Difference between revisions of "Team:SZMS 15 Shenzhen/project"

    The E.coli we constructed is able to gradually turn from colourless to green in a lactose included culture medium. The working mechanism is described in the following: constitutive promoter express lacI protein continuously. lacI protein binds with the lactose contained in the culture medium when there is a fair amount of lactose. Plac, a promoter that is oppressed by lacI protein will not be inhibited due to the lack of lacI protein, because lacI protein all binds with lactose. Plac will promote the expression of C0051, which is a kind of cI protein that exists in λ bacteriophage. The expression of C0051 will constantly inhibit the promoter R0051. As time elapse, the lactose in the culture medium will be gradually consumed, leaving no more lactose to bind with lacI protein, which will oppress the Plac promoter R0010, causing the end to the expression C0051. Because of the LVA tail, the remaining C0051 will be degraded, With the lack of C0051, the promoter R0051 will no longer be inhibited. The promoter R0051 can express GFP (green fluorescence protein), causing the E. coli to turn green.

    In common scenarios, lacI repressor will create leak expression, causing the expression of Plac even without the presence of lactose. However, according to an article, they claim to have found several kinds of “super repressor” with no leak expression. The article has given the gene sequence of these types of “super repressor”, we have chosen one and use PCR conducted site-specific mutagenesis to engineer the part C0012 in order to better achieve the system.

    The system we created contains two kinds of E. coli bacteria, one represents the fox and the other represents the grapes. The working mechanism is described in the following: under the stimulation of L-arabinose, the plasmid in the E. coli representing the fox starts to transcript C0071, which produced rhlR, a quorum sensing signal factor that leads to the working of R0071 in the plasmid of the E. coli representing the grapes, and gives out RFP. Then, with the transcription of C0061 in the E. coli representing the grapes, LuxR starts to produce continuously. LuxR stimulates the promoter R0062 and starts its promotion, which results in the expression of E0422 and produce enhanced cyan fluorescence protein (ECFP); at the same time, it represses the expression of R0063, which stops the E. coli representing the grapes from giving out the scent of bananas.

    We constructed this system with two different kinds of E. coli bacteria, one representing the sun and the other representing Houyi. The working mechanism is described in the following: first we transform a plasmid with the serial EC 1.7.7.2 to simulate the sun. EC 1.7.7.2 is a sequence of an enzyme that catalyses an exothermic reaction., causing the E. coli representing the sun to rise its temperature constantly. It should be noted that the expression of EC 1.7.7.2 is regulated by LuxI through the QS system. Second, we transformed a plasmid containing LuxI into another kind of E. coli representing Houyi. Due to the fact that the expression of EC 1.7.7.2 can be repressed by the presence of LuxI, the E. coli representing Houyi can effectively lower the temperature of the previously described E. coli with EC 1.7.7.2.