Team:Toulouse/Project/Spreading

From 2014.igem.org

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<p class="title1">Survival in the environment</p>
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<p class="texte">SubtiTree will live in sap tree, thus we use one endophyte <I>Bacillus subtilis</I> strain. In order to contain our bacteria in this area during a short period of time, we modified some of its survival characteristics.First of all, the control of synthetic bacterium location concerned us,that is why we border it inside the plane tree. Sap tree is known to contain a certain quantity of proline which could allow bacterial growth whereas the soil is composed by only trace of this amino acid. Thus, we decided to delete the proline production pathway to make an auxotrophic bacterium for this amino acid.
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</p>
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<p class="title1">Preventing sporulation of <i>B. subtilis</i></p>
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<p class="texte">
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It is known that endophyte bacteria must sporulate to survive to winter. In order to limit the spreading of our bacterium, we decided to limit its lifespan to only one season. The bacteria should be injected in spring, grow during the summer and finally should be inactivated in fall.<br\>
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<i>Bacillus subtilis</i> is a sporing bacterium : sporulation enable the microorganism to handle very harsh conditions and to spread tree to tree. Indeed, a spore is a very resistant form that is adapted for unfavorable conditions and for dispersal.<br/>
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To keep the control on the development of SubtiTree, our strain should therefore be non-sporinghus. We chose a <I>B.subtilis</I> strain without late genes of sporulation. Thus, after a season of treatment, the sape become less nutritious, the temperature is low and the engineered bacterium cannot survive the following winter.<br/>
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In addition, deleting all the engineered bacterial community every year puts a brake on the evolution due to random mutation, thus it allows to keep control on the genetic constructions.
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</p>
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<p class="texte">These two first characteristics of SubtiTree show that it is an annual bacterium, which can only grow in sap tree. By combinind them, they prevent any long term colonization of an ecological niche by SubtiTree against wild type bacteria. These prevent a long term effect.</p>
<p class="title1">Using a glutamin auxotroph <i>B. subtilis</i> strain</p>
<p class="title1">Using a glutamin auxotroph <i>B. subtilis</i> strain</p>
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Thus, if the bacterium is in the sap, it can grow normally without any deficiency since it uses the glutamine present in the sap ; but if it escapes from the tree and <i>a fortiori</i> from the sap, it will not be able to survive for a long time. Indeed, glutamine is found in low quantities in the ground. This system should guarantee that the bacterium develops only in the tree and not elsewhere in the surroundings of the tree.<br/>  
Thus, if the bacterium is in the sap, it can grow normally without any deficiency since it uses the glutamine present in the sap ; but if it escapes from the tree and <i>a fortiori</i> from the sap, it will not be able to survive for a long time. Indeed, glutamine is found in low quantities in the ground. This system should guarantee that the bacterium develops only in the tree and not elsewhere in the surroundings of the tree.<br/>  
Auxotroph <i>B.sutbilis</i> strains already exist and are indexed in databases as BGSC (Bacillus Genetic Stock Center), therefore it is easy to find.   
Auxotroph <i>B.sutbilis</i> strains already exist and are indexed in databases as BGSC (Bacillus Genetic Stock Center), therefore it is easy to find.   
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</p>
 
-
 
-
<p class="title1">Preventing sporulation of <i>B. subtilis</i></p>
 
-
<p class="texte">
 
-
In order to limit the spreading of our bacterium, we decided to limit its lifespan to only one season. The bacteria should be injected in spring, grow during the summer and finally should be inactivated in fall.<br\>
 
-
<i>Bacillus subtilis</i> is a sporing bacterium : sporulation enable the microorganism to handle very harsh conditions and to spread tree to tree. Indeed, a spore is a very resistant form that is adapted for unfavorable conditions and for dispersal.<br/>
 
-
To keep the control on the development of SubtiTree, our strain should therefore be non-sporing. Thus, after a season of treatment, the sape become less nutritious, the temperature is low and the engineered bacterium cannot survive the following winter.<br/>
 
-
In addition, deleting all the engineered bacterial community every year puts a brake on the evolution due to random mutation, thus it allows to keep control on the genetic constructions.
 
</p>
</p>
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</p>
</p>
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<p class="texte"><I><CENTER>Survival in the environment</I></CENTER></p>
 
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<p class="texte">SubtiTree will live in sap tree, thus we use one endophyte <I>Bacillus subtilis</I> strain. In order to contain our bacteria in this area during a short period of time, we modified some of its survival characteristics. 
 
-
First of all, the control of synthetic bacterium location concerned us,that is why we border it inside the plane tree. Sap tree is known to contain a certain quantity of proline which could allow bacterial growth whereas the soil is composed by only trace of this amino acid. Thus, we decided to delete the proline production pathway to make an auxotrophic bacterium for this amino acid.
 
-
</p>
 
-
 
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<p class="texte">Secondly, SubtiTree is conceived as an annual bacterium to avoid any kind of mutations. It is known that endophyte bacteria must sporulate to survive to winter. Thus, we chose a <I>B.subtilis</I> strain without late genes of sporulation. So SubtiTree is a non-sporing bacterium, which means that under stress conditions (cold temperature, food lack …) or outside the sap, the bacterium will not resist and die.</p>
 
-
 
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<p class="texte">These two characteristics of SubtiTree show that it is an annual bacterium, which can only grow in sap tree. By combinind them, they prevent any long term colonization of an ecological niche by SubtiTree against wild type bacteria. These prevent a long term effect.</p>
 
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<p class="texte"><I><CENTER>Gene transfer</I></CENTER></p>
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<p class="title1">Gene transfer</p>
<p class="texte"> While we were trying to respond to bacterial spreading problem, at the same time we wondered about horizontal gene transfer. The transmission of genes from our synthetic bacterium to wild type bacteria could be blocked with two modifications.   
<p class="texte"> While we were trying to respond to bacterial spreading problem, at the same time we wondered about horizontal gene transfer. The transmission of genes from our synthetic bacterium to wild type bacteria could be blocked with two modifications.   

Revision as of 10:02, 13 October 2014