Both cadmium and sulfate can be found in wastewater and in high concentrations from industrial output. For example, cadmium is widely used in a process known as electroplating. If these contaminants are not removed from the environment, they have a detrimental impact upon living organisms. If cadmium is consumed by mammals over a long period of time, it can cause health problems such as Itai-Itai disease (cadmium poisoning). This year, our project at iGEM York is focusing on increasing the uptake of cadmium and sulfate in our chosen chassis E. coli. The project has two main, interlinked approaches:

• Firstly, the increased uptake of sulfur using an exogenous sulfate transporter from Bacillus.

• Secondly the increased uptake and chelation of cadmium ions through the use of metal-binding proteins, to produce a potentially recoverable metal product.

The link between these two processes is the cysteine-rich phytochelatins. The phytochelatins we are over-expressing in our chassis are rich in cysteine and as a result, rich in sulfate. Thus our phytochelatins act as a sink for sulfate whilst chelating the cadmium that builds up inside the cell.