Genetically Modified Bacteria Produce Living Photographs
for National Geographic News
|December 6, 2005|
Hold still and say, E. coli.
In an unusual proof-of-concept display, researchers have developed a way to create photographs with living bacteria.
The results are not only much sharper than what can be produced with a photo printer, but also point the way to a new industrybuilding useful objects from living organisms.
According to the researchers, this biological film is an early success for an emerging field known as synthetic biology, the science of making simple organisms that can exhibit predetermined behaviors.
"The photograph was mainly a cute parlor trick, [but it provided] a demonstration of our ability to use these things," said Anselm Levskaya, a biophysics graduate student at the University of California, San Francisco (UCSF), who worked on the project.
Researchers at UCSF collaborated with colleagues at the University of Texas at Austin to create the living photos. They described their work in the November 24 issue of the science journal Nature.
Seeing the Light
Nondigital photographs are made by momentarily exposing light-sensitive film, then processing the film to capture the image, which is transfered with light onto chemically treated paper.
In the new approach, E. coli bacteria that have been genetically modified to react to light record the image.
University of Texas students first concocted the idea as an entry in a genetic engineering contest held by the Massachusetts Institute of Technology.
To complete the job, the students needed a light-sensitive living substance. By coincidence, their faculty advisor Edward Marcotte had recently met Chris Voigt, an assistant professor of pharmaceutical chemistry at UCSF, who had been working on such a product using E. coli.
Genetic researchers frequently use E. coli because the bacteria grow quickly in the lab. In nature E. coli typically reside in the intestines of people and other animals. The bacteria do not sense light.
Hoping to endow the bacteria with light-sensing abilities, Voigt looked for receptors from other simple organisms that could be grafted onto E. coli.
After some searching, Voigt and his team found proteins on photosynthetic blue-green algae that would do the trick.
"We were fairly lucky," said Levskaya, who assisted Voigt. Grafting the receptors onto an E. coli bacterium "is sort of like a knitting operation."
"They did the hard engineering work [at UCSF], and we took advantage of it to implement our idea," said University of Texas graduate student Jeff Tabor, a doctoral student who worked on the project.
The Texas students grew a sample of Voigt's E. coli in dishes of agar, a standard Jellolike growth medium for bacteria.
They built a special projector to shine light through a mask onto a colony of the modified bacteria. Each bacterium produced a black pigment if it did not sense light.
Using this approach, the bacteria generated a photographic reproduction in about 12 hours. Researchers say the image has a resolution a thousand times greater than what can be produced by today's high-end printers.
UCSF student Levskaya said that he is working on finding other biological light-sensors that can produce other wavelengthsperhaps leading to the possibility of producing color photographs in a similar manner.
The research paves the way for producing genetically modified organisms that could be useful in other applications. The researchers say, for example, that the technology could one day be used to program and grow living tissues to help fight cancer.
This approach could be inexpensive, thanks to bacteria's ability to rapidly proliferate when given warmth, oxygen, and food.
"You can start with one bacterium, and you can have billions in a matter of hours," Tabor, of the University of Texas, said.
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