1
|
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: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [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. QZNs inhibit PQS-dependent quorum sensing and reduce biofilm formation in Pseudomonas aeruginosa A subset of QZNs is bactericidal for planktonic Staphylococcus aureus and severely damages biofilms In mixed species biofilms, P. aeruginosa protects S. aureus from tobramycin Tobramycin plus QZN eradicates mixed P. aeruginosa and S. aureus biofilms
Collapse
Affiliation(s)
- Ewan J Murray
- National Biofilms Innovation Centre, Biodiscovery Institute and School of Life Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK
| | - Jean-Frédéric Dubern
- National Biofilms Innovation Centre, Biodiscovery Institute and School of Life Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK
| | - Weng C Chan
- School of Pharmacy, Biodiscovery Institute, University of Nottingham, University Park, Nottingham NG7 2RD, UK
| | - Siri Ram Chhabra
- National Biofilms Innovation Centre, Biodiscovery Institute and School of Life Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK
| | - Paul Williams
- National Biofilms Innovation Centre, Biodiscovery Institute and School of Life Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK.
| |
Collapse
|
2
|
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] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
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.
Collapse
Affiliation(s)
- Ewan J Murray
- School of Life Sciences, Centre for Biomolecular Sciences, University of Nottingham , Nottingham, NG7 2RD, U.K
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
3
|
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] [What about the content of this article? (0)] [Affiliation(s)] [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.
Collapse
Affiliation(s)
- Sven Thierbach
- Institute of Molecular Microbiology and Biotechnology, University of Münster, Corrensstrasse 3, 48149 Münster, Germany
| | - Nguyen Bui
- Department of Biophysics, School of Medicine, Saarland University, Clinical Center, Building 76, 66421 Homburg, Germany
| | - Josef Zapp
- Pharmaceutical Biology, Saarland University, Campus, Building C2, 66123 Saarbrücken, Germany
| | - Siri Ram Chhabra
- School of Life Sciences, Centre for Biomolecular Sciences, University of Nottingham, University Park, Nottingham, NG7 2RD, UK
| | - Reinhard Kappl
- Department of Biophysics, School of Medicine, Saarland University, Clinical Center, Building 76, 66421 Homburg, Germany
| | - Susanne Fetzner
- Institute of Molecular Microbiology and Biotechnology, University of Münster, Corrensstrasse 3, 48149 Münster, Germany.
| |
Collapse
|
4
|
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: 151] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [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.
Collapse
Affiliation(s)
- Aravindan Ilangovan
- Centre for Biomolecular Sciences, University of Nottingham, University Park, Nottingham, United Kingdom
- School of Molecular Medical Sciences, University of Nottingham, University Park, Nottingham, United Kingdom
- School of Pharmacy, University of Nottingham, University Park, Nottingham, United Kingdom
| | - Matthew Fletcher
- Centre for Biomolecular Sciences, University of Nottingham, University Park, Nottingham, United Kingdom
- School of Molecular Medical Sciences, University of Nottingham, University Park, Nottingham, United Kingdom
| | - Giordano Rampioni
- Centre for Biomolecular Sciences, University of Nottingham, University Park, Nottingham, United Kingdom
- School of Molecular Medical Sciences, University of Nottingham, University Park, Nottingham, United Kingdom
| | - Christian Pustelny
- Centre for Biomolecular Sciences, University of Nottingham, University Park, Nottingham, United Kingdom
- School of Molecular Medical Sciences, University of Nottingham, University Park, Nottingham, United Kingdom
| | - Kendra Rumbaugh
- Department of Surgery, University of Texas, Lubbock, Texas, United States of America
| | - Stephan Heeb
- Centre for Biomolecular Sciences, University of Nottingham, University Park, Nottingham, United Kingdom
- School of Molecular Medical Sciences, University of Nottingham, University Park, Nottingham, United Kingdom
| | - Miguel Cámara
- Centre for Biomolecular Sciences, University of Nottingham, University Park, Nottingham, United Kingdom
- School of Molecular Medical Sciences, University of Nottingham, University Park, Nottingham, United Kingdom
| | - Alex Truman
- Centre for Biomolecular Sciences, University of Nottingham, University Park, Nottingham, United Kingdom
- School of Molecular Medical Sciences, University of Nottingham, University Park, Nottingham, United Kingdom
| | - Siri Ram Chhabra
- Centre for Biomolecular Sciences, University of Nottingham, University Park, Nottingham, United Kingdom
- School of Molecular Medical Sciences, University of Nottingham, University Park, Nottingham, United Kingdom
| | - Jonas Emsley
- Centre for Biomolecular Sciences, University of Nottingham, University Park, Nottingham, United Kingdom
- School of Pharmacy, University of Nottingham, University Park, Nottingham, United Kingdom
| | - Paul Williams
- Centre for Biomolecular Sciences, University of Nottingham, University Park, Nottingham, United Kingdom
- School of Molecular Medical Sciences, University of Nottingham, University Park, Nottingham, United Kingdom
- * E-mail:
| |
Collapse
|
5
|
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] [What about the content of this article? (0)] [Affiliation(s)] [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.
Collapse
Affiliation(s)
- Heiko Niewerth
- Institute of Molecular Microbiology and Biotechnology, University of Münster, 48149 Münster, Germany
| | | | | | | | | |
Collapse
|
6
|
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.
Collapse
Affiliation(s)
- Stephan Heeb
- School of Molecular Medical Sciences, Centre for Biomolecular Sciences, University Park, University of Nottingham, Nottingham, UK
| | | | | | | | | | | |
Collapse
|
7
|
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] [What about the content of this article? (0)] [Affiliation(s)] [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.
Collapse
Affiliation(s)
- Gopal P Jadhav
- School of Pharmacy, University of Nottingham, University Park, Nottingham, NG7 2RD, U.K
| | | | | | | | | | | | | | | | | |
Collapse
|
8
|
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] [What about the content of this article? (0)] [Affiliation(s)] [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.
