Question 1

Which experiment provided the most convincing evidence against the theory of spontaneous generation by demonstrating that microorganisms do not grow in broth unless exposed to a source of contamination?

Accepted Answer

Pasteur's swan neck flask experiment

Question 2

Which of the following statements best describes a key difference between prokaryotic and eukaryotic genetic organization?

Accepted Answer

Prokaryotes have a single circular chromosome in the nucleoid region, while eukaryotes have multiple linear chromosomes in a membrane-bound nucleus

Question 3

A patient is diagnosed with a Gram-negative bacterial infection. Which component of the bacterial cell envelope is most likely responsible for triggering a strong inflammatory response via TLR4 activation?

Accepted Answer

Lipid A portion of lipopolysaccharide (LPS)

Question 4

Which of the following best explains why SAR11 bacteria are considered ecologically significant in ocean environments?

Accepted Answer

Their abundance, ubiquity, and efficient metabolism make them major contributors to global carbon cycling

Question 5

Which of the following transport systems in bacteria involves the chemical modification of the substrate during its passage across the membrane, often using phosphoenolpyruvate (PEP) as an energy source?

Accepted Answer

Group translocation (phosphotransferase system)

Question 6

A researcher is studying a microorganism with the following characteristics: ether-linked isoprenoid chains in its membrane, no peptidoglycan, and an S-layer as the main cell wall component. To which domain does this organism most likely belong?

Accepted Answer

Archaea

Question 7

Which of the following best describes the function of teichoic acids in Gram-positive bacteria?

Accepted Answer

They attract cations, increasing cell wall rigidity and water retention

Question 8

A bacterial cell is observed to move in a corkscrew-like fashion through viscous media. Which structure is most likely responsible for this type of motility?

Accepted Answer

Endoflagella located in the periplasmic space

Question 9

Which of the following statements about endospores is FALSE?

Accepted Answer

Endospores are formed in response to nutrient abundance

Question 10

During Gram staining, which structural difference between Gram-positive and Gram-negative bacteria is primarily responsible for the difference in staining outcome?

Accepted Answer

Thickness of the peptidoglycan layer

Question 11

A bacterium is found to use hydrogen sulfide ($$\mathrm{H_2S}) as an $$energy source and carbon dioxide ($$\mathrm{CO_2$}) as a $$carbon source. Which nutritional category does it belong to?

Accepted Answer

Chemolithoautotroph

Question 12

Which of the following best explains why rRNA gene sequences are used to determine evolutionary relationships among microorganisms?

Accepted Answer

rRNA genes are universally present, functionally conserved, and change slowly over time

Question 13

A Gram-negative bacterium is able to survive in the presence of certain antibiotics due to the presence of porins. What is the primary function of porins in the outer membrane?

Accepted Answer

They form channels that allow passive diffusion of small molecules

Question 14

Which of the following best describes the mechanism by which the bacterial flagellar motor is powered?

Accepted Answer

Proton motive force ($$\Delta p) $$generated by the flow of protons through Mot proteins

Question 15

A scientist observes a bacterial cell with a tuft of flagella at both poles. What is the correct term for this flagellar arrangement?

Accepted Answer

Amphilophotrichous

Question 16

Which of the following statements about the bacterial phosphotransferase system (PTS) is TRUE?

Accepted Answer

It phosphorylates the sugar substrate during transport using phosphoenolpyruvate (PEP) as the phosphate donor

Question 17

Which of the following is a function of small acid-soluble spore proteins (SASPs) in bacterial endospores?

Accepted Answer

They bind to DNA, protecting it from UV damage and converting it from B-DNA to A-DNA

Question 18

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

Accepted Answer

It contains hydrolytic enzymes, binding proteins, and chemoreceptors

Question 19

A bacterial cell is observed to move by extending and retracting appendages from one pole, pulling itself along a surface. Which structure and energy source are responsible for this movement?

Accepted Answer

Type IV pili powered by ATP hydrolysis

Question 20

Which of the following best explains why Mycoplasma species are resistant to penicillin?

Accepted Answer

They lack a cell wall and therefore do not have peptidoglycan

Microbiology Exam 1 Study Guide: Foundations, Cell Structure, and Metabolism

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