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Unformatted text preview: Counterstain is the step that could be omitted. Counterstain: is a stain with color contrasting to the principal stain, making the stained structure more easily visible. 2. Why isnt the Gram stain used on acid-fast bacteria? Acid fast bacteria are not classified as either Gram-positive or Gram-negative because they do not have the chemical characteristics of either, although the bacteria do contain peptidoglycan (murein) in their cell wall. Mycobacterium species, along with members of a related genus Nocardia, are classified as acid-fast bacteria due to their impermeability by certain dyes and stains (thus explaining why the gram stain isn't useful)....
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- Spring '09