Eli5: What exactly are archaea?

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Eli5: What exactly are archaea?

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They’re a large group of single-celled organisms, as varied as plants or animals or bacteria. They’re very common in almost every environment, but because no known archaea cause disease, because they’re not currently economically important, and because the fact that they’re a distinct group from bacteria is a relatively recent discovery, they get less press than bacteria.

There are three domains of life – Archaea, Bacteria, and Eukaryota

Eukaryota is the easiest to explain – they have a casing around the nucleus called a nuclear envelope. Basically, Eukaryotes separate their DNA from the rest of the cell. Eukaryotes include all plants, animals, and fungi. Almost all Eukaryotes (with maybe a few exceptions) use mitochondria to produce energy from food.

Bacteria and Archaea do not do that, so they are called Prokaryotes – they dk not have nuclear envelopes and they do not use mitochondria. The differences between those two domains are a bit more complex.

Archaea use a different chemical to make their outer membrane than bacteria do. They also use different structures for movement, and can thrive in extreme environments bacteria cannot (extreme temperature, high salt, etc.)

We weren’t even aware of some of these differences until relatively recently. It wasn’t until the 1970’s that DNA sequencing showed Archaea to be as genetically distant from bacteria as bacteria is from humans.

Archaea are a group of single-celled organisms. Along with the bacteria and the eukaryotes (which include all multicellular life, including you and me) they are one of the three main domains of life, the earliest branches from the origins of life on Earth.

Achaea are superficially similar to bacteria, being single cells without a nucleus. However a study of their genes suggests that they are more closely related to the eukaryotes, and that eukaryotes may have themselves evolved from archaea.

It was initially thought that all archaea were extremophiles, organisms that only live in extremely hostile environments that others cannot tolerate such as hydrothermal vents and salt lakes. However, we now know that archaea are present all over the world, including in oceanic plankton and the human microbiome. There is, however, no known example of an archaea pathogen.