Collapse
Affiliation(s)
- Kok-Gan Chan
- Division of Genetics and Molecular Biology, Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia
- School of Molecular Medical Sciences, Centre for Biomolecular Sciences, University of Nottingham, Nottingham, NG7 2RD, UK
- Institute of Biological Sciences (Division of Genetics and Molecular Biology), Faculty of Science, University of Malaya, 50603 Malaysia
| | - Steve Atkinson
- School of Molecular Medical Sciences, Centre for Biomolecular Sciences, University of Nottingham, Nottingham, NG7 2RD, UK
| | - Kalai Mathee
- Department of Molecular Microbiology and Infectious Diseases, Herbert Wertheim College of Medicine, Florida International University, Miami, FL 33199, USA
| | - Choon-Kook Sam
- Natural Sciences and Science Education AG, National Institute of Education, Nanyang Technological University, 1 Nanyang Walk, Singapore 637616, Singapore
| | - Siri Ram Chhabra
- School of Molecular Medical Sciences, Centre for Biomolecular Sciences, University of Nottingham, Nottingham, NG7 2RD, UK
| | - Miguel Cámara
- School of Molecular Medical Sciences, Centre for Biomolecular Sciences, University of Nottingham, Nottingham, NG7 2RD, UK
| | - Chong-Lek Koh
- Natural Sciences and Science Education AG, National Institute of Education, Nanyang Technological University, 1 Nanyang Walk, Singapore 637616, Singapore
| | - Paul Williams
- School of Molecular Medical Sciences, Centre for Biomolecular Sciences, University of Nottingham, Nottingham, NG7 2RD, UK
| |
Collapse
|
9
|
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: 143] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [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.
Collapse
Affiliation(s)
- Catharine A Ortori
- Centre for Analytical Bioscience, School of Pharmacy, University of Nottingham, Nottingham, NG7 2RD, UK
| | | | | | | | | | | | | |
Collapse
|
10
|
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] [What about the content of this article? (0)] [Affiliation(s)] [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.
Collapse
Affiliation(s)
- Christian Pustelny
- School of Molecular Medical Sciences, Centre for Biomolecular Sciences, University of Nottingham, Nottingham NG7 2RD, UK
| | | | | | | | | | | | | | | |
Collapse
|
11
|
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: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [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.
Collapse
Affiliation(s)
- Margaret Cooley
- Menzies Research Institute and School of Medicine, University of Tasmania, Hobart, TAS 7001, Australia
| | | | | |
Collapse
|
12
|
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: 340] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [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.
Collapse
Affiliation(s)
- Stephen P Diggle
- Institute of Infection, Immunity & Inflammation, Centre for Biomolecular Sciences, University Park, University of Nottingham, Nottingham NG7 2RD, United Kingdom.
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
13
|
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] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
14
|
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] [What about the content of this article? (0)] [Affiliation(s)] [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.
Collapse
Affiliation(s)
- Adam J Ritchie
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | | | | | | | | | | |
Collapse
|
15
|
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] [What about the content of this article? (0)] [Affiliation(s)] [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.
Collapse
Affiliation(s)
- Stephen P Diggle
- Institute of Infection, Immunity & Inflammation, Centre for Biomolecular Sciences, University Park, University of Nottingham, UK.
| | | | | | | | | | | | | | | | | |
Collapse
|
16
|
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] [What about the content of this article? (0)] [Affiliation(s)] [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.
Collapse
Affiliation(s)
- Stéphane Uroz
- CNRS, ISV, Bâtiment 23, Avenue de la Terrasse, 91198 Gif-sur-Yvette, France
| | | | | | | | | | | |
Collapse
|
17
|
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] [What about the content of this article? (0)] [Affiliation(s)] [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.
Collapse
Affiliation(s)
- Catharine A Ortori
- Centre for Analytical Bioscience, School of Pharmacy, University of Nottingham, Nottingham, NG7 2RD, UK
| | | | | | | | | | | |
Collapse
|
18
|
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] [What about the content of this article? (0)] [Affiliation(s)] [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.
Collapse
Affiliation(s)
- S R Chhabra
- Biosystems Research Department, Mailstop 9292, Sandia National Laboratory, 7011 East Ave., Livermore, CA 94550, USA
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
19
|
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] [What about the content of this article? (0)] [Affiliation(s)] [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.
Collapse
Affiliation(s)
- Saara Qazi
- Institute of Infection, Immunity and Inflammation, Centre for Biomolecular Sciences, University of Nottingham, Nottingham NG7 2RD, United Kingdom
| | | | | | | | | | | | | | | | | |
Collapse
|
20
|
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] [What about the content of this article? (0)] [Affiliation(s)] [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.
Collapse
Affiliation(s)
- D I Pritchard
- School of Pharmacy, University of Nottingham, University Park, Nottingham NG7 2RD, UK.
| | | | | | | | | | | | | |
Collapse
|
21
|
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] [What about the content of this article? (0)] [Affiliation(s)] [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.
Collapse
Affiliation(s)
- Stéphane Uroz
- Interactions Plantes et Micro-organismes de la Rhizosphère, Institut des Sciences du Végétal, CNRS, Bâtiment 23, Avenue de la Terrasse, 91198 Gif-sur-Yvette CEDEX, France
| | - Siri Ram Chhabra
- Institute of Infection, Immunity and Inflammation, Centre for Biomolecular Sciences, University of Nottingham, Nottingham NG7 2RD, UK
| | - Miguel Cámara
- Institute of Infection, Immunity and Inflammation, Centre for Biomolecular Sciences, University of Nottingham, Nottingham NG7 2RD, UK
| | - Paul Williams
- Institute of Infection, Immunity and Inflammation, Centre for Biomolecular Sciences, University of Nottingham, Nottingham NG7 2RD, UK
| | - Phil Oger
- Laboratoire des Sciences de la Terre, École Normale Supérieure de Lyon, 43 Allée D'Italie, 69364 Lyon CEDEX 07, France
| | - Yves Dessaux
- Interactions Plantes et Micro-organismes de la Rhizosphère, Institut des Sciences du Végétal, CNRS, Bâtiment 23, Avenue de la Terrasse, 91198 Gif-sur-Yvette CEDEX, France
| |
Collapse
|
22
|
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] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
23
|
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] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
24
|
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] [What about the content of this article? (0)] [Affiliation(s)] [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.
