Currently, we usually classify living beings into three domains:Archaea, Bacteria and Eukarya. At the Archaea Domain, we find the prokaryotic organisms previously classified, together with bacteria, as organisms belonging to the Kingdom Monera, extinct realm after being created the classification in Domains.
→ What are the organisms classified in the Archaea Domain?
As stated earlier, archaea are prokaryotic organisms, that is, they do not have a membrane-bounded cell nucleus, thus, their genetic material is dispersed in the cytoplasm. These organisms, however, are no longer classified with bacteria, as they have characteristics that the they also leave them close to the eukaryotes, in addition to the existence of specific characteristics among them, which constitute their own group.
Many archae are considered Extremophile organisms, however, there are species that live in a moderate environment. Extremophile organisms are those that live well in extreme environments, such as those that are high in salts and extremely hot. Because of these characteristics, some researchers claim that species belonging to this group define the limits of biological tolerance. In the group of extremophiles, we can include halophytes and extreme thermophiles:
Extreme halophytes: They are organisms that live in salt-rich environments, which are generally located in hot, dry regions, where there is high evaporation. Some of these species tolerate the salt-rich environment; others, however, depend on this environment. Halobacterium, for example, it is unable to survive when the salinity drops below 9%.
Extreme Thermophiles: This group of organisms lives in extremely hot environments, which would be deadly for most living organisms. An example of extreme thermophiles is the genus archaea Sulfolobus, that survive in volcanic springs with a temperature around 90 °C.
Regarding archaea that live in moderate environments, we must highlight the methanogenic, Archaea's best-known group. This group is widely distributed in nature, produces methane as a by-product of its energy production processes, and is composed of mandatory anaerobes. Among the places where they can be found, we can mention the viscera of cattle and other herbivores, below ice sheets in Greenland and in swamps and deep aquatic sediments. These organisms are still used by humans for decomposition in sewage treatment plants.
→ Archaea Domain Division
Crenarchaeota: Includes most thermophilic species.
Euryarchaeota: In this group are all methanogens and many extreme halophiles.
Korarchaeota: Includes little-known extreme thermophilic organisms.
By Ma. Vanessa dos Santos
Source: Brazil School - https://brasilescola.uol.com.br/o-que-e/biologia/o-que-e-archaea.htm
