathogen and antibiotic resistant, community-associated strains, such as the methicillin resistant S. aureus (MRSA) strain USA300, continue to spread. To avoid resistance, anti-virulence therapy has been proposed where toxicity is targeted rather than...... viability. Previously we have shown that norlichexanthone, a small non-reduced tricyclic polyketide produced by fungi and lichens, reduces expression of hla encoding α-hemolysin as well as the regulatory RNAIII of the agr quorum sensing system in S. aureus 8325-4. The aim of the present study was to further...... SaeRS system. Our data show that norlichexanthone treatment reduces expression of key virulence factors in CA-MRSA strain USA300 via AgrA binding and represses biofilm formation....

Pseudomonas aeruginosa with lasI quorum-sensing deficiency during corneal infection

DEFF Research Database (Denmark)

Zhu, H.; Bandara, R.; Conibear, T.C.

2004-01-01

To understand the importance of Pseudomonas aeruginosa quorum-sensing systems in the development of corneal infection, the genotypic characteristics and pathogenesis of seven ocular isolates with low-protease and acyl homoserine lactone (AHL) activity and quorum-sensing mutants of PAO1 deficient...

Æstetik og udvikling - indledning

DEFF Research Database (Denmark)

Austring, Bennyé D.; Sørensen, Merete

2007-01-01

I indledningen til antologien Æstetik og udvikling præsenteres 10 udviklingsprojekter og rammen om dem: Kompetencecenter for Æstetik og Læring. Redaktørerne Bennyé D. Austring og Merete Sørensen gør også rede for centrets teoretiske inspirationskilder, især Hansjörg Hohr og Anne Bamford, og de...

Teori og baggrundsviden

DEFF Research Database (Denmark)

Skytte, Marianne

2005-01-01

Bogdel med følgende kapitler: Statistik om befolkningssammensætningen i Danmark. Kultur og etnicitet. Kategorisering, stereotypering, stigmatisering og diskrimination. Integrationsstrategier. Værdier omkring familieliv og børneopdragelse. Tosprogethed. Kulturagram. Dilemmaet mellem ligebehandling...

Reklamesemiotik mellem mening og virkning – komposition, kategorier og kognition

Directory of Open Access Journals (Sweden)

Christian Andersen

2004-09-01

Full Text Available På baggrund af kognitionspsykologi og peirceansk tegnteori fremsætter artiklen et reklamesemiotisk bud på sammenhængen mellem annoncers komposition og deres virkning. Artiklen har til formål at belyse, hvorledes den trykte annonces forskellige æstetikker og kompositioner udløser for- skellige emotionelle og kognitive effekter i receptionen. Der indkredses tre receptionsmodi, der hver svarer til en bestemt annoncekompositorisk kategori. Artiklen er en videreudvikling af reklamesemiotikken, som i Dan- mark især er blevet funderet på et semiologisk grundlag. Der argumente- res for, at den semiologiske tilgang kun er delvis fyldestgørende, efter- som man her læser reklamens illustration med verbalsproget som model og derved implicit antager, at verbalsproglige og visuelle tegnsystemer har samme organisation. I modsætning til sproget mangler billedet imid- lertid den dobbelte artikulation. Artiklen forsøger at indfange disse forskel- le mellem tegnsystemer for derigennem at oparbejde et mere nuanceret blik for, i hvilket omfang forskellige reklameæstetikker faktisk udløser bestemte kognitive effekter i receptionen. Ved ’kognitive effekter’ forstås primært emotionsdannelse og inferensprocesser.

At finde rundt i klinisk praksis og om de enkelte rums funktion og betydning

DEFF Research Database (Denmark)

Larsen, Kristian

2013-01-01

de rumlige omgivelser er relevant, fordi læring i praksis i højeste grad foregår i fysiske, arkitektoniske rammer med specifikke sociale spilleregler for, hvad man gør og ikke gør i et konferencerum, en sygestue eller i patientens eget hjem. Arkitektur er således materielt og kropsligt nærværende...... læremester, og rumlige omgivelser involverer også magtrelationer,som hvem der besidder hvilke lokaliteter og artefakter og hvem, der ikke gør det. Dette kapitel angår relationer mellem mennesker og fysiske omgivelser, og det er hensigten at gøre rede for både enkle og komplekse forhold. I den forbindelse vil...

Informatik og eventyr - videotex i Frankrig og Danmark

Directory of Open Access Journals (Sweden)

Mads Christoffersen

1989-09-01

Full Text Available Da eksperimenterne med videotex, eller teledata som teleselskaberne kalder det, blev påbegyndt i Danmark i 1982, var forventningerne til informations- udbud og brugerefterspørgsel store. Forventningerne blev imidlertid ikke indfriet, og selvom systemet er blevet relanceret, lever det danske teledata fortsat en skyggetilværelse med omkring 2400 brugere. I modsætning hertil er det i Frankrig lykkedes at udvikle et videotex-koncept, der er blevet en succes. I denne artikel analyserer Mads Christoffersen videotex-udviklingen i henholdsvis Danmark og Frankrig og belyser årsagerne til den forskellige udvikling. Endelig skitserer han et seks punkts program for en dansk tele- matik-politik, der kan gøre videotex til et slagkraftigt medium i Danmark.

Inhibition of quorum sensing and biofilm formation in Vibrio harveyi by 4-fluoro-DPD; a novel potent inhibitor of signalling.

Science.gov (United States)

Kadirvel, Manikandan; Fanimarvasti, Fariba; Forbes, Sarah; McBain, Andrew; Gardiner, John M; Brown, Gavin D; Freeman, Sally

2014-05-21

(S)-4,5-Dihydroxypentane-2,3-dione [(S)-DPD, (1)] is a precursor for , a quorum sensing signalling molecule for inter- and intra-species bacterial communication. The synthesis of its fluoro-analogue, 4-fluoro-5-hydroxypentane-2,3-dione () is reported. An intermediate in this route also enables a new, shorter synthesis of the native (S)-DPD. 4-Fluoro-DPD (2) completely inhibited bioluminescence and bacterial growth of Vibrio harveyi BB170 strain at 12.5 μM and 100 μM, respectively.

Stereochemical insignificance discovered in Acinetobacter baumannii quorum sensing.

Directory of Open Access Journals (Sweden)

Amanda L Garner

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

Risiko og usikkerhed - miljø og fødevarer

DEFF Research Database (Denmark)

Løkke, H.

given risiko, stor eller lille. Det er politikernes og myndighedernes opgave at sørge for love og regler, som beskytter miljøet og befolkningen. På de fleste områder er der imidlertid et spillerum for forbrugernes valg. Vi vælger fx selv om vi vil købe den ene eller den anden type af vaskepulver eller...

Uddannelse og Entrepreneurship

DEFF Research Database (Denmark)

Blenker, Per; Dreisler, Poul; Færgemann, Helle Maibom

2004-01-01

Innovation og entrepreneurship står højt på den politiske dagsorden og universiteterne er tiltænkt en central rolle i denne proces, hvis mål er at skabe større vækst og øget velfærd i samfundet. Et af midlerne har været at motivere til større samarbejde om forskning og uddannelse i samspil mellem...

Cooperative pathogenicity in cystic fibrosis: Stenotrophomonas maltophilia modulates Pseudomonas aeruginosa virulence in mixed biofilm

Directory of Open Access Journals (Sweden)

Arianna ePompilio

2015-09-01

Full Text Available The present study was undertaken in order to understand more about the interaction occurring between S. maltophilia and P. aeruginosa, which are frequently co-isolated from CF airways. For this purpose, S. maltophilia RR7 and P. aeruginosa RR8 strains, co-isolated from the lung of a chronically infected CF patient during a pulmonary exacerbation episode, were evaluated for reciprocal effect during planktonic growth, adhesion and biofilm formation onto both polystyrene and CF bronchial cell monolayer, motility, as well as for gene expression in mixed biofilms. P. aeruginosa significantly affected S. maltophilia growth in both planktonic and biofilm cultures, due to an inhibitory activity probably requiring direct contact. Conversely, no effect was observed on P. aeruginosa by S. maltophilia. Compared with monocultures, the adhesiveness of P. aeruginosa on CFBE41o- cells was significantly reduced by S. maltophilia, which probably acts by reducing P. aeruginosa's swimming motility. An opposite trend was observed for biofilm formation, confirming the findings obtained using polystyrene. When grown in mixed biofilm with S. maltophilia, P. aeruginosa significantly over-expressed aprA, and algD - codifying for protease and alginate, respectively - while the quorum sensing related rhlR and lasI genes were down-regulated. The induced alginate expression by P. aeruginosa might be responsible for the protection of S. maltophilia against tobramycin activity we observed in mixed biofilms. Taken together, our results suggest that the existence of reciprocal interference of S. maltophilia and P. aeruginosa in CF lung is plausible. In particular, S. maltophilia might confer some selective fitness advantage to P. aeruginosa under the specific conditions of chronic infection or, alternatively, increase the virulence of P. aeruginosa thus leading to pulmonary exacerbation.

Lydighedsetik og bureaukratisk grusomhed

DEFF Research Database (Denmark)

Moesby-Jensen, Cecilie Kolonda; Moesby-Jensen, Tommy

2017-01-01

I dette kapitel fokuseres der på samarbejdet mellem socialrådgivere i en forvaltnings familieafdeling og ansatte i Psykologisk og Pædagogisk Rådgivning (PPR). Vi vil vise, hvordan denne arbejdsorganisering har afgørende bureaukratiske træk og derfor rummer lydighedsetiske problemer – et begreb, d...... tager udgangspunkt i et myndighedssocialrådgiver-perspektiv og dermed i, hvordan de oplever samarbejdet. Analyserne fremskrives og diskuteres med udgangspunkt i teoretiske perspektiver hos Max Weber, Zygmunt Bauman, Etienne Wenger, Paul Duguid og John Seely Brown....

Individualiseringens vindere og tabere

DEFF Research Database (Denmark)

Rasborg, Klaus

2013-01-01

Snarere end værdiforfald og egoisme er nutidens individualisering ensbetydende med fremkomsten af nye værdier, deltagelsesformer og politiske orienteringsmønstre. Der er imidlertid både vindere og tabere i individualiseringsspillet, hvilket artiklen forsøger at vise.......Snarere end værdiforfald og egoisme er nutidens individualisering ensbetydende med fremkomsten af nye værdier, deltagelsesformer og politiske orienteringsmønstre. Der er imidlertid både vindere og tabere i individualiseringsspillet, hvilket artiklen forsøger at vise....

Cinnamaldehyde and cinnamaldehyde derivatives reduce virulence in Vibrio spp. by decreasing the DNA-binding activity of the quorum sensing response regulator LuxR

Directory of Open Access Journals (Sweden)

Van Calenbergh Serge

2008-09-01

Full Text Available Abstract Background To date, only few compounds targeting the AI-2 based quorum sensing (QS system are known. In the present study, we screened cinnamaldehyde and substituted cinnamaldehydes for their ability to interfere with AI-2 based QS. The mechanism of QS inhibition was elucidated by measuring the effect on bioluminescence in several Vibrio harveyi mutants. We also studied in vitro the ability of these compounds to interfere with biofilm formation, stress response and virulence of Vibrio spp. The compounds were also evaluated in an in vivo assay measuring the reduction of Vibrio harveyi virulence towards Artemia shrimp. Results Our results indicate that cinnamaldehyde and several substituted derivatives interfere with AI-2 based QS without inhibiting bacterial growth. The active compounds neither interfered with the bioluminescence system as such, nor with the production of AI-2. Study of the effect in various mutants suggested that the target protein is LuxR. Mobility shift assays revealed a decreased DNA-binding ability of LuxR. The compounds were further shown to (i inhibit biofilm formation in several Vibrio spp., (ii result in a reduced ability to survive starvation and antibiotic treatment, (iii reduce pigment and protease production in Vibrio anguillarum and (iv protect gnotobiotic Artemia shrimp against virulent Vibrio harveyi BB120. Conclusion Cinnamaldehyde and cinnamaldehyde derivatives interfere with AI-2 based QS in various Vibrio spp. by decreasing the DNA-binding ability of LuxR. The use of these compounds resulted in several marked phenotypic changes, including reduced virulence and increased susceptibility to stress. Since inhibitors of AI-2 based quorum sensing are rare, and considering the role of AI-2 in several processes these compounds may be useful leads towards antipathogenic drugs.

