Download - Parsek lecture #3
Microm 410 Fall 2009: ProkaryoticStructure/Function: Part 2/3Dr. Matt Parsek
PeptidoglycanSynthesis
Fig.6.7a
UDP-NAG
cytoplasm cell membrane cell wall
Bactoprenol-PUDP-NAM
pentapeptide
NAM-NAG
pentapeptide
Bactoprenol
PP
UMP
UMP
NAM
pentapeptide
Bactoprenol
PP
Pi
G
M
G
M
M
G
G
G
M
M
G
Interbridgepeptide
PeptidoglycanSynthesis
Bactoprenol-P-P
NAM‐NAG
Cross-linking of Peptidoglycan Strands
autolysins
Fig. 6.7b
Transpeptidase (FtsI)
UDP-NAG
cytoplasm cell membrane cell wall
Bactoprenol-PUDP-NAM
pentapeptide
pentapeptide
NAM-NAG
Bactoprenol
PP
UMP
UMP
NAM
pentapeptide
Bactoprenol
PP
Pi
G
M
G
M
M
G
G
G
M
M
G
Interbridgepeptide
PeptidoglycanSynthesis
Bactoprenol-P-P
NAM‐NAG
D-cycloserine(Oxamycin)
Bacitracin
Vancomycin
pentapeptide
Microm 410 Fall 2009: ProkaryoticStructure/Function: Part 2/3Dr. Matt Parsek
Cross-linking of Peptidoglycan Strands
autolysins
Fig. 6.5
β-lactams
penicillins and cephalosporins
lysozyme
transpeptidase
Antibiotic Resistance
• Inactivate antibiotic β-lactamase (penicillinase)
Augmentin and Trimentin (combination of clavulanic acid andamoxicillin or ampicillin respectively)
• Change chemistry of target site
• Limit access of the antibiotic to target site
Clavulanic acid
CellShapeDetermination
•ModificationsmadetoPeptidoglycan:
•Protein(s)mayplayamajorrole
‐MreBprotein
‐MreB has homology to actin, a component of thecytoskeleton of eukaryotes.
‐lysozyme: Protoplasts/spheroplasts
‐autolysins
‐endopeptidase Heliobacterpylori
Bacillussubtilis
Caulobactercrescentus
Shapedeterminingprotein‐crescentin
Fig.6.4
Microm 410 Fall 2009: ProkaryoticStructure/Function: Part 2/3Dr. Matt Parsek
similar predicted structures of crescentin andintermediate filaments
intermediate filaments in the bacteriaCaulobacter crescentus
Cell Wall Gram-positive Bacteria
Fig. 4.20
glycerol
StructuresofdifferentTeichoicacidsCell Wall Gram-negative Bacteria
Fig.4.23
Microm 410 Fall 2009: ProkaryoticStructure/Function: Part 2/3Dr. Matt Parsek
Structure Lipopolysaccharide
Fig. 4.22
Salmonella typhimurium- ~1000 serotypes
Heptose2-keto-3-deoxyoctonic acid
MajorantigenicdetermineofGram‐negativebacteria
endotoxin Receptorssitesforcertainphage
Outer Cell Wall Proteins
• lipoproteins (Braun lipoprotein)
• porins- classical porins (non-specific channels)
OmpC- 1.1nm
OmpF- 1.2 nm
- “specific” porins
- “active transport” porin systems
Uptake of iron chelates, Vit B12, disacharides, andphosphorylated cpds
• OmpA (porin?): is essential to conjugation
LamB- maltose and maltodextrinsTsx- uptake of nucleosides
Fig.4.25
Archaealcellwalls PolysaccharidecellwallsofsomeArchaea
Microm 410 Fall 2009: ProkaryoticStructure/Function: Part 2/3Dr. Matt Parsek
S‐layersaspartofthecellwall
Fig. 4.28
Capsule and Slime Layer
Streptococcus pneumoniae
Negative stain with Indiaink
Chemistry of Capsule/Slime Layer
• Polysaccharide in composition
• Glycoprotein in composition
• Protein in composition
Homopolymer of glutamic acid
Bacillus anthracis and Bacillus megaterium
Acetobacter xylinum- cellulose capsule (β-1, 4 linkage)
Agrobacterium tumefaciens- glycan capsule (β-1, 2 linkage)
Crown Gall Tumors
D-isomer
• Identifying type of capsule being made:
- chemical analysis
- serotyping Antibodies or immunoglobulinsAntigen or an antigenic determinant or epitope
E. coli- 50 different serotypes
Glycocalyx layerDextran
• Synthesized from sucrose by S. mutans;involved in plaque formation
• Polymer can also be used for:– Antithrombotic agent in microsurgery– Osmotic agents for treatment of hypovolemia– Lubricant in eye drops– Size-exclusion chromatography matrix (Sephadex)
Microm 410 Fall 2009: ProkaryoticStructure/Function: Part 2/3Dr. Matt Parsek
Slime layer of carbohydrate produced by Streptococcus mutans
Dextran
Role/Function of Capsule/Slime Layer
• Attachment or adherence
Streptococcus mutans
• Protection
- desiccation
- avoiding phagocytosis
sucrose
Dental plaquebiofilm
(109 Bacteria/gram; and over 500 differentspecies identified)
In the laboratory capsule production can be deemed to be non‑essential.
Some bacteria owe theirpathogenecity to thisstructure.
Capsule/slime Layer Contributes toPathogenesis
• Streptococcus pyogenes- acute bacterial pharyngitis (sore throat)
• Streptococcus pneumoniae- pneumonia
• Yersinia pestis- plague
• Bacillus anthracis- anthrax
• Neisseria meningitidis- meningitis