Question 1

Which of the following best describes the purpose of the Kirby-Bauer method in microbiology labs?

Accepted Answer

To assess the susceptibility of bacteria to various antibiotics by measuring zones of inhibition.

Question 2

Which parameter is NOT standardized in the Kirby-Bauer disc diffusion assay?

Accepted Answer

Bacterial species used

Question 3

A bacterium is exposed to an antibiotic and survives, continuing to grow in the presence of the drug. What is the most likely explanation?

Accepted Answer

The bacterium is resistant to the antibiotic.

Question 4

Which of the following best distinguishes a bacteriostatic antibiotic from a bactericidal antibiotic?

Accepted Answer

Bacteriostatic antibiotics inhibit bacterial growth, while bactericidal antibiotics kill bacteria.

Question 5

If two antibiotics are found to be synergistic, what does this imply about their combined therapeutic use?

Accepted Answer

Their combined effect is greater than the sum of their individual effects.

Question 6

What is the definition of Minimum Inhibitory Concentration (MIC) in the context of antibiotic testing?

Accepted Answer

The lowest concentration of antibiotic that prevents visible bacterial growth.

Question 7

During an MIC assay, you observe that bacterial growth is inhibited at $2 \, \mu g/mL$ but not at $1 \, \mu g/mL$. What is the MIC?

Accepted Answer

$2 \, \mu g/mL$

Question 8

Which of the following best describes how to determine the Minimum Bactericidal Concentration (MBC) after performing an MIC test?

Accepted Answer

By subculturing from tubes with no visible growth onto antibiotic-free media and identifying the lowest concentration that results in no colony growth.

Question 9

Which type of DNA mutation is most commonly caused by UV radiation in bacteria?

Accepted Answer

Thymine dimer formation

Question 10

Why are spore-forming bacteria more resistant to UV radiation compared to non-spore-formers?

Accepted Answer

Their spores contain protective layers and DNA repair enzymes.

Question 11

Which of the following is a correct sequence of steps in biofilm formation?

Accepted Answer

Attachment, microcolony formation, maturation, dispersal

Question 12

Which of the following statements best differentiates disinfectants from antiseptics?

Accepted Answer

Disinfectants are used on inanimate objects, while antiseptics are safe for use on living tissues.

Question 13

Which type of horizontal gene transfer involves direct cell-to-cell contact and the transfer of plasmid DNA?

Accepted Answer

Conjugation

Question 14

What is the function of the F factor in bacterial conjugation?

Accepted Answer

It contains genes necessary for pilus formation and DNA transfer.

Question 15

In a transformation experiment using the pGlo plasmid, which ingredient in the agar plate is essential for GFP expression?

Accepted Answer

Arabinose

Question 16

Which of the following best describes a 'persister' cell in a bacterial biofilm?

Accepted Answer

A dormant cell that can survive antibiotic treatment and repopulate the biofilm.

Question 17

Which of the following is a real-life consequence of incorrectly identifying a bacterial pathogen in a clinical setting?

Accepted Answer

The patient may receive ineffective treatment, leading to prolonged illness or complications.

Question 18

During a conjugation experiment, what is a 'transconjugant' cell?

Accepted Answer

A recipient cell that has acquired new genetic material via conjugation.

Question 19

Which of the following best explains why various strains of the same bacterial species might yield different results in staining procedures?

Accepted Answer

Differences in cell wall composition or capsule presence can affect stain uptake.

Question 20

Which of the following is a critical step to ensure a pure bacterial culture during identification procedures?

Accepted Answer

Sterilizing inoculation loops between streaks.

BIO221 Lab Material Review: Core Microbiology Techniques and Concepts

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