Question 1
Microbiology LAB QUIZ 2. What is the total magnification of the microscopes used in our microbiology lab when viewing bacteria using oil immersion?
- 10X
- 40X
- 100X
- 400X
- 1,000X
Question 2
Which of the following does NOT accurately describe a bacterial capsule?
- it protects the bacterium from dehydration
- it protects the bacterium from phagocytosis
- it is a type of glycocalyx
- it is typically comprised of polysaccharides
- typically comprised of proteins
- ALL these accurately describe a bacterial capsule
Question 3
With respect to microscopes, what is the meaning of resolution?
- the approximate size of a bacterium
- the degree to which the apparent size of a specimen is increased
- the difference in color between Gram-positive and Bram-negative bacteria
- the difference in the intensity of light between an object and its surroundings
- the distance between the objective lens and the specimen
- the smallest distance between two objects that allows them to be detected as separate objects
Question 4
You perform a Gram stain and your Gram-positive cells appear pink. Which of the following could best explain this aberrant result?
- you added too much iodine to the cells
- you destained your cells too long
- you failed to counterstain your cells
- you failed to destain the cells for long enough
- you failed to heat fix your slide
- you used malachite green instead of safranin
Question 5
If you perform a Gram stain on a mixture of the Gram-negative E. coli and the Gram-positive Staph aureus and skip the counterstaining step, what results would you expect?
- both species would appear pink
- both species would appear purple
- E. coli would appear colorless and Staph aureus would appear pink
- E. coli would appear colorless and Staph aureus would appear purple
- E. coli would appear pink and Staph aureus would appear purple
- E. coli would appear purple and Staph aureus would appear pink
Question 6
Which of the following is NOT accomplished by performing a simple stain on bacteria?
- it allows one to determine the cell groupings characteristic of the bacteria
- it allows one to determine the shape of the bacteria
- it allows one to determine whether the cells are Gram-positive or Gram-negative
- the contrast between the bacteria and their surroundings is increased
- ALL these are accomplished by a simple stain
- NONE these are accomplished by a simple stain
Question 7
How does a simple stain differ from a Gram stain? Microbiology LAB QUIZ 2.
- cell groupings can be determined in a simple stain but not in a Gram stain
- cell motility can be detected in a simple stain but not in a Gram stain
- cell shape can be determined in a simple stain but not in a Gram stain
- only a single stain is used in a simple stain
- only Gram-negative cells can be visualized by a simple stain
- only Gram-positive cells can be visualized by a simple stain
Question 8
An acid-fast stain should be used to detect bacteria in which of the following genera?
- Bacillus
- Clostridium
- Escherichia
- Mycobacterium
- Salmonella
- Streptococcus
Question 9
In an acid-fast staining procedure, what is the primary stain?
- carbolfuchsin
- crystal violet
- malachite green
- methylene blue
- safranin
- iodine
Question 10
What is the purpose of immersion oil?
- causing stains to adhere to cells more strongly
- increasing the magnification of the microscope
- increasing the microscope’s resolution by decreasing light refraction
- it provides a protective coating for the objective lenses
- making cells adhere more strongly to a slide
- staining cells differently based on their cell wall structure
Question 11
How does the primary staining step in an endospore stain differ from that in a Gram stain?
- a mordant attaches to the primary stain in an endospore stain but not in a Gram stain
- aside from using a different stain, there is no difference in the primary staining step in these two types of differential stains
- heat is used to drive stain into endospores
- heat is used to drive stain into Gram-positive cells
- primary staining in an endospore stain must be done in an anaerobic chamber
- the primary staining step is longer in a Gram stain
Question 12
Which of the following pairs of genera commonly produce endospores?
- Bacillus and Escherichia
- Clostridium and Mycobacterium
- Escherichia and Staphylococcus
- Mycobacterium and Bacillus
- Staphylococcus and Clostridium
- NONE of these pairs of genera both produce endospores
Question 13
In a Gram-staining procedure, why does ethanol preferentially destain Gram-negative cells?
- the outer membrane of Gram-negative cells facilitates the entry of ethanol
- the outer membrane of Gram-negative cells restricts binding by the primary stain
- Gram-negative cells have a thicker layer of peptidoglycan
- Gram-negative cells have a thinner layer of peptidoglycan
- teichoic acids of Gram-negative cells repel the primary stain
- teichoic acids of Gram-positive cells bind strongly to the primary stain Microbiology LAB QUIZ 2.
Question 14
Which of the following is accomplished by the destaining step in a Gram staining procedure?
- it causes bacteria to adhere more strongly to the slide
- it counterstains cells that have had their primary stain removed
- it helps spread the bacteria more evenly on the slide
- it traps primary stain in bacterial cell walls
- stain is preferentially removed from Gram-negative cells
- stain is preferentially removed from Gram-positive cells
Question 15
A Gram stain is performed on a mixture of E. coli and Staph aureus. After briefly rinsing the cells with ethanol, what color are the bacteria?
- both species are pink
- both species are purple
- E. coli is colorless and Staph aureus is pink
- E. coli is colorless and Staph aureus is purple
- E. coli is pink and Staph aureus is purple
- E. coli is purple and Staph aureus is pink
Question 16
An endospores stain is performed on Bacillus anthracis. After the destaining step, what color are the bacteria without endospores and what color are the endospores?
- both are green
- the endospores are colorless and the bacteria lacking endospores are green
- the endospores are green and the bacteria lacking endospores are colorless
- the endospores are green and the bacteria lacking endospores are red
- the endospores are red and the bacteria lacking endospores are colorless
- the endospores are red and the bacteria lacking endospores are green
Question 17
Why must the primary stain be regularly reapplied in an acid-fast staining procedure?
- an excess of stain helps stain vegetative cells as well as endospores
- as stain is absorbed into the endospores, the stain volume decreases significantly
- the stain rapidly evaporates during the primary staining step and must be replaced
- the primary stain is much more dilute than the primary stain in a Gram-staining procedure
- the primary stain used in an endospore stain has a much shorter half-life than that used in a Gram stain
- NONE of these accurately describes the reason the primary stain is continually reapplied
Question 18
What is the purpose of the safranin in a Gram-staining procedure?
- it acts as a primary stain
- it acts as a secondary stain
- it binds to the primary stain and makes the stain more difficult to remove
- it helps the bacteria adhere to the slide
- it preferentially removes stain from Gram-negative cells
- it preferentially removes stain from Gram-positive cells
Question 19
Which objective lens has the smallest working distance? Microbiology LAB QUIZ 2.
- 4X (scanning power)
- 10X (low power)
- 40X (high power)
- 100X (oil immersion lens)
- 10X ocular lens
- 400X total magnification
Question 20
Which of the following accurately describes a way in which a capsule stain differs from a Gram stain?
- a wet mount is typically used with a Gram stain, but not with a capsule stain
- ethanol is used to destain in a Gram stain, while acidified alcohol is used to destain in a capsule stain
- ethanol is used to destain in a Gram stain, while water is used to destain in a capsule stain
- heat is used to drive in the primary stain in a capsule stain, but not in a Gram stain
- safranin is used as a secondary stain in a Gram stain, while crystal violet is used as a secondary stain in a capsule stain
- NONE of these accurately describe differences between a capsule stain and a Gram stain
