Team:DLUT China/Improve

Improve

Figure 1 Improve system 1, composed of promoter hucO, hypothetical uricase regulator which called HucR, uric acid transporter which called ygfU and lysis protein.
We made drastic improvements to the 2017 Hong Kong UCCKE team's BBa_K2197302 components. We placed HucR behind the PhucO sequence for self-regulation purposes. We also added the uric acid transporter ( ygfU), which reduces the system's response concentration to uric acid and increases the sensitivity of the system. We also added lytic proteins to the sequence to make the system a lethal system that can be induced using uric acid.

Figure 2 Improve system 2, composed of two plasmids. Plasmid 1 is composed of the promoter hucO, hypothetical uricase regulator which called HucR, uric acid transporter which called ygfU, sRNA and lysis protein. Plasmid 2 is composed of the sRNA and lysis protein.
We also designed a second lethal system. We used two plasmids with two different lysis proteins, and the sRNA on plasmid 1 inhibited the expression of lysis proteins on plasmid 2, while the sRNA on plasmid 2 inhibited the expression of the lysis protein on plasmid 1. If any one of the plasmids is lost, the expression of the lysis protein on the other plasmid is not inhibited, resulting in the death of the bacterium, and the purpose of preventing the loss of a plasmid. At the same time, under the condition that the uric acid concentration is higher than the threshold, HucR is inhibited by uric acid, sRNA is normal expression, and the expression of lysis protein is inhibited. Under the condition that the uric acid concentration is lower than the threshold, HucR inhibits Phuco, and the subsequent sequence of plasmid 1 cannot be expressed normally. Thus, the expression of the cleavage protein in the plasmid 2 was not inhibited, and the bacterium was killed by lysis protein. Because the uric acid content in the in vitro environment is not high, the uric acid concentration is lower than the threshold. Therefore, when the bacteria are lost to the external environment, the bacteria are lysed due to the expression of the system, thereby preventing the loss of the experimental strain to the external environment.