Science Interviews

How to Make a Bacterial Camera

Chris S - What have you done?

Chris V - What we've done is to use genetic engineering to create a strain of bacteria that's able to respond to light. If you look a pond, you'll often see a green sludge. That sludge is sometimes bacteria, and the reason it's green is that the bacteria can photosynthesise. In order to do that, it has to be able to see light. We took a gene from the bacteria you find in ponds and we modified it so that it works in a bacteria that's normally living in your gut. These don't normally have to see light. It's called E. coli. By adding this gene and doing a few more modifications to the genome of E. coli, we made it so that individual E. coli cells are able to see light.

Chris S - When you shine a light on them, what does it do to the bacteria?

Chris V - It has a special type of protein that's on the surface of the bacterium. It's special in that it has a chemical on it that causes the protein to change shape when light is on it. This change in protein shape is recognised by the bacteria, and this leads to turning on a gene. In this way, you can couple shining light on the bacteria to the switching on of a gene.

Chris S - And what sort of things have you made it activate? In the paper you published in Nature this week, you were able to make your bacteria change colour. What else could you do?

Chris V - You could imagine using this for a wide range of applications. If you think about constructing complex materials, such as proteins, they can be very difficult from a chemistry perspective. It would be useful if you were able to print proteins with a very high resolution. We are thinking about using this system to have individual bacteria turn on the production of proteins that produce a particular type of material like spider silk.

Chris S - If you bought this bacteria as a digital camera in the shops, what number of megapixels would it say on the box?

Chris V - If it was able to turn on individual bacteria, it would be about 100 megapixels.

Chris S - So that's a tiny resolution you can work at. You can make really fine structures.

Kat - Are these bacteria dangerous at all?

Chris V - No, they're completely harmless. We're using what is known as a lab strain of E. coli. This differs from natural strains because almost 85% of its genome is missing. This strain of bacteria is used frequently in the lab because it's a very safe strain.

November 2005