Question 1

Bacteria capsules can best be visualized by _______ staining.

Accepted Answer

Negative staining involves using a negative stain, such as India ink or nigrosin, which does not penetrate bacterial capsules, resulting in a clear halo around the stained cell. This technique is often used to visualize bacterial capsules. Flagellar staining is used to visualize bacterial flagella, crystal violet staining is commonly used in Gram staining to distinguish between different types of bacteria, and mordant staining is used to enhance the adherence of stains to bacterial cell walls.

Question 2

The counterstain in a spore stain is

Accepted Answer

In a spore stain, malachite green is used as the primary stain to stain the endospores. The counterstain is used to stain the vegetative cells. Safranin is frequently used as the counterstain in a spore stain.

Question 3

Compare and contrast light microscopy to electron microscopy. Be sure to include how they work and what they can see (or the extent of their total magnification).

Accepted Answer

The answer of Compare and contrast light microscopy to electron...

Question 4

Why do basic dyes attach to most bacterial surfaces?

Accepted Answer

Basic dyes are positively charged, and most bacterial surfaces are negatively charged due to the presence of cell wall components like teichoic acids, lipopolysaccharides, and peptidoglycans. This charge interaction leads to the attachment of basic dyes to most bacterial surfaces.

Question 5

Which type of staining results in a clear object being viewed against a dark background

Accepted Answer

A negative stain involves staining the background instead of the specimen, resulting in a clear object being viewed against a dark background. Simple stains are used for basic visualization of the overall shape and size of the specimen. Endospore stains and flagellar stains are used to specifically stain endospores and flagella, respectively, and do not necessarily result in a clear object against a dark background.

Question 6

Which stain would be the best choice for detecting mycobacterium (the bacteria responsible for tuberculosis and leprosy)?

Accepted Answer

Acid-fast stain is used for detecting mycobacterium because these bacteria have a unique cell wall that is high in lipids, which makes them resistant to most staining techniques. Acid-fast stain involves using a strong acid to penetrate the lipid-rich cell wall, which allows the stain to adhere to the bacteria and appear red under the microscope. None of the other stain options would be effective at detecting mycobacterium.

Question 7

In a properly executed Gram stain,Gram positive organisms appear ________ while Gram negative organisms appear ________.

Accepted Answer

Gram positive organisms appear purple because the crystal violet-iodine complex is trapped in their thick peptidoglycan layer while Gram negative organisms appear pink because they have thinner peptidoglycan and an outer membrane that allows the crystal violet to be washed out during the decolorization step, and the safranin counterstain is retained.

Question 8

What statement about microscopy and staining techniques is false?

Accepted Answer

Staining and microscopic examination are not always enough to identify a microorganism. Additional tests such as biochemical tests may be necessary for accurate identification.

Question 9

When given a microorganism to identify,which of the following would be useful?

Accepted Answer

All of the options are useful in identifying a microorganism: a gram stain helps determine the cell wall structure, a transmission electron micrograph provides detailed images of the microorganism's ultrastructure, and biochemical and genetic characteristics offer specific identification and classification information.

Question 10

Would light of a higher or lower wavelength give you better resolution when using a microscope? Why? Would a light microscope that had a total magnification of 500X give you better resolution than one that has a magnification of 100X? Why?

Accepted Answer

The answer of Would light of a higher or lower...

Question 11

If the step involving iodine were left out of a Gram stain,which of the following would best describe the results?

Accepted Answer

The iodine step is responsible for binding the crystal violet stain to the peptidoglycan layer in Gram positive cells, forming a complex that cannot be washed out with alcohol. Therefore, if this step were omitted, Gram positive cells would not retain the violet stain and would appear pink or colorless like Gram negative cells.

Question 12

The stains used in the Ziehl-Neelsen acid-fast stain are

Accepted Answer

The Ziehl-Neelsen acid-fast stain uses carbolfuschin as the primary stain and methylene blue as the counterstain to identify acid-fast bacteria like Mycobacterium species.

Question 13

What is the Wright stain? What does it distinguish?

Accepted Answer

The answer of What is the Wright stain? What does...

Quiz 3: Microscopy and Staining