In Hot Springs such as those found in Yellowstone National Park, one can observe the presence of thermophilic bacteria in brightly colored films and stringy
filaments. In solfatera
fields (which can be found in volcanic landscapes such as that of Iceland) archaebacteria
draw their energy from the reactions created when escaping sulfuring gases
collide with oxygen: just as human metabolism burns carbohydrates for energy, thermophilic metabolisms have the ability to burn sulfides
for that same purpose. Such organisms
can live in temperatures up to 100 degrees.
However, since water is a necessary component for life, thermophiles in terrestrial hot springs and solfatera
fields are limited to the temperatures at which water remains in its liquid
form. When temperatures rise above 100
degrees, water evaporates and microorganisms can no longer exist.
Black smokers, volcanic hot springs in the ocean floor, harbor three
quarters of all hyperthermophilic life. Since the normal temperature in the deep sea
is closer to 2 degrees, the mixing of extreme hot with extreme cold results in
an instantaneous precipitation of heavy metal sulfides, this accounts for the
several-meter-high “chimneys” of black “smoke”.
For the thermophilic bacteria in the black
smokers, photosynthesis is clearly not a metabolic option; they, like the
microorganisms found in solfatera fields, draw energy
from the reduced sulfur compounds of the their surrounding water.
The reasons that thermophiles can withstand such intense heat are
several. For one, they have developed
special membranes made of waxy chemicals rather than true fats; these waxy
chemicals have higher melting points than do the fats
that make up human cellular membranes.
As far as DNA goes, it is believed that thermophiles
have protein and protein-like materials that stick to the double helix and help
it sustain its shape in the face of ridiculously high temperatures. Furthermore, it is thought that small
molecules, such as ATP, which are needed for energy transfer within cells (and
which cease to function in very hot water) are made anew by thermophiles
as fast as they decompose. This thinking
has led certain microbiologists to believe that life could exist in
temperatures of up to 160 degrees (although, thus far, 110 degrees is the
limiting temperature of all found life).
Their reasoning is that 160 degrees Celsius is the highest temperature
in which ATP can be formed as rapidly as it decomposes.
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