New research from Japan, published in Space.com, suggests that iron-rich hot springs may explain how early microbial life survived the introduction of oxygen to Earth billions of years ago.
According to a study conducted by the Earth-Life Science Institute at the Institute of Science, Tokyo, these unique ecosystems likely played a crucial role in bridging the gap between an alien, ancient world and the modern, oxygen-filled planet we know today.
The Great Oxidation Event
Approximately 2.3 billion years ago, Earth underwent the Great Oxidation Event (GOE). During this period, oxygen-producing cyanobacteria introduced atmospheric oxygen to the planet. While this event eventually allowed modern life to flourish, it posed a severe threat to the ancient microorganisms that were then the dominant life form, as oxygen was toxic to them.
The mystery of how these ancient microbes adapted and survived this transition has been a subject of scientific inquiry.
To understand this survival mechanism, a team led by graduate researcher Fatima Li-Hau and supervised by Associate Professor Shawn McGlynn studied five hot springs across Japan.
These specific springs were chosen because their chemical composition mirrors that of Earth’s oceans during the GOE. They are: Rich in ferrous iron, low in oxygen, and possessing a nearly neutral pH.
“These iron-rich hot springs provide a unique natural laboratory to study microbial metabolism under early Earth-like conditions,” McGlynn stated.
Key Findings
The researchers told Space.com that they discovered thriving microbial communities in these springs that resemble ancient transitional ecosystems. In four of the five sites, microaerophilic iron-oxidising bacteria were the dominant group, while cyanobacteria appeared in smaller numbers.
Metagenomic analysis revealed a critical survival strategy: the microbes that metabolised iron were also able to metabolise the oxygen produced as waste by the cyanobacteria. This capability allowed iron oxidisers, oxygenic phototrophs, and anaerobes to consistently coexist.
Additionally, the study found that these communities carry out carbon and nitrogen cycling. Researchers also detected a “cryptic” partial sulfur cycle, despite the hot springs containing very few sulfuric compounds.
The findings, published in the journal *Microbes and Environment*, offer a detailed view of how life may have adapted during one of Earth’s most significant transitions.
“By understanding modern analogue environments, we provide a detailed view of metabolic potentials and community composition relevant to early Earth’s conditions,” Li-Hau said on Space.com.
