Research shows Japan’s hot springs show signs about early microbes

Fatima Li-Hau preparing to sample water from a hot spring at low tide. (Image: Natsumi Noda, ELSI)

A graduate student at the Earth-Life Science Institute, Fatima Li-Hau and Shawn McGlynn, who is an associate professor, led a new study. They conducted research on iron-rich hot springs that mimic the chemistry of Earth’s ancient oceans during the Great Oxygenation Event. Published on 25 September 2025, this study examines one of the planet’s most dramatic environmental changes.

Life Before Oxygen

Before the Great Oxygenation Event, Earth had very little oxygen. Microbes were adapted to survive in these harsh and oxygen-poor conditions. They utilised ferrous iron and trace oxygen for their energy. Photosynthetic microbes produced only small amounts of oxygen at that time. This shows that life thrived despite challenging pre-oxygen environments.

Insights from Japanese Hot Springs

The researchers studied five different hot springs across Japan’s regions. These springs contained ferrous iron and very low oxygen levels. These conditions mimic parts of Earth’s early oceans long ago. Iron-oxidising bacteria thrived in low-oxygen conditions in most springs. Cyanobacteria, which produced oxygen, existed in the early oceans but were far fewer in number.

Understanding Early Ecosystems

Studying these modern analogues helps researchers understand ancient microbial metabolic pathways. It reveals ecological interactions during Earth’s transition to an oxygen-rich atmosphere. This research demonstrates microbes’ great adaptability in tough environments. It suggests that iron-rich, low-oxygen planets could potentially support life. This expands the search for extraterrestrial life beyond Earth.