Question

Name the method used for staining of a bacteria culture.

• A. PAS staining
• B. Fuelgen staining
• C. Gram's staining
• D. Cotton blue staining

Hint:

Gram stain is always the first diagnostic step when identifying unknown bacterial isolates in fish disease diagnostics.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Bacterial staining is essential to visualize bacterial cells under a microscope and classify them based on their cell wall structure.

Step 2: Detailed Explanation:
Gram's staining is the most widely used differential staining method in bacteriology.
It classifies bacteria into two broad groups: Gram-positive (which retain crystal violet dye and appear purple due to a thick peptidoglycan layer) and Gram-negative (which take up the counterstain safranin and appear pink/red due to a thin peptidoglycan layer and outer membrane).
PAS (Periodic acid–Schiff) staining is used to detect glycogen and mucins in histology.
Feulgen staining is specific for DNA.
Cotton blue (with lactophenol) is used primarily for fungal staining.

Step 3: Final Answer:
Gram's staining is the standard method used to stain and classify bacterial cultures.