Cinnamaldehyde and cinnamaldehyde derivatives reduce virulence in Vibrio spp. by decreasing the DNA-binding activity of the quorum sensing response regulator LuxR

Science.gov (United States)

Brackman, Gilles; Defoirdt, Tom; Miyamoto, Carol; Bossier, Peter; Van Calenbergh, Serge; Nelis, Hans; Coenye, Tom

2008-01-01

Background To date, only few compounds targeting the AI-2 based quorum sensing (QS) system are known. In the present study, we screened cinnamaldehyde and substituted cinnamaldehydes for their ability to interfere with AI-2 based QS. The mechanism of QS inhibition was elucidated by measuring the effect on bioluminescence in several Vibrio harveyi mutants. We also studied in vitro the ability of these compounds to interfere with biofilm formation, stress response and virulence of Vibrio spp. The compounds were also evaluated in an in vivo assay measuring the reduction of Vibrio harveyi virulence towards Artemia shrimp. Results Our results indicate that cinnamaldehyde and several substituted derivatives interfere with AI-2 based QS without inhibiting bacterial growth. The active compounds neither interfered with the bioluminescence system as such, nor with the production of AI-2. Study of the effect in various mutants suggested that the target protein is LuxR. Mobility shift assays revealed a decreased DNA-binding ability of LuxR. The compounds were further shown to (i) inhibit biofilm formation in several Vibrio spp., (ii) result in a reduced ability to survive starvation and antibiotic treatment, (iii) reduce pigment and protease production in Vibrio anguillarum and (iv) protect gnotobiotic Artemia shrimp against virulent Vibrio harveyi BB120. Conclusion Cinnamaldehyde and cinnamaldehyde derivatives interfere with AI-2 based QS in various Vibrio spp. by decreasing the DNA-binding ability of LuxR. The use of these compounds resulted in several marked phenotypic changes, including reduced virulence and increased susceptibility to stress. Since inhibitors of AI-2 based quorum sensing are rare, and considering the role of AI-2 in several processes these compounds may be useful leads towards antipathogenic drugs. PMID:18793453

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

Science.gov (United States)

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

2015-08-12

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. 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 cascades of V. harveyi. Furthermore, QS-mediated biofilm formation and swimming motility in the mutant strain BB152 (AI-1(-), AI-2(+)) were significantly reduced in the presence of HU-210. HU-210 inhibited QS-mediated virulence factor production without any inhibitory effect on bacterial growth. It also alters the expression of several genes, which are regulated by QS, specifically downregulating the genes of the AI-2 QS cascade. First evidence is being provided for interference of bacterial signal-transduction systems by a synthetic cannabinoid. The effect of HU-210 was specific to the AI-2 cascade in V. harveyi. AI-2 is known as a "universal autoinducer" and interference with its activity opens a broad spectrum of applications for synthetic cannabinoids in future research as a potential anti-QS agent.

Radon og boligen

DEFF Research Database (Denmark)

Rasmussen, Torben Valdbjørn

Radon er en radioaktiv og sundhedsskadelig luftart, som ved indånding øger risikoen for lungekræft. Der er ingen dokumenteret nedre grænse for, hvornår radon er ufarligt. Derfor anbefales det, at man tilstræber et så lavt radonindhold i indeluften som muligt. Man kan hverken lugte, se, høre eller...... smage radon, så vil du vide, om du har radon i din bolig, må du måle radonindholdet i indeluften. Radon forekommer naturligt i jorden og kan suges ind sammen med jordluft, hvis der inde er et undertryk, og hvis konstruktionerne mod jord er utætte. Jordluft trænger ind gennem revner og utætte samlinger......, fx omkring rør til kloak, vand og varmeforsyning. Koncentrationen af radon i jorden varierer meget fra sted til sted, også lokalt og gennem året. Tidligere undersøgelser har vist, at der kan forekomme høje koncentrationer i Sydgrønland, specielt i området syd for Narsalik ved Paamiut, 61°30’N....

Migration og etnicitet

DEFF Research Database (Denmark)

Christiansen, Connie Carøe

2004-01-01

Migration og etnicitet er aktuelle og forbundne fænomener, idet migration øger berøringsfladerne mellem befolkningsgrupper. Etniciteter formes i takt med at grænser drages imellem disse grupper. Imod moderniserings-teoriernes forventning forsvandt etnicitet ikke som en traditionel eller oprindelig...... måde at skabe tilhørsforhold på; globalt set fremstår vor tid istedet som en "migrationens tidsalder", der tilsyneladende også er en tidsalder, hvor kulturelle særtræk, i form af etnicitet, udgør vigtige linjer, hvorefter grupper skilller sig ud fra hinanden. Både migration og etnicitet bringer fokus...... den finder sted i modtagerlandet, men nyere perspektiver på migration, som begreber om medborgerskab, transnationalisme og diaspora er eksponenter for, søger udover den nationalstatslige ramme og inddrager konsekvenserne af migrationen for afsenderlande....

Team og test

DEFF Research Database (Denmark)

Fryd, Krogh, Pernille

Afhandlingen TEAM & TEST er en systemteoretisk og komparativ interviewundersøgelse af implementeringen af accountability-reformpolitik i grundskolen i Danmark og USA. Formålet med afhandlingen er at frembringe forskningsbaseret viden om accountability-reformpolitikkens mulige indvirkning på...... skolelederes og læreres selvforståelse og pædagogiske praksis i den offentlige grundskole i Danmark og USA. Undersøgelsen identificerer en række forskningsresultater, der indikerer, at selvstyrende teamorganisering, som ramme omkring samarbejdet om implementering af nationale standarder og test, ikke altid har...

Ventilation og luftkvalitet i kontorbygninger

DEFF Research Database (Denmark)

Valbjørn, O.; Bach Nielsen, J.; Gunnarsen, Lars Bo

Udformningen og brugen af kontorbygninger spiller en rolle for luftudvekslingen mellem rummene og derved også for luftkvaliteten. I én mekanisk og to naturligt ventilerede kontorbygninger er ventilationsforhold og luftkvalitet blevet undersøgt med dørene til kontorerne henholdsvis holdt åbne og l...... har adsorption af forureninger på overfladerne en betydning. Effekten vil kunne udnyttes ved hensigtsmæssig projektering og drift....

Befolkningsimplosion og seniorpolitik

DEFF Research Database (Denmark)

Bøye, Erik Møllmann; Bøye, Solveig

2000-01-01

Denne artikel vil først belyse baggrunden for at tale om et globalt aldersskælv eller alderdommedag og om en befolkningsimplosion - på et tidspunkt, hvor kurven for Jordens folketal næsten er lodret stigende. Derefter rettes blikket mod Danmark. De globale tendenser, lav-fertiltet og stigende...... levealder, gør sig også gældende her i landet. Sammen med den befolkningsudskiftning, der følger af retten til familiesammenføring, vil det i løbet af få år fuldstændig forandre befolkningsstrukturen her i landet. Og det diskuteres, hvilken betydning dette vil have for seniorpolitikken i de private og...

Nyhedsmedielogik og krisediplomati

DEFF Research Database (Denmark)

Ørsten, Mark

2016-01-01

Tidligere forskning i massemedier og diplomati har peget i mange forskellige retninger, men især forsøgt at undersøge, hvordan nyhedsmedier har været med til at præge den offentlige meningsdannelse i forhold til vigtige emner i både indland og udland. Med udgangspunkt i moderne medialiseringsteori...... fokuserer denne artikel på, hvordan samfundets institutioner bliver påvirket af nyhedsmedierne og deres logikker, og helt specifikt hvordan denne udvikling påvirker to af de forskellige typer af krisediplomati, der er i fokus i dette temanummer: Krisediplomati forstået som ’diplomati i krise’ og...

Dokumentation og forskning

DEFF Research Database (Denmark)

Ridder, Hanne Mette Ochsner

2013-01-01

og psykologiske symptomer på demens. Endelig omtales udgivelsen af "Musical life stories. Narratives on health musicking" fra det norske Senter for Musikk og Helse, og Nordic Journal of Music Therapi beskrives som et toneangivende tidsskrift for international musikterapi....

Baggrund og inspiration

DEFF Research Database (Denmark)

Rotne, Georg

2002-01-01

Illustreret gennemgang af den arkitektoniske anvendelse af beton og betonelementer gennem de sidste 100-150 år. Casestories: Antonio Gandi (1852-1925) og Jørn Utzon (1918-). Afsluttende betragtninger over den aktuelle og fremtidige anvendelse af betonelementer i arkitektur....

Enzyme-mediated quenching of the Pseudomonas quinolone signal (PQS promotes biofilm formation of Pseudomonas aeruginosa by increasing iron availability

Directory of Open Access Journals (Sweden)

Beatrix Tettmann

2016-12-01

Full Text Available The 2-alkyl-3-hydroxy-4(1H-quinolone 2,4-dioxygenase HodC was previously described to cleave the Pseudomonas quinolone signal, PQS, which is exclusively used in the complex quorum sensing (QS system of Pseudomonas aeruginosa, an opportunistic pathogen employing QS to regulate virulence and biofilm development. Degradation of PQS by exogenous addition of HodC to planktonic cells of P. aeruginosa attenuated production of virulence factors, and reduced virulence in planta. However, proteolytic cleavage reduced the efficacy of HodC. Here, we identified the secreted protease LasB of P. aeruginosa to be responsible for HodC degradation. In static biofilms of the P. aeruginosa PA14 lasB::Tn mutant, the catalytic activity of HodC led to an increase in viable biomass in newly formed but also in established biofilms, and reduced the expression of genes involved in iron metabolism and siderophore production, such as pvdS, pvdL, pvdA and pvdQ. This is likely due to an increase in the levels of bioavailable iron by degradation of PQS, which is able to sequester iron from the surrounding environment. Thus, HodC, despite its ability to quench the production of virulence factors, is contraindicated for combating P. aeruginosa biofilms.

Innovation og digitalisering

DEFF Research Database (Denmark)

Ivang, Reimer

2012-01-01

Kapitet fokuserer på, hvordan og hvorfor den digitale teknologi og innovation er to sider af samme sag. Den digitale teknologi er af mange anerkendt som en af nutidens største forandringskræfter. Perez (2002) benævner det ligefrem en teknologisk revolution og sammenligner den digitale teknologi m......, at innovationsprocesser ofte vil være det bedste perspektiv til at forstå, identificere og realisere det virkelige potentiale i digitalisering....

Transfer og effekt

DEFF Research Database (Denmark)

Sørensen, Peter

2017-01-01

Effekt, virkning eller udbytte af en lederuddannelse afhænger af en række individuelle, uddannelsesmæssige og organisatoriske faktorer. Det ved vi fra uddannelsesforskningen og særligt fra forskningen i transfer. Kun hvis uddannelsesinstitutionerne såvel som de studerende og arbejdspladserne vil...... medvirke aktivt til at skabe og fremme transfer, kan man gøre sig forhåbninger om, at få effekt af en lederuddannelse....

Ledelsesfilosofi og Praksis

DEFF Research Database (Denmark)

Hertel, Frederik; Fast, Michael

2015-01-01

, som f.eks. Machiavellis ”Fyrsten”, Platons ”Statsmanden”, Taylors ”The Principles of Scientific Management” og Fayols ”General and Industrial Management”, har ledelse og ledelsesforskningen således koncentreret sig om ledelsestyper, god/rigtig ledelse, management/organisering og arbejdsdeling...

Piper betle leaf extract affects the quorum sensing and hence virulence of Pseudomonas aeruginosa PAO1.

Science.gov (United States)

Datta, Siraj; Jana, Debanjan; Maity, Tilak Raj; Samanta, Aveek; Banerjee, Rajarshi

2016-06-01

Quorum sensing (QS) plays an important role in virulence of Pseudomonas aeruginosa, blocking of QS ability are viewed as viable antimicrobial chemotherapy and which may prove to be a safe anti-virulent drug. Bioactive components from Piper betle have been reported to possess antimicrobial ability. This study envisages on the anti-QS properties of ethanolic extract of P. betle leaf (PbLE) using P. aeruginosa PAO1 as a model organism. A marked reduction in swarming, swimming, and twitching ability of the bacteria is demonstrated in presence of PbLE. The biofilm and pyocyanin production also shows a marked reduction in presence of PbLE, though it does not affect the bacterial growth. Thus, the studies hint on the possible effect of the bioactive components of PbLE on reducing the virulent ability of the bacteria; identification of bioactive compounds should be investigated further.

Quorum-sensing-directed protein expression in Serratia proteamaculans B5a

DEFF Research Database (Denmark)

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

2003-01-01

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 Esal 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...

Kulturel og mental byomdannelse

DEFF Research Database (Denmark)

Samson, Kristine

2013-01-01

Redesign og kulturel byomdannelse kan være tankevækkende studier af, hvordan byer udvikler sig og omdannes under indflydelse af sociale, kulturelle og økonomiske sammenhænge. Parque Cultural de Valparaiso i Chile er et fremragende eksempel på, hvordan arkitektur og landskabsdesign forbinder sig til...... den omkringliggende by og Chiles komplekse historie. Men Parque Cultural giver samtidig et arkitektonisk rumligt bud på Valparaiso mulige fremtid....

