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From 2011.igem.org

We have been working hard to model our system. In a single cell, the system acts like a fast switch upon AHL concentration, on the other hand, cheZ ouput is a slow switch of theophylline concentration. We can see that cheZ concentration rises rapidly when AHL concentration rises from 3nM to 4nM. For the switch is so fast that we can use quorum system in our design. CheZ output rises relatively rapid when theophylline concentration is around 210nM. For the system without quorum part, If AHL concentration is low, regulate ci protein accumulates, the toggle switch is in the ci state, cheZ production is very low, so the cell can rarely move. And when AHL concentration is high, not enough regulate ci protein is produced, the toggle switch is in the ci434 state, cheZ production is high, so the cell can spend less time tumbling, and will move to the direction where cheZ concentration rises. Following pictures show how steady-state cheZ concentrations change under conditions of different AHL and theophylline concentrations. 图片文件夹1 Following pictures show how cheZ concentrations change on time under conditions of different AHL and theophylline concentrations. 图片文件夹2 Following pictures show how a single cell moves on time under conditions of different AHL and theophylline concentrations in one single round of simulation. 图片文件夹2 Following pictures show how a single cell moves and how cheZ concentration changes on time under conditions of 10nM AHL and gradient of theophylline concentration (30,600) in one single round of simulation. 图片文件夹3 Following pictures show 100 cells move under 10nM AHL and gradient of theophylline concentration (25,500). 图片+flash For the whole system with quorum part, in the beginning, we assume that the concentrations of all related macromolecules are zero. Cells begin to divide, cell number is growing, and AHL is accumulating, when AHL concentration is high enough, toggle switch in some of the cells turns to the ci434 state, and these cells is moving out. After some time, AHL concentration in these cells will drop, and the toggle switch will most likely turn to the ci state, cells stop moving. For this part we assume that numbers of the cells grow under the rate of k=0.97*exp(-t/5), the unit of time is hour. For no gradient of theophylline 图片 For theophylline gradient (25,500) 图片