Team:Toulouse/Project/Spreading

From 2014.igem.org

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<p class="title1">Gene transfer: toxin-antitoxin system</p>
<p class="title1">Gene transfer: toxin-antitoxin system</p>
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<p class="texte">We also wondered about horizontal genes transfer. The goal of this module is to prevent horizontal transfers between bacteria. Indeed, it is necessary to avoid any exchange of genetic material between wild type organisms and optimized organisms: it could be dangerous because of mutations, and considering ethics, it seems to be essential to avoid the spreading of synthetic genes.
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<p class="texte">We also wondered about horizontal genes transfer. The goal of this module is to prevent horizontal transfers between bacteria and any exchange of synthetic genetic material that could be dangerous between wild type organisms and optimized organisms.
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<br>Considering this issue, we thought about a system to avoid such transfers: a toxin-antitoxin module. It involves the addition of two genes to the bacterium: a gene encoding for a toxin (for example <i>tse2</i>) and a gene encoding for the antitoxin (<i>tsi1</i>), placing them in an opposite way on the genome. The large space between them prevents simultaneous transfers: if the optimized bacterium transfers the gene encoding for the toxin, the probability that the gene encoding for the antitoxin may be transferred simultaneously is really low since they are located far away from each other.<br/>
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<br>We thought about a system limiting such transfers: a toxin-antitoxin module. It involves the addition of two genes to the bacterium: a gene encoding for a toxin (for example <i>tse2</i>) and a gene encoding for the antitoxin (<i>tsi1</i>), placing them in an opposite way on the genome. The large space between them prevents simultaneous transfers: if the optimized bacterium transfers the gene encoding for the toxin, the probability that the gene encoding for the antitoxin may be transferred simultaneously is really low since they are located far away from each other.<br/>
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Therefore, if the host bacterium receives the gene encoding for the toxin, it will be unable to survive since it will not have the antitoxin. If it receives the antitoxin only, it will not be useful for the bacterium, and will not affect it.<br/>
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Therefore, if anther host bacterium receives the gene encoding for the toxin, it will be unable to survive since it will not possess the antitoxin. If it receives the antitoxin only, it will not be useful for the bacterium, and will not affect it.<br/>
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To sum up, since a simultaneous transfer is dimly probable, the bacterium will either die because of the toxin or live while expressing the antitoxin.  
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In summary, since a simultaneous transfer is dimly probable, the bacterium will either die because of the toxin or live while expressing the antitoxin.  
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<p class="texte">Our synthetic genes are not the only problem in the design of SubtiTree. One of the side effects of our cloning method is the persistence of antibiotic resistance genes. This is incompatible with the introduction of SubtiTree in the environment. It is possible to delete this resistance in chromosome. To conclude, the spreading limitation shown previously makes the use of SubtiTree acceptable in the environment.  
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<p class="texte">Our synthetic genes are not the only problem in the design of SubtiTree. One of the side effects of our cloning method is the persistence of antibiotic resistance genes. This is incompatible with the introduction of SubtiTree in the environment. It is possible to delete this resistance in chromosome.
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While we have not constructed yet these modules, we definitely think that the measures that we designed should render the use of SubtiTree acceptable in the environment.
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<p class="title1">Using integrative plasmids</p>
<p class="title1">Using integrative plasmids</p>
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<p class="texte">
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All our constructions are carried by integrative plasmids. Consequently, our different genetic modules would be integrated into the bacterium genome. The integration in the genome is more stable as the constructions are less likely to be transferred to other microorganisms. In addition to that, the expression of our genetic modules would not be dependent on a selective pressure, allowing a high level of transcription <i>in planta</i>.  
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All our constructions are carried by integrative plasmids. Consequently, our different genetic modules should be integrated into the bacterium genome. The integration in the genome is more stable as the constructions are less likely to be transferred to other microorganisms. In addition to that, the expression of our genetic modules would not be dependent on a selective pressure, allowing a high level of transcription <i>in planta</i>.  
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Revision as of 16:05, 16 October 2014