Living Asgard archaea extended and retracted their protrusions and crawled across glass in observations made without oxygen. Inhibiting actin, a protein involved in the cellular skeleton, suppressed the movement. The observations give researchers a way to study behaviours relevant to complex-cell origins in living microbes. They concern modern organisms related to the lineage implicated in that ancient transition.
Live observations show Asgard archaea extending and retracting their protrusions while crawling across surfaces. The microbes are closely related to the archaeal lineage implicated in the origin of complex cells. The newly reported behaviour provides an experimental way to examine cellular features relevant to that evolutionary transition.[1], [2]
The researchers filmed living organisms in an oxygen-free environment, using a Lokiarchaeon cultivated in Vienna and a Heimdallarchaeon cultivated in Japan. Both changed shape repeatedly and used thin appendages to attach to glass and explore its surface. Earlier electron-microscope images had shown elaborate protrusions but could not reveal how they moved. Watching living cells makes extension, retraction and movement visible through time.[1]
Actin inhibitors suppressed the dynamic behaviour, suggesting that an actin-based cellular skeleton helps control it. Actin also participates in shape changes and movement in complex cells. Models of eukaryotic origins propose an ancient partnership between a bacterium and an archaeal ancestor, from which mitochondria emerged. These observations concern living modern microbes: they offer evidence about possible cellular capacities, while the ancient partnership itself remains an evolutionary reconstruction.[1]
