Download 2a Lab TQ bank Stains

Which of the following is an example of a differential stain:
a.
b.
c.
d.
Capsule Stain
Spore Stain
Gram Stain
Flagella Stain
If a bacterium is positive for the acid-fast stain, what does this indicate?
a.
b.
c.
d.
It does not have mycolic acid in the cell wall
It has mycolic acid in the cell wall
It has tartaric acid in the cell membrane
It does not have tartaric acid in the cell membrane
What is the primary stain in the gram stain?
a.
b.
c.
d.
Alcohol
India ink
Crystal violet
Congo red
What is the primary stain in acid-fast stain?
a.
b.
c.
d.
Acetone
Carbol fuschin
Mycolic acid
Safranin
If a bacterium is gram stain positive, it will appear as a ____________ color; gram stain
negative will indicate a ____________ color.
a.
b.
c.
d.
blue, red
pink, blue
red, pink
violet, pink
What is the first step in preparing a slide for staining?
a.
b.
c.
d.
Wash the slide with water
“Fix” the slide by passing it over a flame a few times
Place the microbes on the slide
Place 2-3 drops of acetone alcohol over the specimen on the slide
What is the purpose of “fixing” a slide?
a. To keep the bacteria alive to see it under the microscope
b. To enlarge the bacteria to see it easier
c. To attach a specimen (like cheek cells or bacteria) to the slide and kill the
microbes
d. To increase the pH of the specimen
What type of dye will we primarily be using in the lab?
a.
b.
c.
d.
Complex dye
Basic dye
Acidic dye
Solvent dye
What does a negative stain do?
a.
b.
c.
d.
Stains the bacteria
Creates a more negative charge
Stains the background instead of the bacteria
Stains the cell membrane of the bacteria
Which of the following is NOT TRUE in regards to the purpose of a mordant in the gram
stain?
a.
b.
c.
d.
It allows the primary stain to react chemically with the cell
It keeps the crystal violet from being washed out of by the alcohol
It makes the bacteria (or cell) stick to the slide better
It forms a complex with crystal violet and peptidoglycan in the cell wall of
bacteria
What is the purpose of using a negative stain?
a) Determine the size of an organism
b) Determine the shape of an organism
c) Counting the number of cells present
d) A and B are correct
e) A, B, and C are correct
Which of the following are true about negative stains?
a) It is acidic and has a positive charge
b) It is acidic and has a negative charge
c) It has a basic pH and a positive charge
d) It has a basic pH and a negative charge
Which of the following morphological shapes classify a round bacterium?
a) Coccus
b) Bacillis
c) Helical
A rod-shaped bacterium that occurs in strands is which classification?
a) Streptococcus
b) Streptobacillus
c) Spirochete
A bacterial colony shaped like a cluster of grapes is which classification?
a) Streptococcus
b) Streptobacillus
c) Spirochete
16. A stain used to determine the true cell morphology and size is the:
a. negative stain.
b. simple stain.
c. acid fast stain.
d. Gram stain.
18. Dyes for bacteria contain which of the following?
a) Positively charged chromophores that are attracted to the negative charge of
bacteria
b) Positively charged chromophores that are attracted to the positive charge of
bacteria
c) Negatively charged chromophores that are attracted to the negative charge of
bacteria
d) Negatively charged chromophores that are attracted to the positive charge of
bacteria
19. Which of the following are negative stains?
a) Nigrosin
b) India ink
c) Congo red
d) Fuschsin red
e) (a), (b), and (c) are correct
f) All of those are negative stains
21. Which of the following is a differential stain?
a) Congo red
b) India ink
c) Gram stain
d) Methylene blue
22. Which of the following are basic dyes?
a) Methylene blue
b) Crystal violet
c) Eosin
d) (a) and (b)
e) All of the above
23. Which of the following are acidic dyes?
a) Methylene blue
b) Crystal violet
c) Eosin
d) All of the above
24. The simplest way to make a slide of bacteria is to prepare a wet mount. The main
drawback to this method is that________
a. bacteria are generally colorless and transparent
b. all bacteria are pathogenic
c. live bacteria move around too quickly to be observed
d. reverse osmosis occurs, killing and distorting bacteria
e. cover slips are too expensive to use regularly
25. Before heat fixation, a wet smear must first be
a) Air-dried
b) Blotted dry
c) Rinsed with water
d) Stained with a basic dye
e) None of the answers are correct
26. Which of the following are differential stains?
a) Gram stain
b) Spore stain
c) Acid-fast stain
d) All are correct
27. Which species of bacteria produce endospores?
a. Bacillus anthracis.
