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Elementary Microbiology > Lab Quiz 1 > Flashcards

Lab Quiz 1 Flashcards

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1
Q

What shape is bacillus megaterium

A

rod

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2
Q

what shape is staphylococcus epidermidis

A

round

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3
Q

Of what value is a simple stain?

A

to determine cell morphology, size, and arrangement

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4
Q

What is the purpose of heat-fixing the smear?

A

it denatures bacterial enzymes, preventing them from digesting cell parts. it also preserves the microbes

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5
Q

Another method of fixing smears is to use methanol instead of heat. How does alcohol chemically fix the bacteria?

A

the alcohol dehydrates the cell, causing them to denature and to be preserved onto the slide

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6
Q

In heat-fixing, what would happen if too much heat were applied?

A

cells will be distorted and unusable

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7
Q

Methylene blue can be prepared as a basic stain or an acidic stain. How would the pH of the stain affect the staining of bacteria?

A

the pH of the stain affects characteristics and transformation of bacteria

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8
Q

Can dyes other than methylene blue be used for direct staining?

A

Yes. crystal violet is catonic, and can directly stain positively charged microbes

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9
Q

Bacteria can be seen without staining. Why, then, was Koch’s recommendation of fixing and staining important for the discovery of the bacterial causes of diseases?

A

How bacteria stain is very important in medical diagnostics and treatment with the correct antibiotic. Also, staining bacteria can make small characteristics in the bacteria visible that otherwise would not be.

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10
Q

Quality control staff in a sterilization unit of a hospital used a simple stain to determine whether bacteria were present in sterilized materials. A simple stain of sterile saline used for respiratory therapy revealed the presence of bacteria. Is the saline contaminated?

A

It is possible. Negative controls and proper aseptic technique are needed to ensure the dye itself and immersion oil are not contaminated. These controls will help narrow down the source of the bacteria. However, staining does not show whether or not the cells were alive.

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11
Q

What color will a gram-negative cell stain?

A

red

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12
Q

What color will a gram-positive cell stain?

A

blue

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13
Q

What shape is bacillus subtilis?

A

rods

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14
Q

what shape is escherichia coli?

A

rods

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15
Q

How does staphylococcus epidermidis gram stain?

A

gram positive (blue)

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16
Q

How does bacillus subtilis gram stain?

A

gram positive (blue)

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17
Q

How does escherichia coli gram stian?

A

gram negative (red)

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18
Q

Why do gram-positive cells more than 24 hours old stain gram-negative?

A

The cells can no longer hold the primary stain.

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19
Q

Can iodine be added before the primary stain in a gram stain?

A

No, it will prevent the crystal violet from washing.

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20
Q

List the steps of the gram staining procedure in order (omit washings), followed by the color of gram-positive cells and gram-negative cells after each step.

A

STEP: GRAM+/GRAM-

  1. crystal violet: blue/blue
  2. iodine: blue/blue
  3. ethanol or acetone: blue/clear
  4. safranin: blue/red
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21
Q

Which step can you omit without affecting determination of the gram reaction?

A

safranin

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22
Q

Suppose you performed a gram stain on a sample from a pure culture of bacteria and observed a field of red and purple cocci. Adjacent cells were not always the same color. What would you conclude?

A

The sample is old and some of the cells are losing their ability to hold the primary stain.

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23
Q

Suppose you are viewing a gram-stained field of red rods and purple cocci through the microscope. What do you conclude?

A

the sample has a mixed culture

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24
Q

Human cells can be stained with crystal violet and safranin, so why can’t human cells be gram stained?

A

the only cells that stain gram positive are those that have a thick cell wall, so the primary would be easily removed by alcohol. safranin would bind to remaining structures with a negative charge.

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25
Q

Considering that it isn’t possible to identify bacteria from a gram stain, why might a physician perform a gram stain on a sample before prescribing an antibiotic?

A

to determine which antibiotic the bacteria will be sensitive to

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26
Q

What color will an acid-fast organism stain in the acid-fast stain?

