ESTUDYR
MT AAB STUDY GUIDE 2025 UPDATED EXAM WITH MOST
TESTED QUESTIONS AND ANSWERS | GRADED A+ | ASSURED
SUCCESS WITH DETAILED RATIONALES
1. What term describes the morphology of organisms that vary in shape and size?
a. Monomorphic
b. Pleomorphic
c. Diploid
d. Polymorphic
Answer: b. Pleomorphic
Rationale: Pleomorphic organisms can vary in shape and size, as seen in coccobacilli. This
adaptability is an identifying feature of certain bacteria.
2. Which of the following describes a "grape-like cluster" bacterial arrangement?
a. Diplococci
b. Streptococci
c. Staphylococci
d. Tetrads
Answer: c. Staphylococci
Rationale: Staphylococci bacteria arrange in grape-like clusters, which is a distinguishing
feature under a microscope.
3. Capsules are the basis of which of the following tests?
a. Gram staining
b. Serotyping
c. Acid-fast staining
d. Hemolysis tests
Answer: b. Serotyping
Rationale: Capsules are antigenic and play a role in serotyping, which aids in identifying
pathogens like Streptococcus pneumoniae and Klebsiella pneumoniae.
,ESTUDYR
4. A mucoid colony on blood agar medium indicates which characteristic?
a. Lack of capsule
b. Presence of a capsule
c. Flagella production
d. Lack of growth
Answer: b. Presence of a capsule
Rationale: A capsule is often responsible for the mucoid appearance of colonies, aiding in
bacterial virulence and survival.
5. What are dark staining granules in bacteria referred to as?
a. Metachromatic granules
b. Inclusion bodies
c. Peptidoglycan clusters
d. Sporulating granules
Answer: a. Metachromatic granules
Rationale: Metachromatic granules have an affinity for basic dyes and are stained with
methods such as Albert or Neisser stains.
6. Which of the following organisms are non-motile?
a. Shigella and Klebsiella
b. Salmonella and Shigella
c. Klebsiella and Enterobacter
d. Bacillus anthracis and Shigella
Answer: a. Shigella and Klebsiella
Rationale: Both Shigella and Klebsiella are non-motile, unlike their motile counterparts like
Salmonella.
7. In which phase of the bacterial growth cycle does growth cease due to nutrient exhaustion
or toxic product accumulation?
,ESTUDYR
a. Lag phase
b. Log phase
c. Stationary phase
d. Death phase
Answer: c. Stationary phase
Rationale: The stationary phase is marked by a plateau in growth when the bacterial
environment becomes hostile.
8. Which genera of bacteria are known to form spores?
a. Escherichia and Proteus
b. Clostridium and Bacillus
c. Klebsiella and Shigella
d. Pseudomonas and Enterococcus
Answer: b. Clostridium and Bacillus
Rationale: Clostridium and Bacillus form highly resistant endospores that enable survival in
extreme conditions.
9. What term is used for bacteria that grow in the absence of atmospheric oxygen and obtain
oxygen from oxygen-containing compounds?
a. Aerobes
b. Anaerobes
c. Microaerophiles
d. Facultative anaerobes
Answer: b. Anaerobes
Rationale: Anaerobes thrive in oxygen-deprived environments, unlike aerobes, which depend
on free oxygen.
10. Which bacterial arrangement describes a "group of four" cells?
a. Diplococci
b. Tetrads
, ESTUDYR
c. Palisades
d. Chains
Answer: b. Tetrads
Rationale: Tetrads refer to bacteria that organize in groups of four, a notable feature of
Peptococcus.
11. Which staining method is used to observe bacterial capsules?
a. Gram stain
b. India ink negative stain
c. Acid-fast stain
d. Endospore stain
Answer: b. India ink negative stain
Rationale: Capsules are visualized using the India ink negative staining technique, highlighting
the capsule against a dark background.
12. Which bacteria are identified by metachromatic granules?
a. Mycobacterium tuberculosis
b. Corynebacterium diphtheriae
c. Klebsiella pneumoniae
d. Staphylococcus aureus
Answer: b. Corynebacterium diphtheriae
Rationale: Metachromatic granules are characteristic of Corynebacterium diphtheriae and are
visualized with specific dyes.
