The Archaebacteria are a super-classification of odd
bacteria that are neither
prokaryotes nor
eukaryotes; some
scientists believe they represent a separate
kingdom. The primary
genus is
Archaebacteria, whose members fall in three categories:
microbes that can live in extremely
salty environments (
halophiles),
microbes that produce
methane (methanogens), and
microbes that can live in extremely
hot environments (thermophiles). All are of interest to
biotechnologists because they have
unique biochemical features (e.g., the
enzymes of the theromophiles are extremely
stable at high
temperatures).
From the science dictionary at http://biotech.icmb.utexas.edu/