Some 2.3 billion years in the past, the Earth would have been unrecognizable to us. At that point, historical microorganisms had been the dominant life kind; there have been no animals, no plants, and positively no people.
But then, one thing modified. Oxygen-producing cyanobacteria triggered the Great Oxidation Event (GOE), which launched atmospheric oxygen to our planet and allowed life as we all know it to flourish. For historical microorganisms, nevertheless, the occasion ought to have been a dying knell. Oxygen was poisonous to them — but by some means, they tailored and survived.
New research from the Earth-Life Science Institute at the Institute of Science Tokyo suggests iron-rich ecosystems played a role in bridging the gap between that alien world and our modern, oxygen-filled planet. The evidence, it would appear, lies in Japan’s hot springs.
The study, led by graduate researcher Fatima Li-Hau and supervised by associate professor Shawn McGlynn, focused on five hot springs across Japan rich in ferrous iron, low in oxygen, with a nearly neutral pH. This chemical composition mirrors that of the Earth’s oceans around the time of the GOE
“These iron-rich hot springs provide a unique natural laboratory to study microbial metabolism under early Earth-like conditions during the late Archean to early Proterozoic transition, marked by the Great Oxidation Event,” McGlynn said in a statement. “They help us understand how primitive microbial ecosystems may have been structured before the rise of plants, animals, or significant atmospheric oxygen.”
In these sizzling springs, the crew uncovered thriving microbial communities that resemble these historical transitional ecosystems. In 4 of the 5 websites, microaerophilic iron-oxidizing micro organism dominated, whereas cyanobacteria appeared in smaller numbers. Metagenomic evaluation revealed that the microbes that metabolized iron had been additionally in a position to metabolize oxygen produced as waste by cyanobacteria throughout photosynthesis.
“Despite differences in geochemistry and microbial composition across sites, our results show that in the presence of ferrous iron and limited oxygen, communities of microaerophilic iron oxidisers, oxygenic phototrophs, and anaerobes consistently coexist and sustain remarkably similar and complete biogeochemical cycles,” mentioned Li-Hau.
The metagenomic evaluation additionally revealed that these communities of microorganisms perform carbon and nitrogen biking as a part of their organic processes. Interestingly, the researchers found a partial sulfur cycle, too — however the sizzling springs had only a few sulfuric compounds to assist such exercise. Thus it is attainable that the microbes perform a “cryptic” sulfur cycle that we don’t but perceive.
These findings provide a brand new window into how life tailored throughout certainly one of Earth’s biggest transitions — and promote additional examine of communities of microorganisms dwelling in sizzling springs. “By understanding modern analog environments, we provide a detailed view of metabolic potentials and community composition relevant to early Earth’s conditions,” says Li-Hau.
The analysis was printed within the 2025 version of the journal Microbes and Environment.