13. Which of the following bacterial genera are obligate anaerobes?
a. Pseudomonas and Clostridium
b. Bacillus and Clostridium
c. Clostridium only
d. Escherichia and Staphylococcus
MT AAB STUDY GUIDE 2025 UPDATED EXAM WITH MOST
TESTED QUESTIONS AND ANSWERS | GRADED A+ | ASSURED
SUCCESS WITH DETAILED RATIONALES
1. What term describes the morphology of organisms that vary in shape and size?
a. Monomorphic
b. Pleomorphic
c. Diploid
d. Polymorphic
Answer: b. Pleomorphic
Rationale: Pleomorphic organisms can vary in shape and size, as seen in coccobacilli. This
adaptability is an identifying feature of certain bacteria.
2. Which of the following describes a "grape-like cluster" bacterial arrangement?
a. Diplococci
b. Streptococci
c. Staphylococci
d. Tetrads
Answer: c. Staphylococci
Rationale: Staphylococci bacteria arrange in grape-like clusters, which is a distinguishing
feature under a microscope.
3. Capsules are the basis of which of the following tests?
a. Gram staining
b. Serotyping
c. Acid-fast staining
d. Hemolysis tests
Answer: b. Serotyping
Rationale: Capsules are antigenic and play a role in serotyping, which aids in identifying
pathogens like Streptococcus pneumoniae and Klebsiella pneumoniae.
,ESTUDYR
4. A mucoid colony on blood agar medium indicates which characteristic?
a. Lack of capsule
b. Presence of a capsule
c. Flagella production
d. Lack of growth
Answer: b. Presence of a capsule
Rationale: A capsule is often responsible for the mucoid appearance of colonies, aiding in
bacterial virulence and survival.
5. What are dark staining granules in bacteria referred to as?
a. Metachromatic granules
b. Inclusion bodies
c. Peptidoglycan clusters
d. Sporulating granules
Answer: a. Metachromatic granules
Rationale: Metachromatic granules have an affinity for basic dyes and are stained with
methods such as Albert or Neisser stains.
6. Which of the following organisms are non-motile?
a. Shigella and Klebsiella
b. Salmonella and Shigella
c. Klebsiella and Enterobacter
d. Bacillus anthracis and Shigella
Answer: a. Shigella and Klebsiella
Rationale: Both Shigella and Klebsiella are non-motile, unlike their motile counterparts like
Salmonella.
7. In which phase of the bacterial growth cycle does growth cease due to nutrient exhaustion
or toxic product accumulation?
,ESTUDYR
a. Lag phase
b. Log phase
c. Stationary phase
d. Death phase
Answer: c. Stationary phase
Rationale: The stationary phase is marked by a plateau in growth when the bacterial
environment becomes hostile.
8. Which genera of bacteria are known to form spores?
a. Escherichia and Proteus
b. Clostridium and Bacillus
c. Klebsiella and Shigella
d. Pseudomonas and Enterococcus
Answer: b. Clostridium and Bacillus
Rationale: Clostridium and Bacillus form highly resistant endospores that enable survival in
extreme conditions.
9. What term is used for bacteria that grow in the absence of atmospheric oxygen and obtain
oxygen from oxygen-containing compounds?
a. Aerobes
b. Anaerobes
c. Microaerophiles
d. Facultative anaerobes
Answer: b. Anaerobes
Rationale: Anaerobes thrive in oxygen-deprived environments, unlike aerobes, which depend
on free oxygen.
10. Which bacterial arrangement describes a "group of four" cells?
a. Diplococci
b. Tetrads
, ESTUDYR
c. Palisades
d. Chains
Answer: b. Tetrads
Rationale: Tetrads refer to bacteria that organize in groups of four, a notable feature of
Peptococcus.
11. Which staining method is used to observe bacterial capsules?
a. Gram stain
b. India ink negative stain
c. Acid-fast stain
d. Endospore stain
Answer: b. India ink negative stain
Rationale: Capsules are visualized using the India ink negative staining technique, highlighting
the capsule against a dark background.
12. Which bacteria are identified by metachromatic granules?
a. Mycobacterium tuberculosis
b. Corynebacterium diphtheriae
c. Klebsiella pneumoniae
d. Staphylococcus aureus
Answer: b. Corynebacterium diphtheriae
Rationale: Metachromatic granules are characteristic of Corynebacterium diphtheriae and are
visualized with specific dyes.
13. Which of the following bacterial genera are obligate anaerobes?
a. Pseudomonas and Clostridium
b. Bacillus and Clostridium
c. Clostridium only
d. Escherichia and Staphylococcus
