Team:Dundee/Project/pqs
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<div class="jumbotron"> | <div class="jumbotron"> | ||
- | <h1>The <i>Pseudomonas</i> Quinolone Signal (PQS) | + | <h1><font size="14">The <i>Pseudomonas</i> Quinolone Signal (PQS) Sensing System</font></h1> |
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<p class="lead"></p> | <p class="lead"></p> | ||
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<ul class="nav list-group affix"> | <ul class="nav list-group affix"> | ||
- | <li class="list-group-item"><a href="#0" class="">Initial | + | <li class="list-group-item"><a href="#0" class="">Initial Planning and Cloning Strategy</a> |
</li> | </li> | ||
- | <li class="list-group-item"><a href="#1" class="">Building the PQS | + | <li class="list-group-item"><a href="#1" class="">Building the PQS Sensor</a> |
</li> | </li> | ||
<li class="list-group-item"><a href="#2" class="">Characterisation</a> | <li class="list-group-item"><a href="#2" class="">Characterisation</a> | ||
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- | + | <h2 id="0">Initial Planning and Cloning Strategy</h2> | |
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- | + | <img class= "pull-left img-responsive shrink" src="https://static.igem.org/mediawiki/2014/4/46/Pqssss.png"width="288" height="380" /> | |
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<p> | <p> | ||
- | <i>Pseudomonas</i>quinolone signal (2-heptyl-3-hydroxy-4-quinolone) is a quorum-sensing molecule produced by <i>Pseudomonas aeruginosa</i>, which regulates the expression of genes involved in biofilm development and virulence | + | <i>Pseudomonas</i> quinolone signal (2-heptyl-3-hydroxy-4-quinolone) is a quorum-sensing molecule produced by <i>Pseudomonas aeruginosa</i>, which regulates the expression of genes involved in biofilm development and virulence<sup>1</sup>. Expression of these traits is mediated through the LysR-type transcriptional regulator, <a href="http://parts.igem.org/Part:BBa_K1157001">PqsR</a>. Bioinformatic analysis of the PqsR sequence predicted that it is a soluble protein. Fractionation experiments of <i>P. aeruginosa</i> cells has shown that PqsR is primarily associated with the inner membrane<sup>2</sup>. It is not clear however, whether this is through protein-lipid or protein-protein interactions with membrane lipids or with a yet unidentified integral inner membrane protein, respectively. In the presence of PQS, PqsR interacts with the promoter region of the <a href="http://parts.igem.org/Part:BBa_K1315001"><i>pqsA</i></a> operon, allowing transcription of the downstream genes<sup>3</sup>. We have engineered<i> E. coli</i> to express this signal transduction system for the detection of PQS (as shown in Fig 1), with a promoter-less <a href="http://parts.igem.org/Part:BBa_K562011"> mCherry</a> coding gene fused to the <i>pqsA</i> promoter to give a fluorescent output. |
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- | <h2 id="1">Building the PQS | + | <h2 id="1">Building the PQS Sensor</h2> |
<div class="row"> | <div class="row"> | ||
<div class="col-xs-12"> | <div class="col-xs-12"> | ||
<p> | <p> | ||
- | Chromosomal DNA from <i>Pseudomonas | + | Chromosomal DNA from <i>Pseudomonas aeruginosa</i> PA01 strain was kindly gifted to us by Drs Robert Ryan and Shi-Qi An from the Division of Molecular Microbiology in the College of Life sciences at the University of Dundee. This was used as a template for the amplification of the <i>pqsA</i> promoter gene. |
+ | <br> | ||
+ | <br> | ||
- | The <i>pqsA</i> promoter region was cloned into the pSB1C3 plasmid ( | + | The <i>pqsA</i> promoter region was cloned into the pSB1C3 plasmid (BioBrick <a href="http://parts.igem.org/Part:BBa_K1315001">BBa_K1315001</a>), and was then subcloned into pBluescript. Promoterless mCherry was amplified (template used: <a href="http://parts.igem.org/Part:BBa_K562011"> BBa_K562012</a>), and was cloned into pBluescript downstream of the <i>pqsA</i> promoter. The P<i><sub>pqsA</sub></i>-mCherry construct was then subcloned into pUniprom. A schematic of our completed construct can be seen in Fig 2. |
- | + | <br> | |
- | The pqsR gene (present in <a href="http://parts.igem.org/Part: | + | <br> |
- | influenza virus haemagglutinin (HA) tag coding sequence, which can be detected | + | The <i>pqsR</i> gene (present in <a href="http://parts.igem.org/Part:BBa_K1157001">BBa_K1315001</a>) which was designed and cloned by Lin Ang Chieh from iGEM13-NTU-Taida was used as a template for the amplification of <i>pqsR</i> with an |
+ | influenza virus haemagglutinin (HA) tag coding sequence, which can be detected by commercially available antibodies. The HA-tag was fused to the C-terminus of the protein to allow visualisation by immunohistochemistry. | ||
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+ | <img class= "img-responsive" src="https://static.igem.org/mediawiki/2014/8/84/Pqs1boold.png"width="600" height="152" /> | ||
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- | Initially, western blots were undertaken to test for the production of PqsR-HA. We transformed our plasmid encoding PqsR-HA into <i>E. coli </i>strain MC1061 and blotted for | + | Initially, western blots were undertaken to test for the production of PqsR-HA. We transformed our plasmid encoding PqsR-HA into <i>E. coli </i>strain MC1061 and blotted for recombinantely expressed protein. An overnight culture of the cells was lysed and proteins separated by SDS-PAGE in a 12% acrylamide gel. Anti-HA antibodies linked to horseradish peroxidase were used for detection of PqsR. Fig 3A shows the expression of PqsR within our system. |
