TACK Superphylum and Lokiarchaeota Evolution: Dissecting the Ecology and Evolution of Archaea to Elucidate the Prokaryote to Eukaryote Transition

Project Information

TACKLE

Grant agreement ID: 695192

DOI

10.3030/695192

Project closed

EC signature date 28 July 2016

Start date 1 August 2016

End date 31 July 2022

Funded under

• EXCELLENT SCIENCE - European Research Council (ERC)

Total cost

€ 2 500 000,00

EU contribution

€ 2 500 000,00

Coordinated by

UNIVERSITAT WIEN
Austria

Periodic Reporting for period 4 - TACKLE (TACK Superphylum and Lokiarchaeota Evolution: Dissecting the Ecology and Evolution of Archaea to Elucidate the Prokaryote to Eukaryote Transition)

Reporting period: 2021-02-01 to 2022-07-31

Summary of the context and overall objectives of the project

Archaea arose as one of the earliest life forms on Earth probably at about the same time as Bacteria. They have unique cell membranes and many of their cellular machineries are primordial versions of those in complex multicellular life forms (Eukaryotes). This project investigated two lineages of Archaea that can give clues to some of the most fundamental questions in biology: how did organisms expand from hot into moderate and cold environments on the early Earth and what kind of archaeon led to the evolution of Eukaryotes by incorporating a bacterium (which later evolved into mitochondria) into its cell. Without this event, no complex life forms would exist on Earth.
To address these questions it was a major objective of this project to cultivate and study organisms of two crucial lineages: Lokiarchaea of the new phylum Asgardarchaeota that are the closest known living relatives to Eukaryotes and thermophilic Thaumarchaeota from hot springs whose descendants have radiated into moderate environments on Earth.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

Novel habitats of Asgardarchaeota were discovered and well and stably growing enrichments of the lineage Lokiarchaeia were obtained. Their cells revealed an unprecedented cellular and cell wall complexity that shows the evolutionary emergence of actin-based cytoskeleton long before the emergence of Eukaryotes and a unusual and diverse cell wall that might particularly well interact with its biotic and abiotic environment. A thermophilic ammonia oxidizing Thaumarchaeote was obtained in pure culture and together with 38 further Thaumarchaeota genomes was used to reconstruct the evolution and ecological adaptations of this group into moderate environments. This revealed an enormous repertoire of proteins to cope with oxygen stress, apparently to alleviate the elevated amounts of oxygen in environments of decreasing temperature.
Our work was published in 15 peer-reviewed publications and presented on 3 conferences. At least 6 further publications are currently in preparation and more are expected to come.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The collaboration with a group at ETH Zurich experienced in cryo-EM and other imaging techniques has allowed to get unprecedented insights into features of the cultivated Lokiarchaeote that have never been seen before. Since this enrichment is the first of its kind that reaches high cell densities, it representes a tractable organism for many investigations to come, including metabolic reconstructions, identification of cell wall components, cell division machinery and other components that will shed light on the early evolution of machineries which led to the emergence of eukaryotes.

Sampling on top of the volcano in Vulcano island, Liparic islands

Researchers walking by a volcano crater in Etna, Sicily