Page 1 of 80
DIAGNOSTIC MICROBIOLOGY, 7TH EDITION BY CONNIE R.
MAHON EXAM QUESTIONS WITH VERIFIED QUESTIONS
DETAILED RATIONALES GRADED A+
Diagnostic Microbiology, 7th Edition By Connie R. Mahon
Original Practice Questions with Answers and Rationales
PART 1: INTRODUCTION TO CLINICAL MICROBIOLOGY
SECTION 1: BACTERIAL CELL STRUCTURE, PHYSIOLOGY, METABOLISM, AND GENETICS
Questions 1–30
1. Which structure is responsible for the rigid shape of a bacterial cell and provides protection
against osmotic lysis?
A) Cytoplasmic membrane
B) Capsule
C) Cell wall
D) Nucleoid
Answer: C) Cell wall
Rationale: The cell wall provides rigidity and strength to the exterior of the cell, protecting
against osmotic lysis .
2. The cytoplasmic membrane of bacteria is composed primarily of:
A) Peptidoglycan
B) A phospholipid bilayer with embedded proteins
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C) Lipopolysaccharide
D) Teichoic acid
Answer: B) A phospholipid bilayer with embedded proteins
Rationale: The cytoplasmic membrane is a phospholipid bilayer with embedded proteins that
regulates transport .
3. Gram-positive bacteria differ from Gram-negative bacteria primarily in the:
A) Presence of ribosomes
B) Thickness of the peptidoglycan layer
C) Type of nucleic acid
D) Method of reproduction
Answer: B) Thickness of the peptidoglycan layer
Rationale: Gram-positive bacteria have a thick peptidoglycan layer; Gram-negative bacteria
have a thin layer with an outer membrane .
4. Lipopolysaccharide (LPS) is an important virulence factor found in:
A) Gram-positive bacteria
B) Gram-negative bacteria
C) Mycoplasma
D) Viruses
Answer: B) Gram-negative bacteria
Rationale: LPS is found in the outer membrane of Gram-negative bacteria and acts as an
endotoxin .
5. The bacterial structure responsible for adherence to host tissues and evasion of
phagocytosis is the:
A) Flagella
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B) Capsule
C) Pili
D) Endospore
Answer: B) Capsule
Rationale: The capsule is a protective layer that aids in adherence and evasion of phagocytosis .
6. Plasmids are:
A) Essential for bacterial survival
B) Extrachromosomal DNA molecules that can carry antibiotic resistance genes
C) Part of the bacterial chromosome
D) Found only in Gram-positive bacteria
Answer: B) Extrachromosomal DNA molecules that can carry antibiotic resistance genes
Rationale: Plasmids are extrachromosomal DNA that often carry resistance genes .
7. The term "generation time" refers to:
A) The time required for a bacterial population to double
B) The time required for a bacterial cell to die
C) The time required for DNA replication
D) The time required for spore formation
Answer: A) The time required for a bacterial population to double
Rationale: Generation time is the time for a bacterial population to double .
8. Which of the following describes the bacterial growth phase where the number of dying
cells equals the number of new cells formed?
A) Lag phase
B) Log phase
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C) Stationary phase
D) Death phase
Answer: C) Stationary phase
Rationale: In stationary phase, cell division equals cell death .
9. Binary fission in bacteria results in:
A) Two genetically identical daughter cells
B) Four genetically diverse daughter cells
C) One daughter cell and one parent cell
D) Eight daughter cells
Answer: A) Two genetically identical daughter cells
Rationale: Binary fission produces two identical daughter cells .
10. Bacteria that require oxygen for growth are called:
A) Anaerobes
B) Microaerophiles
C) Obligate aerobes
D) Facultative anaerobes
Answer: C) Obligate aerobes
Rationale: Obligate aerobes require oxygen for growth .
11. The bacterial enzyme catalase is used to:
A) Produce oxygen from hydrogen peroxide
B) Convert nitrate to nitrite
C) Break down glucose
D) Synthesize peptidoglycan
DIAGNOSTIC MICROBIOLOGY, 7TH EDITION BY CONNIE R.
