© EVERLY 2025 ALL RIGHTS RESERVED.
Microbiology lab final Exam Questions And
Answers 100% Pass.
Which staining technique is used to determine the thickness of the peptidoglycan layer based on
the cell wall composition? - Answer✔Gram stain
Where would you properly dispose of the following items? - Answer✔Contaminated slides:
Slide trays on student benches
Pipettes: Nalgene buckets on student benches
Used test tubes: Trash cart at front of lab
Uncontaminated broken glass: Broken glass box at front of lab (and notify the TA!)
When are open toed-shoes and shorts allowed in the microbiology labs? - Answer✔Never
What do you use to clean the ocular lenses and objective lenses on your microscope? -
Answer✔Lens cleaner and lens paper
________________________ microscopy is used to view dead, stained microorganisms, and
________________________ microscopy is used to view live, unstained microorganisms -
Answer✔Brightfield, phase-contrast
What is the purpose of isolation streaks on your environmental isolate? - Answer✔To purify one
species of bacteria
In microscopy, what are the three main factors to obtain a good image? -
Answer✔Magnification, resolution, and contrast
Which objective lens is used with immersion oil? - Answer✔100X objective lens
When you first enter the lab and again before you leave the lab, what are two things that you
should always do? - Answer✔Wash your hands and wipe down the lab bench with QT solution
In Exercise 1 Part 2 Phase-Contrast Microscopy, ______________ ______________ was used to
visualize bacteria at 1000x total magnification with oil immersion. - Answer✔Bacillus
megaterium
Which of the following is a growth streak? - Answer✔perfect up down streak
______________ ______________ is the positive control organism for the capsule stain. -
Answer✔Klebsiella pneumoniae
, © EVERLY 2025 ALL RIGHTS RESERVED.
With regard to staining techniques used in this lab, what is the definition of a control organism? -
Answer✔A control organism is known to have a positive or negative result for a specific staining
technique and is used as a comparison to determine the staining result of an unknown bacteria
When differentially staining bacterial cells, what is the purpose of the steaming step? -
Answer✔Endospore stain: Drives the primary stain into keratin proteins
Capsule stain: The steaming step is not used in this staining technique
Gram stain: The steaming step is not used in this staining technique
Based on the following image, where is the appropriate place to label a Petri plate? -
Answer✔Along the side of the bottom plate
How do bacteria benefit from the production of endospores? - Answer✔Endospores allow
bacteria to survive stressful environmental conditions
When staining bacterial cells, what is the purpose of a mordant? - Answer✔The mordant and the
primary stain form an insoluble complex that is attached to a substrate of interest
Why do Gram negative bacteria lose the primary stain during decolorization with 70% ethanol? -
Answer✔The thin peptidoglycan layer does not retain the crystal violet stain
What information must be included when labeling your environmental isolate plates? Select all
correct answers. - Answer✔Your lab section
Where you collected the unknown bacteria (for example, soil or leaf)
Your NAU ID (for example, abc123)
Which isolation streak this plate represents (for example, first isolation streak or second isolation
streak)
The date you streaked this plate
Which of the following stains are used to determine the Gram reaction of bacterial cells? Select
all correct answers. - Answer✔Safranin
Crystal violet
Match the bacterial species listed below with the correct Gram reaction. - Answer✔Bacillus
megaterium: Gram positive
Staphylococcus epidermidis: Gram positive
Escherichia coli: Gram negative
Which staining technique is the quickest way to determine the cell morphology of bacteria? -
Answer✔Simple stain
What is the cellular morphology of spherical-shaped bacterial cells? - Answer✔Cocci (or
coccus)
Microbiology lab final Exam Questions And
Answers 100% Pass.
Which staining technique is used to determine the thickness of the peptidoglycan layer based on
the cell wall composition? - Answer✔Gram stain
Where would you properly dispose of the following items? - Answer✔Contaminated slides:
Slide trays on student benches
Pipettes: Nalgene buckets on student benches
Used test tubes: Trash cart at front of lab
Uncontaminated broken glass: Broken glass box at front of lab (and notify the TA!)
When are open toed-shoes and shorts allowed in the microbiology labs? - Answer✔Never
What do you use to clean the ocular lenses and objective lenses on your microscope? -
Answer✔Lens cleaner and lens paper
________________________ microscopy is used to view dead, stained microorganisms, and
________________________ microscopy is used to view live, unstained microorganisms -
Answer✔Brightfield, phase-contrast
What is the purpose of isolation streaks on your environmental isolate? - Answer✔To purify one
species of bacteria
In microscopy, what are the three main factors to obtain a good image? -
Answer✔Magnification, resolution, and contrast
Which objective lens is used with immersion oil? - Answer✔100X objective lens
When you first enter the lab and again before you leave the lab, what are two things that you
should always do? - Answer✔Wash your hands and wipe down the lab bench with QT solution
In Exercise 1 Part 2 Phase-Contrast Microscopy, ______________ ______________ was used to
visualize bacteria at 1000x total magnification with oil immersion. - Answer✔Bacillus
megaterium
Which of the following is a growth streak? - Answer✔perfect up down streak
______________ ______________ is the positive control organism for the capsule stain. -
Answer✔Klebsiella pneumoniae
, © EVERLY 2025 ALL RIGHTS RESERVED.
With regard to staining techniques used in this lab, what is the definition of a control organism? -
Answer✔A control organism is known to have a positive or negative result for a specific staining
technique and is used as a comparison to determine the staining result of an unknown bacteria
When differentially staining bacterial cells, what is the purpose of the steaming step? -
Answer✔Endospore stain: Drives the primary stain into keratin proteins
Capsule stain: The steaming step is not used in this staining technique
Gram stain: The steaming step is not used in this staining technique
Based on the following image, where is the appropriate place to label a Petri plate? -
Answer✔Along the side of the bottom plate
How do bacteria benefit from the production of endospores? - Answer✔Endospores allow
bacteria to survive stressful environmental conditions
When staining bacterial cells, what is the purpose of a mordant? - Answer✔The mordant and the
primary stain form an insoluble complex that is attached to a substrate of interest
Why do Gram negative bacteria lose the primary stain during decolorization with 70% ethanol? -
Answer✔The thin peptidoglycan layer does not retain the crystal violet stain
What information must be included when labeling your environmental isolate plates? Select all
correct answers. - Answer✔Your lab section
Where you collected the unknown bacteria (for example, soil or leaf)
Your NAU ID (for example, abc123)
Which isolation streak this plate represents (for example, first isolation streak or second isolation
streak)
The date you streaked this plate
Which of the following stains are used to determine the Gram reaction of bacterial cells? Select
all correct answers. - Answer✔Safranin
Crystal violet
Match the bacterial species listed below with the correct Gram reaction. - Answer✔Bacillus
megaterium: Gram positive
Staphylococcus epidermidis: Gram positive
Escherichia coli: Gram negative
Which staining technique is the quickest way to determine the cell morphology of bacteria? -
Answer✔Simple stain
What is the cellular morphology of spherical-shaped bacterial cells? - Answer✔Cocci (or
coccus)
