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New 'Fire Amoeba' Sets Eukaryote Heat Tolerance Record

A newly discovered single-celled organism, nicknamed the 'fire amoeba,' has established a new record for heat tolerance among eukaryotes, thriving in conditions previously considered lethal for this domain of life.

Researchers found the amoeba, named Incendiamoeba cascadensis, in California hot springs. It can grow at 63° Celsius (145° Fahrenheit), surpassing the previous eukaryote record of 60° C. This organism includes all life forms with nuclei and organelles, such as plants, fungi, and animals.

The study involved collecting water samples from geothermal hot springs and attempting to grow amoebas in the lab at various temperatures. The team observed the amoeba not only growing at 63° C but also surviving up to 70° C by entering a dormant state.

While simpler microbes like bacteria and archaea can tolerate much higher temperatures, the fire amoeba exhibits adaptations similar to these organisms. These include chemical features on its protein surfaces that prevent harmful clumping at high temperatures.

The amoeba can also switch between two body shapes, potentially aiding its survival in fluctuating hot spring temperatures. One form appears suited for foraging, while another faster form may help it escape unfavorable temperature changes.

Scientists believe that even more heat-tolerant eukaryotes may exist, as they do not yet know the upper temperature limits for this domain of life.

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