scholarly journals Discovery of an inhibitor of the production of the Pseudomonas aeruginosa virulence factor pyocyanin in wild-type cells

2016 ◽  
Vol 12 ◽  
pp. 1428-1433 ◽  
Author(s):  
Bernardas Morkunas ◽  
Balint Gal ◽  
Warren R J D Galloway ◽  
James T Hodgkinson ◽  
Brett M Ibbeson ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Quorum Sensing ◽  
Cell Signalling ◽  
Opportunistic Pathogen ◽  
Wild Type ◽  
Wide Range ◽  
Potential Applications ◽  
Therapeutic Context ◽  
Pyocyanin Production

Pyocyanin is a small molecule produced by Pseudomonas aeruginosa that plays a crucial role in the pathogenesis of infections by this notorious opportunistic pathogen. The inhibition of pyocyanin production has been identified as an attractive antivirulence strategy for the treatment of P. aeruginosa infections. Herein, we report the discovery of an inhibitor of pyocyanin production in cultures of wild-type P. aeruginosa which is based around a 4-alkylquinolin-2(1H)-one scaffold. To the best of our knowledge, this is the first reported example of pyocyanin inhibition by a compound based around this molecular framework. The compound may therefore be representative of a new structural sub-class of pyocyanin inhibitors, which could potentially be exploited in in a therapeutic context for the development of critically needed new antipseudomonal agents. In this context, the use of wild-type cells in this study is notable, since the data obtained are of direct relevance to native situations. The compound could also be of value in better elucidating the role of pyocyanin in P. aeruginosa infections. Evidence suggests that the active compound reduces the level of pyocyanin production by inhibiting the cell–cell signalling mechanism known as quorum sensing. This could have interesting implications; quorum sensing regulates a range of additional elements associated with the pathogenicity of P. aeruginosa and there is a wide range of other potential applications where the inhibition of quorum sensing is desirable.

scholarly journals Protist predation can favour cooperation within bacterial species

2013 ◽  
Vol 9 (5) ◽  
pp. 20130548 ◽  
Author(s):  
Ville-Petri Friman ◽  
Stephen P. Diggle ◽  
Angus Buckling
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Quorum Sensing ◽  
Public Goods ◽  
Trophic Interactions ◽  
Bacterial Species ◽  
Cell Signalling ◽  
Opportunistic Pathogen ◽  
Wild Type ◽  
Floating Cell ◽  
Cell Aggregations

Here, we studied how protist predation affects cooperation in the opportunistic pathogen bacterium Pseudomonas aeruginosa , which uses quorum sensing (QS) cell-to-cell signalling to regulate the production of public goods. By competing wild-type bacteria with QS mutants (cheats), we show that a functioning QS system confers an elevated resistance to predation. Surprisingly, cheats were unable to exploit this resistance in the presence of cooperators, which suggests that resistance does not appear to result from activation of QS-regulated public goods. Instead, elevated resistance of wild-type bacteria was related to the ability to form more predation-resistant biofilms. This could be explained by the expression of QS-regulated resistance traits in densely populated biofilms and floating cell aggregations, or alternatively, by a pleiotropic cost of cheating where less resistant cheats are selectively removed from biofilms. These results show that trophic interactions among species can maintain cooperation within species, and have further implications for P. aeruginosa virulence in environmental reservoirs by potentially enriching the cooperative and highly infective strains with functional QS system.

scholarly journals Differential Regulation of Twitching Motility and Elastase Production by Vfr in Pseudomonas aeruginosa

2002 ◽  
Vol 184 (13) ◽  
pp. 3605-3613 ◽  
Author(s):  
Scott A. Beatson ◽  
Cynthia B. Whitchurch ◽  
Jennifer L. Sargent ◽  
Roger C. Levesque ◽  
John S. Mattick
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Quorum Sensing ◽  
Binding Pocket ◽  
Receptor Protein ◽  
Twitching Motility ◽  
Wild Type ◽  
Type Iv ◽  
Allelic Deletion ◽  
Pyocyanin Production ◽  
Null Mutants

