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Murray EJ, Dubern JF, Chan WC, Chhabra SR, Williams P. A Pseudomonas aeruginosa PQS quorum-sensing system inhibitor with anti-staphylococcal activity sensitizes polymicrobial biofilms to tobramycin. Cell Chem Biol 2022; 29:1187-1199.e6. [PMID: 35259345 PMCID: PMC9605878 DOI: 10.1016/j.chembiol.2022.02.007] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Revised: 07/16/2021] [Accepted: 02/15/2022] [Indexed: 12/23/2022]
Abstract
As single- and mixed-species biofilms, Staphylococcus aureus and Pseudomonas aeruginosa cause difficult-to-eradicate chronic infections. In P. aeruginosa, pseudomonas quinolone (PQS)-dependent quorum sensing regulates virulence and biofilm development that can be attenuated via antagonists targeting the transcriptional regulator PqsR (MvfR). Here, we exploited a quinazolinone (QZN) library including PqsR agonists and antagonists for their activity against S. aureus alone, when co-cultured with P. aeruginosa, and in combination with the aminoglycoside tobramycin. The PqsR inhibitor, QZN 34 killed planktonic Gram-positives but not Gram-negatives. QZN 34 prevented S. aureus biofilm formation, severely damaged established S. aureus biofilms, and perturbed P. aeruginosa biofilm development. Although P. aeruginosa protected S. aureus from tobramycin in mixed biofilms, the combination of aminoglycoside antibiotic with QZN 34 eradicated the mixed-species biofilm. The mechanism of action of QZN 34 toward Gram-positive bacteria is shown to involve membrane perturbation and dissipation of transmembrane potential.
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Murray EJ, Crowley RC, Truman A, Clarke SR, Cottam JA, Jadhav GP, Steele VR, O'Shea P, Lindholm C, Cockayne A, Chhabra SR, Chan WC, Williams P. Targeting Staphylococcus aureus quorum sensing with nonpeptidic small molecule inhibitors. J Med Chem 2014; 57:2813-9. [PMID: 24592914 PMCID: PMC4010551 DOI: 10.1021/jm500215s] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
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A series of 3-oxo-C12-HSL,
tetramic acid, and tetronic
acid analogues were synthesized to gain insights into the structural
requirements for quorum sensing inhibition in Staphylococcus
aureus. Compounds active against agr were
noncompetitive inhibitors of the autoinducing peptide (AIP) activated
AgrC receptor, by altering the activation efficacy of the cognate
AIP-1. They appeared to act as negative allosteric modulators and
are exemplified by 3-tetradecanoyltetronic acid 17, which
reduced nasal cell colonization and arthritis in a murine infection
model.
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Thierbach S, Bui N, Zapp J, Chhabra SR, Kappl R, Fetzner S. Substrate-assisted O2 activation in a cofactor-independent dioxygenase. ACTA ACUST UNITED AC 2014; 21:217-25. [PMID: 24388758 DOI: 10.1016/j.chembiol.2013.11.013] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2013] [Revised: 11/22/2013] [Accepted: 11/27/2013] [Indexed: 11/29/2022]
Abstract
In contrast to the majority of O2-activating enzymes, which depend on an organic cofactor or a metal ion for catalysis, a particular group of structurally unrelated oxygenases is functional without any cofactor. In this study, we characterized the mechanism of O2 activation in the reaction pathway of a cofactor-independent dioxygenase with an α/β-hydrolase fold, which catalyzes the oxygenolytic cleavage of 2-alkyl-3-hydroxy-4(1H)-quinolones. Chemical analysis and electron paramagnetic resonance spectroscopic data revealed that O2 activation in the enzyme's active site is substrate-assisted, relying on single electron transfer from the bound substrate anion to O2 to form a radical pair, which recombines to a C2-peroxide intermediate. Thus, an oxygenase can function without a cofactor, if the organic substrate itself, after activation to a (carb)anion by an active-site base, is intrinsically reactive toward molecular oxygen.
