Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 15 de 15
Filter
Add more filters










Publication year range
1.
Environ Microbiol ; 16(8): 2623-2634, 2014 Aug.
Article in English | MEDLINE | ID: mdl-24191970

ABSTRACT

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


Subject(s)
4-Butyrolactone/analogs & derivatives , Aliivibrio fischeri/genetics , Bacterial Proteins/genetics , Gene Expression Regulation, Bacterial , Quorum Sensing/genetics , Repressor Proteins/genetics , Symbiosis/genetics , Trans-Activators/genetics , Transcription Factors/genetics , 4-Butyrolactone/metabolism , Aliivibrio fischeri/metabolism , Animals , Bacterial Proteins/metabolism , Decapodiformes/microbiology , Luminescence , Repressor Proteins/metabolism , Time Factors , Trans-Activators/metabolism , Transcription Factors/metabolism
2.
Appl Environ Microbiol ; 76(24): 8255-8, 2010 Dec.
Article in English | MEDLINE | ID: mdl-20935125

ABSTRACT

We report the screening of 16,000 synthetic compounds for induction and inhibition of quorum sensing in a Pseudomonas putida N-acylated l-homoserine lactone (AHL) sensor strain engineered with the LasR transcriptional activator. LasR controls virulence gene expression in the opportunistic pathogen Pseudomonas aeruginosa and is of significant interest as a therapeutic target. Nine compounds that inhibit and 14 compounds that induce LasR activity were identified in our high-throughput screen.


Subject(s)
Anti-Bacterial Agents/isolation & purification , Bacterial Proteins/antagonists & inhibitors , Bacterial Proteins/biosynthesis , Pseudomonas putida/drug effects , Quorum Sensing/drug effects , Trans-Activators/antagonists & inhibitors , Trans-Activators/biosynthesis , Enzyme Inhibitors/isolation & purification , High-Throughput Screening Assays , Pseudomonas aeruginosa/drug effects , Pseudomonas aeruginosa/physiology , Pseudomonas putida/physiology , Transcriptional Activation/drug effects
3.
ACS Chem Biol ; 4(12): 1051-9, 2009 Dec 18.
Article in English | MEDLINE | ID: mdl-19928886

ABSTRACT

Quorum sensing (QS) is under the control of N-acylated l-homoserine lactones (AHLs) and their cognate receptors (LuxR-type proteins) in Gram-negative bacteria and plays a major role in mediating host-bacteria interactions by these species. Certain cyclic dipeptides (2,5-diketopiperazines, DKPs) have been isolated from bacteria and reported to activate or inhibit LuxR-type proteins in AHL biosensor strains, albeit at significantly higher concentrations than native lactones. These reports have prompted the proposal that DKPs represent a new class of QS signals and potentially even interspecies or interkingdom signals; their mechanisms of action and physiological relevance, however, remain unknown. Here, we describe a library of synthetic DKPs that was designed to (1) determine the structural features necessary for LuxR-type protein activation and inhibition and (2) probe their mechanisms of action. These DKPs, along with several previously reported natural DKPs, were screened in bacterial reporter gene assays. In contrast to previous reports, the native DKPs failed to exhibit either antagonistic or agonistic activities in these assays. However, non-natural halogenated cyclo(l-Pro-l-Phe) derivatives were capable of inhibiting luminescence in Vibrio fischeri. Interestingly, additional experiments revealed that these DKPs do not compete with the natural lactone signal, OHHL, to inhibit luminescence. Together, these data suggest that DKPs are not QS signals in the bacteria examined in this study. Although these compounds can influence QS-regulated outcomes, we contend that they do not do so through direct interaction with LuxR-type proteins. This work serves to refine the lexicon of naturally occurring QS signals used by Gram-negative bacteria.


