This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: A tiny, single-celled organism can thrive at temperatures that would kill all other known complex life. In a study published in Cell, scientists describe a new species of amoeba that can eat and reproduce in hot spring water as warm as 63°C (145°F) in California's Lassen Volcanic National Park.
The amoeba can protect itself at temperatures up to 70°C (158°F) by changing shape and forming a protective outer layer. "This finding pushes the bounds of what we thought was possible, which is incredibly exciting," says corresponding author Angela Oliverio of Syracuse University. "There could be more eukaryotes that can survive at even higher temperatures than we know of." The record for the hottest-growing organism belongs to Methanopyrus kandleri, an archaeon and relatively simple microorganism that lives at 122°C (252°F) around hydrothermal vents in the deep ocean.
For decades, researchers have considered 60°C (140°F) to be the upper limit for eukaryotes, which are organisms with complex cells, such as animals, plants, fungi and some microbes. Only a handful of eukaryotes can grow at temperatures approaching that limit. Previous studies have found traces of amoebae—single-celled microorganisms that can change shape—near geothermal springs, where water temperatures can exceed 140°F (60°C).
But scientists had not thoroughly studied these species to verify that they could cope with extreme heat. So Oliverio and her team set out to do just that. Between 2023 and 2025, the researchers collected organisms from geothermal streams in Lassen Volcanic National Park in California's Cascade Range, where water temperatures at the sampling sites ranged from about 47°C to 64°C (117°F to 147°F).
Among all the samples collected, one previously unknown amoeba stood out. The organism grew robustly at 57°C (135°F) in the lab, the highest temperature previously known for amoeba growth. So the team kept raising the temperature.
At 63°C (145°F), they saw the amoeba undergoing mitosis, a process by which eukaryotic cells divide. This confirmed that it could not only survive but also thrive at temperatures beyond the previously recognized limit for eukaryotes. The researchers named the new species Incendiamoeba cascadensis, roughly translating to "fire amoeba from the Cascades." They found that the fire amoeba can protect itself by changing shape and forming a protective outer layer when temperatures rise beyond 63°C (145°F).
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