Tissue-Like Multicellular Development Triggered by Mechanical Compression in Archaea

The advent of clonal multicellularity is a critical evolutionary milestone, seen often in eukaryotes, rarely in bacteria, and - until now - never in archaea. We show that uniaxial compression induces clonal multicellularity in haloarchaea, forming tissue-like structures. These archaeal tissues are mechanically and molecularly distinct from their unicellular lifestyle, mimicking several eukaryotic features. Notably, archaeal tissues undergo a coenocytic stage followed by a tubulin-independent cellularization, orchestrated by active membrane tension at a critical cell size. Past cellularization, tissues are organized into two cell types - apical and basal scutoids - with junction elasticity akin to animal tissues, with actin and protein glycosylation as fiducial polarity markers. Our findings highlight the remarkable biophysical potential of convergent evolution in the emergence of multicellular systems across domains of life.