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Live Photographs
Living Photographs developed with the E. Coli Bacterium
Photographs built with Escherichia Coli (E. Coli) bacteria's
commonly found in lower intenstines of mammals was the main attraction of last
year's MIT's Genetically Engineered Machine (iGEM) competition. Although
there's no winner of the iGEM contest, the research team from University of
Texas at Austin was rewarded when their research was published in the Nov. 26
issue of Nature, in an issue focused on the field of synthetic biology.
Research Students Aaron Chevalier, Jeff Tabor and Laura Lavery
from University of texas used a new biological circuit in the E. coli to sense
light and make black pigment. Each bacterium acts like a pixel on a computer
screen, turning black when growing in the dark part of a projection and staying
clear in the light.
Massachusetts Institute of Technology's annual intercollegiate
Genetically Engineered Machine (iGEM) competition encourages students to build
simple biological machines. "This is a great example of the emergent field of
synthetic biology-using principles of engineering in biology," says Dr. Edward
Marcotte, one of the students' faculty advisers and associate professor of
biochemistry.
The Texas team, including students Alexander Scouras and Eric
Davidson, postdoctoral researcher Matthew Levy, and CSSB researcher Zachary
Booth Simpson, decided that they wanted to use E. coli to create an outline
around a projected light image. But first, they needed E. coli-a standard
workhorse for genetic engineering in the lab-that could sense light.
Left Image is Projected on Bacteria Plate and Right Image is the Resulted
Bacteria Photograph
They found their engineered microbe in the lab of Dr. Chris
Voigt, an assistant professor of pharmaceutical chemistry at the University of
California, San Francisco (UCSF). Voigt and his graduate student Anselm
Levskaya had engineered a strain of E. coli to sense light by adding a light
receptor protein from a photosynthetic blue-green algae to the microbe's cell
surface.
In order for the UCSF scientists to know if the E. coli were
responding to light, they also connected the light receptor to a genetic system
in the bacteria that leads to the digestion of sugars. When light hits the
receptors on the surface of the modified microbes, it turns off a gene that
leads to the production of a sugar-digesting enzyme. So in the dark, the
microbes digest sugar. In the light, they don't.
The Texas students then engineered a biological film-an
agar-filled Petri dish optimized so that the E. coli grow evenly throughout the
dish. Importantly, the film is infused with a special sugar engineered to turn
black when digested. When the bacteria grow in dark parts of the Petri dish,
they digest the sugar and produce black pigment. Those in the light don't
produce the sugar-digesting enzyme and the film remains clear.
Left Image is Projected on Bacteria Plate and Right Image is the Resulted
Bacteria Photograph
Using the same bacterial photography technology, they are
engineering bacteria that will create only the outline of a pattern of light
projected on them, rather than an entire image. They're also creating what they
call "light wires," which uses a Petri dish of E. coli as a circuit board to
conduct biochemical currents. Cells in the dark will propagate the current,
while cells in the light will be repressed.
And they aren't the only ones using the photographic technology.
Marcotte says the photography set-up is now becoming a standard tool for
engineering bacteria to perform new tasks. The students, for their part, have
contributed to the growing field of synthetic biology.
Synthetic biologists like Marcotte and his students and
colleagues at the Center for Systems and Synthetic Biology are harnessing the
power of genetic engineering to build new biological machines-computers that
process information, living systems that manufacture new materials or produce
energy, and bacteria that make and administer drugs. They use genes and
molecules much like engineers use wires and circuit boards.
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