Some Like It Hot, Some Like It Cold
Microbial Life in Hot Springs and Antarctic Lakes

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Background
Microbial life in the permanently ice-covered lakes of the Dry Valleys in Antarctica and in the hot springs of Yellowstone National Park can be used to illustrate temperature requirements for optimal growth in microbial populations. Extremophiles can be classified as thermophilic, psychrophilic, halophilic or by other chemical or physical requirement extremes.

In the 1960's, Thomas Brock isolated a bacterium (Thermus aquaticus) from a hot spring in Yellowstone National Park in temperatures that exceeded 70^oC! Most scientists believe that about 150^oC is the upper temperature limit for life. Organisms that live and reproduce in temperature above approximately 50^oC are called thermophiles.

Psychrophiles, cold-loving bacteria, are typically studied as organisms that spoil food. There is little exploration into bacteria that inhabit cold or polar environments. These organisms are classifed based on optimal growth temperatures between 1^oC and 15^oC.

Resources and Reference Materials
Madigan, Michael T. and Barry L. Marrs. "Extremophiles", Scientific American, April 1997, pp.

Life At High Temperatures. Thomas D. Brock. Yellowstone Association for Natural Science, History, and Education, Inc., 1994.

Any general microbiology text such as:
Brock Biology of Microorganisms. Eighth edition. Michael T. Madigan, John M. Martinko, and Jack Parker. Prentice Hall, 1997.

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