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Microbiology lecture exam 1 > Microbiology Lab Exam 2 > Flashcards

Microbiology Lab Exam 2 Flashcards

1
Q

How much time is required by spores of Clostridium botulinum to be killed by moist heat at 120oC?

A

4 to 20 minutes

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2
Q

What do negative staining and positive staining have in common?

A

They increase the contrast between the specimen and the background.

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3
Q

_______ is the third reagent used in the stain. Using a squirt bottle, you ‘wash’ the slide
for 15 to 30 seconds which should change from the color of the first dye to clear.

A

Acid Alcohol

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4
Q

What is heat fixation?

A

Passing the slide through the flame of a burner several times until the smear completely dries.

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5
Q

In the image of the Acid -Fast stain Which bacteria is non-acid-fast?

A

A

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5
Q

Gram staining is an example of

A

Differential stain

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5
Q

Determine TDT of Bacillus subtilis.

A

20min

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6
Q

The Gram stain differentiates between bacteria based on the composition of their
_________.

A

Cell Wall

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6
Q

Before heat fixation, a wet smear of bacterial cells on a slide can first be

A

air-dried.

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7
Q

What color do vegetative cells and endospores of bacteria take after staining; respectively?

A

Green and red

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7
Q

During ethanol treatment in gram staining,

A

crystal violet stain is dissolved in alcohol in Gram negative bacteria due to high
lipid content in the outer layer
crystal violet stain is retained in Gram positive bacteria due to less lipid content
and thick peptidoglycan wall
ALL OF THESE ARE CORRECT

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8
Q

The endospore stain reveals internal structures within cells of the genera Bacillus and Clostridium. T/F

A

TRUE

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9
Q

I’ve just finished doing a Gram stain, and am packing up my things when I notice a large
purple dot on my thumb; what did I forget to do?

A

Wear protective gloves

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10
Q

A _______ stain is one that colors the background surrounding the cell, leaving the cell itself unstained.

A

negative

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11
Q

How does smear preparation of cells from a liquid medium differ from preparation of cells from a solid medium?

A

Water is applied to the slide before emulsifying cells from a solid medium.

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11
Q

Why are encapsulated strains of Streptococcus pneumoniae much more likely to cause disease than strains that do not produce a capsule?

A

They are able to evade immune defenses.

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12
Q

Flagella staining is an example of

A

Simple stain

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13
Q

What color do Gram positive and Gram negative bacteria take after staining; respectively?

A

Purple and red

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13
Q

Which image represents Gram positive bacilli?

A

C

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13
Q

Which image represents Gram positive cocci?

A

A

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14
Q

_______ is the second reagent used in the stain. You have to wait 60 seconds before
tipping it off and washing your slide with water.

A

Iodine

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15
Q

_______ is the mordant reagent used in the stain. You have to wait 60 seconds before
tipping it off and washing your slide with water.

A

Iodine

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15
Q

You make a smear of E. coli and then simple stain the slide with methylene blue. If you failed to use correct aseptic technique by not sterilizing the loop before picking up the bacterial sample for the smear, what results may be seen under the microscope?

A

There may be cells of different shapes, sizes, and arrangements.

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15
Q

Which of the following actions occur due to low temperature?

