The envelope of mycobacteria

Annu Rev Biochem. 1995;64:29-63. doi: 10.1146/annurev.bi.64.070195.000333.

Abstract

Mycobacteria, members of which cause tuberculosis and leprosy, produce cell walls of unusually low permeability, which contribute to their resistance to therapeutic agents. Their cell walls contain large amounts of C60-C90 fatty acids, mycolic acids, that are covalently linked to arabinogalactan. Recent studies clarified the unusual structures of arabinogalactan as well as of extractable cell wall lipids, such as trehalose-based lipooligosaccharides, phenolic glycolipids, and glycopeptidolipids. Most of the hydrocarbon chains of these lipids assemble to produce an asymmetric bilayer of exceptional thickness. Structural considerations suggest that the fluidity is exceptionally low in the innermost part of bilayer, gradually increasing toward the outer surface. Differences in mycolic acid structure may affect the fluidity and permeability of the bilayer, and may explain the different sensitivity levels of various mycobacterial species to lipophilic inhibitors. Hydrophilic nutrients and inhibitors, in contrast, traverse the cell wall presumably through channels of recently discovered porins.

Publication types

  • Research Support, U.S. Gov't, P.H.S.
  • Review

MeSH terms

  • Carbohydrate Sequence
  • Cell Membrane Permeability
  • Cell Wall / chemistry
  • Cell Wall / metabolism
  • Cell Wall / ultrastructure
  • Glycolipids / chemistry
  • Humans
  • Lipopolysaccharides / chemistry
  • Membrane Lipids / chemistry
  • Membrane Lipids / metabolism
  • Membrane Proteins / chemistry
  • Molecular Sequence Data
  • Mycobacterium / chemistry*
  • Mycobacterium / metabolism
  • Mycobacterium / pathogenicity
  • Mycolic Acids / chemistry
  • Peptidoglycan / chemistry
  • Polysaccharides, Bacterial / chemistry

Substances

  • Glycolipids
  • Lipopolysaccharides
  • Membrane Lipids
  • Membrane Proteins
  • Mycolic Acids
  • Peptidoglycan
  • Polysaccharides, Bacterial
  • lipoarabinomannan