Eubacteria, Archea, Yeast Cell Walls

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Eubacteria, Archea, YeastCell Walls
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Question

• Plants, bacteria, and yeast all have cell walls
  that provide resistance to osmotic
  pressure. Compare the composition and
  architecture of these barriers.

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Schaffer et al (2001) Proteomics 1248
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Peptidoglycan
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Gram-positive Teichoic Acids
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LPS - Lipid A
Compare the structure of LPS to glycerolipids and
gangliosides.
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O-antigens

• O-antigens consist of 2-8 sugars, repeated 50
  times
• O-antigens gives rise to different serotypes and
  some are correlated with disease

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Capsule type
Structure
K1, polysialic acid
K5, N-acetylheparosan
Group A Streptococcus (hyaluronan)

• Mucoid strains contain a polysaccharide capsule
• 80 different capsules types are known just in E.
  coli
• Extraordinary diversity of structure

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Yeast Cell Wall
The cell wall is made of 60 b-glucans, 40
mannoproteins, and 1 chitin
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Compare and contrast the pathways of glycoprotein
N-glycosylation in Archaea ,yeast and mammals.
What is the functional significance of the
differences?
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Fig. 21.5
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N-linked glycans Isoprenoid donors Acidic
glycans Crosslinking
Burda Aebi (1999) Biochim Biophys Acta 1426239
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Summary

• Bacterial cell walls are complex layered
  structures composed of multiple classes of
  glycans
• Bacterial wall glycans provide an exoskeleton,
  define shape, protect against turgor pressure,
  create antigenic serotypes, and provide a way to
  prevent immune recognition
• Glycosylated proteins are present in eubacteria
  and in archaea
• Yeast produce many of the same glycans found in
  higher eukaryotes, but the mecahnism of assembly
  differs in subtle way
• Yeast cell walls are composed of glucans,
  mannans, chitin)
• Yeast and bacteria provide powerful genetic
  systems for understanding membrane and cell wall
  assembly

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Questions

• 1. The relationship of commensal bacteria in the
  gut is sometimes described as symbiotic.
  Describe the system that exists between
  Bacteroides and the mouse host and and how its
  mutually beneficial.

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Ileum and fucose
UEA1 P28 Ileum
OPA ?1-6
UEA1 ?1-2
UEA1 P25 Germ-free
UEA1 P25 Conventional
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Induced Fucosylation
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Fucose Operon
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Fu-4 Mutant Cant Metabolize Fucose
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