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Ilangovan A, Fletcher M, Rampioni G, Pustelny C, Rumbaugh K, Heeb S, Cámara M, Truman A, Chhabra SR, Emsley J, Williams P. Structural basis for native agonist and synthetic inhibitor recognition by the Pseudomonas aeruginosa quorum sensing regulator PqsR (MvfR). PLoS Pathog 2013; 9:e1003508. [PMID: 23935486 PMCID: PMC3723537 DOI: 10.1371/journal.ppat.1003508] [Citation(s) in RCA: 159] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2012] [Accepted: 06/05/2013] [Indexed: 12/02/2022] Open
Abstract
Bacterial populations co-ordinate gene expression collectively through quorum sensing (QS), a cell-to-cell communication mechanism employing diffusible signal molecules. The LysR-type transcriptional regulator (LTTR) protein PqsR (MvfR) is a key component of alkyl-quinolone (AQ)-dependent QS in Pseudomonas aeruginosa. PqsR is activated by 2-alkyl-4-quinolones including the Pseudomonas quinolone signal (PQS; 2-heptyl-3-hydroxy-4(1H)-quinolone), its precursor 2-heptyl-4-hydroxyquinoline (HHQ) and their C9 congeners, 2-nonyl-3-hydroxy-4(1H)-quinolone (C9-PQS) and 2-nonyl-4-hydroxyquinoline (NHQ). These drive the autoinduction of AQ biosynthesis and the up-regulation of key virulence determinants as a function of bacterial population density. Consequently, PqsR constitutes a potential target for novel antibacterial agents which attenuate infection through the blockade of virulence. Here we present the crystal structures of the PqsR co-inducer binding domain (CBD) and a complex with the native agonist NHQ. We show that the structure of the PqsR CBD has an unusually large ligand-binding pocket in which a native AQ agonist is stabilized entirely by hydrophobic interactions. Through a ligand-based design strategy we synthesized and evaluated a series of 50 AQ and novel quinazolinone (QZN) analogues and measured the impact on AQ biosynthesis, virulence gene expression and biofilm development. The simple exchange of two isosteres (OH for NH2) switches a QZN agonist to an antagonist with a concomitant impact on the induction of bacterial virulence factor production. We also determined the complex crystal structure of a QZN antagonist bound to PqsR revealing a similar orientation in the ligand binding pocket to the native agonist NHQ. This structure represents the first description of an LTTR-antagonist complex. Overall these studies present novel insights into LTTR ligand binding and ligand-based drug design and provide a chemical scaffold for further anti-P. aeruginosa virulence drug development by targeting the AQ receptor PqsR. Populations of bacterial cells collectively co-ordinate their activities through cell-to-cell communication via the production and sensing of signal molecules. This is called quorum sensing (QS) and in many bacteria, QS controls the expression of virulence genes, the products of which damage host tissues. Consequently, QS systems are potential targets for antimicrobial agents which do not kill bacteria but instead block their ability to cause disease. Pseudomonas aeruginosa causes a wide range of human infections and produces an armoury of virulence factors. Since many of these are controlled by alkylquinolone (AQ)-dependent QS, we determined the crystal structure of the AQ receptor (PqsR) in order to visualize the shape of the AQ-binding site and better design PqsR inhibitors which compete for the AQ binding site and so block QS. This work in conjunction with the chemical synthesis of AQ analogues resulted in the discovery of potent quinazolinone inhibitors of PqsR. These blocked AQ and virulence factor production in P. aeruginosa as well as biofilm development. Our studies present novel insights into the structure of PqsR and create further opportunities for target-based antibacterial drug development.
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Niewerth H, Bergander K, Chhabra SR, Williams P, Fetzner S. Synthesis and biotransformation of 2-alkyl-4(1H)-quinolones by recombinant Pseudomonas putida KT2440. Appl Microbiol Biotechnol 2011; 91:1399-408. [PMID: 21670979 DOI: 10.1007/s00253-011-3378-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2011] [Revised: 05/09/2011] [Accepted: 05/09/2011] [Indexed: 11/29/2022]
Abstract
2-Alkyl-4(1H)-quinolones (AQs) and related derivatives, which exhibit a variety of biological properties, are secondary metabolites produced by, e.g., Pseudomonas and Burkholderia spp. Due to their main role as signaling molecules in the quorum sensing system of Pseudomonas aeruginosa, 2-heptyl-4(1H)-quinolone (HHQ) and its 3-hydroxy derivative, termed the "Pseudomonas quinolone signal" (PQS), have received considerable attention. Since chemical synthesis of different AQs is complex, we assessed the applicability of recombinant P. putida KT2440 strains for the biosynthetic production of AQs. In mineral salts medium supplemented with octanoate and anthranilate, batch cultures of P. putida KT2440 [pBBR-pqsABCD] produced about 45 μM HHQ, 30% and 70% of which were localized in the culture supernatant and methanolic cell extract, respectively. 2,4-Dihydroxyquinoline and minor amounts of C₃- to C₁₃-saturated and C₇:₁ to C₁₃:₁ monounsaturated AQs were formed as by-products. Mass spectrometry and nuclear magnetic resonance analyses spectroscopy indicated that unsaturated AQs having the same molecular mass are cis and trans isomers rather than position isomers, with the double bond located between the α and β carbon of the alkyl chain. Supplementing the cultures with hexanoate instead of octanoate shifted the AQ profile towards increased formation of C₅-AQ. Individual AQs can be prepared from concentrated methanolic extracts by preparative high-performance liquid chromatography (HPLC). Regioselective hydroxylation of HHQ to PQS can be achieved in > 90% yield by biotransformation with P. putida KT2440 [pBBR-pqsH]. PQS can be isolated from methanolic cell extracts by HPLC, or be precipitated as Fe(III)-PQS complex. Preparation of a library of AQs will facilitate studies on the biological functions of these compounds.
