Microbiologists discover fire amoeba reproducing at 63 degrees Celsius

Discovery in volcanic streams

A research team from Syracuse University identified a new single-celled organism capable of surviving and reproducing in extreme heat. The microbe, named Incendiamoeba cascadensis, was isolated from geothermal streams in California's Lassen Volcanic National Park. Field sampling conducted between 2023 and 2025 targeted geothermal waters with temperatures ranging between 47°C and 64°C. The researchers initially travelled to study an acidic site at Boiling Springs Lake, where other amoebas survive up to 54°C, but gathered two samples from an adjacent stream with neutral pH water. Laboratory analysis published on 22 September 2026 in the journal Cell showed that this previously unclassified amoeba survived under thermal conditions previously considered lethal to complex cells.

Adrienne Kish, a microbiologist at the National Museum of Natural History in Paris who was not involved in the study, noted the significance of the sampling environment.

“By looking in an unusual place, the study team found unusual life.”

Pushing eukaryote temperature thresholds

Eukaryotes, which include animals, plants, fungi, and amoebas, possess complex cellular structures with distinct nuclei and membrane-bound organelles. For decades, biologists treated 60°C as the upper thermal boundary for eukaryotic cell division, a limit derived primarily from studies of fungi and red algae. Incendiamoeba cascadensis grew steadily at 57°C in laboratory incubators before continuing cell division via mitosis at 63°C. The amoeba remained mobile and explored its surroundings at 64°C. When researchers subjected cultures to 70°C, the cells survived by modifying their shape and forming a protective layer, recovering normal activity once returned to lower temperatures.

Steady growth57

Cell division (mitosis)63

Mobility threshold64

Maximum survival limit70

Steady growth

57 °C

Cell division (mitosis)

63 °C

Mobility threshold

64 °C

Maximum survival limit

70 °C

Data from the article text

Cellular defenses and genetic adaptations

To determine how the amoeba withstands heat that curdles egg proteins at 65°C, researchers sequenced its genome. The genomic analysis identified duplicated genes dedicated to DNA repair and protein maintenance compared to amoebas from temperate habitats. Structural adaptations in the outer cell membrane provide physical stability against thermal stress, mirroring mechanisms found in thermophilic prokaryotes. Simpler single-celled organisms without nuclei, such as the hydrothermal vent archaeon Methanopyrus kandleri, survive at temperatures up to 122°C. Incendiamoeba cascadensis now establishes the highest known threshold for any organism with a cell nucleus.

Angela Oliverio, an associate professor and microbiologist at Syracuse University, described the broader significance of the finding.

“This finding pushes the bounds of what we thought was possible, which is incredibly exciting.”

Boiling Springs Lake amoeba54

Previous eukaryote benchmark60

Incendiamoeba cascadensis (survival)70

Methanopyrus kandleri (archaeon)122

Boiling Springs Lake amoeba

54 °C

Previous eukaryote benchmark

60 °C

Incendiamoeba cascadensis (survival)

70 °C

Methanopyrus kandleri (archaeon)

122 °C

Data from the article text

Broader implications for microbiology

The identification of Incendiamoeba cascadensis expands the known physical boundaries under which complex life can operate. Researchers suggest that other uncatalogued eukaryotes may inhabit unexplored thermal niches across the globe. Understanding heat-stable eukaryotic enzymes and repair pathways could also assist industrial applications that rely on high-temperature biochemical processing. Lead author Beryl Rappaport pointed out that detailed eukaryotic studies in extreme environments remain sparse.

“So few have been described, especially in detail. We have a lot to learn from them.”