Design
Our Aim
We endeavor our strains to grow into patterns by arranging themselves in a synchronous, self-organised manner, “just as in organisms in nature which all are able to develop shapes and patterns.” Implementing such idea on bacteria sheds light to a mechanism involving cell-cell communication that would produce a key response, predominately a respond affecting cell motility. The characteristics of the response logically should be critical towards the formation overall pattern.
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Chassis selection
Past chemotaxis studies have provided the molecular basis of cellular motility regulation, Escherichia coli and Bacillus subtilis are notably the well-understood strains which are ideal to be the chassis of our designed genetic circuit. We chose E.coli as our chassis for the project reasoning that cell-cell communications will require the use of a signaling molecule, which are often density related. E.coli is known to be less motile than Bacillus in terms of speed, thus would ease the accumulation of the signaling molecule. We hope the subsequent pattern generated by using E.coli as chassis would be finer and more interesting.
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Genetic Circuit Design
An On-Off motility design is desired as the response to cell-cell communication. Based on the pioneer work (Topp & Gallivan 2006) shows the motility can be abolished by knocking out the cheZgene, and can be restored by subsequent re-introduction of the cheZ gene under a controllable promoter back into the host.
We designed two DNA constructs whose cheZ expression level would be sensitive to the concentration of AHL (Acetyl homoserine lactone). One would become motile in the presence of AHL, while the other one be become immotile under the same condition. Since concentration of AHL is proportional to cell density, the motility of our strains would be dependent on local cell density.
Predicted Pattern:
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Plasmids and strains
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