Archaea

One of the three major classes major classes of living organisms; previously known as archaebacteria. They are unicellular mircoorganisms that are commonly found living in extreme abiotic conditions such as deep sea vents and extremely salty (hypersaline) waters. However, some species of archaea are also found living inside your gut, where they were first discovered in 1982.

The archaea wasn't recognised as a seperate domain of life until right up to the late 1970s when Dr. Carl Woese and his colleagues at the University of Illinois were studying relationships among the prokaryotes using DNA sequences. When archaea were first founded they were often grouped as prokaryotes alongside bacteria under the organism classification system as they do not contain any membrane bound nuclei. Many archaea and bacteria are quite similar in size and shape, although a few archaea have very unusual shapes, for example theHaloquadratum ("salt square"), a genus of the family Halobacteriaceae, which has a very unique structure that looks like flattened square boxes. Nevertheless despite the visual similarity to bacteria, archaea possess genes and several metabolic pathways that are more closely related to those of eukaryotes, notably the enzymes involved in transcription and translation.

The archaea are very different to the bacteria and eukaryota in they neither require sunlight for photosynthesis as do plants, nor oxygen. Archaea absorbs CO₂, N₂, or H₂S and give off methane gas as a waste product the same way humans breathe in oxygen and breathe out carbon dioxide.