1. Structure and Function of Prokaryotes Structures External to the Cell Wall Cell Walls Biochemistry (Gram +/-)

2. Prokaryote “Anatomy” Overview Cell envelope: Collectively all the structures outside from the plasma membrane.

3. Cell Wall & Osmotic Pressure Solutes diffuse from high to low concentration. Net movement of water is toward higher solute concentrations. Cells have semi-permeable membranes (water passes; solutes don’t). Intracellular and external environment strive for isosmotic equilibrium. Osmotic pressure, refers to that required to hold back the net movement of water. Hypotonic environments promote “osmolysis”; unless there’s a rigid cell wall. Hypertonic environments promote “plasmolysis”

4. Two Cell Wall Designs:

5. Gram Stain Differential staining to distinguish cell wall types. (Christian Gram 1884)

6. Cell Wall Biochemistry What is peptidoglycan? Gram - Gram +

7. Cell Wall Biochemistry What is peptidoglycan? (Inter-) (gly)

8. Cell Wall (Gram +)

9. Cell Wall (Gram -) (w/ Outer Membrane) Periplasmic space Braun’s lipoprotein (LPS = endotoxin) core

10. Glycocalyx: means sugar coating; often polysaccharide or polypeptide layer external to the cell wall. Capsules: organized, consolidated, well attached. Slime Layer: unorganized; loose; removed easily. Function in attachment; protection; virulence. Structures External to the Cell Wall S-layer: extremely well organized layer of protein subunits that forms a rigid mesh, or mail, next to cell wall. Functions in protection and in resisting hypoosmotic stress

11. Structures External to the Cell Wall peritrichous monotrichous amphitrichous lophotrichous Flagella: Mostly made of flagellin. Filament thick (20 nm) & long (10-20 µm). Filament possibly sheathed. Varied locations on cell: Fimbriae: 1000’s of thin (~5 nm) & short appendages of helical proteins. Attachment to (specific) surfaces. Sex Pili: 1-10 slightly larger than fimbriae. Only in cells with a fertility plasmid (F factor), called donors. Attaches to like cells without F factor, called recipients. Facilitates genetic transfer between cells; with recipient gaining the F factor and possibly other genes.

12. Flagellar Motility & Chemotaxis Other kinds of motility: SpirocheteSpirochete; axial flagella Gliding motilityGliding motility; no flagella

13. Random (searching) Positive Chemotaxis (“follow that smell”) Low [nutrient solute]High [nutrient solute]