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The Thermoproteota are prokaryotes that have been classified as a phylum of the domain Archaea. [2] [3] [4] Initially, the Thermoproteota were thought to be sulfur-dependent extremophiles but recent studies have identified characteristic Thermoproteota environmental rRNA indicating the organisms may be the most abundant archaea in the marine environment. [5]
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.
A significant amount of research has been done on the metabolism of Thermoproteus and other hyperthermophiles as well.Thermoproteus metabolizes autotrophically through sulfur reduction, but it grows much faster by sulfur respiration in cultivation.
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 origin of eukaryotes from Archaea, meaning the two are of the same larger group, came to be supported by studies based on ribosome protein sequencing and phylogenetic analyses in 2004. [ 30 ] [ 31 ] Phylogenomic analysis of about 6000 gene sets from 185 bacterial, archaeal and eukaryotic genomes in 2007 also suggested origin of eukaryotes ...
In 2016, Madeline C. Weiss and colleagues genetically analyzed 6.1 million protein-coding genes and 286,514 protein clusters from sequenced prokaryotic genomes representing many phylogenetic trees, and identified 355 protein clusters that were probably common to the LUCA. The results of their analysis are highly specific, though debated.
Two kingdoms, Archaebacteria (archaea) and Eubacteria (for bacteria) were established. [22] Based on further studies, Woese, Otto Kandler and Mark Wheelis introduced the concept of "domain" in 1990 as the highest level of biological classification, and proposed the three-domain system consisting of Eucarya, Bacteria and Archaea. [23]