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Heeb S, Fletcher MP, Chhabra SR, Diggle SP, Williams P, Cámara M. Quinolones: from antibiotics to autoinducers. FEMS Microbiol Rev 2011; 35:247-74. [PMID: 20738404 PMCID: PMC3053476 DOI: 10.1111/j.1574-6976.2010.00247.x] [Citation(s) in RCA: 386] [Impact Index Per Article: 29.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Since quinine was first isolated, animals, plants and microorganisms producing a wide variety of quinolone compounds have been discovered, several of which possess medicinally interesting properties ranging from antiallergenic and anticancer to antimicrobial activities. Over the years, these have served in the development of many synthetic drugs, including the successful fluoroquinolone antibiotics. Pseudomonas aeruginosa and related bacteria produce a number of 2-alkyl-4(1H)-quinolones, some of which exhibit antimicrobial activity. However, quinolones such as the Pseudomonas quinolone signal and 2-heptyl-4-hydroxyquinoline act as quorum-sensing signal molecules, controlling the expression of many virulence genes as a function of cell population density. Here, we review selectively this extensive family of bicyclic compounds, from natural and synthetic antimicrobials to signalling molecules, with a special emphasis on the biology of P. aeruginosa. In particular, we review their nomenclature and biochemistry, their multiple properties as membrane-interacting compounds, inhibitors of the cytochrome bc1 complex and iron chelators, as well as the regulation of their biosynthesis and their integration into the intricate quorum-sensing regulatory networks governing virulence and secondary metabolite gene expression.
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Jadhav GP, Chhabra SR, Telford G, Hooi DSW, Righetti K, Williams P, Kellam B, Pritchard DI, Fischer PM. Immunosuppressive but non-LasR-inducing analogues of the Pseudomonas aeruginosa quorum-sensing molecule N-(3-oxododecanoyl)-l-homoserine lactone. J Med Chem 2011; 54:3348-59. [PMID: 21488685 DOI: 10.1021/jm2001019] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The Pseudomonas aeruginosa quorum-sensing molecule N-(3-oxododecanoyl)-l-homoserine lactone (1) is involved not only in bacterial activation but also in subversion of the host immune system, and this compound might thus be used as a template to design immunosuppressive agents, provided derivatives devoid of quorum-sensing activity could be discovered. By use of a leukocyte proliferation assay and a newly developed bioluminescent P. aeruginosa reporter assay, systematic modification of 1 allowed us to delineate the bacterial LasR-induction and host immunosuppressive activities. The main determinant is replacement of the methylene group proximal to the β-ketoamide in the acyl chain of 1 with functions containing heteroatoms, especially an NH group. This modification can be combined with replacement of the homoserine lactone system in 1 with stable cyclic groups. For example, we found the simple compound N(1)-(5-chloro-2-hydroxyphenyl)-N(3)-octylmalonamide (25d) to be over twice as potent as 1 as an immune suppressor while displaying LasR-induction antagonist activity.
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Chan KG, Atkinson S, Mathee K, Sam CK, Chhabra SR, Cámara M, Koh CL, Williams P. Characterization of N-acylhomoserine lactone-degrading bacteria associated with the Zingiber officinale (ginger) rhizosphere: co-existence of quorum quenching and quorum sensing in Acinetobacter and Burkholderia. BMC Microbiol 2011; 11:51. [PMID: 21385437 PMCID: PMC3062576 DOI: 10.1186/1471-2180-11-51] [Citation(s) in RCA: 126] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2010] [Accepted: 03/08/2011] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND Cell-to-cell communication (quorum sensing (QS)) co-ordinates bacterial behaviour at a population level. Consequently the behaviour of a natural multi-species community is likely to depend at least in part on co-existing QS and quorum quenching (QQ) activities. Here we sought to discover novel N-acylhomoserine lactone (AHL)-dependent QS and QQ strains by investigating a bacterial community associated with the rhizosphere of ginger (Zingiber officinale) growing in the Malaysian rainforest. RESULTS By using a basal growth medium containing N-(3-oxohexanoyl)homoserine lactone (3-oxo-C6-HSL) as the sole source of carbon and nitrogen, the ginger rhizosphere associated bacteria were enriched for strains with AHL-degrading capabilities. Three isolates belonging to the genera Acinetobacter (GG2), Burkholderia (GG4) and Klebsiella (Se14) were identified and selected for further study. Strains GG2 and Se14 exhibited the broadest spectrum of AHL-degrading activities via lactonolysis while GG4 reduced 3-oxo-AHLs to the corresponding 3-hydroxy compounds. In GG2 and GG4, QQ was found to co-exist with AHL-dependent QS and GG2 was shown to inactivate both self-generated and exogenously supplied AHLs. GG2, GG4 and Se14 were each able to attenuate virulence factor production in both human and plant pathogens. CONCLUSIONS Collectively our data show that ginger rhizosphere bacteria which make and degrade a wide range of AHLs are likely to play a collective role in determining the QS-dependent phenotype of a polymicrobial community.
