WGU D311 Microbiology OA Comprehensive Study Guide 2026 UPDATE
1. Which component is found in the cell walls of Bacteria but not in Archaea?
A. Pseudomurein
B. Peptidoglycan
C. Chitin
D. Cellulose
Answer: B
Rationale: Peptidoglycan is a unique polymer of sugars and amino acids that forms the cell
wall of most bacteria; Archaea use pseudomurein or S-layers.
2. During which phase of the bacterial growth curve are bacteria most sensitive to antibiotics
like penicillin?
A. Lag phase
B. Stationary phase
C. Log phase
D. Death phase
Answer: C
,Rationale: In the log (exponential) phase, bacteria are actively dividing and synthesizing
new cell walls, making them highly susceptible to drugs that target cell wall synthesis.
3. What is the primary function of a bacterial capsule?
A. Protein synthesis
B. Energy storage
C. Protection from phagocytosis
D. Genetic exchange
Answer: C
Rationale: The capsule is a glycocalyx layer that protects the bacterium from the host
immune system by preventing engulfment by white blood cells.
4. Which process involves the transfer of DNA from a donor to a recipient cell via a
bacteriophage?
A. Transformation
B. Transduction
C. Conjugation
D. Translation
Answer: B
Rationale: Transduction is the horizontal gene transfer process where a virus
(bacteriophage) carries bacterial DNA from one cell to another.
, 5. In the Gram stain procedure, what is the role of iodine?
A. Mordant
B. Decolorizer
C. Counterstain
D. Primary stain
Answer: A
Rationale: Iodine acts as a mordant, forming a complex with crystal violet that gets
trapped in the thick peptidoglycan layer of Gram-positive cells.
6. Which organism is characterized by having a cell wall containing high concentrations of
mycolic acid?
A. Staphylococcus aureus
B. Escherichia coli
C. Mycobacterium tuberculosis
D. Bacillus anthracis
Answer: C
Rationale: Mycobacterium species have waxy mycolic acids in their cell walls, requiring an
acid-fast stain rather than a standard Gram stain.
1. Which component is found in the cell walls of Bacteria but not in Archaea?
A. Pseudomurein
B. Peptidoglycan
C. Chitin
D. Cellulose
Answer: B
Rationale: Peptidoglycan is a unique polymer of sugars and amino acids that forms the cell
wall of most bacteria; Archaea use pseudomurein or S-layers.
2. During which phase of the bacterial growth curve are bacteria most sensitive to antibiotics
like penicillin?
A. Lag phase
B. Stationary phase
C. Log phase
D. Death phase
Answer: C
,Rationale: In the log (exponential) phase, bacteria are actively dividing and synthesizing
new cell walls, making them highly susceptible to drugs that target cell wall synthesis.
3. What is the primary function of a bacterial capsule?
A. Protein synthesis
B. Energy storage
C. Protection from phagocytosis
D. Genetic exchange
Answer: C
Rationale: The capsule is a glycocalyx layer that protects the bacterium from the host
immune system by preventing engulfment by white blood cells.
4. Which process involves the transfer of DNA from a donor to a recipient cell via a
bacteriophage?
A. Transformation
B. Transduction
C. Conjugation
D. Translation
Answer: B
Rationale: Transduction is the horizontal gene transfer process where a virus
(bacteriophage) carries bacterial DNA from one cell to another.
, 5. In the Gram stain procedure, what is the role of iodine?
A. Mordant
B. Decolorizer
C. Counterstain
D. Primary stain
Answer: A
Rationale: Iodine acts as a mordant, forming a complex with crystal violet that gets
trapped in the thick peptidoglycan layer of Gram-positive cells.
6. Which organism is characterized by having a cell wall containing high concentrations of
mycolic acid?
A. Staphylococcus aureus
B. Escherichia coli
C. Mycobacterium tuberculosis
D. Bacillus anthracis
Answer: C
Rationale: Mycobacterium species have waxy mycolic acids in their cell walls, requiring an
acid-fast stain rather than a standard Gram stain.
