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