Ways to think about peptidoglycan
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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

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)

      • 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

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

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

“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

  • 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

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



  • 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

  • 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

  • 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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