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Functions of bacterial cell parts

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Functions of bacterial cell parts Powered By Docstoc
					   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
• Cytoplasmic (=inner membrane, plasma
  membrane), CM
• Outer membrane, OM
• Periplasm
• Cell wall
• Capsule
     3. Bacterial appendages
• Pilus, pili
• Flagellum, flagella
 4. Disruption of bacterial cells
• Boiling in SDS
• Sonic oscillation
• French pressure cell
              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
            1. Protoplasm
• Nucleoid: Molecular composition
  – Circular 2 x double stranded DNA helix
  – 4.7 x 106 bp
  – Supercoiled
  – Proteins: packing DNA
  – Proteins: remove supercoils
           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
             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
            1. Protoplasm
• Cytosol: Function and properties
  – enclosed by CM
  – 1000s of proteins: metabolism
  – [protein] ~ 20%
  – Gel
             1. Protoplasm
• Cytosol: Molecular composition
  – 80% dry weight = protein
  – 60 tRNA molecules
  – mRNA
  – Metabolites
  – Vitamins, cofactors, ATP, inorganic ions
  – H2O
            1. Protoplasm
• Storage granules: Function and properties
  – Deposits
  – Short-term energy source


• Storage granules: Molecular composition
  – Polysaccharides: glycogen
  – Degradation  free sugars
   2. Bacterial cell envelopes
• CM: Function and properties
  – Selectively permeable boundary
  – Passage of H2O, nutrients, ions
  – Transport systems
  – Nutrient E  ATP
   2. Bacterial cell envelopes
• CM: Molecular composition
  – Bilayer of 7 different phospholipids
  – 100s of proteins: > 2 x 105 / CM
  – 30% lipid; 70% protein
   2. Bacterial cell envelopes
• OM: Function and properties
  – Molecular sieve
  – Protection vs chemicals
  – Specific transport proteins:
     • Scavenge rare nutrients
   2. Bacterial cell envelopes
• OM: Molecular composition
  – Asymmetric bilayer:
     • Inner leaflet: phospholipids
     • Outer leaflet: lipopolysaccharide
  – 50 proteins: 106 molecules / cell
   2. Bacterial cell envelopes
• Periplasm: Function and properties
  – Between OM and CM
  – Aqueous gel
  – Proteins: nutrition, detoxification
   2. Bacterial cell envelopes
• Periplasm: Molecular composition
  – Peptidoglycan = murein: rigidity
    • Several layers
    • Sacculus
  – Gram - = thin; Gram + = thick
  – Binding proteins: nutrients
  – Degradative enzymes
   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
     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
     3. Bacterial appendages
• Pilus, -i : Molecular composition
  – Pilin = single species protein
  – Minor protein at tip = adhesin
  – Carbohydrate binding
  – Attachment
     3. Bacterial appendages
• Flagellum, -a: Function and properties
  – Cell swimming
  – Basal body complex: M, S, P, L rings
  – Central rod
  – Hook
  – Filament
     3. Bacterial appendages
• Flagellum, -a: Molecular composition
  – Flagellin
  – Hook protein
  – Basal body complex: 10s of protein


• Rotary motor
 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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posted:10/3/2011
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