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Assembly Plan

Background

Movement and Chemotaxis

Chemotaxis is the cell’s system for directed movement which allows the cell to move towards nutrition sources as well as away from toxic substances. The chemotactic system is a complex chain of phosphorylation reactions. At the end of the chain is the flagellum-binding protein CheY. The phosphorylated CheY (CheY-p) binds the flagella and causes the cell to tumble in place, essentially remaining immotile. The phosphatase CheZ dephosphorylates CheY, causing CheY to unbind to the flagella, resulting in directed movement of the cell [1]. More factors are involved in the full chemotactic pathway of E.coli, although they are not of importance for our project.

Using Chemotaxis to track down a pathogen

Due to the complexity of the chemotactic pathway of E.coli, controlling the steering of this chemotactic car was not an option. Instead, we decided to manipulate the breaks, so that our bacteria would stop moving once close enough to the pathogen and deliver a deadly dose of bacteriocin.
To achieve this stop-and-kill mechanism, focus was laid on the protein CheZ. As mentioned above, the bacteria cannot move straight in the absence of CheZ, but tumbles in place instead, so by stopping the production of CheZ we essentially get an immotile bacterium. Then, by producing CheZ under controlled manners, the bacteria would ideally become motile again but on our terms. The production of CheZ would be controlled by a system based on the quorum sensing (see Sensing) of our pathogen, designed by the Sensing group. The result would be low production of CheZ when close to the pathogen and high production when far away from it.