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Ortori CA, Dubern JF, Chhabra SR, Cámara M, Hardie K, Williams P, Barrett DA. Simultaneous quantitative profiling of N-acyl-L-homoserine lactone and 2-alkyl-4(1H)-quinolone families of quorum-sensing signaling molecules using LC-MS/MS. Anal Bioanal Chem 2010; 399:839-50. [PMID: 21046079 DOI: 10.1007/s00216-010-4341-0] [Citation(s) in RCA: 141] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2010] [Revised: 10/08/2010] [Accepted: 10/12/2010] [Indexed: 11/29/2022]
Abstract
An LC-MS/MS method, using positive mode electrospray ionization, for the simultaneous, quantitative and targeted profiling of the N-acyl-L-homoserine lactone (AHL) and 2-alkyl 4-(1H)-quinolone (AQ) families of bacterial quorum-sensing signaling molecules (QSSMs) is presented. This LC-MS/MS technique was applied to determine the relative molar ratios of AHLs and AQs produced by Pseudomonas aeruginosa and the consequences of mutating individual or multiple QSSM synthase genes (lasI, rhlI, pqsA) on AHL and AQ profiles and concentrations. The AHL profile of P. aeruginosa was dominated by N-butanoyl-L-homoserine lactone (C4-HSL) with lesser concentrations of N-hexanoyl-L-homoserine lactone (C6-HSL) and 3-oxo-substituted longer chain AHLs including N-(3-oxodecanoyl)-L-homoserine lactone (3-oxo-C10-HSL) and N-(3-oxododecanoyl)-L-homoserine lactone (3-oxo-C12-HSL). The AQ profile of P. aeruginosa comprised the C7 and C9 long alkyl chain AQs including 2-heptyl-4-hydroxyquinoline (HHQ), 2-nonyl-4-hydroxyquinoline, the "pseudomonas quinolone signal" (2-heptyl-3-hydroxy-4-quinolone) and the N-oxides, 2-heptyl-4-hydroxyquinoline N-oxide and 2-nonyl-4-hydroxyquinoline N-oxide. Application of the method showed significant effects of growth medium type on the ratio and the nature of the QSSMs synthesized and the dramatic effect of single, double and triple mutations in the P. aeruginosa QS synthase genes. The LC-MS/MS methodology is applicable in organisms where either or both AHL and AQ QSSMs are produced and can provide comprehensive profiles and concentrations from a single sample.
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Pustelny C, Albers A, Büldt-Karentzopoulos K, Parschat K, Chhabra SR, Cámara M, Williams P, Fetzner S. Dioxygenase-mediated quenching of quinolone-dependent quorum sensing in Pseudomonas aeruginosa. ACTA ACUST UNITED AC 2010; 16:1259-67. [PMID: 20064436 DOI: 10.1016/j.chembiol.2009.11.013] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2009] [Revised: 10/29/2009] [Accepted: 11/02/2009] [Indexed: 01/19/2023]
Abstract
2-Heptyl-3-hydroxy-4(1H)-quinolone (PQS) is a quorum-sensing signal molecule used by Pseudomonas aeruginosa. The structural similarity between 3-hydroxy-2-methyl-4(1H)-quinolone, the natural substrate for the 2,4-dioxygenase, Hod, and PQS prompted us to investigate whether Hod quenched PQS signaling. Hod is capable of catalyzing the conversion of PQS to N-octanoylanthranilic acid and carbon monoxide. In P. aeruginosa PAO1 cultures, exogenously supplied Hod protein reduced expression of the PQS biosynthetic gene pqsA, expression of the PQS-regulated virulence determinants lectin A, pyocyanin, and rhamnolipids, and virulence in planta. However, the proteolytic cleavage of Hod by extracellular proteases, competitive inhibition by the PQS precursor 2-heptyl-4(1H)-quinolone, and PQS binding to rhamnolipids reduced the efficiency of Hod as a quorum-quenching agent. Nevertheless, these data indicate that enzyme-mediated PQS inactivation has potential as an antivirulence strategy against P. aeruginosa.
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Cooley M, Chhabra SR, Williams P. N-Acylhomoserine lactone-mediated quorum sensing: a twist in the tail and a blow for host immunity. ACTA ACUST UNITED AC 2009; 15:1141-7. [PMID: 19022174 DOI: 10.1016/j.chembiol.2008.10.010] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2008] [Revised: 10/17/2008] [Accepted: 10/22/2008] [Indexed: 12/31/2022]
Abstract
Communication through quorum sensing (QS) enables bacterial populations to coordinate their behavior. Recent work on N-acylhomoserine lactone-mediated QS has revealed that some soil bacteria exploit host-derived substrates to generate an alternative N-substituted homoserine lactone. New light has also been shed on the mechanism by which N-(3-oxo-dodecanoyl)-L-homoserine lactone modulates host inflammatory signaling pathways to promote bacterial survival.
