Transcriptional regulation of Pseudomonas aeruginosa rhlR, encoding a quorum-sensing regulatory protein

Microbiology ◽  
2003 ◽  
Vol 149 (11) ◽  
pp. 3073-3081 ◽  
Author(s):  
Gerardo Medina ◽  
Katy Juárez ◽  
Rafael Díaz ◽  
Gloria Soberón-Chávez
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Transcriptional Regulation ◽  
Quorum Sensing ◽  
Regulatory Protein ◽  
Culture Conditions ◽  
Transcriptional Level ◽  
Coding Region ◽  
Upstream Gene ◽  
Transcription Start Sites ◽  
Response Systems

The Pseudomonas aeruginosa rhlR gene encodes the transcriptional regulator RhlR which has a central role in the quorum-sensing response. Different gene products involved in bacterial pathogenesis are regulated at the transcriptional level by two quorum-sensing response systems, Las and Rhl. The expression of rhlR has been reported to be under the control of the Las system, but its transcriptional regulation has not been studied in detail. Here, the rhlR promoter region has been characterized and shown to present four different transcription start sites, two of which are included in the upstream gene (rhlB) coding region. It was found that rhlR expression is not only dependent on LasR but also on different regulatory proteins such as Vfr and RhlR itself, and also on the alternative sigma factor σ 54. It is reported that rhlR expression is partially LasR-independent under certain culture conditions and is strongly influenced by environmental factors.

scholarly journals Transcriptional regulation of Pseudomonas aeruginosa rhlR: role of the CRP orthologue Vfr (virulence factor regulator) and quorum-sensing regulators LasR and RhlR

Microbiology ◽  
2011 ◽  
Vol 157 (9) ◽  
pp. 2545-2555 ◽  
Author(s):  
Gerardo Croda-García ◽  
Victoria Grosso-Becerra ◽  
Abigail Gonzalez-Valdez ◽  
Luis Servín-González ◽  
Gloria Soberón-Chávez
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Transcriptional Regulation ◽  
Quorum Sensing ◽  
Binding Sites ◽  
Regulatory Network ◽  
Coding Region ◽  
Transcription Start ◽  
Transcription Start Sites ◽  
Negative Effect

The production of many virulence factors by Pseudomonas aeruginosa is regulated by the quorum-sensing (QS) response. In this regulatory network LasR and RhlR, bound to their corresponding autoinducers, play a central role. The QS response has a hierarchical structure: LasR/3O-C12-HSL activates the transcription of rhlR, and RhlR/C4-HSL activates the transcription of several genes, including the rhlAB operon, which encodes the enzymes responsible for rhamnolipid synthesis. The rhlAB operon is located immediately upstream of the rhlR gene. rhlR has four transcription start sites, two of which are located in the rhlB coding region. Vfr directly activates transcription of lasR, and has been reported to be also involved in rhlR expression. The aim of this work was to characterize the details of the mechanism of rhlR transcriptional regulation. We show that Vfr directly regulates rhlR transcription through its binding to several Vfr-binding sites (VBSs) present in the rhlR promoter region, one of which has a negative effect on transcription. Two of the VBSs overlap with las boxes where LasR/3O-C12-HSL binds to activate rhlR transcription. We also show that rhlR transcription is subject to positive-feedback autoregulation through RhlR/C4-HSL activation of the rhlA promoter. This positive autoregulation plays a major role in rhlR expression.

