Researchers have discovered a new species of extreme lifeform in Lassen Volcanic National Park in California’s Cascade Range, which can survive temperatures up to 158°F (70°C) by changing shape and forming a protective outer layer.
Dubbed Incendiamoeba cascadensis, or “Fire Amoeba from the Cascades,” the unusually adaptive organism, whose survival ability exceeds the previously assumed upper limit of 140°F, is able to eat and reproduce in hot spring waters reaching 145°F (63°C).
Syracuse University’s Angela Oliverio, a corresponding author on the study detailing the extreme organisms’ record-breaking adaptive abilities, said the finding pushed the bounds of what science thought was possible, “which is incredibly exciting.”
Hints of Fire Amoeba’s Extreme Abilities Study Inspired
According to a statement announcing the fire amoeba’s extraordinary abilities, the ‘hottest growing’ organism previously described in scientific literature is a simple archaeon microorganism, Methanopyrus kandleri. Found alongside deep-ocean thermal vents, M. kandleri lives at a blistering 252°F (122°C), or above the temperature at which water boils.
Among eukaryotes, organisms with complex cellular structures including plants and animals, the upper limit was assumed to be 60°C (140°F). The research team said at those extreme temperatures, “only a handful” of eukaryotes can survive, much less eat and reproduce.
Still, they add, previous efforts have identified “traces of amoebae” near geothermal springs that exceed the 140°F threshold. However, researchers have not studied those species closely enough to confirm their ability to survive extreme temperatures. Olivero said this knowledge gap motivated the team to take a closer look at the elusive fire amoeba.
One Collected Specimen Stood Out From the Rest
To collect viable specimens to study back in the lab, the researchers collected organisms from geothermal streams within Lassen Volcanic National Park in California’s Cascade Range between 2023 and 2025. The specimens were collected from waters between 117°F and 147°F (47°C to 64°C).
When examining the specimens in the lab, the research team said that “one previously unknown amoeba stood out.” Unlike the others collected, the team said this mystery amoeba “grew robustly” at 135°F (57°C).
Beryl Rappaport.
Scientists previously assumed that this extreme temperature represented the ceiling for amoeba growth, so they gradually increased the water’s temperature to see what would happen.
When the water reached 145°F (63°C), the fire amoeba could still successfully replicate via mitosis. The study authors said the fire amoeba appeared to form a protective outer layer and change its shape at this temperature.
When the test water reached 158°F (70°C), the study authors said they were still able to recover after being cooled back down. This team said these results “confirmed that it could not only survive but also thrive at temperatures beyond the previously recognized limit for eukaryotes.”
DNA Sequence Reveals Secrets Behind High Temperature Survival
When researchers sequenced the fire amoeba’s genome, they found several genetic adaptations that convey its extreme heat-tolerance abilities. For example, the hardy organisms have what they termed “extra genes” associated with DNA repair and protein maintenance. These genes likely give the fire amoeba an extra layer of protection against heat damage that other amoebae in more moderate environments don’t need.
Further analysis revealed that the extreme organism’s proteins possessed more positively charged amino acids on their surfaces than their mild-environment equivalents. The study authors said this same feature, which may help proteins remain stable and avoid clumping together under extreme heat, has been identified on the outer layers of “the most heat-tolerant bacteria and archaea.”
The study’s first author, H. Beryl Rappaport, a doctoral student at Syracuse University, said the results show how biologically divergent organisms can take similar paths to survival in extreme environments.
“Even though these organisms are so different, there’s convergence in how protein properties are selected for stability under high temperatures,” Rappaport explained.
Discovery “Expands Our Understanding”
Discussing the team’s findings, Olivero said the record-breaking fire amoeba could inspire future extreme environment survival research efforts that don’t start with preconceived notions. The researcher noted that the discovery also suggests that more species adapted to such extreme temperatures may simply be waiting for scientists to discover them.
“There could be more eukaryotes that can survive at even higher temperatures than we know of,” Olivero explained.
Although the new record is only slightly higher than the previous eukaryotic temperature survival limit, the team compared the discovery’s significance to newly established records in other walks of life.
“Every time we set a new world record in sports, it’s amazing and celebrated, even if it’s by milliseconds,” Oliverio said. “We should do the same for amoebae.”
“These very small changes expand our understanding of what we think is possible,” the researcher added.
The study “A geothermal amoeba sets a new upper temperature limit for eukaryotes” was published in Cell.
Christopher Plain has spent the last six years as Associate News Editor and Head Science Reporter at The Debrief. Follow and connect with him on X, learn about his novels at plainfiction.com, or email him at christopher@thedebrief.org.