Laboratory #3 – Structural Stains

These flashcards cover key concepts and procedures related to structural stains in bacteria, including capsule staining, endospore staining, and motility testing.

What is the objective of Laboratory #3?

To learn how to stain bacteria to observe unique external structures.

What are capsules in bacteria?

Mucilaginous substances of carbohydrate nature surrounding bacterial cells.

What are endospores?

Dormant, hardy, protective structures produced by some bacteria under stress.

What is the key feature of endospores?

They contain the bacterium's DNA and ribosomes and are resistant to harsh conditions.

What happens to a bacterium when the endospore germinates?

A new vegetative cell emerges.

How can motility in bacteria be determined?

By using motility test media that allows motile bacteria to move away from the inoculation site.

What does TTC indicate in motility tests?

It indicates bacterial growth when reduced, creating a purple formazan.

What is flagella in bacteria made of?

A single type of protein called flagellin.

How do flagella assist bacteria?

They allow bacteria to generate propulsion to move.

What type of structure is a capsule around bacterial cells?

A mucilaginous layer that can be water-soluble.

What does a purple halo around endospores indicate?

The endospores are clear due to their hardy structure and will not absorb the stain.

What type of bacteria are used for capsule staining in the experiment?

Staphylococcus aureus and Klebsiella pneumoniae.

What color does crystal violet turn the capsules during staining?

Bluish violet.

What is the purpose of washing with 20% copper sulfate during capsule staining?

To prevent removal of the water-soluble capsule and stain it light blue.

Why is heat fixing important when staining endospores?

It helps the bacteria adhere to the slide and prepares them for staining.

What should not be done to the smears when staining for capsules?

They should not be heat fixed.

What is the procedure to observe endospores in the microscope?

Stain with crystal violet, rinse, and observe under high magnification.

What are the signs of bacteria being motile in the motility agar test?

They will move away from the stab line in the media.

What initial step is crucial for inoculating the motility tube?

Sterilizing the inoculation needle with a flame.

What two bacterial cultures are used in the motility agar test?

Staphylococcus aureus and Serratia marcescens.

At what temperature are the inoculated motility tubes incubated?

37 degrees Celsius.

What is the consequence for bacteria when conditions become favorable after germination?

The bacteria will grow and reproduce.

What visual cue indicates bacterial growth in motility media?

A purple color due to TTC reduction.

What is the role of the basal body in flagella?

It anchors the flagella to the cytoplasmic membrane.

What is the function of motility test media?

To allow motile bacteria to spread from the inoculation line.

Which bacterial strain is used for endospore staining?

Bacillus subtilis.

What is the result of reducing TTC in motility agar?

The appearance of a purple color indicating growth.

During capsule staining, what happens if water is used in the procedure?

It can dissolve and remove the water-soluble capsule.

What structure allows some bacteria to move towards nutrients?

Flagella.

What is a unique characteristic of bacterial endospores?

They are extremely resistant to environmental stresses.

Which reagent is used to rinse off crystal violet in capsule staining?

20% copper sulfate solution.

What is the main cellular component inside an endospore?

The bacterium's DNA and ribosomes.

What are the two main colors observed during the endospore staining process?

Purple for the vegetative cell and clear for the endospore.

What changes occur in the media when motile bacteria grow?

The media shows a diffused purple coloration away from the stab line.

What is the role of flagella in the behavior of bacteria?

They enable bacteria to respond to environmental stimuli.

What should be done to the microscope slides after staining?

They should be air-dried.

Which type of bacteria generally have flagella?

Some bacteria, which may have single flagella, tufts of flagella, or flagella all over their surface.

Why is it important to carefully perform the inoculation in motility agar?

To ensure accuracy in determining the motility of the bacteria.

What should be done before placing the inoculation needle into the motility media?

The inoculation needle should be sterilized in a flame.

At which magnifications should the microscope be used to observe the stained samples?

Starting at 4x, then moving through 10x, 40x, and to 100x with oil immersion.