scholarly journals The hanR/hanI quorum-sensing system of Halomonas anticariensis, a moderately halophilic bacterium

Microbiology ◽  
2011 ◽  
Vol 157 (12) ◽  
pp. 3378-3387 ◽  
Author(s):  
Ali Tahrioui ◽  
Emilia Quesada ◽  
Inmaculada Llamas
Keyword(s):  
Quorum Sensing ◽  
Halophilic Bacterium ◽  
Transcriptional Analysis ◽  
Signal Molecules ◽  
Rt Pcr ◽  
Significant Group ◽  
Signalling Molecules ◽  
Sensing System ◽  
Moderately Halophilic Bacterium ◽  
Quorum Sensing System

Quorum sensing is a cell density-dependent gene expression mechanism found in many Gram-negative bacteria which involves the production of signal molecules such as N-acylhomoserine lactones (AHLs). One significant group of micro-organisms in which quorum sensing has not been previously studied, however, are the moderate halophiles. We describe here the results of our studies of the quorum-sensing system in Halomonas anticariensis FP35T, which is composed of luxR/luxI homologues: hanR (the putative transcriptional regulator gene) and hanI (the autoinducer synthase gene). To understand how the hanR/hanI system is organized and regulated we conducted RT-PCR and quantitative real-time PCR assays. Transcriptional analysis indicated that the hanR and hanI genes are on the same transcript and that their transcription is growth phase-dependent. HanI seems to be the only autoinducer synthase responsible for the synthesis of AHLs by the bacterium, since the inactivation of hanI resulted in the complete loss of its AHLs. We also found that the hanI gene appears to be transcribed from its own promoter and that its expression does not depend upon HanR. This finding was supported by the fact that the FP35hanR mutant showed AHL-producing activity and hanI expression similar to that of the wild-type strain, the latter being measured by RT-PCR. Moreover, hanR is expressed from its own promoter and appears to be independent of the AHL signalling molecules produced by HanI.

#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 Quorum-Sensing System and Stationary-Phase Sigma Factor (rpoS) of the Onion Pathogen Burkholderia cepacia Genomovar I Type Strain, ATCC 25416

2003 ◽  
Vol 69 (3) ◽  
pp. 1739-1747 ◽  
Author(s):  
Claudio Aguilar ◽  
Iris Bertani ◽  
Vittorio Venturi
Keyword(s):  
Quorum Sensing ◽  
Stationary Phase ◽  
Sigma Factor ◽  
Burkholderia Cepacia ◽  
Type Strain ◽  
Plant Pathogens ◽  
Signal Molecules ◽  
Strain Atcc ◽  
Sensing System ◽  
Quorum Sensing System

ABSTRACT Bacterial strains belonging to Burkholderia cepacia can be human opportunistic pathogens, plant pathogens, and plant growth promoting and have remarkable catabolic activity. B. cepacia consists of several genomovars comprising what is now known as the B. cepacia complex. Here we report the quorum-sensing system of a genomovar I onion rot type strain ATCC 25416. Quorum sensing is a cell-density-dependent regulatory response which involves the production of N-acyl homoserine lactone (HSL) signal molecules. The cep locus has been inactivated in the chromosome, and it has been shown that CepI is responsible for the biosynthesis of an N-hexanoyl HSL (C6-HSL) and an N-octanoyl HSL (C8-HSL) and that the cep locus regulates protease production as well as onion pathogenicity via the expression of a secreted polygalacturonase. A cep-lacZ-based sensor plasmid has been constructed and used to demonstrate that CepR responded to C6-HSL with only 15% of the molar efficiency of C8-HSL, that a cepR knockout mutant synthesized 70% less HSLs, and that CepR responded best towards long-chain HSLs. In addition, we also report the cloning and characterization of the stationary-phase sigma factor gene rpoS of B. cepacia ATCC 25416. It was established that quorum sensing in B. cepacia has a negative effect on rpoS expression as determined by using an rpoS-lacZ transcriptional fusion; on the other hand, rpoS-null mutants displayed no difference in the accumulation of HSL signal molecules.

scholarly journals Quorum Sensing Regulates Denitrification in Pseudomonas aeruginosa PAO1

