scholarly journals Non-hierarchical, RhlR-regulated acyl-homoserine lactone quorum sensing in a cystic fibrosis isolate of Pseudomonas aeruginosa

2019 ◽  
Author(s):  
Renae L. Cruz ◽  
Kyle L. Asfahl ◽  
Sara Van den Bossche ◽  
Tom Coenye ◽  
Aurélie Crabbé ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Pseudomonas Aeruginosa ◽  
Quorum Sensing ◽  
Virulence Factors ◽  
Chronic Infection ◽  
Cell Model ◽  
Lung Epithelium ◽  
Independent Manner ◽  
Epithelium Cell ◽  
Regulated Gene Expression

ABSTRACTThe opportunistic pathogen Pseudomonas aeruginosa is a leading cause of airway infection in cystic fibrosis (CF) patients. P. aeruginosa employs several hierarchically arranged and interconnected quorum sensing (QS) regulatory circuits to produce a battery of virulence factors such as elastase, phenazines, and rhamnolipids. The QS transcription factor LasR sits atop this hierarchy, and activates the transcription of dozens of genes, including that encoding the QS regulator RhlR. Paradoxically, inactivating lasR mutations are frequently observed in isolates from CF patients with chronic P. aeruginosa infections. In contrast, mutations in rhlR are rare. We have recently shown that in CF isolates, the QS circuitry is often “rewired” such that RhlR acts in a LasR-independent manner. To begin understanding how QS activity differs in this “rewired” background, we characterized QS activation and RhlR-regulated gene expression in P. aeruginosa E90, a LasR-null, RhlR-active chronic infection isolate. In this isolate, RhlR activates the expression of 53 genes in response to increasing cell density. The genes regulated by RhlR include several that encode virulence factors. Some, but not all, of these genes are present in the QS regulon described in the well-studied laboratory strain PAO1. We also demonstrate that E90 produces virulence factors at similar concentrations to that of PAO1. Unlike PAO1, cytotoxicity by E90 in a three-dimensional lung epithelium cell model is also RhlR-regulated. These data illuminate a “rewired” LasR-independent RhlR regulon in chronic infection isolates and suggest that RhlR may be a target for therapeutic development in chronic infections.AUTHOR SUMMARYPseudomonas aeruginosa is a prominent cystic fibrosis (CF) pathogen that uses quorum sensing (QS) to regulate virulence. In laboratory strains, the key QS regulator is LasR. Some isolates from patients with chronic CF infections appear to use an alternate QS circuitry in which another transcriptional regulator, RhlR, mediates QS. We show that a LasR-null CF clinical isolate engages in QS through RhlR and remains capable of inducing cell death in an in vivo-like lung epithelium cell model. Our findings support the notion that LasR-null clinical isolates can engage in RhlR QS and highlight the centrality of RhlR gene regulation in chronic P. aeruginosa infections.

scholarly journals RhlR-Regulated Acyl-Homoserine Lactone Quorum Sensing in a Cystic Fibrosis Isolate of Pseudomonas aeruginosa

mBio ◽  
2020 ◽  
Vol 11 (2) ◽  
Author(s):  
Renae L. Cruz ◽  
Kyle L. Asfahl ◽  
Sara Van den Bossche ◽  
Tom Coenye ◽  
Aurélie Crabbé ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Pseudomonas Aeruginosa ◽  
Quorum Sensing ◽  
Virulence Factors ◽  
Chronic Infection ◽  
Cell Model ◽  
Lung Epithelium ◽  
Content Type ◽  
Epithelium Cell ◽  
Regulated Gene Expression

