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 stronauts may one day be able to use their spacecraft's
septic tank to keep in touch with ground control as long as they
have plenty of sugar. Scientists in Michigan have developed a
biofuel cell that creates a constant, low-power electricity supply
by feeding glucose to common bacteria such as E. coli.
 Biochemists
Gregory Zeikus and Doo Hyun Park at Michigan State University
in East Lansing have manipulated the bugs' metabolism to convert
them into tiny powerhouses. They have built a 0.6-volt biofuel
cell that can deliver currents of up to 17 milliamperes.
Bacteria normally
break down glucose to generate adenosine triphosphate the main
energy source for cells. This involves a flow of electrons, which
the researchers have tapped into by adding a chemical called
neutral red. Molecules of neutral red insert themselves into
the bacterial membrane, where they hijack the reaction's electron-transport
process, and shuttle electrons onto an electrode.
"It's
like an electric plug," says Zeikus. "You put it in
the cell membrane and put the cells in a cathode to make electricity."
The method isn't likely to be powering your CD player any time
soon, but Zeikus says it could be used as a backup method of
maintaining communications in remote areas such as space. There
is a bonus, too. Because some of the bacteria's energy is diverted
to producing electricity, they don't multiply as fast as usual,
leaving less sludge to dispose of.
Ziekus and
Park are not the only researchers exploring the electrical potential
of sugar-fed biofuel cells. Itamar Willner and his colleagues
in the chemistry department of the Hebrew University of Jerusalem
in Israel, for example, are using enzymes rather than bacteria
to make batteries that could be implanted in people's bodies.
Powered by blood sugar, the batteries could one day power pacemakers,
insulin pumps and prostheses. 
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