The Power of Positive Thinking: How Gram Staining Unveils the Color of Bacteria

What makes Gram-positive bacteria appear purple in color?

a) Thick cell wall b) Thin cell wall c) Outer membrane d) Peptidoglycan layer

Final answer: a) Thick cell wall

Answer:

In the process of Gram staining, Gram-positive bacteria appear purple due to their thick cell wall that retains the crystal violet dye.

Explanation: In the classification of bacteria using the Gram stain technique, Gram-positive bacteria are characterized by a purple color after the staining process. This coloration is due to the presence of a thick peptidoglycan layer in the cell walls of Gram-positive bacteria, which retains the crystal violet dye used in the process.

On the other hand, Gram-negative bacteria appear pink after the process because they have a thinner peptidoglycan layer and an outer membrane that does not retain the crystal violet dye, instead taking up the counterstain, usually safranin.

For example, in a Gram-stained specimen, the violet rod-shaped cells forming chains are the Gram-positive bacteria Bacillus cereus, and the small, pink cells are the Gram-negative bacteria Escherichia coli. When performing a Gram stain, Gram-positive cells resist decolorization and remain purple, while the dye is released from Gram-negative cells, which are then counterstained pink.