Spontaneous quorum-sensing hierarchy reprogramming in Pseudomonas aeruginosa laboratory strain PAO1.
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ABSTRACT:
SUBMITTER: Cheng X
PROVIDER: S-EPMC8792115 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Quorum sensing (QS) is used to coordinate social behaviors, such as virulence and biofilm formation, across bacterial populations. However, the role of QS in regulating phage-bacterium interactions remains unclear. Preventing phage recognition and adsorption are the first steps of bacterial defense against phages; however, both phage recognition and adsorption are a prerequisite for the successful application of phage therapy. In the present study, we report that QS upregulated the expression of phage receptors, thus increasing phage adsorption and infection rates in Pseudomonas aeruginosa. In P. aeruginosa PAO1, we found that las QS, instead of rhl QS, upregulated the expression of galU for lipopolysaccharide synthesis. Lipopolysaccharides act as the receptor of the phage vB_Pae_QDWS. This las QS-mediated phage susceptibility is a dynamic process, depending on host cell density. Our data suggest that inhibiting QS may reduce the therapeutic efficacy of phages. IMPORTANCE Phage resistance is a major limitation of phage therapy, and understanding the mechanisms by which bacteria block phage infection is critical for the successful application of phage therapy. In the present study, we found that Pseudomonas aeruginosa PAO1 uses las QS to promote phage infection by upregulating the expression of galU, which is necessary for the synthesis of phage receptor lipopolysaccharides. In contrast to the results of previous reports, we showed that QS increases the efficacy of phage-mediated bacterial killing. Since QS upregulates the expression of virulence factors and promotes biofilm development, which are positively correlated with lipopolysaccharide production in P. aeruginosa, increased phage susceptibility is a novel QS-mediated trade-off. QS inhibition may increase the efficacy of antibiotic treatment, but it will reduce the effectiveness of phage therapy.
| S-EPMC8764535 | biostudies-literature
Project description:The bacterial pathogen Pseudomonas aeruginosa activates expression of many virulence genes in a cell density-dependent manner by using an intricate quorum-sensing (QS) network. QS in P. aeruginosa involves two acyl-homoserine-lactone circuits, LasI-LasR and RhlI-RhlR. LasI-LasR is required to activate many genes including those coding for RhlI-RhlR. P. aeruginosa causes chronic infections in the lungs of people with cystic fibrosis (CF). In these infections, LasR mutants are common, but rhlR-rhlI expression has escaped LasR regulation in many CF isolates. To better understand the evolutionary trajectory of P. aeruginosa QS in chronic infections, we grew LasR mutants of the well-studied P. aeruginosa strain, PAO1, in conditions that recapitulate an environment where QS signal synthesis by other bacteria might still occur. When QS is required for growth, addition of the RhlI product butyryl-homoserine lactone (C4-HSL), or bacteria that produce C4-HSL, to LasR mutants results in the rapid emergence of a population with a LasR-independent RhlI-RhlR QS system. These evolved populations exhibit subsequent growth without added C4-HSL. The variants that emerge have mutations in mexT, which codes for a transcription factor that controls expression of multiple genes. LasR-MexT mutants have a competitive advantage over both the parent LasR mutant and a LasR-MexT-RhlR mutant. Our findings suggest a plausible evolutionary trajectory for QS in P. aeruginosa CF infections where LasR mutants arise during infection, but because these mutants are surrounded by C4-HSL-producing P. aeruginosa, variants rewired to have a LasR-independent RhlIR system quickly emerge.
