BIOL 2004 Lecture Notes - Lecture 17: Pseudopeptidoglycan, Euryarchaeota, Membrane Lipids
30 Mar 2017
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Document Summary
Many are extremophiles: most of the first archaea isolated were found in an extreme environment. Few internal cell structures: usually single circular chromosome + operons o o. Important differences from bacteria (in favour of archaea: archaea-specific features - cell membrane and envelope composition. S-layers are common: membrane lipids are completely different from lipids in bacteria and eukaryotes. Isoprenoids (assembled from isoprene units) - branched chain lipids. Methionine as initiator amino acid (bacteria use n-formylmethionine. Some grow in temperatures higher than 90c, and even 120c: many thermophiles are lithoautotrophs. Primarily, geothermal sites: hot springs, vents, deep in earths crust, etc. Sources of h2, h2s, sulfur (s0) o o e. g. eat h2, with s0 as electron acceptor (h2 + s0 --> h2s) Structurally stable (and active) at high temperatures: membranes - increased integrity and rigidity. Archaeal membrane lipids more stable in first place. Additional characteristics e. g. , tetraethers (increases stability even more) in some archaea: dna stabilisation (esp. avoiding denaturation)
