A genomic analysis of the archaeal system Ignicoccus hospitalis-Nanoarchaeum equitans

Mircea Podar, Iain Anderson, Kira S. Makarova, James G. Elkins, Natalia Ivanova, Mark A. Wall, Athanasios Lykidis, Kostantinos Mavromatis, Hui Sun, Matthew E. Hudson, Wenqiong Chen, Cosmin Deciu, Don Hutchison, Jonathan R. Eads, Abraham Anderson, Fillipe Fernandes, Ernest Szeto, Alla Lapidus, Nikos C. Kyrpides, Milton H. SaierPaul M. Richardson, Reinhard Rachel, Harald Huber, Jonathan A. Eisen, Eugene V. Koonin, Martin Keller, Karl O. Stetter

Research output: Contribution to journalArticlepeer-review


Background: The relationship between the hyperthermophiles Ignicoccus hospitalis and Nanoarchaeum equitans is the only known example of a specific association between two species of Archaea. Little is known about the mechanisms that enable this relationship. Results: We sequenced the complete genome of I. hospitalis and found it to be the smallest among independent, free-living organisms. A comparative genomic reconstruction suggests that the I. hospitalis lineage has lost most of the genes associated with a heterotrophic metabolism that is characteristic of most of the Crenarchaeota. A streamlined genome is also suggested by a low frequency of paralogs and fragmentation of many operons. However, this process appears to be partially balanced by lateral gene transfer from archaeal and bacterial sources. Conclusions: A combination of genomic and cellular features suggests highly efficient adaptation to the low energy yield of sulfur-hydrogen respiration and efficient inorganic carbon and nitrogen assimilation. Evidence of lateral gene exchange between N. equitans and I. hospitalis indicates that the relationship has impacted both genomes. This association is the simplest symbiotic system known to date and a unique model for studying mechanisms of interspecific relationships at the genomic and metabolic levels.

Original languageEnglish (US)
Article numberR158
JournalGenome biology
Issue number11
StatePublished - Nov 10 2008

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Genetics
  • Cell Biology


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