Team:Caltech

Hi! We are the Caltech 2011 iGEM Team. We are interested in bioremediation of endocrine disruptors or organic pollutants :)

EDCs (Endocrine Disrupting Chemicals) are substances which detrimentally effect the development and reproduction of wild organisms. To remedy that, the Caltech iGEM team hopes to engineer bacteria which can sense and degrade DDT, estrogen, bisphenol A, and nonylphenol to less toxic forms. Compared to more traditional forms of pollution removal, bioremediation would be relatively cheaper and less disruptive to the environment. However, a successful project must make sure that the bacteria used for remediation do not act as pollutants or introduce toxic byproducts into the environment.

To start, we hope to create genetic elements that initiate the production of signaling proteins upon exposure to endocrine disrupting chemicals and to identify enzymes that can degrade endocrine disruptors. Eventually, these components will be combined in a signal transduction system that can be used to detect and remove endocrine disruptors from bodies of water.

The detection pathway triggered by the binding of an endocrine disruptor to a receptor can be used to activate the production of the degradation enzymes. In our testing stages, the receptor will activate a visual reporter pathway instead. Our plan is to alter the human receptor-activation pathway for estrogen to fit our project. When the human estrogen receptor binds to estrogen, it dimerizes into a construct that can bind to a responsive element on human DNA, triggering transcription. This receptor has been tested in E. coli in previous work, but has also shown a high toxicity to the organism. We will alter the receptor using protein tags such as maltose, green fluorescent protein, and ubiquitin, as these have been demonstrated to help the estrogen receptor fold and to minimize its toxicity in E. coli. Since the estrogen receptor shows low-specificity binding to general endocrine disruptors, we can use site-directed mutagenesis to increase its specificity to our target chemicals DDT, ethinyl estradiol, BPA, and nonylphenol.

Multiple pathways for degradation are being explored. We hope to optimize previously established degradation pathways for DDT and BPA as well as search for novel pathways for all four chemicals. Prior research has indicated that there exist proteins can degrade DDT; however, these are poorly characterized and have not been successfully introduced into E. coli. Luckily, enzymes and constructs which degrade BPA have established functionality in E. coli and are in the parts registry. We base our experiment upon these results by searching for new genes in LA river bacteria that can degrade endocrine disruptors and exploring the abilities of the aforementioned genes.