• The vast web of life on Earth includes three major areas: archaea, bacteria and eukaryotes.

• Scientists at Monash University recently discovered hydrogen-producing enzymes in archaea that were thought to only exist in the other two orders.

• These archaeal enzymes, known as hydrogenases, are smaller and more complex than those found in the other two domains and could help biotech companies develop better and more efficient hydrogen energy systems.

There are an estimated 8.7 million Species, only a fraction of which have been scientifically identified. Despite this vast, fragmented tree of life, however, every living thing falls into one of three broad categories or “domains” – archaea, bacteria and eukaryotes.

All the usual things we think of as “life” – things like trees, fungi, and animals – are eukaryotes, meaning their cells contain a nucleus and other membrane-bound organelles. Archaea and bacteria, on the other hand, are prokaryotic, meaning they contain no such structures. While these two other domains may look similar under the microscope, there are a long list of differences which distinguish archaea from bacteria as well as from humans.

Since the discovery of archaea in the late 1970s, scientists believed that one difference between this third domain and other life forms was that these organisms do not produce hydrogen-utilizing enzymes called “hydrogenases.” A new study published this week in the journal cell says that this is not only not While this is true, archaea have actually been consuming and producing hydrogen for two billion years – a process that has allowed them to live in some of the most hostile places on Earth.

Understanding this process can also help shed light on the origin of all other life. The leading biological theory proposes that the first eukaryotes arose when a primordial species of archaea fused with a bacterial cell (also known as Endosymbiosis) via hydrogen gas exchange.

“Humans have only recently started thinking about using hydrogen as an energy source, but archaea have been doing so for a billion years,” said Bob Leung, a co-author of the study, in a press release. “Our discovery brings us one step closer to understanding how this crucial process led to the emergence of all eukaryotes, including humans.”

As part of the study, the research team examined the genomes of thousands of archaea, found hydrogen-producing enzymes, and then produced these enzymes in the laboratory for further study. They noticed that some of these archaea produced an enzyme called (FeFe)-hydrogenase.

This contradicts the idea that only the other two domains utilized this type of enzyme, and also highlights the fact that archaeal enzymes were both the smallest and most complex form of hydrogen-utilizing enzymes found in all three domains. This could have major implications as engineers continue to look for ways to use hydrogen as a green energy source.

“Industry currently uses valuable chemical catalysts to harness hydrogen. But we know from nature that biological catalysts can be highly efficient and resilient,” said Chris Greening, the study’s lead author, in a press release. “Can we use these to improve the way we use hydrogen?”

Amazingly, the discovery of a two billion-year-old process — linked to one of the least understood areas of life — could help pave a path to a much-needed zero-emissions future. While archaea can survive temperatures beyond boiling or freezing, many of us eukaryotes need slightly milder conditions.

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