Species: Hospitalis 
Description and Significance
I. hospitalis is a newly discovered hyperthermophile with many interesting features. Most unique, however, is its ability to serve as a host for the microbe Nanoarchaeum equitans.  This feature of I. hospitalis is striking because it is the first known hyperthermophilic archaeon to have this capability.  At present, it is not known whether the relationship between these two species is parasitic or symbiotic.  The species name, hospitalis was chosen due to its hosting ability. Besides that unique feature, I. hospitalis is an irregular cocci about 1-6μm in diameter.  These microbes are typically found in pairs. They are chemolithoautotrophs that grow exclusively by reducing sulfur.  Like the other members of their genus, they exhibit a cell envelope that consists of a plasma membrane, periplasmic space, and an outer membrane. 
Structure, Metabolism, and Life Cycle
I. hospitalis is an irregular cocci that is 1-6μm in diameter. It has up to nine flagella arranged at one pole of the cell, making it lophotrichous.  The periplasmic space that is part of the cell envelope of I. hospitalis varies significantly in width from one organism to another; a range of 20-500 nm has been observed. The outer membrane is predominately composed of a protein called Imp1227 (Ignicoccus outer-membrane protein) .
I. hospitalis is an obligate anaerobic chemolithoautotroph. It obtains all of its energy from reducing sulfur and has hydrogen as its only electron donor . As a result of its metabolic pathway, large amounts of hydrogen sulfide (H2S) is produced by this microbe.
The life cycle of I. hospitalis has no unique features. At optimal growth conditions, doubling time is around one hour .
Ecology and Pathogenesis
I. hospitalis is a hyperthermophilic organism that was first isolated from the Kolbeinsey Ridge, a hydrothermal vent system north of Iceland. It is also considered a moderate acidophile and a moderate halophile due to its optimal growth at pH 5.5 and 1.4% NaCl.  I. hospitalis has no known pathogenic properties.
 Paper W, Jahn U, Hohn MJ, Kronner M, Nather DJ, Burghardt T, Rachel R, Stetter KO, Huber H. 2007. "Ignicoccus hospitalis sp. nov., the host of 'Nanoarchaeum equitans'. Int. J Syst Evol Microbiol. 57:803-808.
 Waters E, Hohn MJ, Ahel I, Graham DE, Adams MD, Barnstead M, Beeson KY, Bibbs L, Bolanos R. 2003. The genome of Nanoarchaeum equitans: insights into early archaeal evolution and derived parasitism. Proc Natl Acad Sci USA. 100:12984–12988.
 Huber H, Hohn MJ, Rachel R, Fuchs T, Wimmer VC, Stetter KO. 2002. A new phylum of Archaea represented by a nanosized hyperthermophilic symbiont. Nature. 417:63–67.
 Rachel R, Wyschkony I, Riehl S, Huber H. 2002. The ultrastructure of Ignicoccus: evidence for a novel outer membrane and for intracellular vesicle budding in an archaeon. Archaea. 1:9–18.
Page authored by Andrea Richard, student of Mandy Brosnahan, Instructor at the University of Minnesota-Twin Cities, MICB 3301/3303: Biology of Microorganisms.