Korarchaeota
In taxonomy, the Korarchaeota are a phylum of the Archaea. The name is derived from the Greek noun koros or kore, meaning "young man" or "young woman," and the Greek adjective archaios which means "ancient." They are also known as Xenarchaeota. Taxonomy. Korarchaeota is regarded as a phylum, which itself is part of the archaeal TACK superphylum which encompasses Thaumarchaeota (now Nitrososphaerota), "Aigarchaeota", Crenarchaeota (now Thermoproteota), and "Korarchaeota". Phylogeny. Analysis of their 16S rRNA gene sequences suggests that they are a deeply branching lineage that does not belong to the main archaeal groups, Thermoproteota and Euryarchaeota. Analysis of the  genome of one korarchaeote that was enriched from a mixed culture revealed a number of both Crenarchaeota- and Euryarchaeota-like features and supports the hypothesis of a deep-branching ancestry. Reference species. The strain "Korarchaeum cryptofilum" was cultivated in an enrichment culture from a hot spring in Yellowstone National Park in USA 2008. The cells are long and needleshaped, which gave the species its name, alluding to its "cryptical filaments". This organism lacks the genes for purine nucleotide biosynthesis and thus relies on environmental sources to meet its purine requirements. Ecology. The Korarchaeota have only been found in hydrothermal environments . They appear to have diversified at different phylogenetic levels according to temperature, salinity (freshwater or seawater), and/or geography. Korarchaeota have been found in nature in only low abundance.