4.2: Agar Plates

Question 1

Growth media comes in two forms:

Answer 1

liquid and solid.

Question 2

The addition of a polysaccharide derived from seaweed (algae) extract creates a solid medium called ______.

Answer 2

Agar

Question 3

The addition of a ______ extract creates a solid medium called agar.

Answer 3

polysaccharide derived from seaweed (algae)

Question 4

______ is used to create a solid, smooth surface on which microbes can grow.

Answer 4

Agar

Question 5

As they grow, microbes form ______ that take on the appearance of individual isolated dots. However, as the microbe increases in number, the isolates merge into one another.

Answer 5

Colonies

Question 6

Once the microbe has grown to cover the entire plate, this is referred to as a ______.

Answer 6

Lawn

Question 7

______ is the cousin of Agar.

Answer 7

Gelatin

Question 8

______ is an animal-derived product that gives Jell-O its classic texture and form.

Answer 8

Gelatin

Question 9

______ is simply the plant-based form of Gelatin and acts in a very similar way.

Answer 9

Agar

Question 10

______ is a multi-purpose media capable of growing a wide variety of microorganisms.

Answer 10

LB agar, also known as lysogeny broth

Question 11

LB agar, also known as lysogeny broth, is a…….

Answer 11

……multi-purpose media capable of growing a wide variety of microorganisms.

Question 12

LB agar plates are ______ in color as shown in color.

Answer 12

pale yellow

Question 13

LB is classified as a ___1___ and ___2___ media.

Answer 13

1. non-selective
2. non-differential

Question 14

LB agar is commonly used for growing ______, a microbe often associated with molecular microbiology applications based on its ability to easily produce recombinant proteins.

Answer 14

E. Coli

Question 15

Why is E. coli so commonly used in molecular microbiology applications?

Answer 15

Because of its ability to easily produce recombinant proteins.

Question 16

What is shown in this picture?

Answer 16

Agar plates. LB agar plates are shown with either the top lid in place (left) or tilted off (right). The agar is melted, sterilized, and poured into a sterile petri dish then allowed to solidify at room temperature.

Question 17

______ is another multi-purpose media capable of growing a wide variety of microorganisms.TSA plates are virtually identical in color to LB plates. TSA media is non-selective and non-differential and serves as the base when formulating specialized (enriched) medias.

Answer 17

Trypticase soy agar, also known as TSA or TSAYE

Question 18

Trypticase soy agar, also known as TSA or TSAYE is……

Answer 18

……another multi-purpose media capable of growing a wide variety of microorganisms.TSA plates are virtually identical in color to LB plates. TSA media is non-selective and non-differential and serves as the base when formulating specialized (enriched) medias.

Question 19

______ serves as the base when formulating specialized (enriched) medias.

Answer 19

Trypticase soy agar, also known as TSA or TSAYE

Question 20

______ is a derivative of TSA whereby mammalian blood, often from sheep, is added to the plate composition at a concentration range of 5-10%.

Answer 20

Blood agar, also known as BAP (blood agar plates),

Question 21

Blood agar, also known as BAP (blood agar plates), is a……..

Answer 21

……derivative of TSA whereby mammalian blood, often from sheep, is added to the plate composition at a concentration range of 5-10%.

Question 22

BAP have a distinct ______ coloration.

Answer 22

red

Question 23

BAP is an enriched, ___1___ yet ___2___ media.

Answer 23

1. non-selective
2. differential

Question 24

The red blood cells in the media promote the growth of ___1___ microorganisms, such as various strains of ___2___.

Answer 24

1. fastidious
2. Streptococcus

Question 25

BAP is a differential media used to detect ______ activity.

Answer 25

hemolytic

Question 26

______ is a differential media used to detect hemolytic activity.

Answer 26

BAP

Question 27

Hemolysis is what?

Answer 27

The lysis (breakdown) of red blood cells

Question 28

______is the lysis (breakdown) of red blood cells

Answer 28

Hemolysis

Question 29

In what 3 ways is Hemolysis classified?

Answer 29

is classified as alpha, beta, or gamma.

Question 30

______present as greenish-brown color colonies due to the incomplete (partial) lysis of red blood cells.

Answer 30

Alpha Hemolysis

Question 31

Alpha Hemolysis present as.......

Answer 31

......greenish-brown color colonies due to the incomplete (partial) lysis of red blood cells.

Question 32

______is classified as the capacity of a microbe to completely lyse red blood cells. The resulting lysis presents as a distinct zone of clearing around the growing colony.

