Ignicoccus Explained

Ignicoccus is a genus of hyperthermophillic Archaea living in marine hydrothermal vents. They were discovered in samples taken at the Kolbeinsey Ridge north of Iceland, as well as at the East Pacific Rise (at 9 degrees N, 104 degrees W) in 2000.^[1]

Systematics

According to the comparisons of 16S rRNA genes, Ignicoccus represents a new, deeply branching lineage within the family of the Desulfurococcaceae.^[2] 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.

They have a previously unknown cell envelope 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 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.^[3]

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.^[4]

Physiology

Ignicocci live in a temperature range of 70–98 °C (optimum around 90 °C). They gain energy by reduction of elemental sulfur to hydrogen sulfide using molecular hydrogen as the electron donor. 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 (LPSN) ^[5] and National Center for Biotechnology Information (NCBI)^[6]

See also

• List of Archaea genera

Further reading

• Huber H, Kueper U, Daxer S, Rachel R . The unusual cell biology of the hyperthermophilic Crenarchaeon Ignicoccus hospitalis . Antonie van Leeuwenhoek . August 2012 . 102 . 2 . 203–219 . 10.1007/s10482-012-9748-5 . 22653377 . 7732441 . subscription.
• Nass B, Poll U, Langer JD, Kreuter L, Kuper U, Flechsler J, Heimer T, Rachel R, Huber H, Kletzin A . Three multihaem cytochromes c from the hyperthermophilic archaeon Ignicoccus hospitalis: purification, properties and localization . Microbiology. 2014 . 6 . 160 . 1278–1289. 10.1099/mic.0.077792-0 . free . 24705227 .

External links

• Ignicoccus at BacDive - the Bacterial Diversity Metadatabase

Notes and References

1. Huber H, Burggraf S, Mayer T, Rachel R, Stetter KO . Ignicoccus gen. nov., a novel genus of hyperthermophilic, chemolithoautotrophic Archaea, represented by two new species, Ignicoccus islandicus sp nov and Ignicoccus pacificus sp nov. and Ignicoccus pacificus sp. nov . International Journal of Systematic and Evolutionary Microbiology. November 2000 . 50 . 6 . 2093–2100 . 10.1099/00207713-50-6-2093 . free . 11155984 .
2. Huber H, Hohn MJ, Rachel R, Fuchs T, Wimmer VC, Stetter KO . A new phylum of Archaea represented by a nanosized hyperthermophilic symbiont . Nature . 2 May 2002 . 417 . 6884 . 63–67 . 10.1038/417063a . 11986665 . 2002Natur.417...63H . 4395094 . subscription.
3. Rachel R, Wyschkony I, Riehl S, Huber H . The ultrastructure of Ignicoccus: evidence for a novel outer membrane and for intracellular vesicle budding in an archaeon . Archaea . March 2002 . 9–18 . 10.1155/2002/307480 . free . 15803654 . 685547 . 1 . 1 .
4. Heimerl T, Flechsler J, Pickl C, Heinz V, Salecker B, Zweck J, Wanner G, Geimer S, Samson RY, Bell SD, Huber H, Wirth R, Wurch L, Podar M, Rachel R . A Complex Endomembrane System in the Archaeon Ignicoccus hospitalis Tapped by Nanoarchaeum equitans . Frontiers in Microbiology . 8 . 1072 . 13 June 2017 . 28659892 . 5468417 . 10.3389/fmicb.2017.01072 . free .
5. Web site: J.P. Euzéby . Ignicoccus . 2023-06-10 . List of Prokaryotic names with Standing in Nomenclature (LPSN).
6. Web site: Sayers. etal. Ignicoccus . 2023-06-10 . National Center for Biotechnology Information (NCBI) taxonomy database.
7. Web site: The LTP . 10 May 2023.
8. Web site: LTP_all tree in newick format. 10 May 2023.
9. Web site: LTP_06_2022 Release Notes. 10 May 2023.
10. Web site: GTDB release 08-RS214 . Genome Taxonomy Database. 10 May 2023.
11. Web site: ar53_r214.sp_label . Genome Taxonomy Database. 10 May 2023.
12. Web site: Taxon History . Genome Taxonomy Database. 10 May 2023.