Subject(s)
Diketopiperazines/metabolism , Dipeptides/metabolism , Gram-Negative Bacteria/metabolism , Peptides, Cyclic/metabolism , Quorum Sensing , Repressor Proteins/metabolism , Trans-Activators/metabolism , Aliivibrio fischeri/metabolism , Diketopiperazines/chemical synthesis , Diketopiperazines/chemistry , Dipeptides/chemical synthesis , Dipeptides/chemistry , Molecular Structure , Peptides, Cyclic/chemical synthesis , Peptides, Cyclic/chemistry , Repressor Proteins/agonists , Repressor Proteins/antagonists & inhibitors , Small Molecule Libraries/chemical synthesis , Small Molecule Libraries/chemistry , Small Molecule Libraries/metabolism , Trans-Activators/agonists , Trans-Activators/antagonists & inhibitors
4.
Org Lett ; 11(20): 4600-3, 2009 Oct 15.
Article in English | MEDLINE | ID: mdl-19743816

ABSTRACT

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


Subject(s)
4-Butyrolactone/analogs & derivatives , Quorum Sensing/drug effects , 4-Butyrolactone/chemical synthesis , 4-Butyrolactone/chemistry , 4-Butyrolactone/pharmacology , Acylation , Aliivibrio fischeri/cytology , Aliivibrio fischeri/drug effects , Chromobacterium/cytology , Chromobacterium/drug effects , Cyclization , Nitrogen/chemistry
5.
Bioorg Med Chem Lett ; 18(22): 5978-81, 2008 Nov 15.
Article in English | MEDLINE | ID: mdl-18760602

ABSTRACT

A focused library of N-aryl l-homoserine lactones was designed around known lactone leads and evaluated for antagonistic and agonistic activity against quorum-sensing receptors in Agrobacterium tumefaciens, Pseudomonas aeruginosa, and Vibrio fischeri. Several compounds were identified with significantly heightened activities relative to the lead compounds, and new structure-activity relationships (SARs) were delineated. Notably, 4-substituted N-phenoxyacetyl and 3-substituted N-phenylpropionyl l-homoserine lactones were identified as potent antagonists of TraR and LuxR, respectively.


Subject(s)
4-Butyrolactone/analogs & derivatives , Quorum Sensing/drug effects , 4-Butyrolactone/chemical synthesis , 4-Butyrolactone/chemistry , 4-Butyrolactone/pharmacology , Agrobacterium tumefaciens/metabolism , Aliivibrio fischeri/metabolism , Bacterial Proteins/antagonists & inhibitors , Combinatorial Chemistry Techniques , Dose-Response Relationship, Drug , Molecular Structure , Pseudomonas aeruginosa/metabolism , Repressor Proteins/antagonists & inhibitors , Structure-Activity Relationship , Trans-Activators/antagonists & inhibitors
6.
ISME J ; 2(11): 1101-11, 2008 Nov.
Article in English | MEDLINE | ID: mdl-18650927

ABSTRACT

The overall goal of this study was to examine the role of quorum-sensing (QS) signals in a multispecies microbial community. Toward this aim, we studied QS signals produced by an indigenous member and an invading pathogen of the microbial community of the cabbage white butterfly (CWB) larval midgut (Pieris rapae). As an initial step, we characterized the QS system in Pantoea CWB304, which was isolated from the larval midgut. A luxI homolog, designated panI, is necessary for the production of N-acyl-L-homoserine lactones (AHLs) by Pantoea CWB304. To determine whether AHL signals are exchanged in the alkaline environment of the midgut, we constructed AHL-sensing bioluminescent reporter strains in Pantoea CWB304 and a panI mutant of this strain. In the gut of the CWB larvae, the reporter in an AHL-deficient Pantoea CWB304 detected AHLs when coinoculated with the wild type. To study the role of AHL signals produced by a community invader, we examined pathogenesis of Pseudomonas aeruginosa PAO1 in CWB larvae. Mortality induced by P. aeruginosa PAO1 was significantly reduced when signaling was interrupted by either a potent chemical inhibitor of QS or mutations in the lasI and rhlI AHL synthases of P. aeruginosa PAO1. These results show that AHLs are exchanged among bacteria in the alkaline gut of CWB larvae and contribute to disease caused by P. aeruginosa PAO1.