Collapse
Affiliation(s)
- Doreen S W Hooi
- School of Pharmacy, University of Nottingham, University Park, NG7 2RD, UK
| | | | | | | | | |
Collapse
|
25
|
|
26
|
Li L, Hooi D, Chhabra SR, Pritchard D, Shaw PE. Bacterial N-acylhomoserine lactone-induced apoptosis in breast carcinoma cells correlated with down-modulation of STAT3. Oncogene 2004; 23:4894-902. [PMID: 15064716 DOI: 10.1038/sj.onc.1207612] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Cell growth is promoted by mitogens and survival factors, which activate intracellular signalling pathways to control cell cycle progression and cellular integrity. Proliferation signals are transmitted through Ras and Rho family small G-proteins coupled to mitogen-activated protein kinase (MAPK) cascades, while survival signals are propagated by lipid-dependent kinases such as phosphatidylinositide 3-kinases (PI3Ks) and protein kinase B (Akt/PKB). Recently, signal transducer and activator of transcription (STAT) proteins were identified as positive regulators of proliferation in a variety of cell types. Persistent activation of these pathways is associated with tumour cell growth, whereas their inhibition can halt proliferation and precipitate apoptotic cell death. The human pathogen Pseudomonas aeruginosa uses quorum-sensing signal molecules (QSSMs) to regulate virulence gene expression. QSSMs also suppress host immune responses although the mechanism of suppression is unknown. Here, we demonstrate that the QSSM N-(3-oxododecanoyl)-L-homoserine lactone (OdDHL) from P. aeruginosa blocks proliferation and induces apoptosis in human BC cell lines. Analyses of signalling events reveal that OdDHL has little or no effect on MAPK cascades, partially inhibits the Akt/PKB pathway and ablates STAT3 activity. Pharmacological inhibition of each pathway independently indicates that STAT3 activity is critical for BC cell proliferation and survival, while a constitutively active STAT3 confers resistance to OdDHL. These results support the notion of OdDHL as a bioactive molecule in eukaryotic systems and a paradigm for a novel class of antiproliferative compounds.
Collapse
Affiliation(s)
- Li Li
- School of Biomedical Sciences, University of Nottingham, Queen's Medical Centre, Nottingham NG7 2UH, UK
| | | | | | | | | |
Collapse
|
27
|
Sleeman MC, Smith P, Kellam B, Chhabra SR, Bycroft BW, Schofield CJ. Biosynthesis of Carbapenem Antibiotics: New Carbapenam Substrates for Carbapenem Synthase (CarC). Chembiochem 2004; 5:879-82. [PMID: 15174175 DOI: 10.1002/cbic.200300908] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Mark C Sleeman
- Dyson Perrins Laboratory, University of Oxford, South Parks Road, Oxford, OX1 3QY, UK
| | | | | | | | | | | |
Collapse
|
28
|
Middleton RJ, Mellor SL, Chhabra SR, Bycroft BW, Chan WC. Expedient synthesis of a novel class of pseudoaromatic amino acids: tetrahydroindazol-3-yl- and tetrahydrobenzisoxazol-3-ylalanine derivatives. Tetrahedron Lett 2004. [DOI: 10.1016/j.tetlet.2003.11.133] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
|
29
|
Abstract
The selectins are a family of cell-adhesion proteins that mediate the early stages of leukocyte recruitment from the blood stream to sites of tissue damage through recognition of the carbohydrate epitope sialyl Lewis(x) (sLe(x)). Current development of small molecule based inhibitors of this process and their clinical potential to address numerous acute and chronic diseases are explored.
Collapse
Affiliation(s)
- Siri Ram Chhabra
- School of Pharmacy, University of Nottingham, University Park, Nottingham NG7 2RD, UK
| | | | | |
Collapse
|
30
|
Diggle SP, Winzer K, Chhabra SR, Worrall KE, Cámara M, Williams P. The Pseudomonas aeruginosa quinolone signal molecule overcomes the cell density-dependency of the quorum sensing hierarchy, regulates rhl-dependent genes at the onset of stationary phase and can be produced in the absence of LasR. Mol Microbiol 2003; 50:29-43. [PMID: 14507361 DOI: 10.1046/j.1365-2958.2003.03672.x] [Citation(s) in RCA: 421] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
In Pseudomonas aeruginosa, diverse exoproduct virulence determinants are regulated via N-acylhomoserine lactone-dependent quorum sensing. Here we show that 2-heptyl-3-hydroxy-4(1H)-quinolone (PQS) is also an integral component of the quorum sensing circuitry and is required for the production of rhl-dependent exoproducts at the onset of stationary phase. Analysis of spent P. aeruginosa culture supernatants revealed that PQS is produced at the end of exponential phase in the parent strain and in the late stationary phase of a lasR mutant. Mutants defective in both PQS production (pqsR-) and response (pqsE-) produced substantially reduced levels of exoproducts but retained wild-type N-butanoyl homoserine lactone (C4-HSL) levels. In the wild type, provision of exogenous PQS at the time of inoculation significantly increased PA-IL lectin, pyocyanin and elastase production during early stationary phase and promoted biofilm formation. Exogenous PQS but not PQS derivatives lacking the 3-hydroxy group overcame the cell density but not growth phase-dependent production of exoproducts. PQS also overcame the transcriptional and post-transcriptional repression of lecA (which codes for the PA-IL lectin) mediated via the negative regulators MvaT and RsmA respectively. Increased expression of lecA in the presence of exogenous PQS can be explained partially by increases in RhlR, RpoS and C4-HSL levels. A refined model for quorum sensing in P. aeruginosa is presented.
Collapse
Affiliation(s)
- Stephen P Diggle
- Institute of Infection, Immunity and Inflammation, University of Nottingham, Queen's Medical Centre, Nottingham NG7 2RD, UK
| | | | | | | | | | | |
Collapse
|
31
|
Chhabra SR, Harty C, Hooi DSW, Daykin M, Williams P, Telford G, Pritchard DI, Bycroft BW. Synthetic analogues of the bacterial signal (quorum sensing) molecule N-(3-oxododecanoyl)-L-homoserine lactone as immune modulators. J Med Chem 2003; 46:97-104. [PMID: 12502363 DOI: 10.1021/jm020909n] [Citation(s) in RCA: 205] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Comparative immune modulatory activity for a range of synthetic analogues of a Pseudomonas aeruginosa signal molecule, N-(3-oxododecanoyl)-l-homoserine lactone (3O, C(12)-HSL), is described. Twenty-four single or combination systematic alterations of the structural components of 3O, C(12)-HSL were introduced as described. Given the already defined immunological profile of the parent compound, 3O, C(12)-HSL, these compounds were assayed for their ability to inhibit murine and human leucocyte proliferation and TNF-alpha secretion by lipopolysaccharide (LPS) stimulated human leucocytes in order to provide an initial structure-activity profile. From IC(50) values obtained with a murine splenocyte proliferation assay, it is apparent that acylated l-homoserine lactones with an 11-13 C side chain containing either a 3-oxo or a 3-hydroxy group are optimal structures for immune suppressive activity. These derivatives of 3O, C(12)-HSL with monounsaturation and/or a terminal nonpolar substituent on the side chain were also potent immune suppressive agents. However, structures lacking the homoserine lactone ring, structures lacking the l-configuration at the chiral center, and those with polar substituents were essentially devoid of activity. The ability of compounds selected from the optimal activity range to modulate mitogen-driven human peripheral blood mononuclear cell proliferation and LPS-induced TNF-alpha secretion indicates the suitability of these compounds for further investigation in relation to their molecular mechanisms of action in TNF-alpha driven immunological diseases, particularly autoimmune diseases such as psoriasis, rheumatoid arthritis, and type 1 (autoimmune) diabetes.
