Jheni Osman is a science journalist and presenter of
SciTech Voyager. Her books include 100 Ideas That Changed
The World and The World’s Great Wonders.started to produce oxygen by photosynthesis,
which led to the development of using oxygen
to generate energy.
Before the GOE, microbes had to get their
energy from elsewhere, and one source was
minerals. Indeed, one theory for how life
developed from the primordial soup of early
Earth was that it developed on mineral surfaces
that concentrated biological molecules and
catalysed reactions. The discovery that these
microbes can transport electrons into their cells
from mineral surfaces could fill in the missing
link in that theory. If that was the case, then it
provides us wit h clues as to how life could exist
on other oxygen-deficient planets.
“While the surface conditions of many
planetary bodies seem inhospitable, it is
possible t hat life eit her used to exist, or now
exists, underground or in massive ice shells,”
says El-Naggar. “Electron transfer is not an
Earth-centric notion, but it’s fundamental to all
of life’s energetics. Perhaps it holds the key to
discovering evidence of life on other planets!”
Astrobiologist and extremophile-guru Prof
Lewis Dartnell, from the University of
Westminster, agrees that these microbes could
exist anywhere in the cosmos, even as close to
home as the Red Planet: “By stripping electrons
directly of f metals in rocks, such microbes
could have a ready source of energy pretty much
anywhere – even on Mars, where there are
plenty of iron-containing minerals and pockets
of liquid water underground. In fact, most life
forms in the Galaxy might turn out not to be
sunbat hers like t he majority of su rface life on
Earth, but to be electron-munchers!”Research Facility in South Dakota. They are
writing up the results of that research right
now. “We don’t yet understand the movement of
electrons in biology as well as we understand
them in metals or semiconductors,” says
El-Naggar. “Yet look at the amazing
developments of our digital age that were
enabled by an understanding of how electrons
move in ‘hard materials’.”
Microbes that transfer electrons have already
been used for tasks like degrading toxic and
industrial waste, and recovering metals.
Scientists are now looking at how to harness
microbial electron transfer to synthesise
nanomaterials, and are working on technologies
thatusemicrobestogenerateelectricity.
But, crucially, El-Naggar and his team believe
that their research could reveal clues as to how
lifedevelopedonEarthandhowitcouldhave
evolved on other planets.HUNTING FOR ALIENS
Everyday,eachofusbreathesinandoutaround
20,000 times. We take it for granted that there is
oxygen in the atmosphere. But billions of years
ago breathing wouldn’t have been possible, as
oxygendidnotexist.About2.3billionyears
ago, Earth’s atmosphere radically changed
in composition. In this so-called ‘Great
Oxygenation Event’ (GOE), marine
cyanobacteria, also known as blue-green algae,“Electron transfer is
fundamental to all of life’s
energetics. Perhaps it holds
the key to discovering life
on other planets!”
BELOW LEFT: New York
State’s Oneida Lake is
where Shewanella, one
of the original
electron-eating
microbes, was
discovered in the 1980s
BELOW RIGHT: The
long, hair-like
structures on
Shewanella are an
important part
of its electron
transfer system