| S-EPMC6452656 | biostudies-literature
Project description:Pseudomonas aeruginosa is a major nosocomial pathogen that presents high-level resistance to antibiotics. Its ability to cause infections relies on the production of multiple virulence factors. Quorum sensing (QS) regulates the expression of many of these virulence factors through three QS systems: Las, Rhl, and PQS. The Las system positively regulates the other two systems, so it is at the top of a hierarchized regulation. Nevertheless, clinical and environmental strains that lack a functional Las system have been isolated, and, surprisingly, some of them still have the ability to produce virulence factors and infect animal models, so it has been suggested that the hierarchy is flexible under some conditions or with atypical strains. Here, we analyze the PAO1 type strain and its ΔlasR-derived mutant and report, for the first time, a growth condition (phosphate limitation) where LasR absence has no effect either on virulence factor production or on the gene expression profile, in contrast to a condition of phosphate repletion where the LasR hierarchy is maintained. This work provides evidence on how the QS hierarchy can change from being a strictly LasR-dependent to a LasR-independent RhlR-based hierarchy under phosphate limitation even in the PAO1 type strain.IMPORTANCEPseudomonas aeruginosa is an important pathogen, considered a priority for the development of new therapeutic strategies. An important approach to fight its infections relies on blocking quorum sensing. The Las system is the main regulator of the quorum-sensing response, so many research efforts aim to block this system to suppress the entire response. In this work, we show that LasR is dispensable in a phosphate-limited environment in the PAO1 type strain, which has been used to define the quorum-sensing response hierarchy, and that under this condition RhlR is at the top of the regulation hierarchy. These results are highly significant, since phosphate limitation represents a similar environment to the one that P. aeruginosa faces when establishing infections.
| S-EPMC7890550 | biostudies-literature
Project description:Sulfane sulfur, such as inorganic and organic polysulfide (HSn- and RSn-, n > 2), is a common cellular component, produced either from hydrogen sulfide oxidation or cysteine metabolism. In Pseudomonas aeruginosa PAO1, LasR is a quorum sensing master regulator. After binding its autoinducer, LasR binds to its target DNA to activate the transcription of a suite of genes, including virulence factors. Herein, we report that the production of hydrogen sulfide and sulfane sulfur were positively correlated in P. aeruginosa PAO1, and sulfane sulfur was able to modify LasR, which generated Cys188 persulfide and trisulfide and produced a pentasulfur link between Cys201 and Cys203. The modifications did not affect LasR binding to its target DNA site, but made it several-fold more effective than unmodified LasR in activating transcription in both in vitro and in vivo assays. On the contrary, H2O2 inactivates LasR via producing a disulfide bond between Cys201 and Cys203. P. aeruginosa PAO1 had a high cellular sulfane sulfur and high LasR activity in the mid log phase and early stationary phase, but a low sulfane sulfur and low LasR activity in the declination phase. Thus, sulfane sulfur is a new signaling factor in the bacterium, adding another level of control over LasR-mediated quorum sensing and turning down the activity in old cells.
| S-EPMC8469610 | biostudies-literature
Project description:The administration of macrolides such as azithromycin for chronic pulmonary infection of cystic fibrosis patients has been reported to be of benefit. Although the mechanisms of action remain obscure, anti-inflammatory effects as well as interference of the macrolide with Pseudomonas aeruginosa virulence factor production have been suggested to contribute to an improved clinical outcome. In this study we used a systematic approach and analyzed the impact of azithromycin on the global transcriptional pattern and the protein expression profile of P. aeruginosa PAO1 cultures versus those in untreated controls. The most remarkable result of this study is the finding that azithromycin exhibited extensive quorum-sensing antagonistic activities. In accordance with the inhibition of the quorum-sensing systems, virulence factor production was diminished and the oxidative stress response was impaired, whereas the type III secretion system was strongly induced. Moreover, P. aeruginosa motility was reduced, which probably accounts for the previously observed impaired biofilm formation capabilities of azithromycin-treated cultures. The interference of azithromycin with quorum-sensing-dependent virulence factor production, biofilm formation, and oxidative stress resistance in P. aeruginosa holds great promise for macrolide therapy in cystic fibrosis. Clearly quorum-sensing antagonist macrolides should be paid more attention in the management of chronic P. aeruginosa infections, and as quorum-sensing antagonists, macrolides might gain vital importance for more general application against chronic infections.