A

coagulation of proteins

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16
Please choose the answer that best completes the blanks of this sentence in correct order. Basic or cationic dyes have a ______ charge which are attracted to negatively-charged bacteria, whereas acidic or anionic dyes have a ______ charge and do not stain bacteria.
positive; negative
16
Please choose the answer that best completes the blanks of this sentence in the correct order. _______ is used to stain the endospore, and _______ is the stain used to stain the vegetative cell in the Schaeffer-Fulton method of spore staining.
Malachite green; safranin
17
What color do acid-fast and non acid-fast bacteria take after staining; respectively?
Fuschia and blue
18
_______ is the first reagent used in the stain. You have to wait 5 minutes over steam before tipping it off and washing your slide with water.
Carbolfuschin
19
Serial dilution can be used in combination with pour plates as a method for isolating pure cultures. T/F
TRUE
19
Ted heats some food just to boiling, and stores some of it immediately in a container which he places in the refrigerator. A week later he takes the food out and finds it has spoiled. The microbes that spoiled the food are probably ________ organisms.
thermoduric
20
To determine TDT, microbes are exposed to what kind of heat?
Moist heat
21
Streak plates are a useful way to obtain CFUs. T/F
TRUE
22
For the negative stain procedure, one can use
either India ink or nigrosin.
22
Endospores
may be produced when nutrients are scarce.
23
Why would a differential stain be used to stain a microscopic specimen?
Because differential stains contrast two cell types or cell structures.
24
Schaeffer-Fulton is an example of
Differential stain
25
During staining, the smear is heat-fixed in order to __________________.
kill the organism and attach the organism firmly to the slide
26
The anaerobic Clostridium species are troublesome pathogens largely because of their capacity for
endospore production.
27
Which of the following is a common Gram positive bacteria
Bacillus thurigiensis
28
Doing a Gram stain from a culture in broth simply requires the use of a few loops of culture. However, if you want to do a stain from a colony on media, what must you add a drop of to the microscope slide beforehand?
Water
29
You are examining a bacterial smear on a light microscope. You observe pinkish-red bacilli and green dots. You are probably looking at a smear prepared with the ________ stain.
Schaffer-Fulton endospore
30
Which of the following statements is incorrect regarding Gram-negative Bacteria?
None of these choices is incorrect
30
_______ is the last reagent used in the stain. You have to wait 30 seconds before tipping it off and washing your slide with water.
Methylene blue
31
When performing the Gram stain, what type of specimen is used?
Heat-fixed
31
_______ is the decolorizer reagent used in the stain. You have to wait up to 30 seconds before tipping it off and washing your slide with water.
Alcohol
32
Both simple and differential stained specimens allow for the visualization of all the following, EXCEPT?
Motility
33
_______ is the mordant reagent used in the stain. You have to wait 5 minutes before tipping it off and washing your slide with water.
Steam
33
Which image represents Gram negative bacilli?
D
34
The ________ stain uses malachite green.
endospore
34
Please choose the answer that best completes this sentence in the correct order. In the Anthony method of capsular staining, the stain used is _________ and the decolorizer used is an aqueous solution of 20% ___________.
crystal violet; copper sulfate
35
Why does culture age affect the results of a spore stain?
Older cultures are most likely to produce spores due to depleted nutrition.
36
I. Alcohol II. Gram's iodine III. Carbolfuchsin IV. Crystal violet V. Methyl red VI. Methylene blue VII. Safranin Use Figure the list above to answer the following questions: The substances listed below are used in various differential staining techniques. Which of the following lists the correct order for the solutions used in the Gram stain?
IV - II - I - VII
36
At temperatures higher than the maximum growth temperature for an organism
hydrogen bonds are broken, proteins are denatured, and membranes become too fluid.
37
Why is refrigeration a considered short-term method of storing bacteria?
Refrigeration slows metabolism but does not stop it.
38
The colorization of bacteria with more than one dye solution to distinguish between microbial cell types is called a _________.
differential stain
39
Why is negative staining useful for accurately determining cell size?
Heat fixation is not performed so cells do not shrink.
39
If the iodine step were omitted in the Gram-staining procedure, what color would you expect Gram-positive bacteria to stain and what color would you expect Gram-negative bacteria to stain?
Gram-positive = red; Gram-negative = red
40
Determine TDT of Staphylococcus aureus
1min
40
Which of the following conditions are required for the determination of thermal death time?
temperature is fixed and time is varied
41
The Counter stain used in Gram staining is
Safranin
42
In general, TDT of Bacillus subtilis is greater than the TDT of Staphylococcus aureus. This is attributed to the spore forming nature of Bacillus subtilis. T/F
TRUE
43
Which image represents Gram negative cocci? Correct Answer
B
44
Which of the following stains is not a differential stain?
Negative
45
Agar is a useful compound in the microbiology lab because it is an excellent nutrient for bacteria. T/F
FALSE
46
Among the following which one is the most effective method of killing microorganisms?
High temperature
47
What type of microscopy produces an image of unstained cells that is similar to one achieved by negative staining?
Darkfield
48
The ACID-FAST STAIN is important, because it is a __________.
Differential stain that is helpful in diagnosing tuberculosis.
49
Acid-fast staining is an example of
Differential stain
50
What makes Mycobacterium particularly resistant to staining?
The presence of mycolic acid in their cell walls
51
If you know you have a pure culture of spore-forming bacilli but the endospore stain on samples shows only reddish pink rods, which choice below is reasonable explanation for what you see?
None of the cells happened to be producing spores at the time they were stained.
51
In Gram staining, if some bacteria retain the crystal violet stain after alcohol treatment. Then the bacteria is:
Gram positive
51
Please choose the answer that best completes the blanks of this sentence in the correct order. After acid-fast staining, Mycobacterium tuberculosis would be _______ in color, whereas Proteus vulgaris would be ________ in color.
red; blue
51
Washing dishes in the dishwasher with detergent and hot water is a ________ process.
degerming and disinfecting

Microbiology lecture exam 1 (4 decks)

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