Wednesday, November 23, 2005

Living Bacterial Photographs

Using Petri dishes full of genetically engineered E. coli instead of photo paper, students at The University of Texas at Austin and UCSF successfully created the first-ever bacterial photographs.

Their work is published in this week's issue of Nature (Nov. 24, 2005), which is devoted entirely to the emerging field of synthetic biology.

The students produced the innovative bacterial images and a bacterial camera as part of MIT's intercollegiate Genetically Engineered Machine (iGEM) competition, which encourages students to build simple biological machines.

"The goal of the contest was to build bacteria that could do very simple computing," says Dr. Edward Marcotte, one of the students' faculty advisers and associate professor of biochemistry at The University of Texas at Austin. "This is a great example of the emergent field of synthetic biology--using principles of engineering in biology."

The students produced ghostlike, living photos of many things, including themselves, their advisers and The University of Texas Tower.

The bacterial photos were created by projecting light on "biological film"--billions of genetically engineered E. coli growing in dishes of agar, a standard jello-like growth medium for bacteria.

Like pixels on a computer screen switching between white and black, each bacterium either produced black pigment or didn't, based on whether it was growing in a light or dark place in the dish. The resulting images are a collection of all the bacteria responding to the pattern of light.

The light receptor was connected to a system in the bacteria that makes pigments. When light strikes the new receptor, it turns off a gene that ultimately controls the production of a colored compound in the bacteria.

The device projects the pattern of light--like an image of one of the Texas students' co-advisers, Dr. Andy "Escherichia" Ellington--onto the dish of bacteria growing at body temperature in an incubator. After about 12-15 hours of exposure (the time it takes for a bacterial population to grow and fill the Petri dish), the light projector is removed.

What's left is a living photograph.

New Scientist


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