Question

Staining material of gram positive bacterium is

• A. Fast green
• B. Haematoxylin
• C. Crystal violet
• D. Safranin

Hint:

Crystal violet is the primary stain used in Gram staining, which helps differentiate Gram-positive bacteria from Gram-negative bacteria.

Answer 1

The Correct Option is C

Step 1: Understanding Gram staining.
In Gram staining, a differential staining technique, gram-positive bacteria retain the crystal violet stain, appearing purple under the microscope due to their thick peptidoglycan cell wall.
Step 2: Analyzing the options.
(1) Fast green: Incorrect, fast green is not used in Gram staining.
(2) Haematoxylin: Incorrect, haematoxylin is used for staining cell nuclei, not for Gram staining.
(3) Crystal violet: Correct — Crystal violet is the primary stain used in Gram staining to color the cell walls of Gram-positive bacteria.
(4) Safranin: Incorrect, safranin is used as a counterstain for Gram-negative bacteria in the Gram staining procedure.
Step 3: Conclusion.
The correct stain for Gram-positive bacteria is (3) Crystal violet.

Answer 2

Gram staining relies on differences in cell wall structure to differentiate bacteria, using a sequence of specific dyes. Let's check each option against its role in this procedure.

1. Fast green: Fast green is a counterstain used in some histological techniques, such as staining collagen or cytoplasm, but it is not part of the standard Gram staining protocol.
2. Haematoxylin: Haematoxylin is used to stain cell nuclei in histology, unrelated to differentiating bacterial cell wall types in Gram staining.
3. Crystal violet: Crystal violet is the primary stain applied first in Gram staining. Gram-positive bacteria retain this dye within their thick peptidoglycan layer even after decolorization, giving them their characteristic purple color.
4. Safranin: Safranin is applied as the counterstain at the end of the procedure, coloring Gram-negative bacteria (which lose the crystal violet during decolorization) pink to red.

Since Gram-positive bacteria are defined by their retention of the primary stain, crystal violet is the dye responsible for their staining.

Therefore, the correct answer is Crystal violet.