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TA: Will Spencer

TA: Will Spencer . Email: william.j.spencer@mail.mcgill.ca. Functions of bacterial cell parts. Lengeler et al. pp. 20-46 Cellular and subcellular organization of procaryotes. 1. Protoplasm. Nucleoid Ribosomes / polysomes Cytosol Storage granules. 2. Bacterial cell envelopes.

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TA: Will Spencer

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  1. TA: Will Spencer Email: william.j.spencer@mail.mcgill.ca

  2. Functions of bacterial cell parts Lengeler et al. pp. 20-46 Cellular and subcellular organization of procaryotes

  3. 1. Protoplasm • Nucleoid • Ribosomes / polysomes • Cytosol • Storage granules

  4. 2. Bacterial cell envelopes • Cytoplasmic (=inner membrane, plasma membrane), CM • Outer membrane, OM • Periplasm • Cell wall • Capsule

  5. 3. Bacterial appendages • Pilus, pili • Flagellum, flagella

  6. 4. Disruption of bacterial cells • Boiling in SDS • Sonic oscillation • French pressure cell

  7. 1. Protoplasm • Nucleoid: Function, Properties • Compact lobular body: skein • Loops, coils DNA • Genome • Center of cell; CM attached • 1 copy / cell; > 1 copy / cell; rapidly growing

  8. 1. Protoplasm • Nucleoid: Molecular composition • Circular 2 x double stranded DNA helix • 4.7 x 106 bp • Supercoiled • Proteins: packing DNA • Proteins: remove supercoils

  9. 1. Protoplasm • Ribosomes: Function, Properties • Sites of protein synthesis • mRNA  translation to protein • E. coli: 18,000 ribs / cell • Polysomes = > 1 ribosome on same mRNA

  10. 1. Protoplasm • Ribosomes: Molecular composition • rRNA = 62% • Proteins = 38% • Large subunit = 50 S • 2 rRNAs + 32 proteins • Small subunit = 30 S • 1 rRNA + 21 proteins

  11. 1. Protoplasm • Cytosol: Function and properties • enclosed by CM • 1000s of proteins: metabolism • [protein] ~ 20% • Gel

  12. 1. Protoplasm • Cytosol: Molecular composition • 80% dry weight = protein • 60 tRNA molecules • mRNA • Metabolites • Vitamins, cofactors, ATP, inorganic ions • H2O

  13. 1. Protoplasm • Storage granules: Function and properties • Deposits • Short-term energy source • Storage granules: Molecular composition • Polysaccharides: glycogen • Degradation  free sugars

  14. 2. Bacterial cell envelopes • CM: Function and properties • Selectively permeable boundary • Passage of H2O, nutrients, ions • Transport systems • Nutrient E  ATP

  15. 2. Bacterial cell envelopes • CM: Molecular composition • Bilayer of 7 different phospholipids • 100s of proteins: > 2 x 105 / CM • 30% lipid; 70% protein

  16. 2. Bacterial cell envelopes • OM: Function and properties • Molecular sieve • Protection vs chemicals • Specific transport proteins: • Scavenge rare nutrients

  17. 2. Bacterial cell envelopes • OM: Molecular composition • Asymmetric bilayer: • Inner leaflet: phospholipids • Outer leaflet: lipopolysaccharide • 50 proteins: 106 molecules / cell

  18. 2. Bacterial cell envelopes • Periplasm: Function and properties • Between OM and CM • Aqueous gel • Proteins: nutrition, detoxification

  19. 2. Bacterial cell envelopes • Periplasm: Molecular composition • Peptidoglycan = murein: rigidity • Several layers • Sacculus • Gram - = thin; Gram + = thick • Binding proteins: nutrients • Degradative enzymes

  20. 2. Bacterial cell envelopes • Capsule: Function and Properties • Defense against host cell’s phagocytes • Colonization of environments • Growth conditions • Capsule: Molecular composition • High mol weight complex polysaccharides • Amorphous slime

  21. 3. Bacterial appendages • Pilus, -i : Function and properties • Type 1 pili; 100-200 / cell • Attaching to surfaces • F1 pili = sex pilus; 1 – 3 / cell • Conjugation • Conduit for transfer of DNA to recipient

  22. 3. Bacterial appendages • Pilus, -i : Molecular composition • Pilin = single species protein • Minor protein at tip = adhesin • Carbohydrate binding • Attachment

  23. 3. Bacterial appendages • Flagellum, -a: Function and properties • Cell swimming • Basal body complex: M, S, P, L rings • Central rod • Hook • Filament

  24. 3. Bacterial appendages • Flagellum, -a: Molecular composition • Flagellin • Hook protein • Basal body complex: 10s of protein • Rotary motor

  25. 4. Disruption of bacterial cells • Boiling in 2% SDS • Cell lysate: all contents dissolved • Proteins: SDS-PAGE • Sonic oscillation • Pop bacteria • French pressure cell • 16,000 psi

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