Deep-sea microbes called missing link for complex cellular life
By Will Dunham
WASHINGTON (Reuters) - Deep beneath the Atlantic Ocean between Greenland
and Norway, scientists have found microorganisms they call a missing
link connecting the simple cells that first populated Earth to the
complex cellular life that emerged roughly 2 billion years ago.
The researchers said on Wednesday a group of
microorganisms called Lokiarchaeota, or Loki for short, were retrieved
from the inhospitable, frigid seabed about 1.5 miles (2.35 km) under the
ocean surface not too far from a hydrothermal vent system called Loki's
Castle, named after a Norse mythological figure.
The discovery provides insight into how the larger,
complex cell types that are the building blocks for fungi, plants and
animals including people, a group called eukaryotes, evolved from small,
simple microbes, they said.
The Lokiarchaeota are
part of a group called Archaea that have relatively simple cells lacking
internal structures such as a nucleus. But the researchers found the
Lokiarchaeota share with eukaryotes a significant number of genes, many
with functions related to the cell membrane.
These genes would have provided Lokiarchaeota "with a
'starter-kit' to support the development of cellular complexity," said
evolutionary microbiologist Lionel Guy of Sweden's Uppsala University.
Archaea and bacteria, another microbial form, are together known as prokaryotes.
"Humans have always been interested in trying to find an
answer to the question, 'Where do we come from?' Well, now we know from
what type of microbial ancestor we descend," said Uppsala University
evolutionary microbiologist Thijs Ettema, who coordinated the study.
"Essentially, Lokiarchaeota represent a missing piece of
the puzzle of the evolution from simple cells - bacteria and archaea,
prokaryotes - to complex cells - eukaryotes, which includes us humans,"
Ettema added.
Earth's wide diversity of life would
have been impossible without this transition from rudimentary cells into
the more complicated ones seen in multicellular life. Microbial life
originated about 3.5 billion years ago. The first complex cellular life
came roughly 2 billion years ago.
How cellular complexity first developed has been one of the big puzzles of evolutionary biology, Guy said.
The Lokiarchaeota were retrieved from oxygen-starved
sediment layers during voyages of a Norwegian research vessel, said
microbiologist Steffen Jørgensen of Norway's University of Bergen.
While the Loki's Castle geothermal vents spew fluids
reaching about 570 degrees Fahrenheit (300 degrees Celsius) about 9
miles (15 km) away, the Lokiarchaeota's locale was desolate, pitch dark
and around the freezing point, Jørgensen added.
The research appears in the journal Nature.
(Reporting by Will Dunham; Editing by Mohammad Zargham)
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