Team:Grenoble/Projet/Design/quorum

From 2011.igem.org

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<h2>The Quorum Sensing</h2>
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By coupling Toggle Switch with Quorum Sensing genes, the switch in a pathway defines a specific behavior: receiving or secretory bacteria.
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<a href="https://static.igem.org/mediawiki/2011/a/a3/Toggle_Switch.png"><img src="https://static.igem.org/mediawiki/2011/a/a3/Toggle_Switch.png"  width="300px"></a>
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<a href="https://static.igem.org/mediawiki/2011/2/27/Reseau_regulation_QS_receiving.png"><img src="https://static.igem.org/mediawiki/2011/2/27/Reseau_regulation_QS_receiving.png"  width="300px"></a>
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The Toggle Switch allows our bacterial strain to switch between one of the two different behaviors (Receiver or Secretor) depending on the predominant concentration in the external medium: IPTG or Hg.
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If MerR pathway is activated, CinI proteins are expressed providing to the bacteria the ability to release in the medium AHL molecules.
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We take into account two proteins repressing (CinI/CinR) each other's expression (pLac/pMerT). We create the fundaments of a toggle system that can switch when using two inducers in the medium: IPTG and Hg.
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Whereas if LacI pathway is activated, CinR proteins are expressed in the inner bacteria. Thus, these bacteria will be able to received Quorum Sensing molecule, AHL.
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<a href="https://static.igem.org/mediawiki/2011/8/8b/Reseau_regulation_QS_receiv.png"><img src="https://static.igem.org/mediawiki/2011/8/8b/Reseau_regulation_QS_receiv.png"  width="300px"></a>
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Initially, both genes, MerR and LacI, are expressed repressing each other promoters: pLac and pMerT.
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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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<a href="https://static.igem.org/mediawiki/2011/4/43/Toggle_Switch_predominance1.png"><img src="https://static.igem.org/mediawiki/2011/4/43/Toggle_Switch_predominance1.png"  width="300px"></a>
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On the plate where Hg concentration is the uppermost, this inducer will remove the repression exerted on pMerT promoter. So, the LacI proteins will be expressed and by repressing the promoter pLac, LacI proteins are shutting down the other way of the toggle.
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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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Revision as of 02:55, 22 September 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 secretory bacteria.

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

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

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.

Inversely, where IPTG concentration is the uppermost, the other way will be activated.

Coloration

The two populations encounter each other at the “interface”. 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 to up-regulate the promoter pCin. Allowing the expression of the three Lycopene synthesise enzymes coding crtB, crtE, crtI. These three enzymes produce the lycopene so we can observe a red stripe at the interface between receiving and senders.

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