Archaeoglobus
Ferroglobus
The Archaeoglobi are a family of Archaea, with two genera. Both are hyperthermophiles, found in undersea hydrothermal vents.
Ferroglobus is chemoautotrophic, oxidizing iron salts from Fe2+ to Fe3+, and at the same time reducing nitrate to nitrite.
Archaeoglobus is unique among the Archaea in using sulfate as its oxidizing agent, although there are various sulfate-reducing bacteria that do the same.