Gram Staining: Why does Moraxella catarrhalis turn pink?

Why does Moraxella catarrhalis turn pink after the decolorizer is used in a Gram stain?

What are the characteristics of Moraxella (Branhamella) catarrhalis in the Gram staining process?

Answer:

Moraxella (Branhamella) catarrhalis is a Gram-negative bacterium that turns pink after the decolorizer is used in a Gram stain.

Gram staining is a widely used technique in microbiology to differentiate between different types of bacteria based on the characteristics of their cell walls. In the case of Moraxella catarrhalis, which is a Gram-negative bacterium, it exhibits a specific behavior during the Gram staining process.

When the decolorizer is applied in the Gram stain, Moraxella catarrhalis initially becomes colorless due to its thin peptidoglycan layer in the cell wall. The decolorizer washes away the primary stain, crystal violet, revealing the colorless cells.

However, when the counterstain safranin is applied, it stains the decolorized cells a pink color. This pink coloration is characteristic of Gram-negative bacteria like Moraxella catarrhalis in the Gram staining process.

Overall, the specific behavior of Moraxella catarrhalis turning pink after the decolorizer is used in a Gram stain is due to its Gram-negative nature and the thin peptidoglycan layer in its cell wall.