Question 1

Which of the following best explains why electron microscopes have a higher resolving power than light microscopes?

Accepted Answer

Electrons have a much shorter wavelength than visible light.

Question 2

A microbiologist observes a specimen using a compound light microscope with a 40X objective lens and a 10X ocular lens. What is the total magnification?

Accepted Answer

$$40 	imes 10 = 400$$

Question 3

Which staining technique would you use to differentiate between bacteria with thick peptidoglycan layers and those with thin peptidoglycan layers?

Accepted Answer

Gram stain

Question 4

During the Gram stain procedure, what is the primary function of iodine?

Accepted Answer

To fix the crystal violet dye within the cell wall

Question 5

A sample is stained with carbolfuchsin, heated, decolorized with acid-alcohol, and counterstained with methylene blue. Acid-fast bacteria will appear:

Accepted Answer

Red

Question 6

Which of the following best describes the purpose of using immersion oil with a 100X objective lens?

Accepted Answer

To prevent refraction of light and increase resolution

Question 7

A laboratory technician performs a negative stain using India ink. What will be the appearance of bacterial cells under the microscope?

Accepted Answer

Cells will appear colorless against a dark background

Question 8

Which of the following is a key advantage of the scanning electron microscope (SEM) over the transmission electron microscope (TEM)?

Accepted Answer

SEM provides detailed 3-D images of specimen surfaces

Question 9

A bacterial culture is tested with an antiserum and agglutination occurs. What does this indicate?

Accepted Answer

The bacteria possess antigens recognized by the antibodies in the antiserum

Question 10

Which of the following best explains why heat fixation is used when preparing a bacterial smear for staining?

Accepted Answer

It kills the cells and causes them to adhere to the slide

Question 11

A microbiologist wants to identify a bacterium based on its ability to ferment lactose. Which type of test should be used?

Accepted Answer

Biochemical test

Question 12

Which of the following statements about simple stains is correct?

Accepted Answer

Simple stains reveal basic cell shapes and arrangements

Question 13

Which of the following best describes the result of a successful endospore stain using the Schaeffer-Fulton method?

Accepted Answer

Endospores appear green and vegetative cells appear pink

Question 14

Which of the following is a reason why a Gram-positive bacterium might appear pink after Gram staining?

Accepted Answer

The decolorization step was too long

Question 15

A scientist is using a fatty acid methyl ester (FAME) analysis to identify a bacterium. What is the principle behind this technique?

Accepted Answer

Each bacterium has a unique pattern of fatty acid methyl esters detectable by gas chromatography

Question 16

Which of the following best describes the principle of contrast in microscopy?

Accepted Answer

Contrast is the difference between the object and the background

Question 17

Which of the following stains would be most appropriate to visualize bacterial capsules?

Accepted Answer

Capsule stain (negative stain followed by simple stain)

Question 18

A student observes two closely spaced dots under a microscope. With high resolving power, the dots appear as two distinct objects. Which equation best describes the relationship between resolving power ($$R) $$and wavelength ($$\lambda$$)?

Accepted Answer

$$R \propto \frac{1}{\lambda}$$

Question 19

Which of the following best describes the main difference between a simple and a compound microscope?

Accepted Answer

A simple microscope uses a single lens, while a compound microscope uses multiple lenses for magnification

Microscopy, Staining, and Classification in Microbiology

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