In the microscopic world, we find the best examples of extreme survival, beings capable of living in habitats where other forms of life are impossible.
Hydrothermal spaces, the depths of volcanoes, spaces without oxygen, or underwater acid jets are some of the favorite places for Extremophile microorganisms to live.
These bacteria have populated our planet for billions of years and have a series of singularities that have caused scientists to pay more and more attention to them. Although approaching them is not an easy task, most of them live underground, making their study extremely difficult.
Extremophiles offer us certain indications about the possible existence of analogous microorganisms on Mars, a planet that has temperatures ranging between -20ºC and -100ºC, where its inhabitants would also have to tolerate high salt concentrations that allow the water to be liquid at such low temperatures.
Methanogenic and halophilic
Extremophiles include methanogenic bacteria and anaerobic microorganisms that do not tolerate exposure to air, however brief it may be. Thanks to their metabolism they are able to use hydrogen as a source of energy and carbon dioxide as a source for their growth.
They are common bacteria in the rumen of cows and ruminants, animals capable of eliminating up to fifty liters of methane gas daily through their mouths.
Metahnococcus jannischii belongs to this group, an irregular coconut that was isolated in a chimney -white smoker- at a depth of 2,600 meters in the Pacific Ocean, being able to withstand a range of temperatures that oscillate between fifty and eighty-six degrees Celsius.
Another group of extremophile bacteria is known as halogens, which live in extremely saline environments, such as the Dead Sea, the Great Salt Lake, or saltwater evaporation ponds.
The strategy of these microorganisms to withstand the high salt concentration is to avoid the effects of osmosis, a process by which water passes through the cell membrane from the most diluted solution to the most concentrated.
When the temperature is not a problem
There are extremophiles that require very high temperatures – close to one hundred degrees centigrade – in order to grow. Most are usually found in hot springs or sulfurous waters (eg Sulfolobus), in deep seas, or in acid mining drainages.
In 1969, scientist Thomas Brock discovered a bacterium – Thermophilus aquaticus – in Yellowstone National Park that is capable of living at temperatures exceeding 45ºC.
In the other corner would be, for example, the Polaromona vacuolate, an extremophile from the group of psychrophiles or cryophiles, which live at extremely low temperatures. Its habitat is the waters of Antarctica, where it lives at 0ºC, with an optimum temperature close to 4ºC.
There are also acidophilic microorganisms -they live at a very low pH-, among which is Lactobacillus acidophilus, which lives in the human intestine; others capable of surviving space radiation, suspending their metabolic processes for long periods of time to adapt to the most hostile conditions, such as tardigrades, also known as water bears.
The key to all these examples has been adaptation, all of them have been able to shape their survival in impossible habitats for the vast majority of species.
