BIOS 242 Lab Practicum Fundamentals of
Microbiology 2026/2027 – Practice
Questions, Answers & Detailed
Rationales Guaranteed Pass (GRADED
A+)
Question 1
Which instrument is most commonly used to transfer a small
amount of bacterial culture to a sterile medium?
A. Microscope slide
B. Inoculating loop
C. Petri dish
D. Graduated cylinder
Answer: B. Inoculating loop
Rationale: An inoculating loop is designed for aseptically
transferring microorganisms between culture media.
Question 2
What is the primary purpose of using aseptic technique in a
microbiology laboratory?
A. To increase bacterial growth rate
B. To prevent contamination of cultures and the environment
,C. To stain bacterial cells
D. To measure bacterial size
Answer: B. To prevent contamination of cultures and the
environment
Rationale: Aseptic technique minimizes unwanted microbial
contamination and protects both cultures and laboratory
personnel.
Question 3
Which type of microscope is routinely used to observe stained
bacterial cells?
A. Compound light microscope
B. Dissecting microscope
C. Electron microscope only
D. Telescope
_Answer: A. Compound light microscope
Rationale: A compound light microscope provides sufficient
magnification and resolution for routine observation of stained
bacteria.
Question 4
Which objective lens is normally used with immersion oil
during bacterial microscopy?
,A. 4×
B. 10×
C. 40×
D. 100×
_Answer: D. 100×
Rationale: The 100× oil-immersion objective is designed to be
used with immersion oil, which improves resolution by reducing
light refraction.
Question 5
What is the main purpose of immersion oil when using the 100×
objective?
A. To sterilize the slide
B. To increase light refraction
C. To improve resolution
D. To stain bacterial cells
_Answer: C. To improve resolution
Rationale: Immersion oil has a refractive index similar to glass,
allowing more light to enter the objective and improving image
resolution.
Question 6
, Which bacterial arrangement consists of spherical cells
occurring in grape-like clusters?
A. Streptococci
B. Staphylococci
C. Diplococci
D. Streptobacilli
_Answer: B. Staphylococci
Rationale: Staphylococci are cocci arranged in irregular,
grape-like clusters.
Question 7
What shape describes a bacterial cell that is spherical?
A. Bacillus
B. Vibrio
C. Coccus
D. Spirillum
_Answer: C. Coccus
Rationale: Cocci are spherical or approximately spherical
bacterial cells, whereas bacilli are rod-shaped.
Question 8
What is the purpose of heat-fixing a bacterial smear before
staining?
Microbiology 2026/2027 – Practice
Questions, Answers & Detailed
Rationales Guaranteed Pass (GRADED
A+)
Question 1
Which instrument is most commonly used to transfer a small
amount of bacterial culture to a sterile medium?
A. Microscope slide
B. Inoculating loop
C. Petri dish
D. Graduated cylinder
Answer: B. Inoculating loop
Rationale: An inoculating loop is designed for aseptically
transferring microorganisms between culture media.
Question 2
What is the primary purpose of using aseptic technique in a
microbiology laboratory?
A. To increase bacterial growth rate
B. To prevent contamination of cultures and the environment
,C. To stain bacterial cells
D. To measure bacterial size
Answer: B. To prevent contamination of cultures and the
environment
Rationale: Aseptic technique minimizes unwanted microbial
contamination and protects both cultures and laboratory
personnel.
Question 3
Which type of microscope is routinely used to observe stained
bacterial cells?
A. Compound light microscope
B. Dissecting microscope
C. Electron microscope only
D. Telescope
_Answer: A. Compound light microscope
Rationale: A compound light microscope provides sufficient
magnification and resolution for routine observation of stained
bacteria.
Question 4
Which objective lens is normally used with immersion oil
during bacterial microscopy?
,A. 4×
B. 10×
C. 40×
D. 100×
_Answer: D. 100×
Rationale: The 100× oil-immersion objective is designed to be
used with immersion oil, which improves resolution by reducing
light refraction.
Question 5
What is the main purpose of immersion oil when using the 100×
objective?
A. To sterilize the slide
B. To increase light refraction
C. To improve resolution
D. To stain bacterial cells
_Answer: C. To improve resolution
Rationale: Immersion oil has a refractive index similar to glass,
allowing more light to enter the objective and improving image
resolution.
Question 6
, Which bacterial arrangement consists of spherical cells
occurring in grape-like clusters?
A. Streptococci
B. Staphylococci
C. Diplococci
D. Streptobacilli
_Answer: B. Staphylococci
Rationale: Staphylococci are cocci arranged in irregular,
grape-like clusters.
Question 7
What shape describes a bacterial cell that is spherical?
A. Bacillus
B. Vibrio
C. Coccus
D. Spirillum
_Answer: C. Coccus
Rationale: Cocci are spherical or approximately spherical
bacterial cells, whereas bacilli are rod-shaped.
Question 8
What is the purpose of heat-fixing a bacterial smear before
staining?
