The Earth was not always the blue-green planet that we know today: The level of oxygen on the ancient Earth was about a million times lower than now. For ancient organisms, oxygen was toxic. What did life look like in those days?

A recent study conducted by scientists of the Institute of Sciences of Earth and the Life of Tokyo was looking for a response in hot sources rich in iron, which approximately repeat the chemistry of the ancient oceans of the Earth during one of the most dramatic periods of the planet: oxidation of the atmosphere.

The results published in the journal Microbes and Environmentssuggest that To obtain energy, some ancient microbial communities used iron and oxygen secreted by photosynthetic microbes. It was a kind of transitional ecosystem, where life turned the waste of new organisms into a new source of energy before photosynthesis became dominant.

The great oxygen event occurred about 2.3 billion years ago And marked the appearance of atmospheric oxygen. Probably, this process was caused by green cyanobacteria that use sunlight to split water and the subsequent transformation of carbon dioxide into oxygen through photosynthesis.

Result: The current atmosphere contains about 78% nitrogen and 21% oxygenwith only small traces of other gases, such as methane and carbon dioxide, which possibly played a large role until the level of oxygen increases.

The "oxygen disaster" radically changed the course of life on Earth. A high level of oxygen allows animals to breathe, but it created difficulties for ancient forms of life that almost did not know about the O2 molecule. The adaptation of ancient microbes to the presence of oxygen remains a big question.

To search for answers, the authors studied five hot springs in Japan with various water composition. These five sources (one in Tokyo, two in the prefectures of Akita and Aomori) are rich in iron (Fe2+). Such media are rare in the modern oxygen world, since iron quickly reacts with oxygen, turning into an insoluble form FE3+.

But in these sources, the water still contains high levels of FE2+, low oxygen levels and almost neutral pH. These Conditions are considered similar to the ancient oceans of the Earth.

In four of five hot springs, microfaerophilic bacteria were dominant, oxidizing iron. These organisms flourish in conditions with a low oxygen content and use Fe2+ as a source of energy, turning it into FE3+.

Cyanobacteria, known for the production of oxygen through photosynthesis, were also present there, but in relatively small quantities. The only exception was one of the hot springs in Akita, where microbes with metabolism founded not on iron unexpectedly dominated.

Using a metagenomic analysis, the team collected more than 200 high -quality samples and used them for a detailed analysis of microbes in the community.

The same microbes that combined the metabolism of iron and oxygen turned a toxic connection into a source of energy and helped maintain conditions that allow anaerobes sensitive to oxygen to survive.

In these communities, important biological processes took place, such as the cycle of carbon and nitrogen. Having identified genes, the researchers also found signs of a partial cycle of sulfur. Given that hot springs contain very few sulfur connections, this discovery has become unexpected.

Researchers suggest that this may indicate a “hidden” sulfur cycle, when microbes processed the latter in difficult ways, which have not yet been fully studied.

The authors believe that, like these hot sources, the early Earth contained ecosystems consisting of various microbes, including iron oxidizing agents, anaerobes and cyanobacteria living together and regulating oxygen concentration. The discovery deepens the understanding of the early evolution of life on Earth and is important for finding life on other planets.

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This article is republished from naukatv.ru on 2025-09-25 16:00:00. Content and views belong to the original publisher, not UAE Today News.