Ignicoccus


Ignicoccus is a genus of Archaea living in marine hydrothermal vents. They were discovered in Kolbeinsey Ridge north of Iceland and in the Pacific Ocean in 2000.

Systematics

According to the comparisons of 16S rRNA genes, Ignicoccus represents a new, deeply branching lineage within the family of the Desulfurococcaceae. 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, and an outer membrane. The latter contains numerous tightly, irregularly packed single particles and pores with a diameter of 24 nm, surrounded by tiny particles, arranged in a ring and clusters of up to eight particles .

Physiology

Ignicocci live in a temperature range of 70–98 °C. They gain energy by reduction of elemental sulfur to hydrogen sulfide using molecular hydrogen as the electron donor. A unique symbiosis with Nanoarchaeum equitans has also been reported.