Subject(s)
Bacterial Physiological Phenomena , Gastrointestinal Tract/microbiology , Larva/microbiology , Lepidoptera/microbiology , Quorum Sensing , Acyl-Butyrolactones/metabolism , Animals , Bacterial Proteins/genetics , Genes, Reporter , Luminescent Proteins/biosynthesis , Luminescent Proteins/genetics , Molecular Sequence Data , Pantoea/genetics , Pantoea/isolation & purification , Pantoea/physiology , Pseudomonas Infections/microbiology , Pseudomonas aeruginosa/pathogenicity , Survival Analysis , Transcription Factors/genetics
7.
Chem Soc Rev ; 37(7): 1432-47, 2008 Jul.
Article in English | MEDLINE | ID: mdl-18568169

ABSTRACT

Bacteria are capable of "communicating" their local population densities via a process termed quorum sensing (QS). Gram-negative bacteria use N-acylated l-homoserine lactones (AHLs), in conjunction with their cognate LuxR-type receptors, as their primary signalling circuit for QS. In this critical review, we examine AHL signalling in Gram-negative bacteria with a primary focus on the design of non-natural AHLs, their structure-activity relationships, and their application in chemical biological approaches to study QS (72 references).


Subject(s)
4-Butyrolactone/analogs & derivatives , Cell Physiological Phenomena , Gram-Negative Bacteria/physiology , Quorum Sensing/physiology , Repressor Proteins/chemistry , Trans-Activators/chemistry , 4-Butyrolactone/chemistry , 4-Butyrolactone/metabolism , Acylation , Ligands , Molecular Structure , Repressor Proteins/metabolism , Structure-Activity Relationship , Trans-Activators/metabolism
8.
Chembiochem ; 9(3): 389-400, 2008 Feb 15.
Article in English | MEDLINE | ID: mdl-18224645

ABSTRACT

Bacterial quorum sensing is mediated by low molecular-weight signals and plays a critical role in both the pathogenesis of infectious disease and beneficial symbioses. There is significant interest in the development of synthetic ligands that can intercept bacterial quorum sensing signals and modulate these outcomes. Here, we report the design and comparative analysis of the effects of approximately 90 synthetic N-acylated homoserine lactones (AHLs) on quorum sensing in three Gram negative bacterial species and a critical examination of the structural features of these ligands that dictate agonistic and antagonistic activity, and selectivity for different R protein targets. These studies have revealed the most comprehensive set of structure-activity relationships to date that direct AHL-mediated quorum sensing and a new set of chemical probes with which to study this complex signaling process. Furthermore, this work provides a foundation on which to design next-generation quorum sensing modulators with improved activities and selectivities.


Subject(s)
4-Butyrolactone/analogs & derivatives , Quorum Sensing , 4-Butyrolactone/chemistry , Acylation , Molecular Structure
9.
Bioorg Med Chem Lett ; 18(10): 3072-5, 2008 May 15.
Article in English | MEDLINE | ID: mdl-18083553

ABSTRACT

The transcription factor QscR is a regulator of quorum sensing in Pseudomonas aeruginosa and plays a role in controlling virulence in this prevalent opportunistic pathogen. This study outlines the discovery of a set of synthetic N-acylated homoserine lactones that are capable of either activating or strongly inhibiting QscR in a cell-based reporter gene assay. We demonstrate that the synthetic antagonists inhibit ligand-dependent QscR binding to DNA. Several of these ligands can selectively modulate QscR instead of LasR, or modulate the activity of both receptors, and represent new chemical tools to study the hierarchy of quorum-sensing signaling in P. aeruginosa.


Subject(s)
Acyl-Butyrolactones/chemical synthesis , Acyl-Butyrolactones/pharmacology , Bacterial Proteins/agonists , Bacterial Proteins/antagonists & inhibitors , Drug Design , Pseudomonas aeruginosa/drug effects , Repressor Proteins/agonists , Repressor Proteins/antagonists & inhibitors , Acyl-Butyrolactones/chemistry , Anti-Bacterial Agents/chemical synthesis , Anti-Bacterial Agents/chemistry , Anti-Bacterial Agents/pharmacology , Bacterial Proteins/metabolism , DNA, Bacterial/metabolism , Dose-Response Relationship, Drug , Ligands , Microbial Sensitivity Tests , Models, Molecular , Molecular Structure , Pseudomonas aeruginosa/metabolism , Repressor Proteins/metabolism , Signal Transduction/drug effects , Virulence Factors/agonists , Virulence Factors/antagonists & inhibitors , Virulence Factors/metabolism
10.
J Am Chem Soc ; 129(44): 13613-25, 2007 Nov 07.
Article in English | MEDLINE | ID: mdl-17927181

