The earliest cells harnessed energy through geochemical reactions, a process that LMU researchers have now successfully replicated in the lab.
The earliest ancestor of all life on Earth likely thrived in warm environments, relied on hydrogen for energy, and produced methane as a byproduct. Researchers at LMU Munich have reached this conclusion through fossil evidence and genetic analyses that allowed them to reconstruct ancient metabolic pathways. One of these pathways, the relatively simple acetyl-CoA pathway, still exists in many microorganisms today.
To better understand the metabolism of what were likely among the first living organisms on Earth, a research team led by Professor William Orsi from LMU’s Department of Earth and Environmental Sciences conducted laboratory simulations mimicking early Earth conditions, dating back 4 to 3.6 billion years. These simulations replicated aspects of modern hydrothermal vents known as “black smokers” on the ocean floor. However, a key difference was that the ancient oceans contained much higher levels of dissolved iron.
Strong growth without any nutrients
In the laboratory experiment, the researchers produced miniature versions of such “black smokers.” As it happens naturally at the seafloor, iron and sulfur geochemical reactions took place at high temperatures, forming iron sulfide minerals such as mackinawite (FeS) and greigite (Fe3S4) in a process that produced hydrogen gas (H2).
In these “chemical gardens,” the single-celled archaean Methanocaldococcus jannaschii was not only able to thrive, but positively exceeded the expectations of the researchers: “As well as overexpressing some genes of the acetyl-CoA metabolism, the archaeans actually grew exponentially,” explains Vanessa Helmbrecht, lead author of the study, which has now been published in the journal Nature Ecology & Evolution. “At the beginning, we expected only slight growth, as we did not add any extra nutrients, vitamins, or trace metals to the experiment.”
The single-celled organism thus proved highly adept at utilizing the hydrogen gas produced by the abiotic precipitation of iron sulfides as an energy source.
Isolated from the sediment of hydrothermal vents on the ocean floor, the hyperthermophile microbe Methanocaldococcus jannaschii serves as a model organism for methanogenesis via the Acetyl-CoA metabolic pathway. It is an organism that is adapted to extreme conditions: “For the cultivation, we were given access to the state-of-the-art facilities in the Archaea Center at the University of Regensburg, where Professor Dina Grohmann and Dr. Robert Reichelt kindly supported us. This was very important for preparing the experiments in the chemical gardens,” says William Orsi.
Oldest metabolic process in evolutionary history
In the chemical gardens, the cells always remained in direct proximity to the mackinawite particles. This aligns with fossil evidence, where some geological deposits of such minerals from the early history of the Earth contain fossil traces of the first microbial life.
The researchers conclude from the study’s results that chemical reactions during the precipitation of iron sulfide minerals around four billion years ago generated sufficient energy for the survival of the very first cells and thus laid the foundations for the hydrogen-dependent metabolism of the first microbes on the young Earth.
Accordingly, this form of methanogenesis based on hydrogen produced inorganically through chemical reactions is the oldest known form of energy generation in evolutionary history.
Space – the next frontier
The LMU geobiologists are now asking the question as to whether the metabolic processes they observed might not also take place outside our planet, and therefore whether there could be extraterrestrial habitats for archaeans – such as on Enceladus.
NASA already treats this moon of Saturn as a candidate for possible life, because scientists suspect the presence of hydrothermal activities between its rocky core and a liquid ‘soda ocean’ beneath its icy crust. “In our next study, we will simulate the conditions of Enceladus in the lab and test whether archaeans are capable of surviving and growing there,” says Helmbrecht.
Reference: “Simulated early Earth geochemistry fuels a hydrogen-dependent primordial metabolism” by Vanessa Helmbrecht, Robert Reichelt, Dina Grohmann and William D. Orsi, 30 April 2025, Nature Ecology & Evolution.
DOI: 10.1038/s41559-025-02676-w
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3 Comments
This is wild and amazing 🌌
The idea that scientists are reviving 4-billion-year-old reactions that could mirror how life began—on Earth or elsewhere —is blowing my mind.
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Were aligned with another planet. Signal and electricity has made transition and transporting possible. It applies in àn execintial form.yet to understand there has been foreign life to earth that has traveled here is just a possibility that is probably. In my own opinion. Think on how 3rd world county practices can extract all matter from a being and Utilize it to create and heal. Where did that approach begin and culminate from? Before the use of frequency electricity and concentration of temperature or signals?