Global regulation in Pseudomonas aeruginosa: the regulatory protein AlgR2 (AlgQ) acts as a modulator of quorum sensing

2003 ◽  
Vol 154 (3) ◽  
pp. 207-213 ◽  
Author(s):  
Fouzia Ledgham ◽  
Chantal Soscia ◽  
Ananda Chakrabarty ◽  
Andrée Lazdunski ◽  
Maryline Foglino
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Quorum Sensing ◽  
Regulatory Protein ◽  
Global Regulation

scholarly journals Evaluation of the Antibacterial and Investigation of the Molecular Docking of New Derivatives of 1, 3, 4-Oxadiazole as Inhibitors of Quorum Sensing System in the Human Pathogen Pseudomonas Aeruginosa

2021 ◽  
Vol 8 (1) ◽  
pp. 27-33
Author(s):  
Sepideh Ghameshlouei ◽  
Nakisa Zarrabi Ahrabi ◽  
Ali Souldozi ◽  
Yasin SarveAhrabi
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Molecular Docking ◽  
Quorum Sensing ◽  
Regulatory Protein ◽  
Inhibitory Effect ◽  
Chemical Structures ◽  
Sensing System ◽  
Wide Range ◽  
Quorum Sensing System ◽  
Derivatives Of

Background: Oxadiazoles are a group of anti-inflammatory compounds that have a wide range of activity due to their higher efficacy. Pseudomonas aeruginosa is an opportunistic pathogen and a major pathogen of nosocomial infections. This study aimed to evaluate the antibacterial and investigation of the molecular docking of new derivatives of 1, 3, 4-oxadiazole against P. aeruginosa, in vitro & in silico. Materials and Methods: Four new derivatives were synthesized and added to our previous synthetic derivatives of 1, 3, 4-oxadiazole. The antibacterial activity of all derivatives was measured based on three standard species of P. aeruginosa using inhibition zone (IZ) and minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) methods. Then, employing the computational design of the drug by the molecular docking method, the inhibitory effect of synthetic compounds on the LasR regulatory protein of P. aeruginosa quorum sensing system was investigated, which plays an important role in regulating the expression of pathogenic genes in bacteria. Results: The chemical structures of new compounds were characterized by IR spectra and 1H-NMR. A variety of inhibitory effects were observed by the synthesized compounds – compound 4d and 4g, in particular. Also, the inhibitory effect of these two compounds on the LasR regulatory protein under the control of the quorum sensing system in P. aeruginosa was demonstrated by molecular docking. Conclusions: The results of this study showed that the two compounds containing the functional group of naphthalene and fluorophenyl have a significant effect on the inhibition of P. aeruginosa, as well as on the LasR protein of this bacterium.

Notch1 Expression Is Regulated at Post-Transcriptional Level by 3′UTR Region in Hematopoietic Stem Cell Development

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 2457-2457
Author(s):  
Shin-ichi Mizuno ◽  
Hidetoshi Ozawa ◽  
Tadafumi Iino ◽  
Yojiro Arinobu ◽  
Chong Yong ◽  
...  
Keyword(s):  
Transcriptional Regulation ◽  
Stem Cell ◽  
Hematopoietic Stem Cell ◽  
Transcriptional Control ◽  
Regulation Of Gene Expression ◽  
Cell Development ◽  
Transcriptional Level ◽  
Coding Region ◽  
Hematopoietic Stem ◽  
Hematopoietic Development

Abstract In hematopoietic stem cell development, the expression of critical genes is precisely regulated in a stage specific manner, which supports normal hematopoietic development through adequately regulating timing of cell division, self-renewal, and lineage commitment. Regulation of gene expression is known to take place at least at transcriptional level. In addition to the transcriptional regulation, there are growing evidences that post-transcriptional control of critical genes may play an important role, suggesting an interesting possibility that post-transcriptional control may also play a role in hematopoiesis. Here, we provide the evidence that the expression of Notch1, a key factor in lymphoid development, is controlled at post-transcriptional level in hematopoietic stem cell (HSC). By quantitative PCR, Notch1 mRNA is substantially expressed at HSCs as well as common lymphoid progenitors (CLPs) or double negative (DN) thymocytes. However, Notch1 protein is detected at very low level in HSCs compared to CLPs or DN thymocytes, suggesting that Notch1 expression is regulated at post-transcriptional level in HSC. To investigate the effect of 3′UTR (untranslated region) on post-transcriptional regulation, we prepared a retrovirus sensor vector, in which 3′UTR of target gene is placed between the GFP coding region and the retrovirus 3′LTR, and found that induction of the sensor vector with the 3′UTR sequence of Notch1 showed marked suppression of the GFP intensity at the HSC stage. This effect was not observed when we introduced the vector into DN thymocytes. Suppression of Notch1 by its 3′UTR was further confirmed by using a retrovirus vector which has two distinct markers of YFP and GFP-3′UTR fusion genes under bi-directional EF1 promoter. Deletion mutant analysis showed that the responsible region required for this post-transcriptional suppression is confined to 120-bp sequence within Notch1 3′UTR so far. These data suggest that the expression of Notch1 should be regulated at post-transcriptional level by its 3′UTR at the HSC stage and our data provide the first evidence that the stage-specific translational regulation can play an important role in organization of hematopoietic development.