Et ekskluderende «vi»? Verdier, kulturer og kulturarv i læreplanens generelle del og i formålsparagrafen: nasjonalt fellesskap, multikulturalitet og kulturell kompleksitet

Directory of Open Access Journals (Sweden)

Halldis Breidlid

2012-10-01

Full Text Available Artikkelens tema er hegemoniske diskurser i Generell del av læreplanen (GD og i ny formålsparagraf. Kulturarv, kulturer og verdier er viktige innganger til analyse av norskhets- og mangfolds-diskurser i disse styringsdokumentene. Jeg undersøker spesifikt hvilken hierarkisk ordning av verdier og kulturer som kommer til uttrykk i GD og i ny formålsparagraf, og hvilken tilnærming til nasjonal identitet og mangfold som følger av dette. Artikkelen undersøker også dokumentenes bruk av begrepene “kristne” og “humanistiske” verdier og utforsker hvordan disse forstås i forhold til hverandre og til andre tradisjoners verdier, og videre hvordan de knyttes til forståelsen av nasjonal identitet. Innledningsvis kommenterer jeg identitetsdanning i postmoderne kulturkomplekse samfunn ved å knytte sammen Skeies analyse av tre ulike typer pluralitet med mangfolds-diskursene «multikulturalisme» og «kulturell kompleksitet». Norskhets- og mangfolds-diskursene som kommer til uttrykk i læreplanen tolkes i lys av to samfunnsanalyser: Gullestads analyse av norsk samfunnsdebatt («det nasjonale fellesskapet» og «likhetens skillelinjer» og Slagstads analyse av religion og nasjonsbygging. Siden vekten ligger på diskurser i de skriftlige dokumentene, sett ut fra ideologiske strømninger i samfunnet, er det den ideologiske og den formelle læreplan (Goodlad som er i fokus. Min undersøkelse viser at GD, liksom formålsparagrafen, gjenspeiler den nasjonale diskursen om forestilt likhet og forestilt fellesskap, der likhetens skillelinjer går mellom majoritetens norske «vi» på den ene siden, for hvem «kristne og humanistiske verdier» tenkes å utgjøre en symbiose, og språklige og kulturelle minoriteter på den andre. Denne forståelsen utfordres av den hegemoniske samfunnsforskningen, som forstår mangfold ut fra kulturell kompleksitet.

Stemmeret og straf

DEFF Research Database (Denmark)

Rytter, Jens Elo

2016-01-01

En analyse af hvorvidt det vil være foreneligt med Grl § 29 og med EMRK at fratage straffede personer stemmeret. Det overvejes også, hvilke grunde, der taler for hhv. imod at fratage straffede personer stemmeret......En analyse af hvorvidt det vil være foreneligt med Grl § 29 og med EMRK at fratage straffede personer stemmeret. Det overvejes også, hvilke grunde, der taler for hhv. imod at fratage straffede personer stemmeret...

Luhmann og Organisation

DEFF Research Database (Denmark)

Tække, Jesper; Paulsen, Michael

2008-01-01

  Synopsis - Vi vil i denne artikel udlægge Luhmanns organisationsteori i et fugleperspektiv. Ud fra en videnskabsteoretisk og metametodologisk vinkel henvender vi os især til interesserede i organisationsteori og organisationskommunikation, som gerne vil tilegne sig Luhmanns organisationsteori i...... bevæger sig videre til systembegrebet, forskellige systemtyper, kommunikationsbegrebet og til sidst organisations- og beslutningsbegrebet. Alt i alt er det artiklens ærinde at blotlægge de begrebslige præmisser for Luhmanns organisationsteori....

Musik og psykologi

DEFF Research Database (Denmark)

Bonde, Lars Ole

Temanummeret om Musik og Psykologi skrives af over 20 bidragydere, heraf 5 udlændinge, med baggrund i musikpsykologi, musikterapi, musikvidenskab, hjerneforskning mm. Der vil være både teoretiske, kliniske og kombineret teoretisk-kliniske artikler.......Temanummeret om Musik og Psykologi skrives af over 20 bidragydere, heraf 5 udlændinge, med baggrund i musikpsykologi, musikterapi, musikvidenskab, hjerneforskning mm. Der vil være både teoretiske, kliniske og kombineret teoretisk-kliniske artikler....

Religion, migration og integration

DEFF Research Database (Denmark)

Borup, Jørn

2010-01-01

Sammenhængen mellem religion og integration har de sidste år været genstand for debat. Artiklen kommer ind på begreber og sammenhænge relateret til området (migration, diaspora, assimilation, etnicitet, kultur) og ser på religionens mulige rolle som negativ eller positiv ressource i integrationss......Sammenhængen mellem religion og integration har de sidste år været genstand for debat. Artiklen kommer ind på begreber og sammenhænge relateret til området (migration, diaspora, assimilation, etnicitet, kultur) og ser på religionens mulige rolle som negativ eller positiv ressource i...

Arbejdsmiljø og arbejdsliv

DEFF Research Database (Denmark)

ofte negative konsekvenser for de ansatte i form af: stress, udbrændthed og forværret sundhedstilstand. Den overordnede påstand i denne bog er, at det er muligt at komme arbejdsmiljøproblemerne i forkøbet ved at fokusere på de menneskelige ressourcer i organisationen. For at skabe et positivt...... for arbejdsmiljøforskningen. Temaer der behandles inden for dette perspektiv er: Globalisering og arbejdsmiljø, samspillet mellem menneskearbejdet og dets arbejdsmiljøproblemer, sygefravær og arbejdsmiljø, arbejdsmiljøseminarer og motivation, arbejdsværdiorientering i arbejdsmiljø- og personalearbejde, dødens arbejde samt...

Environmental, Social og Governance og aktivt ejerskab

DEFF Research Database (Denmark)

Bechmann, Ken L.

2016-01-01

Den første artikel i dette nummer af Finans/Invest diskuterer Environmental, Social og Governance (ESG) i forhold til at skabe forbedret aktieafkast. Den tredje artikel går i dybden med udviklingen i danske børsnoterede bankers corporate governance karakteristika hen over bankkrisen. ESG og...

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

Science.gov (United States)

Ho, Jessica S.; Geske, Grant D.; Blackwell, Helen E.; Ruby, Edward G.

2014-01-01

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

Pesticiders vekselvirkning med jordbearbejdning og gødskning. Effekter på fauna og mikroflora, og på udvalgte økosystem-funktioner

DEFF Research Database (Denmark)

Petersen, S O; Kjærgaard, Charlotte; Elsgaard, Lars

Dette projekt har undersøgt vekselvirkninger mellem to pesticider og hhv. jordbearbejdning (direkte sået eller pløjet jord) og gødskning (handels- eller husdyrgødning) med hensyn til effekter på regnorme, mikroleddyr og mikrobielle indikatorer og på udvalgte økosystem-tjenester (funktioner)....

Landbruget og kulturlandskabet

DEFF Research Database (Denmark)

Rentz-Petersen, Nee

2011-01-01

Denne historiske oversigt beskriver, hvordan landbrugets bygninger og driftsformer gennem de sidste 6000 år har tilført kulturlandskabet en dynamik og stadig forvandling. Materialet er udvalgt efter nedslagsmetoden – landbrugets udvikling beskrives i spring, når signifikante ændringer og nyskabel...

Indre spenninger og ytre press

DEFF Research Database (Denmark)

Ibsen, Bjarne

2011-01-01

Anmeldelse af bogen 'Norsk idrett. Indre spenninger og ytre press' redigeret af Dag Vidar Hanstad, Gunnar Breivik, Mari Kristin Sisjord og Hans B. Skaset og udgivet af forlaet akilles.......Anmeldelse af bogen 'Norsk idrett. Indre spenninger og ytre press' redigeret af Dag Vidar Hanstad, Gunnar Breivik, Mari Kristin Sisjord og Hans B. Skaset og udgivet af forlaet akilles....

Analyse og design af produktionssystemer

DEFF Research Database (Denmark)

Johansen, John; Riis, Jens Ove; Arlbjørn, Jan Stentoft

lys, men til vores store glæde og overraskelse har vi erfaret, at dele af materialet stadigvæk er anvendt på en del ingeniør- og økonomiuddannelser i Danmark. Nogle af de tanker og metoder som blev udviklet i ViPSprogrammet har overlevet og opfattes fortsat som relevante og anvendelige også til...

Inger og Johannes Exner

DEFF Research Database (Denmark)

Jensen, Thomas Bo

Monografi om Inger og Johannes Exners arkitektur. Bogen behandler indgående Exners inspirationer samt deres teorier vedrørende kirkearkitektur og restaurering.......Monografi om Inger og Johannes Exners arkitektur. Bogen behandler indgående Exners inspirationer samt deres teorier vedrørende kirkearkitektur og restaurering....

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

Science.gov (United States)

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

2017-12-01

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

Fluorescence and NMR spectroscopy together with molecular simulations reveal amphiphilic characteristics of a Burkholderia biofilm exopolysaccharide.

Science.gov (United States)

Kuttel, Michelle M; Cescutti, Paola; Distefano, Marco; Rizzo, Roberto

2017-06-30

Biofilms are a collective mode of bacterial life in which a self-produced matrix confines cells in close proximity to each other. Biofilms confer many advantages, including protection from chemicals (including antibiotics), entrapment of useful extracellular enzymes and nutrients, as well as opportunities for efficient recycling of molecules from dead cells. Biofilm matrices are aqueous gel-like structures composed of polysaccharides, proteins, and DNA stabilized by intermolecular interactions that may include non-polar connections. Recently, polysaccharides extracted from biofilms produced by species of the Burkholderia cepacia complex were shown to possess clusters of rhamnose, a 6-deoxy sugar with non-polar characteristics. Molecular dynamics simulations are well suited to characterizing the structure and dynamics of polysaccharides, but only relatively few such studies exist of their interaction with non-polar molecules. Here we report an investigation into the hydrophobic properties of the exopolysaccharide produced by Burkholderia multivorans strain C1576. Fluorescence experiments with two hydrophobic fluorescent probes established that this polysaccharide complexes hydrophobic species, and NMR experiments confirmed these interactions. Molecular simulations to model the hydrodynamics of the polysaccharide and the interaction with guest species revealed a very flexible, amphiphilic carbohydrate chain that has frequent dynamic interactions with apolar molecules; both hexane and a long-chain fatty acid belonging to the quorum-sensing system of B. multivorans were tested. A possible role of the non-polar domains of the exopolysaccharide in facilitating the diffusion of aliphatic species toward specific targets within the biofilm aqueous matrix is proposed. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

Tegn og gerninger

DEFF Research Database (Denmark)

Togeby, Ole

2005-01-01

Begrebet 'tegn' eller 'repræsentation' defineres som noget der for nogen angiver noget som det er udformet til at angive. Der skelnes dernæst mellem analoge og digitale repræsentationer, blandingsrepræsentationer og komplekse repræsentationer.......Begrebet 'tegn' eller 'repræsentation' defineres som noget der for nogen angiver noget som det er udformet til at angive. Der skelnes dernæst mellem analoge og digitale repræsentationer, blandingsrepræsentationer og komplekse repræsentationer....

Formalsproglig kompetence og IT

DEFF Research Database (Denmark)

Ambjørn, Lone

2002-01-01

Sproglæringsteoretisk værktøj til udvikling af IT-støttede materialer og programmer inden for grammatisk og leksikalsk kompetence......Sproglæringsteoretisk værktøj til udvikling af IT-støttede materialer og programmer inden for grammatisk og leksikalsk kompetence...

Supervisionens materiale og proces

DEFF Research Database (Denmark)

Jacobsen, Claus Haugaard

2007-01-01

Kapitlet handler om supervisionens materiale og proces, dvs. spørgsmålene om, hvilket materiale supervisanden skal medbringe til supervision, hvordan det skal fremlægges, og hvordan valg af materiale og metode gensidigt indvirker på hinanden og på supervisionsprocessen. Som de mest anvendte metoder...

Sport og etik

DEFF Research Database (Denmark)

Møller, Rasmus Bysted

Sportsidealismens grundsyn på forholdet mellem sport og moral har længe domineret sportsetikken. Opfattelsen, der går ud på, at sporten udgør frugtbar jord for dyrkelse af et moralsk sindelag, fordi sporten indeholder en moralsk dimension i kraft af sin egen-natur, understøttes ikke af den...... forholdet mellem sport og moral kom således til at bekræfte og delvist forklare empirien på området. Endeligt kunne sportsidealismens hovedtese tilbagevises, for så vidt at den omhandler forholdet mellem sport og moral i dette sidste ords moderne betydning. Dette skete i artiklens afsluttende fjerde afsnit......, hvor forskellen mellem antik og moderne etik blev tydeliggjort. På baggrund af den præsenterede undersøgelse af forholdet mellem sport og moral kan vi konkludere, at sporten isoleret set ikke egner sig som arnested for udviklingen af et moralsk sindelag, idet sporten ikke indeholder den af...

