General Biology/Classification of Living Things/Prokaryotes

For Eubacteria, please visit General Biology/Classification of Living Things/Eubacteria.

Archaea

 * Proposed as separate group from (eu)bacteria by Carl Woese
 * based on structure and metabolic pathways
 * inhabit extreme environments
 * unique branched lipids in membrane
 * Share traits with both eukaryotes and eubacteria, e.g., RNA polymerase, introns
 * Biochemically diverse
 * Economically important
 * Taq polymerase used in PCR

Types

 * Methanogens
 * Halophiles
 * Thermophiles

Underground bacteria

 * Metabolism
 * built around inorganic energy sources
 * e.g., basalt reacts with H2O to release hydrogen which is catalytically combined with CO2 to form carbohydrate (akin to photosynthesis)
 * may result in deposit of minerals
 * Unresolved problems
 * Did bacteria move downward from surface or did they first evolve there, protected from harsh surface conditions?
 * Could bacteria be ejected into space in rocks?

Prokaryote evolution

 * Tentative, subject to change
 * Derived largely from molecular systematics (rRNA sequences)
 * Note: most bacteria can’t be cultured, thus hard to study! (Studied by PCR of water/soil samples)

Domains of life: characteristics
This text is based on notes very generously donated by Paul Doerder, Ph.D., of the Cleveland State University.