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Questions and Answers
What is the primary purpose of Gram staining?
What is the primary purpose of Gram staining?
What is the first step in the Gram staining procedure?
What is the first step in the Gram staining procedure?
What color do Gram positive organisms appear after Gram staining?
What color do Gram positive organisms appear after Gram staining?
Which solution is used as a mordant in the Gram staining process?
Which solution is used as a mordant in the Gram staining process?
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During the decolorization step, what can happen if ethanol is applied for too long?
During the decolorization step, what can happen if ethanol is applied for too long?
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How long should safranin typically be left on during the Gram staining process?
How long should safranin typically be left on during the Gram staining process?
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What is a key characteristic of Gram negative bacteria in the Gram staining procedure?
What is a key characteristic of Gram negative bacteria in the Gram staining procedure?
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What should be done to the slide after applying the final stain?
What should be done to the slide after applying the final stain?
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Which step of the Gram staining process helps to determine if the crystal violet is still present on the slide?
Which step of the Gram staining process helps to determine if the crystal violet is still present on the slide?
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Study Notes
Gram Staining
- Gram staining is a crucial method for classifying bacteria into Gram-positive or Gram-negative groups.
- It relies on differences in cell wall structure.
- This technique is frequently used as the initial step in bacterial identification.
- However, not all bacteria are definitively identifiable using this method.
Gram Staining Procedure
- Preparation: Begin by creating a heat-fixed smear of the bacterial sample.
- Crystal Violet: Flood the smear with crystal violet for 30 seconds.
- Rinse: Rinse with water.
- Gram's Iodine: Apply Gram's iodine mordant for 1 minute.
- Rinse: Rinse with water.
- Decolorization: Decolorize using 95% ethanol (15-30 seconds, dropwise until crystal violet no longer washes off) or a 3:1 isopropanol-acetone mixture (30-60 seconds).
- Rinse: Rinse with water.
- Counterstain (Safranin): Stain with safranin (60-80 seconds; staining time varies between batches).
- Rinse: Rinse with water.
- Observation: Blot dry and examine under oil immersion.
- Results: Gram-positive bacteria appear blue-purple; Gram-negative bacteria appear pink-red.
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Description
This quiz focuses on the Gram staining technique, a vital process used for classifying bacteria into Gram-positive and Gram-negative groups. It covers the steps involved in the procedure, including preparation, staining, and decolorization. Understanding this method is essential for anyone working in microbiology or related fields.
