"Candidatus Sukunaarchaeum mirabile" (provisional name) is a species of archaea of which only the DNA is known, but which already presents several particularities: it is a holoparasite of the dinoflagellate Citharistes regius and is the first known parasitic archaean. Its DNA, the smallest known for an archaeon, codes for only proteins necessary for reproduction.
The proposed name for the genus, "Ca. Sukunaarchaeum", is a reference to Sukunabikona ("renowned little lord"), a small Shinto deity associated with hot springs. The specific epithet, mirabile, means "astonishing, admirable, marvelous."
The DNA of "Ca. Sukunaarchaeum mirabile" is a circular molecule comprising 238 kilobase pairs (kbp), less than half the size of the smallest previously known archaeal DNA. This genome lacks almost all recognizable metabolic pathways, and primarily encodes the mechanisms of DNA replication, transcription, and translation. This suggests an unprecedented level of metabolic dependence on the host, a condition that challenges functional distinctions between minimal cellular life and viruses. Unlike viruses, "Ca. Sukunaarchaeum mirabile" has the ability to replicate its DNA, whereas viruses depend completely on their host organisms for replication.