MAHON EXAM QUESTIONS WITH VERIFIED QUESTIONS
DETAILED RATIONALES GRADED A+
Diagnostic Microbiology, 7th Edition By Connie R. Mahon
Original Practice Questions with Answers and Rationales
PART 1: INTRODUCTION TO CLINICAL MICROBIOLOGY
SECTION 1: BACTERIAL CELL STRUCTURE, PHYSIOLOGY, METABOLISM, AND GENETICS
Questions 1–30
1. Which structure is responsible for the rigid shape of a bacterial cell and provides protection
against osmotic lysis?
A) Cytoplasmic membrane
B) Capsule
C) Cell wall
D) Nucleoid
Answer: C) Cell wall
Rationale: The cell wall provides rigidity and strength to the exterior of the cell, protecting
against osmotic lysis .
2. The cytoplasmic membrane of bacteria is composed primarily of:
A) Peptidoglycan
B) A phospholipid bilayer with embedded proteins
,Page 2 of 80
C) Lipopolysaccharide
D) Teichoic acid
Answer: B) A phospholipid bilayer with embedded proteins
Rationale: The cytoplasmic membrane is a phospholipid bilayer with embedded proteins that
regulates transport .
3. Gram-positive bacteria differ from Gram-negative bacteria primarily in the:
A) Presence of ribosomes
B) Thickness of the peptidoglycan layer
C) Type of nucleic acid
D) Method of reproduction
Answer: B) Thickness of the peptidoglycan layer
Rationale: Gram-positive bacteria have a thick peptidoglycan layer; Gram-negative bacteria
have a thin layer with an outer membrane .
4. Lipopolysaccharide (LPS) is an important virulence factor found in:
A) Gram-positive bacteria
B) Gram-negative bacteria
C) Mycoplasma
D) Viruses
Answer: B) Gram-negative bacteria
Rationale: LPS is found in the outer membrane of Gram-negative bacteria and acts as an
endotoxin .
5. The bacterial structure responsible for adherence to host tissues and evasion of
phagocytosis is the:
A) Flagella
,Page 3 of 80
B) Capsule
C) Pili
D) Endospore
Answer: B) Capsule
Rationale: The capsule is a protective layer that aids in adherence and evasion of phagocytosis .
6. Plasmids are:
A) Essential for bacterial survival
B) Extrachromosomal DNA molecules that can carry antibiotic resistance genes
C) Part of the bacterial chromosome
D) Found only in Gram-positive bacteria
Answer: B) Extrachromosomal DNA molecules that can carry antibiotic resistance genes
Rationale: Plasmids are extrachromosomal DNA that often carry resistance genes .
7. The term "generation time" refers to:
A) The time required for a bacterial population to double
B) The time required for a bacterial cell to die
C) The time required for DNA replication
D) The time required for spore formation
Answer: A) The time required for a bacterial population to double
Rationale: Generation time is the time for a bacterial population to double .
8. Which of the following describes the bacterial growth phase where the number of dying
cells equals the number of new cells formed?
A) Lag phase
B) Log phase
, Page 4 of 80
C) Stationary phase
D) Death phase
Answer: C) Stationary phase
Rationale: In stationary phase, cell division equals cell death .
9. Binary fission in bacteria results in:
A) Two genetically identical daughter cells
B) Four genetically diverse daughter cells
C) One daughter cell and one parent cell
D) Eight daughter cells
Answer: A) Two genetically identical daughter cells
Rationale: Binary fission produces two identical daughter cells .
10. Bacteria that require oxygen for growth are called:
A) Anaerobes
B) Microaerophiles
C) Obligate aerobes
D) Facultative anaerobes
Answer: C) Obligate aerobes
Rationale: Obligate aerobes require oxygen for growth .
11. The bacterial enzyme catalase is used to:
A) Produce oxygen from hydrogen peroxide
B) Convert nitrate to nitrite
C) Break down glucose
D) Synthesize peptidoglycan
