Scientists discovered Asgard archaea physically connected to bacteria by ultrathin nanotubes within stromatolite mats in Shark Bay, Australia. Using electron cryotomography, they visualized the nanometre-scale bridges and found evidence the microbes exchanged vitamins, nutrients and hydrogen. These findings offer a tangible, modern model for archaeon–bacterium partnerships that could have contributed to the origin of eukaryotic cells between 2.7 and 1.8 billion years ago.
Invisible Nanotubes Link Asgard Archaea and Bacteria — A Clue to How Complex Life Began
This Living Fossil Was the Key to the Rise of LifeKira-Yan - Getty Images
New research reports a striking physical and metabolic connection between an Asgard archaeon and a bacterium inside modern stromatolite microbial mats — a finding that offers a plausible model for the close partnerships that may have led to the first eukaryotic cells.
A Window Into Deep Time
For billions of years, life on Earth was dominated by prokaryotes: bacteria and archaea. Between roughly 2.7 and 1.8 billion years ago, scientists believe an archaeon and an alphaproteobacterium entered a close partnership through endosymbiosis, a union that eventually produced mitochondria and the cellular complexity of eukaryotes. How that partnership began remains actively debated.
Stromatolites and Living Fossils
Researchers studied stromatolites — layered structures created by cyanobacteria within microbial mats — that act as modern analogues of ancient microbial communities. The team collected samples from Shark Bay, Western Australia, where stromatolite fields preserve diverse, tightly packed microbial ecosystems.
What They Found
Scientists from the University of New South Wales, the University of Technology Sydney and the University of Melbourne isolated an Asgard archaeon identified as Nerearchaeum marumarumayae paired with a bacterium identified as Stromatodesulfovibrio nilemahensis. Using electron cryotomography — a high-resolution 3D imaging method — the team visualized ultrathin tube-like bridges, described as "nanotubes," that physically connected the cells at roughly one nanometre scale.
Beyond the structural link, analyses indicate metabolic exchange between the partners: vitamins, nutrients and hydrogen produced by one cell could be used by the other. This mutual exchange suggests a cooperative, metabolite-sharing relationship rather than a mere incidental contact.
Why It Matters
Although a modern example cannot prove the exact sequence of events that produced the first eukaryotic cell, these observations provide tangible evidence that archaeal–bacterial partnerships with both physical connections and metabolic complementarity can and do form in natural microbial mats. Such partnerships are a plausible mechanism that could have set the stage for endosymbiosis and eukaryogenesis on the early Earth.
"Stromatolites could be more than 'just' a cradle of life where early microbial life flourished," said Brendan Burns (University of New South Wales), senior author of the study. "They could also tell us how complex life first emerged … This could be a little model for how these kinds of partnerships started and ultimately formed eukaryotes."
The study was published in Current Biology and represents one of the first in situ observations of an Asgard archaeon linked to bacteria by ultrathin nanotubes, reinforcing hypotheses that metabolite sharing and intimate physical contact facilitated the emergence of cellular complexity.
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