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Questions and Answers
What is the primary stain used in the gram staining procedure?
What is the primary stain used in the gram staining procedure?
- Safranin
- Ethanol
- Crystal violet (correct)
- Iodine solution
What role does the iodine solution play in gram staining?
What role does the iodine solution play in gram staining?
- It stains the decolorized bacteria
- It prepares the slide for microscopic examination
- It cleans the slide of excess stain
- It acts as a mordant forming a complex with the primary stain (correct)
During which step is the decolorization of gram-negative bacteria achieved?
During which step is the decolorization of gram-negative bacteria achieved?
- Washing with water
- Applying safranin
- Washing with 95% ethanol (correct)
- Adding crystal violet
What color do gram-positive bacteria appear after the gram staining process?
What color do gram-positive bacteria appear after the gram staining process?
What is the purpose of the counterstain in gram staining?
What is the purpose of the counterstain in gram staining?
Which statement accurately describes the gram staining process?
Which statement accurately describes the gram staining process?
What is formed when iodine is added to the crystal violet in the gram staining process?
What is formed when iodine is added to the crystal violet in the gram staining process?
What occurs during the washing step with 95% ethanol in gram staining?
What occurs during the washing step with 95% ethanol in gram staining?
Flashcards
Gram-positive bacteria
Gram-positive bacteria
Bacteria with thick peptidoglycan layers in their cell walls, retaining crystal violet stain during decolorization.
Gram-negative bacteria
Gram-negative bacteria
Bacteria with thin peptidoglycan layers and an outer membrane, losing crystal violet stain and taking up counterstain (safranin).
Gram staining
Gram staining
A technique to distinguish between gram-positive and gram-negative bacteria based on cell wall differences.
Primary stain
Primary stain
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Mordant
Mordant
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Decolorization
Decolorization
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Counterstain
Counterstain
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Peptidoglycan
Peptidoglycan
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Study Notes
Gram Staining Procedure
- Prepare a thin bacterial smear on a slide.
- Cover the smear with crystal violet (primary stain) for a minute.
- Wash the slide with water to remove excess stain.
- Add iodine solution (mordant) for a minute.
- Rinse with water.
- Decolorize with 95% ethanol for 10-30 seconds.
- Rinse with water.
- Counterstain with safranin for a minute.
- Rinse and observe under a microscope.
Gram-Positive vs. Gram-Negative
- Gram-positive bacteria: Retain the crystal violet stain, appearing purple. Possess a thick peptidoglycan layer in their cell walls.
- Gram-negative bacteria: Lose the crystal violet stain after decolorization. They take up the counterstain (safranin), appearing pink/red. Have a thin peptidoglycan layer and an outer membrane.
Gram Staining Principle
- The process distinguishes bacteria based on differences in their cell wall structure.
- The thick peptidoglycan layer in Gram-positive bacteria traps the crystal violet-iodine complex, while the thin layer in Gram-negative bacteria allows the complex to be removed during decolorization.
Gram Staining Results
- Gram-positive: Purple
- Gram-negative: Pink/red
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Description
Explore the Gram staining procedure, which is essential for classifying bacteria into Gram-positive and Gram-negative. This quiz covers the steps involved in the staining process, the characteristics of both types of bacteria, and the underlying principles of the method. Test your knowledge on this key microbiological technique.
