Team:Toulouse/Project/Chemotaxis

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<center><img style="width:420px; " src="http://parts.igem.org/wiki/images/e/e9/Recap_chemotax.jpg"></center>
<p class="title1">What is chemotaxis?</p>
<p class="title1">What is chemotaxis?</p>
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Chemotaxis is a bacterial function which allows bacteria to move according a concentration gradient. With this system bacteria can find better place to grow by swimming toward higher concentrations of molecules, such as nutritional molecules like sugar, amino acid, vitamins...
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Chemotaxis is a bacterial function which allows to move according to a concentration gradient. With this system bacteria can find a better place to grow by swimming toward higher concentrations of molecules, such as nutritional molecules like sugar, amino acid, vitamins...Chemotactic-signal transducers respond to changes in the concentration of attractants and repellents in the environment, transduce a signal from the outside to the inside of the cell, and facilitate sensory adaptation through the variation of the level of methylation.  
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In our case, chemotaxis is used as a way to detect and approach fungus. Indeed during its growth, fungi release N-acetylglucosamine, a monomer of chitin which is specific to fungal presence. Thus, there is a gradient of N- acetylglucosamine around fungi.</p>
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<center><img style="width:420px; " src="http://parts.igem.org/wiki/images/e/e9/Recap_chemotax.jpg"></center>
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In our case, chemotaxis is used as a way to detect and approach fungi. Indeed during its growth, fungi release N-acetylglucosamine (NAG), the basic unit of chitin which composed its cell wall. Thus, the concentration of N-acetylglucosamine is getting more important around fungi.</p>
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Unfortunately <i>Bacillus subtilis</i> is not able to detect such gradient, but <i>Bacillus</i> is able to detect and to move towards sugar like glucose thanks a glucose specific receptor, VcpA. But other bacteria can detect these kind of molecule, for example <i>Vibrio cholerae</i>, which has a specific receptor for N- acetylglucosamine, VCD.</p>
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It is well known that  <i>Bacillus subtilis</i> is able to detect and to shift towards glucose thanks to the Methyl-accepting chemotaxis protein, called <b> McpA </b>. <br>
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Some bacteria are attracted by NAG, like <i>Vibrio cholerae</i> which has a N-acetylglucosamine regulated methyl-accepting chemotaxis protein, henceforth called with the simple name of<b> VCD</b>.</p>
<center><img SRC="http://2014.igem.org/wiki/images/c/cf/Schema_chemotaxis.png" alt="schema"></center>
<center><img SRC="http://2014.igem.org/wiki/images/c/cf/Schema_chemotaxis.png" alt="schema"></center>
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Therefore, our idea is pretty simple, we switch glucose specificity by N-acetylglucosamine specificity. So we need to modify the extracellular part of VcpA, the part which is responsible of the specificity, by the extracellular part of a N-acetylglucosamine receptor, VCD.</p>
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Therefore, our idea is to switch the natural glucose specificity of <i>B. subtilis</i> by a NAG specificity. To achieve this, we need to change the extracellular domain of McpA, the domain responsible for the specificity, by the extracellular domain of VCD.
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The whole sequence has been designed <i>in silico</i> and codon optimized for the transcription in <i>Bacillus subtilis</i> before its synthesis.</p>
<center><img SRC="http://2014.igem.org/wiki/images/c/cf/Gene_chemotaxis.png" alt="gene construct"></center>
<center><img SRC="http://2014.igem.org/wiki/images/c/cf/Gene_chemotaxis.png" alt="gene construct"></center>

Revision as of 19:52, 14 October 2014