Lab exam 1

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1
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What does the dark yellow mean?

beta hemolysis: complete breakdown of blood cells

2
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S. mutans; what does the light yellow mean?

alpha hemolysis: partial breakdown of blood cells

3

What is an antibiotic?

a substance produced by the natural metabolic processes of some microorganisms that can inhibit others.

4

What does this mean: the narrow/ limited spectrum of antimicrobials?

antimicrobials are effective against a limited array of microbial types; ex. a drug only effective on gram (+) bacteria

5

What's the name of the technique that tests drug susceptibility?

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KIRBY-BAUER disk diffusion TEST

6
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In the Kirby test, the clear area around an antibiotic is called...

the zone of inhibition: where the drug inhibited bacterial growth:); the foggy area represents growth

7

What is the MIC (minimum inhibitory concentration) for drugs? *hint: it's a number

it's the smallest concentration of drug (smallest does) that VISIBLY inhibits growth.

8

EX: using penicillin G, what's the MIC for E. Coli?

100ug/ mLmeaning that anything below this dose will not inhibit E. Coli growth

9
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What bacteria is this?

Staphylococcus aureus purple & round, cocci-shaped

10

What's the therapeutic index (TI)?

When you choose a drug w/ HIGHEST level of SELECTIVITY.... but lowest level of toxicity, HIGH index is desirable to ensure safety.

11

How do you calculate the therapeutic index?

toxic dose divided by MIC

12

What is the triple sugar iron (TSI) agar used for?

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3 reasons:

1) to determine if an organism can ferment sugars (glucose, lactose/sucrose),

2) to produce gas and

3) to produce H2S

13

When advanced microbiology is not readily available (like in tropics), what is diagnosis based on?

clinical & laboratory features

14

What is the TSI agar used to differentiate?

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gram (-) enteric bacilli

15

What prevents cross-bridge formation by binding to the terminal D-Ala-D-Ala dipeptide?

Vancomycin

16

What is the TSI agar differentiation based on?

it's based on carb fermentation & production of hydrogen sulfide

17

What is the function of the phenol red in the TSI agar?

the pH indicator will turn yellow if pH is<6.8

red if pH is>8.28.2

pH = basic; failure to turn butt yellow

18

In the TSI agar, if an organism turns yellow...

this indicates that acids of fermentation have been produced

19

In the TSI agar, what does a yellow butt and red slant mean?

that the bacterium only fermented glucose

20

In TSI test, what does a yellow butt and yellow slant mean?

that the culture can ferment lactose or sucrose

21

An organism that can ferment glucose only... looks like..

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red slant and yellow base/ butt

22

In TSI test, when a culture produces gas... what does it look like?

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23

What are the IMViC tests used for?

to differentiate the enteric family of bacteria

24

What does the IMViC stand for?

Indole test Methyl Test & Vogues-Proskauer Test and Citrate Test

25

What are the IMViC tests used for?

to differentiate the enteric family of bacteria

26

What does the IMViC stand for?

Indole test Methyl Test & Vogues-Proskauer Test and Citrate Test

27

Why are the IMViC tests important?

to test drinking water for presence of sewage indicator E. Coliafter this test, you should be able to rule out Enterobacter areogenes

28

What is the medium for the Indole Test?

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Tryptone broth

29
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What results are these?

these are the results of Methyl Red Test

30

What is the medium for the Citrate Test?

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= citrate agar slants; below are the results

31

What does the Indole Test detect?

tryptophan hydrolysis

32

What does the MR-VP medium differentiate?

it differentiates gram (-) intestinal bacteria, based on the products they produce when they ferment glucose

33

What is the purpose of the citrate test?

to determine the ability of an organism to use citrate as its sole source of carbon.

34

Heterotrophs & autotrophs deal with... carbon or energy?

CARBON!

Heterotrophs, like us, must obtain carbon through the 4 macromolecules

35

What are the processes in aerobic respiration?

