Methanocaldococcus jannaschii (formerly Methanococcus jannaschii) is a thermophilic methanogenic archaean in the class Methanococci that lives at temperatures from 48° to 94 °C and at pressures of more than 200 atmospheres. It was the first archaeon, and third organism, to have its complete genome sequenced. The sequencing identified many genes unique to the archaea. Many of the synthesis pathways for methanogenic cofactors were worked out biochemically in this organism, as were several other archaeal-specific metabolic pathways.

Closest relatives