Thermophiles are little creatures that live in hot-as-hell environments, above 45 to 50 degrees Celsius, in which organisms like us humans would basically melt. Our fats and proteins would break down, and at around 65 to 75 degrees Celsius the double helices of our DNA, the very "stuff" of us, would fall apart. If our world were to be heated above said temperatures, humans and all complex organisms would simply cease to be; life, nonetheless, would go on.
Thermophiles have been found in soil that is subjected to direct and full sunlight, reaching 50 degrees at midday. They are also present in fermenting materials such as compost piles and silage, which can reach temperatures of 60 to 65 degrees. But the most extreme thermophiles are found in environments near to active volcanoes: terrestrial hot springs, solfatera fields (areas of fading volcanic activity whose soil excretes sulfuric gas), and deep sea hot spring vents commonly referred to as "black smokers."
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.
But thermophilic microorganisms have been found in temperatures up to 110 degrees Celsius, and it is believed that they can live in temperatures nearing 160 degrees. How, you may wonder, can this be? The answer is this: these temperatures exist in places where the evaporation of water is unfathomable, namely at the bottom of the sea (where the pressure is so great that the boiling temperature of water is raised to 400 degrees Celsius).
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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