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+ | <img class= "img-responsive" src="https://static.igem.org/mediawiki/2014/8/8f/3pqs3.png"/> | ||
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- | As shown in Fig 3, successful production of PqsR-HA (expected mass 38 kDa) was observed. With the PqsR regulator being produced we could begin to test for a response to PQS. To test how the system would respond to PQS, cells containing the construct were cultured in LB medium and spiked with synthetic PQS in DMSO at concentrations of | + | As shown in Fig 3, successful production of PqsR-HA (expected mass 38 kDa) was observed. With the PqsR regulator being produced we could begin to test for a response to PQS. To test how the system would respond to PQS, cells containing the construct were cultured in LB medium and spiked with synthetic PQS (in 100% DMSO) at finals concentrations of 50 and 500 μM. A western blot with anti-mCherry antibodies was performed on the treated cells alongside a control (DMSO). Two further controls - MC1061 cells harbouring the empty pUniprom vector (mCherry negative control) and <a href="http://parts.igem.org/Part:BBa_K562011"> BBa_K562011</a> (mCherry positive control) were also included. |
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- | < | + | <img class="center img-responsive" src="https://static.igem.org/mediawiki/2014/e/ec/4pqs4.png" /> |
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- | As shown in Fig 4 incubation of cells with synthetic PQS, did not induce expression of mCherry. It is not clear why the biosensor did not respond. One possibility we considered is that | + | <br> |
+ | <br> | ||
+ | As shown in Fig 4, incubation of cells with synthetic PQS, did not induce expression of mCherry. It is not clear why the biosensor did not respond. One possibility we considered is that PqsR is not correctly localized to the membrane in <i>E. coli</i>. We therefore fractionated <i>E. coli</i> cells containing PqsR-HA into soluble and membrane fractions. However, as shown in Fig 5, all of the detectable PqsR-HA was found in the membranes as it is in the native organism. | ||
</p> | </p> | ||
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- | + | <img class="center img-responsive" src="https://static.igem.org/mediawiki/2014/a/a3/5pqs5.png"/> | |
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- | src="https://static.igem.org/mediawiki/2014/ | + | </div> |
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- | We discussed the | + | <br> |
+ | <br> | ||
+ | We discussed the results of the PQS biosensor extensively with the | ||
+ | <a href="https://2014.igem.org/Team:Dundee/Modeling/pqs">modelling team</a>. They suggested increasing the number of promoters (by at least 10-fold). This should allow for sufficient production of mCherry, which can then be detected. We are in the process of building this new expression system. | ||
+ | </p> | ||
+ | <br> | ||
+ | <br> | ||
+ | The following parts were deposited as BioBricks: | ||
+ | <br> | ||
+ | <br> | ||
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- | <td> | + | <td><i>pqsA</i></td> |
<td>Promoter</td> | <td>Promoter</td> | ||
<td><a href="http://parts.igem.org/Part:BBa_K1315001">BBa_K1315001</a></td> | <td><a href="http://parts.igem.org/Part:BBa_K1315001">BBa_K1315001</a></td> | ||
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+ | <div id="ref"> | ||
+ | <h3>References</h3> | ||
+ | <p> | ||
+ | <sup>1</sup>Reen, F.J. et al. (2011) FEMS Microbiol Ecol 77, 413-428. <br> | ||
+ | <sup>2</sup>Cao, H. et al. (2001) Proc Natl Acad Sci USA 98, 14613–14618.<br> | ||
+ | <sup>3</sup>Dekimpe, V. et al. (2009) Microbiology 155, 712-723.</font> | ||
+ | </p> | ||
+ | </div> | ||
+ | </div> | ||
+ | </div> | ||
+ | </div> | ||
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- | <a href="" class="btn btn-default toLesson">Previous | + | <a href="Aims" class="btn btn-default toLesson">Previous Lesson: The Lung Ranger</a> |
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- | <a href=" | + | <a href="PAI-1" class="btn btn-default toLesson">Next Lesson: PAI-1 Sensor</a> |
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Latest revision as of 22:20, 17 October 2014
The Pseudomonas Quinolone Signal (PQS) Sensing System
Initial Planning and Cloning Strategy
![](https://static.igem.org/mediawiki/2014/4/46/Pqssss.png)
Pseudomonas quinolone signal (2-heptyl-3-hydroxy-4-quinolone) is a quorum-sensing molecule produced by Pseudomonas aeruginosa, which regulates the expression of genes involved in biofilm development and virulence1. Expression of these traits is mediated through the LysR-type transcriptional regulator, PqsR. Bioinformatic analysis of the PqsR sequence predicted that it is a soluble protein. Fractionation experiments of P. aeruginosa cells has shown that PqsR is primarily associated with the inner membrane2. It is not clear however, whether this is through protein-lipid or protein-protein interactions with membrane lipids or with a yet unidentified integral inner membrane protein, respectively. In the presence of PQS, PqsR interacts with the promoter region of the pqsA operon, allowing transcription of the downstream genes3. We have engineered E. coli to express this signal transduction system for the detection of PQS (as shown in Fig 1), with a promoter-less mCherry coding gene fused to the pqsA promoter to give a fluorescent output.
