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Dr. Alvin Fox

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Cell membrane cell wall ( plus outer membrane) Cell wall ... Sporulation. 25. cortex. The endospore. exosporium. coat. Inner. membrane. outer. membrane ... – PowerPoint PPT presentation

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Title: Dr. Alvin Fox


1
The external layers of vegetative cells and
spores
Dr. Alvin Fox
2
KEY WORDS
Cell envelope Teichoic acid Cell
wall Teichuronic acid Cell membrane Lipoteic
hoic acid Outer membrane Mycolic
acid Peptidoglycan Undecaprenol
(bactoprenol) Braun lipoprotein Endospore
(spore) Porins Cell
division Lipopolysaccharide
3
Topics
  • Structure of vegetative cell envelopes
  • unique cell envelope molecules
  • biosynthesis of cell wall constituents
  • Endospores (dormant cells)
  • Cell division

4
Cell Envelope
  • Cell membrane cell wall ( plus outer
    membrane)
  • Cell wall
  • peptidoglycan
  • attached structures.

5
Bacterial cell envelopes
Gram stain ( or -) correlates with structure
6
Gram positive
Gram negative
7
Peptidoglycan
  • single macromolecule
  • highly cross-linked
  • surrounds cell
  • provides rigidity

8
Peptidoglycan
  • glycan backbone
  • muramic acid
  • glucosamine
  • peptide side chain
  • peptide cross-bridge
  • D- and L- amino acids
  • diaminopimelic acid

9
  • Muramic acid, D-amino acids diaminopimelic acid
  • not synthesized by mammals

10
Peptidoglycan
L-alanine D-glutamic acid L-lysine/Diaminopimelic
acid D-alanine D-alanine
Muramic acid
Glucosamine
11
Gram Positive Cell Envelope
  • Teichoic acid
  • polymer
  • ribitol phosphate or ribitol glycerol backbone
  • Teichuronic acid
  • polymer
  • no phosphorus
  • glucuronic acid


12
Teichoic and teichuronic acids
  • Metal ion uptake
  • Direct autolytic enzymes
  • holes punched in cell wall
  • allows insertion cell wall (synthesis)

13
Lipoteichoic acids
  • cell membrane
  • autolysins kept from cell wall

14
Gram Positive Cell Envelope
Lipoteichoic acid
Peptidoglycan-teichoic acid
Cytoplasmic membrane
Cytoplasm
15
Gram Negative Peptidoglycan
  • Braun lipoprotein
  • binds cell wall to outer membrane


16
Outer Membrane
  • lipopolysaccharide
  • phospholipids
  • Proteins
  • porins

17
Lipopolysaccharide
O-antigen Highly variable
n
  • Core
  • Heptoses
  • Ketodeoxyoctonic acid
  • Lipid A
  • Glucosamine disaccharide
  • Beta hydroxy fatty acids

18
Gram Negative Cell Envelope
Lipopolysaccharide
Porin
Outer Membrane
Braun lipoprotein
Peptidoglycan
Cytoplasm
Inner (cytoplasmic) membrane
19
Acid Fast Cell Envelope
Mycolic acid lipids
Peptidoglycan-mycolic acid-arabinogalactan
Cytoplasmic membrane
Cytoplasm
20
Peptidoglycan synthesis
1
2
3
Cell Membrane
Cytoplasm
Cell wall
undecaprenol
sugar
amino acid
21
Lipopolysaccharide
  • synthesis similar to peptidoglycan
  • also on undecaprenol carrier

22
Spore
  • Modified Gram positive bacteria cell
  • unusual cell envelope
  • cell membrane
  • outer membrane

23
Spore
  • Peptidoglycan layer
  • cortex
  • between two membranes
  • less cross-linked
  • dehydrated muramic acid (lactam)

24
Vegetative cell division
Sporulation
25
The endospore
exosporium
coat
outer membrane
Inner membrane
cortex
26
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