| S-EPMC1472232 | biostudies-literature
Project description:Quorum sensing allows bacteria to sense and respond to changes in population density. Acyl-homoserine lactones serve as quorum-sensing signals for many Proteobacteria, and acyl-homoserine lactone signaling is known to control cooperative activities. Quorum-controlled activities vary from one species to another. Quorum-sensing controls a constellation of genes in the opportunistic pathogen Pseudomonas aeruginosa, which thrives in a number of habitats ranging from soil and water to animal hosts. We hypothesized that there would be significant variation in quorum-sensing regulons among strains of P. aeruginosa isolated from different habitats and that differences in the quorum-sensing regulons might reveal insights about the ecology of P. aeruginosa. As a test of our hypothesis we used RNA-seq to identify quorum-controlled genes in seven P. aeruginosa isolates of diverse origins. Although our approach certainly overlooks some quorum-sensing-regulated genes we found a shared set of genes, i.e., a core quorum-controlled gene set, and we identified distinct, strain-variable sets of quorum-controlled genes, i.e., accessory genes. Some quorum-controlled genes in some strains were not present in the genomes of other strains. We detected a correlation between traits encoded by some genes in the strain-variable subsets of the quorum regulons and the ecology of the isolates. These findings indicate a role for quorum sensing in extension of the range of habitats in which a species can thrive. This study also provides a framework for understanding the molecular mechanisms by which quorum-sensing systems operate, the evolutionary pressures by which they are maintained, and their importance in disparate ecological contexts.
| S-EPMC3478653 | biostudies-literature
Project description:Quorum sensing (QS) is one of the key virulence factors in Pseudomonas aeruginosa and causes recalcitrant infections. Multi-drug resistance and biofilm formation seem to be regulated by cell-to-cell communication system through QS. Thus this study is aimed to assess the efficacy of ethanolic leaf extract of Boerhavia diffusa in acting against the QS-regulated virulence traits. Fresh leaves of B. diffusa were dried and the ethanolic crude extract was checked for antimicrobial and anti biofilm effect against P. aeruginosa. The active components and the biological structures were elucidated by GC-MS, HPLC and NMR analysis respectively. Further, computational analyses were also performed to assess the drug ligand interactions based on the docking scores and binding energy. The results suggested that the MIC concentration showed a significant effect in inhibiting the QS network circuit of P. aeruginosa. The docking results showed that leaf had bioactive compounds that exhibit strong binding affinity towards transcriptional activators of the QS circuit in P. aeruginosa, i.e., LasR, as compared to the natural ligands, 3-oxo-C12-HSL and C4-HSL. These results clearly depictthe efficacy of Boerhavia diffusa and its phytoconstituents as promising QS antagonist which can be further applied in the treatment strategies for the diseases caused by P. aeruginosa.
| S-EPMC10557443 | biostudies-literature
Project description:Two clinical isolates of the opportunist pathogen Pseudomonas aeruginosa named PAO1 and PA14 are commonly studied in research laboratories. Despite the isolates being closely related, PA14 exhibits increased virulence compared to that of PAO1 in various models. To determine which players are responsible for the hypervirulence phenotype of the PA14 strain, we elected a transcriptomic approach through RNA sequencing. We found 2,029 genes that are differentially expressed between the two strains, including several genes that are involved with or regulated by quorum sensing (QS), known to control most of the virulence factors in P. aeruginosa Among them, we chose to focus our study on QslA, an antiactivator of QS whose expression was barely detectable in the PA14 strain according our data. We hypothesized that lack of expression of qslA in PA14 could be responsible for higher QS expression in the PA14 strain, possibly explaining its hypervirulence phenotype. After confirming that QslA protein was highly produced in PAO1 but not in the PA14 strain, we obtained evidence showing that a PAO1 deletion strain of qslA has faster QS gene expression kinetics than PA14. Moreover, known virulence factors activated by QS, such as (i) pyocyanin production, (ii) H2-T6SS (type VI secretion system) gene expression, and (iii) Xcp-T2SS (type II secretion system) machinery production and secretion, were all lower in PAO1 than in PA14, due to higher qslA expression. However, biofilm formation and cytotoxicity toward macrophages, although increased in PA14 compared to PAO1, were independent of QslA control. Together, our findings implicated differential qslA expression as a major determinant of virulence factor expression in P. aeruginosa strains PAO1 and PA14.IMPORTANCEPseudomonas aeruginosa is an opportunistic pathogen responsible for acute nosocomial infections and chronic pulmonary infections. P. aeruginosa strain PA14 is known to be hypervirulent in different hosts. Despite several studies in the field, the underlining molecular mechanisms sustaining this phenotype remain enigmatic. Here we provide evidence that the PA14 strain has faster quorum sensing (QS) kinetics than the PAO1 strain, due to the lack of QslA expression, an antiactivator of QS. QS is a major regulator of virulence factors in P. aeruginosa; therefore, we propose that the hypervirulent phenotype of the PA14 strain is, at least partially, due to the lack of QslA expression. This mechanism could be of great importance, as it could be conserved among other P. aeruginosa isolates.