Professionsetik indefra og udefra

DEFF Research Database (Denmark)

Dige, Morten

& Childress' fire principper for medicinsk etik: godgørenhed, ikke-skadevolden, retfærdighed og respekt for autonomi. Mange organisationers og professioners værdigrundlag er bygget op om værdier som bedst lader sig forstå som denne type: respekt, ligeværdighed, troværdighed, omsorg, tillid, værdighed osv. Den....... Jeg finder en besindelse på og oprustning af denne etiske kerne af afgørende betydning i en tid, hvor hjælpeprofessionernes autonomi og troværdighed sættes under pres af markedsdrevne og bureaukratiske logikker ("New Public Managment"). Jeg illustrerer dette med cases fra socialt arbejde og...

Møder og konferencer

DEFF Research Database (Denmark)

Ravn, Ib

2008-01-01

Beskæftiger man sig professionelt med møder og konferencer, er det nyttigt at have gjort sig klart, hvad man forstår ved disse begreber. I denne artikel prøver jeg at definere de to ord, og jeg giver eksempler på forskellige typiske møder og konferencer. Udgivelsesdato: 2008......Beskæftiger man sig professionelt med møder og konferencer, er det nyttigt at have gjort sig klart, hvad man forstår ved disse begreber. I denne artikel prøver jeg at definere de to ord, og jeg giver eksempler på forskellige typiske møder og konferencer. Udgivelsesdato: 2008...

Medier - love og regler

DEFF Research Database (Denmark)

Jørgensen, Oluf

Den mest komplette samling af de love og regler, der har størst betydning for medier og journalistik i Danmark. Samlingen ajourføres, når Folketinget lukker i juni, og alle nye bestemmelser dermed er kendt. Ændringer siden sidste udgave: Lovbogen er ajourført med ændringer i arkivloven, miljøoply......Den mest komplette samling af de love og regler, der har størst betydning for medier og journalistik i Danmark. Samlingen ajourføres, når Folketinget lukker i juni, og alle nye bestemmelser dermed er kendt. Ændringer siden sidste udgave: Lovbogen er ajourført med ændringer i arkivloven...

Motivation og æstetik

DEFF Research Database (Denmark)

Austring, Bennyé D.; Sørensen, Merete

2007-01-01

I de tilfælde, hvor læringen også skaber fokus på barnet og inkluderer dets udtryksbehov, er motivation umiddelbart nem at etablere. Frem for at "bogliggøre" læringen yderligere bør vi i stedet i højere grad udnytte æstetikkens fascinationskraft og udtryksstyrke som motivationsfaktor.......I de tilfælde, hvor læringen også skaber fokus på barnet og inkluderer dets udtryksbehov, er motivation umiddelbart nem at etablere. Frem for at "bogliggøre" læringen yderligere bør vi i stedet i højere grad udnytte æstetikkens fascinationskraft og udtryksstyrke som motivationsfaktor....

Menneskets hjerne og personlighed

DEFF Research Database (Denmark)

Mathiesen, Birgit Bork; Thomsen, Marianne Skovgaard

2017-01-01

været stigende, siden en gruppe af danske psykiatere og psykologer i 1988 afholdt den første internationale kongres om personlighedsforstyrrelser i København og dannede Institut for Personlighedsteori og Psykopatologi (IPTP). Da IPTP afholdt sit 25-års jubilæum, besluttede man at udgive en bog, der...... indeholder al den viden, man har opnået på området gennem de seneste 25 års forskning. Resultatet er Personlighed og personlighedsforstyrrelser. En grundbog. Bogens redaktører er professor Erik Simonsen og lektor Birgit Bork Mathiesen, der er henholdsvis formand og næstformand for IPTP. De har begge gennem...

Etnicitet og udsathed

DEFF Research Database (Denmark)

Tireli, Üzeyir

2015-01-01

Kapitlet beskæftiger sig med relationen mellem udsathed og etnicitet og bearbejder spørgsmålet om, hvorfor nogle grupper defineres som udsatte, uden et egentligt empirisk belæg for kausalitetsforhold mellem etnicitet og udsathed. Desuden gives en forklaring på forskellighed i udsathed grupperne i...

Person og Rolle

DEFF Research Database (Denmark)

Szatkowski, Janek

2011-01-01

Distinktionen mellem person og rolle forslås som grundlag for et præcist og anlytisk anvendeligt begreb om performativitet. Begrebet tager sigte på at beskrive enkeltindividers og gruppers kommunikation med henblik på hvordan kommunikation etableres. Performativitet gør det muligt at iagttage den...

Forsegling og symbiose

DEFF Research Database (Denmark)

Bjerregaard Jensen, Lotte

universelle løsninger, men mere dybtgående ved grundlaget for vor videnskabelige og tekniske kultur. Bjerregaard taler i sin bog om komp!ekset kartesiansk dualisme, naturvidenskab og industrialisme. Op imod denne ”modernitet” sætter hun naturromantikken og etablerer en forbindelse mellem det ”pittoreske...

Konstruktion, rekonstruktion og strategiske essentialismer

DEFF Research Database (Denmark)

Borup, Jørn

2007-01-01

Essentialisme og dennes misrepræsentation, etnocentrisme og hegemoni (som afsløret af eksempelvis postkoloniale studier) er et af de vigtigste kritikpunkter mod før-postmoderne religions- og kulturstudier. Denne artikel hævder, at konstruktioner ("opfindelser") og essentialismer er naturlige og...

Quickplace - anvendelse og muligheder

DEFF Research Database (Denmark)

Bojesen, Jakob Cloos

beskrives status og fremtidsudsigter for brugen af systemet på Aalborg Universitet. De opnåede erfaringer med emner som mulige anvendelsesområder, organisatorisk forankring, support og tilretning af systemet beskrives, og rapporten kan således inspirere og informere andre, som står over for at vælge en...

Xerostomi og nedsat spytsekretion

DEFF Research Database (Denmark)

Jensen, Siri Beier; Dynesen, Anja Weirsøe; Pedersen, Anne Marie Lynge

2011-01-01

Forekomst og årsager til xerostomi og nedsat spytsekretion ' Xerostomi er defineret som den subjektive følelse af mundtørhed og er som oftest en følge af nedsat eller manglende spytsekretion. Xerostomi kan dog også forekomme uden objektiv dysfunktion af spytkirtlerne. De grundlæggende årsager til...

Musikvideo og tilskuer: Fjernsyn, ideologi og drøm

Directory of Open Access Journals (Sweden)

Marsha Kinder

1987-08-01

Full Text Available Denne artikel af Marcha Kinder er allerede en klassiker. I næsten al litteratur om musikvideoer henvises der til den - også herhjemme. Det er især hendes typologi over musikvideoerne, som der refereres til, mens artiklens percep- tionspsykologiske sammenligninger mellem musikvideoer og drømme næsten ikke har været inddraget i debatten. Marcha Kinder har arbejdet med medier i en årrække og udgav sammen med Beverle Houston "Self and Cinema A Transformalist Perspective" /(Redgrave Publishing Vompany i 1980. Artiklen "Musikvideo og tilskuer" er oversat i sin helhed fra "Music Video and the Spectator": Television, Ideology and Dream, Film Quarterly, vol. XXXVIII, no. I 1984 af Jim Høyer.

Samtidskunst og migration

DEFF Research Database (Denmark)

Petersen, Anne Ring

2010-01-01

"Samtidskunst og migration. En oversigt over faglitteraturen" er en forskningsoversigt der gør status over hvad der hidtil er skrevet inden for det kunsthistoriske område om vor tids billedkunst og migration som politisk, socialt og kulturelt fænomen, primært i forbindelse med immigration til...

Internationalisering og sprogpolitik

DEFF Research Database (Denmark)

Rasmussen, Palle

2008-01-01

Internationaliseringen af uddannelse og erhverv sker helt overvejende via det engelske sprog, som kommer til at dominere mere og mere. Som modvægt hertil er det vigtigt at danske forskere og universiteter gør en bevidst indsats for at opretholde dansk som videnskabssprog. Derimod er det mere prob...

Personlighed og motivation

DEFF Research Database (Denmark)

Olsen, Jan Brødslev

2017-01-01

ses som forskelle i deres personlighed og i deres motivation. Kapitlet er opbygget således, at ganske kort præciseres først de to begreber, personlighed og motivation, hvorefter udvalgte teoretiske perspektiver på personlighed og motivation tages op. Til sammen vil disse bidrage til at besvare...

Den danske samfundsudvikling 1848-2012 og marxistisk, neoklassisk, keynesiansk, monetaristisk og nykeynesiansk teori

DEFF Research Database (Denmark)

Madsen, Poul Thøis

Efter i adskillige år at have undervist ud fra andres bøger og efter mange tilløb besluttede forfatteren sig for at skrive sin egen forskningsbaserede bog til Det Samfundsvidenskabelige Fællessemester, som dækker fem lektioner om den politiske økonomis historie og den danske økonomiske udvikling........ Ambitionen har været at udarbejde en kort appetitvækker, der gør, at studerende får et overblik og forstår nogle basale sammenhænge og får lyst til at vide mere om økonomisk teori, dansk og international økonomi og ikke mindst debatterne herom....

Hund og menneske imellem

DEFF Research Database (Denmark)

Hovmark, Henrik

2009-01-01

og menneske imellem? Denne artikel beskriver hvordan hundelivet bliver udfoldet i Ordbog over det danske Sprog (ODS), Den Danske Ordbog (DDO) og Ømålsordbogen (ØMO). Fælles for ODS, DDO og ØMO er at de er videnskabeligt beskrivende ordbøger. Det betyder ideelt set at man indsamler og beskriver...

Designprocesser og digital produktion:

DEFF Research Database (Denmark)

Pilgaard, Michal; Lembcke, Steen

Der er fokus på Fab-Labs som ramme for en social læringskontekst i folkeskolen, hvor elever sammen med lærere og pædagoger får mulighed for at udforske teknologier og fremstille digitale produkter og produktioner. I læringsmiljøet hvor designprocessen og den digitale fabrikation udfoldes...

Mat, måltid og moral - hvordan spise rett og riktig?

OpenAIRE

Bugge, Annechen Bahr

2015-01-01

Matforbruk er i økende grad blitt et spørsmål om ansvar og omsorg. I den nyliberalistiske retorikken blir forbrukerne hele tiden oppfordret til å handle sunne, naturlige, økologiske, etiske produkter, samt å unngå billig, masseprodusert mat (hvor gjerne sukker, fett og salt er hovedingredienser). Det er ikke bare ansett som dårlig for kroppen, men også for våre omgivelser. Gjennom media, ekspertuttalelser, helse-/miljøkampanjer, produktlanseringer, reklame, dietter osv. blir også forbrukerne ...

Mellem bureaukrati og profession

DEFF Research Database (Denmark)

Sandholm, Niels; Nielsen, Ulla Søbjerg; Nielsen, Iben Husted

2015-01-01

Forhold mellem profession og bureaukrati undersøges med afsæt i to cases, sygeplejersker på hospital og sygehussocialrådgivere. Det empiriske materiale er fokusgruppeinterviews med to grupper af sygeplejersker og to grupper af socialrådgivere. Perspektivet er mikrosociologisk og der trækkes på an....... Et markant fund er, at mens socialrådgiverne fremstår som overvejende loyale overfor klienter, så udtrykker sygeplejerskerne en højere grad af loyalitet med organisatoriske mål og logikker....

Om standpunkter, interesser og behov

DEFF Research Database (Denmark)

Adrian, Lin

2008-01-01

Begreberne standpunkter, interesser og behov er hyppigt anvendte begreber i mæglingslitteraturen. Deres betydning tages ofte for givet og underkastes sjældent selvstændig definition og analyse. Artiklen undersøger begrebernes oprindelse og betydning og diskuterer deres rolle i mæglingspraksis. Ar...

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

Science.gov (United States)

Defoirdt, Tom; Sorgeloos, Patrick

2012-12-01

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.

Herbart om oppdragelse, formbarhet og takt

Directory of Open Access Journals (Sweden)

Lars Løvlie

2015-04-01

Full Text Available Jeg presenterer her en analyse og tolkning av Herbarts syn på oppdragelse og danning, med feste i to av hans begreper: formbarhet – Bildsamkeit – og takt. Det første kaster lys over forholdet mellom lærer og elev, det andre først og fremst over forholdet mellom teori og praksis. For ham, som for forgjengeren Immanuel Kant, dreiet det seg om subjektivitet og frihet, eller mer konkret: Hvordan oppdra til autonomi der det også kreves tvang? Så vidt jeg kan se, bruker Herbart de to grunnbegrepene nettopp til å bestemme det paradoksale og uferdige forholdet mellom frihet og tvang. Han forklarer det som et åpent forhold eller relasjon som ikke har en bestemt begynnelse og heller ikke en bestemt konklusjon. Verken tradisjon eller vitenskap kan ved seg selv realisere dette råderommet. Han tenker seg et frirom der kunnskap, intuisjon og skjønn spiller på lag i oppdragelsen. Tradisjonen henger gjerne igjen i gamle fordommer, vitenskapen fanges i teori og abstrakt skjema, og ingen av dem dekker de unike situasjonene som nyskaper forholdet mellom voksne og barn. Herbart stilte seg åpen til spørsmål som ikke løses ved styring og kontroll, og spør implisitt om ikke vi også kan gjøre det samme.

