SERIES MICROBIOLOGY LAB - STAINS COMPLETE QUESTIONS AND CORRECT ANSWERS | GRADED AND THE LATEST SERIES

2025-2026 SERIES
MICROBIOLOGY LAB - STAINS COMPLETE
QUESTIONS AND CORRECT ANSWERS | GRADED
AND THE LATEST SERIES
Simple stain


Ans: -Add color to cells for viewing
-Highlight entire organism's shape and basic structures
-Includes:
Methylene blue
Safranin
Crystal violet
Carbolfuchsin


Question: Negative stain


Ans: -Enhances viewing of morphology, capsules
-Bacteria are live
-No heat fixing! (no denaturing)
-Nigrosin ink
-View under oil
-Anionic (acidic) simple stain


Question: Gram stain


Ans: -Determines cell wall type (gram positive or negative)
-Differential stain

, 2025-2026 SERIES
Question: Gram stain procedure


Ans: 1. Crystal violet
2. Iodine (mordant)
3. Alcohol (decolorizer)
4. Safranin (counterstain)
5. Observe under oil


Question: Mordant - gram stain


Ans: -Increases intensity of crystal violet
-Iodine enters cell forms crystal violet-iodine complex (CV-I)
-Complex is too large to leave the cell


Question: Alcohol - gram negative


Ans: -Decolorizer
-Dissolves lipids in the outer membrane
-Allows CV-I complex to leave cell, making it colorless


Question: Safranin - gram stain


Ans: -Counter stain
-Will only stain gram negative cells


Question: Alcohol - gram positive