Researchers identified a new single-celled eukaryote, Incendiamoeba cascadensis, that can reproduce at 145 degrees Fahrenheit (63 degrees Celsius). The finding, published in September 2026, breaks the previously theorized limit of 143 F (62 C) for eukaryotic life.
The team isolated the organism from geothermal springs in Lassen Volcanic National Park in Northern California. Incendiamoeba can actively crawl at 147 F (64 C) before entering a protective hibernation-like state at higher temperatures.
Unlike bacteria, which have been recorded living up to 212 F (100 C), eukaryotic cells contain organelles, complex molecular machinery, and a dynamic cytoskeleton. Scientists have not fully understood why eukaryotes tolerate heat poorly compared to bacteria.
The research team examined heat shock proteins, which help refold proteins that unfold under high temperatures. Incendiamoeba has a large reservoir of these helper proteins, but this alone does not explain its heat tolerance, since producing them requires substantial energy and the proteins themselves must be folded correctly.
Incendiamoeba also contains a unique set of protein building blocks that hold proteins together more effectively. Many genes that activate when temperature rises remain unknown. The organism's heat tolerance likely results from a combination of small evolutionary changes rather than a single mechanism, according to the researchers.