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From 2013.igem.org

Overall project

Our project aims to produce a reliable three wavelength control system for E coli and use it to produce a full colour photograph or Colour E. Coliroid. We will be building upon the work done by previous teams and institutions, most notably UT Austin 2004 iGEM and Uppsala 2011 iGEM. Throughout the project extensive modelling of the system will quantify its behavior for future users.

In order to produce a full colour spectrum our E. coli will be modified to detect the primary colours of light; red, green and blue wavelengths of light and produce the corrosponding mix of the primary colours of pigment; cyan, magenta and yellow. This will then be put into a camera system and colour picture taken.

High spatial and medium temporal control over each output should be possible by using lasers of various wavelengths. This has many potential applications from the manufacturing of composite materials to control of released engineered organisms in an environment.

Although many have grappled with multiple wavelength control of E. coli we are confident of making meaningful advances in this area and contributing valuable new biobricks to the registy.

As a sideline, we’re also going to test a new way of preserving and presenting bacterial culture using pouring plastics. Unfortunately, this would kill the bacteria, but should give academics a new way to physically present colonies and cultures they have been working on. For us, it will allow a way of easily transporting our “photographs” without unwieldy plates and gels.

As mentioned we will be using additive and subtractive colour combinations to allow synthesis of the correct pigment output, corresponding to which colours of light they are exposed to. For example the NOT gated input of red light represses synthesis of cyan pigment enabling an output of yellow and magenta pigment. We hope to analyse the absorption spectrum of each pigment, both alone and in combination. Visualisation of light sensitivity throughout the system will enable calibration of the light input ensuring a reliable and sensical output. Further to this other teams reported their light sensing systems working better at temperatures <37 degrees, which we will also investigate.

For the blue and red light sensors, the presence of their corresponding wavelength of light causes autophosphorylation of an intermediate protein. Phosphorylated intermediates then freely bind as repressors to the corresponding output gene (cyan for red light, yellow for blue light). With the green light sensor, a signal inverter will be introduced, as the FixJ system acts as an activator not a repressor (the exact opposite of what we want). Instead of acting on the gene coding for the output (magenta) the phosphorylated intermediate binds instead to a gene coding for the cI protein used in the lambda phage (a bacteriophage which infects E. coli). Once synthesised the cl protein acts as the output (magenta) repressor.

The project can be followed on a [http://exeterigem.tumblr.com/ blog] created by the team.

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