Question 1

Which of the following statements best describes a key difference between Archaea and Bacteria?

Accepted Answer

Archaea have ether-linked membrane lipids, while Bacteria have ester-linked membrane lipids.

Question 2

Which scientist is credited with developing the use of rRNA sequences to classify organisms into the three domains of life?

Accepted Answer

Carl Woese

Question 3

A bacterial cell is observed to have a thick peptidoglycan layer, teichoic acids, and no outer membrane. Which type of cell wall does it possess?

Accepted Answer

Gram-positive

Question 4

Which of the following best explains why RNA is considered a likely candidate for the original genetic material in early life evolution?

Accepted Answer

RNA can act as both a genetic material and a catalyst (ribozyme).

Question 5

Which of the following is a unique feature of Gram-negative bacteria compared to Gram-positive bacteria?

Accepted Answer

Presence of an outer membrane containing lipopolysaccharide (LPS)

Question 6

A patient is infected with a bacterium that can survive in extremely high salt concentrations. Which term best describes this organism, and what is a likely habitat?

Accepted Answer

Halophile; salt lakes such as the Dead Sea

Question 7

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

Accepted Answer

It protects against phagocytosis and desiccation.

Question 8

During DNA replication in bacteria, which enzyme is responsible for synthesizing the majority of the new DNA strand on the leading strand?

Accepted Answer

DNA polymerase III

Question 9

Which of the following best describes the process of group translocation (PTS system) in bacteria?

Accepted Answer

A molecule is transported across the membrane and chemically modified during transport.

Question 10

A bacterium is observed to move toward a chemical attractant. Which process is responsible for this behavior, and what is the underlying mechanism?

Accepted Answer

Chemotaxis; rotation of flagella powered by proton motive force

Question 11

Which of the following statements about horizontal gene transfer (HGT) in bacteria is correct?

Accepted Answer

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

Question 12

Which of the following best explains why microbial growth curves are important in medicine and industry?

Accepted Answer

They help determine the optimal time for antibiotic treatment or harvesting products.

Question 13

Which of the following enzymes protects bacteria from the toxic effects of hydrogen peroxide ($$H_2O_2$$)?

Accepted Answer

Catalase

Question 14

A researcher isolates a microbe from a hot spring with a pH of 9.5. Which term best describes this organism?

Accepted Answer

Alkaliphile

Question 15

Which of the following best describes the function of porins in Gram-negative bacteria?

Accepted Answer

They allow passive diffusion of small molecules across the outer membrane.

Question 16

Which of the following is a correct sequence of events in the formation of a biofilm?

Accepted Answer

Attachment, microcolony formation, production of extracellular polymeric substance, maturation

Question 17

Which of the following best describes the role of N-acyl homoserine lactone (AHL) in bacterial populations?

Accepted Answer

It acts as a signaling molecule in quorum sensing.

Question 18

A bacterium is exposed to a sudden increase in osmotic pressure. Which adaptation is most likely to help it survive?

Accepted Answer

Activation of mechanosensitive channels to release solutes

Question 19

Which of the following statements about the bacterial flagellum is correct?

Accepted Answer

The flagellum is powered by the proton motive force ($$\Delta p) $$across the membrane.

Question 20

Which of the following best describes the function of the periplasmic space in Gram-negative bacteria?

Accepted Answer

It contains enzymes for nutrient acquisition and cell wall synthesis.

Microbiology Study Guide: Domains of Life, Bacterial Cell Structure, and Growth

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