Bacterial Polysaccharide Overviewlwang/bcmb8020/bacterial-polysaccharid… · Bacterial...
Transcript of Bacterial Polysaccharide Overviewlwang/bcmb8020/bacterial-polysaccharid… · Bacterial...
![Page 1: Bacterial Polysaccharide Overviewlwang/bcmb8020/bacterial-polysaccharid… · Bacterial Polysaccharide Function of Bacterial and Viral Polysaccharides Dr. Lianchun Wang Overview General](https://reader034.fdocuments.us/reader034/viewer/2022042622/5f7bd7f8cd26fe17c81819b8/html5/thumbnails/1.jpg)
Bacterial Polysaccharide
Function of Bacterial and Viral Polysaccharides
Dr. Lianchun Wang
Overview
General structure of bacterial cell walls
Peptidoglycan (murein)
Periplasmic !-glucans (MDO)
Lipopolysaccharide (LPS)
Capsular polysaccharides
![Page 2: Bacterial Polysaccharide Overviewlwang/bcmb8020/bacterial-polysaccharid… · Bacterial Polysaccharide Function of Bacterial and Viral Polysaccharides Dr. Lianchun Wang Overview General](https://reader034.fdocuments.us/reader034/viewer/2022042622/5f7bd7f8cd26fe17c81819b8/html5/thumbnails/2.jpg)
Crystal violet staining
1. Based on retention ofcrystal violet dye (Gramstaining)
2. The Gram stainingclassifying two distincttypes of bacteria based onstructural difference intheir cell wall (Gram+ andGram-)
3. The positive staining iscaused by a high amountof peptidoglycan in the cellwall of Gram+ bacteria.
4. Gram+ bacteria lack outermembrane, and have athicker peptidoglycan withteichoic acids
5. Many species of Gram-bacteria are pathogenic,causing disease in a hostorganism.
6. This pathogenic capabilityis usually associated withcertain component ofGram- cell wall.
Gram-positive and Gram-negative bacteria
(+ safranin counterstaining)
Staphylococcus aureus
Pseudomonas aeruginosa
LPS
MDO
PG
Capsule
Gram-negative bacteria cell wall
Structure of the cell wall of E. coli. The cell wall of gram-negative bacteria consists of several layers of variouspolysaccharides. The periplasm contains peptidoglycan, a copolymer of polysaccharide and short peptides, and a classof !-glucans known as MDOs. The outer leaflet of the outer membrane is rich in LPS. In mucoid strains, a capsularpolysaccharide covers the entire cell.
![Page 3: Bacterial Polysaccharide Overviewlwang/bcmb8020/bacterial-polysaccharid… · Bacterial Polysaccharide Function of Bacterial and Viral Polysaccharides Dr. Lianchun Wang Overview General](https://reader034.fdocuments.us/reader034/viewer/2022042622/5f7bd7f8cd26fe17c81819b8/html5/thumbnails/3.jpg)
Peptidoglycan
[GlcNAc!1,4MurNAc!1,4]n
Heijenoort (2001) Glycobiology 11:25R
1. Consists of parallel strands ofpolysaccharide composed of GlcNAcand N-acetylmuramic acid (MurNAc) in !-1,4 linkages, cross-linked by covalentlybound short peptides composed of L-Ala, unusual D-amino acids (D-Glu & D-Ala), and L-diaminopimelic acid (L-DAP).