Collapse
Affiliation(s)
- Siri Ram Chhabra
- School of Pharmaceutical Sciences, University of Nottingham, University Park, Nottingham, NG7 2RD, UK
| | | | | | | | | | | | | | | |
Collapse
|
32
|
Burton CL, Chhabra SR, Swift S, Baldwin TJ, Withers H, Hill SJ, Williams P. The growth response of Escherichia coli to neurotransmitters and related catecholamine drugs requires a functional enterobactin biosynthesis and uptake system. Infect Immun 2002; 70:5913-23. [PMID: 12379665 PMCID: PMC130287 DOI: 10.1128/iai.70.11.5913-5923.2002] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2002] [Revised: 05/15/2002] [Accepted: 07/24/2002] [Indexed: 11/20/2022] Open
Abstract
The neurotransmitter norepinephrine (NE) stimulates the growth of low inocula of Escherichia coli in a minimal medium (SAPI) supplemented with serum (SAPI+serum) and induces the production of an "autoinducer" (AI) which, in turn, promotes E. coli growth in the absence of NE. Given the importance of NE, epinephrine, and their corresponding adrenergic agonists and antagonists in clinical medicine, we sought to investigate the molecular basis for these observations. Using a variety of NE precursors, metabolites, and therapeutic agents, we demonstrated that their ability to stimulate E. coli growth in SAPI+serum is dependent on the presence of a catechol (1,2-dihydroxybenzene) moiety with maximal activity requiring a two-carbon substituent incorporating a terminal primary amine. Serum contains the iron-binding glycoprotein, transferrin, and when SAPI+serum was supplemented with sufficient Fe(3+) to saturate transferrin, growth inhibition was relieved. Other metal cations, including Mg(2+), Ca(2+), and Zn(2+), had no effect. These data suggested that the stimulation of E. coli growth by NE in SAPI+serum may involve the catecholate siderophore, enterobactin, a cyclic triester of 2,3-dihydroxybenzoylserine. Consistent with this hypothesis, E. coli strains with mutations in ferrienterobactin transport (fepA or tonB) or enterobactin biosynthesis (entA) did not respond to NE. Furthermore, NE induced expression of the ferrienterobactin receptor, FepA, during growth in SAPI+serum. The enterobactin degradation product, 2,3-dihydroxybenzoylserine (DBS) was as effective as NE in stimulating the growth of E. coli and mutations in fepA or tonB abolished the DBS-dependent growth stimulation. In contrast to NE, however, DBS stimulated the growth of the entA mutant. Moreover, after growth in an iron-limited M9 medium in the absence of NE, ethyl acetate extracts of the E. coli entA(+) parent but not of the entA mutant contained AI, i.e., stimulated the growth of E. coli in SAPI+serum. Taken together, these data show that when low numbers of E. coli are inoculated into SAPI+serum, NE, DBS, and related catecholamines induce the enterobactin iron uptake system. This, in turn, facilitates iron sequestration from transferrin and indicates that the AI present in NE-conditioned SAPI+serum medium is enterobactin and its DBS breakdown products.
Collapse
Affiliation(s)
- Claire L Burton
- Institute of Infections and Immunity. Institute of Cell Signalling, Queens Medical Centre, University of Nottingham, Nottingham NG7 2UH, United Kingdom
| | | | | | | | | | | | | |
Collapse
|
33
|
Yates EA, Philipp B, Buckley C, Atkinson S, Chhabra SR, Sockett RE, Goldner M, Dessaux Y, Cámara M, Smith H, Williams P. N-acylhomoserine lactones undergo lactonolysis in a pH-, temperature-, and acyl chain length-dependent manner during growth of Yersinia pseudotuberculosis and Pseudomonas aeruginosa. Infect Immun 2002; 70:5635-46. [PMID: 12228292 PMCID: PMC128322 DOI: 10.1128/iai.70.10.5635-5646.2002] [Citation(s) in RCA: 421] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In gram-negative bacterial pathogens, such as Pseudomonas aeruginosa and Yersinia pseudotuberculosis, cell-to-cell communication via the N-acylhomoserine lactone (AHL) signal molecules is involved in the cell population density-dependent control of genes associated with virulence. This phenomenon, termed quorum sensing, relies upon the accumulation of AHLs to a threshold concentration at which target structural genes are activated. By using biosensors capable of detecting a range of AHLs we observed that, in cultures of Y. pseudotuberculosis and P. aeruginosa, AHLs accumulate during the exponential phase but largely disappear during the stationary phase. When added to late-stationary-phase, cell-free culture supernatants of the respective pathogen, the major P. aeruginosa [N-butanoylhomoserine lactone (C4-HSL) and N-(3-oxododecanoyl)homoserine lactone (3-oxo-C12-HSL)] and Y. pseudotuberculosis [N-(3-oxohexanoyl)homoserine lactone (3-oxo-C6-HSL) and N-hexanoylhomoserine lactone (C6-HSL)] AHLs were inactivated. Short-acyl-chain compounds (e.g., C4-HSL) were turned over more extensively than long-chain molecules (e.g., 3-oxo-C12-HSL). Little AHL inactivation occurred with cell extracts, and no evidence for inactivation by specific enzymes was apparent. This AHL turnover was discovered to be due to pH-dependent lactonolysis. By acidifying the growth media to pH 2.0, lactonolysis could be reversed. By using carbon-13 nuclear magnetic resonance spectroscopy, we found that the ring opening of homoserine lactone (HSL), N-propionyl HSL (C3-HSL), and C4-HSL increased as pH increased but diminished as the N-acyl chain was lengthened. At low pH levels, the lactone rings closed but not via a simple reversal of the ring opening reaction mechanism. Ring opening of C4-HSL, C6-HSL, 3-oxo-C6-HSL, and N-octanoylhomoserine lactone (C8-HSL), as determined by the reduction of pH in aqueous solutions with time, was also less rapid for AHLs with more electron-donating longer side chains. Raising the temperature from 22 to 37 degrees C increased the rate of ring opening. Taken together, these data show that (i) to be functional under physiological conditions in mammalian tissue fluids, AHLs require an N-acyl side chain of at least four carbons in length and (ii) that the longer the acyl side chain the more stable the AHL signal molecule.
