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Until very recently it was thought that life could develop only
under "normal" conditions, i.e., with neutral pH (around 7),
with low ionic strength (similar to that of blood plasma), at
temperatures around 37°C, at normal atmospheric
pressure (corresponding to altitudes up to several kilometres) and
in the presence of oxygen. Obviously thses limits were basically anthropocentric and the result of considering our species as the centre of the Universe.
Human beings have always been at war with microbes, mainly to
prevent food spoilage and diseases. This is the reason why people
became obsessed with finding what would prevent microbial growth. To preserve food we have learned to use salt (ionic strength), both
high and low temperatures, pH (pickling), drying and irradiation. As a
consequence we have found that although most organisms are unable to
develop or remain viable in those conditions, some are exceedingly
stubborn, resisting extreme conditions, or even requiring them for
optimal growth. Organisms that develop and thrive under extreme conditions are
known as extremophiles. Here are some important weblinks to
comprehensive information about this fascinating field of research:
At the beginning of the 20th century the salt fish industry
suffered a devastating economic disaster when all the salt cod was
spoiled by halophiles (salt loving
microbes) present in the marine salt used for its preservation. The discovery of chemolithotrophic acidophiles (acid lovers,
some of them able to grow at negative pH) in the mid-1940's explained
the cause of pollution from acid mine drainage associated with the
mining industry, a problem of grave environmental concern. The discovery of hyperthermophiles (heat loving microbes)
had to wait until Thomas Brock isolated some of them in the
geysers and fumaroles of Yellowstone National Park in the United
States during the 1960's. At the beginning of the 1980's, the hunt was on in microbial
ecology to find the most extreme of the extremophiles. As a result we
found microorganisms in oceanic black smokers that can grow at
113°C in a pressure cooker, or at temperatures
below 0°C in polar ice. Others thrive at negative
pH (concentrations higher than 1M sulfuric acid) in copper
mines, or high pH (over 12) in soda lakes. Some live under enormous pressure at the bottom of
the oceans (over 1100 bars), or are able to survive extremely high doses
of radiation in nuclear power facilities. And others survive
dried out in the form of viable dormant endospores for millions of
years, or in rock matrices several
kilometers under the surface of the Earth, etc., etc. ... What use are extremophiles? Although for many years they were considered a problem (halophiles
and thermophiles for food conservation, acidophiles for ground water
contamination), scientists became interested in finding the limits of
life and the mechanisms associated with their extreme behaviour. In
addition, possible technological applications are being explored for
biomining, enzymology at high temperature or low moisture levels,
bioremediation, etc. Recently extremophiles have earned an important place in
Astrobiology: the search for life in the universe. Indeed, the
possibility that life can develop at extreme conditions of
temperature, pressure, pH, high radiation or low moisture levels has
increased the chances of finding life elsewhere in the universe, in
systems with conditions completely different from our planet
Earth. |  Yellowstone
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Last updated July 26, 2001
