scholarly journals Specificity and Genetic Polymorphism of theBacillus Competence Quorum-Sensing System

2001 ◽  
Vol 183 (2) ◽  
pp. 451-460 ◽  
Author(s):  
P. Tortosa ◽  
L. Logsdon ◽  
B. Kraigher ◽  
Y. Itoh ◽  
I. Mandic-Mulec ◽  
...  
Keyword(s):  
Genetic Polymorphism ◽  
Quorum Sensing ◽  
Response Regulator ◽  
Two Component System ◽  
Extracellular Medium ◽  
Receptor Proteins ◽  
Sensing System ◽  
Quorum Sensing System ◽  
Isogenic Strains

ABSTRACT A quorum-sensing mechanism involving the pheromone ComX and the ComP-ComA two-component system controls natural competence inBacillus subtilis. ComX is expressed as a cytoplasmic inactive precursor that is released into the extracellular medium as a cleaved, modified decapeptide. This process requires the product ofcomQ. In the presence of ComX, the membrane-localized ComP histidine kinase activates the response regulator ComA. We compared the sequences of the quorum-sensing genes from four closely related bacilli, and we report extensive genetic polymorphism extending throughcomQ, comX, and the 5′ two-thirds ofcomP. This part of ComP encodes the membrane-localized and linker domains of the sensor protein. We also determined the sequences of the comX genes of four additional wild-type bacilli and tested the in vivo activities of all eight pheromones on isogenic strains containing four different ComP receptor proteins. A striking pattern of specificity was discovered, providing strong evidence that the pheromone contacts ComP directly. Furthermore, we show that coexpression of comQ and comX inEscherichia coli leads to the production of active pheromone in the medium, demonstrating that comQ is the only dedicated protein required for the processing, modification, and release of active competence pheromone. Some of the implications of these findings for the evolution and the mechanism of the quorum-sensing system are discussed.

#99: Streptococcus pyogenes Utilizes the Peptide-Based Rgg 2/3 Quorum Sensing System During Oropharyngeal Colonization

2021 ◽  
Vol 10 (Supplement_1) ◽  
pp. S10-S10
Author(s):  
Artemis Gogos ◽  
Michael J Federle
Keyword(s):  
Quorum Sensing ◽  
Streptococcus Pyogenes ◽  
Lymphoid Tissue ◽  
Transcriptional Activator ◽  
Rt Pcr ◽  
Sensing System ◽  
Bacterial Rna ◽  
Quorum Sensing System ◽  
Luciferase Reporters

Abstract Background Streptococcus pyogenes is a human-restricted pathogen most often found in the human nasopharynx. Multiple bacterial factors have been found to contribute to persistent colonization of this niche, and many of these factors are important in mucosal immunity and vaccine development. In this work, we infected mice intranasally with transcriptional regulator mutants of the Rgg2/3 quorum sensing (QS) system—a peptide-based signaling system conserved in all sequenced isolates of S. pyogenes. Methods Three-week-old CD1 mice were intranasally infected with ~107 CFU of S. pyogenes strain MGAS315. Calcium alginate throat swabs were used to monitor nasopharyngeal colonization by the bacteria over time. Luciferase reporters used alongside an IVIS camera were able to show quorum sensing activity levels after inoculation into the mouse nose. Bacterial RNA was isolated from the throat of the mice and quantitative RT–PCR was performed on the samples to corroborate the luciferase reporter data. The nasal-associated lymphoid tissue (NALT) was excised and its supernatants were subjected to 32-plex murine cytokine and chemokine analysis (Millipore). Results Deletion of the QS system’s transcriptional activator (Δrgg2) dramatically diminished the percentage of colonized mice. Deletion of the transcriptional repressor (Δrgg3) increased the percentage of colonized mice compared with wild type. Stimulation of the QS system using synthetic pheromones prior to inoculation did not significantly increase the percentage of animals colonized, indicating that activity of the QS system is responsive to conditions of the host nasopharynx. Mice inoculated with QS-dependent luciferase reporters were subjected to in vivo imaging and showed activation within 1 hour. Bacterial RNA extracted directly from oropharyngeal swabs and evaluated by quantitative RT–PCR subsequently confirmed QS upregulation within 1 hour of inoculation. In the nasal-associated lymphoid tissue (NALT), a muted inflammatory response to the Δrgg2 bacteria suggests that their rapid elimination fails to elicit the previously characterized response to intranasal inoculation of GAS. Conclusions Deletion of the Rgg2 transcriptional activator of the Rgg 2/3 quorum sensing system eliminates colonization of the murine nasopharynx and changes the transcriptional profile of the bacteria in this niche. An existing small-molecule inhibitor of the Rgg2/3 system was unable to inhibit QS activation in vivo, likely due to the suboptimal achievable doses; however, results of our study indicate inhibition of QS may diminish the oropharyngeal colonization of S. pyogenes and argue for further development.