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Diggle SP, Matthijs S, Wright VJ, Fletcher MP, Chhabra SR, Lamont IL, Kong X, Hider RC, Cornelis P, Cámara M, Williams P. The Pseudomonas aeruginosa 4-quinolone signal molecules HHQ and PQS play multifunctional roles in quorum sensing and iron entrapment. ACTA ACUST UNITED AC 2008; 14:87-96. [PMID: 17254955 DOI: 10.1016/j.chembiol.2006.11.014] [Citation(s) in RCA: 346] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2006] [Revised: 11/20/2006] [Accepted: 11/27/2006] [Indexed: 12/20/2022]
Abstract
Pseudomonas aeruginosa produces 2-heptyl-3-hydroxy-4(1H)-quinolone (PQS), a quorum-sensing (QS) signal that regulates numerous virulence genes including those involved in iron scavenging. Biophysical analysis revealed that 2-alkyl-3-hydroxy-4-quinolones form complexes with iron(III) at physiological pH. The overall stability constant of 2-methyl-3-hydroxy-4-quinolone iron(III) complex was log beta(3) = 36.2 with a pFe(3+) value of 16.6 at pH 7.4. PQS was found to operate via at least three distinct signaling pathways, and its precursor, 2-heptyl-4-quinolone (HHQ), which does not form an iron complex, was discovered to function as an autoinducer molecule per se. When PQS was supplied to a P. aeruginosa mutant unable to make pyoverdine or pyochelin, PQS associated with the cell envelope and inhibited bacterial growth, a finding that reveals a secondary function for PQS in iron entrapment to facilitate siderophore-mediated iron delivery.
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Fletcher MP, Diggle SP, Crusz SA, Chhabra SR, Cámara M, Williams P. A dual biosensor for 2-alkyl-4-quinolone quorum-sensing signal molecules. Environ Microbiol 2007; 9:2683-93. [DOI: 10.1111/j.1462-2920.2007.01380.x] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Ritchie AJ, Whittall C, Lazenby JJ, Chhabra SR, Pritchard DI, Cooley MA. The immunomodulatory
Pseudomonas aeruginosa
signalling molecule
N
‐(3‐oxododecanoyl)‐
l
‐homoserine lactone enters mammalian cells in an unregulated fashion. Immunol Cell Biol 2007; 85:596-602. [PMID: 17607318 DOI: 10.1038/sj.icb.7100090] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The Pseudomonas aeruginosa quorum-sensing signal molecule N-3-oxododecanoyl)-L-homoserine lactone (OdDHL) has been reported to affect the function of a wide range of mammalian cell types, including cells of the immune system. In T cells, it has been reported to inhibit the production of most cytokines, and it has been reported to inhibit the function of antigen-presenting cells. The intracellular target of OdDHL in these cells remains to be identified, although the lipophilic nature of the molecule suggested that the target could be membrane associated. We explored the association of radiolabelled OdDHL with the membrane and cytoplasm of Jurkat T-cell lines and of primary murine T cells and dendritic cells. We found that not only did 3H-OdDHL enter the cytoplasm of Jurkat cells without disproportionate association with the cell membrane, it also reached maximum levels in the cytoplasm very quickly, and that the intracellular concentration was proportional to the extracellular concentration. Similar results were obtained when 3H-OdDHL was incubated with primary murine T cells or cultured dendritic cells. In addition, we show that the cellular distribution of OdDHL does not significantly alter after stimulation of Jurkat cells or primary murine CD4 T cells with immobilized anti-CD3, with little activity being associated with nuclear fractions. Together, these data strongly suggest that OdDHL enters mammalian cells by passive mechanisms, and that it does not preferentially associate with the membrane or nucleus upon T-cell receptor ligation.
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Diggle SP, Lumjiaktase P, Dipilato F, Winzer K, Kunakorn M, Barrett DA, Chhabra SR, Cámara M, Williams P. Functional genetic analysis reveals a 2-Alkyl-4-quinolone signaling system in the human pathogen Burkholderia pseudomallei and related bacteria. ACTA ACUST UNITED AC 2006; 13:701-10. [PMID: 16873018 DOI: 10.1016/j.chembiol.2006.05.006] [Citation(s) in RCA: 142] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2006] [Revised: 04/27/2006] [Accepted: 05/01/2006] [Indexed: 10/24/2022]
Abstract
Pseudomonas aeruginosa synthesizes diverse 2-alkyl-4(1H)-quinolones (AHQs), including the signaling molecule 2-heptyl-3-hydroxy-4(1H)-quinolone (PQS), via the pqsABCDE locus. By examining the genome databases, homologs of the pqs genes were identified in other bacteria. However, apart from P. aeruginosa, only Burkholderia pseudomallei and B. thailandensis contained a complete pqsA-E operon (termed hhqA-E). By introducing the B. pseudomallei hhqA and hhqE genes into P. aeruginosa pqsA and pqsE mutants, we show that they are functionally conserved and restore virulence factor and PQS production. B. pseudomallei, B. thailandensis, B. cenocepacia, and P. putida each produced 2-heptyl-4(1H)-quinolone (HHQ), but not PQS. Mutation of hhqA in B. pseudomallei resulted in the loss of AHQ production, altered colony morphology, and enhanced elastase production, which was reduced to parental levels by exogenous HHQ. These data reveal a role for AHQs in bacterial cell-to-cell communication beyond that seen in P. aeruginosa.
