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vsv4 vsv4 Presentation Transcript

  • Dr. Alvin Fox The external layers of vegetative cells and spores
  • KEY WORDS Cell envelope Teichoic acid Cell wall Teichuronic acid Cell membrane Lipoteichoic acid Outer membrane Mycolic acid Peptidoglycan Undecaprenol (bactoprenol) Braun lipoprotein Endospore (spore) Porins Cell division Lipopolysaccharide
  • Topics:
    • Structure of vegetative cell envelopes
      • unique cell envelope molecules
      • biosynthesis of cell wall constituents
    • Endospores (dormant cells)
    • Cell division
  • Cell Envelope
    • C ell membrane + cell wall (+ plus outer membrane)
    • Cell wall
      • peptidoglycan
      • attached structures .
  • Bacterial cell envelopes Gram stain (+ or -) correlates with structure
  • Gram positive Gram negative
  • Peptidoglycan
    • single macromolecule
    • highly cross-linked
    • surrounds cell
    • provides rigidity
  • Peptidoglycan
    • glycan backbone
      • muramic acid
      • glucosamine
    • peptide side chain
    • peptide cross-bridge
      • D- and L- amino acids
      • diaminopimelic acid
    • Muramic acid , D-amino acids diaminopimelic acid
    • not synthesized by mammals
  • Peptidoglycan Muramic acid Glucosamine L-alanine D-glutamic acid L-lysine/Diaminopimelic acid D-alanine D-alanine
  • Gram Positive Cell Envelope
    • Teichoic acid
      • polymer
      • ribitol phosphate or ribitol glycerol backbone
    • Teichuronic acid
      • polymer
      • no phosphorus
      • glucuronic acid
  • Teichoic and teichuronic acids
    • Metal ion uptake
    • Direct autolytic enzymes
      • holes punched in cell wall
      • allows insertion cell wall (synthesis)
  • Lipoteichoic acids
    • cell membrane
    • autolysins kept from cell wall
  • Gram Positive Cell Envelope Cytoplasm Lipoteichoic acid Peptidoglycan-teichoic acid Cytoplasmic membrane r r r r r r r r r r
    • Braun lipoprotein
      • binds cell wall to outer membrane
    Gram Negative Peptidoglycan
  • Outer Membrane
    • lipopolysaccharide
    • phospholipids
    • Proteins
      • porins
  • Lipopolysaccharide
    • Lipid A
    • Glucosamine disaccharide
    • Beta hydroxy fatty acids
    • Core
    • Heptoses
    • Ketodeoxyoctonic acid
    O-antigen Highly variable n
  • Gram Negative Cell Envelope Cytoplasm Inner (cytoplasmic) membrane Outer Membrane Lipopolysaccharide Porin Braun lipoprotein Peptidoglycan
  • Acid Fast Cell Envelope Cytoplasm Peptidoglycan-mycolic acid-arabinogalactan Cytoplasmic membrane Mycolic acid lipids r r r r r r r r r r
  • Peptidoglycan synthesis Cytoplasm Cell wall undecaprenol sugar amino acid Cell Membrane 1 2 3
  • Lipopolysaccharide
    • synthesis similar to peptidoglycan
    • also on undecaprenol carrier
  • Spore
    • Modified Gram positive bacteria cell
      • unusual cell envelope
        • cell membrane
        • outer membrane
  • Spore
    • Peptidoglycan layer
      • cortex
      • between two membranes
      • less cross-linked
      • dehydrated muramic acid (lactam)
  • Vegetative cell division Sporulation
  • The endospore cortex exosporium coat Inner membrane outer membrane