Question

hans: did you pay attention? what is the outcome of a well-executed gram stain?
a) both gram-positive and gram-negative appear purple
b) both gram-positive and gram-negative appear pink
c) gram-positive appear pink, and gram-negative appear purple
d) gram-positive appear purple, and gram-negative appear pink

Explanation:

Gram - staining is a common technique in microbiology. Gram - positive bacteria have a thick peptidoglycan layer. During the Gram - staining process, after the initial staining with crystal violet (a purple dye), the iodine mordant fixes the dye. When decolorized, the thick peptidoglycan layer of Gram - positive bacteria retains the purple crystal violet - iodine complex. Gram - negative bacteria have a thin peptidoglycan layer and an outer membrane. The decolorizing step removes the crystal violet - iodine complex from Gram - negative bacteria. Then, the counter - stain (usually safranin, which is pink) stains the Gram - negative bacteria pink.

Answer:

D. Gram - positive appear purple, and Gram - negative appear pink