Ignicoccus hospitalis KIN4/I

An anaerobic chemolithoautotrophic and hyperthermophilic archaeon, Ignicoccus hospitalis was isolated from a submarine hydrothermal system off the coast of Iceland. Optimal growth occurs at 90 degrees C utilizing molecular hydrogen, elemental sulfur, and carbon dioxide as the energy substrate, the electron acceptor, and the carbon source, respectively. It is the obligatory host of Nanoarchaeum equitans; up to a dozen N.equitans can be found on the surface of I.hospitalis without doing any apparent harm to the host. Ignicoccus species are unique among the Archaea in having two cell membranes; together with the cytoplasmic membrane, it encloses a huge periplasmic space, in which membrane-bound vesicles are found. I.hospitalis at 1.3 Mb has one of the smallest genomes among free-living bacteria and archaea, and shows signs of gene exchange with N.equitans as well as gene acquisition from Euryarchaeota and bacteria (adapted from PMID 19000309). (HAMAP: IGNH4)