A Tiny "Fire Amoeba" Just Shattered What We Thought Was Possible for Complex Life

A Record-Breaking Discovery in a Scalding Hot Spring

Somewhere in the steaming, little-visited backcountry of northern California, tucked into a tributary of Hot Springs Creek surrounded by tall grasses, a single-celled organism has been quietly defying the rules of biology. Researchers at Syracuse University discovered a newly identified fire amoeba, found in Lassen Volcanic National Park, that replicates at temperatures up to 145°F — shattering previous thermal thresholds for complex eukaryotic organisms. The study was published on Tuesday, September 22, in the journal Cell.

The researchers named the new species *Incendiamoeba cascadensis*, roughly translating to "fire amoeba from the Cascades." The name is fitting. The fire amoeba was observed making more of itself via mitosis at a maximum temperature of 145°F, and it could endure and recover from temperatures as high as 158°F by changing shape and forming a protective outer layer. That's not just impressive — it's a biological record.

How Scientists Found It

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). The fieldwork was as unglamorous as it sounds. To collect samples safely, the research team used extra-long barbecue tongs to grip a series of vials that researcher Beryl Rappaport dipped directly into the steaming water.

Back in the lab, Rappaport examined the water under a microscope. When she sped up her video footage, she watched a cell fluidly change shape, protrude, and retract. "That's definitely an amoeba," Rappaport recalled thinking. From there, the team kept pushing the temperature higher and higher in laboratory cultures, ultimately confirming that at 63°C (145°F), the amoeba was undergoing mitosis — a process by which eukaryotic cells divide — confirming that it could not only survive but also thrive at temperatures beyond the previously recognized limit for eukaryotes.

Why This Changes the Science of Extreme Life

Before this discovery, the heat-tolerance record for complex life stood at 57°C (135°F). The samples had contained one particular unknown amoeba that could grow comfortably at 135°F, the previously established limit for amoeba life. The team's willingness to keep raising the temperature revealed an organism operating ten degrees beyond that ceiling. For context, 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. The fire amoeba shares some of those simpler organisms' survival tricks — but with a far more complex cellular structure.

One potential advantage for *Incendiamoeba cascadensis* is that its extreme heat tolerance allows it to avoid competition for food or other resources by being the only organism of its kind in its environment. In other words, it has found a niche so hostile that nothing else dares move in. Angela Oliverio, the Syracuse University microbiologist who led the research, frames the work in terms of fundamental curiosity. "There's a very deep curiosity and desire to understand life at its limits and at its most extreme," she says, "and where that boundary is and what truly are our constraints."

Real-World Implications and What Comes Next

Oliverio argues the amoeba's temperature resilience could offer clues to help create heat-resilient crops or drugs that are stable across a wider range of temperatures. As global temperatures rise and agricultural stress intensifies, understanding the molecular machinery that allows a cell to function in extreme heat could prove enormously valuable. The fire amoeba essentially serves as a natural blueprint for thermal endurance.

The researchers believe this discovery may be only the beginning. Scientists have discovered a species of amoeba that can endure hot temperatures previously thought impossible for any relatively complex lifeform to survive. Researchers at Syracuse University found the survivor living in the hot springs of a national park in California — and it's likely that this amoeba isn't the only one out there that can shatter our preconceptions of life's upper limits. If one fire amoeba can be hiding in a creek surrounded by tall grass, there's no telling what else might be lurking in the planet's most extreme corners, quietly rewriting the rules.