Without ultraviolet rays, meteorite impacts, or volcanic eruptions, life on Earth originated from...

How did the first chemical reactions at the origin of life begin? What was their energy source? Researchers at the University of Düsseldorf (HHU) in Germany have reconstructed the metabolism of LUCA, the last common ancestor before the divergence of modern organisms. They have discovered and identified the long-sought source of energy required to drive these reactions forward: hydrogen, which had been hiding in plain sight.

Metabolism of LUCA. The team investigated 402 biochemical reactions required for the biosynthesis of the molecular building blocks of life. Each circle represents a reaction and its color represents the energy released by each reaction. Green means energy is released and purple means energy is required. Image credit: HHU / Jessica Wimmer

In the laboratory, Professor William Martin's team at HHU's Institute of Molecular Evolution conducted chemical experiments using catalysts and conditions found in hydrothermal vents on the seafloor to study the reaction between hydrogen and carbon dioxide. They developed a form of molecular archaeology on computers that allowed them to discover many different traces of primitive life preserved in proteins, DNA and chemical reactions in modern cells.

Instead of looking at genes, the researchers looked at the information contained in the chemical reactions of life itself. They identified 402 metabolic reactions that have remained virtually unchanged since the origin of life about 4 billion years ago. Because these reactions are common to all cells, they were also present in LUCA.

In the most primitive modern cells, some compounds were synthesized from simple molecules present in the modern environment that were also present in hydrothermal vents on the early Earth: hydrogen, carbon dioxide and ammonia - representing the metabolic network of LUCA.

The results of the study published in Frontiers in Microbiology show that LUCA's metabolism does not require external energy sources, such as ultraviolet light, meteorite impacts, volcanic eruptions, etc. On the contrary, in the typical environment of many modern submarine hydrothermal vents, the energy required for metabolic reactions to proceed comes from metabolism itself. In other words, almost all of LUCA's metabolic reactions release energy by themselves: the energy of life comes from life itself.

The researchers explained that in the "Lost City" hydrothermal field environment that produces hydrogen in the middle of the Atlantic Ocean, about 95%-97% of LUCA metabolic reactions can proceed spontaneously without any other energy. In the dark abyss of the hydrothermal system, hydrogen is "chemical sunlight." Modern energy technology is studying the use of hydrogen properties that are exactly the same as life. It's just that life has 4 billion years of "hydrogen technology experience", while humans are just getting started.

Editor-in-Chief's Comments

LUCA, the common basic ancestor of existing organisms, is an entity that has left no fossil traces. The hydrothermal ecosystem is located on the dark and cold ocean floor. It is not lonely there, but even full of vitality, with organisms such as tube worms and sea anemones active there. The researchers used the catalysts and conditions found in the seafloor hydrothermal vents to conduct chemical experiments, identified some metabolic reactions that have hardly changed since the origin of life, and inferred that LUCA's metabolism does not require external energy. Like the hydrothermal vent ecosystem, they use hydrogen energy. This discovery not only solves the mystery of the origin of life, but also provides humans with an advanced and original idea for the use of hydrogen energy - bionics.

Source: Science and Technology Daily

◎ Science and Technology Daily reporter Zhang Mengran

Editor: Wang Yu

Review: Yue Liang

Final review: Liu Haiying