Questions and Answers
What is the purpose of capsular staining?
To examine the capsule surrounding the plasma membrane.
What are the two functions of the capsule in bacterial cells?
It protects the cell from phagocytosis by white blood cells, and allows it to attach to solid surfaces.
What is glycocalyx?
A polysaccharide shell that surrounds the membrane, meaning sugar cell.
Do you heat fix a capsular stain?
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If the layer around the cell wall is distinct and gelatinous, it is a...
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If the layer around the cell wall is diffuse and irregular, it is a...
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What kind of bacteria did we look at with capsular staining?
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Procedure for capsular staining: 1. Spread organism across slide (May need an H2O drop), 2. air drop, 3. Crystal violet (2 min), 4. Rinse with H2O, 5. ___
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What is the purpose of negative staining?
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How do negative stains work?
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What does the stain look like in negative staining?
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Do you heat fix the negative stain?
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Can you see a capsule with negative staining?
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What are the kinds of stains used for negative staining?
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What bacteria did we use for negative staining?
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Why is alcohol widely used as an antiseptic on the skin?
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True or false: The number of bacteria on human skin does not vary in different parts of the body.
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What kinds of alcohol are used as effective antiseptics?
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What does alcohol do to bacteria?
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True or false: Proteins are more soluble in solutions of alcohol.
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True or false: Alcohols are effective against endospores and naked viruses.
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What is an advantage of alcohol as an antiseptic?
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What is a disadvantage of alcohol as an antiseptic?
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Study Notes
Capsular Staining
- Purpose: To observe the capsule surrounding the plasma membrane of bacterial cells.
- Capsule Functions: Protects bacteria from phagocytosis by white blood cells and facilitates attachment to solid surfaces.
- Glycocalyx: A polysaccharide layer encasing the membrane, often referred to as a "sugar cell."
- Heat Fixing: Not performed; it can distort cells and damage the capsule.
Types of Capsules
- Distinct and Gelatinous Layer: Identifies as a capsule.
- Diffuse and Irregular Layer: Identifies as a slime layer.
Bacterial Examples
- Capsular Staining Bacteria: Observed Streptococcus pneumoniae and Klebsiella pneumoniae in tooth plaque.
- Negative Staining Bacteria: Dental plaque and Klebsiella pneumoniae.
Capsular Staining Procedure
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Steps:
- Spread organism on a slide (may add a drop of water).
- Air dry.
- Apply crystal violet for 2 minutes.
- Rinse with water.
- View under a microscope.
Negative Staining
- Purpose: Used to examine morphology and structures like capsules; provides accurate measurement of cell dimensions.
- Mechanism: Negative stains are acidic and composed of negatively charged chromophores, repelling instead of penetrating the cell.
- Staining Appearance: Dark background with white bacteria.
- Heat Fixing: Typically avoided to prevent shrinkage of the cell and capsule.
Visibility of Capsules
- Capsule Observation: Possible with negative staining combined with positive staining.
Negative Stains Used
- Common Stains: Nigrosin and India ink.
Antiseptic Use of Alcohol
- Purpose: Used to inhibit bacteria, especially pathogens, during medical procedures like blood drawing.
- Effective Alcohols: Ethyl and isopropyl alcohol are effective antiseptics for skin.
- Action on Bacteria: Denatures proteins and damages cell membranes.
Skin Bacteria Variability
- True/False Statement: The number of bacteria varies by body location and moisture levels.
Alcohol Properties
- Solubility: Proteins are more soluble in alcohol solutions.
- Effectiveness Against Microbes: Alcohols do not affect endospores or naked viruses.
Advantages and Disadvantages of Alcohol
- Advantage: Relatively non-toxic to human skin.
- Disadvantage: Volatile nature can reduce effectiveness over time.
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Description
This quiz focuses on essential concepts from microbiology labs regarding capsule staining and the functions of the bacterial capsule. Test your knowledge on key definitions and functions of the glycocalyx and its significance to bacterial cells. Perfect for students revising lab content!
