Which statement about Pseudomonads is true regarding Gram staining?

Which statement about Pseudomonads is true regarding Gram staining?

• A. They stain weakly with safranin
• B. They have strong avidity to and uptake the maximum amount of safranin
• C. They do not take up safranin
• D. They stain yellow

Answer: (B)

Pseudomonads are Gram-negative organisms, so in the Gram stain the crystal violet-iodine complex is washed out during the decolorization step. They then readily take up the safranin counterstain, resulting in a pink/red appearance. This strong affinity for safranin explains why the statement about uptake of the maximum amount of safranin is true. The other descriptions don’t fit Gram staining outcomes for these bacteria: they do take up safranin (not avoid it), they are not colored yellow, and their staining with safranin is not weak.

Pseudomonads are Gram-negative organisms, so in the Gram stain the crystal violet-iodine complex is washed out during the decolorization step. They then readily take up the safranin counterstain, resulting in a pink/red appearance. This strong affinity for safranin explains why the statement about uptake of the maximum amount of safranin is true. The other descriptions don’t fit Gram staining outcomes for these bacteria: they do take up safranin (not avoid it), they are not colored yellow, and their staining with safranin is not weak.