Question 1

Which of the following best explains why Pasteur’s swan-neck flask experiment was pivotal in disproving spontaneous generation?

Accepted Answer

It showed that sterilized broth remained free of microbial growth unless exposed to particles from the air, supporting biogenesis.

Question 2

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

Accepted Answer

They provide a systematic method to link a specific microorganism to a specific disease.

Question 3

A unicellular osmotrophic bacterium is found to be extremely small. What is the primary advantage of this small size for its mode of nutrition?

Accepted Answer

It allows for a higher surface area-to-volume ratio, enhancing nutrient uptake by diffusion.

Question 4

Which of the following best describes the difference between Gram-positive and Gram-negative bacterial cell walls?

Accepted Answer

Gram-positive bacteria have a thick peptidoglycan layer and lack an outer membrane, while Gram-negative bacteria have a thin peptidoglycan layer and possess an outer membrane.

Question 5

Which of the following equations correctly expresses exponential population growth in bacteria, where $$N is $$the final cell number, $$N_0 is $$the initial cell number, and $$n is $$the number of generations?

Accepted Answer

$$N = N_0$ 2^n$$

Question 6

A bacterium is placed in an environment with no oxygen but continues to grow by using nitrate as a terminal electron acceptor. Which metabolic pathway is it most likely using?

Accepted Answer

Anaerobic respiration

Question 7

Which of the following best describes the function of the proton motive force (PMF) in prokaryotic cells?

Accepted Answer

It drives ATP synthesis, solute transport, and flagellar rotation.

Question 8

A culture of bacteria is exposed to a chemical that kills cells by lysing them. This chemical is best described as:

Accepted Answer

Bacteriolytic

Question 9

Which of the following statements about viruses is TRUE?

Accepted Answer

Viruses can only replicate inside a host cell.

Question 10

A researcher is studying a virus that integrates its genome into the host’s DNA and remains dormant for several generations before becoming active. This type of viral life cycle is called:

Accepted Answer

Lysogenic cycle

Question 11

Which of the following best describes the function of an operon in prokaryotic gene regulation?

Accepted Answer

A group of genes transcribed together under the control of a single promoter.

Question 12

A bacterial population is grown in a medium containing both glucose and lactose. The cells first consume glucose, then after a lag, begin to metabolize lactose. This phenomenon is known as:

Accepted Answer

Diauxic growth

Question 13

Which of the following is a correct description of a selectable mutation?

Accepted Answer

A mutation that can be detected because it confers a growth advantage or disadvantage under certain conditions.

Question 14

Which of the following best explains why single point mutations can result in silent, missense, or nonsense mutations?

Accepted Answer

Because the genetic code is degenerate and a single nucleotide change can have different effects on the encoded amino acid.

Question 15

Which of the following is a function of two-component regulatory systems in bacteria?

Accepted Answer

They allow bacteria to sense and respond to environmental changes via a sensor kinase and a response regulator.

Question 16

A bacterial cell is exposed to UV light, resulting in DNA damage. Which process is most likely to repair the damage?

Accepted Answer

DNA repair mechanisms such as nucleotide excision repair

Question 17

Which of the following best describes the difference between transformation, transduction, and conjugation in bacteria?

Accepted Answer

Transformation involves uptake of free DNA, transduction involves bacteriophages, and conjugation involves direct cell-to-cell contact.

Question 18

Which of the following is a key difference between bacterial and animal viruses?

Accepted Answer

Bacterial viruses inject their genome into the host, while animal viruses often enter the host cell via endocytosis or membrane fusion.

Question 19

A researcher is using a chemostat to grow a bacterial culture. Which of the following parameters does the chemostat directly control to maintain continuous growth?

Accepted Answer

Nutrient concentration and dilution rate

Question 20

Which of the following best describes the role of ATP in microbial metabolism?

Accepted Answer

ATP acts as the primary energy currency, storing and transferring energy for cellular processes.

Microbiology Study Guide: Key Concepts for MAR 301 Mid-Term I

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