2007 ◽  
Vol 189 (13) ◽  
pp. 4969-4972 ◽  
Author(s):  
Masanori Toyofuku ◽  
Nobuhiko Nomura ◽  
Tatsuya Fujii ◽  
Naoki Takaya ◽  
Hideaki Maseda ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Quorum Sensing ◽  
Homoserine Lactone ◽  
Anaerobic Growth ◽  
Signal Molecules ◽  
Pseudomonas Aeruginosa Pao1 ◽  
Sensing System ◽  
Quorum Sensing System ◽  
Denitrification Activity

ABSTRACT Anaerobic growth of Pseudomonas aeruginosa PAO1 was affected by quorum sensing. Deletion of genes that produce N-acyl-l-homoserine lactone signals resulted in an increase in denitrification activity, which was repressed by exogenous signal molecules. The effect of the las quorum-sensing system was dependent on the rhl quorum-sensing system in regulating denitrification.

scholarly journals An OmpA Family Protein, a Target of the GinI/GinR Quorum-Sensing System in Gluconacetobacter intermedius, Controls Acetic Acid Fermentation

2008 ◽  
Vol 190 (14) ◽  
pp. 5009-5019 ◽  
Author(s):  
Aya Iida ◽  
Yasuo Ohnishi ◽  
Sueharu Horinouchi
Keyword(s):  
Acetic Acid ◽  
Quorum Sensing ◽  
Gluconic Acid ◽  
Transcriptional Analysis ◽  
Nucleotide Sequencing ◽  
Acid Fermentation ◽  
Acetic Acid Fermentation ◽  
Sensing System ◽  
Family Protein ◽  
Quorum Sensing System

ABSTRACT Via N-acylhomoserine lactones, the GinI/GinR quorum-sensing system in Gluconacetobacter intermedius NCI1051, a gram-negative acetic acid bacterium, represses acetic acid and gluconic acid fermentation. Two-dimensional polyacrylamide gel electrophoretic analysis of protein profiles of strain NCI1051 and ginI and ginR mutants identified a protein that was produced in response to the GinI/GinR regulatory system. Cloning and nucleotide sequencing of the gene encoding this protein revealed that it encoded an OmpA family protein, named GmpA. gmpA was a member of the gene cluster containing three adjacent homologous genes, gmpA to gmpC, the organization of which appeared to be unique to vinegar producers, including “Gluconacetobacter polyoxogenes.” In addition, GmpA was unique among the OmpA family proteins in that its N-terminal membrane domain forming eight antiparallel transmembrane β-strands contained an extra sequence in one of the surface-exposed loops. Transcriptional analysis showed that only gmpA of the three adjacent gmp genes was activated by the GinI/GinR quorum-sensing system. However, gmpA was not controlled directly by GinR but was controlled by an 89-amino-acid protein, GinA, a target of this quorum-sensing system. A gmpA mutant grew more rapidly in the presence of 2% (vol/vol) ethanol and accumulated acetic acid and gluconic acid in greater final yields than strain NCI1051. Thus, GmpA plays a role in repressing oxidative fermentation, including acetic acid fermentation, which is unique to acetic acid bacteria and allows ATP synthesis via ethanol oxidation. Consistent with the involvement of gmpA in oxidative fermentation, its transcription was also enhanced by ethanol and acetic acid.

scholarly journals Identification and Characterization of a GDSL Esterase Gene Located Proximal to the swr Quorum-Sensing System of Serratia liquefaciens MG1

2003 ◽  
Vol 69 (7) ◽  
pp. 3901-3910 ◽  
Author(s):  
Kathrin Riedel ◽  
Daniela Talker-Huiber ◽  
Michael Givskov ◽  
Helmut Schwab ◽  
Leo Eberl
Keyword(s):  
Quorum Sensing ◽  
Extracellular Enzymes ◽  
Tween 80 ◽  
Homoserine Lactone ◽  
Growth Conditions ◽  
Tween 20 ◽  
Signal Molecules ◽  
Sensing System ◽  
Serratia Liquefaciens ◽  
Quorum Sensing System