scholarly journals The Enterococcus faecalis fsrB Gene, a Key Component of the fsr Quorum-Sensing System, Is Associated with Virulence in the Rabbit Endophthalmitis Model

2002 ◽  
Vol 70 (8) ◽  
pp. 4678-4681 ◽  
Author(s):  
Eleftherios Mylonakis ◽  
Michael Engelbert ◽  
Xiang Qin ◽  
Costi D. Sifri ◽  
Barbara E. Murray ◽  
...  
Keyword(s):  
Quorum Sensing ◽  
Enterococcus Faecalis ◽  
Deletion Mutant ◽  
Wild Type ◽  
Sensing System ◽  
Quorum Sensing System

ABSTRACT We used a rabbit endophthalmitis model to explore the role of fsrB, a gene required for the function of the fsr quorum-sensing system of Enterococcus faecalis, in pathogenicity. A nonpolar deletion mutant of fsrB had significantly reduced virulence compared to wild type. Complementation of mutation restored virulence. These data corroborate the role of fsrB in E. faecalis pathogenesis and suggest that the rabbit endophthalmitis model can be used to study the in vivo role of quorum sensing.

scholarly journals Escherichia coliO157:H7 Lacking theqseBC-Encoded Quorum-Sensing System Outcompetes the Parental Strain in Colonization of Cattle Intestines

2014 ◽  
Vol 80 (6) ◽  
pp. 1882-1892 ◽  
Author(s):  
V. K. Sharma ◽  
T. A. Casey
Keyword(s):  
Quorum Sensing ◽  
Parental Strain ◽  
Response Regulator ◽  
Stress Hormones ◽  
Gene Encoding ◽  
Fecal Shedding ◽  
Sensing System ◽  
Quorum Sensing System ◽  
Parental Level

ABSTRACTTheqseBC-encoded quorum-sensing system regulates the motility ofEscherichia coliO157:H7 in response to bacterial autoinducer 3 (AI-3) and the mammalian stress hormones epinephrine (E) and norepinephrine (NE). TheqseCgene encodes a sensory kinase that autophosphorylates in response to AI-3, E, or NE and subsequently phosphorylates its cognate response regulator QseB. In the absence of QseC, QseB downregulates bacterial motility and virulence in animal models. In this study, we found that 8- to 10-month-old calves orally inoculated with a mixture ofE. coliO157:H7 and its isogenicqseBCmutant showed significantly higher fecal shedding of theqseBCmutant.In vitroanalysis revealed similar growth profiles and motilities of theqseBCmutant and the parental strain in the presence or absence of NE. The magnitudes of the response to NE and expression of flagellar genesflhDandfliCwere also similar for theqseBCmutant and the parental strain. The expression ofler(a positive regulator of the locus of enterocyte effacement [LEE]), theler-regulatedespAgene, and thecsgAgene (encoding curli fimbriae) was increased in theqseBCmutant compared to the parental strain. On the other hand, growth, motility, and transcription offlhD,fliC,ler,espA, andcsgAwere significantly reduced in theqseBCmutant complemented with a plasmid-cloned copy of theqseBCgenes. Thus,in vitromotility and gene expression data indicate that the near-parental level of motility, ability to respond to NE, and enhanced expression of LEE and curli genes might in part be responsible for increased colonization and fecal shedding of theqseBCmutant in calves.

scholarly journals A Nonsense Mutation in agrA Accounts for the Defect in agr Expression and the Avirulence of Staphylococcus aureus 8325-4 traP::kan

2007 ◽  
Vol 75 (9) ◽  
pp. 4534-4540 ◽  
Author(s):  
Rajan P. Adhikari ◽  
Staffan Arvidson ◽  
Richard P. Novick
Keyword(s):  
Staphylococcus Aureus ◽  
Quorum Sensing ◽  
Mutant Strain ◽  
Nonsense Mutation ◽  
Stop Codon ◽  
Response Regulator ◽  
Wild Type ◽  
Sensing System ◽  
Quorum Sensing System ◽  
Type Sequence

