Team:Korea U Seoul/Project/Improvement

     Rice Guardian project was to build an engineered E. coli which detects and kills. However, our team had difficulties making plasmid construction which follows iGEM regulation. Therefore, our team decided to make Xanthomonas oryzae KACC10331 detecting E. coli beforehand. As we already discussed the mechanism of these bacteria, our team used red light emitting protein (RFP) as a final output instead of lysis and bacteriocin gene. Our alternative approach was successful and we decided to go one step further. Our team is conducting an experiment to add lysis and bacteriocin gene and this experiment will be done before iGEM championship.

     Addition of lysis and bacteriocin gene ensures death of nearby Xanthomonas oryzae KACC10331. Bacteriocins are proteinaceoustoxins produced by bacteria to inhibit the growth of similar or closely related bacterial strain(s). They are typically considered to be narrow spectrum antibiotics, though this has been debated . Lysis gene causes death of E. coli releasing bacteriocin inside the cell.

     Constitutive promoter will produce RaxR and RaxH. Protein synthesized from the genes allows cell to detect Ax21. When RaxR and RaxH proteins detect Ax21, They work as protein kinase (mechanism unknown) and stimulate bacteriocin and lysis gene. When lysis protein induces cell death of the E. coli , bacteriocin will burst into the surrounding and attacks Xanthomonas oryzae KACC10331.

     Designing this project, our team's final goal was to make standardized logic gate modules for organizing biological logic circuit. Therefore, every designed logic gates' input signal chemical had to be same with output signal chemical. (In this project,the chemical was named Chemical A) And to show how well this works, we planned to make binary full adder. However, due to the difficulty of finding Chemical A, experiment was not yet done. We recently decided use C4HSL for Chemical A. C4HSL is molecule used in quorum sensing between bacteria, therefore it is density dependent. This means the density of the bacteria in the logic gate effect on the signal intensity. We are still searching for the chemical substance, substitute for C4HSL. While converting Chemical A to input signal, the original signal from the previous logic gate can be either amplified or dampened. This directly effects on the logic operation and change the total calculation result. To prevent this condition, further study of the conversion rate must be is needed.

     Because we designed the binary full adder, currently we are not perfectly sure how linking more than one full adder module will effect on the calculation result. If we succeed in making the binary adder module, experiment on three or more digit binary adder can be done as the further study.