Team:Grenoble/Projet/Design/quorum

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<h3>In a few words</h3>
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<h1 >The Quorum Sensing</h1>
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Quorum sensing is an important phase of physiological development of the bacteria. It’s the communication signal between bacteria carried by a signalling molecule. All bacteria can produce or detect the quorum sensing molecule. Quorum sensing involves a secreted molecule which allows the number of bacteria to be known and give a logical response to a high level of population. Frequently the Quorum sensing is the signal to stop the growth, activate the virulence state, or activate luminescence.
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The quorum sensing (QS) detection is links to his concentration in the medium, so when the bacteria are in low numbers the QS molecule is at a low concentration and does not activate the response. But when the bacteria become too abundant the QS concentration is higher and activates the response.
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By coupling Toggle Switch with Quorum Sensing genes, the switch in a pathway defines a specific behavior: receiving or sending bacteria.
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  <td><p>Beginning of growth phase, cells are few, so the production of QS is very low, no response activity.
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<a href="http://2011..org/wiki/images/4/4f/TS_QS_send.png"><img src="https://static.igem.org/mediawiki/2011/4/4f/TS_QS_send.png"  width="450px"></a>
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If LacI pathway is activated, CinI proteins are expressed providing to the bacteria the ability to release in the medium Quorum Sensing molecules, AHL.
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  <td><p>Middle Growth phase bacteria are many but not enough for activate QS response, the concentration in QS is not high enough.</p></td>
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<a href="https://static.igem.org/mediawiki/2011/3/37/TS_QS_recei.png"><img src="https://static.igem.org/mediawiki/2011/3/37/TS_QS_recei.png"  width="450px"></a>
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Whereas if MerR pathway is activated, CinR proteins are expressed in the inner bacteria. Thus, these bacteria will be able to received AHL molecule.
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Put together, both bacterial behaviors allow the formation of AHL/CinR complex in the inner receiving bacteria.
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  <td><p>In Stationary phase, bacteria are very concentrated so the production of QS is maximal and the lack of space up the concentration of QS. Both phenomena are sufficient to activate a response.</p></td>
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<a href="https://static.igem.org/mediawiki/2011/3/36/Coloration_toi_toi_mon_toi.png"><img src="https://static.igem.org/mediawiki/2011/3/36/Coloration_toi_toi_mon_toi.png"  width="350px"></a>
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We make use of this complex to visualize the boundary between the two different bacterial behavior areas.
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<h3>Biologically, what is happening ?</h3>
 
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The Quorum sensing system is composed of three elements: an enzyme, a secreted molecule and a receptor.
 
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A bacterium synthesises this Quorum sensing enzyme which in turn synthesizes the quorum sensing molecule. This molecule diffuses within and outside the cell (around 1mm/h), and can enter inside the issuing bacterium or any other bacteria in its neighbourhood. The QS molecule interacts with its receptor protein. The complex binds to DNA and activates or represses genes generating the appropriate response.
 
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<h2>Coloration</h2>
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The two behaviors encounter each other at the boundary. At this location cells emit AHL closely to receivers.
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The AHL molecules enter into the receiving cells and bind receptor protein to form a complex which up-regulates the promoter pCin. Thus, the expression of the three Lycopene synthesise enzymes is allowed. These three enzymes (crtB, crtE, crtI) produce the lycopene pigment so we can observe a red stripe at the interface between receiving and senders.
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<img height="300" src="https://static.igem.org/mediawiki/2011/1/1b/Details_lycopene.png"/>
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Both of these parts of the genetic network are modelled in the <a href="https://2011.igem.org/Team:Grenoble/Projet/Modelling/Deterministic#Our_EquationsQS">same module</a>.
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Coupled with the toggle switch module, this model gives us the behavior of <a href="https://2011.igem.org/Team:Grenoble/Projet/Results/Toggle#QS">quorum sensing production and complexation</a>.
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From which we can deduce some <a href="https://2011.igem.org/Team:Grenoble/Projet/Results/Device#Optimization">optimizations</a> for our device.
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<H3>Importance of Quorum Sensing for 'Le Projet'  ?</H3>
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The Quorum sensing (QS) is an important part of our project because ours cells have the same genetic network, but they have the ability to choose a pathway and become sender cell or receptor cell of quorum sensing (QS), depending the IPTG and Anhydro-tetracyclin (ATC) concentration in the medium. Remember bacteria are fixed on a plate, at one side bacteria are in a way and at the opposite side they choose the other way. So at the interface of these two populations, we are in a cryptic place, the concentration are in a specific ratio and bacteria have the same probability to choose one of the both ways. We obtain closely, a mix of QS senders and QS receptors. 
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The receptor cells receives quorum sensing molecules from the senders, the presence of receptors proteins (in receptor cells) and QS molecules, permit by complexing both to activate the transcription of the pCin promoter which regulate the synthesis of a orange pigment named lycopen. So at the interface of populations we can observed a red line corresponding to a defined concentration in anhydro-tetracyclin(ATC). 
 
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The interface location move on the plate depending of the concentration ratio of IPTG and ATC.
 
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    <option value="#Content">General network</option>
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                                    <option value="/Design/toggle" >The Toggle Switch</option>
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                            <optgroup label="Quorum Sensing">
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                                    <option value="/Design/quorum"  selected="selected">The Quorum Sensing</option>
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                            <optgroup label="Post Transcriptional Regulation">
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    <option value="/regulation">A Post-Transcriptional Regulation System</option>
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Latest revision as of 02:31, 29 October 2011

Grenoble 2011, Mercuro-Coli iGEM


The Quorum Sensing

By coupling Toggle Switch with Quorum Sensing genes, the switch in a pathway defines a specific behavior: receiving or sending bacteria.

If LacI pathway is activated, CinI proteins are expressed providing to the bacteria the ability to release in the medium Quorum Sensing molecules, AHL.

Whereas if MerR pathway is activated, CinR proteins are expressed in the inner bacteria. Thus, these bacteria will be able to received AHL molecule.



Put together, both bacterial behaviors allow the formation of AHL/CinR complex in the inner receiving bacteria.



We make use of this complex to visualize the boundary between the two different bacterial behavior areas.

Coloration

The two behaviors encounter each other at the boundary. At this location cells emit AHL closely to receivers.

The AHL molecules enter into the receiving cells and bind receptor protein to form a complex which up-regulates the promoter pCin. Thus, the expression of the three Lycopene synthesise enzymes is allowed. These three enzymes (crtB, crtE, crtI) produce the lycopene pigment so we can observe a red stripe at the interface between receiving and senders.

Both of these parts of the genetic network are modelled in the same module. Coupled with the toggle switch module, this model gives us the behavior of quorum sensing production and complexation. From which we can deduce some optimizations for our device.

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