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Ways to think about peptidoglycan

Ways to think about peptidoglycan. Bacterial Cell Structure (continued). You are here. Gram negative cell wall. Outer membrane. Lipid bilayer membrane: Asymmetric Inner and outer leaflets Inner leaflet made of phospholipids; outer leaflet is made of lipopolysaccharide (LPS)

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Ways to think about peptidoglycan

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  1. Ways to think about peptidoglycan

  2. Bacterial Cell Structure (continued) You are here.

  3. Gram negative cell wall

  4. Outer membrane • Lipid bilayer membrane: Asymmetric • Inner and outer leaflets • Inner leaflet made of phospholipids; outer leaflet is made of lipopolysaccharide (LPS) • LPS = endotoxin • Proteins for transport of substances • Porins: tri-subunit, transmembrane proteins • Barrier to diffusion of various substances • Lipoprotein: anchors outer membrane to PG

  5. Structure of LPS extends from cell surface. contains odd sugars e.g. KDO. Gln-P and fatty acids take the place of phospholipids. www.med.sc.edu:85/fox/ cell_envelope.htm

  6. Periplasmic Space www.arches.uga.edu/~emilyd/ theory.html

  7. Periplasm • The periplasm is the “stuff” in that space, • A hydrated gel including the PG • Binding proteins that aid in transport • Hydrolytic enzymes for breaking down large molecules • Chemoreceptor proteins that help direct swimming • Enzymes for synthesizing PG, OM • Must be in Gram + bacteria also.

  8. Glycocalyx: capsules and slime layers “Sugar covering”: capsules are firmly attached, slime layers are loose. Multiple advantages to cells: prevent dehydration absorb nutrients protection from predators, WBCs protection from biocides (as part of biofilms) attachment to surfaces and site of attachment by others. cell capsule www.activatedsludge.info/ resources/visbulk.asp

  9. Non-Carbohydrate layers • S Layers • Crystalline, protein layers • Found widely in Archaea, also in G- and G+ • Polypeptide capsule • B. anthracis has a poly D-glutamic acid capsule • TEM image of a freeze-etching preparation of a bacterial cell exhibiting an S-layer with square (p4) lattice symmetry. Bar, 100nm • http://www.nano.boku.ac.at/1143.html?&L=1

  10. Fimbriae and pili Both are appendages made of protein Singular: fimbria, pilus Both used for attachment Fimbriae: to surfaces (incl. host cells) and other bacteria. Pili: to other bacteria for exchanging DNA (“sex”). www.ncl.ac.uk/dental/oralbiol/ oralenv/images/sex1.jpg

  11. Fimbriae and pili-2 http://www.mansfield.ohio-state.edu/~sabedon/006pili.gif

  12. Flagella • Flagella: protein appendages for swimming through liquid or across wet surfaces. • Rotate like propellers. • Different from eukaryotic flagella. • Arrangements on cells: • polar, • Lophotrichous, • amphitrichous, • peritrichous. www.ai.mit.edu/people/ tk/ce/flagella-s.gifwww.bmb.leeds.ac.uk/.../icu8/ introduction/bacteria.html

  13. From the membrane in: the bacterial cytoplasm • Cytoplasm is a gel made of water, salts, LMW molecules, and lots of proteins. • DNA = nucleoid, w/ proteins • Plasmids = small circular DNA • Ribosomes: site of protein synthesis. Cytoplasm may also contain inclusions, gas vacuoles, extended membrane systems, or magnetosomes. But generally NO membrane-bound organelles.

  14. Inclusions and granules • Storage molecules found as small bodies within cytoplasm. • Can be organic (e.g. PHB or glycogen) or inorganic (Sulfur, polyphosphate. • PHB, a type of PHA, degradable plastic (polyester); glycogen, a polymer of glucose. • Sulfur, a metabolic by-product; polyphosphate, polymer of PO4 http://www.accessexcellence.org/WN/SUA12/marg499.html

  15. Magnetosomes “Membrane”- coated pieces of magnetite, assist bacteria in moving to microaerophilic environments. An organelle? North is down. Magnetospirillum magnetotacticum www.calpoly.edu/~rfrankel/ mtbphoto.htmlhttp://geoweb.tamu.edu/courses/geol101/lab/topo_maps/IMG00006.GIF

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