ABSTRACT

Bacteria use a language of low molecular weight ligands to assess their population densities in a process called quorum sensing. This chemical signaling process plays a pivotal role both in the pathogenesis of infectious disease and in beneficial symbioses. There is intense interest in the development of synthetic ligands that can intercept quorum-sensing signals and attenuate these divergent outcomes. Both broad-spectrum and species-selective modulators of quorum sensing hold significant value as small-molecule tools for fundamental studies of this complex cell-cell signaling process and for future biomedical and environmental applications. Here, we report the design and synthesis of focused collections of non-native N-acylated homoserine lactones and the systematic evaluation of these approximately 90 ligands across three Gram-negative bacterial species: the pathogens Agrobacterium tumefaciens and Pseudomonas aeruginosa; the model symbiont Vibrio fischeri. This study is the first to report and compare the activities of a set of ligands across multiple species and has revealed some of the most potent synthetic modulators of quorum sensing to date. Moreover, several of these ligands exhibit agonistic or antagonistic activity in all three species, while other ligands are only active in one or two species. Analysis of the screening data revealed that at least a subset of these ligands modulate quorum sensing via a partial agonism mechanism. We also demonstrate that selected ligands can either inhibit or promote the production of elastase B, a key virulence factor in wild-type P. aeruginosa, depending on their concentrations. Overall, this work provides broad insights into the molecular features required for small-molecule inhibition or activation of quorum sensing in Gram-negative bacteria. In addition, this study has supplied an expansive set of chemical tools for the further investigation of quorum-sensing pathways and responses.


Subject(s)
4-Butyrolactone/analogs & derivatives , Agrobacterium tumefaciens/drug effects , Aliivibrio fischeri/drug effects , Anti-Bacterial Agents/pharmacology , Pseudomonas aeruginosa/drug effects , Quorum Sensing/drug effects , 4-Butyrolactone/chemical synthesis , 4-Butyrolactone/chemistry , 4-Butyrolactone/pharmacology , Acetylation , Agrobacterium tumefaciens/chemistry , Agrobacterium tumefaciens/genetics , Aliivibrio fischeri/chemistry , Aliivibrio fischeri/genetics , Anti-Bacterial Agents/chemical synthesis , Anti-Bacterial Agents/chemistry , Combinatorial Chemistry Techniques , Drug Resistance, Microbial , Gene Expression Regulation, Bacterial/drug effects , Gene Expression Regulation, Bacterial/genetics , Ligands , Microbial Sensitivity Tests , Molecular Conformation , Molecular Weight , Pseudomonas aeruginosa/chemistry , Pseudomonas aeruginosa/genetics , Species Specificity , Stereoisomerism , Structure-Activity Relationship
12.
ACS Chem Biol ; 2(5): 315-9, 2007 May 22.
Article in English | MEDLINE | ID: mdl-17480049

ABSTRACT

Bacteria monitor their population densities using low-molecular-weight ligands in a process known as quorum sensing. At sufficient cell densities, bacteria can change their mode of growth and behave as multicellular communities that play critical roles in both beneficial symbioses and the pathogenesis of infectious disease. The development of non-native ligands that can block quorum-sensing signals has emerged as a promising new strategy to attenuate these divergent outcomes. Here, we report that N-phenylacetanoyl-L-homoserine lactones are capable of either inhibiting or, in some cases, strongly inducing quorum sensing in the bacterial symbiont Vibrio fischeri. Moreover, simple structural modifications to these ligands have remarkable effects on activity. These studies have revealed one of the first synthetic superagonists of quorum sensing, N-(3-nitro-phenylacetanoyl)-L-homoserine lactone. Together, these ligands represent a powerful new class of chemical probes with the potential to significantly expand the current understanding of quorum sensing and its role in host/bacteria interactions.


