What are Extremophiles?

Extremophiles are incredible creatures, testing the limits of the types of environments where scientists think life can possibly survive.

Sabrina Stierwalt, PhD
4-minute read
Episode #254


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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About the Author

Sabrina Stierwalt, PhD

Dr Sabrina Stierwalt earned a Ph.D. in Astronomy & Astrophysics from Cornell University and is now a Professor of Physics at Occidental College.