Ancient energy sources: Microbiologists decipher life in the past

Ancient energy sources: Microbiologists decipher life in the past

An interdisciplinary team of microbiologists and geologists has made significant progress in studying the earliest life forms on Earth. In a newly published article in the journal Nature Ecology & Evolution, the scientists document their laboratory experiments that simulated conditions that existed on Earth around four billion years ago. The focus of the study was on “black smokers” – hydrothermal vents that occur in the depths of the oceans. This environment may have played a crucial role in the emergence of life because it harbors unique chemical processes.

In the experiments, the researchers created so-called “chemical gardens” that represent miniature versions of the black smokers. These artificial structures make it possible to recreate chemical reactions that occur in the deep sea, particularly the reaction between iron and sulfur that leads to the formation of iron sulfide minerals. This produces hydrogen gas (H2), a potential energy source for microorganisms. This hydrogen production may have been important to support microbes that need it to produce methane.

Growth of archaea in simulated environments

A central concern of the study was to understand whether the hydrogen gas produced in the laboratory is sufficient to enable the growth of methanogenic archaea. These special microbes are capable of producing methane, providing clues to the earliest forms of life. The team tested the growth of the methanogenic archaea under oxygen-free conditions in the Chemical Gardens.

Methanocaldococcus jannaschii was chosen as a model organism for the experiments. The results were revealing: the archaea showed exponential growth and overexpressed genes responsible for acetyl-CoA metabolism. This ability of microbes to use hydrogen gas as an energy source demonstrates the adaptability of early life forms to extreme environments.

Significance of the results for understanding the early Earth

The research shows that the cells remained close to mackinawite particles, consistent with geological findings made in ancient hydrothermal vents. This discovery suggests that chemical reactions that occur during the precipitation of iron sulfide minerals generated sufficient energy for the first cells to survive. The authors of the study argue that this form of hydrogen methanogenesis may represent the evolutionarily oldest known method of producing energy.

By combining experimental results and geological evidence, this study contributes to the overall understanding of the emergence of life on Earth. The findings could also provide the basis for future research into life in extreme environments on other celestial bodies. Further information on the background and details of this research can be found on the website of University of Regensburg, IMW Mainz and Nature.com to find.