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 would not be impact by the population quantity variation, and could require shorter time as well as better detection limits. However, the part LuxR cannot work as expection while in stationary phase of E.coli. We constructed the 4A5-R-G and transform it into E.coli BL21 to test LuxR. We added AHL(10^-7M) into it at different growth periods, and measured the fluorescence.

We found that when we added AHL after 15h culturing, GFP could not express obviously while being compared to the control which contained no add AHL. That means the LuxR couldn’t work well when the host, E.coli, growed to a certain period. According to the research, combining to AHL is essential for the LuxR stability. With the E.coli growing, the substance of the medium will change, and this may cause the LuxR fail to combine with AHL.

AHL usually activate LuxR in logarithmic growth phase in previous project, so that there’re few researchers noticed that LuxR cannot work in E.coli all the time. The characteristic of our contribution referred above may be useful to users who would use LuxR as an activating transcription.