vsv4

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vsv4

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

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