ABSTRACT The opportunistic pathogen Pseudomonas aeruginosa is a leading cause of airway infection in cystic fibrosis (CF) patients. P. aeruginosa employs several hierarchically arranged and interconnected quorum sensing (QS) regulatory circuits to produce a battery of virulence factors such as elastase, phenazines, and rhamnolipids. The QS transcription factor LasR sits atop this hierarchy and activates the transcription of dozens of genes, including that encoding the QS regulator RhlR. Paradoxically, inactivating lasR mutations are frequently observed in isolates from CF patients with chronic P. aeruginosa infections. In contrast, mutations in rhlR are rare. We have recently shown that in CF isolates, the QS circuitry is often rewired such that RhlR acts in a LasR-independent manner. To begin understanding how QS activity differs in this rewired background, we characterized QS activation and RhlR-regulated gene expression in P. aeruginosa E90, a LasR-null, RhlR-active chronic infection isolate. In this isolate, RhlR activates the expression of 53 genes in response to increasing cell density. The genes regulated by RhlR include several that encode virulence factors. Some, but not all, of these genes are present in the QS regulon described in the well-studied laboratory strain PAO1. We also demonstrate that E90 produces virulence factors at similar concentrations as PAO1, and in E90, RhlR plays a significant role in mediating cytotoxicity in a three-dimensional lung epithelium cell model. These data illuminate a rewired LasR-independent RhlR regulon in chronic infection isolates and suggest further investigation of RhlR as a possible target for therapeutic development in chronic infections. IMPORTANCE Pseudomonas aeruginosa is a prominent cystic fibrosis (CF) pathogen that uses quorum sensing (QS) to regulate virulence. In laboratory strains, the key QS regulator is LasR. Many isolates from patients with chronic CF infections appear to use an alternate QS circuitry in which another transcriptional regulator, RhlR, mediates QS. We show that a LasR-null CF clinical isolate engages in QS through RhlR and remains capable of inducing cell death in an in vivo-like lung epithelium cell model. Our findings support the notion that LasR-null clinical isolates can engage in RhlR QS and highlight the centrality of RhlR in chronic P. aeruginosa infections.

scholarly journals Pseudomonas aeruginosa PA80 is a cystic fibrosis isolate deficient in RhlRI quorum sensing

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Syed A. K. Shifat Ahmed ◽  
Michelle Rudden ◽  
Sabrina M. Elias ◽  
Thomas J. Smyth ◽  
Roger Marchant ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Pseudomonas Aeruginosa ◽  
Quorum Sensing ◽  
Virulence Factors ◽  
Genomic Islands ◽  
Clinical Strain ◽  
Whole Genome ◽  
Synonymous Mutations ◽  
Wide Range

AbstractPseudomonas aeruginosa uses quorum sensing (QS) to modulate the expression of several virulence factors that enable it to establish severe infections. The QS system in P. aeruginosa is complex, intricate and is dominated by two main N-acyl-homoserine lactone circuits, LasRI and RhlRI. These two QS systems work in a hierarchical fashion with LasRI at the top, directly regulating RhlRI. Together these QS circuits regulate several virulence associated genes, metabolites, and enzymes in P. aeruginosa. Paradoxically, LasR mutants are frequently isolated from chronic P. aeruginosa infections, typically among cystic fibrosis (CF) patients. This suggests P. aeruginosa can undergo significant evolutionary pathoadaptation to persist in long term chronic infections. In contrast, mutations in the RhlRI system are less common. Here, we have isolated a clinical strain of P. aeruginosa from a CF patient that has deleted the transcriptional regulator RhlR entirely. Whole genome sequencing shows the rhlR locus is deleted in PA80 alongside a few non-synonymous mutations in virulence factors including protease lasA and rhamnolipid rhlA, rhlB, rhlC. Importantly we did not observe any mutations in the LasRI QS system. PA80 does not appear to have an accumulation of mutations typically associated with several hallmark pathoadaptive genes (i.e., mexT, mucA, algR, rpoN, exsS, ampR). Whole genome comparisons show that P. aeruginosa strain PA80 is closely related to the hypervirulent Liverpool epidemic strain (LES) LESB58. PA80 also contains several genomic islands (GI’s) encoding virulence and/or resistance determinants homologous to LESB58. To further understand the effect of these mutations in PA80 QS regulatory and virulence associated genes, we compared transcriptional expression of genes and phenotypic effects with isogenic mutants in the genetic reference strain PAO1. In PAO1, we show that deletion of rhlR has a much more significant impact on the expression of a wide range of virulence associated factors rather than deletion of lasR. In PA80, no QS regulatory genes were expressed, which we attribute to the inactivation of the RhlRI QS system by deletion of rhlR and mutation of rhlI. This study demonstrates that inactivation of the LasRI system does not impact RhlRI regulated virulence factors. PA80 has bypassed the common pathoadaptive mutations observed in LasR by targeting the RhlRI system. This suggests that RhlRI is a significant target for the long-term persistence of P. aeruginosa in chronic CF patients. This raises important questions in targeting QS systems for therapeutic interventions.

