Team:SiCAU-China/Contribution

The QS system LuxR/LuxI has been widely used in kinds of logic circuit. In our positive feedback loop, We hope it can detect input signal in stationary phase so that our system will not be impact by the population quantity variation and have shorter time as well as Better detection limits. However, the part LuxR can not work as expection while in stationary phase in E.coli. We construction the 4A5-R-G and transform it to E.coli BL21 to test LuxR. We added AHL(10^-7M) into it at different growth period, and measure the fluorescence.

We found that when we add AHL after 15h culture, GFP could not express obviously compared to control which did not add AHL. That means the LuxR cannot work well when the host, E.coli, grow to a certain period. According to the research, LuxR is unstable unless combine to AHL. With the E.coli growth , the substance of the medium will change, and which may cause the LuxR fail to combine to AHL.

AHL usually activate LuxR in logarithmic growth phase in previous project, so there’re few researcher noticed that LuxR cannot always work in E.coli. This characteristic of our contribution may be useful to users who will use LuxR as an activating transcription.