Følelse og fornuft

DEFF Research Database (Denmark)

Busk, Malene

2007-01-01

supplerer reelt hinanden, mens det nedbryder og modarbejder udviklingen af konstruktive former for følelse og fornuft: Tro kræver at fornuften tier og kynismen kræver at følsomheden afstumpes. En af epokens udfordringer er netop at gendefinere følelse og fornuft så begreberne ikke indebærer den systematiske...

Orientering og banelægning med Google Earth og Condes

DEFF Research Database (Denmark)

Jørgensen, Henrik Taarsted; Piaster, Thomas Gabriel

2011-01-01

Et e-læringsmodul på Danmarks undervisningsportal, som handler om hvordan man kan arbejde med banelægning indenfor o-løb. Med udgangspunkt i de to gratisprogrammer Google Earth og Condes lærer man gennem modulet, hvordan man indtegner poster og hvordan eleverne kan gøre det samme.......Et e-læringsmodul på Danmarks undervisningsportal, som handler om hvordan man kan arbejde med banelægning indenfor o-løb. Med udgangspunkt i de to gratisprogrammer Google Earth og Condes lærer man gennem modulet, hvordan man indtegner poster og hvordan eleverne kan gøre det samme....

Fænomenologi og bevægelse

DEFF Research Database (Denmark)

Dupont, Søren

Dette paper forsøger at trække nogle linjer til relationerne mellem fænomenologi og bevægelse, men også tid, rum og sted. Teoretikerne er Maurice Merleau-Ponty, Hannah Arendt og Daniel Stern. Til sidst diskuteres forholdet mellem fænomenologi og metode.......Dette paper forsøger at trække nogle linjer til relationerne mellem fænomenologi og bevægelse, men også tid, rum og sted. Teoretikerne er Maurice Merleau-Ponty, Hannah Arendt og Daniel Stern. Til sidst diskuteres forholdet mellem fænomenologi og metode....

A novel compound to maintain a healthy oral plaque ecology in vitro

NARCIS (Netherlands)

Janus, M.M.; Crielaard, W.; Zaura, E.; Keijser, B.J.; Brandt, B.W.; Krom, B.P.

2016-01-01

Objective: Dental caries is caused by prolonged episodes of low pH due to acid production by oral biofilms. Bacteria within such biofilms communicate via quorum sensing (QS). QS regulates several phenotypic biofilm parameters, such as biofilm formation and the production of virulence factors. In

Handling Neighbor Discovery and Rendezvous Consistency with Weighted Quorum-Based Approach.

Science.gov (United States)

Own, Chung-Ming; Meng, Zhaopeng; Liu, Kehan

2015-09-03

Neighbor discovery and the power of sensors play an important role in the formation of Wireless Sensor Networks (WSNs) and mobile networks. Many asynchronous protocols based on wake-up time scheduling have been proposed to enable neighbor discovery among neighboring nodes for the energy saving, especially in the difficulty of clock synchronization. However, existing researches are divided two parts with the neighbor-discovery methods, one is the quorum-based protocols and the other is co-primality based protocols. Their distinction is on the arrangements of time slots, the former uses the quorums in the matrix, the latter adopts the numerical analysis. In our study, we propose the weighted heuristic quorum system (WQS), which is based on the quorum algorithm to eliminate redundant paths of active slots. We demonstrate the specification of our system: fewer active slots are required, the referring rate is balanced, and remaining power is considered particularly when a device maintains rendezvous with discovered neighbors. The evaluation results showed that our proposed method can effectively reschedule the active slots and save the computing time of the network system.

Handling Neighbor Discovery and Rendezvous Consistency with Weighted Quorum-Based Approach

Directory of Open Access Journals (Sweden)

Chung-Ming Own

2015-09-01

Full Text Available Neighbor discovery and the power of sensors play an important role in the formation of Wireless Sensor Networks (WSNs and mobile networks. Many asynchronous protocols based on wake-up time scheduling have been proposed to enable neighbor discovery among neighboring nodes for the energy saving, especially in the difficulty of clock synchronization. However, existing researches are divided two parts with the neighbor-discovery methods, one is the quorum-based protocols and the other is co-primality based protocols. Their distinction is on the arrangements of time slots, the former uses the quorums in the matrix, the latter adopts the numerical analysis. In our study, we propose the weighted heuristic quorum system (WQS, which is based on the quorum algorithm to eliminate redundant paths of active slots. We demonstrate the specification of our system: fewer active slots are required, the referring rate is balanced, and remaining power is considered particularly when a device maintains rendezvous with discovered neighbors. The evaluation results showed that our proposed method can effectively reschedule the active slots and save the computing time of the network system.

Interference of quorum sensing in urinary pathogen Serratia marcescens by Anethum graveolens.

Science.gov (United States)

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. © FEMS 2015. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

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

Directory of Open Access Journals (Sweden)

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.

Isolation and molecular characterization of biofouling bacteria and profiling of quorum sensing signal molecules from membrane bioreactor activated sludge.

Science.gov (United States)

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

2014-02-04

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.

Mette og Murakami

DEFF Research Database (Denmark)

Roesgaard, Marie Højlund

2017-01-01

Chiro og Heksene, mange ved at manga er japanske tegneserier, Nationalmuseet laver udstilling om cosplay og opstiller en purikura-maskine, der kan lave billeder af gæsterne i nuttede, storøjede udgaver – så jo, Japan er synlig i Danmark. Mindre kendt er det, at Japan og Danmark allerede under Christian...

Videnssamfundet i det 12. og 13. århundrede. Forskning og formidling

DEFF Research Database (Denmark)

Bloch, David; Ebbesen, Sten

Bogen undersøger de metoder og de litterære genrer, ved hvilke middelalderens tænkere bedrev og formidlede deres forskning. Den argumenterer for, at de havde et særdeles velfungerende system, der sikrede muligheder for god formidling til de forskellige målgrupper.......Bogen undersøger de metoder og de litterære genrer, ved hvilke middelalderens tænkere bedrev og formidlede deres forskning. Den argumenterer for, at de havde et særdeles velfungerende system, der sikrede muligheder for god formidling til de forskellige målgrupper....

Synthetic quorum sensing in model microcapsule colonies

Science.gov (United States)

Shum, Henry; Balazs, Anna C.

2017-08-01

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

Mellem medicin og moral

DEFF Research Database (Denmark)

Eriksen, Sidsel

2002-01-01

Den dødsdømte Peder Worms sidste tid før skafottet i 1830'ernes København set ud en medicinsk synsvinkel repræsteret ved fængselslægen og frenologen (kraniesamleren) Carl Otto og en teologisk synsvinkel set ud fra fængselslægen og rationalisten C.F. Visbye og dennes samtaler med fangen....

Tårnet og territoriet

DEFF Research Database (Denmark)

Munk, Kasper Green

2016-01-01

Tyskland står midt i en kulturkamp, der handler om flygtninge og indvandrere, og hvor arven fra nazismen og kommunismen spiller en meget stor rolle. En rejse til Dresden med litteraturen ved hånden kan gøre os klogere på baggrunden for, hvad der foregår. Det handler om sammenstød mellem drøm og v...

Kildebankemne: Slaveriet og Vestindien

DEFF Research Database (Denmark)

Sørensen, Christina Louise; Poulsen, Jens Aage; Peters, Rikke Louise Alberg

2017-01-01

Den digitale kildebank består af flere end 130 kilder, der er inddelt i de 12 temaer. I hvert tema stilledes der mellem 10-15 kilder til rådighed om slavehandelen, slavernes liv og arbejde på De Dansk Vestindiske Øer og meget mere. Til læremidlet er også udviklet lærervejledninger, opgaver og tri...

Yrkesstolthet og frafall i kokkeyrket

Directory of Open Access Journals (Sweden)

Bjørn Eben

2018-01-01

Full Text Available Hvorfor vurderer så mange kokker å skifte yrke når det samtidig viser seg at mange også er stolte av yrket sitt (Spetalen, Eben & Jahnlu, 2016; St. Olav Hospital, 2013, Tidemann & Myklebust, 2005? Denne artikkelen vil rette oppmerksomheten på mulige årsaker til dette, og hvorfor restaurantkokker vurderer å endre arbeidsplass eller yrkesmulighet. Restaurantbransjen er i rask utvikling og befolkningen spiser stadig oftere på restaurant (Bugge & Lavik, 2007. Samtidig synker rekruteringen til kokkeyrket (Sundquist, 2016. Det er derfor viktig å drøfte hvilke faktorer som har betydning for at restaurantkokker forlater yrket etter forholdsvis kort tid.Problemstillingen er; Hvorfor vurderer så mange kokker å skifte yrke når de er så stolte av yrket sitt?I denne artikkelen er det gjennomført en reanalyse av grunnlagsmaterialet som ble presentert i rapporten «Yrkesutøvelse i restaurant og matfagene – Arbeidsoppgaver, prioriteringer og forskjeller» (Spetalen, Eben & Jahnlu, 2016. I tillegg til denne univariate analysen har jeg også sammenliknet gjennomsnitt og testet hypoteser ved hjelp av T-test og ANOVA i SPSS (Johannessen, 2009; Pallant, 2013.  Studenter ved bachelorutdanningen i Restaurant og matfag, kull 2013 ved Høgskolen i Oslo og Akershus, tok utgangspunkt i dataene fra Spetalen et al. (2016 i sine bacheloroppgaver. I samarbeid med tre studenter er det gjennomført kvalitative intervjuer med til sammen 23 nåværende og tidligere kokker. For å forklare dataene har jeg trukket inn det organisasjonsteoretiske begrepet «turnover» siden dette er et tydelig problem i restaurantbransjen. Faktorer som tiltrekker og frastøter medarbeideren i forhold til yrket, er også med i diskusjonen for å forklare funnene (Lashley, 2000; Brochs-Haukedal, 2010; Kuvås, 2013. Med bakgrunn i funnene fra de kvalitative intervjuene kan man anta at følgende årsaker veier tungt når kokker aktivt søker annen yrkeskarriere:Ledelse – mangel p

Forskel og lighed - Hannah Arendts bidrag til uddannelsespolitik og pædagogik i det multikulturelle samfund

DEFF Research Database (Denmark)

Larsen, Kirsten

2015-01-01

Artiklen analyserer de to tekster Hannah Arendt har skrevet om uddannelsespolitik og pædagogik. På baggrund af den ene af teksternes forsvar for racesegregering og - diskrimination i den offentlige grundskole, stilles spørgsmålet om det er muligt at være både racist og, som Arendt, jøde flygtet fra...... nazismen. Svaret er ja; ved at skelne skarpt mellem på den ene side filosofi og på den anden side både egen livshistorie og praktisk (uddannelses)politik og pædagogik, er det muligt for Arendt at tænke racialiserende og socialt og institutionelt at racediskriminere. Men artiklen peger også på at der andre...... steder i Arendts værk kunne være inspirationer til en mangfoldig skole i det senmoderne multietniske og multikulturelle samfund, også det aktuelle danske...

A broad range quorum sensing inhibitor working through sRNA inhibition

DEFF Research Database (Denmark)

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

2017-01-01

that the repressing effect of ajoene on quorum sensing occurs by inhibition of small regulatory RNAs (sRNA) in P. aeruginosa as well as in Staphylococcus aureus, another important human pathogen that employs quorum sensing to control virulence gene expression. Using various reporter constructs, we found that ajoene......-spectrum compounds transcending the Gram negative-positive borderline....

Potentialitet og optimering

DEFF Research Database (Denmark)

Hamre, Bjørn

. Afhandlingen kan både ses som et bidrag til eksisterende governmentality studier inden for uddannelse og som et bidrag til forskning i specialpædagogik. Optimering ses som en type rationalitetsform og magtudøvelse, der defi nerer problemforståelser i nutiden og sætter et skel mellem den adfærd, der inkluderes...

Adoption og diskrimination

DEFF Research Database (Denmark)

Henze-Pedersen, Sofie

2017-01-01

I denne undersøgelse har vi gennemført interview med både internationalt adopterede og dansk adopterede og har derfor mulighed for at nuancere adopteredes oplevelser af diskrimination. Det bliver således muligt at belyse, hvornår og på hvilken måde det at have et etnisk udseende, der adskiller si...

Klima og turisme

DEFF Research Database (Denmark)

Ren, Carina Bregnholm

2014-01-01

Denne artikel præsenterer en række koblinger mellem klima og turisme med det formål at pege på, hvorledes klima og turisme i fremtiden kan tænkes. Jeg beskriver, hvorledes man i turismeforskningen har fokuseret på at blotlægge særligt to kausale forbindelser mellem klima og turisme, nemlig hvorda...

