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What Colour is Gram-negative Cocci?

Published in Microbiology 1 min read

Gram-negative cocci do not have a specific color. The color observed under a microscope depends on the staining technique used.

Gram Staining:

Gram staining is a technique used to differentiate bacteria based on their cell wall structure. It involves a series of steps:

  1. Crystal violet stain: This stains all bacteria purple.
  2. Iodine solution: This acts as a mordant, fixing the crystal violet stain in the cell wall.
  3. Decolorizing agent: This removes the crystal violet stain from bacteria with thinner cell walls.
  4. Counterstain: This stains the decolorized bacteria pink or red.

Gram-negative Cocci and Staining:

Gram-negative cocci have thinner cell walls than gram-positive bacteria. This means they lose the crystal violet stain during the decolorization step and are subsequently stained pink or red by the counterstain.

Examples of Gram-negative Cocci:

  • Neisseria gonorrhoeae: The bacteria responsible for gonorrhea.
  • Moraxella catarrhalis: Often found in the respiratory tract.
  • Acinetobacter baumannii: A common cause of hospital-acquired infections.

Therefore, gram-negative cocci appear pink or red under a microscope after gram staining.

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