Collapse
Affiliation(s)
- Edwin A Yates
- School of Biosciences, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
34
|
Abstract
Anomalous amino acids not only play central roles as mimics of natural amino acids but also offer opportunities as unique building blocks for combinatorial chemistry. This paper describes the chiral syntheses and solid-phase applications of a versatile atypical amino acid, 4-azalysine (2,6-diamino-4-azahexanoic acid) 1. The syntheses of differentially protected 4-azalysine derivatives 28a-e have been developed by two efficient and inexpensive routes that start either from Garner's aldehyde 16 or the chiron (S)-N(alpha)-Cbz-2,3-diaminopropionic acid 23. Both approaches employ the convergent modular concept and exploit reductive amination of aldehydes with amines as the key step for the fusion of the two segments. In the first route, the overall process inverts the chirality of the starting material, L-serine, and thus provides an excellent route to the unnatural D-isomers. The alternative route starting from L-asparagine provides a shorter and high-yielding route to orthogonally protected 4-azalysine derivatives. The corresponding N(2)-Fmoc-4-azalysines 31a-e, readily derived from the key intermediate 27, are compatible with the Fmoc-based solid-phase peptide synthesis (SPPS) and solid-phase organic chemistry (SPOC) protocols. Furthermore, the utility and versatility of another key structure, tris-Boc-4-azalysine 2 in the engineering of novel high-loading dendrimeric polystyrene resins 33 and 36, have been demonstrated. Following derivatization with the Rink amide linker 34, the stability and robustness of these resin-bound dendrimers 35 and 37 in the synthesis of small molecules using a range of reaction conditions (e.g., Mitsunobu and Suzuki reactions) have been effectively illustrated.
Collapse
Affiliation(s)
- Siri Ram Chhabra
- School of Pharmaceutical Sciences, University of Nottingham, University Park, NG7 2RD, United Kingdom
| | | | | |
Collapse
|
35
|
Wisniewski-Dyé F, Jones J, Chhabra SR, Downie JA. raiIR genes are part of a quorum-sensing network controlled by cinI and cinR in Rhizobium leguminosarum. J Bacteriol 2002; 184:1597-606. [PMID: 11872711 PMCID: PMC134902 DOI: 10.1128/jb.184.6.1597-1606.2002] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Analysis of N-acyl-L-homoserine lactones (AHLs) produced by Rhizobium leguminosarum bv. viciae indicated that there may be a network of quorum-sensing regulatory systems producing multiple AHLs in this species. Using a strain lacking a symbiosis plasmid, which carries some of the quorum-sensing genes, we isolated mutations in two genes (raiI and raiR) that are required for production of AHLs. The raiIR genes are located adjacent to dad genes (involved in D-alanine catabolism) on a large indigenous plasmid. RaiR is predicted to be a typical LuxR-type quorum-sensing regulator and is required for raiI expression. The raiR gene was expressed at a low level, possibly from a constitutive promoter, and its expression was increased under the influence of the upstream raiI promoter. Using gene fusions and analysis of AHLs produced, we showed that expression of raiI is strongly reduced in strains carrying mutations in cinI or cinR, genes which determine a higher-level quorum-sensing system that is required for normal expression of raiIR. The product of CinI, N-(3-hydroxy-7-cis tetradecenoyl) homoserine lactone, can induce raiR-dependent raiI expression, although higher levels of expression are induced by other AHLs. Expression of raiI in a strain of Agrobacterium that makes no AHLs resulted in the identification of N-(3-hydroxyoctanoyl)-L-homoserine lactone (3OH,C(8)-HSL) as the major product of RaiI, although other AHLs that comigrate with N-hexanoyl-, N-heptanoyl-, and N-octanoyl-homoserine lactones were also made at low levels. The raiI gene was strongly induced by 3OH,C(8)-HSL (the product of RaiI) but could also be induced by other AHLs, suggesting that the raiI promoter can be activated by other quorum-sensing systems within a network of regulation which also involves AHLs determined by genes on the symbiotic plasmid. Thus, the raiIR and cinIR genes are part of a complex regulatory network that influences AHL biosynthesis in R. leguminosarum.
Collapse
|
36
|
Parker KN, Chhabra SR, Lam D, Callen W, Duffaud GD, Snead MA, Short JM, Mathur EJ, Kelly RM. Galactomannanases Man2 and Man5 from Thermotoga species: growth physiology on galactomannans, gene sequence analysis, and biochemical properties of recombinant enzymes. Biotechnol Bioeng 2001; 75:322-33. [PMID: 11590605 DOI: 10.1002/bit.10020] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The enzymatic hydrolysis of mannan-based hemicelluloses is technologically important for applications ranging from pulp and paper processing to food processing to gas and oil well stimulation. In many cases, thermostability and activity at elevated temperatures can be advantageous. To this end, the genes encoding beta-mannosidase (man2) and beta-mannanase (man5) from the hyperthermophilic bacteria Thermotoga neapolitana 5068 and Thermotoga maritima were isolated, cloned, and expressed in Escherichia coli. The amino acid sequences for the mannosidases from these organisms were 77% identical and corresponded to proteins with an M(r) of approximately 92 kDa. The translated nucleotide sequences for the beta-mannanase genes (man5) encoded polypeptides with an M(r) of 76 kDa that exhibited 84% amino acid sequence identity. The recombinant versions of Man2 and Man5 had similar respective biochemical and biophysical properties, which were also comparable to those determined for the native versions of these enzymes in T. neapolitana. The optimal temperature and pH for the recombinant Man2 and Man5 from both organisms were approximately 90 degrees C and 7.0, respectively. The presence of Man2 and Man5 in these two Thermotoga species indicates that galactomannan is a potential growth substrate. This was supported by the fact that beta-mannanase and beta-mannosidase activities were significantly stimulated when T. neapolitana was grown on guar or carob galactomannan. Maximum cell densities increased by at least tenfold when either guar or carob galactomannan was added to the growth medium. For T. neapolitana grown on guar at 83 degrees C, Man5 was secreted into the culture media, whereas Man2 was intracellular. These localizations were consistent with the presence and lack of signal peptides for Man5 and Man2, respectively. The identification of the galactomannan-degrading enzymes in these Thermotoga species adds to the list of biotechnologically important hemicellulases produced by members of this hyperthermophilic genera.