WTO og skatteret

DEFF Research Database (Denmark)

Sørensen, Karsten Engsig

2005-01-01

Artiklen analyserer hvordan WTO-retten, særligt GATT-, GATS- og subsidieaftalen, kan påvirke indholdet af national skatteret. Udover en drøftelse af princippet om national behandling og mest begunstigelsesprincippet drøftes hvordan subsidieaftalen kan påvirke de nationale principper om global con...... contra territorial beskatning og reglerne om transfer pricing....

Antibacterial, anti-swarming and anti-biofilm formation activities of Chamaemelum nobile against Pseudomonas aeruginosa.

Science.gov (United States)

Kazemian, Hossein; Ghafourian, Sobhan; Heidari, Hamid; Amiri, Pouya; Yamchi, Jalil Kardan; Shavalipour, Aref; Houri, Hamidreza; Maleki, Abbas; Sadeghifard, Nourkhoda

2015-01-01

Chamomile (Chamaemelum nobile) is widely used throughout the world, and has anti-inflammatory, deodorant, bacteriostatic, antimicrobial, carminative, sedative, antiseptic, anti-catarrhal, and spasmolytic properties. Because of the increasing incidence of drug-resistant bacteria, the development of natural antibacterial sources such as medical herbs for the treatment of infectious diseases is necessary. Extracts from different plant parts such as the leaves, flowers, fruit, and bark of Combretum albiflorum, Laurus nobilis , and Sonchus oleraceus were found to possess anti-quorum sensing (QS) activities. In this study, we evaluated the effect of C. nobile against Pseudomonas aeruginosa biofilm formation. The P. aeruginosa samples were isolated from patients with different types of infection, including wound infection, septicemia, and urinary tract infection. The flowers of C. nobile were dried and the extract was removed using a rotary device and then dissolved in dimethyl sulfoxide at pH 7.4. The microdilution method was used to evaluate the minimum inhibitory concentration (MIC) of this extract on P. aeruginosa , and biofilm inhibition was assayed. Eighty percent of the isolated samples (16/20) could form a biofilm, and most of these were isolated from wound infections. The biofilm inhibitory concentration of the C. nobile extract was 6.25-25mg/ml, whereas the MIC was 12.5-50mg/ml. The anti-QS property of C. nobile may play an important role in its antibacterial activity, thus offering an additional strategy in the fight against bacterial infections. However, molecular investigation is required to explore the exact mechanisms of the antibacterial action and functions of this phytocompound.

Test og prøvelser

DEFF Research Database (Denmark)

Test i forskellige former og afskygninger spiller i dag en markant rolle indenfor mange forskellige områder i samfundet. De bliver anvendt til at evaluere og bedømme børn, unge og voksne i forskellige kontekster og med forskellige formål og konsekvenser. I mange tilfælde er der tale om test, hvis...... udfald – direkte eller indirekte - vil kunne få vidtrækkende følger for dem, der testes. Test kan sætte sig spor livet igennem og udsætte de testede for prøvelser, idet de påvirker deres selvopfattelser og udstikker bestemte livsbaner og muligheder. Med afsæt i uddannelsesområdet sætter denne bog fokus...... på test i historisk og nutidig belysning. Den behandler spørgsmål som: Hvordan kom test ind i feltet? Hvilke test anvendes? Hvem tester man? Hvorfor vil man gerne teste? Hvad er de direkte og indirekte sociale konsekvenser af at anvende test? Besvarelsen af disse spørgsmål kan på den ene side bidrage...

Cases om organisation og ledelse

DEFF Research Database (Denmark)

Sinding, Knud; Bøllingtoft, Anne

Cases gør det muligt at øve sig og giver mange forskellige problemstillinger at arbejde med, end de fleste kommer i nærheden af i deres arbejde. Samlingen her passer til en bred vifte af organisationsfag. Der er navnløse og navngivne, store og små, offentlige og private, kendte og ukendte. Casene...

Iron is a signal for Stenotrophomonas maltophilia biofilm formation, oxidative stress response, OMPs expression and virulence

Directory of Open Access Journals (Sweden)

Carlos Adrian Garcia

2015-09-01

Full Text Available Stenotrophomonas maltophilia is an emerging nosocomial pathogen. In many bacteria iron availability regulates, trough the Fur system, not only iron homeostasis but also virulence. The aim of this work was to assess the role of iron on S. maltophilia biofilm formation, EPS production, oxidative stress response, OMPs regulation, quorum sensing (QS, and virulence. Studies were done on K279 and its isogenic fur mutant F60 cultured in the presence or absence of dipyridyl. This is the first report of spontaneous fur mutants obtained in S. maltophilia. F60 produced higher amounts of biofilms than K279a and CLSM analysis demonstrated improved adherence and biofilm organization. Under iron restricted conditions, K279a produced biofilms with more biomass and enhanced thickness. In addition, F60 produced higher amounts of EPS than K279a but with a similar composition, as revealed by ATR-FTIR spectroscopy. With respect to the oxidative stress response, MnSOD was the only SOD isoenzyme detected in K279a. F60 presented higher SOD activity than the wt strain in planktonic and biofilm cultures, and iron deprivation increased K279a SOD activity. Under iron starvation, SDS-PAGE profile from K279a presented two iron-repressed proteins. Mass spectrometry analysis revealed homology with FepA and another putative TonB-dependent siderophore receptor of K279a. In silico analysis allowed the detection of potential Fur boxes in the respective coding genes. K279a encodes the QS diffusible signal factor (DSF. Under iron restriction K279a produced higher amounts of DSF than under iron rich condition. Finally, F60 was more virulent than K279a in the Galleria mellonella killing assay. These results put in evidence that iron levels regulate, likely through the Fur system, S. maltophilia biofilm formation, oxidative stress response, OMPs expression, DSF production and virulence.

Miljø- og arbejdsmiljøvenlig bygningsisolering af fåreuld og hør

DEFF Research Database (Denmark)

Hansen, Ernst Jan de Place

2001-01-01

Resume af rapport om miljø- og arbejdsmiljøvenlig bygningsisolering af fåreuld og hør og mulighederne for at starte en dansk produktion, udarbejdet af Esbensen Rådgivende Ingeniører, Sonnerup ECO Advise og HBC A/S under Energistyrelsens udviklingsprogram "Miljø- og arbejdsmiljøvenlig isolering"...

Følelser og sociologi

DEFF Research Database (Denmark)

Bo, Inger Glavind; Jacobsen, Michael Hviid

2017-01-01

En introduktion til bogen om følelsernes sociologi eller emotionssociologi - herunder om den ekspressive revolution og den affektive vending, om forskning i følelser og dens klassifikationer, tilgange, teorier og metoder....

Motivation, tilstedeværelse og fastholdelse

DEFF Research Database (Denmark)

Sørensen, Niels Ulrik; Hansen, Niels-Henrik Møller

Motivation, tilstedeværelse og fastholdelse undersøger, hvordan kursisterne oplever uddannelses- og læringskulturen på VUC og hf Nordjylland, og hvordan kulturen virker sammen med deres motivation, tilstedeværelse og fastholdelse. Der tages udgangspunkt i kursisternes egne beskrivelser og...... overvejelser, belyser en række problemstillinger, som har bred relevans for VUC og det almene uddannelsessystem. Med afsæt i kursisternes perspektiv anlægger evalueringen en konstruktiv valør i blikket på, hvad der fungerer godt og mindre godt på deres uddannelsesinstitution. I Motivation, tilstedeværelse og...... kan sætte ind på en række felter. Motivation, tilstedeværelse og fastholdelse er dermed aktuel for alle institutioner/skoler, hvor fravær og manglende motivation er et problem i hverdagen....

Diskursive dilemmaer i ledelse og organisation

DEFF Research Database (Denmark)

Frimann, Søren

2016-01-01

Kapitlet diskuterer de forskellige og ofte modstridende opfattelser af ledelse i organisationer og i ledelsesteorier. Forskellige diskurser om ledelse og organisation giver ofte udfordringer og dilemmaer i teori og i organisationers praksis samt mellem konsulentydelser, lederuddannelser og den...... praktiske virkelighed i organisationer. Dilemmaer viser sig ofte i konkret sprogbrug som semantiske modsætningspar, for eksempel udvikling-drift, management-leadership, individ-gruppe, forandring-stabilitet, kontrol-tillid, resultater-relationer, produkt-proces, direktiv leder-leder som facilitator....../coach/konsulent. Målet med dette kapitel er at skabe et overblik på et metaplan over forskellige paradigmer inden for organisation, kommunikation og ledelse, som ofte udgør den klangbund, dilemmaer og modsætninger udspringer af i teori og praksis.Først introduceres en case og empiriske eksempler fra lederes dilemmaer og...

Minnesmerker etter terrorangrep og massakrer : plassering, symbolisme og landskapets rolle i utformingen

OpenAIRE

Benum, Iselin Bennick

2013-01-01

Oppgaven tar for seg utforming av minnesmerker etter terrorangrep og massakrer, med hovedfokus på bruk av plassering, symbolisme og landskap. I dagens samfunn er det mye fokus på terrorangrep og massakrer, og minnesmerker etter slike hendelser har blitt mer vanlig. De siste 30 årene har utforming av minnesmerker endret seg. Tidligere bestod minnesmerker hovedsakelig av et monument, men etter åpningen av Vietnam Veterans Memorial i 1982 har utformingen av minnesmerker blitt mer abstrakt. M...

strong>Dannelse og dissonanserstrong>

DEFF Research Database (Denmark)

Frederiksen, Mons Bissenbakker

italesætter kønslige identiteter som fænomener, der be­ting­er elevers og læreres faglige præferencer og evner. Det vises også, at materialets itale­sættelse af etnicitet kendetegnes af, at faget anerkender og værdsætter det etnisk dif­ferentierede skolerum, men at det samtidig italesætter minoritetsetniske...

Læring og it

DEFF Research Database (Denmark)

  Antologien er et bidrag til didaktiske diskussioner om brug af f.eks. programpakker til sprogundervisning, præsentationsprogrammel og konferencesystemer på de videregående uddannelser. Antologien diskuterer ideen om, at multimediale medier og internettet kan understøtte læring, undervisning og ...... samarbejde ud fra konkrete eksempler på it-anvendelser, hvor fokus er på potentialer, barrierer og faldgruber....

S-aryl-L-cysteine sulphoxides and related organosulphur compounds alter oral biofilm development and AI-2-based cell-cell communication.

Science.gov (United States)

Kasper, S H; Samarian, D; Jadhav, A P; Rickard, A H; Musah, R A; Cady, N C

2014-11-01

To design and synthesize a library of structurally related, small molecules related to homologues of compounds produced by the plant Petiveria alliacea and determine their ability to interfere with AI-2 cell-cell communication and biofilm formation by oral bacteria. Many human diseases are associated with persistent bacterial biofilms. Oral biofilms (dental plaque) are problematic as they are often associated with tooth decay, periodontal disease and systemic disorders such as heart disease and diabetes. Using a microplate-based approach, a bio-inspired small molecule library was screened for anti-biofilm activity against the oral species Streptococcus mutans UA159, Streptococcus sanguis 10556 and Actinomyces oris MG1. To complement the static screen, a flow-based BioFlux microfluidic system screen was also performed under conditions representative of the human oral cavity. Several compounds were found to display biofilm inhibitory activity in all three of the oral bacteria tested. These compounds were also shown to inhibit bioluminescence by Vibrio harveyi and were thus inferred to be quorum sensing (QS) inhibitors. Due to the structural similarity of these compounds to each other, and to key molecules in AI-2 biosynthetic pathways, we propose that these molecules potentially reduce biofilm formation via antagonism of QS or QS-related pathways. This study highlights the potential for a non-antimicrobial-based strategy, focused on AI-2 cell-cell signalling, to control the development of dental plaque. Considering that many bacterial species use AI-2 cell-cell signalling, as well as the increased concern of the use of antimicrobials in healthcare products, such an anti-biofilm approach could also be used to control biofilms in environments beyond the human oral cavity. © 2014 The Society for Applied Microbiology.

Just-in-Time og Lean Manufacturing

DEFF Research Database (Denmark)

Michelsen, Aage U.

2004-01-01

Filosofi, principper og teknikker i JIT. Princip i Kanban-styring og dimensionering af et Kanban-system. Lean Thinking og Value Stream Mapping.......Filosofi, principper og teknikker i JIT. Princip i Kanban-styring og dimensionering af et Kanban-system. Lean Thinking og Value Stream Mapping....

Unge og gambling

DEFF Research Database (Denmark)

Nielsen, Jens Christian; Sørensen, Niels Ulrik; Wittendorff, Nina

Rapporten offentliggør resultaterne af den første videnskabelige undersøgelse af pengespil blandt unge danskere mellem 12 og 17 år. Den beskæftiger sig med tre områder 1) Pengespiladfærd blandt unge, 2) Problemspiladfærd blandt unge og 3) Sammenhænge mellem unges risikoadfærd og trivsel samt dere...

