Title: Dr. Alvin Fox
1The external layers of vegetative cells and
spores
Dr. Alvin Fox
2KEY 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
3Topics
- Structure of vegetative cell envelopes
- unique cell envelope molecules
- biosynthesis of cell wall constituents
- Endospores (dormant cells)
- Cell division
4Cell Envelope
- Cell membrane cell wall ( plus outer
membrane) - Cell wall
- peptidoglycan
- attached structures.
5Bacterial cell envelopes
Gram stain ( or -) correlates with structure
6Gram positive
Gram negative
7Peptidoglycan
- single macromolecule
- highly cross-linked
- surrounds cell
- provides rigidity
8Peptidoglycan
- 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
10Peptidoglycan
L-alanine D-glutamic acid L-lysine/Diaminopimelic
acid D-alanine D-alanine
Muramic acid
Glucosamine
11Gram Positive Cell Envelope
- Teichoic acid
- polymer
- ribitol phosphate or ribitol glycerol backbone
-
- Teichuronic acid
- polymer
- no phosphorus
- glucuronic acid
12Teichoic and teichuronic acids
- Metal ion uptake
- Direct autolytic enzymes
- holes punched in cell wall
- allows insertion cell wall (synthesis)
13Lipoteichoic acids
- cell membrane
- autolysins kept from cell wall
14Gram Positive Cell Envelope
Lipoteichoic acid
Peptidoglycan-teichoic acid
Cytoplasmic membrane
Cytoplasm
15Gram Negative Peptidoglycan
- Braun lipoprotein
- binds cell wall to outer membrane
16Outer Membrane
- lipopolysaccharide
- phospholipids
- Proteins
- porins
17Lipopolysaccharide
O-antigen Highly variable
n
- Core
- Heptoses
- Ketodeoxyoctonic acid
- Lipid A
- Glucosamine disaccharide
- Beta hydroxy fatty acids
18Gram Negative Cell Envelope
Lipopolysaccharide
Porin
Outer Membrane
Braun lipoprotein
Peptidoglycan
Cytoplasm
Inner (cytoplasmic) membrane
19Acid Fast Cell Envelope
Mycolic acid lipids
Peptidoglycan-mycolic acid-arabinogalactan
Cytoplasmic membrane
Cytoplasm
20Peptidoglycan synthesis
1
2
3
Cell Membrane
Cytoplasm
Cell wall
undecaprenol
sugar
amino acid
21Lipopolysaccharide
- synthesis similar to peptidoglycan
- also on undecaprenol carrier
22Spore
- Modified Gram positive bacteria cell
- unusual cell envelope
- cell membrane
- outer membrane
23Spore
- Peptidoglycan layer
- cortex
- between two membranes
- less cross-linked
- dehydrated muramic acid (lactam)
24Vegetative cell division
Sporulation
25The endospore
exosporium
coat
outer membrane
Inner membrane
cortex
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