Collapse
Affiliation(s)
- K N Parker
- Department of Chemical Engineering, North Carolina State University, Box 7905, Raleigh, North Carolina 27695-7905, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
37
|
Gardiner SM, Chhabra SR, Harty C, Williams P, Pritchard DI, Bycroft BW, Bennett T. Haemodynamic effects of the bacterial quorum sensing signal molecule, N-(3-oxododecanoyl)-L-homoserine lactone, in conscious, normal and endotoxaemic rats. Br J Pharmacol 2001; 133:1047-54. [PMID: 11487515 PMCID: PMC1572880 DOI: 10.1038/sj.bjp.0704174] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2000] [Revised: 03/07/2001] [Accepted: 05/17/2001] [Indexed: 11/09/2022] Open
Abstract
N-acylhomoserine lactones (AHLs) are small, diffusible signalling molecules, employed by Gram-negative bacteria to coordinate gene expression with cell population density. Recent in vitro findings indicate that AHLs may function as virulence determinants per se, through modification of cytokine production by eukaryotic cells, and by stimulating the relaxation of blood vessels. In the present study, we assessed the influence of AHLs on cardiovascular function in conscious rats, and draw attention to the ability of the N-(3-oxododecanoyl)-L-homoserine lactone (3-oxo-C12-HSL), a signal molecule produced by P. aeruginosa, to cause marked bradycardia. This bradycardic effect was blocked by atropine and atenolol, and did not occur in vitro. Furthermore, modification of the acyl side chain length resulted in the loss of activity, whereas removal of the homoserine lactone ring, did not. The bradycardic effect of 3-oxo-C12-HSL was also observed in endotoxaemic animals, albeit attenuated. In normal rats, 3-oxo-C12-HSL caused initial mesenteric and hindquarters vasoconstriction, but only slight, and delayed signs of vasodilatation in the renal and mesenteric vascular beds. Furthermore, administration of 3-oxo-C12-HSL (pre-treatment or 2 h post-treatment) together with LPS, did not modify the established regional haemodynamic effects of the LPS, 6 h after the onset of its infusion. Our observations do not provide any clear evidence for an ability of 3-oxo-C12-HSL to modify the haemodynamic responses to LPS infusion. However, they are not inconsistent with the hypothesis that some of the cardiovascular sequelae of bacterial infection may be modulated by an influence of bacterial quorum sensing signalling molecules on the host.
Collapse
Affiliation(s)
- S M Gardiner
- School of Biomedical Sciences, Queen's Medical Centre, University of Nottingham NG7 2UH, UK.
| | | | | | | | | | | | | |
Collapse
|
38
|
|
39
|
Laue BE, Jiang Y, Chhabra SR, Jacob S, Stewart GSAB, Hardman A, Downie JA, O'Gara F, Williams P. The biocontrol strain Pseudomonas fluorescens F113 produces the Rhizobium small bacteriocin, N-(3-hydroxy-7-cis-tetradecenoyl)homoserine lactone, via HdtS, a putative novel N-acylhomoserine lactone synthase. Microbiology (Reading) 2000; 146 ( Pt 10):2469-2480. [PMID: 11021923 DOI: 10.1099/00221287-146-10-2469] [Citation(s) in RCA: 163] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Several different species of Pseudomonas: produce N:-acylhomoserine lactones (AHLs), quorum-sensing signal molecules which are involved in the cell-density-dependent control of secondary metabolite and virulence gene expression. When Pseudomonas fluorescens F113 was cross-streaked against AHL biosensors capable of sensitively detecting either short (C(4)-C(8)) or long (C(10)-C(14)) acyl chain AHLs, no activity was detectable. However, by extracting cell-free stationary-phase culture supernatants with dichloromethane followed by reverse-phase HPLC, three distinct fractions were obtained capable of activating the AHL biosensors. Three AHLs were subsequently characterized using high-resolution MS and chemical synthesis. These were (i) N:-(3-hydroxy-7-cis-tetradecenoyl)homoserine lactone (3OH, C(14:1)-HSL), a molecule previously known as the Rhizobium leguminosarum small bacteriocin as a consequence of its growth inhibitory properties, (ii) N:-decanoylhomoserine lactone (C(10)-HSL) and (iii) N:-hexanoylhomoserine lactone (C(6)-HSL). A gene (hdtS) capable of directing synthesis of all three P. fluorescens AHLs in Escherichia coli was cloned and sequenced. In vitro transcription/translation of hdtS yielded a protein of approximately 33 kDa capable of directing the synthesis of 3OH, C(14:1)-HSL, C(10)-HSL and C(6)-HSL in E. coli. HdtS does not belong to either of the known AHL synthase families (LuxI or LuxM) and is related to the lysophosphatidic acid acyltransferase family. HdtS may therefore constitute a member of a third protein family capable of AHL biosynthesis.
