Mankind’s missing microbe-link found in deep sea – study

Reuters / David Loh
The bed of the northern Atlantic Ocean is home to a previously unknown group of microorganisms that scientists suppose to be a link between the first simple cells and complex creatures, including human beings.

A team of Norwegian and Swedish scientists have recently discovered a group of microorganisms called Lokiarchaeota – or Loki – that may help them understand how primitive microbes developed into complex cell organisms or eukareotes, ranging from plants to animals including people.

Their findings, were published in the journal Nature on Wednesday.

Loki microorganisms were found on the seabed about 2.35 km from the surface of the ocean between Norway and Greenland, some 15 km from Loki's Castle – a field of active hydrothermal vents, named after one of the gods from Norse mythology.

Loki, the newly discovered type of archaea, which is a group of single-celled microorganisms, still share over 100 genes with eukaryotes. Those genes are responsible for such functions as deforming cell membranes. According to evolutionary microbiologist Lionel Guy of Sweden's Uppsala University, these genes could have been “a ‘starter-kit’ to support the development of cellular complexity”.

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"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," Thijs Ettema, Uppsala University evolutionary microbiologist and coordinator of the study, told Reuters.

"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.

While microbial life on our planet appeared about 3.5 billion years ago, the first complex cellular creatures emerged approximately 2 billion years ago. According to the authors of the study, “The origin of the eukaryotic cell remains one of the most contentious puzzles in modern biology.”

Microbiologist Steffen Jørgensen of Norway's University of Bergen told Reuters that the Lokiarchaeota were discovered during voyages of a Norwegian research vessel. The oxygen-starved sediment layers were “desolate, pitch dark and around the freezing point”.

"Ettema's team have certainly thrown the cat among the pigeons,"
Anthony Poole at the University of Canterbury in New Zealand, told New Scientist news magazine. "It's still 100 per cent archaeon, but the presence of genes we usually associate with eukaryote cell biology is absolutely fascinating."