scholarly journals Pseudomonas aeruginosa lasRTranscription Correlates with the Transcription of lasA,lasB, and toxA in Chronic Lung Infections Associated with Cystic Fibrosis

1998 ◽  
Vol 66 (6) ◽  
pp. 2521-2528 ◽  
Author(s):  
Douglas G. Storey ◽  
Eva E. Ujack ◽  
Harvey R. Rabin ◽  
Ian Mitchell
Keyword(s):  
Cystic Fibrosis ◽  
Pseudomonas Aeruginosa ◽  
Quorum Sensing ◽  
Virulence Factors ◽  
Rank Correlation ◽  
Transcript Accumulation ◽  
Bacterial Populations ◽  
Sensing System ◽  
Quorum Sensing System ◽  
Lung Infections

ABSTRACT The role of Pseudomonas aeruginosa quorum-sensing systems in the lung infections associated with cystic fibrosis (CF) has not been examined. The purpose of this study was to determine if genes regulated by the LasR-LasI quorum-sensing system were coordinately regulated by the P. aeruginosa populations during the lung infections associated with CF. We also wanted to ascertain if there was a relationship between the expression of lasR, a transcriptional regulator, and some P. aeruginosa virulence factors during these infections. We extracted RNAs from the bacterial populations of 131 sputa taken from 23 CF patients. These RNAs were blotted and hybridized with probes to P. aeruginosa lasA,lasB, and toxA. The hybridization signals from each probe were ranked, and the rankings were analyzed by a Spearman rank correlation to determine if there was an association between the population transcript accumulations for the three genes. The correlations between the transcript accumulation patterns of pairs of the genes suggested that lasA, lasB, andtoxA might be coordinately regulated during CF lung infections. To determine if this coordinate regulation might be due to regulation by LasR, we probed RNAs, extracted from 84 sputa, with thelasR, lasA, lasB, toxA, and algD probes. Statistical analysis indicated thatlasR transcript accumulation correlated tolasA, lasB, toxA, andalgD transcript accumulations. These results indicated thatlasR may at least partially regulate or be coordinately regulated with lasA, lasB, toxA, and algD during the lung infections associated with CF. These results also suggested that the LasR-LasI quorum-sensing system may control the expression of at least some virulence factors in the lungs of patients with CF.

scholarly journals Identification of Five Structurally Unrelated Quorum-Sensing Inhibitors of Pseudomonas aeruginosa from a Natural-Derivative Database

2013 ◽  
Vol 57 (11) ◽  
pp. 5629-5641 ◽  
Author(s):  
Sean Yang-Yi Tan ◽  
Song-Lin Chua ◽  
Yicai Chen ◽  
Scott A. Rice ◽  
Staffan Kjelleberg ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Quorum Sensing ◽  
Virulence Factors ◽  
Extracellular Dna ◽  
Signal Molecules ◽  
Dependent Manner ◽  
Absolute Quantitation ◽  
Content Type ◽  
Quorum Sensing Inhibitors ◽  
Regulated Gene Expression

