Team:Cambridge/Non-Biologist

Synthetic biology is a new discipline which has arisen as scientists have developed better techniques for manipulating genetic material, and a better understanding of how existing organisms work. In almost every case it involves taking the genes which exist naturally after billions of years of evolution and combining and changing them in novel ways.

Engineering disciplines rely on standardisation of parts and one of the chief aims of iGEM is to create a Registry of Standard Parts for synthetic biology. Teams must submit all the genetic constructs they use in their projects to this central repository from which they are distributed to future teams. Gradually a full toolkit is built up.

The work of the Cambridge team this year is a prime example of both these aspects of iGEM. The team began the project by scouring the light producer's that had been produced by the natural world. They considered a large number of candidates, including glow worms, jellyfish and a bacterium called Photobacterium phosphoreum.

But in the end they settled on three species:

• The North American Firefly, Photinus pyralis was selected because it is known for its brightness, and because papers had recently been published which suggested more progress could be made
• The Japanese Firefly, Luciola cruciata was selected because papers showed that it could be easily changed to emit a number of different colours
• Vibrio fischeri, a bacterium which inhabits squid, and allows them to emit light (a symbiotic relationship) was selected for its blue colour and because unlike firefly genes it required nothing but nutrients to emit light.

The team then needed the DNA to work with, a number of approaches were taken here.

• Genes had already been extracted from Vibrio fischeri and stored in circles of DNA known as plasmids. We contacted James Slock at King's College who offered to send us his plasmids. But when they arrived we still had a great deal of work to do.

Vibrio fischeri has a rather interesting way of life. It can either be free-living or live in the light organs of large marine organisms. These two distinct lifestyles require different proteins to be produced by the bacteria. It is useless to waste resources emitting light when floating around as a single cell in the sea. The bacterium has a clever control mechanism - each bacteria constantly produces a small amount of a chemical called AHL which is free to diffuse into the liquid outside. Only at high levels of this chemical will the genes for light emission be activated.

This activation process is controlled by a particular region of DNA known as a promoter which comes just before the light producing genes. We wanted to end the reliance on AHL for light output, to achieve this we made a new BioBrick using a promoter called pBAD from the Registry. This allows light output to be triggered by adding a small amount of a sugar called arabinose. We also synthesised a BioBrick containing just the light emitting genes with no promoter, this will allow future teams to use light output in any way they which. For example they could use a carbon-monoxide sensitive promoter to make a sensor.