Kognition og kultur

DEFF Research Database (Denmark)

Jensen, Hans Jørgen Lundager

2008-01-01

  Igennem det meste af det 20. årh. har akademisk religionsteori været baseret på et kulturparadigme, som ignorerede eller direkte afviste at inddrage biologi og evolution. Med tilkomsten siden 1990'erne af kognitive studier og disses indflydelse på religionsvidenskaben er denne situation ændret ...... ‒ det som er formuleret af bl.a. Emile Durkheim og Roy A. Rappaport....

Oplevelsesanalyse og arkitektur

DEFF Research Database (Denmark)

Nagbøl, Søren Peter

styrer ikke blot de fysiske begrænsninger, den sætter for os, men også de sociale og psykiske processer, der næsten i al forskning har været upåagtet. Samtidig repræsenterer og symboliserer arkitekturen den tid de er opført i. Alt dette analyseres i bogen ved udvikling af metoder forbindelse med konkrete...

Virksomhedens personalearbejde i organisation og samfund

DEFF Research Database (Denmark)

Nielsen, Kjeld

2010-01-01

En model vedr. temaet "Virksomhedens personalearbejde i organisation og samfund" gennemgås ud fra en række funktioner (Grund-, styre- adfærds- og outputfunktioner) og sættes ind i et organisatorisk og samfundsmæssigt perspektiv.......En model vedr. temaet "Virksomhedens personalearbejde i organisation og samfund" gennemgås ud fra en række funktioner (Grund-, styre- adfærds- og outputfunktioner) og sættes ind i et organisatorisk og samfundsmæssigt perspektiv....

Tegn kan også Tale

DEFF Research Database (Denmark)

Fischer, Jutta; Niebe, Susanne; Bisgaard, Hanne

"Tegn kan også Tale" er et begyndermateriale til undervisning af syns- og hørehæmmede døvblindblevne i taktil tegnstøttet kommunikation - en ny taktil kommunikationsform, som bygger på det danske sprog og bruger tegn og andre elementer fra døves tegnsprog. Tegn kan også Tale´ henvender sig primær...

Hjertet og kærligheden

DEFF Research Database (Denmark)

Ehrensvärd, Martin Gustaf

2009-01-01

Sufierne er, på en måde, islams munke og nonner, bortset fra at de ikke er munke og nonner (cølibatet er ikke almindeligt brugt i sufismen). Men de tilhører samme del af deres religion, som buddhistmunke og -nonner, hindu-sannyaser og kristne munke og nonner gør - den del af religionen, der ikke ...... mystica/ illumination/ det uskabte lys/ tawhid/ ain/ rigpa/ moksha) ikke er forskel på dem og gud. Artiklen er en introduktion til sufiernes religiøse praksis....

Lokalisering av arbeidsplasser og boliger

DEFF Research Database (Denmark)

Næss, Petter

2011-01-01

En miljømessig effektiv lokalisering av arbeidsplasser og boliger sikter mot å begrense - og helst redusere - biltrafikk og miljøproblemer knyttet til bytransport, sammenliknet med alternative lokaliseringer. En effektiv transportmessig lokalisering kan også bidra til å redusere tap av verdifulle...... arealer (f eks jordbruksareal eller natur- og friluftsområder) utenfor dagens tettstedsgrense. Tiltaket må samtidig utformes slik at en kan bevare viktige bomiljøkvaliteter og så mye som mulig av de grønne arealene innenfor tettbebyggelsen....

Mass Customization og Postponement - strategier og modeller for integreret produktion og distribution af kundespecifikke produkter

DEFF Research Database (Denmark)

Michelsen, Aage U.; Janus, Pagh

2002-01-01

Mass Customization er et produktionskoncept, der søger at kombinere masseproduktion og enkeltstyksproduktion på en sådan måde, at det er muligt at "masseproducere" kundespecifikke produkter. Postponement er i denne forbindelse et centralt begreb, idet det vedrører placeringen af dekoblingspunktet...... ("customer order decoupling point"), dvs. placeringen af det lager, hvorfra efterfølgende produktion og distribution er styret af kundespecifikke produkter. I artiklen fokuseres på, at hvis produktion og distribution ikke opfattes som to sekventielle systemer, men som ét integreret system, så opstår der en...

A Model of Rapid Radicalization Behavior Using Agent-Based Modeling and Quorum Sensing

Science.gov (United States)

Schwartz, Noah; Drucker, Nick; Campbell, Kenyth

2012-01-01

Understanding the dynamics of radicalization, especially rapid radicalization, has become increasingly important to US policy in the past several years. Traditionally, radicalization is considered a slow process, but recent social and political events demonstrate that the process can occur quickly. Examining this rapid process, in real time, is impossible. However, recreating an event using modeling and simulation (M&S) allows researchers to study some of the complex dynamics associated with rapid radicalization. We propose to adapt the biological mechanism of quorum sensing as a tool to explore, or possibly explain, rapid radicalization. Due to the complex nature of quorum sensing, M&S allows us to examine events that we could not otherwise examine in real time. For this study, we employ Agent Based Modeling (ABM), an M&S paradigm suited to modeling group behavior. The result of this study was the successful creation of rapid radicalization using quorum sensing. The Battle of Mogadishu was the inspiration for this model and provided the testing conditions used to explore quorum sensing and the ideas behind rapid radicalization. The final product has wider applicability however, using quorum sensing as a possible tool for examining other catalytic rapid radicalization events.

Ældres hverdagspraksisser og aldringspolitik. Om synkroniseringsarbejdet imellem hverdag og politik

Directory of Open Access Journals (Sweden)

Aske Juul Lassen

2015-07-01

Full Text Available Ældres hverdagspraksisser fremtræder ofte som problemer, som aldringspolitik- ken søger at løse. Forfatterne diskuterer forskellige etnologiske tilgange til hver- dagen, og præsenterer forholdet imellem hverdagspraksisser og politiske praksis- ser som et kontinuerligt synkroniseringsarbejde. Dette bruges til at vise, hvordan problemer som afhængighed, forfald, ensomhed og passivitet bliver problemati- seret på bestemte måder i diskursen om aktiv aldring, og hvordan problemerne tager sig ud for de ældre, set fra et hverdagslivsperspektiv. Artiklen er baseret på et etnografisk feltarbejde på to aktivitetscentre.

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

Directory of Open Access Journals (Sweden)

Angelika eHolm

2014-06-01

Full Text Available Both direct and long-range interactions between pathogenic Pseudomonas aeruginosa bacteria and their eukaryotic hosts are important in the outcome of infections. For cell-to-cell communication, these bacteria employ the quorum sensing (QS system to pass on information of the density of the bacterial population and collectively switch on virulence factor production, biofilm formation and resistance development. Thus, QS allows bacteria to behave as a community to perform tasks which would be impossible for individual cells, e.g. to overcome defense and immune systems and establish infections in higher organisms. This review highlights these aspects of QS and our own recent research on how P.aeruginosa communicates with human cells using the small QS signal molecules N-acyl homoserine lactones (AHL. We focus on how this conversation changes the behavior and function of neutrophils, macrophages and epithelial cells and on how the signaling machinery in human cells responsible for the recognition of AHL. Understanding the bacteria-host relationships at both cellular and molecular levels is essential for the identification of new targets and for the development of novel strategies to fight bacterial infections in the future.

Mental sundhed, klasse og livshistorie

DEFF Research Database (Denmark)

Dybbroe, Betina

2016-01-01

Kapitlet stiller spørgsmål til, hvordan klasserelationer påvirker identitet og handlerummet for børn og deres familier, og skaber betydninger for ulige sundhed. De empiriske eksempler som bidrager til analysen er hentet fra psykiatrisk praksis, hvori børn og familier indgår i relationer til behan...... behandlere og sundhedssystem, og hvori sygdomskategoriseringer skabes. Her får vi et indblik i, hvordan ulige mental sundhed indgår i komplekse sociale livsmønstre af social ulighed, reproduceret over flere generationer....

Umberto Eco og fortolkningens semiotik

DEFF Research Database (Denmark)

Frandsen, Finn

1997-01-01

En analyse af spørgsmålet om fortolkningens muligheder og grænser, sådan som det bliver formuleret og besvaret i den italienske semiotiker Umberto Ecos teoretiske forfatterskab. Problemstillingen - og dens transformationer hvad angår såvel metasprog, omfang, niveau og fokus - følges fra begyndelsen...... af 60'erne, hvor Eco er inspireret af fænomenologi og hermeneutik (f.eks. i Opera aperta), til begyndelsen af 90'erne, hvor han arbejder med tekstpragmatik og receptionssemiotik. (f.eks. i I limiti dell'interpretazione)...

Vision og virkelighed

DEFF Research Database (Denmark)

Carlsen, Benny Bang

Bogen behandler andetsprogsdidaktiske problemstillinger og emner som fx sproglig opmærksomhed, kontrastiv lingvistik, kommunikativ kompetence, andetsprogstilegnelsesteorier, intersprogsanalyse og kulturmødet....

Professor og DMI

DEFF Research Database (Denmark)

Kaas, Eigil

2010-01-01

Det er koldt, og det har det været længe. Sammen med sneen har det en selvforstærkende effekt på vintervejret, forklarer professor og meteorolog. Kulde: - Det er koldt, fordi vinden kommer fra et sted, hvor det er koldt. Det er den enkle forklaring på, at Danmark og store dele af Europa lige nu...... oplever meget lave temperaturer - og for Danmarks vedkommende en usædvanlig lang periode med vintervejr. Forklaringen kommer fra professor Eigil Kaas fra Niels Bohr Instituttet ved Københavns Universitet. Han forklarer til jp.dk, at vintervejret dog er betinget af den mere eller mindre tilfældige måde...

Danmarks rolle i de globale værdikæder for konventionel og certificeret soja og palmeolie

DEFF Research Database (Denmark)

Bosselmann, Aske Skovmand; Gylling, Morten

2012-01-01

Dette notat kortlægger Danmarks rolle i de globale handelsveje for soja og palmeolie ved brug af import- og eksportstatistikker, fremlægger de økonomiske aspekter ved import og brug af certificeret soja og palmeolie, og diskuterer, hvorvidt certificeringsordningerne kan beskrives som legitime og ...

Rapport: Coding Class - Dokumentation og evaluering

DEFF Research Database (Denmark)

Hansbøl, Mikala; Ejsing-Duun, Stine

2017-01-01

Denne rapport rummer evaluering og dokumentation af Coding Class projektet . Coding Class projektet blev igangsat i skoleåret 2016/2017 af IT-Branchen i samarbejde med en række medlemsvirksomheder, Københavns kommune, Vejle Kommune, Styrelsen for IT- og Læring (STIL) og den frivillige forening...... Coding Pirates . Rapporten er forfattet af Docent i digitale læringsressourcer og faglig leder af forsknings- og udviklingsmiljøet Digitalisering i Skolen (DiS), Mikala Hansbøl, fra Institut for Skole og Læring ved professionshøjskolen Metropol; og Lektor i læringsteknologi, interaktionsdesign, design...... tænkning og design-pædagogik, Stine Ejsing-Duun fra Forskningslab: It og Læringsdesign (ILD-LAB) ved Institut for Kommunikation ved Aalborg Universitet i København. Vi har fulgt og gennemført evaluering og dokumentation af Coding Class projektet i perioden november 2016 til maj 2017...

Materialers og komponenters bestandighed

DEFF Research Database (Denmark)

Publikationen omfatter 41 indlæg på et nordisk symposium arrangeret af SBI i samarbejde med NORDTEST-BYGG og NBS-MK. Indlæggene giver information om prøvningsmetoder og vurderingskriterier for byggematerialers og -komponenters bestandighed....

IT og Innovation

DEFF Research Database (Denmark)

Nordbjerg, Finn Ebertsen; Andersen, Poul

IT og innovation behandles ud fra tre perspektiver: IT-udviklingsprocesser, IT og lærende organisation og IT-understøttelse af en innovativ didaktik. Vi beskriver nogle ideer til, hvordan arbejdsformer anvendt i forbindelse med ITudviklingsprocesser kan inspirere en innovativ didaktik. IT...... beskrives nogle idéer til, hvordan IT-værktøjer kan understøtte innovative læreprocesser....

Immaterialret og IT

DEFF Research Database (Denmark)

Riis, Thomas

Indhold: Beskyttelse af edb-programmer ; Patentbeskyttelse af softwarerelaterede opfindelser ; Beskyttelse af databaser ; Ophavsret og internettet ; Beskyttelse af halvlederkredsløb ; Informationsteknologi og konkurrence...

