found in South
Alive and well, deeper underground
than any other life has gone before
Worms in South African mines extend limits of habitability
“If it can work its way through the
fractures and keep on picking up good-
ies, it doesn’t really care about how deep
it is,” says Onstott. “Given enough time,
these organisms will get there.”
Nematodes can live with hardly any
oxygen; the limiting factor to their sur-
vival in the deep is probably the high
temperatures found there, Borgonie
says. In lab cultures H. mephisto survived
temperatures up to 41° Celsius.
But R. John Parkes, a deep-biosphere
expert at Cardiff University in Wales,
questions whether drilling boreholes
for the mines altered the subsurface
environment somehow, perhaps by
introducing more oxygen or otherwise
providing an artificial environment in
which nematodes could thrive.
In a few months Borgonie will return to
South Africa to hunt for new nematodes
in mine water that he has been collecting
and filtering for two years— far longer
than the 24-hour samples he reports on
in the new study.
Karsten Pedersen, a microbiologist at
the University of Gothenburg in Sweden,
says he is convinced by the hard work the
team did to rule out the possibility of surface contamination. Pedersen has found
yeast up to 450 meters deep in Swedish
granite, the previous record holder for
complex subterranean life, but hasn’t
yet looked for nematodes there. More
research is needed, he says, to confirm
whether the South African deep worms
are a rarity or the rule. s
By Alexandra Witze
Tiny worms appear to live in rock fractures up to 3. 6 kilometers underground,
researchers have reported, far deeper
than anyone has encountered complex
organisms before. The discovery of nematode worms in three South African gold
mines underscores the fact that Earth’s
biosphere reaches well into subterranean
realms. It also suggests that habitable
environments may exist buried way
down on other planets, such as Mars.
Worm specialist Gaetan Borgonie
and his colleagues present their findings, which include a new nematode
species named after Faust’s devil
Mephistopheles, in the June 2 Nature.
Nematodes are an incredibly diverse
group encompassing numerous intestinal parasites and the widely studied
laboratory roundworm C. elegans.
Over the last few decades, researchers have found plenty of bacteria and
other single-celled creatures thriving
deep underground. But “to actually go
out and start looking for multicellular organisms is such a game changer.
Nobody in their right mind would think
they were down there,” says team member Tullis Onstott, a geomicrobiologist
at Princeton University.
But Borgonie, of the University of
Ghent in Belgium, thought there just
might be enough food, water, oxygen
and other nematode necessities to keep
worms alive deep in Hades’ realm. So he
traveled to South Africa to collect water
and soil samples from six boreholes.
In the deepest, 3. 6 kilometers down at
the Tau Tona gold mine, Borgonie found
traces of nematode DNA in water oozing
from rock fractures. Much shallower,
900 meters down the Driefontein gold
mine, he found actual nematodes of
The discovery of the worm
Halicephalobus mephisto 1. 3 kilometers deep in a
South African mine suggests that complex life can thrive deeper in the Earth
than scientists had suspected.
two known surface species. And at the
middle depths, 1. 3 kilometers down in
the Beatrix gold mine, he uncovered an
odd-looking, living female nematode.
Back in the laboratory, Borgonie laid
that worm under a microscope. “It was
like an intensive care unit — I was looking
at it every hour,” he says. “The only thing
I wanted it to do was lay an egg.”
It did. Eight of them. Borgonie had
the start of a worm dynasty. About half
a millimeter long, the nematodes are
different enough from other species to
warrant their own name: Halicephalobus
To make sure the worms weren’t accidentally brought down by mine workers,
the researchers ran a series of painstaking tests. The studies showed that the
water in which the nematodes live is at
least several thousand years old.
Before that, Borgonie says, ancestors
of the newly found worms probably lived
on the surface. Over generations they
presumably slithered down, munching
bacteria along the way.
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