2. 10% dry weight of cell well, representingthe major structural component ofperiplasm
3. Confers mechanical strength & Shapecell
4. Withstand internal osmotic pressure
Peptidoglycan Biosynthesis
P
Undecaprenylphosphate
![Page 4: Bacterial Polysaccharide Overviewlwang/bcmb8020/bacterial-polysaccharid… · Bacterial Polysaccharide Function of Bacterial and Viral Polysaccharides Dr. Lianchun Wang Overview General](https://reader034.fdocuments.us/reader034/viewer/2022042622/5f7bd7f8cd26fe17c81819b8/html5/thumbnails/4.jpg)
Peptidoglycan
A
GDA
AG
DA
AG
DA
AG
DA
A
G
DA
A
G
DA
AG
DA
A
GDA
A A
A
G
DA
A
GD
A
G
DA
A
GDA
A
GD
A
G
DA
A
G
DA
AGDA
AGD
A
AGD
A
AGD
A
AG
D
A
AG
D
A
AGD
A
AGDA
The final step involvescleavage between theD-Ala-D-Ala unit andtranspeptidation to theamino group of DAP ofanother unit
A AA A
Vancomycin
![Page 5: Bacterial Polysaccharide Overviewlwang/bcmb8020/bacterial-polysaccharid… · Bacterial Polysaccharide Function of Bacterial and Viral Polysaccharides Dr. Lianchun Wang Overview General](https://reader034.fdocuments.us/reader034/viewer/2022042622/5f7bd7f8cd26fe17c81819b8/html5/thumbnails/5.jpg)
MDO
Gram-negative Bacteria Cell Wall
Membrane Derived Oligosaccharides (MDO)
! Branched !-glucans
! Generally consists of 6–12glucose units, mostly in !1-2linkages with !1-6 branches
! Represent about 1-5% of dryweight
! Require UDP-Glc andundecaprenyl-PP-Glc as aprimer and carrier for MDOassembly
! Charged substituents act asan osmolyte and protects theinner membrane against thelarge difference in osmolarityinside the cell compared tooutside the cell
![Page 6: Bacterial Polysaccharide Overviewlwang/bcmb8020/bacterial-polysaccharid… · Bacterial Polysaccharide Function of Bacterial and Viral Polysaccharides Dr. Lianchun Wang Overview General](https://reader034.fdocuments.us/reader034/viewer/2022042622/5f7bd7f8cd26fe17c81819b8/html5/thumbnails/6.jpg)
LPS
Gram-negative Bacteria Cell Wall
Lipopolysaccharide (LPS)
LPS consists of three domains
– Lipid A, also known as endotoxin
– Core region composed of KDO (K), heptoses(H), and hexoses (open hexagons)
– Highly variable outer O-antigen region
![Page 7: Bacterial Polysaccharide Overviewlwang/bcmb8020/bacterial-polysaccharid… · Bacterial Polysaccharide Function of Bacterial and Viral Polysaccharides Dr. Lianchun Wang Overview General](https://reader034.fdocuments.us/reader034/viewer/2022042622/5f7bd7f8cd26fe17c81819b8/html5/thumbnails/7.jpg)
! Initiates by acylation of UDP-GlcNAc at C3,followed by N-deacetylation, and N-acylation
HOO
ONH
O H
CO
HO
OO
P
O
OO H
HO
P
O
OO H
Uridin e
HO
O
HOAcN
HO
OP
O
OO H
P
O
OO H
Uridin e
Wyckoff et al. (1998) Trends Microbiol. 6:154
Lipid A Assembly
Lipid A Assembly
HOO
ONH
OH
CO
HO
OO
P
O
OOH
HO
P
O
OOH
Uridine
HOO
ONH
OH
CO
HO
O OP
O
OOH
HO
HOO
ONH
OH
CO
HO
O
O
HO
HOO
ONH
CH2
CO
HO
O OP
O
OOH
HO
+
Diacylglucosamine-1-P condenses with anothermolecule of UDP-diacylglucosamine to form thetetraacyl disaccharide core
![Page 8: Bacterial Polysaccharide Overviewlwang/bcmb8020/bacterial-polysaccharid… · Bacterial Polysaccharide Function of Bacterial and Viral Polysaccharides Dr. Lianchun Wang Overview General](https://reader034.fdocuments.us/reader034/viewer/2022042622/5f7bd7f8cd26fe17c81819b8/html5/thumbnails/8.jpg)
Lipid A Assembly
! KDO transferases initiate theformation of the core
! Additional C12 fatty acids addedto !-hydroxy groups (wax)
! Lipid A translocates to the outerleaflet of the outer membrane bymsbA (ABC transporter)
Doerrler et al. (2001) J Biol Chem. 276:11461
Lipid A Biology
! Lipid A, the heat stable endotoxin of gram negatives
! Cause fever, septic shock, and a variety of deleteriousphysiological effects
