$$\text{Total Magnification} = \text{Objective Magnification} \times \text{Ocular Magnification}$$

Question 1

Which of the following best describes the relationship between magnification and field of view in a compound light microscope?

Accepted Answer

As magnification increases, the field of view decreases.

Question 2

A student is preparing a bacterial smear. After air drying the smear, what is the next critical step before staining?

Accepted Answer

Heat fix the cells by passing the slide through a flame.

Question 3

Which of the following is NOT a component of Personal Protective Equipment (PPE) in the microbiology lab?

Accepted Answer

Open-toed sandals

Question 4

During Gram staining, what is the primary function of the mordant (Gram’s iodine)?

Accepted Answer

To form an insoluble complex with crystal violet, locking it inside the cell

Question 5

Which genus of bacteria is known for forming endospores and causing diseases such as anthrax and tetanus?

Accepted Answer

Bacillus

Question 6

What is the main selective agent in Mannitol Salt Agar (MSA), and what type of bacteria does it select for?

Accepted Answer

High NaCl concentration; halophilic bacteria

Question 7

Which of the following best explains why oil immersion is used with the 100x objective lens?

Accepted Answer

Oil has the same refractive index as glass, reducing light bending and increasing resolution.

Question 8

Which step in the Gram staining procedure is responsible for differentiating between Gram-positive and Gram-negative bacteria?

Accepted Answer

Decolorization with alcohol or acetone

Question 9

A microbiologist observes pink/red cells after performing a Gram stain. What does this indicate about the bacterial cell wall?

Accepted Answer

The cells are Gram-negative with a thin peptidoglycan layer and an outer membrane.

Question 10

Which of the following best describes a differential staining technique?

Accepted Answer

A technique that uses multiple dyes to distinguish between different groups of organisms.

Question 11

Which of the following equations correctly calculates the total magnification of a compound microscope?

Accepted Answer

$$	ext{Total Magnification} = 	ext{Objective Magnification} 	imes 	ext{Ocular Magnification}$$

Question 12

Which of the following is a correct sequence for the 5 I’s in microbiology?

Accepted Answer

Inoculation, Incubation, Isolation, Inspection, Identification

Question 13

Which of the following best describes the difference between a positive and a negative stain?

Accepted Answer

A positive stain colors the cells, while a negative stain colors the background.

Question 14

Which of the following is a disease caused by an endospore-forming bacterium?

Accepted Answer

Anthrax

Question 15

Which of the following statements about MacConkey agar is TRUE?

Accepted Answer

It selects for Gram-negative bacteria and differentiates lactose fermenters.

Question 16

A student observes a bacterial sample under the microscope using the 40x objective and a 10x ocular lens. What is the total magnification?

Accepted Answer

$$40 	imes 10 = 400$$

Question 17

Which of the following best describes the depth of field in microscopy?

Accepted Answer

The distance from the nearest object plane in focus to the farthest object plane that is simultaneously in focus.

Question 18

Which of the following is a correct safety rule for the microbiology laboratory?

Accepted Answer

Wear closed-toe shoes at all times.

Question 19

Which of the following best explains why bacteria are described as ubiquitous?

Accepted Answer

They are found everywhere on Earth and are highly adaptable.

Question 20

Which of the following is the correct order of reagents used in the Gram staining procedure?

Accepted Answer

Crystal violet, iodine, alcohol, safranin

Microbiology Study Guide: Microscopy, Cell Domains, Staining, and Viruses

Study Guide - Practice Questions