1. glycolysis,

2. Kreb's Cycle

3. respiratory chainand oxygen is the final electron acceptor

36

How does aerobic and anaerobic respiration differ?

both use the same 3 processes...but in anaerobic resp, sulfate & nitrate are the final acceptors

37

What is the sole process of fermentation?

glycolysisand final acceptors: organic compounds

38

What is fermentation?

incomplete oxidation of glucose or another carb (example: alcohol, lactic acid) when oxygen is unavailable ATP yield is small

39

When yeast acts on glucose, what does it produce?

Ethyl alcohol

40
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What test is this?

carbohydrate fermentation test

41

In carb fermentation test (lab10), what color was the original bacteria and the bacteria that did not ferment?

Pink/ reddish this was our negative control.

42
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What does A and AG mean?

YELLOW= fermentation; bacteria on Left produced an acidbacteria on Right produced acid+gas

43

Peptidoglycan is unique to

bacteria

44

What inhibits the transpeptidase that cross-links the peptides?

Penicillin

45

What 3 bacteria did we use for the carb fermentation test?

E. Coli, P. vulgaris and....

46
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Identify the gram reaction seen at the pointer?

Identify the morphology(shape)?

Identify the arrangement?

G+

Cocci

diplococci

47
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Identify the staining technique?

Identify the purpose of iodine in this technique?

Name the primary morphology seen in the slide?

Name the most likely Genus and species seen in this image?

Gram stain

Iodine is a mordant that firmly fixes the primary dye, crystal violet, to the G+ cells

Staphylococci

Staphylococcus aureus

48
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Identify the method?

What is the purpose of this method?

Streak plate

Isolation of single pure colonies of bacteria

49
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Identify microscope part # 1

What is the magnification of part #1

Identify microscope part # 6 that is labeled 10X.

what is the magnification when using the oil immersion objective lens?

Ocular

10X

Low pwr objective

1000X

50
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Identify this selective and differential media that allows for differentiation between staph, aureus and staph epidermis

Name which sector you would find S.aureus

Name the ingredient that makes this plate "selective"

why is sector "1" turning yellow.

Mannitol salt agar

Sector 1

Salt allows halophiles to be selected on the plate

Fermentation of mannitol (ph idicator turns yellow in presence of acid)

51
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What does EMB stand for in this test?

Which bacteria are inhibited on this plate?

Name the bacteria isolated on the above plate?

Eosin methylene blue

G+

While EMB allows for differentiation of lactose fermenters from non-lactose fermenters, E.coli (and other coliforms) often give a “green sheen” appearance.

52
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Identify which disk the bacteria is totally resistant to.

Identify which disk the bacterial is most susceptible to.

Name 2 reason for the colonies seen in the inhibition zone at the arrow.

SSS (triple sulfa)

P (penicillin)

Mixed culture (contamination) and resistant bacteria

53

In the carb test, can you see gas bubbles if no acid was produced?

No gas will form ONLY if acid is produced

54

A 40X objective and an 10X ocular produce a total magnification of
A) 50
B) 400
C) 90

B) 400

55

Resolution

two objects can be separated and still be distinguished

56

Shorter_____ and _______________l will provide better resolution.

wavelength, larger numerical aperture

57

The resolution of a microscope can be improved by changing the
A) condenser.
B) fine adjustment.
C) wavelength of light.
D) diaphragm.
E) coarse adjustment.

C) wavelength of light.

58

The ability of a lens to separate or distinguish between small objects that are close together is called
A) Magnification
B) Numerical aperture
C) Refractive index
D) Resolution

D) Resolution

59
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what is label #1

ocular lens

60
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what is label #2

Objective Lens

61
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what is label #3

Carrying Handle

62
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what is label #4

Slide Holder

63
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what is label #5

stage

64
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what is label #6

condenser

65
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what is label #7

Condenser

66
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what is label #8

Light

67
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what is label #9

Coarse adjustment

68
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what is label #10

Fine adjustment

69

If an object is viewed through the 10x ocular and 10x objective lens the total magnification is

100x

70

The Gram stain was devised in 1884 by the Dutch physician______

Hans Christian Gram

71

The advantage of a wet prep:

study a living/motile organism.