! When released in blood circulation, LPS binds to CD14 onmonocytes and macrophages, triggers cytokine secretion
! A significant target to treat bacterium-infection resultedhuman diseases
![Page 9: Bacterial Polysaccharide Overviewlwang/bcmb8020/bacterial-polysaccharid… · Bacterial Polysaccharide Function of Bacterial and Viral Polysaccharides Dr. Lianchun Wang Overview General](https://reader034.fdocuments.us/reader034/viewer/2022042622/5f7bd7f8cd26fe17c81819b8/html5/thumbnails/9.jpg)
LPS Structural and Functional Domains
Core region contains unusual sugars
! The inner core contains 1-4 KDO residues, which looklike an analog of sialic acid
! The core also contains heptopyranoses, which can varystereochemically
! The rest of the core consists of various combinations ofGlc and Gal
OH O COOH
OH
OH
HOHC
CH2OH
3-deoxy-D-manno-octulosonic acid (KDO)
L-glycero-D-manno-heptulose
O
OH
OH
CHOH
CH2OH
OHOH
![Page 10: Bacterial Polysaccharide Overviewlwang/bcmb8020/bacterial-polysaccharid… · Bacterial Polysaccharide Function of Bacterial and Viral Polysaccharides Dr. Lianchun Wang Overview General](https://reader034.fdocuments.us/reader034/viewer/2022042622/5f7bd7f8cd26fe17c81819b8/html5/thumbnails/10.jpg)
LPS Structural and Functional Domains
O-antigens
! O-antigens consist of 2-8 sugars,repeated !50 times
! O-antigens gives rise to differentserotypes and some arecorrelated with disease
O-antigen Structure
O9 "3 "2 "2 "2 "3
O6 "3 !4 !3
!2
"4
O124 !3 !6 "3
"4
!6 GlcLA
GlcLA = glucolactillic acid
![Page 11: Bacterial Polysaccharide Overviewlwang/bcmb8020/bacterial-polysaccharid… · Bacterial Polysaccharide Function of Bacterial and Viral Polysaccharides Dr. Lianchun Wang Overview General](https://reader034.fdocuments.us/reader034/viewer/2022042622/5f7bd7f8cd26fe17c81819b8/html5/thumbnails/11.jpg)
Capsule
Gram-negative bacteria cell wall
! Mucoid strains contain a polysaccharide capsule
! >80 different capsules types are known just in E. coli
! Extraordinary diversity of structure
!4 !3 !4!4 !3
"4 !4 "4"4 !4
"8 "8 "8 "8 "8
Capsule type Structure
K1, polysialic acid
K5, N-acetylheparosan
Group A Streptococcus (hyaluronan)
![Page 12: Bacterial Polysaccharide Overviewlwang/bcmb8020/bacterial-polysaccharid… · Bacterial Polysaccharide Function of Bacterial and Viral Polysaccharides Dr. Lianchun Wang Overview General](https://reader034.fdocuments.us/reader034/viewer/2022042622/5f7bd7f8cd26fe17c81819b8/html5/thumbnails/12.jpg)
! Adhesion receptor
! Deterrent to desiccation
! Resistance to phages and to complement in vertebrate host(virulence factor)
! Escape of host immunity (molecular mimicry)
Function of Capsule
Carbohydrates of Bacterial Cell Wall
Peptidoglycan (murein)
Periplasmic !-glucans (MDO)
Lipopolysaccharide (LPS)
Capsular polysaccharides
![Page 13: Bacterial Polysaccharide Overviewlwang/bcmb8020/bacterial-polysaccharid… · Bacterial Polysaccharide Function of Bacterial and Viral Polysaccharides Dr. Lianchun Wang Overview General](https://reader034.fdocuments.us/reader034/viewer/2022042622/5f7bd7f8cd26fe17c81819b8/html5/thumbnails/13.jpg)
! Have important structural and functional roles in the life of abacterial cell
! The capsular polysaccharides and LPS represent the first lineof defense against complement and bacteriophages
! Contain the major antigenic determinants that distinguishvarious serotypes of bacteria, which are sometimes correlatedwith diseases.
! Have compound effects on mammalian host. For example,Lipid A of LPS causes various secondary complications ofinfections, such as septic shock, multiple organ failure, andmortality.
! Considerable interest exists in developing anti-bacteria agents
Function of Polysaccharides inBacterial Cell Wall