Team:ZJU-China/original

Versatile aptamer

ZJU-China this year want to use aptamer based biosensor to detect molecules of different size.

In order to detect large molecules such as protein, we use bacterial ghost technique to make tunnels through inner and outer membrane while at the same time keep periplasmic space intact. Protein can diffuse freely into the cell through the tunnel, and lead to subsequent receptor dimerization. These receptors are targeted to the inner-membrane and have both periplasmic terminal and plasmic terminal. Receptor periplamic terminal have enzymic activity once dimerized and can yield visible pigment. Biotin-tagged exogenous added aptamer in our project has both receptor plasmic terminal binding ability and protein binding end. Upon protein binding to aptamer, it will result in receptor dimerization and give pigment output.

In the second part, we want to detect and destroy a small molecule called atrazine, which is an herbicide that can cause flu-like symptoms when it contaminates drinking water. In order to make engineered E.coli diffuse more evenly in the plate, we separate atrazine sensing module and degradation module into two populations of cheZ deficient E.coli. For the first population, they will sense atrazine and control cheZ gene expression via a riboswitch mechanism; they will also excrete QS molecule AHL as to attract the second population. For the second population, atrazine degradation gene and cheZ gene are under the control of PluxR. So they will follow the route of the first population over degrading atrazine in their way.

We also want to standardize some artificial-built riboswitches which are evolved from in vitro selected aptamers. We altogether aim to test four parameters of them. They are Static performance which means PoPS change according to different concentration of induction molecules; Dynamic performance which means PoPS change along the time; Input compatibility which shows the ability of riboswitch to distinguish structurally similar induction molecules and reliability which describes the ability of the device to continue functioning over many generations is reported.