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Uroz S, Oger P, Chhabra SR, Cámara M, Williams P, Dessaux Y. N-acyl homoserine lactones are degraded via an amidolytic activity in Comamonas sp. strain D1. Arch Microbiol 2006; 187:249-56. [PMID: 17136382 DOI: 10.1007/s00203-006-0186-5] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2006] [Revised: 10/05/2006] [Accepted: 10/09/2006] [Indexed: 11/27/2022]
Abstract
Comamonas strain D1 enzymatically inactivates quorum-sensing (QS) signal molecules of the N-acyl homoserine lactone (N-AHSL) family, and exhibits the broadest inactivation range of known bacteria. It degrades N-AHSL with acyl-side chains ranging from 4 to 16 carbons, with or without 3-oxo or 3-hydroxy substitutions. N-AHSL degradation yields HSL but not N-acyl homoserine: strain D1 therefore harbors an amidohydrolase activity. Strain D1 is the fifth bacterium species in which an N-AHSL amidohydrolase is described. Consistent with its N-AHSL degradation ability, strain D1 efficiently quenches various QS-dependent functions in other bacteria, such as violacein production by Chromobacterium violaceum and pathogenicity and antibiotic production in Pectobacterium.
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Ortori CA, Atkinson S, Chhabra SR, Cámara M, Williams P, Barrett DA. Comprehensive profiling of N-acylhomoserine lactones produced by Yersinia pseudotuberculosis using liquid chromatography coupled to hybrid quadrupole–linear ion trap mass spectrometry. Anal Bioanal Chem 2006; 387:497-511. [PMID: 16967185 DOI: 10.1007/s00216-006-0710-0] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2006] [Revised: 07/24/2006] [Accepted: 07/25/2006] [Indexed: 10/24/2022]
Abstract
A method for the comprehensive profiling of the N-acylhomoserine lactone (AHL) family of bacterial quorum-sensing molecules is presented using liquid chromatography (LC) coupled to hybrid quadrupole-linear ion trap (QqQLIT) mass spectrometry. Information-dependent acquisition (IDA), using triggered combinations of triple-quadrupole and linear ion trap modes in the same LC-MS/MS run, was used to simultaneously screen, quantify and identify multiple AHLs in a single sample. This MS method uses common AHL fragment ions attributed to the homoserine moiety and the 3-oxo-, 3-hydroxy- or unsubstituted acyl side chains, to identify unknown AHLs in cell-free culture supernatants in an unbiased manner. This LC-MS technique was applied to determine the relative molar ratios of AHLs produced by Yersinia pseudotuberculosis and the consequences of inactivating by mutation either or both of the AHL synthase genes (ypsI and ytbI) on AHL profile and concentration. The Y. pseudotuberculosis wild type but not the ypsI ytbI double mutant produced at least 24 different AHLs with acyl chains ranging from C4 to C15 with or without 3-oxo or 3-hydroxy substituents. YtbI, in contrast to YpsI, could direct the synthesis of all of the AHLs identified. The most abundant and hence most biologically relevant Y. pseudotuberculosis AHLs were found to be the 3-oxo-substituted C6, C7 and C8 AHLs and the unsubstituted C6 and C8 compounds. The LC-QqQLIT methodology is broadly applicable to quorum-sensing signal molecule analysis and can provide comprehensive AHL profiles and concentrations from a single sample and simultaneously collect confirmatory spectra for each AHL identified.
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Chhabra SR, He Q, Huang KH, Gaucher SP, Alm EJ, He Z, Hadi MZ, Hazen TC, Wall JD, Zhou J, Arkin AP, Singh AK. Global analysis of heat shock response in Desulfovibrio vulgaris Hildenborough. J Bacteriol 2006; 188:1817-28. [PMID: 16484192 PMCID: PMC1426554 DOI: 10.1128/jb.188.5.1817-1828.2006] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Desulfovibrio vulgaris Hildenborough belongs to a class of sulfate-reducing bacteria (SRB) and is found ubiquitously in nature. Given the importance of SRB-mediated reduction for bioremediation of metal ion contaminants, ongoing research on D. vulgaris has been in the direction of elucidating regulatory mechanisms for this organism under a variety of stress conditions. This work presents a global view of this organism's response to elevated growth temperature using whole-cell transcriptomics and proteomics tools. Transcriptional response (1.7-fold change or greater; Z >/= 1.5) ranged from 1,135 genes at 15 min to 1,463 genes at 120 min for a temperature up-shift of 13 degrees C from a growth temperature of 37 degrees C for this organism and suggested both direct and indirect modes of heat sensing. Clusters of orthologous group categories that were significantly affected included posttranslational modifications; protein turnover and chaperones (up-regulated); energy production and conversion (down-regulated), nucleotide transport, metabolism (down-regulated), and translation; ribosomal structure; and biogenesis (down-regulated). Analysis of the genome sequence revealed the presence of features of both negative and positive regulation which included the CIRCE element and promoter sequences corresponding to the alternate sigma factors sigma(32) and sigma(54). While mechanisms of heat shock control for some genes appeared to coincide with those established for Escherichia coli and Bacillus subtilis, the presence of unique control schemes for several other genes was also evident. Analysis of protein expression levels using differential in-gel electrophoresis suggested good agreement with transcriptional profiles of several heat shock proteins, including DnaK (DVU0811), HtpG (DVU2643), HtrA (DVU1468), and AhpC (DVU2247). The proteomics study also suggested the possibility of posttranslational modifications in the chaperones DnaK, AhpC, GroES (DVU1977), and GroEL (DVU1976) and also several periplasmic ABC transporters.
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Qazi S, Middleton B, Muharram SH, Cockayne A, Hill P, O'Shea P, Chhabra SR, Cámara M, Williams P. N-acylhomoserine lactones antagonize virulence gene expression and quorum sensing in Staphylococcus aureus. Infect Immun 2006; 74:910-9. [PMID: 16428734 PMCID: PMC1360299 DOI: 10.1128/iai.74.2.910-919.2006] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Many gram-negative bacteria employ N-acylhomoserine lactone (AHL)-mediated quorum sensing to control virulence. To determine whether gram-positive bacteria such as Staphylococcus aureus respond to AHLs, we used a growth-dependent lux reporter fusion. Exposure of S. aureus to different AHLs revealed that 3-oxo-substituted AHLs with C10 to C14 acyl chains inhibited light output and growth in a concentration-dependent manner, while short-chain AHLs had no effect. N-(3-Oxododecanoyl)-L-homoserine lactone (3-oxo-C12-HSL) inhibited the production of exotoxins and cell wall fibronectin-binding proteins but enhanced protein A expression. Since these processes are reciprocally regulated via the S. aureus agr quorum-sensing system, which in turn, is regulated via sar, we examined the effect of AHLs on sarA and agr. At sub-growth-inhibitory concentrations of 3-oxo-C12-HSL, both sarA expression and agr expression were inhibited, indicating that the action of 3-oxo-C12-HSL is mediated at least in part through antagonism of quorum sensing in S. aureus. Spent culture supernatants from Pseudomonas aeruginosa, which produces both 3-oxo-C12-HSL and N-butanoyl-homoserine lactone (C4-HSL), also inhibited agr expression, although C4-HSL itself was inactive in this assay. Since quorum sensing in S. aureus depends on the activities of membrane-associated proteins, such as AgrB, AgrC, and AgrD, we investigated whether AHLs perturbed S. aureus membrane functionality by determining their influence on the membrane dipole potential. From the binding curves obtained, a dissociation constant of 7 muM was obtained for 3-oxo-C12-HSL, indicating the presence of a specific saturable receptor, whereas no binding was observed for C4-HSL. These data demonstrate that long-chain 3-oxo-substituted AHLs, such as 3-oxo-C12-HSL, are capable of interacting with the S. aureus cytoplasmic membrane in a saturable, specific manner and at sub-growth-inhibitory concentrations, down-regulating exotoxin production and both sarA and agr expression.
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Pritchard DI, Todd I, Brown A, Bycroft BW, Chhabra SR, Williams P, Wood P. Alleviation of insulitis and moderation of diabetes in NOD mice following treatment with a synthetic Pseudomonas aeruginosa signal molecule, N-(3-oxododecanoyl)-L-homoserine lactone. Acta Diabetol 2005; 42:119-22. [PMID: 16258734 DOI: 10.1007/s00592-005-0190-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/17/2004] [Accepted: 07/28/2005] [Indexed: 11/30/2022]
Abstract
Quorum sensing signal molecules (QSSMs) from the bacterium Pseudomonas aeruginosa control bacterial population density and the expression of virulence determinants. Coincidentally, and possibly to allow this pathogen to gain a foothold in the human body, certain signal molecules also downregulate immunological responses in an apparently T-helper 1-selective manner, which would suggest their application as therapeutics to some autoimmune diseases. In the present paper, experiments are described that indicate that one particular signal molecule, a synthetic N-(3-oxododecanoyl)-L-homoserine lactone, can be used to alleviate insulitis and diabetes in non-obese diabetic (NOD) mice, suggesting that bacterial signal molecules may represent a novel source of immune modulatory compounds for the treatment of type 1 diabetes, which afflicts more than 2 million individuals in Europe and North America.
