Q: A bacterial culture is diluted in a series of tenfold dilutions. If 0.1 mL of the $$10^{-4}$$ dilution yields 50 colonies on a plate, what is the original concentration of bacteria per mL?

$$50 \times 10^4$ \times 10 = 5 \times 10^6$ CFU/mL

Question 1

Which of the following best describes the main purpose of the MBY161 Microbiology module?

Accepted Answer

To introduce students to the diversity, structure, and function of microorganisms and their impact on human life and the environment.

Question 2

Which scientist’s work directly disproved the theory of spontaneous generation?

Accepted Answer

Louis Pasteur

Question 3

Which of the following is NOT a distinguishing characteristic of prokaryotic cells?

Accepted Answer

Presence of a nucleus

Question 4

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

Accepted Answer

$$10 	imes 40 = 400$$

Question 5

Which of the following best explains why Gram staining is a critical technique in microbiology?

Accepted Answer

It distinguishes bacteria based on differences in their cell wall structure.

Question 6

Which of the following is a correct sequence of steps in the Gram stain procedure?

Accepted Answer

Crystal violet, iodine, alcohol, safranin

Question 7

Which of the following statements about biofilms is TRUE?

Accepted Answer

Biofilms are communities of microorganisms attached to a surface and encased in extracellular polymeric substances.

Question 8

Which physical method is most effective for sterilizing heat-sensitive solutions?

Accepted Answer

Filtration

Question 9

A bacterial culture is diluted in a series of tenfold dilutions. If 0.1 mL of the $$10^{-4}$$ dilution yields 50 colonies on a plate, what is the original concentration of bacteria per mL?

Accepted Answer

$$50 	imes 10^4$ 	imes 10 = 5 	imes 10^6$ CFU/mL

Question 10

Which of the following best describes the mechanism of action of penicillin?

Accepted Answer

Inhibits cell wall synthesis by blocking peptidoglycan cross-linking

Question 11

Which of the following is a reason why viral, fungal, and protozoan infections are generally harder to treat than bacterial infections?

Accepted Answer

Their cells are more similar to human cells, making selective toxicity difficult.

Question 12

Which of the following is an example of a selective medium?

Accepted Answer

Agar containing antibiotics to inhibit unwanted bacteria

Question 13

Which of the following statements about Koch’s postulates is correct?

Accepted Answer

They are used to prove that a specific microorganism causes a specific disease.

Question 14

Which of the following best describes the difference between exotoxins and endotoxins?

Accepted Answer

Exotoxins are proteins secreted by bacteria; endotoxins are lipopolysaccharides found in the outer membrane of Gram-negative bacteria.

Question 15

Which of the following is a defining feature of viruses?

Accepted Answer

They are acellular and require a host cell to replicate.

Question 16

Which of the following is a correct statement about the three domains of life?

Accepted Answer

Bacteria and Archaea are both prokaryotic, while Eukarya includes all eukaryotic organisms.

Question 17

Which of the following best explains why mycoses are often chronic diseases?

Accepted Answer

Fungi grow slowly and resist immune defenses.

Question 18

Which of the following is a correct definition of a biofilm?

Accepted Answer

A complex community of microorganisms attached to a surface and encased in a self-produced matrix.

Question 19

Which of the following best describes the function of siderophores in bacterial pathogenicity?

Accepted Answer

They help bacteria acquire iron from the host.

Microbiology MBY161: Study Guide and Syllabus Overview

Study Guide - Practice Questions

Study Guide - Flashcards