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Types of Extremophiles (Microbe Mission 7)
Types of Extremophiles
Some types of microbes are extremophiles, meaning they thrive in extreme conditions that would quickly kill many other organisms. Some examples of extreme environments where microbes have been found are hot springs, saline lakes, the ocean floor, deep-sea hydrothermal vents, acid mine drainage sites, cold deserts, and subglacial lakes. While many extremophiles are either archaea or bacteria, there are also some extremophilic eukaryotes. Extremophiles come in many different varieties:
Acidophiles and alkaliphiles prefer to live in areas with very low (usually pH < 3) or very high pH (usually pH > 9), respectively. In contrast, neutrophiles prefer environments around pH = 7 and are not considered extremophiles.
Capnophiles inhabit environments with very high concentrations of carbon dioxide (CO2).
Halophiles are highly tolerant to environments with high salt concentrations, such as salt lakes.
Osmophiles are organisms that live in areas with very high osmotic pressures, which result from high concentrations of solutes - especially sugars - in the surrounding environment.
Piezophiles (also called barophiles) live under conditions of high hydrostatic pressure.
Thermophiles are microorganisms prefer very high temperature environments. Usually, thermophiles are considered to live between 45-80C (sometimes the lower end of the range is states as closer to 50C), and organisms that grow best above 80C are called hyperthermophiles. Psychrophiles (also called cryophiles) are extremophilic organisms that grow at temperatures -20C to 20C, while mesophiles usually reside in moderate temperatures between 20-45C and are not considered extremophiles.
Xerophiles are a type of extremophile that inhabit environments with very low moisture or humidity.
Other extremophiles are capable of dealing with high concentrations of gases that are toxic to many other microbes.
Some extremophiles exhibit metallotolerance, the ability to live in conditions with high concentrations of metal cations, and are called metallophiles.
Some extremophiles exhibit radioresistance, the ability to withstand very high doses of ionizing and/or nuclear radiation, and are called radiophiles (e.g., Deinococcus radiodurans, and a group of microscopic animals called Tardigrades).
In many cases, extreme environments have more than one extreme quality and are inhabited by polyextremophiles, which are organisms that display multiple tolerances to extreme conditions.