Collapse
Affiliation(s)
- Bridget E Laue
- School of Pharmaceutical Sciences, University of Nottingham, Nottingham NG7 2RD, UK1
| | - Yan Jiang
- School of Pharmaceutical Sciences, University of Nottingham, Nottingham NG7 2RD, UK1
| | - Siri Ram Chhabra
- School of Pharmaceutical Sciences, University of Nottingham, Nottingham NG7 2RD, UK1
| | - Sinead Jacob
- Biomerit Research Centre, Department of Microbiology, National University of Ireland, Cork, Ireland2
| | - Gordon S A B Stewart
- School of Pharmaceutical Sciences, University of Nottingham, Nottingham NG7 2RD, UK1
| | - Andrea Hardman
- School of Pharmaceutical Sciences, University of Nottingham, Nottingham NG7 2RD, UK1
| | | | - Fergal O'Gara
- Biomerit Research Centre, Department of Microbiology, National University of Ireland, Cork, Ireland2
| | - Paul Williams
- School of Pharmaceutical Sciences, University of Nottingham, Nottingham NG7 2RD, UK1
| |
Collapse
|
40
|
Chhabra SR, Khan AN, Bycroft BW. Solid-phase synthesis of polyamines using a Dde-linker: philanthotoxin-4.3.3 via an on-resin Mitsunobu reaction. Tetrahedron Lett 2000. [DOI: 10.1016/s0040-4039(99)02239-x] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
|
41
|
Lawrence RN, Dunn WR, Bycroft B, Camara M, Chhabra SR, Williams P, Wilson VG. The Pseudomonas aeruginosa quorum-sensing signal molecule, N-(3-oxododecanoyl)-L-homoserine lactone, inhibits porcine arterial smooth muscle contraction. Br J Pharmacol 1999; 128:845-8. [PMID: 10556916 PMCID: PMC1571710 DOI: 10.1038/sj.bjp.0702870] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
The Pseudomonas aeruginosa quorum sensing molecule N-(3-oxododecanoyl)-L-homoserine lactone (OdDHL) has been shown to suppress cytokine production in macrophages. We have examined the effect of OdDHL and related compounds on constrictor tone of porcine blood vessels. OdDHL (1-30 microM) caused a concentration-dependent inhibition of U46619-induced contractions of the coronary artery through a largely endothelium-independent mechanism, but was markedly less effective in the pulmonary artery. Quantitively similar effects to those produced by OdDHL were observed with N-(3-oxododecanoyl)-L-homocysteine thiolactone, a thiolactone derivative, while N-3-oxododecanamide, a lactone-free acyl analogue, possessed 1/3rd the potency as a vasorelaxant. Neither N-butanoyl-L-homoserine lactone nor L-homoserine lactone (up to 30 microM) were active. Our findings indicate that OdDHL inhibits vasoconstrictor tone of both pulmonary and coronary blood vessels from the pig. The vasorelaxant action of OdDHL appears to be primarily determined by the N-acyl chain length, with a minor contribution by the homoserine lactone moiety.
Collapse
Affiliation(s)
- R N Lawrence
- School of Biomedical Sciences, The Queen's Medical Centre, Clifton Boulevard, Nottingham, NG7 2UH, UK
| | | | | | | | | | | | | |
Collapse
|
42
|
|
43
|
Winson MK, Swift S, Fish L, Throup JP, Jørgensen F, Chhabra SR, Bycroft BW, Williams P, Stewart GS. Construction and analysis of luxCDABE-based plasmid sensors for investigating N-acyl homoserine lactone-mediated quorum sensing. FEMS Microbiol Lett 1998; 163:185-92. [PMID: 9673021 DOI: 10.1111/j.1574-6968.1998.tb13044.x] [Citation(s) in RCA: 423] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Plasmid reporter vectors have been constructed which respond to activation of LuxR and its homologues LasR and RhlR (VsmR) by N-acyl homoserine lactones (AHLs). The expression of luxCDABE from transcriptional fusions to PluxI, PlasI and PrhlI respectively, occurs in the presence of activating AHLs. A profile of structure/activity relationships is seen where the natural ligand is most potent. The characterisation of individual LuxR homologue/AHL combinations allows a comprehensive evaluation of quorum sensing signals from a test organism.
Collapse
Affiliation(s)
- M K Winson
- Food Microbiology Section, School of Biological Sciences, University of Nottingham, Leics, UK
| | | | | | | | | | | | | | | | | |
Collapse
|
44
|
Kellam B, Bycroft BW, Chan WC, Chhabra SR. Solid phase strategies: Applications of 2-acetyl-4-nitroindane-1,3-dione as a selective protecting group for primary amines. Tetrahedron 1998. [DOI: 10.1016/s0040-4020(98)00365-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
45
|
|
46
|
Jiang Y, Camara M, Chhabra SR, Hardie KR, Bycroft BW, Lazdunski A, Salmond GP, Stewart GS, Williams P. In vitro biosynthesis of the Pseudomonas aeruginosa quorum-sensing signal molecule N-butanoyl-L-homoserine lactone. Mol Microbiol 1998; 28:193-203. [PMID: 9593307 DOI: 10.1046/j.1365-2958.1998.00789.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In Pseudomonas aeruginosa, synthesis of the quorum-sensing signal molecules N-butanoyl-L-homoserine lactone (BHL) and N-hexanoyl-L-homoserine lactone (HHL) requires the Luxl homologue Rhll(Vsml). By using thin-layer chromatography in conjunction with high-performance liquid chromatography (HPLC) and mass spectrometry, we show that purified Rhll can catalyse the biosynthesis of BHL and HHL using either S-adenosylmethionine (SAM) or homoserine lactone (HSL) but not homoserine as the source of the homoserine lactone moiety. As we were unable to detect homoserine lactone in cytoplasmic extracts of Escherichia coli, we conclude that SAM is the natural substrate for Rhll-directed N-acylhomoserine lactone (AHL) biosynthesis. The N-acyl chain of BHL and HHL can be supplied by the appropriately charged coenzyme A derivative (either n-butanoyl-CoA or n-hexanoyl-CoA). The specificity of Rhll for charged CoA derivatives is demonstrated as Rhll was unable to generate AHLs detectable in our bioassays from acetyl-CoA, malonyl-CoA, n-octanoyl-CoA, n-decanoyl-CoA, DL-beta-hydroxybutanoyl-CoA or crotonoyl-CoA. Rhll was also unable to use N-acetyl-S-3-oxobutanoylcysteamine, a chemical mimic for 3-oxobutanoyl-CoA. Furthermore, the Rhll-catalysed synthesis of BHL and HHL was most efficiently driven when NADPH was included in the reaction mixture.
