Question 1

Which of the following statements best explains why Gram-negative bacteria are generally more resistant to certain antibiotics than Gram-positive bacteria?

Accepted Answer

Gram-negative bacteria possess an outer membrane containing porin proteins that can restrict the entry of antibiotics.

Question 2

A patient presents with a wound infection that is not responding to boiling water or common disinfectants. Laboratory analysis reveals the presence of endospores. Which genus is most likely responsible for this infection?

Accepted Answer

Bacillus

Question 3

Which of the following best describes the function of the bacterial glycocalyx when it forms a capsule?

Accepted Answer

It protects the bacterium from phagocytosis by white blood cells.

Question 4

A bacterium is observed to move toward a light source. This behavior is best described as:

Accepted Answer

Positive phototaxis

Question 5

Which of the following structures is found only in Gram-negative bacteria and is involved in the transfer of genetic material during conjugation?

Accepted Answer

Pili

Question 6

A scientist isolates a microorganism from a hot spring that thrives at 100°C and cannot grow at 50°C. This organism is most likely a(n):

Accepted Answer

Hyperthermophile

Question 7

Which of the following is a unique feature of archaeal cell membranes compared to bacterial cell membranes?

Accepted Answer

Unique membrane lipids not found in bacteria

Question 8

A bacterial cell is observed to have a thick, homogenous sheath of peptidoglycan and teichoic acids. Which Gram reaction will it show and why?

Accepted Answer

Gram-positive, due to the thick peptidoglycan layer

Question 9

Which of the following best describes the role of porin proteins in Gram-negative bacteria?

Accepted Answer

They allow selective entry of small molecules through the outer membrane.

Question 10

A bacterium is found to lack a cell wall and displays extreme variability in shape. Which genus does it most likely belong to?

Accepted Answer

Mycoplasma

Question 11

Which of the following is a medically significant consequence of bacterial biofilm formation on artificial devices?

Accepted Answer

Biofilms protect bacteria from host immune responses and disinfectants.

Question 12

Which of the following best explains why endospores are a concern in the food-canning industry?

Accepted Answer

Endospores can survive standard sterilization and contaminate food.

Question 13

Which of the following is a function of teichoic acids in Gram-positive bacteria?

Accepted Answer

They contribute to cell wall maintenance and enlargement during cell division.

Question 14

A bacterium is observed to move in a smooth, linear direction toward a chemical attractant. Which flagellar movement is responsible for this behavior?

Accepted Answer

Counterclockwise movement (run)

Question 15

Which of the following best describes the composition and function of peptidoglycan in bacterial cell walls?

Accepted Answer

A macromolecule of glycan chains cross-linked with short peptide fragments, providing structural support

Question 16

Which of the following is true regarding the ribosomes of bacteria?

Accepted Answer

They are 70S, composed of 50S and 30S subunits.

Question 17

Which of the following best describes the role of lipopolysaccharide (LPS) in Gram-negative bacteria?

Accepted Answer

It functions as an endotoxin and stimulates fever and shock reactions.

Question 18

A bacterium isolated from a salt lake requires high concentrations of NaCl for growth and uses a red pigment to synthesize ATP in the presence of light. This organism is best classified as a(n):

Accepted Answer

Extreme halophile

Question 19

Which of the following is a correct statement about the cytoskeleton in bacteria?

Accepted Answer

It consists of long polymers of proteins similar to actin and contributes to cell shape.

Question 20

A clinical isolate is identified as a facultative anaerobic rod that causes typhoid fever. To which family does this bacterium most likely belong?

Accepted Answer

Enterobacteriaceae

Bacteria and Archaea: Structure, Function, and Classification

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