Ways to think about peptidoglycan

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Ways to think about peptidoglycan
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Bacterial Cell Structure (continued)
You are here.
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Gram negative cell wall
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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

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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.edu85/fox/ cell_envelope.htm
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Periplasmic Space
www.arches.uga.edu/emilyd/ theory.html
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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.

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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
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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?L1
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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
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Fimbriae and pili-2
http//www.mansfield.ohio-state.edu/sabedon/006pi
li.gif
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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.gif
www.bmb.leeds.ac.uk/.../icu8/ introduction/bacteri
a.html
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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.
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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.h
tml
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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//ge
oweb.tamu.edu/courses/geol101/lab/topo_maps/IMG000
06.GIF