Microbiology Lab Test 2 Flashcards

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Questions and Answers

What is the purpose of the Capsule Stain?

To differentiate bacteria with and without capsules (correct)

To determine Gram reaction

To identify bacterial size

To check for motility

What organism is used in the Capsule Stain?

Klebsiella pneumoniae

What prevents phagocytosis in bacteria that produce capsules?

Virulence factors

What is the capsule made of?

Polypeptides or Polysaccharides Signup and view all the answers

What is the effect of bacteria that have capsules on infection?

It makes it harder for the immune system to eliminate them. Signup and view all the answers

Capsules are extracellular structures.

True Signup and view all the answers

Why is it hard to stain a capsule?

The encapsulated nucleoid layer resists staining. Signup and view all the answers

How can we view whether or not a capsule is present?

Using an acidic and a basic stain. Signup and view all the answers

What is the purpose of using an acidic stain on a capsule stain?

To do a negative stain to color the background. Signup and view all the answers

What is the purpose of the basic stain in capsule staining?

To stain the cell membrane. Signup and view all the answers

What is heat-fix?

It fixes cells to the slide and kills them. Signup and view all the answers

What does a negative stain utilize?

An acidic dye solution. Signup and view all the answers

Why do bacteria remain unstained in the negative staining procedure?

Negative stains are repelled by the negative charge of the bacterial cell wall. Signup and view all the answers

Why is heat fixation not used in negative staining?

It distorts the bacteria. Signup and view all the answers

What is a common organism used in negative staining?

Micrococcus luteus Signup and view all the answers

What is a pathogen?

A bacterium, virus, or microorganism that can cause disease. Signup and view all the answers

What is an opportunistic pathogen?

A pathogen that infects hosts with weakened immune systems. Signup and view all the answers

What is the difference between slant and broth cultures?

Broth contains more bacteria than slant. Signup and view all the answers

What are polysaccharides?

Carbohydrates made of sugar molecules bonded together. Signup and view all the answers

What is keratin?

A tough protein found in spores. Signup and view all the answers

What can influence antibiotic treatments?

Gram stain results. Signup and view all the answers

What type of charge does Crystal Violet dye carry?

Cationic Signup and view all the answers

What charge do bacterial cell surfaces have?

Anionic Signup and view all the answers

What is the purpose of the mordant in Gram staining?

To fix the Crystal Violet to the peptidoglycan layer. Signup and view all the answers

What happens to Gram-negative bacteria during the decolorization process?

The purple complex is washed out. Signup and view all the answers

What effect does ethanol have on Gram-positive bacteria?

It has no effect due to their thick cell walls. Signup and view all the answers

What purpose does Safranin serve for Gram-negative bacteria?

It turns them pink/red. Signup and view all the answers

What occurs to cell walls that are old or stressed?

They become thin. Signup and view all the answers

What can the Gram reaction indicate?

It helps determine appropriate antibiotic treatments. Signup and view all the answers

What is a simple stain?

A staining procedure using only one dye. Signup and view all the answers

What are examples of simple stains?

Crystal Violet, Safranin, Methylene Blue, and Malachite Green Signup and view all the answers

What is the Wet Mount preparation technique?

A specimen is placed in a drop of water on a microscope slide. Signup and view all the answers

What are the advantages of the Wet Mount method?

Determines motility, morphology, and does not involve heat. Signup and view all the answers

What was a common organism used in the Hanging Drop method?

Staphylococcus Epidermis Signup and view all the answers

What are the three types of movement observed in the Hanging Drop method?

True motility, Brownian movement, and wave movement. Signup and view all the answers

What is the primary stain used in an Endospore Stain?

Malachite Green Signup and view all the answers

Why is steam heating required in an Endospore Stain?

To soften the outer layers of the endospore. Signup and view all the answers

What is the decolorization agent in an Endospore stain?

Water Signup and view all the answers

What color do Spore Mother cells turn after counterstaining?

Red/Pink Signup and view all the answers

What color are endospores after staining?

Green Signup and view all the answers

What does the presence of a green spore indicate?

Endospore positive. Signup and view all the answers

What is a common endospore stain organism?

Bacillus subtilis Signup and view all the answers

Study Notes

Capsule Stain

Differential stain used to identify bacteria with capsules.
Capsules are slime layers found outside bacterial cells, preventing phagocytosis.
Commonly demonstrated using Klebsiella pneumoniae.
Procedure: Use Congo Red or Nigrosin to stain background, no heat fixing, then apply Maneval’s stain.

Capsule Characteristics

Composed of polypeptides or polysaccharides.
Capsules contribute to virulence by protecting bacteria from the immune system.
Considered extracellular components as they are secreted outside of the cell wall.

Staining Techniques

Capsules are resistant to staining due to their nucleoid layer.
Acidic and basic stains are used: acidic stains create a negative stain, while basic stains color the cell membrane.
Negative stains (like Nigrosin or Eosin) do not penetrate bacteria but create a clear distinction against a dark background.

Bacterial Survival

Capsules enhance survival by evading the immune response, making infections harder to clear.
Older or heat/stress-stricken bacteria may have thinner cell walls, affecting staining.

Types of Stains

Acid-fast stain identifies mycolic acids in bacteria such as Mycobacterium using ZN Carbolfuchsin, resulting in a pink color for positive specimens.
Gram stain differentiates gram-positive (purple) from gram-negative (reddish-pink) bacteria using crystal violet and safranin, crucial for determining appropriate antibiotic treatment.

Bacterial Enumeration and Growth

CFU (Colony Forming Units) quantify bacterial colonies after incubation.
Defined media offers known compositions, while undefined or complex media supports a wider variety of organisms.

Movement and Observation Techniques

Wet mount and hanging drop methods are used to observe live bacterial movement and morphology without heat fixation.
True motility, Brownian movement, and wave movement are types of observed motion.

Endospore Staining

Endospore stain indicates presence and location of spores, primarily in Bacillus and Clostridium genera.
Malachite green is the primary stain, requiring steam heating for penetration; safranin serves as the counterstain.

General Microbiology Concepts

Pathogens can cause disease in hosts; opportunistic pathogens infect those with weakened immune systems.
Simple staining elucidates cell morphology, using basic dyes like crystal violet and methylene blue. No heat is used in wet mount preparations to reduce distortion.

Laboratory Tools

Tools like inoculating loops, glass spreading rods, and pipettes are essential for microbiological techniques and sample handling.

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Description

Test your knowledge on capsule staining techniques and definitions in microbiology. This set of flashcards covers key concepts and methodologies used in identifying bacteria with capsules, particularly focusing on the Congo Red and Nigrosin staining techniques. Perfect for microbiology students preparing for their lab tests.