Questions and Answers
What are the three major methods of staining in microbiology?
Which of the following is a basic dye?
Acidic dyes are positively charged.
False
What does a simple stain use to color a bacterium?
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Bacterial cells are ______ charged, which attracts positively charged basic dyes.
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Name one reagent used in bacterial staining.
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What is the importance of preparing a good smear?
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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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Description
This quiz focuses on Laboratory 6 of the Microbiology course, which covers bacterial staining techniques. It emphasizes the importance of stained preparations for observing microbial morphology and includes details on various staining methods like simple and differential. Test your understanding of laboratory procedures and the use of stains.
