Scientists identify 'fire amoeba' that sets new temperature record for complex life

# What the fire amoeba is

Researchers have described a newly identified single-celled eukaryote they call Incendiamoeba cascadensis, informally the "fire amoeba." This organism can reproduce at 145°F and continue moving at temperatures as high as 147°F. Those values set a new high-water mark for the heat tolerance of complex cells—cells that contain a nucleus and internal structures, unlike bacteria or Archaea.

# Where it was found and how

The organism was discovered in northern California, in Lassen Volcanic National Park. Field sampling targeted steaming geothermal pockets along a tributary of Hot Springs Creek. The team used extra-long barbecue tongs to dip vials into the hot water and collect samples. Back in the lab, researchers examined the water under microscopes, filmed organisms, and tracked activity and reproduction at different temperatures.

# Why this matters

Before this find, the highest reliably documented heat tolerances belonged mainly to simpler microorganisms such as certain bacteria and Archaea, with some species thriving near or above the boiling point of water. Eukaryotes had not been observed reproducing at these higher temperatures. The fire amoeba nudges the known eukaryote threshold up by about five degrees Fahrenheit, demonstrating that more complex cellular architectures can persist at higher temperatures than previously documented.

# Who led the work

The discovery and analysis were carried out by a team led by microbiologist Angela Oliverio at Syracuse University, with graduate students including Beryl Rappaport. The findings were published in the journal Cell.

# Methods and evidence

Field collection focused on accessible geothermal microhabitats in a low-traffic part of a national park. Samples were brought to the lab and observed with microscopy and time-lapse filming to document movement and reproduction under controlled temperature conditions. The team measured the temperatures at which the organism remained motile and at which it reproduced successfully.

# How it compares to other organisms

Some bacteria and Archaea live at or above 212°F, so the new record does not approach the extremes those groups can tolerate. The significance lies in the fact that eukaryotic cells—more structurally complex than bacteria or Archaea—were found functioning and reproducing at higher temperatures than previously recorded.

# Immediate implications

The discovery prompts targeted searches for other heat-tolerant eukaryotes in geothermal habitats. It also widens the set of environmental conditions scientists consider possible for complex single-celled life. The research group emphasized that finding one example demonstrates possibility rather than declaring a final upper boundary for eukaryotes.

# Bottom line