WGU D311 OA Microbiology (2026/2027) Exam –
(2 Set Exams) Actual Questions & Study Guide
(Guarantee Pass)
250 QUESTIONS
TABLE OF CONTENTS
# TOPIC
1 Microbial Structure & Function
2 Microbial Growth & Metabolism
3 Microbial Genetics
4 Control of Microorganisms
5 Immunology
6 Host-Pathogen Interactions
7 Bacteriology
8 Virology
9 Mycology & Parasitology
10 Laboratory Diagnosis
11 Epidemiology & Infection Control
, SET 1
Q1
Which of the following is a characteristic of prokaryotic cells?
A) Presence of a nucleus
B) Presence of a cell wall containing peptidoglycan CORRECT
C) Presence of membrane-bound organelles
D) Presence of mitochondria
Rationale
Prokaryotes (bacteria) have peptidoglycan cell walls; they lack a nucleus and membrane-bound
organelles.
Q2
Gram-positive bacteria appear purple after Gram staining because:
A) They have an outer membrane
B) They retain crystal violet-iodine complex due to thick peptidoglycan CORRECT
C) They have a thin peptidoglycan layer
D) They are counterstained with safranin
Rationale
The thick peptidoglycan layer in Gram-positive cells traps the crystal violet-iodine complex, appearing
purple.
Q3
Which structure allows bacteria to adhere to surfaces and to each other?
A) Flagella
B) Pili (fimbriae) CORRECT
C) Capsule
2
,D) Endospore
Rationale
Pili mediate attachment to surfaces and are involved in conjugation (sex pilus).
Q4
The primary function of the bacterial capsule is to:
A) Provide motility
B) Protect against phagocytosis CORRECT
C) Store nutrients
D) Facilitate conjugation
Rationale
Capsules are polysaccharide layers that inhibit phagocytosis and enhance virulence.
Q5
Which of the following is a distinguishing feature of Gram-negative bacteria?
A) Thick peptidoglycan layer
B) Outer membrane containing lipopolysaccharide (LPS) CORRECT
C) Teichoic acids
D) No cell wall
Rationale
Gram-negative bacteria have an outer membrane with LPS (endotoxin), which is absent in Gram-positive
bacteria.
3
, Q6
Endospores are produced by which genera of bacteria?
A) Escherichia and Salmonella
B) Bacillus and Clostridium CORRECT
C) Staphylococcus and Streptococcus
D) Mycobacterium and Nocardia
Rationale
Endospores are dormant, highly resistant structures formed by Bacillus and Clostridium species.
Q7
The bacterial growth curve phase where cells are metabolically active but not dividing is:
A) Lag phase CORRECT
B) Lag phase
C) Log phase
D) Stationary phase
Rationale
During lag phase, cells adapt to new conditions and synthesize enzymes, but no increase in cell number
occurs.
Q8
Which of the following is a obligate intracellular parasite?
A) Escherichia coli
B) Chlamydia trachomatis CORRECT
C) Staphylococcus aureus
D) Pseudomonas aeruginosa
4
(2 Set Exams) Actual Questions & Study Guide
(Guarantee Pass)
250 QUESTIONS
TABLE OF CONTENTS
# TOPIC
1 Microbial Structure & Function
2 Microbial Growth & Metabolism
3 Microbial Genetics
4 Control of Microorganisms
5 Immunology
6 Host-Pathogen Interactions
7 Bacteriology
8 Virology
9 Mycology & Parasitology
10 Laboratory Diagnosis
11 Epidemiology & Infection Control
, SET 1
Q1
Which of the following is a characteristic of prokaryotic cells?
A) Presence of a nucleus
B) Presence of a cell wall containing peptidoglycan CORRECT
C) Presence of membrane-bound organelles
D) Presence of mitochondria
Rationale
Prokaryotes (bacteria) have peptidoglycan cell walls; they lack a nucleus and membrane-bound
organelles.
Q2
Gram-positive bacteria appear purple after Gram staining because:
A) They have an outer membrane
B) They retain crystal violet-iodine complex due to thick peptidoglycan CORRECT
C) They have a thin peptidoglycan layer
D) They are counterstained with safranin
Rationale
The thick peptidoglycan layer in Gram-positive cells traps the crystal violet-iodine complex, appearing
purple.
Q3
Which structure allows bacteria to adhere to surfaces and to each other?
A) Flagella
B) Pili (fimbriae) CORRECT
C) Capsule
2
,D) Endospore
Rationale
Pili mediate attachment to surfaces and are involved in conjugation (sex pilus).
Q4
The primary function of the bacterial capsule is to:
A) Provide motility
B) Protect against phagocytosis CORRECT
C) Store nutrients
D) Facilitate conjugation
Rationale
Capsules are polysaccharide layers that inhibit phagocytosis and enhance virulence.
Q5
Which of the following is a distinguishing feature of Gram-negative bacteria?
A) Thick peptidoglycan layer
B) Outer membrane containing lipopolysaccharide (LPS) CORRECT
C) Teichoic acids
D) No cell wall
Rationale
Gram-negative bacteria have an outer membrane with LPS (endotoxin), which is absent in Gram-positive
bacteria.
3
, Q6
Endospores are produced by which genera of bacteria?
A) Escherichia and Salmonella
B) Bacillus and Clostridium CORRECT
C) Staphylococcus and Streptococcus
D) Mycobacterium and Nocardia
Rationale
Endospores are dormant, highly resistant structures formed by Bacillus and Clostridium species.
Q7
The bacterial growth curve phase where cells are metabolically active but not dividing is:
A) Lag phase CORRECT
B) Lag phase
C) Log phase
D) Stationary phase
Rationale
During lag phase, cells adapt to new conditions and synthesize enzymes, but no increase in cell number
occurs.
Q8
Which of the following is a obligate intracellular parasite?
A) Escherichia coli
B) Chlamydia trachomatis CORRECT
C) Staphylococcus aureus
D) Pseudomonas aeruginosa
4
