Why we care about cadmium and sulfate in the environment:

Both cadmium and sulfate can be found in wastewater and is produced from processes such as electroplating. If these contaminants are not removed from the environment, they can have a detrimental impact upon living organisms. For example, 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.

How are these two processes intertwined?

We are tweaking the cysteine biosynthesis pathway, allowing the over-expression of cysteine and the utilisation of the sulfate our cell takes up. In addition, we are tweaking another system, the production of phytochelatins. We are over-producing cysteine-rich phytochelatins which will themselves act as a sink for sulfate. These phytochelatins can then chelate the cadmium that accumulates and thus, will act as a sink for cadmium also.