Electric Bacteria Eat Electrons
July 18, 2014 | by Janet Fang
When we eat, our cells break down
sugars, while their excess electrons flow through a series of chemical
reactions until they’re passed onto oxygen. This process generates the energy
molecule ATP, vital to nearly all living things. "Life's very clever,” Kenneth Nealson from the University of Southern
California says. "It figures out how to suck
electrons out of everything we eat and keep them under control."
Not too surprisingly then, there are
bacteria out there that eat and excrete electrons -- and as it turns out, they’re
everywhere.
Years ago, researchers discovered two
types of electric bacteria, Geobacter and Shewanella,
which use energy in its naked, purest form: electrons harvested from the
surface of rocks and minerals. Now, scientists show that many more electric
bacteria can be fished out of rocks and marine mud by baiting them with a bit
of electrical juice, New Scientist reports.
"Electrons must flow in order for
energy to be gained,” Nealson explains. “This is why when someone
suffocates another person they are dead within minutes. You have stopped the
supply of oxygen, so the electrons can no longer flow."
Electric bacteria, however, have done
away with sugary middlemen.
Nealson and colleagues have grown
electric bacteria on battery electrodes, keeping them alive with electricity
and nothing else. (In humans, that’d be like powering up by shoving our fingers
in a socket.) The team collected seabed sediment and inserted electrodes inside
of it. Applying a slightly higher voltage than the sediment’s natural voltage
results in an excess of electrons -- which bacteria in the sediment eat. With a
slightly lower voltage, the electrode becomes eager to accept electrons; in
this case, the bacteria breathe electrons onto the electrode, which
generates a current. "Basically," Nealson says, "the idea is to
take sediment, stick electrodes inside and then ask 'OK, who likes this?'"
In unpublished work, the USC scientists
have identified up to eight different kinds of bacteria that consume
electricity, and they’re all very different from each other.
A handful of other researchers are also
working on electric bacteria. Daniel
Bond’s team from the University of Minnesota in St. Paul is
growing bacteria that harvest electrons from iron electrodes. Lars Peter Nielsen and his colleagues at Aarhus
University in Denmark have found that tens of thousands of
electric bacteria can join together to form “daisy chains” that carry electrons
over several centimeters (huge distances for a bacterium). Here’s a video of
electric bacteria forming their “microbial nanowires.”
Researchers hope to use these bacteria
to probe fundamental questions about life, such as the bare minimum of energy
needed to sustain life. Electric bacteria have practical uses too, such as
cleaning up contaminated groundwater while powering themselves using their
surroundings.
[Via New Scientist]
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