Morphology

MORPHOLOGY

  • Mycobacteria are slender rods of varying lengths that sometimes show branching filamentous form resembling ‘fungal mycelium’.
  • Hence, the name mycobacteria, meaning fungus like bacteria.
  • Although cytochemically Gram positive, the Mycobacteria do not take up the dyes of the Gram stain because the cell walls are rich in lipids – Mycolic acid.
  • Once a dye has been taken up by the cells they are not easily decolourised, even by acid-alcohol. Mycobacteria are therefore called as acid-fast bacilli.
  • They are usually straight or slightly curved rod occurring singly, pairs or in small groups. The morphology varies from cells of species to species.
  • Mycobacterium tuberculosis is often arranged in serpentine cords.
  • Mycobacterium kansasi is distinct banded or beaded appearnce, while
  • Mycobacterium avium is often almost coccoid.
  • In clinical materials they may appear as bundle of faggots. They are non-motile, non-sporing and non-capsulated.
Last modified: Monday, 4 June 2012, 5:00 AM