ABSTRACT Vfr, a homolog of Escherichia coli cyclic AMP (cAMP) receptor protein, has been shown to regulate quorum sensing, exotoxin A production, and regA transcription in Pseudomonas aeruginosa. We identified a twitching motility-defective mutant that carries a transposon insertion in vfr and confirmed that vfr is required for twitching motility by construction of an independent allelic deletion-replacement mutant of vfr that exhibited the same phenotype, as well as by the restoration of normal twitching motility by complementation of these mutants with wild-type vfr. Vfr-null mutants exhibited severely reduced twitching motility with barely detectable levels of type IV pili, as well as loss of elastase production and altered pyocyanin production. We also identified reduced-twitching variants of quorum-sensing mutants (PAK lasI::Tc) with a spontaneous deletion in vfr (S. A. Beatson, C. B. Whitchurch, A. B. T. Semmler, and J. S. Mattick, J. Bacteriol., 184:3598-3604, 2002), the net result of which was the loss of five residues (EQERS) from the putative cAMP-binding pocket of Vfr. This allele (VfrΔEQERS) was capable of restoring elastase and pyocyanin production to wild-type levels in vfr-null mutants but not their defects in twitching motility. Furthermore, structural analysis of Vfr and VfrΔEQERS in relation to E. coli CRP suggests that Vfr is capable of binding both cAMP and cyclic GMP whereas VfrΔEQERS is only capable of responding to cAMP. We suggest that Vfr controls twitching motility and quorum sensing via independent pathways in response to these different signals, bound by the same cyclic nucleotide monophosphate-binding pocket.

scholarly journals The Quorum-Sensing Negative Regulator RsaL of Pseudomonas aeruginosa Binds to the lasI Promoter

2006 ◽  
Vol 188 (2) ◽  
pp. 815-819 ◽  
Author(s):  
Giordano Rampioni ◽  
Iris Bertani ◽  
Elisabetta Zennaro ◽  
Fabio Polticelli ◽  
Vittorio Venturi ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Quorum Sensing ◽  
Binding Site ◽  
Opportunistic Pathogen ◽  
Bidirectional Promoter ◽  
Homoserine Lactone ◽  
Negative Regulator ◽  
Direct Demonstration ◽  
Dna Binding Site

ABSTRACT A mutation in the rsaL gene of Pseudomonas aeruginosa produces dramatically higher amounts of N-acyl homoserine lactone with respect to the wild type, highlighting the key role of this negative regulator in controlling quorum sensing (QS) in this opportunistic pathogen. The DNA binding site of the RsaL protein on the rsaL-lasI bidirectional promoter partially overlaps the binding site of the LasR protein, consistent with the hypothesis that RsaL and LasR could be in binding competition on this promoter. This is the first direct demonstration that RsaL acts as a QS negative regulator by binding to the lasI promoter.

scholarly journals The three NADH dehydrogenases of Pseudomonas aeruginosa: Their roles in energy metabolism and links to virulence

PLoS ONE ◽  
2021 ◽  
Vol 16 (2) ◽  
pp. e0244142
Author(s):  
Teri N. Hreha ◽  
Sara Foreman ◽  
Ana Duran-Pinedo ◽  
Andrew R. Morris ◽  
Patricia Diaz-Rodriguez ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Opportunistic Pathogen ◽  
Lag Phase ◽  
Deletion Mutants ◽  
Wild Type ◽  
Nadh:Quinone Oxidoreductase ◽  
Double Deletion ◽  
Single Deletion ◽  
Nadh Dehydrogenases ◽  
Pyocyanin Production

Pseudomonas aeruginosa is a ubiquitous opportunistic pathogen which relies on a highly adaptable metabolism to achieve broad pathogenesis. In one example of this flexibility, to catalyze the NADH:quinone oxidoreductase step of the respiratory chain, P. aeruginosa has three different enzymes: NUO, NQR and NDH2, all of which carry out the same redox function but have different energy conservation and ion transport properties. In order to better understand the roles of these enzymes, we constructed two series of mutants: (i) three single deletion mutants, each of which lacks one NADH dehydrogenase and (ii) three double deletion mutants, each of which retains only one of the three enzymes. All of the mutants grew approximately as well as wild type, when tested in rich and minimal medium and in a range of pH and [Na+] conditions, except that the strain with only NUO (ΔnqrFΔndh) has an extended lag phase. During exponential phase, the NADH dehydrogenases contribute to total wild-type activity in the following order: NQR > NDH2 > NUO. Some mutants, including the strain without NQR (ΔnqrF) had increased biofilm formation, pyocyanin production, and killed more efficiently in both macrophage and mouse infection models. Consistent with this, ΔnqrF showed increased transcription of genes involved in pyocyanin production.

