Scientists have identified a group of microbes belonging to the kingdom of Archaea, but with genes similar to the ones found in eukaryotes. The new discovery could have enabled archaea microorganisms to evolve into more complex eukaryotic cells. This gives support to the hypothesis that maintains that archaea are the common ancestors of eukaryotes. This breakthrough is the most important scientific finding about the questions regarding the evolution of simple life forms (archaea) into more complex ones (eukaryotes) that has been made in recent years.
The Tree of Life
Life forms are classified into three distinct groups-archaea, bacteria and eukaryotes, in the phylogenetic Tree of life and the new finding helps fill the gap between archaea and eukaryotes. Achaea and bacteria are microorganisms that belong to the group of prokaryotes due that they do not possess a nucleus, while eukaryotes include fungi, protist, plants and animals, including humans. Archaea and eukaryotes have been considered very close related due to their similarities in gene structure; however, it was not clear whether they shared a common ancestor or if eukaryotes had originated directly from archaea.
The discovery
Scientists made this important finding while studying the genomic diversity in a mid-Atlantic hydrothermal vent known as Loki´s Castle, where they assembled the genomic sequence of Lokiarchaea.
They found that nearly 175 predicted proteins within these microbes matched eukaryotic proteins taking part in phagocytosis, cell and membrane formation. This revealed that eukaryotes fitted very well within this group of archaea rather than just being a branch of it. The presence of various genes with functions involved with the cellular membrane point to a common ancestor for the origin and evolution of eukaryotes.
Origin of eukaryotic cells
Based on Eocyte hypothesis eukaryotes originated from prokaryotic Crenarchaeota, a phylum within the archaea. This is supported due that the ribosomes in the Crenarchaeota are more related to those of eukaryotes than to bacteria or euryarchaeota-second major kingdom of archaea. The general idea is that eukaryotes originated from prokaryotes, as prokaryotes are simpler organisms that are related to the origin of life.
There is no real consensus about the processes that gave origin to the first eukaryotic cell. The most accepted theory for the origin of the first eukaryotic cell implies endosymbiosis (combination of at least two prokaryotic organisms).
