What are Extremophiles?

Did you know there is a creature that can produce its own antifreeze in order to keep its surroundings from freezing it to death? How about a creature that prefers to live in water but can survive being deprived of even a single drop of water? Creatures like these that can adapt to survive in extreme environments were first dubbed extremophiles (meaning “extreme-loving”) by NASA Ames scientist Dr. R.D. MacElroy in 1974.

What is an extremophile?

Extremophiles test the limits of the types of environments where scientists think life can possibly survive. These creatures have found ways to adapt to the most extreme conditions found here on Earth, which can include extreme temperatures, pressure, acidity, high salinity, high metal concentrations, or even radioactivity. For example, some extremophiles found in very high or very low temperatures are found to have modified the composition of their cell membranes to adapt to the temperatures. Other extremophiles may produce extra solutes inside their cells to balance extremely high concentrations of salt.

Some of the extreme environments here on Earth may represent more normal conditions on other planets. Thus, the search for extraterrestrial life includes efforts to study the extremophiles, and where they thrive on this planet, to understand where else we might find signs of life in our solar system.

The study of extremophiles, and in particular the enzymes they produce to deal with their harsh climates, also has potential applications in industry. The “extremozymes” or the enzymes produced by extremophiles are able to inspire chemical reactions despite their harsh living conditions, a trick that may be useful for triggering chemical reactions under the similarly harsh conditions of many industrial applications. Some of these enzymes are already used in the production of biofuels, as well as cosmetics. Extremozymes, and their ability to adapt to their environments, may also prove useful for developing medications like antibiotics or antifungal drugs.

Let’s investigate just a few examples of these extremely unique creatures.

Examples of Extremophiles

• Thermophiles and the Rushing Fireball
• Psychrophiles
• Tardigrades (or Water Bears)

Let's explore these further.

Thermophiles and the Rushing Fireball

Thermophiles are a type of extremophile that can survive at very high temperatures. For example, the thermophile known as thermus aquaticus, found in the hot springs in Yellowstone National Park, not only survives but thrives at temperatures as high as 160 degrees Fahrenheit (or 70 degrees Celsius).

One kind of microbe so extreme even by thermophile standards that it is known as a hyperthermophile is Pyrococcus furiosus, or the “rushing fireball.” The fireball microbe was first discovered in the geothermally-heated waters around Italy’s Vulcano Islands. Scientists from the University of Georgia have been investigating how to use this little extremophile to take in carbon dioxide and turn it into fuel.  

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Psychrophiles

While thermophiles and hyperthermophiles may prefer extreme heat, psychrophiles have adapted to survive temperatures at the other extreme end. Water temperatures deep in the ocean can reach as low as -12 degrees Celsius without freezing, since salt content affects the freezing point of water.

Animals in frozen conditions have to worry about the expansion of ice in and around them as water expands when it freezes. Some psychrophiles survive these conditions by producing their own antifreeze proteins which lowers the freezing point of water around them. Others are able to effectively force themselves to flash-freeze. In other words, the freezing of any of the liquids in their bodies sets off a chain reaction that causes the rest of the body to freeze, and freeze fast, before any potentially dangerous, large ice crystals can form.  

Tardigrades (or Water Bears)

Tardigrades are small, water-dwelling invertebrates that can survive being thrown in boiling water or being frozen in ice. Although aquatic in nature, they can be dried out completely and are able to survive by replacing the water that should be in their bodies with sugar. Despite being only about a millimeter in size, they have even survived being launched into space and thus exposure to a vacuum, cosmic rays, and dangerously high levels of ultraviolet radiation.

Tardigrades are known as polyextremophile because they are capable of adapting to many varied types of extreme conditions. They have hose-shaped mouths full of sharp teeth but are still often considered nature's cutest extremophile. If you cannot imagine how such an animal could be considered cute, check out the video on National Geographic’s blog of a water bear swimming and see for yourself.

We still have not fully explored all of the ecosystems present on our home planet and thus there are likely many more extremophiles waiting to be discovered. One potential extremophile habitat consists of nearly 400 high pressure, underground lakes under the Antarctic ice cap, including the largest example, Lake Vostok. These lakes exist under ice layers several kilometers thick and are heated by geothermal activity. Thus, their conditions are expected to be similar to the underground lakes on the frozen moons of Jupiter.

For more on extremophiles, check out the Life in the Extreme trading cards from the NASA Astrobiology Institute.

Until next time, this is Sabrina Stierwalt with Everyday Einstein’s Quick and Dirty Tips for helping you make sense of science. You can become a fan of Everyday Einstein on Facebook or follow me on Twitter, where I’m @QDTeinstein. If you have a question that you’d like to see on a future episode, send me an email at everydayeinstein@quickanddirtytips.com.

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