72

Gram (+) cocci in clusters is associated with

Staphylcocci

73

The most common structural support is the _______.

cell wall

74

The cell wall confers shape and rigidity to
the cell, and helps it withstand ___________?

turgor pressure

75

When alcohol is used in the gram stain procedure, the lipids in the gram negative organisms cell wall ______________________?

dissolve in the decolorizer, washed along with the dye.

76

If you de-colorize too much it will

lose stain

77

Methylene Blue is a

counterstain and_________?

78

The basic cell groupings for cocci are:

pairs (diplococcic),

chains (streptococci),

clusters (staphylococci),

packs of four (tetrads)

79

The basic shapes for organisms are

spherical

rod shaped

spiral

80

In colonial morphology:

features that provide clues in identifying organisms are shape, size, consistency, surface, texture, elevation, color, density.

81

What is the most commonly used microscope?

compound microscope

82
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What shape are these?

Filamentous rods (bacilli)

83
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What shape are these?

Spirochetes shape

84
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What shape are these?

Borrelia burgdorferi bacteria- cause of lyme disease

Spirochetes shape

85
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What shape are these?

Cocci in pairs (diplococci)

86
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What shape are these?

Streptococcus pneumoniae-diplococci

87

What are the 2 key characteristics of a reliable microscope?

magnification & resolving power

88

What magnification should be used for oil?

100X lens

89

What is the aseptic technique?

a method that prevents the introduction of contaminants in an environment

90
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Looking at the picture above, what can you tell yourself?

Bacteria are negatively charged

91
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What shape are these?

Spirillium shape- helical shape like spirochetes but lacks flexibility

92

How do vibrio-shaped bacteria look like?

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like curved rods, comma shape

93

What is a pleomorphic?

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A pleomorphic organism is able to change its shape based on environment.

94

Cocci that remain in chains after dividing are called...

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Streptococci

95

"Strepto" refers to chains while "staphylo" refers to.

clusters

96

What are pathogens?

pathogens: disease-causing organisms

97
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Is this Gram+ or Gram - ?

Staphylococcus (S.)aureus Gram- a member of our normal flora

98
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Streptococcus (S.) pyogenes

the aerotolerant bacterium that causes strep throat

99
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What is the structure?

E. Coli vs. salmonella

100
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Helicobacter pylori

causes stomach ulcers

101
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What is this?

Neisseria Gonorrhaeae

102

True or False

In a simple stain, one dye is used and shape & size are revealed

TRUE

103

What does a differential stain use?

a primary stain and counter-stain to distinguish cell types or parts

104

What charge does a basic dye have?

cationic, positive charge

105

True or False

In a positive stain, the negatively charged surfaces of microbes attracts the dye and get stained

TRUE

106

What is the 1st step in a simple stain?

1. place a loopful of culture on clean slide and spread it in a smear across marked area

107

What are steps 3-7 of simple staining?

3. air-dry;

4. heat-fix the smear;

5. add stain for one min;

6. wash off stain with water;

7. use blot paper to take off excess wate and finally just use microscope to examine it

108

True or False

Negative stains color the cell background

TRUE

109

Difference between positive and negative staining?

no heat fixing needed for negative stains

110

If the object you are studying takes up the dye...

it's positive staining

111

What is the most common structural support in prokaryotes?

A. cell membrane

B. organelles

C. phospholipid bilayer or

D. cell wall

D. cell wall

112

What does the bacterial cell wall consist of?

