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We constructed the plasmid with lactose operator and signal peptide, and transformed this plasmid into E. coli to test if this kill switch works. We used gradient plate method in our experiment. As we can see in the picture, the concentration of IPTG on the left of the medium is 0.1% while the concentration on the right is zero. We can see colony only on the right of the medium, the kill switch is effective which illustrates that IPTG can induce the expression of signal peptide and LALF so as to inhibit the growth of the E.coli. Also, a decrease of OD is observed too, after we added IPTG to the liquid culture medium, which means our kill switch did work well.
