Question 1

Which of the following statements best explains why viruses are classified as acellular organisms?

Accepted Answer

Viruses do not carry out metabolism and only replicate within host cells.

Question 2

Pasteurization is a process used to prevent spoilage by microbes. Which of the following best describes the principle behind pasteurization?

Accepted Answer

Brief application of high heat to kill spoiling microbes, followed by addition of yeast.

Question 3

Which of the following is NOT a criterion in Koch's postulates for identifying the microbial cause of an infectious disease?

Accepted Answer

The microbe must be able to survive outside the host for at least 24 hours.

Question 4

Which bacterial structure is primarily responsible for motility and is composed of a filament, hook, and basal body?

Accepted Answer

Flagellum

Question 5

A Gram-negative bacterium is exposed to lysozyme. Which component of its cell envelope is most directly affected?

Accepted Answer

Peptidoglycan layer

Question 6

Which equation correctly describes the relationship between the number of generations ($$n$$), total time ($$t$$), and generation time ($$g) in $$bacterial growth?

Accepted Answer

$$g = \frac{t}{n}$$

Question 7

During aerobic respiration in bacteria, which of the following is the correct overall equation for the catabolism of glucose?

Accepted Answer

$$C_6H_{12}O_6$ + 6 O_2$ \rightarrow 6 CO_2$ + 6 H_2O$$

Question 8

Which of the following statements about the Lac operon in E. coli is correct?

Accepted Answer

The Lac operon is repressed when lactose is absent and activated when lactose is present and glucose is absent.

Question 9

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

Accepted Answer

They protect bacteria from phagocytosis and desiccation.

Question 10

A bacterium is placed in an environment with no terminal electron acceptor. Which metabolic pathway will it most likely use to generate ATP?

Accepted Answer

Fermentation

Question 11

Which of the following is a correct description of an exergonic reaction in bacterial metabolism?

Accepted Answer

It releases energy and has a negative $$\Delta G^\circ'$$ value.

Question 12

Which gene is commonly used for phylotyping and constructing phylogenetic trees in prokaryotes?

Accepted Answer

16S rRNA gene

Question 13

Which of the following best describes horizontal gene transfer in bacteria?

Accepted Answer

Exchange of genes between unrelated bacteria, increasing genetic diversity.

Question 14

Which of the following mechanisms is used by bacteria to destroy non-self DNA, such as bacteriophage DNA?

Accepted Answer

Restriction-modification system

Question 15

In a two-component signal transduction system, which amino acid residues are involved in the transfer of the phosphoryl group?

Accepted Answer

Histidine and aspartate

Question 16

Which of the following is a major virulence factor that enables Staphylococcus aureus to evade host immune responses?

Accepted Answer

Coagulase

Question 17

Which of the following equations represents the specific growth rate ($$k) in $$bacterial exponential growth?

Accepted Answer

$$\frac{dN}{dt} = kN$$

Question 18

Which of the following best explains why penicillin is selectively toxic to bacteria but not to human cells?

Accepted Answer

Penicillin targets the bacterial cell wall, which is absent in human cells.

Question 19

Which of the following is a characteristic of superantigen toxins?

Accepted Answer

They activate a large proportion of T cells, causing systemic inflammation.

Question 20

A patient is infected with a strain of E. coli that acquired a pathogenicity island via horizontal gene transfer. Which of the following is a likely consequence?

Accepted Answer

The strain will gain new virulence factors and may cause disease.

Comprehensive Study Notes: Foundations of Microbiology

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