Imperial College/Courses/Spring2008/Synthetic Biology/Team 5

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This page may be used to host the write-up of a mini-iGEM project being undertaken by Team 5 of the Imperial College London Synthetic Biology course 2008 - the project being to academically investigate a theoretical iGEM proposal and present it to a mock 'funding committee'.

If this is not allowed/isn't acceptable, please email me at taa104 at and I'll find somewhere else to host this!


Our proposal for an iGEM project was originally based on an interface between electrical and biological systems. It has since evolved to be an attempt to construct a bio-implant - a synthetic gland, as it were - that can administer drugs, release hormones or perform other functions when triggered to do so by an external stimulus. Instead of an electrical stimulus we have opted to utilise an optical fiber implanted through the skin to transmit light pulses to the bio-implant and trigger expression of a target molecule. We have extended our criteria to include an 'on' signal and an 'off' signal, each encoded by different wavelengths and controlled by the duration of the pulse.

The Sensor Array

Blue light inhibits - BLUF
Red light activates -


Applications for this system are near limitless, as the gene that is transcribed upon activation by light is interchangeable. Specifically, one might imagine release of a hormone could be triggered in hormone replacement therapies, or insulin could be produced in diabetics with the system replacing the need for injections (dosage variable with duration of light pulse)

While in testing, however, we need an easily-detectable reporter. GFP as a candidate was swiftly dismissed, as using a fluorescent protein to report on the activity of light-sensitive bacteria would undoubtedly lead to interference and skewed results! Antibiotic expression in concert with antibiotic resistance could be relevant as antibiotic-producing bacteria may be a useful bio-implant and would also be an accurate reporter - the complexity of this system may impose on our timetable, however, so we have decided ultimately to use the well-characterised lacZ reporter construct. In this system, bacteria that produce the protein exhibit a blue colouration as opposed to a standard white colour for negative results. [1]

Thus if we tack on a lacZ reporter to the construct the system could be tested using plated cells exposed to light patterns and examined later for distribution of blue colonies vs. white ones.

There is already a lacZ reporter in the MIT registry; part BBa_E0033. This part is a section of the lacZ gene (the lacZ-alpha fragment) such that, when cultured with N-terminal deletion mutants of lacZ, enzyme activity is restored and plates can be assayed by eye.

Our system so far:

Overview of our system