1. Bacterial Cell Structure (continued)
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2. Gram negative cell wall

3. 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

4. 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

5. Periplasmic Space
theory.html

6. Periplasm
The periplasm is the “stuff” in that space, present in Gram + bacteria also.
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

7. 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.
S-layers are highly structured protein layers that function like
capsules
cell
capsule
resources/visbulk.asp

8. 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

9. Fimbriae and pili-2

10. 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

11. Flagellar structures www.scu.edu/SCU/Departments/ BIOL/Flagella.jpg
img.sparknotes.com/.../monera/ gifs/flagella.gif

12. Runs and Tumbles: bacteria find their way

13. Motility revisited
Flagella: protein appendages for swimming through liquid or across wet surfaces.
Axial filament: a bundle of internal flagella
Between cell membrane and outer membrane in spirochetes
Filament rotates, bacterium corkscrews through medium
Gliding
No visible structures, requires solid surface
Slime usually involved.

14. Axial filaments

15. Gliding Motility Movement on a solid surface.
No visible organelles of locomotion.
Cells produce, move in slime trails.
Unrelated organism glide:
myxobacteria, flavobacteria,
cyanobacteria; appear to glide by
different mechanisms.
Cells glide in groups, singly, and
can reverse directions.

16. 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.

17. 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

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