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But for the first time, Ding and Hamm were able to show that the parasitic archaeon Candidatus Nanohaloarchaeum antarcticus does not contain all the lipids that his host Halorubrum lacusprofundi contains, but only a selection of them.

"Unlike its function in many eukaryotic cells, where actin is often associated with maintaining cell shape and facilitating movement, in our model archaeon Haloferax volcanii this actin homolog is crucial for the transition to disk-shaped cells," Pohlschröder says.

It's commonly understood that the first eukaryotic cells resulted from the fusion of an early form of bacteria with an archaeon, a single-celled organism similar to a bacterium.

Although many researchers think early eukaryotic cells arose after an archaeon engulfed a bacterium that became the mitochondria, they have struggled to figure out how other features of eukaryotes, such as their many internal membranes and organelles, evolved.

Under an existing protocol, the scientific community accepts a bacterium, or a prokaryote known as an archaeon, as real only if microbiologists grow the species in the lab and submit a pure “type” culture to at least two of the world’s facilities that keep microbes in perpetuity.