Building the PQS Sensor
Chromosomal DNA from Pseudomonas aeruginosa PA01 strain was kindly gifted to us by Drs Robert Ryan and Shi-Qi An from the Division of Molecular Microbiology in the College of Life sciences at the University of Dundee. This was used as a template for the amplification of the pqsA promoter gene.
The pqsA promoter region was cloned into the pSB1C3 plasmid (BioBrick BBa_K1315001), and was then subcloned into pBluescript. Promoterless mCherry was amplified (template used: BBa_K562012), and was cloned into pBluescript downstream of the pqsA promoter. The PpqsA-mCherry construct was then subcloned into pUniprom. A schematic of our completed construct can be seen in Fig 2.
The pqsR gene (present in BBa_K1315001) which was designed and cloned by Lin Ang Chieh from iGEM13-NTU-Taida was used as a template for the amplification of pqsR with an
influenza virus haemagglutinin (HA) tag coding sequence, which can be detected by commercially available antibodies. The HA-tag was fused to the C-terminus of the protein to allow visualisation by immunohistochemistry.
![](https://static.igem.org/mediawiki/2014/8/84/Pqs1boold.png)
The completed construct was transformed into E. coli strain MC1061 as a chassis for our biosensor.
Characterisation
Initially, western blots were undertaken to test for the production of PqsR-HA. We transformed our plasmid encoding PqsR-HA into E. coli strain MC1061 and blotted for recombinantely expressed protein. An overnight culture of the cells was lysed and proteins separated by SDS-PAGE in a 12% acrylamide gel. Anti-HA antibodies linked to horseradish peroxidase were used for detection of PqsR. Fig 3A shows the expression of PqsR within our system.
![](https://static.igem.org/mediawiki/2014/8/8f/3pqs3.png)
As shown in Fig 3, successful production of PqsR-HA (expected mass 38 kDa) was observed. With the PqsR regulator being produced we could begin to test for a response to PQS. To test how the system would respond to PQS, cells containing the construct were cultured in LB medium and spiked with synthetic PQS (in 100% DMSO) at finals concentrations of 50 and 500 μM. A western blot with anti-mCherry antibodies was performed on the treated cells alongside a control (DMSO). Two further controls - MC1061 cells harbouring the empty pUniprom vector (mCherry negative control) and BBa_K562011 (mCherry positive control) were also included.
![](https://static.igem.org/mediawiki/2014/e/ec/4pqs4.png)
As shown in Fig 4, incubation of cells with synthetic PQS, did not induce expression of mCherry. It is not clear why the biosensor did not respond. One possibility we considered is that PqsR is not correctly localized to the membrane in E. coli. We therefore fractionated E. coli cells containing PqsR-HA into soluble and membrane fractions. However, as shown in Fig 5, all of the detectable PqsR-HA was found in the membranes as it is in the native organism.
![](https://static.igem.org/mediawiki/2014/a/a3/5pqs5.png)
We discussed the results of the PQS biosensor extensively with the
modelling team. They suggested increasing the number of promoters (by at least 10-fold). This should allow for sufficient production of mCherry, which can then be detected. We are in the process of building this new expression system.
The following parts were deposited as BioBricks:
Part | Description | Registry |
---|---|---|
pqsA | Promoter | BBa_K1315001 |
References
1Reen, F.J. et al. (2011) FEMS Microbiol Ecol 77, 413-428.
2Cao, H. et al. (2001) Proc Natl Acad Sci USA 98, 14613–14618.
3Dekimpe, V. et al. (2009) Microbiology 155, 712-723.