Three domains
of life
Archaea, domain of life, Carl Woese, archaebacteria, single-cell organism, bacteria, extreme environment, extremophile, primitive bacteria, filament, cluster, methanogen, halophile, thermophile.
What are they?
Archaea are a type of single-celled or filament and cluster-style of organisms. They live in extreme environments, and are classed as an extremophile. This means they can cope with very high or very low temperatures, extreme inclements of weather, and even space.
Until the 1970s, archaea were classed as a type of bacteria. This was due to the fact that they share similar characteristics to bacteria.
So, archaea are single-celled organisms, which are also known as prokaryotes. These cells lack a nucleus, like a eukaryote.
Archaea comes from the Greek word archaios, which means 'ancient' or 'primitive'. They exhibit characteristics that prove them worthy of this name.
Arachaea is part of a term called classification. Every living organism is classified under these terms. From the single celled-organism such as bacteria and archaea, to the multi-celled organisms such as a banana, plant, or you! Yes, you are a eukaryote.
The Archaea domain is itself split into three different parts, including methanogens, halophiles and thermophiles. It is one of the newly discovered domains.
The three sub-sections of Archaea are fairly simple to explain:
Methanogens: these are mainly archaea that produce methane in some form, due to energy metabolism. They can be found in several places, including human digestive tracts, rice paddies, aquatic sediments and hydrothermal vents.
Halophiles: these archaea live in salt-rich environments - large salt flats like the Dead Sea, salt marshes. They love salt environments (hence the Halo part of the name), and they require the presence of salt in order to reproduce or survive.
Thermophiles: thermophiles love the heat, and these archaea grow in areas of extreme heat (above 40° Celcius/104° Fahrenheit).
Of these three sub-divisions, there can be archaea that cross between any two or three of these divisions.
To help you further, watch this YouTube video on the differences between bacteria and archaea.
In 1977, Carl Woese, an American microbiologist, analysed ribosomal RNA strands, and figured that what was then a single line of bacteria, needed to be split in two.
He defined them Eubacteria and Archaebacteria, which was later shortened to Archaea. Since then, it has been accepted that there are three major domains of life: Bacteria, Archaea and Eukaryota.
There has since been further development, with two subdivisions added, and a further three being considered to be added.
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