| S-EPMC6779463 | biostudies-literature
Project description:Chronic Pseudomonas aeruginosa infections cause significant morbidity in patients with cystic fibrosis (CF). Over years to decades, P. aeruginosa adapts genetically as it establishes chronic lung infections. Nonsynonymous mutations in lasR, the quorum-sensing (QS) master regulator, are common in CF. In laboratory strains of P. aeruginosa, LasR activates transcription of dozens of genes, including that for another QS regulator, RhlR. Despite the frequency with which lasR coding variants have been reported to occur in P. aeruginosa CF isolates, little is known about their consequences for QS. We sequenced lasR from 2,583 P. aeruginosa CF isolates. The lasR sequences of 580 isolates (22%) coded for polypeptides that differed from the conserved LasR polypeptides of well-studied laboratory strains. This collection included 173 unique lasR coding variants, 116 of which were either missense or nonsense mutations. We studied 31 of these variants. About one-sixth of the variant LasR proteins were functional, including 3 with nonsense mutations, and in some LasR-null isolates, genes that are LasR dependent in laboratory strains were nonetheless expressed. Furthermore, about half of the LasR-null isolates retained RhlR activity. Therefore, in some CF isolates the QS hierarchy is altered such that RhlR quorum sensing is independent of LasR regulation. Our analysis challenges the view that QS-silent P. aeruginosa is selected during the course of a chronic CF lung infection. Rather, some lasR sequence variants retain functionality, and many employ an alternate QS strategy involving RhlR. Chronic Pseudomonas aeruginosa infections, such as those in patients with the genetic disease cystic fibrosis, are notable in that mutants with defects in the quorum-sensing transcription factor LasR frequently arise. In laboratory strains of P. aeruginosa, quorum sensing activates transcription of dozens of genes, many of which encode virulence factors, such as secreted proteases and hydrogen cyanide synthases. In well-studied laboratory strains, LasR-null mutants have a quorum-sensing-deficient phenotype. Therefore, the presence of LasR variants in chronic infections has been interpreted to indicate that quorum-sensing-regulated products are not important for those infections. We report that some P. aeruginosa LasR variant clinical isolates are not LasR-null mutants, and others have uncoupled a second quorum-sensing system, the RhlR system, from LasR regulation. In these uncoupled isolates, RhlR independently activates at least some quorum-sensing-dependent genes. Our findings suggest that quorum sensing plays a role in chronic P. aeruginosa infections, despite the emergence of LasR coding variants.
| S-EPMC5050340 | biostudies-literature
Project description:Pseudomonas aeruginosa PAO1 is the most commonly used strain for research on this ubiquitous and metabolically versatile opportunistic pathogen. Strain PAO1, a derivative of the original Australian PAO isolate, has been distributed worldwide to laboratories and strain collections. Over decades discordant phenotypes of PAO1 sublines have emerged. Taking the existing PAO1-UW genome sequence (named after the University of Washington, which led the sequencing project) as a blueprint, the genome sequences of reference strains MPAO1 and PAO1-DSM (stored at the German Collection for Microorganisms and Cell Cultures [DSMZ]) were resolved by physical mapping and deep short read sequencing-by-synthesis. MPAO1 has been the source of near-saturation libraries of transposon insertion mutants, and PAO1-DSM is identical in its SpeI-DpnI restriction map with the original isolate. The major genomic differences of MPAO1 and PAO1-DSM in comparison to PAO1-UW are the lack of a large inversion, a duplication of a mobile 12-kb prophage region carrying a distinct integrase and protein phosphatases or kinases, deletions of 3 to 1,006 bp in size, and at least 39 single-nucleotide substitutions, 17 of which affect protein sequences. The PAO1 sublines differed in their ability to cope with nutrient limitation and their virulence in an acute murine airway infection model. Subline PAO1-DSM outnumbered the two other sublines in late stationary growth phase. In conclusion, P. aeruginosa PAO1 shows an ongoing microevolution of genotype and phenotype that jeopardizes the reproducibility of research. High-throughput genome resequencing will resolve more cases and could become a proper quality control for strain collections.
| S-EPMC2812968 | biostudies-literature