Webdesign, benspænd og ikoner

DEFF Research Database (Denmark)

Engholm, Ida

2014-01-01

Web (www) i 1993 blev nettet også forsynet med billeder, lyd, grafik og animationer, og det blev nemmere for ikke-teknisk kyndige brugere at benytte det. Dermed blev det for alvor også relevant at interessere sig for, hvordan man gav grafisk og interaktiv form til websites, søgemaskiner og andre...

Børns leg og eksperimenterende virksomhed

DEFF Research Database (Denmark)

Damgaard Warrer, Sarah; Broström, Stig

Børns leg og eksperimenterende virksomhed er et rigt felt med mange perspektiver, indgangsvinkler og nuancer. I denne bog kædes leg og det eksperimenterende og skabende sammen som to gensidigt forbundne fænomener og belyses i pædagogisk og didaktisk perspektiv. Desuden beskrives potentialet i båd...

Adelskultur og herregårdsjagt i tiden mellem Junigrundloven og Lensafløsningen

Directory of Open Access Journals (Sweden)

Jesper Laursen

2011-06-01

Full Text Available Indledningsvis præsenteres baggrunden for landadelens storhedstid i sidste halvdel af 1800-tallet i Danmark. Det var denne del af adelen, der for alvor havde mulighed for at manifestere noget, der lignede adelig suverænitet, hvilket i særdeleshed gjaldt majoratsbesidderne, som foruden herregårde med alt, hvad dertil hørte, havde økonomiske midler til deres rådighed, som ingen andre kunne præstere på den tid. Og det havde den et grænseløst behov for at stille til skue, såvel i sin livsførelse på herregårdene som i enhver anden sammenhæng. Jagterne kom til at spille en fremtrædende rolle i disse statusmarkeringer, og en lensgreve gav direkte udtryk for, at han anså dem for at være en del af den luksus, som var nødvendig for at give standen éclat. Dette udsagn synes at rumme nøglen til en nærmere forståelse af den højere landadels ekstravagante livsførelse, og det leder tanken hen på teorier udviklet af socialøkonomen Thorstein Veblen i bogen The Theory of the Leisure Class og af socialantropologen og sociologen Roland Girtler i bogen Die feinen Leute. I artiklen diskuteres det, i hvilket omfang Veblens teorier om iøjnefaldende fritid og forbrug og Girtlers teorier om menneskets iboende stræben efter fornemhed og de dynamiske aspekter forbundet hermed kan bidrage til en forståelse af den betydning, som jagten fik for landadelen i den pågældende periode. Emnet har tidligere været behandlet i forbindelse med en bredt anlagt afhandling om herregårdsjagtens historie i Danmark. Her bliver det gjort til genstand for en sammenfattende diskussion ud fra den opfattelse, at landadelen ganske vist anvendte jagterne og andre statusmarkeringer som led i en generel manifestation af adelig suverænitet og eksklusivitet, men at bestræbelserne nok især var drevet af indbyrdes kappestrid og konkurrence om at opnå en højere grad af fornemhed, snarere end at det handlede om at distingvere sig i forhold til det fremvoksende

EPR, kvantemekanik og Bohr

OpenAIRE

Nielsen, Morten Klockmann

2007-01-01

Dette projekt omhandler området hvor filosofi og fysik smelter sammen. Kvantemekanikkens tilblivelse fik en hård medfart hvilket diskussionerne mellem især Albert Einstein og Niels Bohr vidner om. De var hovedpersoner i striden om hvordan kvantemekanikken skulle fortolkes, og diskussionen kulminerede i 1935 hvor Einstein sammen med kollegerne Podolsky og Rosen offentliggjorde en artikel med titlen “Can Quantum-Mechanical Description of Physical Reality Be Considered Complete?” (EPR-artiklen)....

Brugerdeltagelse og motivation i rehabilitering

DEFF Research Database (Denmark)

Christensen, Elsebeth Hovmøller

2005-01-01

vil herunder nærmere undersøge, om inddragelse af brugerdeltagelse i en rehabiliteringsproces påvirker borgerens motivation. Vores hypotese er, at brugerdeltagelse øger motivationen hos borgeren, således at borgeren er mere klar til at tage ansvar for egen rehabiliteringsproces og den derved bliver...... brugerdeltagelse og empowerment og om motivation - herunder selvbestemmelse, autonomi, self-efficacy og forholdet mellem læring og motivation. Datamateriale Datamaterialet består seks interview med seks forskellige respondenter, som er strategisk udvalgte. Der er tale om tre kvinder og tre mænd i alderen 26 – 50...... år, der alle er fysisk funktionshæmmede, i arbejde og bosat i Jylland. Interviewene er optaget på bånd og herefter transskriberede Konklusion Konklusionen er, at brugerdeltagelse påvirker borgerens motivation i et rehabiliteringsforløb. Den ønskede grad af brugerdeltagelse er et individuelt...

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

Directory of Open Access Journals (Sweden)

Tom Defoirdt

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

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

Science.gov (United States)

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

2012-01-01

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

8 videoer om nyrer og urinvejes anatomi og fysiologi

DEFF Research Database (Denmark)

2014-01-01

Screencastvideoer - optagelser af Powerpoint-diasshow med indtaling. Videoerne indgår i et udviklingsprojekt hvor flipped classroom-metoden afprøves og de studerendes handlinger, opfattelser og præferencer undersøges. Videoer er typisk en central del af flipped classroom-undervisning....

Feedback - evalueringskultur og motivation

DEFF Research Database (Denmark)

Dolmer, Grete

2015-01-01

I bogen formidles erfaringer og refleksioner med anvendelse af studieaktivitetsmodellen i praksis. Forskellige udfordringer og muligheder belyses, og der identificeres opmærksomhedspunkter til arbejdet med studieaktiviteter i studieaktivitetsmodellens fire kvadranter. Bogen baserer sig på et følg...

Rekruttering og fastholdelse af seniorer

DEFF Research Database (Denmark)

Luccat, Dorte

Denne undersøgelse har til formål at afdække holdninger, praksis, barrierer og muligheder i forhold til rekruttering og fastholdelse af seniorer. Undersøgelsen er baseret på 19 kvalitative interviews med henholdsvis tillidsrepræsentanter og personaleledere på 13 forskellige arbejdspladser. De...... udvalgte arbejdspladser repræsenterer såvel den offentlige som den private sektor samt større (mindst 50 ansatte) og mindre (under 50 ansatte) arbejdspladser. Vi har endvidere besøgt virksomheder, der henholdsvis har og ikke har seniorer ansat, for at indsamle information om holdninger og praksis fra flere...

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

DEFF Research Database (Denmark)

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

2009-01-01

the quorum regulatory RNAs 1-4 (Qrr1-4). The four Qrr sRNAs are functionally redundant. That is, expression of any one of them is sufficient for wild-type quorum-sensing behaviour. Here, we show that the combined action of two feedback loops, one involving the sRNA-activator LuxO and one involving the sRNA......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......-target HapR, promotes gene dosage compensation between the four qrr genes. Gene dosage compensation adjusts the total Qrr1-4 sRNA pool and provides the molecular mechanism underlying sRNA redundancy. The dosage compensation mechanism is exquisitely sensitive to small perturbations in Qrr levels. Precisely...

Modstandssvejsning, Forskning og udvikling på Institut for Produktion og Ledelse, DTU

DEFF Research Database (Denmark)

Bay, Niels

2002-01-01

Modstandssvejsning finder udbredt anvendelse i industriel produktion af automobiler, fly, elektronik, radiatorer, containere, pumper m.m. til sammenføjning af ens og forskellige metaller (f.eks. C-stål, højstyrkestål, kobber, sølv, nikkel, aluminium og titan legeringer).......Modstandssvejsning finder udbredt anvendelse i industriel produktion af automobiler, fly, elektronik, radiatorer, containere, pumper m.m. til sammenføjning af ens og forskellige metaller (f.eks. C-stål, højstyrkestål, kobber, sølv, nikkel, aluminium og titan legeringer)....

Metodenotat om anvendelse af fremsyn i kommunale og regionale udviklings- og planstrategiprocesser

DEFF Research Database (Denmark)

Rasmussen, B.; Madsen, F.

2006-01-01

Notatet indeholder forslag til tilrettelæggelse af et regionalt fremsyn med tilhørende beskrivelse af processens enkelte elementer delt i følgende faser: Definition og afgrænsning. Forberedende fase. SWOT analyse. Eksplorativ fase. Bearbejdning.Implementering. Formidling og præsentation. Identite......Notatet indeholder forslag til tilrettelæggelse af et regionalt fremsyn med tilhørende beskrivelse af processens enkelte elementer delt i følgende faser: Definition og afgrænsning. Forberedende fase. SWOT analyse. Eksplorativ fase. Bearbejdning.Implementering. Formidling og præsentation...

Mellem kommunikation og kreativitet

DEFF Research Database (Denmark)

Eriksson, Birgit

2014-01-01

Den franske filosof og kunstteoretiker Yves Michaud har argumenteret for, at moderniteten er karakteriseret ved tre utopier: Utopien om demokratisk medborgerskab, arbejdets utopi og kunstens utopi. Kunstens utopi sporer han tilbage til Immanuel Kants æstetik og hans forestilling om, at vi i...

Facebook samtaler og visionsformuleringer

DEFF Research Database (Denmark)

Madsen, Anders Koed; Munk, Anders Kristian

I forbindelse med Aalborg Kommunes visionsproces for fremtidens folkeskole har forfatterne mellem september 2014 og januar 2015 indsamlet og analyseret visionsrelevante indlæg på skoleforvaltningens facebookside. Analysen falder i to dele: 1. En struktureret analyse og indeksering af de visioner,...

Voksenuddannelse og regional udvikling

DEFF Research Database (Denmark)

Rasmussen, Palle

2008-01-01

Med udgangspunkt i regionale og lokale forskelle uddannelsesforskelle behandler artiklen uddannelsers rolle i regional udvikling. Der lægges særlig vægt på forskellige former for voksenuddannelse. Hvad betyder udviklingen mod vidensamfundet for udviklingen i erhverv, beskæftigelse og sociale...... forhold? Hvilken rolle spiller uddannelse i centerområder og udkantsområder? Hvordan kan uddannelse og læring bidrage til regional udvikling? Hvilke roller kan voksenuddannelse have i denne sammenhæng?...

Strategisk compliance og regulering

DEFF Research Database (Denmark)

Kühn Pedersen, Mogens

2016-01-01

Denne artikel introducerer strategisk compliance og påpeger dens samspil med klassiske og nyere former for reguleringer i digital værdiskabelse. Konteksten er den digitale økonomi, som vokser frem imellem den materielle økonomis bærepiller: Virksomheder og markeder, men består af en helt ny...... materialitet, som er det digitale univers og dets modsvarighed i nye krav til compliance. Den nye materialitet stiller nye krav, hvad angår digitale processer og transaktioner. Klassisk regulering, som aktører ikke selv kan ændre, støder på egenregulering, hvor aktørerne selv opsætter regler for at skabe...... digital værdi. Dette kalder på strategisk compliance. Med digitalisering er strategisk compliance sat på dagsordnen i reguleringsdebatten. Vi hævder, at regulering og egenregulering kan komme til at virke komplementært i det post-industrielle, digitaliserede samfund....

Mentaliseringsbaseret behandling og musikterapi

Directory of Open Access Journals (Sweden)

Niels Hannibal

2013-06-01

Full Text Available Denne artikel behandler spørgsmålet, om mentaliseringsbaseret terapi er en metode der medfører et skift i terapeutisk forholdemåde for analytisk orienterede musikterapeuter i arbejde med patienter med personlighedsforstyrrelse. Artiklen skal ses om en del af den teoretiske integrationer af MBT i musikterapi med denne målgruppe. Artiklen ser på de forskrifter til mentaliseringsfremmende tiltag som Allan, Fonagy og Bateman (2010 beskriver. Artiklens konklusion er dels af MBT’s krav til forholdemåde og interventionsfokus er et skift i forhold til traditionel analytisk orienteret terapi, bl.a. i forhold til fokus på her og nu, og øget fokus på implicit relationel læring, men siger samtidig at musikterapi allerede lever op til og i forvejen anvender disse elementer i musikterapi qua ligheden mellem klinisk improvisation (Wigram 2004 og implicit relationel viden (Stern 2010.

Klassisk og moderne pædagogisk teori

DEFF Research Database (Denmark)

Klassisk og moderne pædagogisk teori giver en indføring i pædagogikkens centrale problemstillinger, teorier, personer og begreber. Bogen indeholder 31 kapitler samt en leksikal del, skrevet af førende danske forskere og ordnet tematisk under følgende overskrifter: Del 1: Pædagogik og teorier om...... opdragelse, undervisning og uddannelse Del 2: Nationalstat og globalisering Del 3: Fag, viden og undervisning Del 4: Kulturelle og sociale forskelle Del 5: Perspektiver og deres betydning Del 6: Pædagogikkens institutioner Del 7: Socialt og pædagogisk samspil Del 8: Person- og teoriintroduktioner Der er...

Bogen og folket