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Archaea
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Archaea (Domain: Archaea)are unicellular organisms that lack a nucleus (prokaryotes). They are very similar to bacteria, but as a result of their particular characteristics, they were considered from the early 1970's as another life form on Earth, distinct from the bacteria (Domain: Bacteria) or from any other living being we know, such as the plants, animals, fungi and protozoa (Domain: Eukarya).

They are microscopic organisms, the cells of which are wrapped with a cover (cell wall) made of different materials that gives them a high resistance to antibiotics or other harmful substances. Their food (chemotrophs) is also very different as they can feed on inorganic substances such as hydrogen, sulfur and iron or carbon dioxide and alcohols among others.

Although they are common in terrestrial and marine environments, some have life habits so strange that they have earned the adjective “extremophiles”, because they are adapted to live in places where the environmental conditions are extreme; such as in high or low temperatures, high concentrations of salt or low pH, where it is virtually impossible for any other living creature to survive.

For example, thermophyllic (heat tolerant) archaea are able to grow at high temperatures, from 80 to 100 °C, such as those found in hot springs and geysers, up to the 400 °C registered at the hydrothermal vents on the seabed.

Halophytic (salt-tolerant) archaea like to live in places with high concentrations of salt. Deposits from which salt is extracted, natural salt lakes and the surfaces of salted fish and meat are ideal conditions for these organisms to reproduce. The Great Salt Lake in the U.S. and Wadi Natrun Lakes in Egypt, have ten times more salt than seawater and are predominantly inhabited by archaea.

Due to these characteristics, archaea have great biotechnological potential. For example, some are being used to produce bio-plastics, which degrade more rapidly in the environment and reduce pollution. Others produce methane as part of their metabolism (cell biochemical reactions), in fact, there are already urban and industrial waste treatment plants that use this methane as a source of energy. They have also been used in science as models in the search for life beyond planet Earth (astrobiology).
     
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