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Homoserine Lactone (homoserine + lactone)

Distribution by Scientific Domains

Life Sciences	55%
Chemistry	22%

Kinds of Homoserine Lactone

acyl homoserine lactone

Selected Abstracts

Quorum sensing: the power of cooperation in the world of Pseudomonas

ENVIRONMENTAL MICROBIOLOGY, Issue 4 2005
Mario Juhas
Summary Work over the past few years has provided evidence that quorum sensing is a generic regulatory mechanism that allows bacteria to launch a unified, coordinated response in a population density-dependent manner to accomplish tasks which would be difficult, if not impossible, to achieve for a single bacterial cell. Quorum sensing systems are widespread among pseudomonads and the one of the human opportunistic pathogen Pseudomonas aeruginosa belongs to the most extensively studied cell-to-cell communication systems. In this organism, quorum sensing is highly complex and is made up of two interlinked N- acyl homoserine lactone (AHL)-dependent regulatory circuits, which are further modulated by a non-AHL-related signal molecule and numerous regulators acting both at the transcriptional and post-transcriptional level. This genetic complexity may be one of the key elements responsible for the tremendous environmental versatility of P. aeruginosa. Work of the past few years showed that quorum sensing is essential for the expression of a battery of virulence factors as well as for biofilm formation in P. aeruginosa and thus represents an attractive target for the design of novel drugs for the treatment of P. aeruginosa infections. Furthermore, the cell-to-cell communication ability was also demonstrated in a number of additional pseudomonads. [source]

Quorum-sensing in Gram-negative bacteria

FEMS MICROBIOLOGY REVIEWS, Issue 4 2001
Neil A Whitehead
Abstract It has become increasingly and widely recognised that bacteria do not exist as solitary cells, but are colonial organisms that exploit elaborate systems of intercellular communication to facilitate their adaptation to changing environmental conditions. The languages by which bacteria communicate take the form of chemical signals, excreted from the cells, which can elicit profound physiological changes. Many types of signalling molecules, which regulate diverse phenotypes across distant genera, have been described. The most common signalling molecules found in Gram-negative bacteria are N -acyl derivatives of homoserine lactone (acyl HSLs). Modulation of the physiological processes controlled by acyl HSLs (and, indeed, many of the non-acyl HSL-mediated systems) occurs in a cell density- and growth phase-dependent manner. Therefore, the term ,quorum-sensing' has been coined to describe this ability of bacteria to monitor cell density before expressing a phenotype. In this paper, we review the current state of research concerning acyl HSL-mediated quorum-sensing. We also describe two non-acyl HSL-based systems utilised by the phytopathogens Ralstonia solanacearum and Xanthomonas campestris. [source]

Novel synthesis of [1- 11C], -vinyl- , -aminobutyric acid ([1,11C]GVG) for pharmacokinetic studies of addiction treatment

JOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 3 2002
Zongren Zhang
Abstract , -Vinyl- , -aminobutyric acid (GVG, Vigabatrin®), a suicide inhibitor of GABA-transaminase (GABA-T), has been suggested as a new drug for the treatment of substance abuse. In order to better understand its pharmacokinetics and potential side effects, we have developed a radiosynthesis of carbon-11 (t1/2=20 min) labeled GVG for positron emission tomographic (PET) studies. We report here a novel synthetic strategy to prepare the precursor and to efficiently label GVG with C-11. 5-Bromo-3-(carbobenzyloxy)amino-1-pentene was synthesized in five steps from homoserine lactone, including reduction and methylenation. This was used in a one-pot, two-step radiosynthesis. Displacement of bromide with no-carrier-added [11C]cyanide followed by acid hydrolysis afforded [1- 11C]GVG with decay corrected radiochemical yields of 27±9% (n=6, not optimized) with respect to [11C]cyanide in a synthesis time of 45 min. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Identification of the central quorum sensing regulator of virulence in the enteric phytopathogen, Erwinia carotovora: the VirR repressor

MOLECULAR MICROBIOLOGY, Issue 1 2006
Tom Burr
Summary In the Gram-negative phytopathogen, Erwinia carotovora ssp. atroseptica (Eca) virulence depends on the production of a N- (3-oxohexanoyl)- l -homoserine lactone (OHHL) quorum sensing (QS) signal. This work identifies the elusive ,missing link' between QS and virulence in Erwinia. We have identified and characterized a novel regulator of virulence, VirR, in Eca and show that a virR mutation completely restores virulence factor production to an Eca mutant unable to synthesize OHHL. This effect of the virR mutation translates to a restoration of virulence to wild-type levels and thus provides evidence that VirR acts to prevent the production of virulence factors at low cell density. We also show that, in Eca, transcription of virulence genes is controlled by OHHL and that this control is effected through the action of VirR. We also demonstrate that the VirR regulatory pathway is present and functional in both blackleg and soft rotting species of Erwinia. [source]

Phosphate availability regulates biosynthesis of two antibiotics, prodigiosin and carbapenem, in Serratia via both quorum-sensing-dependent and -independent pathways

