At the beginning, we read a flood of literature, and found that rare earth elements, especially the capture methods, had attracted numerous scholars both at home and abroad to explore. They had already constructed successful genetically encoded sensors for some rare earth elements. However, the lanthanide elements, one of the important and wealthy rare earth elements, are not included. Consequently, this year,our team is eager to fill the research vacancy.
We want to construct an intelligent system. Only when the concentration of the lanthanide ions reach the threshold, does it react.
In order to reach our goal, we need a smart sensing circuit. Fortunately, we found a two-component system called PmrA/PmrB. This system is aimed at detecting iron ions. If we can find appropriate sequence which can react to lanthanide ions, we can replace the iron-binding sequence with them to achieve our goal.
Through consulting a large number of literature, we made it! We know the most successful lanthanide binder is lanthanide-binding tag. And we will call it LBT in the following. After exchanging sequences, we fuse the pmrC promoter to the gfp gene which encodes green fluorescent protein to prove whether or not the PmrA-PmrB(LBT) are responsive to lanthanide.
Ions sensing is just the first step, then we need to capture them. In this part, we also use LBT——our good lanthanide hunter.
In order to capture more efficiently, we connect 3 LBTs by GS linker on the membrane.
Now our bacteria have collected a lot of lanthanide ions. What we need to do at last is just capturing our cells. So we designed the Si-tag, which we did in our team's previous project, to combine the bacteria with silicon in order to get our bacteria back.
The circuit below can illustrate our project better:
