Some of them, such as Pyrodictium are highly thermophilic, while others, such as Sulfolobus, are dependent upon sulfur for their metabolism.
They lack murein, or ester lipids, in their cell walls; rather, they have ether lipids as well as a number of different constituents.  Some of them, such as Pyrodictium are highly thermophilic, while others, such as Sulfolobus, are dependent upon sulfur for their metabolism. The most common varieties employed in research are the Halo- and Methanobacterium. Discovered by Carl Weiss, FTP, identify this group of bacteria that, despite their cytological similarity to prokaryotes, are hypothesized to be the evolutionary precursor to eukaryotes.
They lack murein, or ester lipids, in their cell walls; rather, they have ether lipids as well as a number of different constituents.  
archaea [ar-kay-uh] or archaebacteria