b. Streptococcus mutans
c. Mycobacterium smegmatis
d. Staphylococcus aureus
e. two of these are spore formers
28. With respect to timing the most critical part of the Gram stain is the application of:
a. crystal violet. b. methylene blue.
c. iodine.
d. safranin. e.
alcohol
29. What color is S. aureus after decolorizer is used?
a) Purple
b) Pink
c) No color
30. What color is S. aureus after the counterstain is added?
a) Purple
b) Pink
c) No color
31. What color is E. coli before the primary stain is added?
a) Purple
b) Pink
c) No color
32. What color is E. coli after the primary stain is added?
a) Purple
b) Pink
c) No color
33. What color is E. coli after decolorizer is used?
d) Purple
e) Pink
f) No color
34. What color is E. coli after the counterstain is added?
d) Purple
e) Pink
f) No color
35. What is the primary stain for the acid-fast technique?
a) Crystal violet
b) Carbol fuschin
c) Malachite green
d) Iodine
e) Safranin
36. What is the mordant for the acid-fast technique?
a) Crystal violet
b) Malachite green
c) Iodine
d) Heat
e) Safranin
39. The negative stain _________________.
a. stains the organisms’ cell walls and protoplasm.
b. allows you can estimate pathogenicity
c. stains the background surrounding the organisms.
d. causes the flagella to become visible
e. two of these
43. If you did a Gram stain on a culture that came out looking Gram negative even
though you
knew it should be Gram positive, which of the following could have caused the
misleading
results?
a. the culture was too old
b. you forgot to add ethanol
c. you used too much alcohol during decolorization
d. the organism is Acid fast +
e. two of these are possible reasons for the wrong Gram reaction.
44. What is the mordant for the Gram stain technique?
a) Crystal violet
b) Malachite green
c) Iodine
d) Heat
e) Safranin
45. What is the decolorizer for the Gram stain technique?
a) Alcohol
b) Acid alcohol
c) Water
46. What is the counter-stain for the Gram stain technique?
a) Crystal violet
b) Carbol fushin
c) Malachite green
d) Iodine
e) Safranin
48. At what temperature is a motility stab incubated?
a) Body temperature
b) Room temperature
c) 50 °C
51. What color are endospores after a Gram stain?
a) Green
b) Red
c) Colorless
52. What external structure makes Mycobacterium different from other organisms?
a) It has a capsule
b) It has mycolic acid in the cell wall
c) It has a larger amount of peptidoglycan than most
53. Endospores are produced by bacteria in the genus
a) Bacillus
b) Clostridium
c) Mycobacterium
d) Both (a) and (b)
e) Both (a) and (c)
54. Acid-fast staining is useful for identifying the causative agent of
a) Leprosy
b) Tetanus
c) Tuberculosis
d) Both (a) and (c)
e) All of the above
55. You are given a culture of E. coli. You do a successful streak for isolation. You
select a
single colony and Gram stain it. You see equal numbers of cocci and bacilli, all
Gram
negative. The most reasonable conclusion is that ____________.
a. you have contamination
b. you have a pure culture with some looking like cocci because of age or
viewing angle
c. you did the gram stain incorrectly
d. you have a coccus that can also look like a rod
e. two of these are reasonable conclusions
62. What is the purpose of a smear prep?
To prepare an organism for staining
63. What are two problems that arise when a slide is not heat fixed properly?
a) burn the cells off
b) cells don’t stick
64. What causes a stain to adhere to bacterial cells?
Charged ions in the dye are attracted to the charges in the bacteria
65. What are the three purposes of a spore stain?
To show endospore presence, location, and size
66. Name an organism which can be identified with an acid-fast stain
Mycobacterium
67. What is the purpose of using a pure culture technique?
To separate a mixture of organisms into pure cultures
68. What does TSA stand for?
Triptic soy agar
69. What is the purpose of a motility test?
To determine the presence of a flagella to assist with identifying the organism
70. What is the function of a mordant?
Forms an insoluble complex with the primary stain in cells that are positive for the
primary stain.
