Team:Toulouse/Project/Chemotaxis

What is chemotaxis?

Chemotaxis is a bacterial function which allows moving toward a gradient of concentration of a molecule that is present in the medium. With this system bacteria can swim to a location containing higher concentrations of molecules such as sugar, amino acid, vitamins... Chemotactic-signal transducers respond to changes in the concentration of attractants and repellents in the environment, transduce the 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 come close to the location of fungi infection. During its growth, fungi release N-acetylglucosamine (NAG), the basic unit of chitin which composed its cell wall. Thus, there should exist a gradient of the concentration of NAG around the fungi.

It is known that B. subtilis is able to detect and to swim towards glucose using the Methyl-accepting chemotaxis protein, called McpA.
Some bacteria are attracted by NAG, like Vibrio cholerae which has a NAG regulated methyl-accepting chemotaxis protein: VCD.

Therefore, our idea is to switch the natural glucose specificity of B. subtilis' McpA to 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 B. 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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