Q: Which formula correctly calculates the total magnification of a microscope?

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

Question 1

Which Biosafety Level (BSL) is appropriate for handling microbes that pose a moderate risk to healthy adults and are unlikely to spread throughout the community, but require specific training and availability of treatment?

Accepted Answer

BSL-2

Question 2

A student is using a compound light microscope and wants to view unstained cells at the highest possible resolution. Which objective lens and adjustment should they use?

Accepted Answer

Use the 100x oil immersion lens with the fine adjustment knob

Question 3

During a Gram stain, what is the primary reason that Gram-positive bacteria retain the crystal violet stain after the decolorization step?

Accepted Answer

They have a thick layer of peptidoglycan

Question 4

Which of the following best describes a defined medium?

Accepted Answer

A medium where the exact chemical composition is known

Question 5

A microbiologist is trying to isolate a pure culture of E. coli from a mixed sample. Which method should they use to ensure isolation of single colonies?

Accepted Answer

Streak plate method

Question 6

Which of the following statements about the Schaeffer-Fulton method for endospore staining is correct?

Accepted Answer

Malachite green stains the spores and safranin stains the vegetative cells

Question 7

Which of the following is NOT a nutritional requirement for bacterial growth?

Accepted Answer

Chlorophyll

Question 8

A student observes that after Gram staining, some bacteria appear pink while others appear purple. What is the most likely explanation?

Accepted Answer

The purple bacteria are Gram-positive and the pink are Gram-negative

Question 9

Which formula correctly calculates the total magnification of a microscope?

Accepted Answer

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

Question 10

Which of the following best describes a chemoorganotroph?

Accepted Answer

An organism that derives energy from the breakdown of organic molecules by fermentation

Question 11

A microbiologist is culturing bacteria in a medium that contains eosin and methylene blue. Only Gram-negative bacteria grow, and colonies of E. coli appear metallic green. What type of medium is this?

Accepted Answer

Selective and differential medium

Question 12

Which of the following statements about the use of oil with the 100x objective lens is correct?

Accepted Answer

Oil increases the refractive index and improves resolution

Question 13

Which of the following is a correct step in the Gram staining procedure?

Accepted Answer

Decolorize with alcohol after applying iodine

Question 14

Which of the following best describes the function of the condenser in a compound microscope?

Accepted Answer

It focuses light onto the specimen

Question 15

A student is asked to distinguish between Streptococcus and Staphylococcus using a microscope. Which arrangement would indicate Streptococcus?

Accepted Answer

Chains of spherical cells

Question 16

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

Accepted Answer

Crystal violet, iodine, alcohol, safranin

Question 17

Which of the following statements about negative staining is correct?

Accepted Answer

Negative staining uses an acidic dye to stain the background, leaving cells clear

Question 18

Which of the following is a reason for using aseptic techniques in microbiology?

Accepted Answer

To prevent contamination of cultures and protect the experimenter

Question 19

Which of the following groups of bacteria would grow at the top of a thioglycollate medium tube?

Accepted Answer

Obligate aerobes

Question 20

A microbiologist is using a medium that contains sodium thioglycollate, cysteine, and resazurin. What is the primary purpose of this medium?

Accepted Answer

To determine the oxygen requirements of bacteria

Microbiology Lab Study Guide: Microscopy, Staining, Bacterial Classification, and Culturing Techniques

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