At the beginning, we read a large amount of literature, and we found that, rare earth elements with high value attracted a lot of people to study, especially the recycling. They have already constructed successful genetically encoded sensors for some rare earth elements. However, the lanthanide ions, as an important rare earth element,are not included. Consequently, our team are eager to try to solve this problem this year.
We want to construct a smart system. Only when the concentration of the lanthanide ions in the environment reaches the threshold, it reacts.
In order to reach our goal, we need a smart sensing part. We found a two-component system called PmrA/PmrB. This system itself is aimed at iron ions. But if we can find the appropriate sequence which can react to lanthanide ions, we can replace the iron-binding and achive our goal of sensing.
Fortunately, we did find it! Through the search, we know the most successful lanthanide binders are lanthanide-binding tags,we will call it LBT in the following. After replacing, we fuse the pmrC promoter to the gfp gene which encodes green fluorescent protein to prove whether or not the PmrA-B-LBT are responsive to lanthanide.
Ions sensing is only the first step, and then we need to recycle them.In this part, we also used LBT——our good lanthanide hunter.
But it’s not good enough to recycle. To maximize its potential, we repeat them three times on cell with GS-Linker between each.
Now our bacteria has collected a lot of lanthanide ions, what we need to do at last is just recycling our cells. So we used the Si-tag which we did in the previous project of our team to combine the bacteria with silicon to facilitate recycling our bacterias.
The circuit below can illustrate our project better:
