1 August 2020 | New Scientist | 13MICROBES that have been
hibernating deep below the
Pacific Ocean since the reign
of the dinosaurs have been
revived in the lab. Some may be
100 million years old, perhaps
making them the longest-lived
life forms on Earth.
We already know that
microbes can survive deep
below our planet’s surface, even
though nutrients are generally
scarce. Biologists suspect that
the microbes enter a minimally
active mode to stay alive. But
whether they can emerge
unscathed has been unclear.
Now a team led by Steven
D’Hondt at the University of
Rhode Island and Yuki Morono
at the Japan Agency for Marine-
Earth Science and Technology
has studied about 7000
individuals of a bacterium found
living in mud 75 metres beneath
the sea floor, 5700-metres-deep
in the South Pacific Ocean.
“We didn’t know whether we
had fully functioning cells or
zombies capable of doing very
few things,” says D’Hondt.In the lab, the researchers
gave the microbes nutrients
laced with distinctive isotopes
of carbon and nitrogen. Within
10 weeks, these isotopes began
showing up inside the microbes,
indicating that they had begun
to feed like typical bacteria
(Nature Communications, DOI:
10.1038/s41467-020-17330-1).
That is remarkable
considering what the bacteria
have been through, says Jens
Kallmeyer at the GFZ German
Research Centre for Geosciencesin Potsdam. He says the mud in
which the bacteria were found
is capped by layers of silicon
dioxide that no microbe could
penetrate. This implies that the
microbial populations have
been trapped since the mud was
buried under the silicon dioxide
an estimated 101.5 million
years ago. Given that this mud
contains few nutrients, survival
must have been challenging.
“Nowhere else on Earth do you
find sediment as close to totallydead as this,” says Kallmeyer.
The microbes may be even
more astonishing than that.
Although they can probably
gather sufficient nutrition
from the mud to repair cellular
damage, it isn’t clear if the mud
contains enough nutrients to
fuel cell reproduction. “They
may have divided since they
were buried, or they may not,”
says Virginia Edgcomb at the
Woods Hole Oceanographic
Institution in Massachusetts.
“I don’t think anyone knows.”
If cell division is difficult
there, some of the bacterial cells
might be as old as the mud itself.
“I mention this possibility
in talks and it drives some
researchers nuts,” says D’Hondt.
Many biologists are unsettled
by the idea that individual
bacterial cells could survive
for 100 million years.
There have been a handful
of claims for even older
microbes on Earth. One
team claimed in 2000 to have
resurrected microbes trapped
inside 250-million-year-old
salt crystals, but some
researchers suspect that the
microbes were seen as a result
of sample contamination,
which is unlikely to be the
case in the new study.
Because the deep-sea
microbes must have patched
and repaired themselves
countless times, it is perhaps
down to philosophers to decide
whether any individual cell
really is 100 million years old.
D’Hondt believes they qualify.
“I sometimes use the metaphor
of my grandfather’s hammer,”
he says. “My grandfather gave
a hammer to my father and
my father gave it to me. We’ve
replaced the head twice and
the handle three times, but
it’s still the same hammer.” ❚Bacteria were
retrieved from the
South Pacific OceanLifeColin BarrasCH
RIS
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WB
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7000
Microbes taken from beneath
the ocean floor to be studiedRevived bacteria may
be 100 million years old
AN ULTRA-FAST camera has
captured a video of light as it
bounces between mirrors.
Although light isn’t normally
visible in flight, some photons from
a laser pulse will scatter off particles
in the air and can be picked up by
a camera. Using these photons to
recreate the pulse’s trajectory is
difficult, because by the time they
reach the camera, the pulse has
moved to a new location.Edoardo Charbon at the Swiss
Federal Institute of Technology in
Lausanne and his colleagues used
a camera with a shutter speed
of about a trillionth of a second
to take pictures and video of a
laser beam following a 3D path.
Knowing exactly how long the
pulse took to get to the camera,
along with the pulse’s trajectory
in a flat plane, allowed a machine
learning algorithm to reconstruct
the entire 3D path of the burst of
light (arxiv.org/abs/2007.09308).
This could be useful in chemistry,
says Marty Baylor at Carleton
College in Minnesota. “You could
watch light interacting with a
molecule in real time”, giving a more
detailed understanding of certain
chemical reactions, she says.
A similar method could also be
used to see around obstacles, says
Charbon. If you bounced a laser
pulse off a wall, then off an
obscured object around a corner
and back off the wall again before
capturing it, the algorithm could
potentially reconstruct an image. ❚This laser pulse appears as a white
line following a path between mirrorsPhysicsLeah CraneLight caught on
camera as it flies
through the airKA
ZUHIRO^ MORIM
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O^ ET^ AL.