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.