Blunderov
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RE: virus: Engineer Turns Bacteria Into Living Computers
« on: 2005-04-30 17:34:01 » |
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[Blunderov] Gazing with wild surmise...
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http://www.sciencedaily.com/releases/2005/04/050427201634.htm
Programmable Cells: Engineer Turns Bacteria Into Living Computers
In a step toward making living cells function as if they were tiny
computers, engineers at Princeton have programmed bacteria to
communicate with each other and produce color-coded patterns.
The feat, accomplished in a biology lab within the Department of
Electrical Engineering, represents an important proof-of-principle in an
emerging field known as "synthetic biology," which aims to harness
living cells as workhorses that detect hazards, build structures or
repair tissues and organs within the body.
"We are really moving beyond the ability to program individual cells to
programming a large collection -- millions or billions -- of cells to do
interesting things," said Ron Weiss, an assistant professor of
electrical engineering and molecular biology.
Collaborating with researchers at the California Institute of
Technology, Weiss and graduate student Subhayu Basu programmed E. coli
bacteria to emit red or green fluorescent light in response to a signal
emitted from another set of E. coli. In one experiment, the cells glowed
green when they sensed a higher concentration of the signal chemical and
red when they sensed a lower concentration. In a Petri dish, they formed
a bull's-eye pattern -- a green circle inside a red one -- surrounding
the sender cells.
In addition to demonstrating that the genetic programming techniques
work, this sensing system could be useful for the detection of chemicals
or organisms in laboratory tests. "The bull's-eye could tell you: This
is where the anthrax is," said Weiss.
The researchers published their results in the April 28 issue of Nature.
In addition to Weiss and Basu, authors of the paper are postdoctoral
researcher Yoram Gerchman at Princeton and professor of chemical
engineering Frances Arnold and graduate student Cynthia Collins at
Caltech. It was funded by a grant from the U.S. Defense Advanced
Research Projects Agency.
In previous work, including a paper published March 8 in the Proceedings
of the National Academy of Sciences along with Sara Hooshangi and
Stephan Thiberge, Weiss showed the feasibility of inserting engineered
pieces of DNA into cells to make them behave in the same manner as
digital circuits. The cells, for example, could be made to perform basic
mathematical logic and produce crisp, reliable readouts that are more
commonly associated with silicon chips than biological organisms. The
new paper applies similar techniques to a large population of cells.
"Here we're showing an integrated package where the cells have an
ability to send messages and other cells have the ability to act on
these messages," said Weiss.
The creation of patterns, such as the bull's-eye effect, is a key step
in one of Weiss' eventual goals, which is to have the cells secrete
materials that build physical devices such as antennas or transmitters
in places that are hard for humans to reach. Programmed cells also could
be used to control the repair or construction of tissues within the
body, possibly guiding stem cells to the locations where they are needed
for the growth of new nerve or bone cells in a process Weiss called
"programmed tissue engineering."
Even the early step of creating patterns in a Petri dish, however, may
be useful as a tool for other scientists, particularly developmental
biologists who are trying to understand how the cells of an embryo
arrange themselves into patterns that become the various body parts of a
mature organism. In fruit fly embryos, for example, the first cells are
thought to differentiate into the head, abdomen and other parts based on
the concentration of chemical signals that are emitted from the ends of
the embryo.
In addition to conducting laboratory experiments, Weiss and colleagues
are creating computer models of their engineered systems, which allow
them to study how small modifications would affect the ultimate behavior
of the organisms. So far, said Weiss, the experimental results have
matched the computer models fairly closely, but the goal is to have a
mathematically exact description of how each component works.
"One of the nice things about synthetic biology is that because we built
the network from scratch, we should be able to model all the important
details," he said. At some point in the future, he said, scientists will
be able to choose a behavior they want from cells, and a computer
program will create a genetic circuit to accomplish the task. "Then we
can do an experiment to see if the community of cells is behaving as we
desire. That is going to have a tremendous number of applications."
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