scholarly journals A Novel Operon Encoding Formaldehyde Fixation: the Ribulose Monophosphate Pathway in the Gram-Positive Facultative Methylotrophic Bacterium Mycobacterium gastri MB19

2000 ◽  
Vol 182 (4) ◽  
pp. 944-948 ◽  
Author(s):  
Ryoji Mitsui ◽  
Yasuyoshi Sakai ◽  
Hisashi Yasueda ◽  
Nobuo Kato
Keyword(s):  
Phylogenetic Tree ◽  
Regulatory Protein ◽  
Open Reading Frames ◽  
Methylotrophic Bacterium ◽  
Transcriptional Level ◽  
Coding Region ◽  
Gram Positive ◽  
Hybridization Probe ◽  
Ribulose Monophosphate Pathway ◽  
Insight Into

ABSTRACT A 4.2-kb PstI fragment harboring the gene cluster of the ribulose monophosphate (RuMP) pathway for formaldehyde fixation was identified in the chromosome of a gram-positive, facultative methylotroph, Mycobacterium gastri MB19, by using the coding region of 3-hexulose-6-phosphate synthase (HPS) as the hybridization probe. The PstI fragment contained three complete open reading frames (ORFs) which encoded from the 5′ end, a DNA-binding regulatory protein (rmpR), 6-phospho-3-hexuloisomerase (PHI; rmpB), and HPS (rmpA). Sequence analysis suggested that rmpAand rmpB constitute an operon, and Northern blot analysis of RNA extracted from bacteria grown under various conditions suggested that the expression of the two genes is similarly regulated at the transcriptional level. A similarity search revealed that the proteins encoded by rmpA and rmpB in M. gastri MB19 show high similarity to the unidentified proteins of nonmethylotrophic prokaryotes, including bacteria and anaerobic archaea. The clusters in the phylogenetic tree of the HPS protein ofM. gastri MB19 and those in the phylogenetic tree of the PHI protein were nearly identical, which implies that these two formaldehyde-fixing genes evolved as a pair. These findings give new insight into the acquisition of the formaldehyde fixation pathway during the evolution of diverse microorganisms.

scholarly journals Mechanism of Pseudomonas aeruginosa RhlR Transcriptional Regulation of the rhlAB Promoter

2003 ◽  
Vol 185 (20) ◽  
pp. 5976-5983 ◽  
Author(s):  
Gerardo Medina ◽  
Katy Juárez ◽  
Brenda Valderrama ◽  
Gloria Soberón-Chávez
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Transcriptional Regulation ◽  
Quorum Sensing ◽  
Regulatory Region ◽  
Transcriptional Repressor ◽  
Homoserine Lactone ◽  
Specific Sequence ◽  
Regulated Expression ◽  
Transcription Regulators ◽  
Repressor Activity

