An example of an s layer 47 brock biology of

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Unformatted text preview: Cell walls of Archaea •  PepAdoglycan is absent in the cell wall of Archeae and there is usually no outer- membrane. •  Cell walls of Archaea are diverse and may consist of proteins (usually), polysaccharides, and/or glycoproteins. •  The structure of pseudomurein (pseudopepAdoglycan) is similar to pepAdoglycan. It contains N- acetyltalosaminuronic acid instead of NAM and lacks D- amino acids. •  The linkage between the sugars is insensiAve to lysozyme, contrary to pepAdoglycan. 46 Brock Biology of Microorganisms, 13th EdiAon. Cell walls of Archaea •  Some species of Archaea have a cell walls composed of repeaAng units of two or more sugars – heteropolysaccharides. •  The great majority of cell walls of of Archaeal species consists of proteins and/ or glycoproteins. •  These cell walls have a crystalline appearance when viewed by electron microscopy and are referred to as paracrystalline surface layers or S- layers. •  A S- layer may also be found in some species of bacteria. In this case the S- layer forms an addiAonal layer on top of pepAdoglycan (Gram- posiAve) or on top of the outer membrane (Gram- negaAve). An example of an S- layer 47 Brock Biology of Microorganisms, 13th EdiAon. Capsule and slime layers of prokaryotes (Bacteria/Archaea) •  Prokaryotes species may synthesize another layer known as the capsule or slime layer depending on its consistency. The capsule or slime layer does not confer significant strength to the cell. •  Composed of polysaccharides (vast majority) or proteins. –  Heteropolysaccharides (Majority of bacteria) –  Homopolysacchrides (Some Gram- negaAve) •  The capsule may be covalently bound to the outer membrane or to the pepAdoglycan layer. •  The capsule is a very important virulence determinant for capsulated bacterial pathogens – the capsule protects against the host defense system. Brock Biolo...
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This note was uploaded on 03/20/2014 for the course PSYC 101 taught by Professor Catone during the Spring '07 term at CSU Fullerton.

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