Question 1

Which scientist is credited with disproving the theory of spontaneous generation through his famous swan-neck flask experiment, and what was the key conclusion from this experiment?

Accepted Answer

Louis Pasteur; concluded that microorganisms do not arise spontaneously but come from other microorganisms.

Question 2

A patient presents with symptoms of Creutzfeldt-Jakob disease. Which infectious agent is responsible, and what is the mechanism of infection?

Accepted Answer

Prion; infection occurs via misfolded protein inducing misfolding in normal PrP proteins.

Question 3

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

Accepted Answer

Gram-positive cell walls contain a thick layer of peptidoglycan and teichoic acids, while Gram-negative cell walls have a thin peptidoglycan layer and an outer membrane containing lipopolysaccharide (LPS).

Question 4

A microbiologist is culturing bacteria using a streak plate method. What is the primary purpose of this technique?

Accepted Answer

To obtain a pure culture by isolating individual colonies from a mixed population.

Question 5

Which equation correctly calculates the total number of bacterial cells after $$n$$ generations, starting with a single cell, assuming binary fission?

Accepted Answer

$$N = 2^n$$

Question 6

During the log phase of bacterial growth, which of the following statements is TRUE?

Accepted Answer

Cells are dividing at their maximum rate, resulting in exponential population growth.

Question 7

Which enzyme protects bacteria from the toxic effects of superoxide radicals ($$O_2$$^-$$)?

Accepted Answer

Superoxide dismutase

Question 8

A facultative anaerobe is grown in Fluid Thioglycollate Medium (FTM). Where would you expect most growth to occur, and why?

Accepted Answer

Throughout the tube, but more at the top, because it can use oxygen for aerobic respiration but can also grow anaerobically.

Question 9

Which of the following is a correct example of binomial nomenclature for a bacterium?

Accepted Answer

Escherichia coli

Question 10

Which bacterial structure is primarily responsible for motility, and what is its basic mechanism?

Accepted Answer

Flagellum; rotation of a helical filament powered by a proton gradient.

Question 11

Which of the following best describes the function of bacterial endospores?

Accepted Answer

To allow bacteria to survive harsh environmental conditions such as heat, desiccation, and chemicals.

Question 12

Which of the following is NOT a characteristic of viruses?

Accepted Answer

They contain both DNA and RNA in the same particle.

Question 13

Which scientist developed a set of criteria to establish a causal relationship between a microbe and a disease, and what are these criteria called?

Accepted Answer

Robert Koch; Koch's Postulates

Question 14

Which of the following best describes the process of quorum sensing in biofilms?

Accepted Answer

Bacteria communicate via chemical signals to coordinate gene expression and behavior once a critical population density is reached.

Question 15

Which of the following is TRUE regarding the lytic cycle of a bacteriophage?

Accepted Answer

The virus immediately replicates, assembles, and lyses the host cell to release new virions.

Question 16

Which of the following is a major function of the bacterial cell wall?

Accepted Answer

To provide structural support and prevent osmotic lysis.

Question 17

Which of the following best describes an opportunistic pathogen?

Accepted Answer

A microorganism that causes disease only when the host's defenses are compromised.

Question 18

Which of the following is TRUE about the nutritional requirements for microbial growth?

Accepted Answer

Microbes require a variety of nutrients, including carbon, nitrogen, phosphorus, and trace elements, for cellular processes such as energy production and biosynthesis.

Question 19

Which of the following is a correct trophic classification for a microbe that uses organic carbon for energy and carbon source?

Accepted Answer

Chemoheterotroph

Question 20

A virus with a +ssRNA genome infects a host cell. Which statement best describes its replication strategy?

Accepted Answer

The +ssRNA is directly translated into viral proteins by the host ribosomes.

Microbiology Exam 1 Review: History, Cell Structure, Growth, Classification, and Infectious Agents

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