''Ignicoccus'' is a genus of hyperthermophillic Archaea living in marine

hydrothermal vent A hydrothermal vent is a fissure on the seabed from which geothermally heated water discharges. They are commonly found near volcanically active places, areas where tectonic plates are moving apart at mid-ocean ridges, ocean basins, and hotspot ...

s. They were discovered in samples taken at the

Kolbeinsey Ridge The Kolbeinsey Ridge is a segment of the Mid-Atlantic Ridge located to the north of Iceland in the Arctic Ocean. It is bounded to the south by the Tjörnes Fracture Zone, which connects the submarine ridge to the on-shore Northern Volcanic Zone ri ...

north of

Iceland Iceland ( is, Ísland; ) is a Nordic island country in the North Atlantic Ocean and in the Arctic Ocean. Iceland is the most sparsely populated country in Europe. Iceland's capital and largest city is Reykjavík, which (along with its s ...

, as well as at the

East Pacific Rise The East Pacific Rise is a mid-ocean rise (termed an oceanic rise and not a mid-ocean ridge due to its higher rate of spreading that results in less elevation increase and more regular terrain), a divergent tectonic plate boundary located along ...

(at 9 degrees N, 104 degrees W) in 2000.

Systematics

According to the comparisons of 16S

rRNA Ribosomal ribonucleic acid (rRNA) is a type of non-coding RNA which is the primary component of ribosomes, essential to all cells. rRNA is a ribozyme which carries out protein synthesis in ribosomes. Ribosomal RNA is transcribed from ribosomal ...

genes, ''Ignicoccus'' represents a new, deeply branching lineage within the family of the

Desulfurococcaceae In taxonomy, the Desulfurococcaceae are a family of the disc-shaped anaerobic microorganisms belonging to the order Desulfurococcales, in the domain Archaea. Members of this family are distinguished from the other family ( Pyrodictiaceae) in th ...

. Three species are known: ''I. islandicus'', ''I. pacificus'' and ''I. hospitalis'' strain KIN4I.

Cell structure

The archaea of the genus ''Ignicoccus'' have tiny coccoid cells with a diameter of about 2 µm, that exhibit a smooth surface, an outer membrane and no

S-layer An S-layer (surface layer) is a part of the cell envelope found in almost all archaea, as well as in many types of bacteria. The S-layers of both archaea and bacteria consists of a monomolecular layer composed of only one (or, in a few cases, two) ...

. They have a previously unknown

cell envelope The cell envelope comprises the inner cell membrane and the cell wall of a bacterium. In gram-negative bacteria an outer membrane is also included. This envelope is not present in the Mollicutes where the cell wall is absent. Bacterial cell enve ...

structure—a cytoplasmic membrane, a

periplasmic space The periplasm is a concentrated gel-like matrix in the space between the inner cytoplasmic membrane and the bacterial outer membrane called the ''periplasmic space'' in gram-negative bacteria. Using cryo-electron microscopy it has been found that ...

(with a variable width of 20 to 400 nm, containing membrane-bound vesicles), and an outer membrane (approximately 10 nm wide, resembling the outer membrane of

gram-negative Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wall ...

bacteria). The latter contains numerous tightly, irregularly packed single particles (about 8 nm in diameter) and pores with a diameter of 24 nm, surrounded by tiny particles, arranged in a ring (with a diameter of 130 nm) and clusters of up to eight particles 12 nm in diameter each. The two layers of membrane previously reported are actually a type of endomembrane system consisting of cytoplasmic protrusions. In ''I. hospitalis'', these structures harbor the endosymbiotic archaeon ''

Nanoarchaeum equitans ''Nanoarchaeum equitans'' is a species of marine archaea that was discovered in 2002 in a hydrothermal vent off the coast of Iceland on the Kolbeinsey Ridge by Karl Stetter. It has been proposed as the first species in a new phylum. Strains of ...

''.

Physiology

''Ignicocci'' live in a temperature range of 70–98 °C (optimum around 90 °C). They gain energy by reduction of elemental

sulfur Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...

to hydrogen sulfide using molecular hydrogen as the

electron donor In chemistry, an electron donor is a chemical entity that donates electrons to another compound. It is a reducing agent that, by virtue of its donating electrons, is itself oxidized in the process. Typical reducing agents undergo permanent chemi ...

. A unique symbiosis with (or parasitism by) ''

'' has also been reported.

Phylogeny

References

External links

''Ignicoccus'' at Bac''Dive'' - the Bacterial Diversity Metadatabase
{{Taxonbar, from=Q290183 Archaea genera Thermoproteota Thermophiles Extremophiles