A

fuchsia/red

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27
Q

What color will a non-acid-fast cell stain in the acid-fast stain?

A

blue

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28
Q

What shape is mycobacterium smegmatis?

A

rods

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29
Q

What will mycobacterium smegmatis stain with acid-fast stain?

A

acid-fast positive (red)

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30
Q

What will escherichia coli stain with acid-fast stain?

A

acid-fast negative (blue)

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31
Q

Did the acid-fast stained sputum slide indicate a possible positive test for tuberculosis?

A

yes

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32
Q

What are the large blue-stained areas on the sputum slide for an acid-fast stain?

A

WBCs and non acid-fast organisms

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33
Q

What is the decolorizing agent in the gram stain?

A

ethanol

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34
Q

What is the decolorizing agen in the acid-fast stain?

A

acid alcohol

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35
Q

What diseases are diagnosed using the acid-fast procedure?

A

tuberculosis, leprosy, and nacordiosis

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36
Q

What is phenol (carbolic acid), and what is its usual application?

A

Phenol is an alcohol with a benzene ring attached. It’s an aromatic compound and it is used as a disinfectant because it controls the growth of microorganisms.

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37
Q

The original acid-fast stain required heating the smear to force the carbolfuchsin into the wall. Why can heat be eliminated in the Kinyoun modification that you used?

A

Because by adding tergitol to the stain, it reduces the surface tension between the cell wall of the mycobacterium and the stain.

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38
Q

How might the acid-fast characteristic of Mycobacterium anhance the organism’s ability to cause disease?

A

Thy have a waxy coating around their cell, that makes it difficult for antibiotics to penetrate the cell wall, making the chances of disease higher.

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39
Q

In 1882, after experimenting with staining Mycobacterium, Paul Ehrlich wrote that only alkaline disinfectants would be effective against Mycobacterium. How did he reach this conclusion without testing the disinfectants?

A

Mycobacterium are resistant to acid so the bacterium does not decolorize when exposed to acid alcohol.

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40
Q

Clinical specimens suspected of containing Mycobacterium are digested with sodium hydroxide (NaOH) for 30 minutes prior to staining. Why is this technique used? Why isn’t this technique used for staining other bacteria?

A

Digestion removes unwanted bacteria, sputum, and human cells. It is not used for staining others because it kills other bacteria.

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41
Q

The acid-fast stain is used to detect Cryptosporidium protozoa oocysts in fecal samples. Which of the following would you expect to be major component of the oocyst wall: carbohydrates, lipids, or proteins?

A

lipids

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42
Q

What disease is caused by Cryptosporidium?

A

cryptosporidiosis, or crypto

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43
Q

When a medium is selected for culturing bacteria, what 3 things must be provided?

A

macronutrients, an energy source, and any necessary growth factors

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44
Q

a medium whose exact chemical composition is known

A

chemically defined medium

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45
Q

media for which the exact chemical composition varies slightly from batch to batch

A

complex media

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46
Q

What type of bacteria are routinely grown on complex media?

A

chemoheterotrophic bacteria

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47
Q

commonly used liquid complex medium

A

nutrient broth

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48
Q

when agar is added to nutrient broth and it becomes a solid medium

A

nutrient agar

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49
Q

an extract from marine red algae, has some unique properties that make it useful in culture media. few microbes can degrade this substance, so it remain solid during microbial growth.

A

agar

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50
Q

most common method of sterilizing culture media that are heat stable by using stem under pressure

A

steam sterilization, or autoclaving

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51
Q

contain solid media that provide a large surface area for examination of colonies

A

petri plates

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52
Q

microbes that are intentionally introduces

A

inoculated

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53
Q

bacteria that are inoculated into culture media increase in number during this time period

A

incubation period

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54
Q

after suitable incubation, liquid media become _____, or cloudy, as a result of bacterial growth

A

turbid

55
Q

a population of cells that arises from a single bacterial cell

A

colony

56
Q

a colony that arises from a group of the same microbes attached to one another

A

colony-forming unit

57
Q

each colony that appears different is usually what?

