Morphology
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Mycobacteria are slender rods of varying lengths that sometimes show branching filamentous form resembling ‘fungal mycelium’.
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Hence, the name mycobacteria, meaning fungus like bacteria.
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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.
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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.
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They are usually straight or slightly curved rod occurring singly, pairs or in small groups. The morphology varies from cells of species to species.
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Mycobacterium tuberculosis is often arranged in serpentine cords.
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Mycobacterium kansasi is distinct banded or beaded appearnce, while
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Mycobacterium avium is often almost coccoid.
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In clinical materials they may appear as bundle of faggots. They are non-motile, non-sporing and non-capsulated.
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Last modified: Monday, 4 June 2012, 5:00 AM