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Uroz S, Chhabra SR, Cámara M, Williams P, Oger P, Dessaux Y. N-Acylhomoserine lactone quorum-sensing molecules are modified and degraded by Rhodococcus erythropolis W2 by both amidolytic and novel oxidoreductase activities. Microbiology (Reading) 2005; 151:3313-3322. [PMID: 16207914 DOI: 10.1099/mic.0.27961-0] [Citation(s) in RCA: 151] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The Rhodococcus erythropolis strain W2 has been shown previously to degrade the N-acylhomoserine lactone (AHL) quorum-sensing signal molecule N-hexanoyl-l-homoserine lactone, produced by other bacteria. Data presented here indicate that this Gram-positive bacterium is also capable of using various AHLs as the sole carbon and energy source. The enzymic activities responsible for AHL inactivation were investigated in R. erythropolis cell extracts and in whole cells. R. erythropolis cells rapidly degraded AHLs with 3-oxo substituents but exhibited relatively poor activity against the corresponding unsubstituted AHLs. Investigation of the mechanism(s) by which R. erythropolis cells degraded AHLs revealed that 3-oxo compounds with N-acyl side chains ranging from C8 to C14 were initially converted to their corresponding 3-hydroxy derivatives. This oxidoreductase activity was not specific to 3-oxo-AHLs but also allowed the reduction of compounds such as N-(3-oxo-6-phenylhexanoyl)homoserine lactone (which contains an aromatic acyl chain substituent) and 3-oxododecanamide (which lacks the homoserine lactone ring). It also reduced both the d- and l-isomers of n-(3-oxododecanoyl)-l-homoserine lactone. A second AHL-degrading activity was observed when R. erythropolis cell extracts were incubated with N-(3-oxodecanoyl)-l-homoserine lactone (3O,C10-HSL). This activity was both temperature- and pH-dependent and was characterized as an amidolytic activity by HPLC analysis of the reaction mixture treated with dansyl chloride. This revealed the accumulation of dansylated homoserine lactone, indicating that the 3O,C10-HSL amide had been cleaved to yield homoserine lactone. R. erythropolis is therefore capable of modifying and degrading AHL signal molecules through both oxidoreductase and amidolytic activities.
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Kellam B, Ward PA, Abdul Rahim AS, Chhabra SR. Nα-Dmc protected amino acid aglycones: versatile hydrogenolysis stable acceptors for O-glycosylation. Tetrahedron Lett 2005. [DOI: 10.1016/j.tetlet.2005.01.055] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Li L, Hooi D, Chhabra SR, Pritchard D, Shaw PE. Erratum: Bacterial N-acylhomoserine lactone-induced apoptosis in breast carcinoma cells correlated with downmodulation of STAT3. Oncogene 2004. [DOI: 10.1038/sj.onc.1208361] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Hooi DSW, Bycroft BW, Chhabra SR, Williams P, Pritchard DI. Differential immune modulatory activity of Pseudomonas aeruginosa quorum-sensing signal molecules. Infect Immun 2004; 72:6463-70. [PMID: 15501777 PMCID: PMC522992 DOI: 10.1128/iai.72.11.6463-6470.2004] [Citation(s) in RCA: 136] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Pseudomonas aeruginosa releases a spectrum of well-regulated virulence factors, controlled by intercellular communication (quorum sensing) and mediated through the production of small diffusible quorum-sensing signal molecules (QSSM). We hypothesize that QSSM may in fact serve a dual purpose, also allowing bacterial colonization via their intrinsic immune-modulatory capacity. One class of signal molecule, the N-acylhomoserine lactones, has pleiotropic effects on eukaryotic cells, particularly those involved in host immunity. In the present study, we have determined the comparative effects of two chemically distinct and endobronchially detectable QSSM, N-(3-oxododecanoyl)-L-homoserine lactone (3-oxo-C12-HSL) and 2-heptyl-3-hydroxy-4 (1H)-quinolone or the Pseudomonas quinolone signal (PQS), on human leukocytes exposed to a series of stimuli designed to detect differential immunological activity in vitro. 3-Oxo-C12-HSL and PQS displayed differential effects on the release of interleukin-2 (IL-2) when human T cells were activated via the T-cell receptor and CD28 (a costimulatory molecule). 3-Oxo-C12-HSL inhibited cell proliferation and IL-2 release; PQS inhibited cell proliferation without affecting IL-2 release. Both molecules inhibited cell proliferation and the release of IL-2 following mitogen stimulation. Furthermore, in the presence of Escherichia coli lipopolysaccharide, 3-oxo-C12-HSL inhibited tumor necrosis factor alpha release from human monocytes, as reported previously (K. Tateda et al., Infect. Immun. 64:37-43, 1996), whereas PQS did not inhibit in this assay. These data highlight the presence of two differentially active immune modulatory QSSM from P. aeruginosa, which are detectable endobronchially and may be active at the host/pathogen interface during infection with P. aeruginosa, should the bronchial airway lymphoid tissues prove to be accessible to QSSM.
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Chhabra SR, Philipp B, Eberl L, Givskov M, Williams P, Cámara M. Extracellular Communication in Bacteria. Top Curr Chem (Cham) 2004. [DOI: 10.1007/b98319] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
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