A

a different species

58
Q

clumps of microbial cells

A

flocculent

59
Q

membrane across the surface of the broth

A

pellicle

60
Q

microbial cells that have settled on the bottom of the tube

A

sediment

61
Q

unwanted microbes

A

contaminants

62
Q

used in microbiology to exclude contaminants

A

aseptic technique

63
Q

rendered free of all life

A

sterilized

64
Q

provide large numbers of bacteria in a small space and are easily trasported

A

broth cultures

65
Q

test tubes containing solid culture media that were left at an angle while the agar solidified. provide a solid growth surface, but are easier to store and transport than petri plates.

A

agar slants

66
Q

agar is allowed to solidify in the bottom of a test tube. often used to grow bacteria that require less oxygen than is present on the surface of the medium.

A

an agar deep

67
Q

used to determine whether a bacterium is motile. motile bacteria will move away from the point of inoculation giving the appearance of an inverted pine tree

A

semisolid agar deeps containing 0.5-0.7% agar instead of the usual 1.5% agar

68
Q

end of the wire is bent into a loop

A

inoculating loop

69
Q

end of wire is straight

A

inoculating needle

70
Q

Why are mixed cultures of little use in studying microorganisms?

A

it’s difficult to determine which organism is responsible for an observed activity

71
Q

name the three dilution methods for isolating bacteria

A

streak plate, spread plate, and pour plate

72
Q

isolation technique where a loop is used to streak the mixed sample many times over the surface of a solid culture medium in a petri plate. this causes the bacteria to fall off the loop one by one an ultimately to be distributed over the agar surface, where each cell or group of the same bacteria as a pair or chain develops into a colony. most common technique

A

streak plate technique

73
Q

quantitative techniques to determine the number of bacteria

A

spread plate and pour plate

74
Q

the number of bacteria in a sample can be determined by counting what?

A

the number of colony-forming units

75
Q

small amount of previously diluted specimen is spread over the surface of a solid medium using a spreading rod

A

spread plate technique

76
Q

a small amount of diluted sample is mixed with melted agar and poured into empty, sterile petri dishes. after incubation, bacterial growth is visible as colonies in and on the agar

A

pour plate technique

77
Q

how many colonies must be in the plate to calculate the number in the original sample of bacteria?

A

25-250

78
Q

colony-forming units per ml=?

A

number of colonies/(dilution X amount plated)

79
Q

What is the advantage of using petri plates rather than test tubes in microbiology?

A

gives room for different colonies to grow

80
Q

What are bacteria using for nutrients in nutrient agar?

A

carbon, nitrogen, phosphorus, sulfur, protein

81
Q

What is the purpose of the agar?

A

to support growth on the surface of a petri plate and it also is used as a solidifying agent

82
Q

How could you determine whether the turbidity in your nutrient broth tube was from a mixture of different microbes or from the growth of only one kind of microbe?

A

you could transfer the sample to a petri plate with agar and see if different types of colonies grow

83
Q

What other methods can be used to determine motility?

A

hang drop and wet mount

84
Q

What is the primary use of slants?

A

a solid growth site that is easier to store and transport

85
Q

What is the primary use of deeps?

A

biochemical (oxygen and motility)

86
Q

What is the primary use of broths?

A

transport, arrangement, large number of bacteria

87
Q

What is the purpose of flaming the loop before use? After use?

A

Sterilization. To kill any previous bacteria on the loop before exposed to preferred bacteria. Afterwards it’s to kill any bacteria it was exposed to.

88
Q

Why must the loop be cool before you touch it to a culture? Would you set down the loop to let it cool? How do you determine when the loop is cool?

A

If it is not cool before you touch it to a culture, the heat will kill the bacteria. You should not set down the loop to let it cool. It will be cool after approximately 20-30 seconds.

89
Q

Why is aseptic technique important?

