''Ignicoccus'' is a genus of hyperthermophillic

Archaea Archaea ( ) is a Domain (biology), domain of organisms. Traditionally, Archaea only included its Prokaryote, prokaryotic members, but this has since been found to be paraphyletic, as eukaryotes are known to have evolved from archaea. Even thou ...

living in marine

hydrothermal vent Hydrothermal vents are fissures 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 hot ...

s. They were discovered in samples taken at the Kolbeinsey Ridge north of

Iceland Iceland is a Nordic countries, Nordic island country between the Atlantic Ocean, North Atlantic and Arctic Oceans, on the Mid-Atlantic Ridge between North America and Europe. It is culturally and politically linked with Europe and is the regi ...

, as well as at the

East Pacific Rise The East Pacific Rise (EPR) is a mid-ocean rise (usually 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), at a divergent tectonic plate bound ...

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

Systematics

According to the comparisons of

16S rRNA 16S ribosomal RNA (or 16Svedberg, S rRNA) is the RNA component of the 30S subunit of a prokaryotic ribosome (SSU rRNA). It binds to the Shine-Dalgarno sequence and provides most of the SSU structure. The genes coding for it are referred to as ...

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

Desulfurococcaceae 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 the order Desulfuroc ...

. 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 Monolayer, monomolecular layer composed of only one (or, in a few c ...

. 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 bacterial outer membrane, outer membrane is also included. This envelope is not present in the Mollicutes where the cell wall is abse ...

structure—a cytoplasmic membrane, a periplasmic space (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, unlike gram-positive bacteria, do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. Their defining characteristic is that their cell envelope consists ...

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''.

Physiology

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

sulfur Sulfur ( American spelling and the preferred IUPAC name) or sulphur ( Commonwealth spelling) is a chemical element; it has symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms ...

hydrogen sulfide Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is toxic, corrosive, and flammable. Trace amounts in ambient atmosphere have a characteristic foul odor of rotten eggs. Swedish chemist ...

using molecular hydrogen as the

electron donor In chemistry, an electron donor is a chemical entity that transfers electrons to another compound. It is a reducing agent that, by virtue of its donating electrons, is itself oxidized in the process. An obsolete definition equated an electron dono ...

. A unique symbiosis with (or parasitism by) '' Nanoarchaeum equitans'' has also been reported.

Phylogeny

The currently accepted taxonomy is based on the

List of Prokaryotic names with Standing in Nomenclature List of Prokaryotic names with Standing in Nomenclature (LPSN) is an online database that maintains information on the naming and taxonomy of prokaryotes, following the taxonomy requirements and rulings of the International Code of Nomenclatu ...

(LPSN) and

National Center for Biotechnology Information The National Center for Biotechnology Information (NCBI) is part of the National Library of Medicine (NLM), a branch of the National Institutes of Health (NIH). It is approved and funded by the government of the United States. The NCBI is lo ...

(NCBI)

References

External links

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