A. peptidoglycan

B. cellulose

C. fiber

D. chitin

A. peptidoglycan

113

True or False

Enzymes in peptidoglycan cell wall make really good targets for antibiotics

TRUE-

examples of antibiotics: penicillin; vancomycin

114

Which bacteria are resistant to antibiotics?

gram (-) bacteria because of thin wall

115

What type of stain is a Gram-stain?

differential stain

116

Gram (+) bacteria retain the crystal violet stain becase of...

their thick cell wall

117

Gram (-) bacteria do not retain the stain because of...

their THIN cell wall

118

Unlike the gram (+)... Gram (-) bacteria have...

porins & liposaccharides in inner and outer membrane

119

What are the 4 chemicals used for a gram-stain procedure?

  • Crystal violet (primary stain)
  • Iodine solution/Gram's Iodine (mordant that fixes crystal violet to cell wall)
  • Decolorizer (e.g. ethanol)
  • Safranin (secondary stain)
120

What are the first 3 steps of a Gram-stain experiment?

1. make sure slide is clean

2. add a loopful of water/ liquid bacteria- spread thin & air dry

3. heat fix (pass it quickly 2-3 times) and then wait for slide to cool

121

What are the remaining steps of a Gram-stain experiment?

4. Flood smear with Crystal violet (and wait exactly1 min);

5. rinse gently with water;

6. add iodine for exact 1 min;

7. rinse again;

8. add alcohol drop by drop (then wait ONLY 10-20 sec);

9. do the final rinse;

10. finally add safranin for 1 min (then rinse & grab microscope)

122

True or False

Microbes in nature exist in complex, multi species communities

TRUE

123

What inhibits the transpeptidase that cross-links the peptides

Penicillin

124

What are the 2 main types of culture media that bacteria are grown in?

1. liquid/ broth- to observe features of pure culture

2. solid- to separate members of a mixed culture

125

What are the 3 main categories of media classification?

1. physical state

2. chemical classification

3. and functional type; eg selective or differential

126

What is a synthetic media?

one that contains pure organic & inorganic compounds in an exact chemical formula

127

Define differential media

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the differentiation of colonies of desired microbes from others; eg blood agar

128

What is a selective media?

contains 1 or more agents that inhibit growth of undesired microbes

129

Difference between nutrient broth & nutrient agar?

both contain beef extract & peptone but nutrient broth doesn't use an agar

130
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What is the process going on the picture above?

Inoculation- an aseptic technique to produce pure culture

131

What are the 3 techniques for isolating pure colonies?

1) streak plate

2) spread plate

3) pour plate

132

What are the main principles in a streak method?

1. drag the bacteria 4 times

2. After each streak/ drag, sterilize the loop

133

Why do you need different types of media?

Because bacterial pathogens exist in very small numbers (so you need different tests)

134

What is a fastidious bacterial pathogen?

a microorganism that will grow only if special nutrients are present

135

What's an example of a media that is both selective & differential?

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Mannitol Salt Agar

136

True or False

The MacConkey Agar is a selective agent

TRUE:

Because the bile salts select for gram (-) bacteria, esp of Enterobacteriaea (Enterics) family

137

How is the MacConkey Agar also differential?

Colonies of bacteria that ferment lactose turn colonies pink

138

What's the enriched and differential media?

The blood agar differential agent is the type of hemolysis

139

What are the 3 types of hemolysis?

1. beta

2. alpha

3. gamma

140

McConkey agar is used to diffentiate bacteria based on

their ability to ferment lactose

141

Which of the following is the inhibitor in Mannitol Salt agar?

Sodium chloride

142

Catalase is

an enzyme that break down hydrogen peroxide

143

When you begin the view an object, use________ knob first then _________?

coarse adjustment

the fine adjustment knob

144

Oil Immersion

un-refracted light rays will enter the lens and improves magnification and the resolving power of a microscope

145
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Identify the arrangement?

coccus

diplococci

streptococci

146
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Identify the arrangement?

Staphylococci

Tetrad

147

Strep=
Staph=

chain

cluster

148

Pleomorphic=

variable in shape and arrangement

149

Simple staining allows the observer to distinguish cell morphology. What other property can also be determined by this procedure?

