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Questions and Answers
What are the three major methods of staining in microbiology?
What are the three major methods of staining in microbiology?
- Differential (correct)
- Simple (correct)
- Special (correct)
- Experimental
Which of the following is a basic dye?
Which of the following is a basic dye?
- Eosin
- Methylene blue (correct)
- Crystal violet (correct)
- Nigrosis
Acidic dyes are positively charged.
Acidic dyes are positively charged.
False (B)
What does a simple stain use to color a bacterium?
What does a simple stain use to color a bacterium?
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Bacterial cells are ______ charged, which attracts positively charged basic dyes.
Bacterial cells are ______ charged, which attracts positively charged basic dyes.
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Name one reagent used in bacterial staining.
Name one reagent used in bacterial staining.
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What is the importance of preparing a good smear?
What is the importance of preparing a good smear?
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Match the following bacterial arrangements with their types:
Match the following bacterial arrangements with their types:
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Study Notes
Overview of Bacterial Staining
- Staining enhances visibility of microorganisms, allowing for observation of shapes, sizes, and appendages.
- Major staining methods include Simple, Differential, and Special staining techniques.
Materials Needed
- Bacterial cultures: Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), Bacillus subtilis (B. subtilis), and unknown bacteria.
- Common reagents include:
- Crystal Violet
- Gram’s Iodine
- 95% Alcohol
- Safranin
- Methylene Blue
- Equipment such as glass microscope slides, Kim wipes, and an alcohol lamp.
Preparation of Bacterial Smears
- Essential for successful staining, requiring mastery of three key techniques:
- Heat Fixing: Adheres cells to the slide without distortion.
- Thin Smear Preparation: Ensures individual cells are visualized and prevents obscuring details.
- Proper Thickness: Balances between too thin (inability to see individual cells) and too thick (difficulty in observing details).
Types of Dyes
- Basic or Positive Dyes: Positively charged dyes with cationic chromophores that attract negatively charged bacterial cells. Common examples include:
- Methylene Blue
- Crystal Violet
- Basic Fuchsin
- Acidic or Negative Dyes: Negatively charged dyes that repel bacterial cells. Common examples include:
- Nigrosin
- India Ink
- Eosin
Simple Staining Technique
- Involves using a single stain to color colorless bacterial cells for easier visualization.
Bacterial Cell Arrangement
- Bacteria can be characterized by the arrangement of cells:
- Diplo: Cells form pairs.
- Strepto: Cells form chains.
- Staphylo: Cells form clusters.
- Tetrad: Cells form groups of four.
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