Bacterial Photography

Using parts from a toolkit developed by
genetic engineers, a team of students has
created light-sensitive bacteria that work as
photographic film. It's an example of
synthetic biology: a new way of thinking
about life that owes as much to Henry Ford
as Charles Darwin.
Engineers take it for granted that they can
take a selection of screws, bolts and
standard parts off the shelf to create whatever they want. Taking this approach
to living systems might seem like science fiction. But it is exactly how students
from the University of Texas built a bacterial-photography system for last year's
Intercollegiate Genetically Engineered Machine competition at the Massachusetts
Institute of Technology (MIT). The fruits of their labour are published in Nature 1,
and the team has since added to their invention for this year's competition (see
' Designs on life ').
The team started with the well-known gut bacteria Escherichia coli , and,
thinking like engineers, added extra 'parts' made at the University of California,
San Francisco (UCSF). To make bacterial photography work, they needed to
make E. coli respond to different levels of light by producing different amounts
of a coloured substance. Then a film of the bacteria would work just like the film
in a camera.
Paint me a picture
Habituated as it is to the dark insides of intestines, E. coli cannot detect light.
So the first component the team needed was a light sensor.
One had already been designed at UCSF. The
sensor consists of two parts: a protein from a
blue-green alga called Synechocystis ,which detects
light, and a second protein, which switches a particular E. coli gene on and off.
In normal E. coli , this gene is triggered by low water concentrations, and affects
the surface membrane of the bug.
The next step was to swap this membrane-protein gene for something more
useful: a gene that turns a certain chemical black.
The finished bacteria made their surroundings black unless they were exposed
to light, at which point the light-sensitive switch turned off production of the
blackening chemicals.
The more light, the less colour is produced, so that black and white
photography is possible. A film of the bacteria can record an image at a high
resolution of 100 megapixels per square inch.
The sum of its parts
"This kicks ass," says Drew Endy, a synthetic biologist at MIT, about the Texas
students' success. "These kids aren't Nobel laureates, but they could take parts
and make something like this in just a few months."
Instead of making black pigment, the bacteria could be redesigned to deposit
proteins like spider silk, says Chris Voigt, leader of the UCSF lab that created the
parts. Researchers in Voigt's lab are working on making bacteria produce
different substances in response to different colours to make it possible to
weave complex materials.
The parts made in Voigt's lab are available to anyone that wants them, thanks
to the Registry of Standard Biological Parts at MIT. It's a toolkit for synthetic
biologists that lists the different parts made, how they work, and how they can
be linked to others.
Pastures new
Other successes of synthetic biology include bacteria
programmed with a biological clock to produce fluorescent
pulses2 , and others that can be told to exchange information encoded as DNA.
But Endy admits that the field is far from easy. "We are still bad at engineering
biology," he says, "and what I want to know is how to get better at it."
Endy says that understanding how to make standard parts that can fit with any
other will unlock synthetic biology's potential. "Screw threads are standardized
so you know what you're getting," he says. "If we can develop standardized
components of living sytems, we can concentrate on the design and engineering
of new ones."
MIT.
References
1. LevskayaA., et al. Nature , 438. 441 - 442 doi:10.1038 (2005). |
Article | PubMed |
2. ElowitzMB., LeiblerS., et al. Nature , 403. 335 - 338doi:
10.1038/35002125 (2000).