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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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Ways to think about peptidoglycan

Ways to think about peptidoglycan

Bacterial cell structure continued

Bacterial Cell Structure (continued)

You are here.

Gram negative cell wall

Gram negative cell wall

Outer membrane

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

Structure of lps

Structure of LPS

extends from cell surface.

contains odd sugars e.g. KDO.

Gln-P and fatty acids

take the place of


www.med.sc.edu:85/fox/ cell_envelope.htm

Periplasmic space

Periplasmic Space

www.arches.uga.edu/~emilyd/ theory.html



  • 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.

Glycocalyx capsules and slime layers

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.



www.activatedsludge.info/ resources/visbulk.asp

Non carbohydrate layers

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

Fimbriae and pili

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

Fimbriae and pili 2

Fimbriae and pili-2




  • 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

From the membrane in the bacterial cytoplasm

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.

Inclusions and granules

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




“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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