ARRANGEMENT

150

Name any two acid/base indicators that can be used in bacterial growth media.

METHYL RED, PHENOL RED

151

This instrument is typically used when transferring microbes to an agar deep tube

TRANSFER NEEDLE

152

We used two distinct techniques to isolate single colonies of bacteria. Which isolation technique involves growing colonies on an agar plate but does not require knowledge of the concentration of cells in the stock culture?

STREAK PLATING

153

Which bacterial characteristic is being observed when the terms circular, irregular, and rhizoid are use?

COLONY FORM

154

A gram-negative bacterium that ferments lactose is streaked onto MacConkey agar. What will the plate look like after an appropriate incubation period?

The bacteria will appear pinkish/red with some precipitation.

155

All of the following are true about agar except it
A. liquefies at 100°C

B. is a polysaccharide extracted from algae
C. solidifies at ~40°C

D. is metabolized by many bacteria

E. facilitates obtaining pure cultures

D. is metabolized by many bacteria

156

What is the most important reason to heat fix a bacterial smear on a glass slide?
A. To kill the bacteria.

B. To complex the dye to the slide.

C. To adhere the cells to the slide.

D. To clean the dust off of the slide.

E. To make sure that the cells are motile.

C. To adhere the cells to the slide.

157

Which of the following aseptic (or sterile) techniques would you perform during the transfer of a microorganism from a broth culture to an agar slant?
A. Rapidly flaming the necks of both tubes before the transfer.
B. Flaming a loop or needle until the entire wire is red before the transfer.
C. Setting your loop carefully on the bench top immediately after the transfer.
D. All of the above.
E. Both A and B are correct

E. Both A and B are correct

158

Which of the following statements best defines a pure culture?

A culture consisting of only one type of bacteria.

159

What is the counter-stain used in negative staining?
A. Gram’s iodine

B. Crystal violet

C. Safranin

D. Copper sulfate

E. It’s a trick question, there is no counter-stain

E. It’s a trick question, there is no counter-stain

160

Which of the following chemicals is not considered a general by-product of fermentation?
A. acid

B. alcohol

C. pyruvic acid

D. gas

E. oxidized NADH

C. pyruvic acid

161

Why is oil used with an oil immersion lens?
A. The refractive index of air is lower than that of glass bending light rays away from the objective lens.
B. The refractive index of mineral oil is the same as that of glass, decreasing light refraction.
C. Oil increases the numerical aperture of the lens.
D. Oil increases the magnification of the lens.
E. A and B are correct.

E. A and B are correct.

162

Which of the following statements is most correct about the Gram stain?
A. Crystal violet differentially stains Gram positive cells.
B. Gram's iodine differentially stains Gram positive cells.
C. Ethanol differentially destains Gram negative cells.
D. Safranin red differentially stains Gram negative

C. Ethanol differentially destains Gram negative cells.

163

Name the 4 reagents used in the Gram staining procedure and their purpose

CRYSTAL VIOLET = PRIMARY STAIN; GRAM’S IODINE = MORDANT; COMPLEXES PRIMARY STAIN; 95% ETHANOL = DESTAIN/DECOLORIZING PRIMARY STAIN; SAFRANIN = SECONDARY STAIN

164

Describe a Gram+

90% peptidogycan

Teichoic Acid

Phospholipid by-layer

transport proteins

165

Describe a Gram-

10% Peptidoglycan

LPS outer Membrane

Phospholipid by-layer

transport proteins

166

This type of media is used to allow bacterial cells to form individual colonies.

A. Agar plate
B. Agar slant
C. Broth
D. Agar deep

A. Agar plate

167

The process of sterilizing an inoculating device for transfer of microorganisms from one media to another is called

A. Culturing
B. Aseptic transfer
C. Streak plate
D. Staining

B. Aseptic transfer

168

The Gram stain works due to differences in the __________ of bacteria.

A. DNA
B. Cell walls
C. Cell membranes
D. Proteins

B. Cell walls