Thermophilic Viruses

A blue steaming pool surrounded by pale rock
A virus was discovered in Congress Pool, shown here, at Norris Geyser Basin. It was infecting the archaeum Sulfolobus.


A magnified image of a blue, teal, and orange shape
This virus parasitizes Sulfolobus.

Thermal Biology Institute, Montana State University

Like bacteria, the word "virus" often conjures up images of sickness and death. However, relatively few of the many types of viruses cause problems for humans. None of the thermophilic viruses in Yellowstone should cause problems for human health—our bodies are too cold, for one thing.

Unlike microorganisms in the three domains, viruses are not considered to be alive. (Yet they are still called "life forms.") They have no cell structure, only a protein "envelope" that encloses a piece of genetic material. They cannot reproduce on their own. Instead, a virus inserts itself into a host cell and uses that cell's nutrients and metabolism to produce more viruses.

Scientists suspect many viruses exist in Yellowstone's hydrothermal features because they would be a logical part of the thermophilic ecosystem. One kind was discovered in Congress Pool, at Norris Geyser Basin. It was infecting the archaeum Sulfolobus. Another kind of virus has been identified in pools near Midway Geyser Basin.


Thermophilic Viruses in Yellowstone National Park

Name pH and Temperature Description Location
Viruses (not in a domain) pH 0.9–5.8; optimum 2–3
55–80°C (131­–176°F) optimum 70–75°C
  • Protein coats a core of genetic material
  • Cannot reproduce by itself
  • Reproduces by using the host cell’s metabolism
  • Not considered living
  • Predators of other microbes
  • In many of Yellowstone’s hydrothermal features
Unnamed Acidic
  • Shape very similar to viruses that infect bacteria and animals, which could mean this group of viruses existed early in the development of life on Earth
  • Unnamed pool near Midway Geyser Basin
Unnamed Acidic
  • Parasitizes the archaeum, Sulfolobus
  • Norris, Congress Pool


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