ABSTRACT Serratia liquefaciens MG1 employs the swr quorum-sensing system to control various functions, including production of extracellular enzymes and swarming motility. Here we report the sequencing of the swr flanking DNA regions. We identified a gene upstream of swrR and transcribed in the same direction, designated estA, which encodes an esterase that belongs to family II of lipolytic enzymes. EstA was heterologously expressed in Escherichia coli, and the substrate specificity of the enzyme was determined in crude extracts. With the aid of zymograms visualizing EstA on polyacrylamide gels and by the analysis of a transcriptional fusion of the estA promoter to the promoterless luxAB genes, we showed that expression of the esterase is not regulated by the swr quorum-sensing system. An estA mutant was generated and was found to exhibit growth defects on minimal medium containing Tween 20 or Tween 80 as the sole carbon source. Moreover, we show that the mutant produces greatly reduced amounts of N-acyl-homoserine lactone (AHL) signal molecules on Tween-containing medium compared with the wild type, suggesting that under certain growth conditions EstA may be important for providing the cell with precursors required for AHL biosynthesis.

scholarly journals Identification and Characterization of an N-Acylhomoserine Lactone-Dependent Quorum-Sensing System in Pseudomonas putida Strain IsoF

2002 ◽  
Vol 68 (12) ◽  
pp. 6371-6382 ◽  
Author(s):  
Anette Steidle ◽  
Marie Allesen-Holm ◽  
Kathrin Riedel ◽  
Gabriele Berg ◽  
Michael Givskov ◽  
...  
Keyword(s):  
Amino Acid ◽  
Quorum Sensing ◽  
Pseudomonas Putida ◽  
Gene Cluster ◽  
Intergenic Region ◽  
Phenotypic Traits ◽  
Signal Molecules ◽  
Structural Development ◽  
Sensing System ◽  
Quorum Sensing System

ABSTRACT Recent reports have shown that several strains of Pseudomonas putida produce N-acylhomoserine lactones (AHLs). These signal molecules enable bacteria to coordinately express certain phenotypic traits in a density-dependent manner in a process referred to as quorum sensing. In this study we have cloned a genomic region of the plant growth-promoting P. putida strain IsoF that, when present in trans, provoked induction of a bioluminescent AHL reporter plasmid. Sequence analysis identified a gene cluster consisting of four genes: ppuI and ppuR, whose predicted amino acid sequences are highly similar to proteins of the LuxI-LuxR family, an open reading frame (ORF) located in the intergenic region between ppuI and ppuR with significant homology to rsaL from Pseudomonas aeruginosa, and a gene, designated ppuA, present upstream of ppuR, the deduced amino acid sequence of which shows similarity to long-chain fatty acid coenzyme A ligases from various organisms. Using a transcriptional ppuA::luxAB fusion we demonstrate that expression of ppuA is AHL dependent. Furthermore, transcription of the AHL synthase ppuI is shown to be subject to quorum-sensing regulation, creating a positive feedback loop. Sequencing of the DNA regions flanking the ppu gene cluster indicated that the four genes form an island in the suhB-PA3819 intergenic region of the currently sequenced P. putida strain KT2440. Moreover, we provide evidence that the ppu genes are not present in other AHL-producing P. putida strains, indicating that this gene cluster is so far unique for strain IsoF. While the wild-type strain formed very homogenous biofilms, both a ppuI and a ppuA mutant formed structured biofilms with characteristic microcolonies and water-filled channels. These results suggest that the quorum-sensing system influences biofilm structural development.

Inhibition of Biogenic Amines in Shewanella baltica by Anthocyanins Involving a Quorum Sensing System

2019 ◽  
Vol 82 (4) ◽  
pp. 589-596
Author(s):  
YANBO WANG ◽  
FEIFEI WANG ◽  
XINGYUE BAO ◽  
JIE FENG ◽  
LINGLIN FU
Keyword(s):  
Quorum Sensing ◽  
Transcriptional Analysis ◽  
Large Yellow Croaker ◽  
Sensing System ◽  
Quorum Sensing System ◽  
A Cell ◽  
Culture Extract ◽  
Purple Sweet Potato ◽  
Positive Correlations ◽  
Shewanella Baltica

