4.4 - Gram pos and Gram neg cell walls

gram pos cell wall

• thicker and peptidoglycan up to 90%; helps retain crystal violet dye; no outer membrane

• contains glycopolymers aka teichoic acid

• very permeable due to peptidoglycan being porous (not the same as porin proteins)

gram neg cell wall

• more complex and high components; contain peptidoglycans (up to 10%)

• lack teichoic acid but has outer membrane and periplasm (space between inner and outer membrane)

  • inner half of membrane is lipid bilayer; outer half of membrane is lipopolysaccharide

• peptidoglycan linked to membrane using lipoprotein

atypical cell walls

• mollicutes lack a cell wall; bacteria are very small (0.2-0.3 micrometer)

  • cell wall lost due to parasitic relationship w/ host

• acid-fast bacteria

  • has property that gives bacteria the ability to resist decolorization by acids during staining procedure

  • easy to classify and detect

  • mycobacterium and nocardia

  • contains waxy-lipid called mycolic acid

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