A

It involves certain procedures that have to be performed carefully in order to minimize contamination by the pathogen. It is crucial in order to identify the bacteria cultured.

90
Q

Why was the arrangement of Lactococcus in the broth culture different from the arrangement on the slant culture in the second period?

A

There is more room for binary fission in the broth

91
Q

For a bacterium, what evolutionary advantage is associated with forming a pellicle in a liquid medium?

A

motility and a greater chance of survival (protection)

92
Q

How can you tell that the media provided for this exercise were sterile?

A

There were no indicators of growth

93
Q

Describe the growth pattern of a motile organism in a semisolid deep.

A

There will be lateral growth. It will move away from point of an inoculation and will look like an inverted pine tree.

94
Q

How will the arrangement of the Lactococcus Lactis in broth differ from the arrangement in the slant culture?

A

They will be more packed together in the broth, and more spread out in the slant.

95
Q

abhorescent pattern of growth

A

branched

96
Q

echinulate pattern of growth

A

pointed

97
Q

filiform pattern of growth

A

even

98
Q

rhizoid pattern of growth

A

rootlike

99
Q

consisted of biconvex lenses and were essentially magnifying glasses

A

simple microscopes

100
Q

has two lenses between the eye and the object, which magnifies and illuminates the object

A

compound microscope

101
Q

shows dark objects in a bright field, used most often

A

brightfield compound microscope

102
Q

holds the slide

A

the stage

103
Q

transmits the magnified image

A

body tube

104
Q

holds the light source in the microscope

A

the base

105
Q

is above the light source and consists of several lenses that concentrate light on the slide by focusing it into a cone

A

condenser

106
Q

controls the angle and size of the cone of light. this ability to control the amount of light ensures that optimal light will reach the slide

A

iris diaphragm

107
Q

microscope with only one ocular lens

A

monocular microsope

108
Q

microscope with two ocular lenses

A

binocular microscope

109
Q

larger knob used for focusing with the low-power objectives (4X and 10X)

A

coarse adjustment

110
Q

smaller knob used for focusing with the high-power and oil immersion lenses

A

fine adjustment

111
Q

the area seen through a microscope

A

field of vision

112
Q

depends on the type of objective lens used with the ocular lens

A

magnification

113
Q

objective with 4X

A

scanning lens

114
Q

objective with 10X

A

low-power lens

115
Q

40X-45X objective

A

high-dry lens

116
Q

objective with 97X-100X

A

oil immersion lens

117
Q

most important lens in microbiology

A

oil immersion

118
Q

why don’t they make microscopes with higher magnification?

A

the resolution would be poor

119
Q

can be adjusted with a wheel that regulates the amount of current to the bulb

A

intensity of the light

120
Q

usually requires more light

A

higher magnification

121
Q

the ability of a lens to reveal fine detail or two points distinctly separated

A

resolution, or resolving power

122
Q

the resolving power is a function of the wavelength of light used and a characteristic of what lens system?

A

numerical aperture

123
Q

smaller wavelengths of light _____ resolving power

A

improve

124
Q

the amount the light bends

A

refractive index

125
Q

using _____ minimizes light loss, and the lens focuses very close to the slide

A

oil

126
Q

as light rays pass through a lens, they are bent to converge at the ______, where an image is formed

A

focal point

127
Q

multiple focal points create a fussy periphery

A

spherical aberration

128
Q

how can you minimize spherical aberration

A

iris diaphragm

129
Q

when a multitude of colors is seen in the field

A

chromatic aberration

130
Q

light source of one wavelength. most logical, but expensive method of eliminating chromatic aberrations

A

monochromatic light

131
Q

when a subject is in focus with one lens, it will be in focus with all the lenses

A

parfocal

132
Q

the distance between the objective lens and the specimen

A

working distance

133
Q

What 2 plants were used to remove phosphorous and ammonia and the benson sewage plant?

A

cattails and bullrush

134
Q

In the final treatment of effluent, what chemical did they use?

A

chlorine

Elementary Microbiology (45 decks)

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