Question 1

Which of the following body sites is typically considered sterile in a healthy individual?

Accepted Answer

Bloodstream

Question 2

A patient receives an injection of pre-formed antibodies after exposure to rabies. This is an example of which type of immunity?

Accepted Answer

Artificial passive immunity

Question 3

Which of the following best describes the difference between exotoxins and endotoxins?

Accepted Answer

Exotoxins are secreted proteins that can cause specific effects, while endotoxins are lipopolysaccharides released from Gram-negative bacteria upon cell lysis.

Question 4

Which immunoglobulin class is most abundant in serum and is responsible for the secondary antibody response?

Accepted Answer

IgG

Question 5

A researcher isolates a bacterium that uses elemental sulfur as an energy source and CO$$_2 as $$its sole carbon source. Which metabolic class does this organism belong to?

Accepted Answer

Chemolithoautotroph

Question 6

Which of the following is a correct statement about the citric acid cycle (Krebs cycle)?

Accepted Answer

It is directly connected to glycolysis by the conversion of pyruvate to acetyl-CoA.

Question 7

Which of the following is NOT a typical virulence factor?

Accepted Answer

Ribosome

Question 8

Which of the following best describes the mechanism of action of A-B toxins?

Accepted Answer

They consist of two components: one binds to the host cell (B), and the other (A) enters the cell to disrupt cellular function.

Question 9

Which of the following statements about horizontal gene transfer is correct?

Accepted Answer

It can occur via transformation, transduction, and conjugation.

Question 10

A patient presents with muscle spasms and lockjaw after a puncture wound. Which disease is most likely, and what is the causative agent?

Accepted Answer

Tetanus; Clostridium tetani

Question 11

Which of the following best explains why aerobic respiration yields more ATP than anaerobic respiration or fermentation?

Accepted Answer

O$$_2 is a $$stronger electron acceptor, allowing for a greater proton motive force and more ATP synthesis via oxidative phosphorylation.

Question 12

Which of the following is a function of leghemoglobin in rhizobial root nodules?

Accepted Answer

It binds oxygen to protect nitrogenase from inactivation.

Question 13

Which of the following best describes the difference between antigenic drift and antigenic shift in influenza viruses?

Accepted Answer

Antigenic drift involves minor point mutations, while antigenic shift involves major changes due to reassortment of genome segments.

Question 14

Which of the following is a correct statement about the human gastrointestinal (GI) microbiome?

Accepted Answer

It plays a role in digestion, immune function, and can influence diseases such as IBD.

Question 15

Which of the following best describes the difference between metagenomics and metatranscriptomics?

Accepted Answer

Metagenomics analyzes all DNA in a community, while metatranscriptomics analyzes all RNA transcripts.

Question 16

A phylogenetic tree is constructed using 16S rRNA gene sequences. Why is careful sequence alignment critical for this analysis?

Accepted Answer

It ensures that homologous positions are compared, allowing for accurate inference of evolutionary relationships.

Question 17

Which of the following best describes the role of syntrophy in the colon of lean and obese mice?

Accepted Answer

Syntrophy involves interspecies H$$_2$$ transfer, which can affect fermentation processes and energy harvest in the colon.

Question 18

Which of the following is a correct example of a nonliving reservoir of infection?

Accepted Answer

A contaminated water source harboring Vibrio cholerae

Question 19

Which of the following statements about the redox tower is correct?

Accepted Answer

Electron acceptors at the bottom of the tower yield more energy when reduced.

Question 20

Which of the following best explains why obtaining a pure culture is important in microbial ecology?

Accepted Answer

It allows for the study of a single microbial species' physiology and genetics without interference from other organisms.

Comprehensive Study Notes: Microbial Evolution, Metabolism, Pathogenesis, Immunity, and Symbiosis

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