Team:Toulouse/Project/Chemotaxis

What is chemotaxis?

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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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.

It is well known that Bacillus subtilis is able to detect and to shift towards glucose thanks to the Methyl-accepting chemotaxis protein, called McpA .
Some bacteria are attracted by NAG, like Vibrio cholerae which has a N-acetylglucosamine regulated methyl-accepting chemotaxis protein, henceforth called with the simple name of VCD.

Therefore, our idea is to switch the natural glucose specificity of B. subtilis 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. The whole sequence has been designed in silico and codon optimized for the transcription in Bacillus subtilis before its synthesis.

References

• K. Meibom,L. Xibing, A. Nielsen, CY. Wu, S. Roseman and G. Schoolnik. The Vibrio cholerae chitin utilization program . The National Academy of Sciences of the USA (2004).

• C. Kristich and GW. Ordal. Bacillus subtilis CheD is a chemoreceptor modification enzyme required for chemotaxis. J Biol Chem. 2002 Jul 12;277(28):25356-62. Epub 2002 May 13.
  

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