In an article published in the journal “Nature”, an international team of researchers described the discovery of new microbes that constitute a missing link in the evolution of complex cells, those of eukaryotes. They were called Lokiarchaeota because they were found in a hydrothermal vent in the depths of the Atlantic Ocean between Greenland and Norway called Loki’s Castle.

Eukaryotic organisms, which include plants, animals and fungi, are made up of complex cells. There are also prokaryotes, single-celled organisms made up of cells that are small and simple. The difference between the two types of cells is remarkable because of the amount of structures present only in those of eukaryotes. The problem was how eukaryotes evolved from prokaryotes.

So far it seemed that there wereren’t organisms with characteristics intermediate between eukaryotes and prokaryotes anymore but a study of the DNA of the microorganisms found in the hydrothermal vents of Loki’s Castle showed that they still exist. These are bacteria that belong to the domain of Archaea, also known archaebacteria.

Archaea are considered prokaryotes for their cell characteristics but Lokiarchaeota, or Loki for short, possess genes found only in eukaryotes. They seem to be part of the superphylum called TACK (from the initials of the four phyla of which it’s composed: Thaumarchaeota, Aigarchaeota, Crenarchaeota and Korarchaeota).

According to Dr. Thijs Ettema of University of Uppsala, in Sweden, one of the main authors of the article, the similarities between eukaryotes and Lokiarchaeota show that they have a common ancestor that lived about two billion years ago. This ancestor may have possessed a kind of genetic starter kit that supported an increase in cellular complexity leading to the emergence of eukaryotic organisms.

The study of this team of researchers focused on microorganisms living in extreme environments, where you can find unique life forms. Areas such as ocean hydrothermal vents are difficult to reach and the bacteria difficult to get but the discovery of Lokiarchaeota shows that the choice was right.

The researchers intend to look for other organisms smiilar to Lokiarchaeota in other places such as the hot springs of Yellowstone National Park, in the USA, or those of New Zealand. The hope is to find bacteria with characteristics more similar to those of eukaryotes to find more information on the evolution of complex life forms.