New Heat-Loving Amoeba Sets a New Temperature Record for Eukaryotic Life

Scientists have discovered a new species of heat-loving amoeba that completes cell division at 63 degrees Celsius (145 degrees Fahrenheit) and remains motile at temperatures as high as 64 degrees Celsius (147 degrees Fahrenheit).

Incendiamoebae cascadensis thrives in extreme heat

The newly identified amoeba, Incendiamoebae cascadensis, has been described as a “fire amoeba.” It completes its full cell-division cycle, including visible mitosis, at 63 degrees Celsius—well above previously recognized temperature limits for eukaryotes.

Eukaryotes are organisms whose cells contain nuclei and include animals, plants, fungi, algae and amoebas.

For decades, the upper temperature limit for eukaryotic growth was considered to be about 60 degrees Celsius (140 degrees Fahrenheit), based on a small number of thermotolerant fungi and red algae. Some amoebas have been recorded at slightly lower temperatures, with one species reaching approximately 57 degrees Celsius (135 degrees Fahrenheit).

“Thermophiles are organisms that have a high thermal limit and grow optimally above 45 degrees Celsius (113 degrees Fahrenheit),” said Syracuse University doctoral student Beryl Rappaport and colleagues.

“Thermal limits are defined by three thresholds: life-cycle completion, such as cell replication; metabolic activity, such as motility and feeding; and survival.”

How hot can life grow?

The highest known growth temperature is 122 degrees Celsius (252 degrees Fahrenheit), reached only by certain archaea, including Methanopyrus kandleri. Some bacteria, such as Geothermobacter ferrireducens, can grow at temperatures of up to 100 degrees Celsius (212 degrees Fahrenheit).

These temperature limits are notable because heat can denature proteins and other biomolecules while also altering the fluidity of cell membranes.

Despite the importance of thermophilic organisms, efforts to characterize heat-loving eukaryotes and establish their upper temperature limits remain limited. Much of the eukaryotic diversity found in high-temperature environments is still unexplored.

Collected from a geothermal environment in California

Rappaport and colleagues collected Incendiamoebae cascadensis from a tributary of Hot Springs Creek in Lassen Volcanic National Park, California. They sampled the site over a three-year period.

Genetic analysis places the species within Amoebozoa, making it a close but genetically distinct relative of Vermamoeba vermiformis, a heat-tolerant amoeba with a maximum temperature range of approximately 40–45 degrees Celsius (104–113 degrees Fahrenheit).

The researchers also identified matching genetic signatures in metagenomic databases from geothermal areas in New Zealand and Yellowstone National Park. The finding suggests that related heat-tolerant amoebas may be more widespread than previously recognized.

Cellular adaptations help the amoeba withstand heat

By comparing gene activity at 48 degrees Celsius (118 degrees Fahrenheit) and 61 degrees Celsius (142 degrees Fahrenheit), the scientists found that Incendiamoebae cascadensis strengthens its cellular repair systems under extreme heat.

At the protein level, the amoeba displayed distinctive chemical properties, including fewer sticky, aggregation-prone surface patches and a high abundance of positively charged surface residues.

“We were able to discover many strategies in Incendiamoebae cascadensis that could be helpful in understanding thermophiles across all organisms,” Rappaport said.

“For example, some proteins in Incendiamoebae cascadensis have a high positive surface charge, which may help maintain their stability. The charges on these proteins are similar to those found in thermophilic bacteria and archaea.”

Could heat-loving amoebas survive beyond Earth?

“Finding eukaryotes that survive in high-temperature environments not only expands our understanding of where life can be found, but also deepens our understanding of how complex life can be,” said Dr. Alison Olcott, an Astrobiology Program scientist at NASA Headquarters who was not involved in the study.

The discovery may also inform the search for life in extreme environments beyond Earth. However, temperature is only one factor that determines whether an organism can survive. Acidity, oxygen levels, pressure, water and food availability are also essential.

“Complex life such as Incendiamoebae cascadensis might be able to survive on another planet, but Earth is currently the only planet where we know it can thrive,” Olcott said. “Incendiamoebae cascadensis could not survive alone. Other forms of life and supporting environmental conditions would also be necessary.”

The discovery is reported in a paper published in the journal Cell.

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H. Beryl Rappaport et al. Geothermal amoebas set a new temperature limit for eukaryotes. Cell, published online September 22, 2026. doi: 10.1016/j.cell.2026.08.043.