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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.
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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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