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Deep-Sea Microbe is Missing Link in Evolution

May 07, 2015 12:43 PM EDT
hydrothermal vent field
Pictured: Image of a hydrothermal vent field along the Arctic Mid-Ocean Ridge, close to where 'Loki' was found in marine sediments.
(Photo : Centre for Geobiology (University of Bergen, Norway) by R.B. Pedersen)

Scientists have discovered a new deep-sea microbe that, as it turns out, represents a missing link in the evolution of complex life, according to new research.

Cells are the basic building blocks of all life on our planet. The cells of bacteria and other microbes, for example, are small and simple, whereas visible life - including plants, fungi, but also animals and humans - are generally made up of large, complex cell types. However, the origin of these complex cell types has long been a mystery to scientists - that is, until now.

This study, published in the journal Nature, provides a new understanding of how, billions of years ago, complex cell types evolved from simple microbes.

A team of researchers led by Uppsala University in Sweden discovered a new group of Archaea called the Lokiarchaeota (or 'Loki' for short), which is the missing link in the origin of eukaryotes.

When the group Archaea was first identified in the 1970s, researchers found that these cells, despite their small, simple nature, were more closely related to organisms with complex cell types - a group collectively known as eukaryotes. But how could the complex cell types from eukaryotes have emerged from the simple cells of Archaea?

"The puzzle of the origin of the eukaryotic cell is extremely complicated, as many pieces are still missing. We hoped that Loki would reveal a few more pieces of the puzzle, but when we obtained the first results, we couldn't believe our eyes. The data simply looked spectacular," Thijs Ettema, who led the scientific team, said in a press release.

"By studying its genome, we found that Loki represents an intermediate form in-between the simple cells of microbes, and the complex cell types of eukaryotes," he added.

When Loki was placed in the Tree of Life, this idea was confirmed.

"Loki formed a well-supported group with the eukaryotes in our analyses," said Lionel Guy, one of the senior scientists involved in the study from Uppsala University.

"In addition, we found that Loki shares many genes uniquely with eukaryotes, suggesting that cellular complexity emerged in an early stage in the evolution of eukaryotes," added researcher Anja Spang.

The name Lokiarchaeota came from the hostile environment close to where it was found, Loki's Castle, a hydrothermal vent system located on the Mid-Atlantic Ridge between Greenland and Norway at a depth of 2,352 meters (~7,700 feet).

These kinds of extreme environments are hotspots for many unknown microorganisms, and with new genomics techniques, researchers hope to find more clues about how complex cells evolved.

For more great nature science stories and general news, please visit our sister site, Headlines and Global News (HNGN).

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