June 26, 2021 – A Science Lesson Brought to you by Yellowstone National Park

Let’s start with this scene, 6 am at the West Yellowstone entrance to the national park. The line was short compared to the 3 miles of vehicles coming in at 1pm as we were leaving.

This blog is inspired by our first visit to Yellowstone National Park. But I will warn you now, I am going off on a tangent, sort of a Bill Bryson “Short History of Nearly Everything” kind of tangent.

The highlight of most people’s visit to the park is the eruption of Old Faithful, which occurs every 60-90 minutes. Here, I wait with a 1000 other people for earth’s most famous geothermal to spew a column of hot water and steam into the air.
There are about a thousand geysers on earth and most of them are in Yellowstone National Park. This was well worth the wait.

Many years ago, I picked up an oversized book at the local Borders bookstore titled “The Animal Kingdom”. I think I paid $10 ($2 per lb) for it as it was among many on a table of discounted books. As someone fascinated with how life forms adapt to their environments, I loved that 1000+-page book and referred to it quite often to indulge my armchair analyses of the natural world. And it was only when Vivian and I purged most of our belongings to live in a 300-sq-ft RV that I parted ways with it.

This early morning sight awaits as you enter Yellowstone National Park from the west side. These are steam vents or fumaroles, and in the morning they are quite visible. These are basically waterless geysers.
The park does a good job giving people close access to the geothermals. This is the Midway Geyser Basin boardwalk into the Grand Prismatic Springs.
Water temperature in the Excelsior Geyser is 199 degrees F. This is a dormant geyser, last eruption well over a hundred years ago. Today, it is a thermal spring that churns out lots of hot water.

What left an impression on me from that book came from its introduction. In it, the main topic ‘Animals’ was placed into a broader context in which all living things are organized (biological taxonomy). The information was current enough that it described the three-domain system devised by Carl Woese in 1990. Basically, all life can be categorized into archaea, bacteria and eukarya. Stay with me here, this blog really is about Yellowstone National Park.

I can almost see where someone might be tempted to walk out into this scene which is the outer area of the Grand Prismatic. And people have, unfortunately. People also throw things into the hot pools.
Look closely at the bottom end of this picture and you’ll see footprints. Some are human and I suspect bison made the others. I also suspect the human footprints were officially made by a park service employee.
Turquoise Pool seen here from the Midway Geyser Basin boardwalk connects underground to Excelsior spring.

To put this into a casual blog context, there are two kinds of cells in this world. One is the well-known eukaryote which contains a membrane-bound nucleus where all the genetic coding exists. Eukaryotes are what animals and plants are made of, and thus, animals and plants (along with fungi by the way) fall into the eukarya domain. Whereas, the unicellular microorganisms of the archaea and bacteria domain are prokaryotes, cells with no membrane-bound nucleus. And here’s a fun fact, prokaryotes were the first life forms on this planet, eukaryotes evolved from them. Nevertheless, eukaryotes are profoundly different from prokaryotes.

The boardwalk contains a bridge that crosses the Firehole River. Here, you see the banks of the river that connect it to the hot springs.

In the 1970s, scientists began sequencing DNA and RNA. Applying this cutting-edge technology, Woese & colleagues discovered that bacteria were just as different from archaea as they were from eukaryotes. As a result of their work, Woese determined that any known life form could be classified within one of these three domains – archaea, bacteria or eukarya. I don’t know about yours, but in my mind that offers an interesting perspective on life considering that humans are only one of millions of species within the animal kingdom that is only one of four within one domain that is one of three on the entire tree of life.

Imagine coming upon an aquamarine pool like this, feeling fatigued from your exploration. So inviting! The blue indicates the center of the spring, where temperatures are the highest, up to 189 degrees F.