ABSTRACT Pseudomonas aeruginosa contains two transcription regulators (LasR and RhlR) that, when complexed with their specific autoinducers (3-oxo-dodecanoyl-homoserine lactone and butanoyl-homoserine lactone, respectively) activate transcription of different virulence-associated traits. We studied the RhlR-dependent transcriptional regulation of the rhlAB operon encoding rhamnosyltransferase 1, an enzyme involved in the synthesis of the surfactant monorhamnolipid, and showed that RhlR binds to a specific sequence in the rhlAB regulatory region, both in the presence and in the absence of its autoinducer. Our data suggest that in the former case it activates transcription, whereas in the latter it acts as a transcriptional repressor of this promoter. RhlR seems to repress the transcription of other quorum-sensing-regulated genes; thus, RhlR repressor activity might be of importance in the finely regulated expression of P. aeruginosa virulence-associated traits.

scholarly journals Effects of 14-Alpha-Lipoyl Andrographolide on Quorum Sensing in Pseudomonas aeruginosa

2012 ◽  
Vol 56 (12) ◽  
pp. 6088-6094 ◽  
Author(s):  
Li Ma ◽  
Xiangyang Liu ◽  
Haihua Liang ◽  
Yizhou Che ◽  
Caixia Chen ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Quorum Sensing ◽  
Antimicrobial Agents ◽  
Synergistic Effects ◽  
Homoserine Lactone ◽  
Inhibitory Effect ◽  
Transcriptional Level ◽  
Dependent Manner ◽  
Content Type ◽  
Conventional Antibiotics

ABSTRACTInPseudomonas aeruginosa, the quorum-sensing (QS) system is closely related to biofilm formation. We previously demonstrated that 14-alpha-lipoyl andrographolide (AL-1) has synergistic effects on antibiofilm and antivirulence factors (pyocyanin and exopolysaccharide) ofP. aeruginosawhen combined with conventional antibiotics, while it has little inhibitory effect on its growth. However, its molecular mechanism remains elusive. Here we investigated the effect of AL-1 on QS systems, especially the Las and Rhl systems. This investigation showed that AL-1 can inhibit LasR–3-oxo-C12-homoserine lactone (HSL) interactions and repress the transcriptional level of QS-regulated genes. Reverse transcription (RT)-PCR data showed that AL-1 significantly reduced the expression levels oflasR,lasI,rhlR, andrhlIin a dose-dependent manner. AL-1 not only decreased the expression level of Psl, which is positively regulated by the Las system, but also increased the level of secretion of ExoS, which is negatively regulated by the Rhl system, indicating that AL-1 has multiple effects on both the Las and Rhl systems. It is no wonder that AL-1 showed synergistic effects with other antimicrobial agents in the treatment ofP. aeruginosainfections.

scholarly journals Role of quorum sensing in UVA-induced biofilm formation in Pseudomonas aeruginosa

Microbiology ◽  
2020 ◽  
Vol 166 (8) ◽  
pp. 735-750 ◽  
Author(s):  
Magdalena Pezzoni ◽  
Ramón A. Pizarro ◽  
Cristina S. Costa
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Quorum Sensing ◽  
Biofilm Formation ◽  
Type Species ◽  
Transcriptional Level ◽  
Content Type ◽  
Link Type ◽  
Opportunistic Human Pathogen ◽  
Biofilm Development

Pseudomonas aeruginosa , a versatile bacterium present in terrestrial and aquatic environments and a relevant opportunistic human pathogen, is largely known for the production of robust biofilms. The unique properties of these structures complicate biofilm eradication, because they make the biofilms very resistant to diverse antibacterial agents. Biofilm development and establishment is a complex process regulated by multiple regulatory genetic systems, among them is quorum sensing (QS), a mechanism employed by bacteria to regulate gene transcription in response to population density. In addition, environmental factors such as UVA radiation (400–315 nm) have been linked to biofilm formation. In this work, we further investigate the mechanism underlying the induction of biofilm formation by UVA, analysing the role of QS in this phenomenon. We demonstrate that UVA induces key genes of the Las and Rhl QS systems at the transcriptional level. We also report that pelA and pslA genes, which are essential for biofilm formation and whose transcription depends in part on QS, are significantly induced under UVA exposure. Finally, the results demonstrate that in a relA strain (impaired for ppGpp production), the UVA treatment does not induce biofilm formation or QS genes, suggesting that the increase of biofilm formation due to exposure to UVA in P. aeruginosa could rely on a ppGpp-dependent QS induction.

