Scientists have discovered a new species of amoeba in California that can grow and reproduce at temperatures of up to 63°C (145°F), setting a new heat-tolerance record for known complex life.
The single-celled organism, named Incendiamoeba cascadensis, was found in geothermal waters inside Lassen Volcanic National Park. Researchers say its ability to remain active under extreme heat challenges previous assumptions about the upper temperature limits of organisms with complex cells.
The findings were published on September 22 in the journal Cell. The research was led by scientists from Syracuse University, with support from NASA.
An Amoeba That Lives in Extreme Heat
Amoebas are microscopic organisms known for their ability to change shape as they move and feed. Most organisms with complex cells cannot tolerate temperatures anywhere near those recorded in the California hot springs.
The newly identified species can divide through mitosis at 63°C, meaning researchers observed it actively reproducing at that temperature. It can remain active at around 64°C, where it continues moving through its environment and searching for food.
The discovery pushes the known temperature limit for eukaryotic life beyond the previous record of roughly 60°C. Eukaryotes include animals, plants, fungi and numerous single-celled organisms whose cells contain a nucleus and other membrane-bound structures.
Researchers Found the Amoeba in a California Hot Spring
Scientists collected water and sediment samples from geothermal streams in Lassen Volcanic National Park between 2023 and 2025.
The sampling sites had water temperatures ranging from about 47°C to 64°C. One previously unknown amoeba stood out when researchers grew the organisms under controlled laboratory conditions.
The team initially found that the organism grew strongly around 57°C, which was already the highest temperature previously reported for amoeba growth.
Researchers then gradually increased the temperature.At 63°C, they observed the cells undergoing mitosis.
This provided evidence that the organism was not simply surviving extreme heat but could actively grow and reproduce under those conditions.
The researchers named the species Incendiamoeba cascadensis. The name roughly refers to a “fire amoeba from the Cascades,” reflecting both its heat tolerance and its location.
How Does the Fire Amoeba Survive?
The organism appears to have several ways of protecting itself as temperatures rise.
Above its preferred growth range, the amoeba can change its shape and develop a protective outer layer.
These changes help shield the cell from the damaging effects of extreme heat.Laboratory experiments showed that the amoeba could recover after being exposed to 70°C (158°F) for a short period.
However, 80°C proved too extreme for recovery under the conditions tested.Genetic analysis also gave researchers clues about its unusual resilience.
The organism contains genes associated with processes such as DNA repair and protein maintenance.
These systems may help the amoeba protect important cellular components when temperatures rise.
A Microscopic Predator in a Harsh Ecosystem
The fire amoeba does not live alone in the hot spring.Researchers found that it feeds on heat-adapted bacteria living in the same geothermal environment.
This makes the amoeba an important predator within a microscopic ecosystem where relatively few organisms can survive.
Its ability to remain active at temperatures that exclude many competitors may give it access to a specialized ecological niche.
Scientists say this also makes the organism useful for studying how complex cells adapt to extreme environments.
The Record Is Different From the Hottest Life on Earth
The discovery does not mean the fire amoeba is the hottest organism known.
That record belongs to much simpler microorganisms called archaea. One archaeon, Methanopyrus kandleri, has been documented living at temperatures around 122°C (252°F) near deep-sea hydrothermal vents.
The significance of the new discovery is that Incendiamoeba cascadensis is a eukaryote.
Eukaryotic cells have complex internal structures, including a membrane-bound nucleus.
Scientists have long regarded temperatures around 60°C as close to the upper boundary for eukaryotic life.
The fire amoeba has now pushed that observed boundary to 63°C for active growth and reproduction.
What the Discovery Could Teach Scientists
The researchers say the organism could help scientists understand how complex cells cope with extreme heat.
The findings may also contribute to research into extremophiles, organisms adapted to environments with unusually high temperatures, acidity, radiation or other harsh conditions.
NASA notes that studying organisms living at the limits of Earth’s habitability can also help researchers think about where life might survive beyond Earth.
However, the discovery does not provide evidence of extraterrestrial life. It simply expands scientists’ understanding of the conditions under which complex life can function.
The researchers also suspect that the fire amoeba may not be unique.Other geothermal environments around the world contain organisms that remain poorly studied.
The discovery raises the possibility that additional eukaryotes with unusual heat tolerance could exist in similarly extreme habitats.
For now, Incendiamoeba cascadensis has established a new benchmark for complex life.
A microscopic organism living in a California hot spring has shown that the thermal limits of eukaryotic life may be less restrictive than scientists once believed.
Curated news reports, in-depth analysis, and special features by India’s Opinion editorial team.