ABSTRACT TraP is a triply phosphorylated staphylococcal protein that has been hypothesized to be the mediator of a second Staphylococcus aureus quorum-sensing system, “SQS1,” that controls expression of the agr system and therefore is essential for the organism's virulence. This hypothesis was based on the loss of agr expression and virulence by a traP mutant of strain 8325-4 and was supported by full complementation of both phenotypic defects by the cloned traP gene in strain NB8 (Y. Gov, I. Borovok, M. Korem, V. K. Singh, R. K. Jayaswal, B. J. Wilkinson, S. M. Rich, and N. Balaban, J. Biol. Chem. 279:14665-14672, 2004), in which the wild-type traP gene was expressed in trans in the 8325-4 traP mutant. We initiated a study of the mechanism by which TraP activates agr and found that the traP mutant strain used for this and other recently published studies has a second mutation, an adventitious stop codon in the middle of agrA, the agr response regulator. The traP mutation, once separated from the agrA defect by outcrossing, had no effect on agr expression or virulence, indicating that the agrA defect accounts fully for the lack of agr expression and for the loss of virulence attributed to the traP mutation. In addition, DNA sequencing showed that the agrA gene in strain NB8 (Gov et al., J. Biol. Chem., 2004), in contrast to that in the agr-defective 8325-4 traP mutant strain, had the wild-type sequence; further, the traP mutation in that strain, when outcrossed, also had no effect on agr expression.

scholarly journals Specificity and genetic polymorphism in the Vfm quorum sensing system of plant pathogenic bacteria of the genus Dickeya

2022 ◽  
Author(s):  
Nicole Hugouvieux‐Cotte‐Pattat ◽  
Monique Royer ◽  
Erwan Gueguen ◽  
Paul Le Guen ◽  
Roderich D. Süssmuth ◽  
...  
Keyword(s):  
Genetic Polymorphism ◽  
Quorum Sensing ◽  
Pathogenic Bacteria ◽  
Plant Pathogenic Bacteria ◽  
Sensing System ◽  
Quorum Sensing System

scholarly journals A Novel Pheromone Quorum-Sensing System Controls the Development of Natural Competence in Streptococcus thermophilus and Streptococcus salivarius

2009 ◽  
Vol 192 (5) ◽  
pp. 1444-1454 ◽  
Author(s):  
Laetitia Fontaine ◽  
Céline Boutry ◽  
Marie Henry de Frahan ◽  
Brigitte Delplace ◽  
Christophe Fremaux ◽  
...  
Keyword(s):  
Quorum Sensing ◽  
Response Regulator ◽  
Streptococcus Thermophilus ◽  
Streptococcus Salivarius ◽  
Gene Encoding ◽  
Component System ◽  
Sensing System ◽  
Quorum Sensing System ◽  
Streptococcal Species ◽  
Transcriptional Induction

ABSTRACT In streptococcal species, the key step of competence development is the transcriptional induction of comX, which encodes the alternative sigma factor σX, which positively regulates genes necessary for DNA transformation. In Streptococcus species belonging to the mitis and mutans groups, induction of comX relies on the activation of a three-component system consisting of a secreted pheromone, a histidine kinase, and a response regulator. In Streptococcus thermophilus, a species belonging to the salivarius group, the oligopeptide transporter Ami is essential for comX expression under competence-inducing conditions. This suggests a different regulation pathway of competence based on the production and reimportation of a signal peptide. The objective of our work was to identify the main actors involved in the early steps of comX induction in S. thermophilus LMD-9. Using a transcriptomic approach, four highly induced early competence operons were identified. Among them, we found a Rgg-like regulator (Ster_0316) associated with a nonannotated gene encoding a 24-amino-acid hydrophobic peptide (Shp0316). Through genetic deletions, we showed that these two genes are essential for comX induction. Moreover, addition to the medium of synthetic peptides derived from the C-terminal part of Shp0316 restored comX induction and transformation of a Shp0316-deficient strain. These peptides also induced competence in S. thermophilus and Streptococcus salivarius strains that are poorly transformable or not transformable. Altogether, our results show that Ster_0316 and Shp0316, renamed ComRS, are the two members of a novel quorum-sensing system responsible for comX induction in species from the salivarius group, which differs from the classical phosphorelay three-component system identified previously in streptococci.

scholarly journals Diversifying Selection at the Bacillus Quorum-Sensing Locus and Determinants of Modification Specificity during Synthesis of the ComX Pheromone

2004 ◽  
Vol 186 (1) ◽  
pp. 15-21 ◽  
Author(s):  
M. Ansaldi ◽  
D. Dubnau
Keyword(s):  
Quorum Sensing ◽  
Protein Interactions ◽  
Response Regulator ◽  
Statistical Tests ◽  
Laboratory Strain ◽  
Nonsynonymous Substitution ◽  
Diversifying Selection ◽  
Sensing System ◽  
Quorum Sensing System ◽  
Natural Isolates