Upon my discovery of the three domains, I turned my attention away from the sexy topic of eukarya and discovered a more seductive one and while at it, picked up a new favorite word – extremophile. Almost entirely within the archaea domain are the prokaryotic unicellular organisms that live under extreme conditions. Having spent a better part of my adult life studying human physiological adaptations to physical stress, I was drawn naturally to the idea that there are organisms surviving, strike that, thriving in environmental conditions so extreme that a human could not survive beyond a millisecond. Our physiology allows us to endure a lot, hot and cold temperatures, excessive physical demands, and high and low atmospheric pressures. When our physiology reaches its limits, our brains devise ways to overcome those limitations. Up to a point, that is. To that end, extremophiles make us look like wimps.

The boardwalk takes you past Excelsior and then to the Grand Prismatic Springs. Here you see the outlying areas surrounding grand prismatic, with temperatures ranging from 147 to 188 degrees F. The rust-colored mats indicate extremophiles living in “cooler” temperatures.
Extremophiles, or more specifically, thermophiles are not wimps, but they can’t live everywhere. At temperatures of 189 degrees F, there are no living microorganisms, as indicated by the blue or hottest area of the spring. Blue indicates clear water. Why blue? When sunlight hits the water surface, it scatters. Blue light scatters the most and reflects off the water, which is what we see.
Of course, not everything can survive in extreme environments. Dead trees are common in Yellowstone as you see here. The springs are rich in minerals, like calcium carbonate. That’s the white stuff you see. It clogs the vascular systems of the trees.

Some extremophiles live in ice, some live thousands of feet under the ocean surface next to sea vents and some live in Yellowstone National Park. While you were self-isolating to avoid a tiny virus spreading across the land, you may have run across a story about a discovery in Yellowstone in 1966. On a visit to the park, biologist Dr. Thomas Brock made a discovery that microorganisms lived in the extreme heat of Yellowstone’s hot pools.

What you see here are microorganisms, archaea and bacteria, extremophiles, thermophiles. This was at the West Thumb Geyser Basin, next to Yellowstone Lake.
Yellow indicates temperatures around 165 degree F, thanks to cyanobacteria that produce carotenoids. Orange is another species of microorganisms that survive in slightly cooler temperatures, 149 degree F.
Red or burgundy color are microorganisms surviving in 131 degree F. Here you see a mud pot, not as attractive as the hotter aquamarine pools. Mudpots are lined with clay and have no direct connection to underground water. They are also stinky due to hydrogen sulfide gas. That’s Yellowstone Lake in the background.

A couple decades later, another scientist, Kary Mullis was attempting to make copies of a single DNA molecule. To do that, he needed an enzyme that could work at high temperatures. Guess where he found his enzyme? From Brock’s discovery of Thermus aquaticus in Yellowstone, scientists like Mullis could purchase a culture and grow batches to find the heat-resistant enzyme. It worked and those enzymes became the key to a widely used method to make millions of copies of genetic material. That method, called polymerase chain reaction or PCR, has such a significant effect on scientific advances, that a Nobel Prize in Chemistry was awarded to Mullis in 1993. And In 2020, scientists used the PCR method (remember the nose swab?) to detect the genetic material of COVID-19. You got to love science.

The travertine terraces of Mammoth Springs seen here and below. These are formed from limestone and the hot water that rises through the limestone.
The water carries dissolved limestone or calcium carbonate and deposits it at the surface. This forms the chalky white travertine terrace. The orange and rust colors are, you guessed it, extremophiles!

But I digress. The real reason most of us come to Yellowstone is not because of a fascination of tiny microorganisms that can live in temperatures above 170 degrees or pH levels below 3, but rather because our eyes perceive it as one of the most beautiful and fascinating places on earth. Earth needs to let off a little steam and heat, and it does so through its geothermal exit points – geysers, fumeroles, hot springs and mudpots. And where there are geothermals, there are thermophilic archaea and bacteria thriving among them. Because these extremophiles love to interact with heat and light, they become a feast of colors to the human eye. The creation of art through the collaborative efforts of biology and physics. Art on the edge brought to you by extremophilia.

And that is where we are left standing, in awe of earth and its life forms that present themselves beyond our human boundaries. That’s the nature of nature, and Yellowstone National Park offers one of the best ornaments on the tree of life.

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