Thermophilic Archaea

Archaea live is some of the hydrothermal features at Mud Volcano, like this boiling mudpot.
Archaea are the most extreme of all extremophiles, and some scientists think they have not changed much from their ancestors. Archaea can be found in the Mud Volcano area, among other places in Yellowstone.



Archaea are the most extreme of all extremophiles—some kinds live in the frigid environments of Antarctica, others live in the boiling acidic springs of Yellowstone. These single-celled organisms have no nucleus, but have a unique, tough outer cell wall. This tough wall contains molecules and enzymes that may keep acid out of the organism, allowing it to live in environments of pH 3 or less. (Vinegar, for example, has a pH of less than 3.) Archaea also have protective enzymes within their cells.

Some scientists think present-day archaea have not changed much from their ancestors. This may be due to the extreme environments in which they live, which would allow little chance for successful changes to occur. If this is so, modern archaea may not be much different from the original forms—and thus provide an important link with Earth’s earliest life forms.

Once thought to be bacteria, organisms in the domain Archaea actually may be more closely related to Eukarya—which includes plants and animals.

Many kinds of archaea live in the hydrothermal waters of Yellowstone. For example, Grand Prismatic Spring at Midway Geyser Basin contains archaea. They are most well known in the superheated acidic features of Norris Geyser Basin and in the muddy roiling springs of the Mud Volcano area.

Whenever you see a hot, muddy, acidic spring, you are probably seeing the results of a thriving community of archaea called Sulfolobus. This is the archaea most often isolated and most well known by scientists. In sulfuric hydrothermal areas, it oxidizes hydrogen sulfide into sulfuric acid, which helps dissolve the rocks into mud. The Sulfolobus community in Congress Pool (Norris) is providing interesting new research directions for scientists: It is parasitized by viruses never before known on Earth.


Thermophilic Archaea in Yellowstone National Park

Name pH Temperature Color Metabolism Notes Location
Domain Archaea 0.9–9.8 up to 92°C (197.6°F) None Chemosynthesis, using hydrogen, sulfur, carbon dioxide Unicellular, tough cell membrane In many of Yellowstone’s hydrothermal features
Sulfolobus (Genus most often isolated) 0–4 40–55°C (104–131°F) Green Photosynthesis Red algae phylum Norris Geyser Basin,& Lemonade Creek, Nymph Creek
Traverine terraces of Mammoth Hot Springs host thermophilic bacteria.

Thermophilic Bacteria

Almost all hot springs and geysers host thermophilic bacteria.

Green colors line a thermal runoff pool.

Thermophilic Eukarya

Microscopic plants and animals live in the extreme environments of Yellowstone's hydrothermal features.

Blue waters of Congress Pool are host to thermophilic viruses

Thermophilic Viruses

Viruses, a logical part of thermophilic ecosystems, have been found in some pools in Yellowstone.

Orange-colered bacterial column growing in geyser runoff water.

Thermophilic Communities

Thermophilic communities are very diverse, depending on the microbes living there, the pH, and the water temperature.

View of the

Thermophiles in Time & Space

Yellowstone's hydrothermal features and thermophilic communities are studied by scientists searching for evidence of life on other planets.

A dark blue hot spring with a white crested edge rimmed by orange water

Life in Extreme Heat

Hydrothermal features are habitats for microscopic organisms called thermophiles: "thermo" for heat, "phile" for lover.

Last updated: August 23, 2017

Contact the Park

Mailing Address:

P.O. Box 168
Yellowstone National Park, WY 82190-0168


(307) 344-7381

Contact Us