Question 1

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

Accepted Answer

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

Question 2

Which parameter is NOT required for standardization in the Kirby-Bauer disc diffusion assay?

Accepted Answer

The use of nutrient broth instead of Mueller-Hinton agar

Question 3

A bacterium is exposed to an antibiotic and survives but does not grow. Which term best describes the action of the antibiotic?

Accepted Answer

Bacteriostatic

Question 4

If two antibiotics are tested together and the combined zone of inhibition is smaller than either alone, what is the most likely interaction?

Accepted Answer

Antagonistic

Question 5

What does the minimum inhibitory concentration (MIC) of an antibiotic represent?

Accepted Answer

The lowest concentration that prevents visible bacterial growth

Question 6

In an MIC assay, you observe no growth in tubes with antibiotic concentrations of 8, 4, and 2 $\mu$g/mL, but growth in 1 $\mu$g/mL. What is the MIC?

Accepted Answer

$2\ \mu\mathrm{g}/\mathrm{mL}$

Question 7

Which of the following best describes the difference between MIC and MBC?

Accepted Answer

MIC is the lowest concentration that inhibits growth; MBC is the lowest that kills bacteria.

Question 8

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

Accepted Answer

Thymine dimer formation

Question 9

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

Accepted Answer

Spores have protective layers and low metabolic activity, making them less susceptible to DNA damage.

Question 10

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

Accepted Answer

Attachment, irreversible adhesion, microcolony formation, maturation, dispersal

Question 11

Which of the following best distinguishes a disinfectant from an antiseptic?

Accepted Answer

Disinfectants are used on inanimate objects; antiseptics are used on living tissue.

Question 12

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

Accepted Answer

Conjugation

Question 13

What is the F factor in bacterial conjugation?

Accepted Answer

A plasmid that carries genes for pilus formation and DNA transfer

Question 14

In a transformation experiment, what is the primary purpose of making cells 'competent'?

Accepted Answer

To enable cells to take up foreign DNA from their environment

Question 15

Which ingredient in the modified LB agar plates is essential for activating GFP expression in pGlo-transformed cells?

Accepted Answer

Arabinose

Question 16

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

Accepted Answer

The patient may receive ineffective treatment, leading to worsening infection.

Question 17

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

Accepted Answer

A dormant cell that survives antibiotic treatment and can repopulate the biofilm

Question 18

Which type of DNA transfer is most likely to occur within a biofilm, contributing to antibiotic resistance?

Accepted Answer

Horizontal gene transfer

Question 19

A student streaks a plate to isolate a pure culture but observes colonies of different morphologies. What is the most likely explanation?

Accepted Answer

The culture was contaminated with more than one organism.

Question 20

Which of the following best defines a scientific hypothesis?

Accepted Answer

A testable explanation for an observation or scientific problem

BIO221 Lab Material Review: Antimicrobial Methods, Biofilms, and Bacterial Genetics

Study Guide - Practice Questions