ABSTRACT The competence quorum-sensing system of Bacillus subtilis consists of two-component regulatory proteins, ComP (histidine kinase) and the response regulator, ComA, an extracellular pheromone (ComX), and a protein that is needed for the proteolytic cleavage and modification of pre-ComX (ComQ). ComQ and pre-ComX are both necessary and sufficient for the production of active pheromone, which is released as an isoprenylated peptide. Laboratory strain 168 and a number of natural isolates of bacilli differ in the primary sequences of their pheromones as well as in the masses of their isoprenyl adducts. We have shown that ComX, ComQ, and the membrane-localized sensor domain of ComP are highly polymorphic in natural isolates of bacilli all closely related to the laboratory strain of B. subtilis. In this study, we used two statistical tests (the ratio of synonymous and nonsynonymous substitution rates and the Tajima D test) to demonstrate that these polymorphic sequences evolved by diversifying selection rather than by neutral drift. We show that the choice of isoprenyl derivative is determined by the C-terminal (mature) sequence of pre-ComX rather than by the ComQ protein. The implications of these findings for the evolution of the quorum-sensing system and for the protein-protein interactions involved in determining specificity are discussed.

scholarly journals Characterization of the cciIR Quorum-Sensing System in Burkholderia cenocepacia

2005 ◽  
Vol 73 (8) ◽  
pp. 4982-4992 ◽  
Author(s):  
Rebecca J. Malott ◽  
Adam Baldwin ◽  
Eshwar Mahenthiralingam ◽  
Pamela A. Sokol
Keyword(s):  
Quorum Sensing ◽  
Protease Activity ◽  
Parent Strain ◽  
Response Regulator ◽  
Homoserine Lactone ◽  
Burkholderia Cenocepacia ◽  
Pcr Analysis ◽  
Swarming Motility ◽  
Sensing System ◽  
Quorum Sensing System

ABSTRACT Several transmissible Burkholderia cenocepacia strains that infect multiple cystic fibrosis patients contain a genomic island designated as the cenocepacia island (cci). The cci contains a predicted N-acylhomoserine lactone (AHL) synthase gene, cciI, and a predicted response regulator gene, cciR. AHL production profiles indicated that CciI catalyzes the synthesis of N-hexanoyl-l-homoserine lactone and minor amounts of N-octanoyl-l-homoserine lactone. The cciI and cciR genes were found to be cotranscribed by reverse transcription-PCR analysis, and the expression of a cciIR::luxCDABE fusion in a cciR mutant suggested that the cciIR system negatively regulates its own expression. B. cenocepacia strains also have a cepIR quorum-sensing system. Expression of cepI::luxCDABE or cepR::luxCDABE fusions in a cciR mutant showed that CciR negatively regulates cepI but does not regulate cepR. Expression of the cciIR::luxCDABE fusion in a cepR mutant indicated that functional CepR is required for cciIR expression. Phylogenetic analysis suggested that the cciIR system was acquired by horizontal gene transfer from a distantly related organism and subsequently incorporated into the ancestral cepIR regulatory network. Mutations in cciI, cciR, cepI cciI, and cepR cciR were constructed in B. cenocepacia K56-2. The cciI mutant had greater protease activity and less swarming motility than the parent strain. The cciR mutant had less protease activity than the parent strain. The phenotypes of the cepI cciI and cepR cciR mutants were similar to cepI or cepR mutants, with less protease activity and swarming motility than the parent strain.

scholarly journals Thymol Protects Channel Catfish from Aeromonas hydrophila Infection by Inhibiting Aerolysin Expression and Biofilm Formation

2020 ◽  
Vol 8 (5) ◽  
pp. 636 ◽  
Author(s):  
Jing Dong ◽  
Lushan Zhang ◽  
Yongtao Liu ◽  
Ning Xu ◽  
Shun Zhou ◽  
...  
Keyword(s):  
Quorum Sensing ◽  
Channel Catfish ◽  
Aeromonas Hydrophila ◽  
Biofilm Formation ◽  
Cell Injury ◽  
Opportunistic Pathogen ◽  
Protective Effects ◽  
Sensing System ◽  
Quorum Sensing System

Aeromonas hydrophila is an opportunistic pathogen responsible for a number of diseases in freshwater farming. Moreover, the bacterium has been identified as a zoonotic pathogen that threatens human health. Antibiotics are widely used for treatments of infectious diseases in aquaculture. However, the abuse of antibiotics has led to the emergence of antimicrobial resistant strains. Thus, novel strategies are required against resistant A. hydrophila strains. The quorum sensing (QS) system, involved in virulence factor production and biofilm formation, is a promising target in identifying novel drugs against A. hydrophila infections. In this study, we found that thymol, at sub-inhibitory concentrations, could significantly reduce the production of aerolysin and biofilm formation by inhibiting the transcription of genes aerA, ahyI, and ahyR. These results indicate that thymol inhibits the quorum sensing system. The protective effects of thymol against A. hydrophila mediated cell injury were determined by live/dead assay and lactate dehydrogenase (LDH) release assay. Moreover, the in vivo study showed that thymol could significantly decrease the mortality of channel catfish infected with A. hydrophila. Taken together, these findings demonstrate that thymol could be chosen as a phytotherapeutic candidate for inhibiting quorum sensing system-mediated aerolysin production and biofilm formation in A. hydrophila.

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