Home, For the Hyperthermophiles



CYellowstone is world-renowned for its thermal features and wildlife (see Yellowstone Ashore). However, the bison, bears, wolves, deer, and lodgepole pines that we all appreciate and photograph are only a small fraction of the total biology of the park.

CThe most abundant species, and among the most economically important to us, live in the boiling springs and geysers of the park. The individuals of these species are invisible to our naked eyes - only their abundance allows us to see their colonies as they color the thermal waters.


Background Biology

CRemember the childhood game of "Animal, vegetable, or mineral?" Well, the world has changed. These three categories are no longer a logical way to divide what we see around us. You think in Yellowstone that you can pigeonhole your observations of biology into plants or animals? You are dating yourself. In the past few decades, microbiological studies have redefined the 'tree of life.' Now, you play the game of bacteria, archaea, eukarya, or mineral? Eh?

CIn the 1970's (see how far out of date you are?), Dr. Carl Woese proposed a new 'tree of life,' based on microbiological studies. Analysis of the genetic material, called ribosomal RNA, revealed the existence of a major new group of microbes, the Archaea. This group contains many species formerly classified as bacteria.

The Tree of Life

A More Detailed View - from Yellowstone Resources and Issues, 2008

CHow does this relate to Yellowstone? Well, the red line in the new 'trees' above connects organisms called hyperthermophiles (hyper - extreme; thermo - heat; phile - lover). These critters live in an environment where temperatures are above 176 degrees F. And water boils at Yellowstone's elevation at 198 degrees! Some thrive in temperatures, up to 239 degrees F. How can they live at such elevated temperatures? Well, the very fact that we ask such a question reflects our adaptation to a temperature range significantly lower. Consequently such high temperatures seem impossible for life. In fact, many life forms would 'freeze' in our 70 degree thermostat-controlled living room, and much prefer (in fact could only live) in our hot water heater. Early times on Earth were excessively hot for us, and we could not have survived. Then the hyperthermophiles ruled! Now, with a 'cold' earth, we (and other life forms familiar to us) have evolved and thrive.The hypers find refuge only in scattered hot springs.

CSince geologists have evidence that the early times on Earth were very hot, these organisms are considered the only forms of life that could have survived those hyperthermo times, and hence are probably the earliest life forms on Earth. All later life evolved from them, according to the current hypotheses on early life on Earth. And Yellowstone has more hot springs bubbling to the surface than any other area on Earth. So here you are, looking at bison and bears, and some of the your ancestors with the longest genealogy and the most active biological research surround you by the billions. And most folks ignore them, and until this month in Yellowstone, so did we!

CAnd it's no wonder they have been overlooked, even by biologists, until recently. These critters are so small that 500 of them, placed end to end, would be about the size of this period . The hot springs and geysers of Yellowstone are well-known and as a visitor we expect to see them - but the vibrant colors of many of the boiling pools surprise (and fascinate) many - and the life within fascinate microbiologists - and us.


CA geologist, Walter H. Weed, was the first to recognize that the colors of Yellowstone's hot springs were microbial. He wrote, in 1889, "There is good reason to believe that the existence of algae of other colors, particularly the pink, yellow and red forms so common in the Yellowstone waters, have been overlooked or mistaken for deposits of purely mineral matter ... the red and yellor tinges of the algae combine with the weird whiteness of the sinter and the varied blue and green of the hot water to form a scene that is, without doubt, one of the most beautiful as well as one of the strangest sights in the world."

CThermophiles have not only been overlooked in Yellowstone's hot springs but also in volcanoes, deserts and man-made thermal environments throughout the world. Some are found in power plants and may even thrive in your hot water heater!

CEvery hot spring in Yellowstone is a unique environment. They differ from each other in their chemistry, temperature, and rates of flow. Each may be home to a different community of vividly-colored microorganisms. For instance, the springs at Norris and Mud Volcano are acidic water, altered by sulfuric acid derived from sulfur-rich gases that have their origin deep in the earth. Some spring water will blister your skin from an acidity greater than that of your car battery! This is home for the group known as thermoacidophiles - fellers who have two environmental barriers for most life - heat and acidity - but these organisms thrive in these hellish springs, and probably are descendants, little changed, from the earliest life on earth when most of our planet's surface was boiling hot and highly acidic. Their relations may occupy other planets throughout the solar system! Some algae can even grow in a pH 100 times more acidic than vinegar.


Acidic Mud Pot - A Potful of Thermoacidophiles

COthers, such as those just north of Old Faithful, including the Upper, Midway, and Lower Geyser Basins, are neutral or slightly alkaline (perhaps about the same as the cookie dough in your mixing bowl). The microbiology of these 'groups' of hot springs is radically different. Because the environment of early Earth was very hot and mostly highly acidic, the microbiota of the Norris and Mud Volcano (the thermoacidophiles) are probably derived from, and very similar to, the very earliest life forms on our planet. So when you smell those rotten eggs near Yellowstone's hot springs, it is a reminder that you are near the homewaters of what are probably your most ancient ancestors!