Answer 32

Beta Hemolysis

Question 33

Beta Hemolysis is classified as........

Answer 33

......the capacity of a microbe to completely lyse red blood cells. The resulting lysis presents as a distinct zone of clearing around the growing colony.

Question 34

______designates the absence or lack of hemolytic activity, and the resulting colonies are often white/tan in color growing on the red background color of the unaffected blood agar plate.

Answer 34

Gamma Hemolysis

Question 35

Gamma Hemolysis designates.......

Answer 35

......the absence or lack of hemolytic activity, and the resulting colonies are often white/tan in color growing on the red background color of the unaffected blood agar plate.

Question 36

______ is red in color and is an enriched, selective, and differential media.

Answer 36

Columbia CNA agar

Question 37

Columbia CNA agar is......

Answer 37

......red in color and is an enriched, selective, and differential media.

Question 38

The media of ______ contains the antimicrobial agents colistin and Nalidixic acid, it suppresses the growth of Gram-negative bacteria and is, therefore, used for isolation of Gram-positive microbes.

Answer 38

Columbia CNA agar

Question 39

The media of Columbia CNA agar contains the antimicrobial agents ___1___ and ___2___, it suppresses the growth of Gram-___3___ bacteria and is, therefore, used for isolation of Gram-___4___ microbes.

Answer 39

1. colistin 2. Nalidixic acid 3. negative 4. positive

Question 40

Similar to BAP, the Columbia CNA agar media is also......

Answer 40

......enriched with blood, which allows for differentiation based on hemolytic patterns.

Question 41

Chocolate agar, also known as CHOC or as chocolate blood agar (CBA), is ______derivative of blood agar plates.

Answer 41

an enriched, non-selective, non-differential

Question 42

Unlike blood agar plates that contain intact red blood cells, chocolate agar plates contain red blood cells that have been______.

Answer 42

lysed by heat

Question 43

The cooking of the red blood cells in chocolate blood agar gives the media a ______ appearance, hence the name.

Answer 43

dark brown chocolaty

Question 44

Lysed red blood cells release various growth factors into the media required for the cultivation of ______.

Answer 44

fastidious, pathogenic bacteria.

Question 45

Chocolate agar is also considered an ___1___. Examples include the ___2___ bacteria ___3___ and ___4___.

Answer 45

1. enriched media 2. Gram-negative 3. Haemophilus influenzae 4. Neisseria meningitidis

Question 46

______ is pale red in color and is both a selective and differential media.

Answer 46

MacConkey agar

Question 47

MacConkey agar is ___1___ in color and is both a ___2___ and ___3___ media.

Answer 47

1.Pale Red 2. Selective 3. Differential

Question 48

The presence of ___1___ and ___2___ in MacConkey agar formulation restricts ___3___ bacterial growth.

Answer 48

1. crystal violet 2. bile salts 3. Gram-positive

Question 49

Only ______ microbes can be grown on MacConkey agar.

Answer 49

Gram-Negative

Question 50

In ______, lactose and the pH indicator neutral red—it is only red when under acidic conditions—are added to differentiate between lactose fermenters (lac+; red colonies) and non-fermenters (lac-; white/tan colonies).

Answer 50

MacConkey agar

Question 51

In MacConkey agar, lactose and the pH indicator neutral red—it is only red when under acidic conditions—are added to differentiate between ___1___ and ___2___.

Answer 51

1. lactose fermenters (lac+; red colonies) 2. non-fermenters (lac-; white/tan colonies)

Question 52

In MacConkey agar, the base color of the agar plate also often changes color as the microbes consume the nutrients within the agar. The agar can turn ___1___ within the surrounding area of a growing non-fermenting microbe. Similarly, the agar may turn ___2___ within the region surrounding a lac+ microbe given its level of acid production during fermentation ___3___.

Answer 52

1. yellow (pH > 8.0) 2. pink or even a darker red 3. (pH < 6.8)

Question 53

True or False: In MacConkey agar, the Gram-negative/lac+ bacteria Escherichia coli is often used to demonstrate the formation of yellow colonies.

Answer 53

False. In MacConkey agar, the Gram-negative/lac+ bacteria Escherichia coli is often used to demonstrate the formation of VIBRANT PINK colonies.

Question 54

Within the clinical laboratory setting, where each patient sample may contain hundreds of species of bacteria, MacConkey agar is used to isolate ___1___ microbes belonging to the ___2___ family such as ___3___ and ___4___ species.

