Thermal Virus Hosts in Yellowstone

Created by George Rice, Montana State University

Transmishion electron microscope (TEM) image by George Rice.

TEM of Acidianus showing the typical irregular lobed morphology of the species. Acidianus belongs to the archaeal order of Sulfolobales based on its morphology and clusters with the genera Metallosphaera. The prominent s-layer is evident at the cell surface and a virus particle is attached at the top right corner. Acidianus ranges in size from 0.5-2.0 microns in diameter and is an autotrophic mixotroph. This means that cultures can be grown anaerobically with carbon dioxide and elemental sulfur, or aerobically on yeast extract or peptone. The cell shown here was isolated from Yellowstone National Park while investigating new thermal viruses.

TEM image by Wolfram Zillig.

Thermofilum, another archaean, is shown here with budding virus-like particles protruding from its surface. As with acidianus, the highly structured s-layer is evident at the cell surface. Thermofilum is generally 0.15-0.35 micrometers in diameter and from 1.0 to over 100.0 micrometers in length. Its habitat is solfataric hot springs with a pH of 2.8-6.7 and temperatures up to 100 degrees C, with optimum growth conditions of pH 5 and temperature range of 89-90 degrees C. Thermofilum is a strict anaerobe and utilizes peptides as a carbon source via sulfur respiration.

TEM image by Wolfram Zillig.

Thermoproteus is a member of the order Thermoproteales, also in the domain of archaea. The morphology of Thermoproteus is ridged rods about 0.4 microns in diameter and up 100 microns in length. It is obligately anaerobic metabolizing complex organic substrates via sulfur respiration. Thermoproteus has been isolated from acidic hot springs in Iceland, Italy, North America, New Zealand, the Azores and Indonesia, and will grow at a range of pH's and temperatures up to 100 degrees C. The cell shown here also has virus-like particles emerging from one of its ends. The TEM's of Thermoproteous and Thermofilum are the result of an investigation by Wolfram Zillig in 2002 into the subsurface of thermal pools in Yellowstone, in conjunction with Mark Young's Lab at Montana State University.