Alkaline Spring - Doesn't Look Like My Cookie Dough!

Some Details

More about the 'New Biology'


CA little more about the 'tree of life' above. We are familiar with the name bacteria. They are single-celled microorganisms, without nuclei. They differ from each other in shape, ability to move, and metabolism. We all have tales that relate to experiences with the most nasty bacteria, those that cause human disease, but most are quite benign or even useful for us. They are found in most of Yellowstone's hot springs.

Home, For Bacteria

CSome chemosynthesize, thriving on sulfur or hydrogen for their energy source. They don't need air or sunlight to live (some thrive deep in the ocean's abyss, surrounded by perpetual cold blackness, clinging to ocean floor hot spring mounds) and others have been found in cores from wells thousands of feet below land surface). Their by-products are often useful for other organisms, both thermophiles and critters living in cooler temperatures . All the cyanobacteria (mostly blue critters) and green non-sulfur bacteria, photosynthesize, using sunlight to draw energy for their lives. Some both chemosynthesize and photosynthesize. Cyanobacteria release oxygen as a 'waste' - they were the first photsynthesizers (over 3 billion years ago), and created the atmosphere we know today. Without them, we would not be writing and reading this. In Yellowstone's hot springs, some bacteria, normally sheres or rod-shaped, join together into long filaments or strands. These group together into mats - a whole 'forest' of microcritters happily sharing a community. They sometimes bind sand into their 'town' or build towers and spires.


Forests of Life - Mats and Sprires of Microcritters


CThe archaea are also single-celled microorganisms without nuclei, but their membranes differ from other life forms - they were formerly classified with bacteria but are now known to be uniquely different. They can survive the highest temperatures, and are often indicated by the white color band of very hot water, surrounded by stripes of orange, yellow, red, and brown.


'Stripes' and a Swimming Hole for Archaea


CEukarya are single or multicelled organisms with a distinct membrane-bound nucleus. Some are microscopic and others are huge.

Cyanidium - Eukaryotic Alga That Grows in Acid Water

CWe, the bisons and bears, and the lodgepole pines are all multicellular creatures, all eukarya and related to each other. Most familiar life around us are Eukarya, but the most abundant of all, the microfolks, are often overlooked.


Not to be Overlooked! Mama Griz with Two Cubs Behind Her; And the Other Eukarya Watching Them


CHot springs are a rainbow of colors - in this case reds, browns, and yellow. The eye fixes on the color and the left side of the brain finds joy and appreciation in the artistic blending of color in nature's palette. But, now for the right side? Why?


Colorful Beauty, But Why?

CThese are mats, whole colonies, entire forests of microorganisms in stratified layers. The top layers are composed of microbes that photosynthesize, using the energy of the sun for growth.They take the sun's energy and convert it into food for themselves and the colony. They also make a slimey glue-like material that binds the colony into a mat.

Synechcoccus, Top Dweller of the Mat

CDeeper layers of organisms use the chemical by-products of the surface photosynthsizers for their food. They do the vital decomposing and recycle nutrients back to the surface microbes. On a micro scale, this ecosystem is similar to that of the better-known tropical rain forest, or, for that matter, the forest out your back door. The canopy trees photosynthesize and drop their waste products to the forest floor or release them to the atmosphere. The bottom dwellers decompose and recycle the nutrients required by the canopy trees. Here, however, it all takes place in less than a few inches.

Chloroflexus, Bottom Layer Resident


Top View of the Mat



Aerial View and on the Ground - Blue is Refracted Skylight; Orange is from Hyperthermal Folks





CThe colors above are the sum total of billions of filaments and sausage-shaped cells of a thermophilic cyanobacteria and an understory of archaea microbes and bacteria. The colors also relate to the seasons or amount of sunlight. The chlorophyll produced at the top of the mat is green, but is masked by carotenoid pigments of orange, yellow or red, produced by the understory. (Carotenoids are related to vitamin A and are why Flamingos are bright pink! - they eat food rich in carotenoids so vary in color depending on their diet!)

CIn Yellowstone's hot springs, summer is the time for the carotenoids since they protect the surface organisms from the bright sunlight. Consequently, summer colors are usually brilliant. In winter, or after a string of cloudy dark days in summer, chlorophyll dominates and the mats are darker.



Here's What They Look Like - Up Close and Personal; Phormidium and Synechococcus (left); Calathrix right


CEarly in this discussion we commented about the economic importance of these microcritters living in Yellowstone's hot springs. Economic? Yep, one type of bacterium is the basis of a multimillion dollar medical and biotechnical industry. Copying and amplify DNA requires an enzyme necessary to sustain a chain reaction at very high temperature. A hyperthermopile, originally discovered in a Yellowstone hot spring, supplies the enzme and thrives at the high temperature. A single molecule of DNA replicates into millions, thanks to the hyper. This process is essential in medical diagnosis and forensic research.


Thermus aquaticus, the Hyperthermophile That Saves Human Lives



So, here they are. In a photomicrograph and as you see them at Mammoth Hot Springs. For us, an entirely new appreciation of the wonders of Yellowstone National Park.


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