Biotechnologists now have the opportunity to take inspiration from these archaea to produce hydrogen industrially."

At the very top of the pyramid of life, there are three “domains” of life: eukaryotes (which animals, plants, and fungi fall into), bacteria, and archaea. Archaea are single-celled organisms that can live in Earth’s most extreme environments. The most widely accepted scientific theory also suggests that eukaryotes, such as humans, evolved from a very ancient lineage of archaea merging with a bacteria cell through exchanging hydrogen gas.

“Our finding brings us a step closer to understanding how this crucial process gave rise to all eukaryotes, including humans.”

The archaea making these hydrogen-using enzymes were found in many of Earth’s most challenging environments, including hot springs, oil reservoirs, and deep beneath the seafloor.

These hydrogenases were thought to be restricted to only two “domains” of life: eukaryotes and bacteria. Here, the team has shown that they are present in archaea for the first time and that they are remarkably diverse in their form and function.

Not only do archaea have the smallest hydrogen-using enzymes, but they also have the most complex hydrogen-using enzymes.

The paper shows some archaea have the smallest hydrogen-producing enzymes of any life form on Earth. This could offer streamlined solutions for biological hydrogen production in industrial settings.