Characterization of Pseudomonas aeruginosa Quorum Sensing Inhibitors from the Endophyte Lasiodiplodia venezuelensis and Evaluation of Their Antivirulence Effects by Metabolomics

2021 ◽  
Vol 9 (9) ◽  
pp. 1807
Author(s):  
Léonie Pellissier ◽  
Sara Leoni ◽  
Laurence Marcourt ◽  
Emerson Ferreira Queiroz ◽  
Nicole Lecoultre ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Quorum Sensing ◽  
Virulence Factors ◽  
Antimicrobial Agents ◽  
Fungal Endophytes ◽  
Opportunistic Pathogen ◽  
Single Step ◽  
Bioactive Natural Products ◽  
Quorum Sensing Inhibitors ◽  
Wide Range

The opportunistic pathogen Pseudomonas aeruginosa is one of the “critical priority pathogens” due to its multidrug resistance to a wide range of antibiotics. Its ability to invade and damage host tissues is due to the use of quorum sensing (QS) to collectively produce a plethora of virulence factors. Inhibition of QS is an attractive strategy for new antimicrobial agents because it disrupts the initial events of infection without killing the pathogen. Highly diverse microorganisms as endophytes represent an under-explored source of bioactive natural products, offering opportunities for the discovery of novel QS inhibitors (QSI). In the present work, the objective was to explore selective QSIs within a unique collection of fungal endophytes isolated from the tropical palm Astrocaryum sciophilum. The fungi were cultured, extracted, and screened for their antibacterial and specific anti-QS activities against P. aeruginosa. The endophytic strain Lasiodiplodia venezuelensis was prioritized for scaled-up fractionation for its selective activity, leading to the isolation of eight compounds in a single step. Among them, two pyran-derivatives were found to be responsible for the QSI activity, with an effect on some QS-regulated virulence factors. Additional non-targeted metabolomic studies on P. aeruginosa documented their effects on the production of various virulence-related metabolites.

scholarly journals A Distinct QscR Regulon in the Pseudomonas aeruginosa Quorum-Sensing Circuit

2006 ◽  
Vol 188 (9) ◽  
pp. 3365-3370 ◽  
Author(s):  
Yannick Lequette ◽  
Joon-Hee Lee ◽  
Fouzia Ledgham ◽  
Andrée Lazdunski ◽  
E. Peter Greenberg
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Quorum Sensing ◽  
Opportunistic Pathogen ◽  
Homoserine Lactone ◽  
Acyl Homoserine Lactone ◽  
Signal Molecule ◽  
Control Of Gene Expression ◽  
Signaling Systems ◽  
Sensing Systems

ABSTRACT The opportunistic pathogen Pseudomonas aeruginosa possesses two complete acyl-homoserine lactone (acyl-HSL) signaling systems. One system consists of LasI and LasR, which generate a 3-oxododecanoyl-homoserine lactone signal and respond to that signal, respectively. The other system is RhlI and RhlR, which generate butanoyl-homoserine lactone and respond to butanoyl-homoserine lactone, respectively. These quorum-sensing systems control hundreds of genes. There is also an orphan LasR-RhlR homolog, QscR, for which there is no cognate acyl-HSL synthetic enzyme. We previously reported that a qscR mutant is hypervirulent and showed that QscR transiently represses a few quorum-sensing-controlled genes. To better understand the role of QscR in P. aeruginosa gene regulation and to better understand the relationship between QscR, LasR, and RhlR control of gene expression, we used transcription profiling to identify a QscR-dependent regulon. Our analysis revealed that QscR activates some genes and represses others. Some of the repressed genes are not regulated by the LasR-I or RhlR-I systems, while others are. The LasI-generated 3-oxododecanoyl-homoserine lactone serves as a signal molecule for QscR. Thus, QscR appears to be an integral component of the P. aeruginosa quorum-sensing circuitry. QscR uses the LasI-generated acyl-homoserine lactone signal and controls a specific regulon that overlaps with the already overlapping LasR- and RhlR-dependent regulons.