Collapse
Affiliation(s)
- Y Jiang
- Department of Pharmaceutical Sciences, University of Nottingham, UK
| | | | | | | | | | | | | | | | | |
Collapse
|
47
|
Chhabra SR, Hothi B, Evans DJ, White PD, Bycroft BW, Chan WC. An appraisal of new variants of Dde amine protecting group for solid phase peptide synthesis. Tetrahedron Lett 1998. [DOI: 10.1016/s0040-4039(97)10828-0] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
|
48
|
McClean KH, Winson MK, Fish L, Taylor A, Chhabra SR, Camara M, Daykin M, Lamb JH, Swift S, Bycroft BW, Stewart GSAB, Williams P. Quorum sensing and Chromobacterium violaceum: exploitation of violacein production and inhibition for the detection of N-acylhomoserine lactones. Microbiology (Reading) 1997; 143 ( Pt 12):3703-3711. [PMID: 9421896 DOI: 10.1099/00221287-143-12-3703] [Citation(s) in RCA: 1168] [Impact Index Per Article: 43.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Quorum sensing relies upon the interaction of a diffusible signal molecule with a transcriptional activator protein to couple gene expression with cell population density. In Gram-negative bacteria, such signal molecules are usually N-acylhomoserine lactones (AHLs) which differ in the structure of their N-acyl side chains. Chromobacterium violaceum, a Gram-negative bacterium commonly found in soil and water, produces the characteristic purple pigment violacein. Previously the authors described a violacein-negative, mini-Tn5 mutant of C. violaceum (CV026) in which pigment production can be restored by incubation with supernatants from the wild-type strain. To develop this mutant as a general biosensor for AHLs, the natural C. violaceum AHL molecule was first chemically characterized. By using solvent extraction, HPLC and mass spectrometry, a single AHL, N-hexanoyl-L-homoserine lactone (HHL), was identified in wild-type C. violaceum culture supernatants which was absent from CV026. Since the production of violacein constitutes a simple assay for the detection of AHLs, we explored the ability of CV026 to respond to a series of synthetic AHL and N-acylhomocysteine thiolactone (AHT) analogues. In CV026, violacein is inducible by all the AHL and AHT compounds evaluated with N-acyl side chains from C4 to C8 in length, with varying degrees of sensitivity. Although AHL compounds with N-acyl side chains from C10 to C14 are unable to induce violacein production, if an activating AHL (e.g. HHL) is incorporated into the agar, these long-chain AHLs can be detected by their ability to inhibit violacein production. The versatility of CV026 in facilitating detection of AHL mixtures extracted from culture supernatants and separated by thin-layer chromatography is also demonstrated. These simple bioassays employing CV026 thus greatly extend the ability to detect a wide spectrum of AHL signal molecules.
Collapse
Affiliation(s)
- Kay H McClean
- Department of Pharmaceutical Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK
- Department of Applied Biochemistry and Food Science, University of Nottingham, Sutton Bonington Campus, Loughborough LE12 5RD, UK
| | - Michael K Winson
- Department of Pharmaceutical Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK
- Department of Applied Biochemistry and Food Science, University of Nottingham, Sutton Bonington Campus, Loughborough LE12 5RD, UK
| | - Leigh Fish
- Department of Pharmaceutical Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK
- Department of Applied Biochemistry and Food Science, University of Nottingham, Sutton Bonington Campus, Loughborough LE12 5RD, UK
| | - Adrian Taylor
- Department of Pharmaceutical Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK
- Department of Applied Biochemistry and Food Science, University of Nottingham, Sutton Bonington Campus, Loughborough LE12 5RD, UK
| | - Siri Ram Chhabra
- Department of Pharmaceutical Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK
| | - Miguel Camara
- Department of Pharmaceutical Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK
| | - Mavis Daykin
- Department of Pharmaceutical Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK
- Department of Applied Biochemistry and Food Science, University of Nottingham, Sutton Bonington Campus, Loughborough LE12 5RD, UK
| | - John H Lamb
- MRC Toxicology Unit, University of Leicester, Leicester LE1 9HN, UK
| | - Simon Swift
- Department of Pharmaceutical Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK
- Department of Applied Biochemistry and Food Science, University of Nottingham, Sutton Bonington Campus, Loughborough LE12 5RD, UK
| | - Barrie W Bycroft
- Department of Pharmaceutical Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK
| | - Gordon S A B Stewart
- Department of Applied Biochemistry and Food Science, University of Nottingham, Sutton Bonington Campus, Loughborough LE12 5RD, UK
| | - Paul Williams
- Department of Pharmaceutical Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK
| |
Collapse
|
49
|
Swift S, Karlyshev AV, Fish L, Durant EL, Winson MK, Chhabra SR, Williams P, Macintyre S, Stewart GS. Quorum sensing in Aeromonas hydrophila and Aeromonas salmonicida: identification of the LuxRI homologs AhyRI and AsaRI and their cognate N-acylhomoserine lactone signal molecules. J Bacteriol 1997; 179:5271-81. [PMID: 9286976 PMCID: PMC179392 DOI: 10.1128/jb.179.17.5271-5281.1997] [Citation(s) in RCA: 282] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Spent culture supernatants from both Aeromonas hydrophila and Aeromonas salmonicida activate a range of biosensors responsive to N-acylhomoserine lactones (AHLs). The genes for a quorum sensing signal generator and a response regulator were cloned from each Aeromonas species and termed ahyRI and asaRI, respectively. Protein sequence homology analysis places the gene products within the growing family of LuxRI homologs. ahyR and asaR are transcribed divergently from ahyI and asaI, respectively, and in both Aeromonas species, the genes downstream have been identified by DNA sequence and PCR analysis. Downstream of both ahyI and asaI is a gene with close homology to iciA, an inhibitor of chromosome replication in Escherichia coli, a finding which implies that in Aeromonas, cell division may be linked to quorum sensing. The major signal molecule synthesized via both AhyI and AsaI was purified from spent culture supernatants and identified as N-(butanoyl)-L-homoserine lactone (BHL) by thin-layer chromatography, high-pressure liquid chromatography analysis, and mass spectrometry. In addition, a second, minor AHL, N-hexanoyl-L-homoserine lactone, was identified. Transcriptional reporter studies with ahyI::luxCDABE fusions indicate that AhyR and BHL are both required for ahyI transcription. For A. salmonicida, although the addition of exogenous BHL gives only a small stimulation of the production of serine protease with comparison to the control culture, the incorporation of a longer-chain AHL, N-(3-oxodecanoyl)-L-homoserine lactone, reduced the final level (by approximately 50%) and delayed the appearance (from an A650 of 0.9 in the control to an A650 of 1.2 in the test) of protease in the culture supernatant. These data add A. hydrophila and A. salmonicida to the growing family of gram-negative bacteria now known to control gene expression through quorum sensing.
Collapse
Affiliation(s)
- S Swift
- Department of Applied Biochemistry and Food Science, University of Nottingham, Leicestershire, United Kingdom.
| | | | | | | | | | | | | | | | | |
Collapse
|
50
|
Kellam B, Chan WC, Chhabra SR, Bycroft BW. Transient affinity tags based on the Dde protection/deprotection strategy: Synthesis and application of 2-biotinyl-and 2-hexanoyldimedone. Tetrahedron Lett 1997. [DOI: 10.1016/s0040-4039(97)01180-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
|