How?
The goal of our project is to construct a noise-free, functional genetic circuit that uses two orthogonal, interspecies signaling molecules that can regulate the population levels of two different species of bacteria, E. coli and Streptomycces. Our inputs in the system are arabinose and salicylate.
Once arabinose has been added to the system, it will repress AraC, allowing for the production of tetracycline by Streptomycees. The tetracycline acts as an interspecies quorum sensing molecule and allows for the expression of Gene A or the methionine synthase gene in E.Coli. As an indicator that this has occurred, GFP will allow the bacteria to glow green. Upon production of methionine synthase, the E.Coli population will increase as methionine (an essential amino acid) availability increases.
Concurrently, salicylate will bind to nahR allowing for the production of LuxS. Expression of this gene allows for interspecies quorum sensing, signaling Streptomycces to express lysine synthase. Again, as an indicator, RFP allows for red fluorescence. Streptomycces population increases as lysine is also an essential amino acid.
In order to control population levels of both bacterial strains, we can incorporate external stimuli, namely heat and IPTG. Addition of heat to express TetX, which degrades tetracycline will decrease the expression of Methionine synthase (decrease the population of E. Coli). Similarly, addition of IPTG to express lsrK, which degrades AI-2 will decrease the expression of lysine synthase (decrease the population of Streptomyces griesius).
This circuit is displayed below:
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