scholarly journals The Pseudomonas Quinolone Signal Regulates rhl Quorum Sensing in Pseudomonas aeruginosa

2000 ◽  
Vol 182 (10) ◽  
pp. 2702-2708 ◽  
Author(s):  
Susan L. McKnight ◽  
Barbara H. Iglewski ◽  
Everett C. Pesci
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Quorum Sensing ◽  
Opportunistic Pathogen ◽  
Homoserine Lactone ◽  
Sensing System ◽  
Sensing Systems ◽  
Pseudomonas Quinolone Signal ◽  
Quorum Sensing System ◽  
Encoding Gene

ABSTRACT The opportunistic pathogen Pseudomonas aeruginosa uses intercellular signals to control the density-dependent expression of many virulence factors. The las and rhlquorum-sensing systems function, respectively, through the autoinducersN-(3-oxododecanoyl)-l-homoserine lactone andN-butyryl-l-homoserine lactone (C4-HSL), which are known to positively regulate the transcription of the elastase-encoding gene, lasB. Recently, we reported that a second type of intercellular signal is involved in lasB induction. This signal was identified as 2-heptyl-3-hydroxy-4-quinolone and designated thePseudomonas quinolone signal (PQS). PQS was determined to be part of the quorum-sensing hierarchy since its production and bioactivity depended on the las and rhlquorum-sensing systems, respectively. In order to define the role of PQS in the P. aeruginosa quorum-sensing cascade,lacZ gene fusions were used to determine the effect of PQS on the transcription of the quorum-sensing system geneslasR, lasI, rhlR, andrhlI. We found that in P. aeruginosa, PQS caused a major induction of rhlI′-lacZ and had lesser effects on the transcription of lasR′-lacZ andrhlR′-lacZ. We also observed that the transcription of bothrhlI′-lacZ and lasB′-lacZ was cooperatively effected by C4-HSL and PQS. Additionally, we present data indicating that PQS was not produced maximally until cultures reached the late stationary phase of growth. Taken together, our results imply that PQS acts as a link between the las and rhlquorum-sensing systems and that this signal is not involved in sensing cell density.

scholarly journals The effect of Quorum sensing inhibitors on the evolution of CRISPR-based phage immunity in Pseudomonas aeruginosa

2021 ◽  
Author(s):  
Jenny M. Broniewski ◽  
Matthew A. W. Chisnall ◽  
Nina Molin Høyland-Kroghsbo ◽  
Angus Buckling ◽  
Edze R. Westra
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Quorum Sensing ◽  
Evolutionary Dynamics ◽  
Opportunistic Pathogen ◽  
Specific Phage ◽  
Type Iv ◽  
Quorum Sensing Inhibitors ◽  
Wide Range ◽  
Chemical Inhibition ◽  
Adsorption Rates

AbstractQuorum sensing controls the expression of a wide range of important traits in the opportunistic pathogen Pseudomonas aeruginosa, including the expression of virulence genes and its CRISPR-cas immune system, which protects from bacteriophage (phage) infection. This finding has led to the speculation that synthetic quorum sensing inhibitors could be used to limit the evolution of CRISPR immunity during phage therapy. Here we use experimental evolution to explore if and how a quorum sensing inhibitor influences the population and evolutionary dynamics of P. aeruginosa upon phage DMS3vir infection. We find that chemical inhibition of quorum sensing decreases phage adsorption rates due to downregulation of the Type IV pilus, which causes delayed lysis of bacterial cultures and favours the evolution of CRISPR immunity. Our data therefore suggest that inhibiting quorum sensing may reduce rather than improve the therapeutic efficacy of pilus-specific phage, and this is likely a general feature when phage receptors are positively regulated by quorum sensing.

