Faculty: Dr' Alvin Fox

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CELL ENVELOPE, SPORES AND MACROMOLECULAR
BIOSYNTHESIS
Faculty Dr. Alvin Fox
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KEY WORDS
Cell envelope Lipopolysaccharide
(endotoxin) Cell wall Teichoic acid Cell
membrane Teichuronic acid Outer membrane
Lipoteichoic acid Peptidoglycan
Mycolic acid Braun lipoprotein Undecaprenol
(bactoprenol) Porins
Endospore
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Topics for discussion

• Structure of cell envelopes.
• Unique cell envelope macromolecules
• their biosynthesis
• Endospores

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Cell Envelope

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

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Bacterial cell envelopes
Gram stain ( or -) correlates with structure
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Gram positive
Gram negative
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Peptidoglycan

• single macromolecule
• highly cross-linked
• surrounds cell
• provides rigidity

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Peptidoglycan

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

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

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Peptidoglycan
L-alanine D-glutamic acid L-lysine/Diaminopimelic
acid D-alanine D-alanine
Muramic acid
Glucosamine
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Gram Positive Cell Envelope

• Teichoic acid
• polymer
• phosphorus
• ribitol or glycerol backbone
• Teichuronic acid
• polymer
• no phosphorus
• glucuronic acid backbone

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Teichoic and teichuronic acids

• Metal ion uptake
• Direct autolytic enzymes
• cell wall digestion
• cell wall synthesis

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Gram Positive Cell Envelope
Lipoteichoic acid
Peptidoglycan-teichoic acid
Cytoplasmic membrane
Cytoplasm
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Gram Negative Peptidoglycan

• Braun lipoprotein
• binds cell wall to outer membrane

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Outer Membrane

• lipopolysaccharide
• phospholipids
• Proteins
• porins

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Lipopolysaccharide
O-antigen Highly variable
n

• Core
• Heptoses
• Ketodeoxyoctonic acid

• Lipid A
• Glucosamine disaccharide
• Beta hydroxy fatty acids

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Gram Negative Cell Envelope
Lipopolysaccharide
Porin
Outer Membrane
Braun lipoprotein
Peptidoglycan
Cytoplasm
Inner (cytoplasmic) membrane
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Acid fast and related (mycobacteria, nocardia and
corynebacteria)

• peptidoglycan
• mycolic acid-polysaccharide
• Outer membrane
• complex lipids (mycolic acid)

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Peptidoglycan synthesis
Cell Membrane
Cytoplasm
Cell wall
undecaprenol
sugar
amino acid
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Lipopolysaccharide

• synthesis similar to peptidoglycan
• also on undecaprenol carrier

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Spore

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

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Spore

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

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The endospore
exosporium
coat
outer membrane
Inner membrane
cortex
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