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Euryarchaeota (from Ancient Greek εὐρύς eurús, "broad, wide") is a kingdom of archaea. [3] Euryarchaeota are highly diverse and include methanogens, which produce methane and are often found in intestines; halobacteria, which survive extreme concentrations of salt; and some extremely thermophilic aerobes and anaerobes, which generally live at temperatures between 41 and 122 °C.
Archaea were initially classified as bacteria, receiving the name archaebacteria (/ ˌ ɑːr k i b æ k ˈ t ɪər i ə /, in the Archaebacteria kingdom), but this term has fallen out of use. [5] Archaeal cells have unique properties separating them from Bacteria and Eukaryota. Archaea are further divided into multiple recognized phyla.
Combined with the five-kingdom model, this created a six-kingdom model, where the kingdom Monera is replaced by the kingdoms Bacteria and Archaea. [16] This six-kingdom model is commonly used in recent US high school biology textbooks, but has received criticism for compromising the current scientific consensus. [13]
The three-domain system adds a level of classification (the domains) "above" the kingdoms present in the previously used five- or six-kingdom systems.This classification system recognizes the fundamental divide between the two prokaryotic groups, insofar as Archaea appear to be more closely related to eukaryotes than they are to other prokaryotes – bacteria-like organisms with no cell nucleus.
The bacteria and archaea are thought to be the most ancient of lineages, [21] as fossil strata bearing the chemical signature of archaeal lipids have been dated back to 3.8 billion years ago. [22] The eukaryotes include all complex cells and almost all multicellular organisms. They are thought to have evolved between 1.6 and 2.1 billion years ...
The most recent common ancestor (MRCA) of bacteria and archaea was probably a hyperthermophile that lived about 2.5 billion–3.2 billion years ago. [16] [17] [18] The earliest life on land may have been bacteria some 3.22 billion years ago. [19] Bacteria were also involved in the second great evolutionary divergence, that of the archaea and ...
"The neomuran origin of archaebacteria, the negibacterial root of the universal tree and bacterial megaclassification". Int. J. Syst. Evol. Microbiol. 52 (Pt 1): 7– 76. doi: 10.1099/00207713-52-1-7. PMID 11837318. Woese, CR; Kandler O; Wheelis ML (1990). "Towards a natural system of organisms: proposal for the domains Archaea, Bacteria, and ...
The cells of Aeropyrum pernix are spherical in shape and approximately 1 μm in diameter. The envelope surrounding the cells of Aeropyrum is about 25 nm wide. The organisms grows at temperature between 70 and 100 °C (optimum, 90 to 95 °C), at pH 5 to 9 (optimum, pH 7), and at a salinity of 1.8 to 7% (optimum, 3.5% salinity).