MICRB 265 (09/20/13) Structure and Function (con't)

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Microbiology (Biological Sciences)
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Brian Lanoil

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MICRB 265 (September 20, 2013) Structure and Function (con’t)  In g-ve bacteria, the inner and outer membranes are VERY different o The outer membrane is very complex (and therefore very important) while the inner membrane is quite simple  Lipoproteins link the membrane to the periplasm  Lipopolysaccharides are very important to g-ve cells o Barrier o Exact composition is different for each organism but there the basic order is uniform  Lipid A  ketodeoxyoctonate  core  O specific  Lipid A is an endotoxin to animals (only known endotoxin)  O-specific polysaccharides have the same structure in all g-ve bacteria and the number of monomers it consists of can vary  Lipid A connects to the lipid bilayer Porin  is there to facilitate the transport of small hydrophilic substances  Molecules < 600 Daltons can pass through Periplasmic Space  Contains enzymes that help the cell acquire nutrients and aid in metabolism  Very small in g-ve bacteria and just about non-existent in g+ve bacteria o To acquire nutrients, g+ve bacteria will secrete exoenzymes that will help with nutrient transport  Exoenzymes – enzymes put out into environment (eg. Witnessed in positive blood agar plates) Capsule and Slime Layers  Not part of the cell itself (cell excretes this so it is not chemically linked to it) Negative stain – stains everything but what you want to see  This polysaccharide matrix is important for survival, protection, and virulence (of certain prokaryotic species) o Attachment and protection are the main functions Cellular Inclusions  Carbon storage o Consist of Poly-β-hydroxtbutyrate granules o In both bacteria and archaea o Sugar  (storage)  PHB  Sulfur Storage o Sulfur granules inside cell o Sulphide eaten using light to convert it into elemental sulfur and then sulfur is stored  Until it needs energy:  Then it can take e from by converting it into sulphite o Ex. Purple sulfur bacterium  Magnetosomes o Allow for bacterial orientation and migration along the Earth’s magnetic fields o Usually associated with oxygen levels o Cell takes in magnetic particles and forms them into dense membrane-bound inclusions o Inclusions line up in a row  Gas Vessicles o Vital for aquatic microorganisms  Allows organism to float o In or
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