NASA-supported researchers have discovered an organism that can survive at temperatures previously thought impossible for complex life. Scientists found the amoeba, Incendiamoeba cascadensis, in the heated waters of California's Lassen Volcanic National Park.
The fire amoeba can reproduce by division at 145 degrees Fahrenheit, setting a record for the upper temperature limit of all known eukaryotes—organisms with a nucleus and membrane-bound organelles. The previous record of 140 degrees Fahrenheit was held by a few species of fungi and red algae. Although the amoeba stops reproducing above 145 degrees Fahrenheit, it remains active and continues to search for food at temperatures up to 147 degrees Fahrenheit.
The findings were published Tuesday in the journal Cell. Beryl Rappaport, a graduate student at Syracuse University and lead author of the study, noted that the discovery challenges long-held assumptions. "In part, studies on eukaryotes may have been limited because of assumptions about membrane stability," Rappaport said. "We are hoping that the discovery of I. cascadensis encourages others to keep searching for high temperature eukaryotes."
The research team sequenced the amoeba's genome and identified genes that stabilize DNA and protect it from breaking down under extreme heat. Other genes enable the organism to sense its external environment. At high temperatures, the expression of certain genes increased, including those involved in protein folding maintenance.
The research has implications for understanding where life might exist beyond Earth. Scientists study extremophiles—organisms that survive at the extreme edges of habitability—to learn about the potential for life on other worlds like Mars. Researchers found evidence of similar DNA sequences in geothermal samples from locations worldwide, including New Zealand and Yellowstone National Park, suggesting related thermophilic amoebas may exist globally.