Science

Researchers draw portrait of eukaryotic ancestor

In the Paleoproterozoic era, about two billion years ago, eukaryotes appeared on Earth – a phylogenetic line of all living creatures that have cells with a nucleus. These single-celled creatures lived on a star very different from the one known to everyone. It was a planet with red waters punctuated by patches of exposed land. This very specific color has been associated with an event called the “Great Oxidation” which resulted in a spike in atmospheric oxygen due to the proliferation of cyanobacteria that produce this molecule through photosynthesis.

Most living creatures of that time could not consume oxygen, so it acted like a poison on the vast majority of living things, leading to mass extinction and at the same time turning the ocean red, oxidizing the iron particles that were there. Eukaryotes were perfectly adapted to this new environment as they could consume oxygen to produce CO2, but their exact origins are shrouded in mystery. However, many recent discoveries have shed light on several plausible scenarios.

In a study published in the journal Nature, researchers from the universities of Zurich, Switzerland, and Vienna, Austria, painted a portrait of one of the protagonists of the two scenarios that received the most recognition from the scientific community. They both have the same protagonists, archaea and bacteria, and come to the same conclusion: the emergence of a complex cell with a nucleus and organelles. In this publication, the researchers focused on the archaeal species Candidatus Lokiarchaeum ossiferum, which are part of the supertype Asgard.

2 scenarios with the same conclusion: eukaryogenesis

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