Subject(s)
4-Butyrolactone/analogs & derivatives , Aliivibrio fischeri/drug effects , Anti-Bacterial Agents , 4-Butyrolactone/agonists , 4-Butyrolactone/antagonists & inhibitors , 4-Butyrolactone/chemical synthesis , 4-Butyrolactone/chemistry , 4-Butyrolactone/pharmacology , Aliivibrio fischeri/genetics , Aliivibrio fischeri/metabolism , Anti-Bacterial Agents/chemical synthesis , Anti-Bacterial Agents/chemistry , Anti-Bacterial Agents/pharmacology , Gene Expression Regulation, Bacterial/drug effects , Ligands , Molecular Structure , Structure-Activity Relationship
13.
J Bacteriol ; 189(11): 4320-4, 2007 Jun.
Article in English | MEDLINE | ID: mdl-17384185

ABSTRACT

The Burkholderia pseudomallei KHW quorum-sensing systems produced N-octanoyl-homoserine lactone, N-decanoyl-homoserine lactone, N-(3-hydroxy)-octanoyl-homoserine lactone, N-(3-hydroxy)-decanoyl-homoserine lactone, N-(3-oxo)-decanoyl-homoserine lactone, and N-(3-oxo)-tetradecanoyl-homoserine lactone. The extracellular secretion of these acyl-homoserine lactones is dependent absolutely on the function of the B. pseudomallei BpeAB-OprB efflux pump.


Subject(s)
Bacterial Outer Membrane Proteins/metabolism , Burkholderia pseudomallei/metabolism , Quorum Sensing/physiology , 4-Butyrolactone/analogs & derivatives , 4-Butyrolactone/metabolism , Bacterial Outer Membrane Proteins/genetics , Burkholderia pseudomallei/genetics , Burkholderia pseudomallei/physiology , Chromatography, High Pressure Liquid , Gene Expression Regulation, Bacterial , Homoserine/analogs & derivatives , Homoserine/metabolism , Lactones/metabolism , Mutation , Quorum Sensing/genetics
14.
J Am Chem Soc ; 127(37): 12762-3, 2005 Sep 21.
Article in English | MEDLINE | ID: mdl-16159245

ABSTRACT

Bacteria monitor their local population densities using small molecules (or autoinducers) in a process known as quorum sensing. Here, we report a new and efficient synthetic route to naturally occurring bacterial autoinducers [N-acyl l-homoserine lactones (AHLs)] that is readily amenable to the synthesis of analogues. This route has been applied in the first synthesis of a library of non-native AHLs. Evaluation of these compounds in bacterial reporter gene and biofilm assays has revealed a potent set of quorum sensing antagonists. These ligands will serve as valuable new tools to explore the role of quorum sensing in bacterial pathogenesis.


Subject(s)
Bacterial Proteins/antagonists & inhibitors , Biofilms/growth & development , Enzyme Inhibitors/pharmacology , Homoserine/pharmacology , Lactones/pharmacology , Biofilms/drug effects , Enzyme Inhibitors/chemical synthesis , Enzyme Inhibitors/chemistry , Homoserine/chemical synthesis , Homoserine/chemistry , Lactones/chemical synthesis , Lactones/chemistry , Ligands , Microwaves , Molecular Conformation , Pseudomonas aeruginosa/drug effects
15.
Inorg Chem ; 41(10): 2795-8, 2002 May 20.
Article in English | MEDLINE | ID: mdl-12005505

ABSTRACT

We performed ab initio calculations on the (Na(2)[CAl(4)])(2) dimer in order to test if the two CAl(4)(2-) groups react to form the more stable dimeric structure, or if the two CAl(4)(2-) groups remain separated in a true dimeric structure. Working at the B3LYP/6-311+G* level of theory (previously found to be satisfactory in our earlier calculations with CAl(4)(-) and Na[CAl(4)](-)), we established that structures with the C-C bond are higher in energy than the structures with two isolated structural CAl(4)(-) units separated by more than 5 A with their structural and electronic integrity preserved. However, alternative structures involving reaction between two CAl(4)(2-) groups forming a C(2)Al(8)(4-) cluster without the C-C bond are higher in energy, but they are still competitive with the true dimeric structure. While we found alternative structures of Na(4)C(2)Al(8) with the energy comparable to that of the true dimeric structure, we hope that the solid ionic salt with the pentaatomic tetracoordinate planar carbon [CAl(4)](2)(-) building block can be synthesized.

SELECTION OF CITATIONS
SEARCH DETAIL
...