1. As we recently joined BlueSky, we want to repost this story for all newcomers! We sat down with @radler92.bsky.social to get more insight into the unique videos from his recent preprint on Promethearchaeota (formerly Asgard archaea). doi.org/10.1101/2025... (Videos and info below)

There are currently only 5 cultivated Asgards and we know most about them from genomic data and some exquisite cryo-EM images. We were, however, interested in observing cell behavior with live cell microscopy!

In our recent preprint, we managed to establish anaerobic live imaging of Ca. Lokiarchaeum ossiferum, a member of Promethearchaeota (formerly Asgard archaea). Below are 4 examples (plus one of the newly cultivated HC1) of these fascinating microorganisms and what we are observing:

Video 1 (Dynamic protrusions) These cells (we call them lovingly Lokis) have a very characteristic shape: A central cell body with long protrusions. We find these protrusions to be unexpectedly dynamic; they grow and retract constantly.

Video 2 (Shapechangers) Not only are the arms dynamic, but also the cell shape is extremely plastic. The cells can rearrange from a spherical shape to form a stick like morphology in a matter of minutes! Such plasticity is unprecedented in the world of prokaryotes.

Video 3 (Moving Cells) When we looked closer, we found some that, after adhering to the glass, used their protrusions to migrate along the glass! This type of crawling motility is untypical of prokaryotes, as it didn’t seem to be dependent on Pili proteins, but rather these dynamic protrusions.

Video 4 (Actin Inhibition) We were able to stop these dynamics by inhibiting the internal Lokiactin (an ancient homologue of human actin) cytoskeleton. Rather than controlled protrusion growth and movement, the cells sway randomly, similar to the Inflatable tube man found next to car dealerships.

Video 5 (HC1) We were very happy to collaborate with the team of Hiro Imachi, who provided their recently cultivated Hodarchaeum Ca. M. peptidophilum, another member of the Promethearchaeota. We found these cells to be incredibly dynamic and rearranging their cell morphology, like the Lokis.

Thus, we suggest that these dynamics are a common feature of Promethearchaeota. The motility seems dependent on internal, actin filaments, which suggests than actin-based motility might not be an invention by eukaryotes but has emerged earlier during evolution.