scholarly journals A complex hierarchical quorum-sensing circuitry modulates phenazine gene expression in Pseudomonas aeruginosa

2018 ◽  
Vol 11 (12) ◽  
pp. 919-925
Author(s):  
Norhan Khairy Abd El-Aziz ◽  
Marwa Ibrahim Abd El-Hamid ◽  
El-sayed Youssef El-Naenaeey
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Quorum Sensing ◽  
Point Mutations ◽  
Strain Analysis ◽  
Signal Molecules ◽  
Transcription Analysis ◽  
Transcript Levels ◽  
Wide Range ◽  
Positive Correlations ◽  
Pyocyanin Production

Introduction: Pseudomonas aeruginosa (P. aeruginosa) modulates the expression of a myriad of virulence factors via two complicated hierarchical quorum-sensing (QS) cascade. This study shed light on the interrelation between P. aeruginosa QS systems and pyocyanin production. Methodology: Transcription analysis of lasR, rhlR, rhlI and phz genes using quantitative real time-reverse transcriptase PCR (qRT–PCR) assay, followed by sequencing of the autoinducer synthase (lasI gene) were applied for 15 P. aeruginosa strains recovered from diverse animal clinical sources. Results: Expression studies revealed that most P. aeruginosa strains demonstrated statistically significant differences (p < 0.05) with a very wide range of transcript levels of QS and phz genes in comparison to P. aeruginosa ATCC 27853. We have identified significant positive correlations (r ≥ 0.3) between the expressions of QS and phz genes in eleven analyzed strains, whereas pyocyanin production positively correlated with the expression of lasR only in three strains (r ≥ 0.6). We further found that there was a negative correlation between the transcript levels of QS and phz genes in one bacterial strain. Analysis of lasI sequences showed point mutations explaining the alterations in pyocyanin expression. The deficiencies of lasI, lasR and rhlI with rhlR-dependent expression of phz in one strain were also recorded. Conclusions: These results provided new insights to the pivotal role of QS signal molecules on pyocyanin production presenting the las system as the dominant regulator.

scholarly journals Intraspecies Signaling between Common Variants of Pseudomonas aeruginosa Increases Production of Quorum-Sensing-Controlled Virulence Factors

mBio ◽  
2020 ◽  
Vol 11 (4) ◽  
Author(s):  
Dallas L. Mould ◽  
Nico J. Botelho ◽  
Deborah A. Hogan
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Quorum Sensing ◽  
Opportunistic Pathogen ◽  
Loss Of Function ◽  
Wild Type ◽  
Chronic Infections ◽  
Content Type ◽  
Complex Interactions ◽  
Natural Settings ◽  
Citrate Release

ABSTRACT The opportunistic pathogen Pseudomonas aeruginosa damages hosts through the production of diverse secreted products, many of which are regulated by quorum sensing (QS). The lasR gene, which encodes a central QS regulator, is frequently mutated in clinical isolates from chronic infections, and loss of LasR function (LasR−) generally impairs the activity of downstream QS regulators RhlR and PqsR. We found that in cocultures containing LasR+ and LasR− strains, LasR− strains hyperproduce the RhlR/RhlI-regulated antagonistic factors pyocyanin and rhamnolipids in diverse models and media and in different strain backgrounds. Diffusible QS autoinducers produced by the wild type were not required for this effect. Using transcriptomics, genetics, and biochemical approaches, we uncovered a reciprocal interaction between wild-type and lasR mutant pairs wherein the iron-scavenging siderophore pyochelin produced by the lasR mutant induced citrate release and cross-feeding from the wild type. Citrate, a metabolite often secreted in low iron environments, stimulated RhlR signaling and RhlI levels in LasR−but not in LasR+ strains. These studies reveal the potential for complex interactions between recently diverged, genetically distinct isolates within populations from single chronic infections. IMPORTANCE Coculture interactions between lasR loss-of-function and LasR+ Pseudomonas aeruginosa strains may explain the worse outcomes associated with the presence of LasR− strains. More broadly, this report illustrates how interactions within a genotypically diverse population, similar to those that frequently develop in natural settings, can promote unpredictably high virulence factor production.

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