Thermoproteati is akingdom ofarchaea. Itssynonym, "TACK", is an acronym for Thaumarchaeota (nowNitrososphaerota),Aigarchaeota, Crenarchaeota (nowThermoproteota), andKorarchaeota, the first groups discovered. They are found in different environments ranging fromacidophilicthermophiles tomesophiles andpsychrophiles and with different types ofmetabolism, predominantly anaerobic and chemosynthetic.[4] Thermoproteati is a kingdom that is sister to theAsgard branch that gave rise to theeukaryotes. It has been proposed that the Thermoproteati kingdom be classified as "Crenarchaeota" and that the traditional "Crenarchaeota" (Thermoproteota) be classified as a class called "Sulfolobia", along with the other phyla with class rank or order.[5] After including thekingdom category intoICNP, the onlyvalidly published name of this group is kingdomThermoproteati (Guy and Ettema 2024).[6]
Thermoproteota (formerly Crenarchaeota). It is the best known edge and the most abundantarchaea in the marine ecosystem. They were previously called sulfobacteria because of their dependence on sulfur and are important as carbon fixers. There arehyperthermophiles in hydrothermal vents and other groups are the most abundant at depths of less than 100 m.
"Aigarchaeota". It is a phylum proposed from the genome of the candidate speciesCaldiarchaeum subterraneum found deep within a gold mine inJapan. Genomic sequences of this group have also been found in geothermal environments, both terrestrial and marine.
"Geoarchaeota". It includes thermophilic organisms that live in acidic environments reducing ferric iron. Alternatively it has been proposed that this and earlier group actually belong to the phylum Nitrososphaerota.
"Nitrososphaerota" (formerly Thaumarchaeota). It includes mesophilic or psychrophilic organisms (medium and low temperatures), of ammonia-oxidant chemolytoautotrophic metabolism (nitrifying) and that can play an important role in biochemical cycles, such as the nitrogen and carbon cycles.
"Bathyarchaeota". It is abundant in the sediments of the seabed with a shortage of nutrients. At least some lineages develop through homoacetogenesis, a type of metabolism hitherto thought unique to bacteria.
"Korarchaeota". They have only been found in hydrothermal environments and in low abundance. They seem diversified at different phylogenetic levels according to temperature, salinity (fresh or marine water) and geography.
One piece of evidence supporting a close relationship between Thermoproteati and eukaryotes is the presence of a homolog of theRNA polymerase subunit Rbp-8 in Thermoproteota but not in Euryarchaea.[16]
^Guy, Lionel; Ettema, Thijs J.G. (2011). "The archaeal 'TACK' superphylum and the origin of eukaryotes".Trends in Microbiology.19 (12):580–587.doi:10.1016/j.tim.2011.09.002.PMID22018741.