MOLECULAR MICROBIOLOGY, Issue 2 2003
Holly Slater
Summary Serratia sp. ATCC 39006 produces two secondary metabolite antibiotics, 1-carbapen-2-em-3-carboxylic acid (Car) and the red pigment, prodigiosin (Pig). We have previously reported that production of Pig and Car is controlled by N -acyl homoserine lactone (N -AHL) quorum sensing, with synthesis of N -AHLs directed by the LuxI homologue SmaI, and is also regulated by Rap, a member of the SlyA family. We now describe further characterization of the SmaI quorum-sensing system and its connection with other regulatory mechanisms. We show that the genes responsible for biosynthesis of Pig, pigA,O, are transcribed as a single polycistronic message in an N -AHL-dependent manner. The smaR gene, transcribed convergently with smaI and predicted to encode the LuxR homologue partner of SmaI, was shown to possess a negative regulatory function, which is uncommon among the LuxR-type transcriptional regulators. SmaR represses transcription of both the pig and car gene clusters in the absence of N -AHLs. Specifically, we show that SmaIR exerts its effect on car gene expression via transcriptional control of carR, encoding a pheromone-independent LuxR homologue. Transcriptional activation of the pig and car gene clusters also requires a functional Rap protein, but Rap dependency can be bypassed by secondary mutations. Transduction of these suppressor mutations into wild-type backgrounds confers a hyper-Pig phenotype. Multiple mutations cluster in a region upstream of the pigA gene, suggesting this region may represent a repressor target site. Two mutations mapped to genes encoding pstS and pstA homologues, which are parts of a high-affinity phosphate transport system (Pst) in Escherichia coli. Disruption of pstS mimicked phosphate limitation and caused concomitant hyper-production of Pig and Car, which was mediated, in part, through increased transcription of the smaI gene. The Pst and SmaIR systems define distinct, yet overlapping, regulatory circuits which form part of a complex regulatory network controlling the production of secondary metabolites in Serratia ATCC 39006. [source]

Inhibition of quorum-sensing signals by essential oils

PHYTOTHERAPY RESEARCH, Issue 5 2010
Mira Ágnes Szabó
Abstract The role of quorum sensing (QS) is well known in microbial pathogenicity and antibiotic resistance. QS is responsible for motility, swarming, and biofilm production based on the signal molecules, e.g., acylated homoserine lactones (AHLs) produced by micro-organisms above certain population density. The inhibition of QS may reduce pathogenicity, antibiotic resistance and biofilm formation in systemic and local infections. The homoserine lactones and other transmitters contribute to antibiotic resistance and pathogenicity of several bacteria; consequently the inhibition of QS signals reduces the problem of resistance and virulence. Due to the increasing number of persistent non-treatable infections, there is an urgent need to develop new strategies to combat infections that destabilize bacterial communities in the host. The effect of essential oils on bacterial growth and QS were evaluated using the sensor strain Chromobacterium violaceum CV026 and N -acyl homoserine lactone (AHL) producing Escherichia coli ATTC 31298 and the grapevine colonizing Ezf 10-17 strains. Of the tested oils, rose, geranium, lavender and rosemary oils were the most potent QS inhibitors. Eucalyptus and citrus oils moderately reduced pigment production by CV026, whereas the chamomile, orange and juniper oils were ineffective. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Altering the Substrate Specificity of RhlI by Directed Evolution

CHEMBIOCHEM, Issue 3 2009
Pavan Kumar Reddy Kambam
Abstract Reducing virulence: RhlI catalyzes the synthesis of N -butanoyl homoserine lactone (BHL), with a minor product N -hexanoyl homoserine lactone (HHL). By using directed evolution and a genetic screen, RhlI has been engineered for enhanced production of both BHL and HHL at a similar level. Quorum sensing regulates biofilm formation and virulence factor production in the human opportunistic pathogen Pseudomonas aeruginosa. We used directed evolution to engineer RhlI, an enzyme in the RhlI,RhlR quorum-sensing system of P. aeruginosa, to alter its substrate specificity and gain insight into the molecular mechanisms of quorum sensing. By using a genetic screen, we identified a mutant with improved production of RhlI's two signaling molecules, N -butanoyl- and N -hexanoyl-homoserine lactone (BHL and HHL). In particular, production of BHL has been enhanced by more than two-fold, and the synthesis of HHL has been improved from an undetectable level to a level similar to BHL; this change indicates a significant change in substrate specificity. No significant change in the gene expression level was observed. Sequence alignments suggest that the mutations are most likely to facilitate interactions between the enzyme and the two acylated ACP substrates. This work also demonstrates that the genetic screen/selection should be useful in engineering additional quorum-sensing components. [source]

Degradation of N -acyl homoserine lactone quorum sensing signal molecules by forest root-associated fungi

FEMS MICROBIOLOGY ECOLOGY, Issue 2 2008
Stephane Uroz
Abstract A collection of mycorrhizal and nonmycorrhizal root-associated fungi coming from forest environments was screened for their ability to degrade N -acyl homoserine lactones (AHL) or to prevent AHL recognition by producing quorum sensing inhibitors (QSI). No production of QS-inhibitors or -activators was detected using the two biosensors Chromobacterium violaceum CV026 and Agrobacterium tumefaciens in the culture supernatant of these fungi. However, the ability to degrade C6- and 3O,C6-HSL was detected for three fungal isolates. Acidification assay revealed that the AHL were degraded by a lactonase activity for two of these isolates. These results demonstrated for the first time that the forest root-associated fungi are capable of degrading the AHL signal molecules. [source]