scholarly journals The Pseudomonas aeruginosa Exotoxin A Regulatory Gene, ptxS: Evidence for Negative Autoregulation

1999 ◽  
Vol 181 (16) ◽  
pp. 4890-4895 ◽  
Author(s):  
Britta L. Swanson ◽  
Jane A. Colmer ◽  
Abdul N. Hamood
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Regulatory Gene ◽  
Regulatory Protein ◽  
Binding Activity ◽  
Upstream Region ◽  
Transcriptional Level ◽  
Exotoxin A ◽  
Specific Sequence ◽  
T7 Promoter ◽  
Gel Shift

ABSTRACT We have previously described a Pseudomonas aeruginosagene, ptxR, which enhances exotoxin A production at the transcriptional level. We have also described another gene,ptxS, which is transcribed divergently fromptxR and interferes with the enhancement of exotoxin A synthesis by ptxR. However, the mechanisms through whichptxR and/or ptxS are regulated is not known. In this study, we attempted (by using the DNA gel shift assay) to determine if P. aeruginosa contains a potential regulatory protein that binds specifically to the ptxR orptxS upstream region. In the initial analysis, different-sized gel shift bands were detected when a probe containing the ptxR-ptxS intergenic region was incubated with the lysate of P. aeruginosa PAO1. The strongest binding activity was detected with a smaller fragment that represents theptxS upstream region. Additional deletion analysis localized the binding to a 52-bp fragment immediately upstream ofptxS. The gel shift band was not detected when the 52-bp fragment was incubated with the lysate of the ptxS isogenic mutant PAO1::ptxS. However, the binding band was regenerated when a plasmid carrying ptxS intact was introduced into PAO1::ptxS. In addition, the gel shift band was detected when the 52-bp fragment was incubated with a lysate of Escherichia coli in which ptxS was overexpressed from the T7 promoter. The effect of PtxS onptxS expression was examined by using aptxS-lacZ fusion plasmid. The level of β-galactosidase activity produced by PAO1::ptxS carrying the fusion plasmid was four- to fivefold higher than that produced by PAO1 carrying the same plasmid. Using DNase I footprinting analysis, the binding region was specified to a 20-bp fragment. Within the fragment, a 14-bp palindromic sequence exists that may function as a PtxS binding site. These results suggest that PtxS autoregulates its synthesis by binding to a specific sequence within the ptxSupstream region.

scholarly journals Quorum Sensing Negatively Regulates Hemolysin Transcriptionally and Posttranslationally in Vibrio cholerae

2009 ◽  
Vol 78 (1) ◽  
pp. 461-467 ◽  
Author(s):  
Amy M. Tsou ◽  
Jun Zhu
Keyword(s):  
Transcription Factor ◽  
Transcriptional Regulation ◽  
Quorum Sensing ◽  
Vibrio Cholerae ◽  
Transcriptional Level ◽  
Disease Symptoms ◽  
Liquid Cultures ◽  
Solid Media ◽  
Cytotoxic Proteins ◽  
First Time

ABSTRACT Recent work has shown that in addition to cholera toxin (CT) and the toxin-coregulated pilus (TCP), other cytotoxic proteins in Vibrio cholerae also cause disease symptoms, and this is particularly evident in strains lacking CT. One such protein is the hemolysin encoded by hlyA. Here we show that, like CT and TCP, HlyA is repressed by the quorum-sensing-regulated transcription factor HapR. This repression occurs on two levels: one at the transcriptional level that is independent of the metalloprotease HapA and one at the posttranslational level that is mediated by HapA. The transcriptional regulation is significantly more apparent on solid media than in liquid cultures. This is the first time that hemolysis has been shown to be directly regulated by quorum sensing in V. cholerae, and it is interesting that, like other virulence factors, HlyA is also repressed by HapR, which is expressed late in infection.

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