Archaea is known as a variety of unicellular microorganisms that make up the archaea kingdom and have their own domain apart from that of eukaryotes and bacteria .
Archaeas are characterized by having a morphological structure of the prokaryotic type, that is, they do not have a specific nucleus, and they are organisms capable of developing under extreme conditions.
Its name derives from the Greek αρχαία ( arkhaía ), which means ‘the old ones’, since it has so far been one of the oldest molecular structures that has been studied and is preserved with few modifications, compared to other microorganisms whose structures They have varied much more over time.
It is worth mentioning that the first classification of archaea as a kingdom of microorganisms was carried out in 1977 by Carl Woese and George E. Fox, since they were previously considered as prokaryotic bacteria.
Characteristics of the archaeas
The main characteristics of the archaeas are the following:
- They have a unicellular membrane composed of lipids that allow it to have greater thermal resistance.
- The cell wall is composed of proteins with form an S layer that protects the outer part of the cell.
- They have flagella similar to that of bacteria, only these can be longer and thicker.
- Its reproduction is asexual.
- These molecules measure between 0.1 μm and 15 μm.
- They take part of their energy from sunlight, organic compounds or hydrogen.
- Some molecules have sizes and shapes very similar to bacteria, and others have very particular shapes, such as square, elongated or flat.
- These microorganisms can be found in various habitats of the planet.
- They are resistant and can easily develop in extreme environments, that is, at high temperatures, high concentrations of salinity, in the seabed, in swamps, oil wells or in the human intestines and even in ruminants.
Classification of the archaeas
The classifications established to determine the domains of the archaeas are based on the phylogenetic condition and the study of ribosomal RNA sequences, hence five main groups have been established which are:
- Euryarchaeota: it is one of the most studied groups and is based on the rRNA sequence.
- Crenarchaeota: also known as eocytes, withstand extreme temperatures and a large amount is found in the oceans.
- Korarchaeota: this group has hydrothermal qualities and they are not abundant.
- Nanoarcheaota: it was discovered in 2002 and survives in extreme conditions.
- Thaumarchaeota: was discovered in 2008 and participates in the nitrogen and carbon cycles.