New Heat-Tolerant Amoeba Challenges Eukaryotic Limits

In a groundbreaking discovery, researchers from Syracuse University have identified a new single-celled organism, Incendiamoeba cascadensis, thriving in the hot springs of Lassen Volcanic National Park in California. This amoeba exhibits remarkable heat tolerance, growing and dividing at temperatures up to 63°C (145°F), surpassing previous records for eukaryotic organisms.

The research team, led by microbiologists H. Beryl Rappaport and Angela Oliverio, collected water samples from a pH-neutral hot stream within the park between 2023 and 2025. Upon culturing these samples, they observed the amoeba's growth at 57°C, a temperature consistent with the natural conditions of the stream. Further laboratory experiments revealed that I. cascadensis does not grow below approximately 42°C, classifying it as an obligate thermophile. Optimal growth occurred between 55–57°C, with cell division observed at 58°C and 63°C. Notably, the amoeba remained active at 64°C, setting a new heat-tolerance record for eukaryotic life. (nature.com)

At 66°C, I. cascadensis began forming protective cysts, a survival strategy that allows amoebae to enter a dormant state under extreme conditions. This adaptation enables the organism to withstand temperatures that would typically be lethal to other eukaryotes. (sciencealert.com)

The discovery of I. cascadensis challenges existing paradigms regarding the thermal limits of eukaryotic life. Traditionally, such extreme heat tolerance was associated with prokaryotic organisms like bacteria and archaea. Angela Oliverio commented, "We need to rethink what’s possible for a eukaryotic cell in a significant way." (nature.com)

Lassen Volcanic National Park, located in northern California's Cascade mountain range, is renowned for its geothermal features, including hot springs, fumaroles, and boiling pools. The park encompasses more than 40 volcanoes and is home to Lassen Peak, one of the largest plug dome volcanoes in the world. The park's diverse volcanic and hydrothermal features provide a unique environment for studying extremophiles like I. cascadensis.

The implications of this discovery extend beyond Earth, offering insights into the potential for eukaryotic life in extreme environments on other planets. The ability of I. cascadensis to thrive at such high temperatures suggests that similar life forms could exist in extraterrestrial settings previously deemed inhospitable.

This finding not only expands our understanding of the adaptability of eukaryotic organisms but also opens new avenues for research into the mechanisms that enable life to persist under extreme conditions. As scientists continue to explore the boundaries of life on Earth, discoveries like Incendiamoeba cascadensis serve as a reminder of the resilience and diversity of life in the most unexpected places.