They are unicellular and are prokaryotic. They are asexual. Depending on the cell they can be both heterotrophic or autotrophic. But this one is heterotrophic and it eats the other cells that cannot survive well in the high conditions that he can live in. These cells are in the kingdom Archea and they are in the domain of Archeabacteria. The Thermoplasma Volcanium can grow best when it's in between a 55-65 degrees place.

Archaebacteria: Thermoplasma Volcanium