As the world turns to green hydrogen and other renewable energy sources, scientists have discovered that archaea, the third life form after bacteria and eukaryotes, have been producing energy using hydrogen gas and “ultra-minimal” enzymes for billions of years. In particular, an international team of researchers discovered that at least nine species of archaea, a domain of single-celled organisms without internal membrane structures, produce hydrogen gas using enzymes thought to exist only in two other forms of life.

They noticed that archaea not only have the smallest hydrogen-using enzymes compared to bacteria and eukaryotes, but their hydrogen-consuming and producing enzymes are also the most complex yet characterized. Small and powerful, these enzymes appeared to allow archaea to survive and thrive in Earth’s harshest environments with almost no oxygen.

“Humans are just starting to think about using hydrogen as an energy source, but archaea have been doing it for a billion years,” says Pok Man Leung, a microbiologist at Monash University in Australia who led the study. “There is now an opportunity for biotechnologists to draw inspiration from these archaea for industrial hydrogen production.”

Hydrogen is the most abundant element in the universe and is used worldwide to make fertilizers and other chemicals, metal processing, food products, and fuel refining. But the future of hydrogen lies in energy storage and steel production, which can be produced with zero emissions by using renewable energy to convert materials such as water into hydrogen.

Microorganisms produce and emit hydrogen gas (H).₂) for completely different purposes, mainly to shed excess electrons produced during fermentation, when organisms obtain energy from carbohydrates such as sugar without oxygen.

Enzymes used to consume or produce H_2, They are called hydrogenases, and they were first studied extensively on the tree of life just eight years ago. Since then, the number of known microbial species has increased significantly, especially archaea that lurk in extreme environments such as hot springs, volcanoes, and deep-sea springs.

But most archaea are known only from fragments of genetic code found in these environments, and most have not been cultured in the laboratory because it is too difficult to do so. Monash University microbiologist Chris Greening and colleagues looked for a gene that encodes part of one type of hydrogenase, a fast-acting hydrogenase. [FeFe]in a cluster of more than 2,300 archaeal species listed in the global database.

They then tasked Google’s AlphaFold2 with predicting the structure of the encoded enzymes and expressing these enzymes in bacteria. Escherichia coliTo test whether these genes are truly functional and produce hydrogenases that can catalyze hydrogen reactions in surrogate hosts.

“Our discovery brings us closer to understanding how this important process led to the emergence of all eukaryotes, including humans,” says Leung.

Eukaryotes are organisms whose cells contain a nucleus and membrane-bound organelles such as mitochondria and other useful cellular factories.

It is believed that all eukaryotes arose from the union of anaerobic archaea and bacteria billions of years ago. A second, much later endosymbiosis gave rise to the ancestor of plants with chloroplasts. Greening, Leung and colleagues find genetic instructions for hydrogenases [FeFe] Research was conducted on nine types of archaea and confirmed that they were indeed active in these microorganisms; This confirmed that three out of three domains of life use such enzymes to produce hydrogen.

But unlike bacteria and eukaryotes, further analysis revealed that archaea form “remarkable hybrid complexes” by combining two types of hydrogenases for their hydrogen production needs.

“These findings reveal novel metabolic adaptations of archaea that are simplified catalysts of H2.”₂ for the surprisingly intertwined evolutionary history between biotechnological development and the two major H-metabolizing enzymes.₂“, the team writes in the article.

But most of the cataloged archaeal genomes analyzed in this study are incomplete, and who knows how many species remain to be discovered? It is likely that archaea have other ingenious ways of obtaining energy that we have not yet discovered. The study was published on: Cell.