ABSTRACT Quorum sensing (QS) is a cell density-dependent signaling system responsible for various physiological activities in bacteria. We initially investigated the relation between a QS system and biogenic amine (BA) production in Shewanella baltica, the specific spoilage organism of refrigerated large yellow croaker (Pseudosciaene crocea). In addition, the inhibition effects of anthocyanins from blueberry and purple sweet potato against QS signals and putrescine production were explored. Two kinds of diketopiperazines, cyclo-(l-Pro-l-Leu) and cyclo-(l-Pro-l-Pro), and two kinds of BAs, putrescine and cadaverine, were detected in the culture extract of S. baltica cultivated in sterile large yellow croaker juice, wherein putrescine presented significantly positive correlations with cyclo-(l-Pro-l-Leu) and cyclo-(l-Pro-l-Pro). In addition, anthocyanins at subminimum inhibitory concentration inhibited the production of diketopiperazines and putrescine in S. baltica 23, a strain with strong putrescine production. Furthermore, a transcriptional analysis showed that anthocyanins suppressed the expression of the odc gene in S. baltica, the gene responsible for the production of putrescine from decarboxylation of ornithine. These results established a correlation of the main BA putrescine with the QS system in S. baltica and revealed that anthocyanins could be developed as new QS inhibitors and seafood preservative candidates. HIGHLIGHTS

scholarly journals Role of Quorum Sensing in Sinorhizobium meliloti-Alfalfa Symbiosis

2009 ◽  
Vol 191 (13) ◽  
pp. 4372-4382 ◽  
Author(s):  
Nataliya Gurich ◽  
Juan E. González
Keyword(s):  
Quorum Sensing ◽  
Plant Invasion ◽  
Sinorhizobium Meliloti ◽  
Growth Cycle ◽  
Signal Molecules ◽  
Wild Type ◽  
In Planta ◽  
Cell Functions ◽  
Sensing System ◽  
Quorum Sensing System

ABSTRACT The ExpR/Sin quorum-sensing system of the gram-negative soil bacterium Sinorhizobium meliloti plays an important role in the establishment of symbiosis with its host plant Medicago sativa. A mutant unable to produce autoinducer signal molecules (sinI) is deficient in its ability to invade the host, but paradoxically, a strain lacking the quorum-sensing transcriptional regulator ExpR is as efficient as the wild type. We compared the whole-genome expression profile of the wild-type strain with strains missing one of the quorum-sensing regulatory components to identify genes controlled by the ExpR/Sin system throughout the different phases of the bacterial growth cycle, as well as in planta. Our analyses revealed that ExpR is a highly versatile regulator with a unique ability to show different regulatory capabilities in the presence or absence of an autoinducer. In addition, this study provided us with insight into the plant invasion defect displayed by the autoinducer mutant. We also discovered that the ExpR/Sin quorum-sensing system is repressed after plant invasion. Therefore, quorum sensing plays a crucial role in the regulation of many cell functions that ensures the successful invasion of the host and is inactivated once symbiosis is established.

scholarly journals Determination of quorum sensing system via biosensor strains and virulence factors in fish pathogen Aeromonas hydrophila

2020 ◽  
Vol 37 (1) ◽  
pp. 29-36
Author(s):  
Nurdan Filik ◽  
Ayşegül Kubilay
Keyword(s):  
Quorum Sensing ◽  
Virulence Factors ◽  
Aeromonas Hydrophila ◽  
Homoserine Lactone ◽  
Signaling Molecules ◽  
Signal Molecules ◽  
Signaling Molecule ◽  
Sensing System ◽  
Quorum Sensing System

Quorum Sensing is a system that produces critical virulence factors, virulent get bacteria and manages the disease as a result, and when they realize that the bacteria reach the majority they want by enabling them to communicate with the signal molecules themselves. In this study, Quorum Sensing system of Aeromonas hydrophila (2 strains) which is the causative agent of fish infection Motile Aeromonas Septicemia (MAS) disease was studied. In the strains, primarily the production of N-butanoyl-L-homoserine lactone (BHL) and N-(3-octododecanoyl)-L-homoserine lactone (OdDHL) signaling molecules was investigated via Chromobacterium violaceum CV026 and Agrobacterium tumafeciens NT1 biosensor strains. A. hydrophila produced BHL signaling molecule in assay committed using C. violaceum CV026 strain, producing OdDHL signaling molecule in assay committed using A. tumefaciens NT1 strain. A. hydrophila was investigated as phenotypically by the detection of BHL and OdDHL signaling molecules and in the presence of virulence factors controlled by quorum sensing system such as ramnolipid, elastase, protease, amylase, hemolysis production dependent on these molecules. The ramnolipid, protease, amylase and hemolysis activities of A. hydrophila strains were found to be positive. A. hydrophila has less elastase activity than Pseudomonas aeruginosa PAO1 control strain. Research has emphasizing A. hydrophila strains are within a population and that they have a of quorum sensing system, shown that they act collectively that determined they produces dangerous virulence factors that cause disease in fish.

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