Answer 54

1. intestinal pathogenic 2. Enterobacteriaceae 3. Salmonella 4. Shigella

Question 55

______is a variant of MacConkey agar specifically formulated to detect the presence of the pathogenic strain of Escherichia coli O157:H7.

Answer 55

Sorbitol-MacConkey agar, also known as SMAC

Question 56

Sorbitol-MacConkey agar, also known as SMAC, is a......

Answer 56

.......variant of MacConkey agar specifically formulated to detect the presence of the pathogenic strain of Escherichia coli O157:H7.

Question 57

Under standard ___1___ conditions, Escherichia coli is able to ferment both ___2___.

Answer 57

1. enteric (gut) 2. lactose and sorbitol

Question 58

Under standard enteric (gut) conditions, ______ is able to ferment both lactose and sorbitol.

Answer 58

Escherichia coli

Question 59

E. coli O157:H7 is unable to ______.

Answer 59

ferment sorbitol

Question 60

______ plates contain sorbitol (instead of lactose) in order to differentiate non-pathogenic strains of Escherichia coli (red colonies; acidic conditions) from pathogenic O157:H7 strains (white colonies; neutral to basic conditions).

Answer 60

SMAC

Question 61

SMAC plates contain ___1___ in order to differentiate ___2___ from ___3___.

Answer 61

1. sorbitol (instead of lactose) 2. non-pathogenic strains of Escherichia coli (red colonies; acidic conditions) 3. pathogenic O157:H7 strains (white colonies; neutral to basic conditions)

Question 62

______also known as EMB, is red in color and is classified as both a selective and differential form of media.

Answer 62

Eosin Methylene Blue agar

Question 63

Eosin Methylene Blue agar, also known as ______ , is..........

Answer 63

EMB ......red in color and is classified as both a selective and differential form of media.

Question 64

As the naming suggests, EMB contains eosin and methylene blue that restricts the growth of ______.

Answer 64

Gram-positive bacteria

Question 65

In EMB, microorganisms are differentiated based on their ability to ______ present in the media.

Answer 65

ferment the lactose

Question 66

In EMB, similar to MacConkey agar, non-fermenting (lac-) microbes grow as ___1___, while lactose-fermenting microbes produce ___2___ on the surface of the agar.

Answer 66

1. white/tan colonies 2. dark (purple to black) colonies

Question 67

if Escherichia coli is grown on EMB agar plates, colonies will have a distinctive ______.

Answer 67

metallic green sheen

Question 68

if ______ is grown on EMB agar plates, colonies will have a distinctive metallic green sheen

Answer 68

Escherichia coli

Question 69

______ also known as MSA, is red in color and is both a selective and differential media

Answer 69

Mannitol salt agar

Question 70

MSA is selective for ___1___ and can differentiate members of the ___2___.

Answer 70

1. Gram-positive bacteria 2. Staphylococci family

Question 71

______ contains a high concentration of sodium chloride (~7.5-10%) that prevents the growth of other microorganisms (selectivity) while the presence of an alternate sugar source, mannitol, along with the pH indicator dye phenol red serves to differentiate pathogenic from non-pathogenic strains of Staph.

Answer 71

MSA

Question 72

MSA contains a high concentration of ___1___that prevents the growth of other microorganisms (selectivity) while the presence of an alternate sugar source, ___2___, along with the pH indicator dye___3___ serves to differentiate pathogenic from non-pathogenic strains of ___4___.

Answer 72

1. sodium chloride (~7.5-10%) 2. mannitol 3. phenol red 4. Staph

Question 73

In MSA Pathogenic strains, such as Staphylococcus aureus, have the ability to ___1___, thus lowering the pH of the medium and changing the dye color from ___2___ to ___3___.

Answer 73

1. ferment mannitol 2. red (pH >8.2) 3. yellow (pH < 6.8)

Question 74

What are the 9 Agar Plates and their colors?

Answer 74

1. LB agar, also known as lysogeny broth -YELLOW- 2. Trypticase soy agar, also known as TSA or TSAYE -YELLOW- 3. Blood agar, also known as BAP (blood agar plates) -RED- 4. Columbia CNA agar -RED- 5. Chocolate agar, also known as CHOC or as chocolate blood agar (CBA) -BROWN- 6. MacConkey agar -PINK- 7. Sorbitol-MacConkey agar, also known as SMAC -PINK- 8. Eosin Methylene Blue agar, also known as EMB -DARK RED- 9. Mannitol salt agar, also known as MSA -RED-

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Question 85

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