Microorganisms of Yellowstone National Park

Mammoth Hot Springs_1Every year millions of visitors experience the unique beauty (and smell) of the more than 10,000 hot springs, mudpots, fumaroles (steam vents), travertine terraces and geysers at Yellowstone National Park. These hydrothermal features are home to hardy thermophilic bacteria which thrive on the extreme conditions found in the park.

To celebrate the 100th Anniversary of the National Park Service, we are sharing a list of some of the amazing microorganisms that help make Yellowstone National Park so majestic.


Hot Spring_3Thermophilic Bacteria

Hydrothermal features at Yellowstone, like the Grand Prismatic Spring, provide the ideal habitat for thermophilic bacteria. These aptly named extremophiles – “thermo” means “heat” and “phile” means “lover” – thrive on the energy and chemicals found in the hot springs throughout Yellowstone. Grouped together to form microbial mats, the thermophiles give the hydrothermal features their unique and brilliant colors.

Thermophilic bacterial mats are formed when individual bacteria connect to Do Not Mark Bacterial Matsform long strands known as filaments. Mini-ecosystems are created when the strands bind together to form the thermophilic mats. Examples of these mats can be found in many places throughout Yellowstone including the popular tourist attraction, Mammoth Hot Springs.

The communities formed by thermophiles living in the run-off from hot springs are often likened to miniature forests. Microbes living on the surface of the bacterial mats perform photosynthesis to provide fuel for the community (like a forest canopy). Energy is derived from this fuel by the organisms living inside the mat. These microbes also decompose and recycle nutrients to the mat’s canopy helping the ecosystem thrive.

Bacterial Mats


Thermus aquaticus

The “heat loving water dweller,” Thermus aquaticus was discovered by scientists in the Lower Geyser Basin in 1966. Thermus aquaticus thrives in high heats ranging from 50°C to 80°C (122°F to 176°F). These microbes contain the enzyme, Taq DNA polymerase, which is one of the backbones of molecular biology. The heat-resistant enzymes are used in the polymerase chain reaction (PCR) DNA amplification technique.


Hot SpringCaldicellulosiruptor obsidiansis

Obsidian Pool is where an anaerobic, extremely thermophilic, cellulolytic bacterium was discovered by scientists from the U.S. Department of Energy’s BioEnergy Science Center. Scientists hope studies of the anaerobe, Caldicellulosiruptor obsidiansis, will lead to development of a genetically modified thermophilic anaerobe capable of converting switchgrass to ethanol.

Caldicellulosiruptor obsidiansis,  named for the location in which it was discovered, is found at the periphery of Obsidian Pool in the Mud Volcano Region of Yellowstone. Heat-tolerant Bacterial Mats_3grasses grow around the edge of the pool. Cells are short, non-motile, Gram-positive rods. The optimal growth temperature is 78°C.  The organism ferments many carbohydrates including glucose, maltose, arabinose, fructose, lactose, mannose, sucrose, galactose and xylose.



Found on the Fountain Paint Pot Nature Trail, cyanobacteria can survive in water up to 73°C (167° F). Depending on water temperature, the bacterial mats can range in color including brown, green, yellow and orange. Three billion years ago, cyanobacteria became the first Roaring Mountainphotosynthesizers, helping to make the oxygen-rich atmosphere we have today.


Sulfobobus acidocaldarius

The Roaring Mountain is home to another thermophile, Sulfolobus acidocaldarius. These microbes thrive on the hydrogen sulfide gas escaping from the earth. Sulfolobus acidocaldarius helps convert the gas into sulfuric acid which breaks the volcanic rock into clay resulting in erosion.


Decription of All Thermophilic Bacteria Found in Yellowstone National Park – source NPS.gov 

Name Temperature Description Location


Color: dark brown mats

Metabolism: photosynthesis by day;

fermentation by night

  • Mammoth Hot Springs
  • Upper, Midway, and Lower Geyser Basins
Phormidium 35–57°C


Color: orange mats

Metabolism: photosynthesis

  • Mammoth Hot Springs
  • Upper, Midway, and Lower Geyser Basins
Oscillatoria 36–45°C


Color: orange mats

Metabolism: photosynthesis;

oscillating moves it closer to light sources.

  • Mammoth Hot Springs
  • Chocolate Pots
Synechococcus 52–74°C


Color: green mats

Metabolism: photosynthesis by day;

fermentation by night

  • Mammoth Hot Springs
  • Upper, Midway, and Lower Geyser Basins
Green Sulfur


Color: dense, dark green mats

Metabolism: anaerobic photosynthesis—

produces sulfate and sulfur, not oxygen.

  • Mammoth Hot springs
  • Calcite Springs
Green non-sulfur


Color: green mats

Metabolism: anaerobic photosynthesis

  • Mammoth Hot Springs
  • Upper, Midway, and Lower Geyser Basins


Color: yellow and white streamers

Metabolism: uses hydrogen, hydrogen sulfide and carbon dioxide as energy sources;

can use arsenic in place of hydrogen sulfide.

  • Norris Geyser Basin
  • Amphitheater Springs


Color: bright red or orange streamers

Contains carotenoid pigments that act as sunscreen.

  • Lower Geyser Basin



Want to know more? Check out these resources:

Hydrothermal Features: https://www.nps.gov/yell/learn/nature/hydrothermal-features.htm

Paint Pot Nature Trail:  https://www.nps.gov/features/yell/tours/fountainpaint/stopslist.htm

Thermophilic Archea: https://www.nps.gov/yell/learn/nature/thermoarchea.htm

Some Like It Hot: http://www.yellowstonepark.com/some-like-it-hot-rare-microbes-flourish-in-yellowstone-national-park-geysers-and-hot-springs/

Caldicellulosiruptor obsidiansis:  http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2820981/?tool=pubmed