Question 1

Which of the following best describes the difference between bacteriostatic and bactericidal antibiotics?

Accepted Answer

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

Question 2

A physician prescribes an antibiotic to treat a viral infection. What is the most likely consequence of this action?

Accepted Answer

Antibiotic resistance may develop due to misuse of the antibiotic.

Question 3

Which equation correctly represents the calculation for the dilution factor when preparing serial dilutions for MIC testing?

Accepted Answer

$$DF = \frac{V_{sample}}{V_{sample} + V_{diluent}}$$

Question 4

If the Minimum Inhibitory Concentration (MIC) of an antibiotic is 0.5 mg/mL and the Minimum Bactericidal Concentration (MBC) is 2 mg/mL, what does this indicate about the antibiotic's action?

Accepted Answer

The antibiotic is bacteriostatic at concentrations close to the MIC.

Question 5

In the Kirby-Bauer disk diffusion method, which factor does NOT affect the size of the zone of inhibition?

Accepted Answer

Ability to distinguish between bacteriostatic and bactericidal drugs

Question 6

Which of the following is TRUE regarding biofilm formation?

Accepted Answer

Biofilms are made up of polysaccharides, proteins, lipids, and DNA.

Question 7

During the biofilm formation process, which stage involves the production of extracellular polymeric substances (EPS) that help cells stick to a surface?

Accepted Answer

EPS matrix formation

Question 8

Which chemical process converts cytosine to uracil in DNA, potentially leading to mutations?

Accepted Answer

Deamination

Question 9

Which repair mechanism uses DNA glycosylase to remove damaged bases and DNA polymerase to fill the gap?

Accepted Answer

Base Excision Repair (BER)

Question 10

Why are wavelengths below 400 nm considered dangerous for living organisms?

Accepted Answer

They can cause DNA damage and mutations.

Question 11

Which of the following best explains how UV radiation kills bacteria?

Accepted Answer

By creating thymine dimers that block DNA replication.

Question 12

A bacterial cell exposed to UV light forms a thymine dimer. Which repair mechanism uses visible light to activate an enzyme that breaks the dimer?

Accepted Answer

Photoactivation (Photoreactivation)

Question 13

Which structure in bacterial endospores is responsible for high resistance to UV radiation?

Accepted Answer

Small acid-soluble proteins (SASP)

Question 14

What is the primary function of the spore coat in bacterial endospores?

Accepted Answer

To provide enzymatic and chemical resistance

Question 15

Which of the following statements about bacterial conjugation is correct?

Accepted Answer

Conjugation requires direct cell-to-cell contact and transfer of plasmid DNA.

Question 16

A bacterium with the F'128 plasmid can ferment lactose and is resistant to chloramphenicol. Which gene is responsible for antibiotic resistance?

Accepted Answer

Cat

Question 17

Which process allows bacteria to acquire DNA from their surroundings, and can be enhanced by chemical treatment?

Accepted Answer

Transformation

Question 18

In a transformation experiment, why do only the colonies on the plate with arabinose glow under UV light?

Accepted Answer

Arabinose activates the promoter controlling the GFP gene.

Question 19

Which of the following is NOT a condition that triggers endospore formation in bacteria?

Accepted Answer

Abundant nutrients and optimal growth conditions

Question 20

A bacterial cell repairs UV-induced DNA damage using the cell's energy in the form of ATP and an enzyme complex that removes and replaces damaged DNA. Which repair mechanism is this?

Accepted Answer

Nucleotide Excision Repair (NER)

Microbiology Lab Practical 2 Study Guide: Antibiotic Resistance, Biofilms, DNA Damage & Repair, and Genetic Exchange

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