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Bioengineers go retro to build a calculator from living cells
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16 May 2013, 9.13am EST
Bioengineers go retro to build a calculator
from living cells
Akshat Rathi
Science and Technology Editor, The Conversation
I N T E R VI E WE D
Chris Myers
Professor of Electrical and Computer Engineering, at University of Utah
Rahul Sarpeshkar
Professor of Electrical Engineering and Computer Science at Massachusetts Institute of
Technology
Scientists in the US have
developed a calculator from
living cells, using
old-fashioned analog
programming. Their hope is
that the technology could be
used in the future to program
cells to kill cancer.
Researchers have previously
built electronic circuits using
living cells. They achieved
this by forcing living cells to
behave in binary (digital)
systems. But this is not
energy efficient. And many
It won’t look quite like that, though. Josef Stuefer
cells are required to implement simple functions that transistors, the basic units of electronic
circuits which are ten times smaller than a cell and more reliable, can perform.
5/18/2013 11:31 AM
Bioengineers go retro to build a calculator from living cells
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http://theconversation.com/bioengineers-go-retro-to-build-a-calculator-f...
Instead analog technology, which uses not just two states like digital but many, could be used
to make cells do more complex tasks. Rahul Sarpeshkar, of the Massachusetts Institute of
Technology, realised that chemical reactions inside a living cell are also analog in nature.
Chris Myers at the University of Utah, who like Sarpeshkar is an electrical engineer working
on biological systems agrees. “Natural systems are more analog than digital,” he said. “They
are also a million times more power efficient than our electrical systems despite using very
poor components that produce lots of noise.”
Sarpeshkar, whose work has been published in the journal Nature this week, chose the
bacteria Escherichia coli, commonly known by its abbreviation as E. coli, to make his
calculator. For building it, he needed to create a way to input numbers, a program to execute
the calculations and a way to count the output. All three of those functions would occur in
living cells via chemical reactions.
The program for performing calculations was coded in synthetically made plasmids, which are
circular DNA molecules, and injected into the bacteria. These plasmids, also called genetic
circuits, have the ability to turn certain genes on or off. This starts a cascade of chemical
reactions, eventually leading to the production of proteins.
Sarpeshkar’s E. coli cells were designed to produce proteins tagged with a fluorescent dye in
response to the plasmids. These proteins could then be “counted” based on the amount of
light they emitted when a laser activated the dye. Their calculator could perform addition,
division and power-law computations.
Sarpeshkar’s aim is not to build computers using cells. That would be an inefficient use of the
technology. Instead, Sarpeshkar said, “In the future, we may build more complex circuits that
‘compute’ whether a cell is cancerous or not and destroy it if it is.”
There have been preliminary studies where genetic circuits put into bacteria can communicate
within a population of cells. That population can then sense their environmental condition and
decide to perform a response. This means Sarpeshkar’s plan to kill cancer cells using cells
that can compute may not be as far-fetched as it might seem.
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5/18/2013 11:31 AM