$$43 \div (0.1 \times 0.01) = 43,000$$

Question 1

Which of the following best describes the main difference between BSL-1 and BSL-2 microbes?

Accepted Answer

BSL-1 microbes are not known to cause disease in healthy adults, while BSL-2 microbes may cause disease that is usually treatable.

Question 2

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

Accepted Answer

$$10 	imes 40 = 400$$

Question 3

Which of the following statements about resolution in microscopy is correct?

Accepted Answer

Resolution is defined as the shortest distance between two objects where they can still be seen as separate.

Question 4

Which cell arrangement describes a chain of rod-shaped bacteria?

Accepted Answer

Streptobacillus

Question 5

What is the main purpose of using aseptic technique in the laboratory?

Accepted Answer

To prevent contamination of cultures and the environment.

Question 6

Which of the following best explains why a positive stain colors the cells, while a negative stain colors the background?

Accepted Answer

Positive stains are attracted to the negatively charged cell surface, while negative stains are repelled and stain the background.

Question 7

A microbiologist observes a colony that is smooth, round, and yellow on nutrient agar. What is this an example of?

Accepted Answer

Colony morphology

Question 8

Which reagent in the Gram stain procedure acts as the mordant?

Accepted Answer

Iodine

Question 9

Why are endospores more resistant to UV radiation than vegetative cells?

Accepted Answer

Endospores contain protective proteins and DNA repair enzymes.

Question 10

A bacterium grows best at 37°C but can also grow at 25°C and 42°C. What is its optimum temperature?

Accepted Answer

$$37^\circ C$$

Question 11

Which type of organism would you expect to find growing at the bottom of a thioglycollate broth tube, where oxygen is absent?

Accepted Answer

Obligate anaerobe

Question 12

How does UV light primarily damage microbial DNA?

Accepted Answer

By forming covalent bonds between adjacent thymine bases, creating thymine dimers.

Question 13

A chemical produces a large zone of inhibition on an agar plate. What does this indicate?

Accepted Answer

The chemical is effective at inhibiting bacterial growth, but diffusion rate must also be considered.

Question 14

Which of the following is NOT a method used for identifying microbes?

Accepted Answer

Gram-negative cell wall synthesis

Question 15

Which metabolic test would you use to determine if a bacterium can ferment lactose and produce acid and gas?

Accepted Answer

TSI (Triple Sugar Iron) agar test

Question 16

A water sample is diluted 1:100, and 0.1 mL is plated. If 43 colonies are counted, what is the original sample density in CFU/mL?

Accepted Answer

$$43 \div (0.1 	imes 0.01) = 43,000$$

Question 17

Which of the following best describes a selective medium?

Accepted Answer

A medium that inhibits the growth of some microbes while allowing others to grow.

Question 18

Which metabolic test detects the presence of cytochrome C oxidase?

Accepted Answer

Oxidase test

Question 19

What is the medical relevance of the Gram stain?

Accepted Answer

It helps guide the selection of antibiotics, as some drugs are more effective against Gram-positive or Gram-negative bacteria.

Question 20

Which of the following best defines a pure culture?

Accepted Answer

A culture containing only one bacterial species.

Microbiology Lab Fundamentals: Safety, Microscopy, Staining, Growth, and Identification

Study Guide - Practice Questions