71. What layer of the cell wall does a primary stain color?
Peptidoglycan layer
72. How do gram positive and gram negative bacteria differ in their cell wall structure?
Gram positive have 90% peptidoglycan, Gram negative have 10%
73. How does culture age affect the results of a Gram stain?
Older cultures can’t hold the purple color as well
74. Why is Bacillus more resistant than Staph to environmental conditions?
Can produce endospores when environmental conditions are not favorable.
75. What is the difference between true motility and Brownian motion?
In true motility, the organism moves from one location to another. Brownian motion
is just water molecules hitting the organism, causing it to bounce around. It is not
true motility.
Multiple Choice: Select the single best answer to the following.
12. Tuberculosis and leprosy are both disease caused by:
a. viruses.
b. Streptococcus.
c. Klebsiella. d. Mycobacterium. e.
Bacillus.
13. Basic dyes are used to stain bacteria because they have:
a. positively charged chromophores that are attracted to the negative charge
of bacteria.
b.
bacteria.
c.
bacteria.
d.
bacteria.
e.
negatively charged chromophores that are attracted to the positive charge of
positively charged chromophores that are attracted to the positive charge of
negatively charged chromophores that are attracted to the negative charge of
none of the above
15. Smears from a slant are:
a. placed directly onto a clean slide and spread into a dime-sized area.
b. placed onto a drop of water on a clean slide and spread into a dime sized area.
c. made by using as much culture as can be lifted with a loop to insure a good
smear.
d. made by using a sample from a broth culture.
e. Both B and C are correct
31. Endospores are:
a. the result of sexual conjugation in bacteria.
b. found only in gram negative bacteria.
c. resistant to chemicals and heat.
d. all of the above are correct statements about endospores.
e. none of the above
32. The purpose of heat-fixing a bacterial smear slide is to:
a. get the bacteria to stick to the surface of the slide so they don’t wash off during
the later staining.
b. kill and preserve the bacteria.
c. break up clumps of bacteria by evenly melting them across the slide.
d. a & b
e. a, b, & c
Matching: Match the organisms listed in Column 1 with the appropriate description in
Column 2.
Descriptions in column 2 may be used once, more than once, or not at all.
COLUMN 1
COLUMN 2
36. Mycobacterium E
A. Gram negative bacillus
37. S. aureus
D
B. Gram positive bacillus
38. B. cereus
B
C. Gram negative coccus
39. E. coli
A
D. Gram positive coccus
E. Tuberculosis
56-63. List the reagents used in the Gram stain. [8pts]
PRIMARY STAIN
Color of Gram positive after
primary stain
Color of Gram negative after
Crystal violet
Purple
Purple
primary stain
MORDANT
DECOLORIZER
COUNTER STAIN
Color of Gram positive after
counter stain
Color of Gram negative after
counterstain
Gram’s iodine
Alcohol
Safranin
Purple
pink
64-65. Explain what is happening to both Gram positive and Gram negative cells during
the Gram stain procedure. [2pts]
Gram positive bacteria have more peptidoglycan in their cell wall, so they retain the
crystal violet/iodine complex after decolonization with alcohol, and they appear
purple.
Gram negative organisms have less peptidoglycan in their cell wall, plus they have
an outer membrane, so the crystal violet/iodine complex washes away when alcohol
is applied. Therefore, the Gram negative organisms must be counterstained with a
red dye to be visualized. This red dye is not seen through the darker purple in Gram
positive organisms.