Sulfolobus  

What you should know:

Sulfolobus is a sulfur-oxidizing thermoacidophile. This member of the Archaea is usually round, but forms pseudopod-like extensions (lobes) seen above. It is usually lithotrophic, oxidizing sulfur to sulfate.

Classification: 

Domain Archaea

    Phylum Crenarchaeota

        Class Thermoprotei

Bergey's Manual Volume 1: The Archaea and the deeply branching and phototrophic Bacteria