Pewarnaan Gram

Summary

The video demonstrates Gram staining, a microbiological technique used to distinguish bacteria based on how their cell walls respond to staining and alcohol decolorization.

• Gram-positive bacteria have thicker cell walls and retain the crystal violet stain, appearing purple or blue.
• Gram-negative bacteria lose the crystal violet during decolorization and take up safranin, appearing pink or red.

The presenter credits Danish bacteriologist Hans Christian Gram with discovering the technique in 1884. The video shows a purple, grape-like cluster of cocci as an example of Gram-positive bacteria and red-stained bacteria as an example of Gram-negative bacteria.

Procedure Shown

1. Wear protective equipment: gloves, a mask, a laboratory coat, and closed shoes.
2. Prepare the bacterial smear:
   • Sterilize the inoculating loop in a flame until it glows, then allow it to cool.
   • Use the loop to transfer about one loopful of bacteria from an isolate.
   • Mix the bacteria with sterile sodium chloride solution on a glass slide, making an oval smear about 2–3 cm across.
   • Let the smear dry.
3. Fix the smear: Pass the slide through the flame three times, then place it on a staining rack.
4. Apply the primary stain: Cover the smear with gentian violet (crystal violet) for 1 minute. Drain vertically and rinse gently with running water.
5. Apply Lugol’s iodine: Cover the smear for 1 minute, then drain and rinse.
6. Decolorize: Apply alcohol until the primary color disappears. Gently agitate, then rinse with running water.
7. Apply the counterstain: Cover the smear with safranin for 30 seconds, then drain and rinse.
8. Dry and examine: Dry the slide and observe it under a microscope. Purple or blue cells are identified as Gram-positive; red or pink cells are identified as Gram-negative.

Speakers and Sources Featured

• Presenter/instructor: An unnamed narrator who explains and demonstrates the staining procedure.
• Historical figure mentioned: Hans Christian Gram, credited by the presenter with discovering Gram staining; he is not presented as a speaker.