Parts of the Lassen Volcanic National Park in California’s Cascade Range resemble the gateway to a hellish underworld, with pools of boiling water and bubbling mud where almost nothing can live, due to scalding temperatures that can reach a blistering 464 degrees Fahrenheit.
That’s enough to kill a human, obviously, which rangers and ample signage helpfully point out to visitors throughout the park. And yet: a team of scientists in America and Europe have discovered one remarkable organism that can survive and even thrive in these hellish waters: a tiny single-cell “fire amoeba.”
This humble critter, a gooey-looking blobunder the microscope, has set a “new record for the upper temperature limit” for all complex organisms on Earth because it can divide at a burning-hot 145.4 degrees Fahrenheit, according to the scientists who laid out their findings in a yet-to-be-peer-reviewed study published last week.
In reporting by Nature, the researchers said the existence of the once-unknown amoeba — now called Incendiamoeba cascadensis, meaning “fire amoeba from the cascades” — also challenges the notion that certain organisms called prokaryotes, which includes all bacteria, are the only lifeforms on Earth that can survive extreme temperatures that kill almost everything else.
Prokaryotes, which have no distinct nucleus, are still the reigning champs of biological toughness, as they can persist in temps between 149 and 221 degrees Fahrenheit — and they can theoretically be viable up to 392 degrees, above which nucleotides and amino acids start to break down.
Prokaryotes, which also includes a domain of microbes called archaeans, can be found in steaming compost piles, and places with volcanic activity and hot springs such as Lassen. The highest known temperature shrugged off by a prokaryote, an archaean called Methanopyrus kandleri, is 251.6 degrees Farenheit, a record for all organisms, prokaryotes or not.
In contrast to prokaryotes, the fire amoeba is an eukaryote — complex organisms that include every animal, plant, fungi, and also unicellular tiny lifeforms called protists, encompassing algae and other amoebae — and is composed of cells, or one cell in the case of the fire amoeba, that have a distinct nucleus bound by a membrane and interior organelles.
Eukaryotes such as mammals and us humans have an upper temperature limit of 109.4 degrees Farenheit, above which we die. Until now, the upper temperature limit for more hardy eukaryotic organisms, such as fungi and red algae, was thought to be 131 to 140 degrees Fahrenheit, so this discovery of the fire amoeba is remarkable.
“We need to rethink what’s possible for a eukaryotic cell in a significant way,” Angela Oliverio, Syracuse University microbiologist and study co-author, told Nature.
The team found this tiny microorganism in a stream of hot spring water that was pH neutral, in contrast to the many acidic pools in Lassen.
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