Syracuse University scientists supported by NASA discovered the single-celled amoeba Incendiamoeba cascadensis thriving in the geothermal waters of Lassen Volcanic National Park, California. The newly identified microbe reproduces by cell division at temperatures reaching 63 °C (145 °F), establishing a record for eukaryotic life and redefining the environmental conditions that could sustain complex biological organisms across the solar system.
The organism, nicknamed the fire amoeba, pushes past long-held assumptions regarding the thermal fragility of membrane-bound cells. Angela Oliverio, assistant professor of biology at Syracuse University and corresponding author of the study, stated that “this finding pushes the bounds of what we thought was possible, which is incredibly exciting. There could be more eukaryotes that can survive at even higher temperatures than we know of.”
Thermal limits of Incendiamoeba cascadensis in volcanic environments
Field teams collected thermal water samples across Lassen Volcanic National Park between 2023 and 2025. Laboratory testing confirmed that Incendiamoeba cascadensis remains active, moving and consuming bacteria, at temperatures as high as 64 °C (147 °F). When exposed to heat ranging between 64 °C and 70 °C (158 °F), the amoeba halts its motion, creates a protective outer layer, and enters a state of dormancy.
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The organism fully revives once ambient temperatures decline from that upper dormancy boundary. However, laboratory cultures determined that an exposure of 80 °C (176 °F) is lethal to the microbe. Researchers also verified that the species is an obligate thermophile, meaning it cannot develop in cold environments and begins active cellular reproduction only when water temperatures rise above approximately 42 °C.
“We set up cultures at a few temperatures, with the hottest being 57° C because that is the highest temperature previously described for an amoeba,” said H. Beryl Rappaport, lead researcher, microbiologist, and Ph.D. candidate in the Department of Biology at Syracuse University.
Scientific records and baseline metrics of Incendiamoeba cascadensis
- Formal publication date: September 22, 2026, in the peer-reviewed journal Cell
- Initial preprint submission: November 24, 2025, on the bioRxiv repository
- Sampling location: Geothermal creeks and hydrothermal pools in Lassen Volcanic National Park, California
- Reproduction threshold: 63 °C (145 °F), marking the highest recorded division temperature for any eukaryote
- Active locomotion ceiling: 64 °C (147 °F)
- Dormancy survival threshold: 70 °C (158 °F)
- Lethal temperature limit: 80 °C (176 °F)
- Precipitating research sponsors: National Aeronautics and Space Administration (NASA) Exobiology Division
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Genomic mechanisms behind heat resistance in Incendiamoeba cascadensis
Eukaryotes possess internal structures enclosed by membranes, including a defined nucleus holding genetic material. These cellular components historically appeared incapable of maintaining structural integrity above 60 °C (140 °F). Earlier thermal records for eukaryotic replication were set by specialized red algae and fungi that max out at that mark.
Genetic sequencing of Incendiamoeba cascadensis revealed several evolutionary solutions that stabilize molecular architecture under severe heat. The amoeba expresses proteins with a high positive electrical charge across their surface, which prevents denaturing. It also relies on enhanced protein-folding processes and gene segments that shield DNA strands from thermal degradation, mirroring survival mechanisms found in single-celled prokaryotic extremophiles.
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Environmental DNA screenings identified gene fragments closely related to Incendiamoeba cascadensis in thermal basins in Yellowstone National Park and New Zealand. The distribution indicates that related thermophilic eukaryotes may inhabit volcanic systems worldwide without prior detection.
Prokaryotic benchmarks compared to Incendiamoeba cascadensis
The overarching biological limit for reproduction in extreme heat still belongs to the domain Archaea. Methanopyrus kandleri, a single-celled prokaryote discovered near deep-sea hydrothermal vents, can divide at temperatures reaching 122 °C (252 °F). Prokaryotes achieve this thermal resistance because their basic cellular structure lacks internal organelles and nuclear membranes that disassemble when heated past the boiling point of water.
Because Incendiamoeba cascadensis maintains internal compartmentalization despite heat stress, its cellular stability demonstrates that complex cellular architecture can endure temperatures previously considered prohibitive. The discovery changes how biochemists evaluate protein stability and cellular longevity under geothermal strain.
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NASA exobiology applications in the search for extraterrestrial life
The findings alter how space agencies select planetary targets in searches for organic life outside Earth. Extremophiles provide empirical baselines for evaluating environments on celestial bodies that deviate from temperate conditions, such as the subterranean oceans of Jupiter’s moon Europa or hydrothermal zones beneath Mars.
“Studying extremophiles helps us better understand the biochemical and physiological limitations of life as we know it on Earth,” said Alison Olcott, program scientist in the Exobiology Division at NASA headquarters in Washington. “This information, in turn, helps guide NASA’s search for life as it expands the range of conditions we think life could potentially be inhabiting elsewhere.”
Field scientists note that ambient temperature remains only one component of habitability. Complex unicellular life also requires specific water chemistry, nutritional prey, pressure, and gas concentrations. Research groups are continuing to analyze the metabolic pathways of Incendiamoeba cascadensis to establish whether similar eukaryotic organisms can maintain growth under varied atmospheric pressures and chemical balances.