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.
cell_envelope.htm

6. Periplasmic Space
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
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

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”).
oralenv/images/sex1.jpg

11. Fimbriae and pili-2

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.
tk/ce/flagella-s.gif 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

15. Magnetosomes
“Membrane”- coated pieces of magnetite, assist bacteria in moving to microaerophilic environments. An organelle?
North is down.
Magnetospirillum magnetotacticum
mtbphoto.html