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Unformatted text preview: MODULE 10 10a) Overview of Archaea • Only recently recognized as group of organisms • Tend to inhabit extreme environments o High temp o Acidic or alkaline pH o High salt concentrations • Many actually require these extreme conditions to grow and reproduce • Pathogenic examples of these do not seem to exist Phylogenetic Overview • Halophilic Archaea: salt tolerant • Methanogens • Thermoplasmateles: similar to microplasmas, no cell wall, exist at high temp and acidic pH • Subgroups; euryarchaeota, crenarchaeota • Euryaechaeota: o Methanogens o Thermoplasmas: no cell wall, grow well at high temp and acidic pH o Thermococcus/pyrococcus: grow at temp above boiling water o Halophiles: grow at high salt concentrations • Marine euryarchaeota and marine crenarchaeota o Only know these organisms from their DNA sequence o Marine environments usually associated with marine bacterial plankton o Comprise large fraction of bacterial biomass of ocean o Related to organisms that are often thermophilic, but grow at moderate or cold temp 10b) Extreme Halophiles Overview • Can tolerate extremely high salt concentrations • Some can grow in conditions where salt will precipitate out of solution (5M or more NaCl) • Typically chemoorganotrophs and obligate aerobes • Halobacterium is organism most extensively studied in this group • High salt concentrations has role in stabilizing glycoproteins in cell wall • Potassium ion is compatible solute in order to maintain water balance in the cell • High sodium outside cell, high potassium inside cell • Some can use light to generate ATP using non-photosynthetic mechanism, uses carotenoid pigment called rhodopsin instead of chlorophyll Habitats • Green pigment is from eukaryotic green algae which is predominant form of life...
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This note was uploaded on 06/26/2011 for the course BIOL 140 taught by Professor Dr.joshneufeld during the Winter '10 term at Waterloo.
- Winter '10