ABSTRACTBacteria communicate by means of small signal molecules in a process termed quorum sensing (QS). QS enables bacteria to organize their activities at the population level, including the coordinated secretion of virulence factors. Certain small-molecule compounds, known as quorum-sensing inhibitors (QSIs), have been shown to effectively block QS and subsequently attenuate the virulence ofPseudomonas aeruginosa, as well as increasing its susceptibility to both antibiotics and the immune system. In this study, a structure-based virtual screening (SB-VS) approach was used for the discovery of novel QSI candidates. Three-dimensional structures of 3,040 natural compounds and their derivatives were obtained, after which molecular docking was performed using the QS receptor LasR as a target. Based on docking scores and molecular masses, 22 compounds were purchased to determine their efficacies as quorum-sensing inhibitors. Using a live reporter assay for quorum sensing, 5 compounds were found to be able to inhibit QS-regulated gene expression inP. aeruginosain a dose-dependent manner. The most promising compound, G1, was evaluated by isobaric tag for relative and absolute quantitation (iTRAQ)-based proteomic analysis, and it was found to significantly affect the abundance of 46 proteins (19 were upregulated; 27 were downregulated) inP. aeruginosaPAO1. It specifically reduced the expression of several quorum-sensing-regulated virulence factors, such as protease IV, chitinase, and pyoverdine synthetases. G1 was also able to reduce extracellular DNA release and inhibited the secretion of the virulence factor, elastase, whose expression is regulated by LasR. These results demonstrate the utility of SB-VS for the discovery of target-specific QSIs.

scholarly journals Revisiting the quorum-sensing hierarchy in Pseudomonas aeruginosa: the transcriptional regulator RhlR regulates LasR-specific factors

Microbiology ◽  
2009 ◽  
Vol 155 (3) ◽  
pp. 712-723 ◽  
Author(s):  
Valérie Dekimpe ◽  
Eric Déziel
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Quorum Sensing ◽  
Virulence Factors ◽  
Transcriptional Regulator ◽  
Homoserine Lactone ◽  
The Other ◽  
Virulence Determinants ◽  
Late Stationary Phase ◽  
Regulatory Systems ◽  
Specific Factors

Pseudomonas aeruginosa uses the two major quorum-sensing (QS) regulatory systems las and rhl to modulate the expression of many of its virulence factors. The las system is considered to stand at the top of the QS hierarchy. However, some virulence factors such as pyocyanin have been reported to still be produced in lasR mutants under certain conditions. Interestingly, such mutants arise spontaneously under various conditions, including in the airways of cystic fibrosis patients. Using transcriptional lacZ reporters, LC/MS quantification and phenotypic assays, we have investigated the regulation of QS-controlled factors by the las system. Our results show that activity of the rhl system is only delayed in a lasR mutant, thus allowing the expression of multiple virulence determinants such as pyocyanin, rhamnolipids and C4-homoserine lactone (HSL) during the late stationary phase. Moreover, at this stage, RhlR is able to overcome the absence of the las system by activating specific LasR-controlled functions, including production of 3-oxo-C12-HSL and Pseudomonas quinolone signal (PQS). P. aeruginosa is thus able to circumvent the deficiency of one of its QS systems by allowing the other to take over. This work demonstrates that the QS hierarchy is more complex than the model simply presenting the las system above the rhl system.

Chronic Infection With Pseudomonas aeruginosa in Cystic Fibrosis

2013 ◽  
Vol 95 (12) ◽  
pp. 1548-1553 ◽  
Author(s):  
Domenic Vital ◽  
David Holzmann ◽  
Annette Boehler ◽  
Markus Hofer
Keyword(s):  
Cystic Fibrosis ◽  
Pseudomonas Aeruginosa ◽  
Chronic Infection

scholarly journals Role of quorum sensing by Pseudomonas aeruginosa in microbial keratitis and cystic fibrosis

Microbiology ◽  
2008 ◽  
Vol 154 (8) ◽  
pp. 2184-2194 ◽  
Author(s):  
M. D. P. Willcox ◽  
H. Zhu ◽  
T. C. R. Conibear ◽  
E. B. H. Hume ◽  
M. Givskov ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Pseudomonas Aeruginosa ◽  
Quorum Sensing ◽  
Microbial Keratitis

scholarly journals The YebC Family Protein PA0964 Negatively Regulates the Pseudomonas aeruginosa Quinolone Signal System and Pyocyanin Production

2008 ◽  
Vol 190 (18) ◽  
pp. 6217-6227 ◽  
Author(s):  
Haihua Liang ◽  
Lingling Li ◽  
Zhaolin Dong ◽  
Michael G. Surette ◽  
Kangmin Duan
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Quorum Sensing ◽  
Virulence Factors ◽  
Response Regulator ◽  
Initial Study ◽  
Pfam Family ◽  
Swarming Motility ◽  
Sensing Systems ◽  
Family Protein ◽  
Pyocyanin Production

ABSTRACT Bacterial pathogenicity is often manifested by the expression of various cell-associated and secreted virulence factors, such as exoenzymes, protease, and toxins. In Pseudomonas aeruginosa, the expression of virulence genes is coordinately controlled by the global regulatory quorum-sensing systems, which includes the las and rhl systems as well as the Pseudomonas quinolone signal (PQS) system. Phenazine compounds are among the virulence factors under the control of both the rhl and PQS systems. In this study, regulation of the phzA1B1C1D1E1 (phzA1) operon, which is involved in phenazine synthesis, was investigated. In an initial study of inducing conditions, we observed that phzA1 was induced by subinhibitory concentrations of tetracycline. Screening of 13,000 mutants revealed 32 genes that altered phzA1 expression in the presence of subinhibitory tetracycline concentrations. Among them, the gene PA0964, designated pmpR ( p qsR-mediated P QS r egulator), has been identified as a novel regulator of the PQS system. It belongs to a large group of widespread conserved hypothetical proteins with unknown function, the YebC protein family (Pfam family DUF28). It negatively regulates the quorum-sensing response regulator pqsR of the PQS system by binding at its promoter region. Alongside phzA1 expression and phenazine and pyocyanin production, a set of virulence factors genes controlled by both rhl and the PQS were shown to be modulated by PmpR. Swarming motility and biofilm formation were also significantly affected. The results added another layer of regulation in the rather complex quorum-sensing systems in P. aeruginosa and demonstrated a clear functional clue for the YebC family proteins.

Possible antivirulent activity of some agents against clinical isolates of Pseudomonas aeruginosa

2021 ◽  
Vol 30 (2) ◽  
pp. 1-8
Author(s):  
Ahmad O. Rifai ◽  
Abeer M. Abd El-Aziz ◽  
Hany I. Kenawy
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Quorum Sensing ◽  
Virulence Factors ◽  
Therapeutic Target ◽  
Inhibitory Action ◽  
Antibacterial Agents ◽  
Mechanisms Of Resistance ◽  
Life Threatening ◽  
Pheniramine Maleate ◽  
Pyocyanin Production

Background: Pseudomonas aeruginosa has developed different mechanisms of resistance against antibiotics and became one of the most life-threatening pathogens. Fighting against its virulence Factors are an alternative therapeutic target. Objective: This study was directed towards the investigation of anti-quorum sensing activity and inhibitory action on virulence factors of different agents including antibacterial agents to which Pseudomonas aeruginosa isolates are resistant and non-antibacterial agents. Methodology: Anti-quorum sensing activity of ceftriaxone, ceftazidime (CAZ), cefepime (FEP), vancomycin (VA), paracetamol (PA), and pheniramine maleate (PHE) investigated as well as their ability to reduce other virulence factors including protease, hemolysin, and pyocyanin production. Results: This study showed that 3rd and 4th generations cephalosporins could be used as anti-quorum sensing agents effectively in the treatment of Pseudomonas aeruginosa infections, however, vancomycin, paracetamol, and pheniramine maleate had no effect on inhibiting the studied virulence factors. Conclusion: From our study we conclude that although cephalosporins at the used concentrations did not show anti-pseudomonal activity they were effective as anti virulent agents that could be utilized in therapeutically in controlling Pseudomonas aeruginosa infections.

Sign in / Sign up

Export Citation Format

Share Document