Selective and differential experiment quiz

Question 1

what is the definition of selective media?

Answer 1

inhibits growth of unwanted microbes (only the selected microbes live)

Question 2

what is the definition of differential media?

Answer 2

allows organisms to grow but the added chemicals make them look different (they change different colors and/or precipitate is visible)

Question 3

what were the three specific plates that we used in our lab?

Answer 3

MSA: Mannitol salt agar
EMB: Eosin methylene blue
MAC: MacConkey agar

Question 4

where were the colors of the MSA, EMB, and MAC plates?

Answer 4

MSA: red
EMB: dark purple
MAC: raspberry

Question 5

which plate used in lab this semester was not selective or differential?

Answer 5

TSA

Question 6

which organisms used in this exercise are Gram + ?

Answer 6

Staphylococcus aureus
Staphylococcus epidermidis

Question 7

which organisms used in this exercise are Gram - ?

Answer 7

Escherichia coli
Enterobacter aerogenes
Proteus vulgaris

Question 8

How is MSA selective?

Answer 8

selects for gram +
selects against gram -

Question 9

how is EMB selective?

Answer 9

selects for gram -
selects against gram +

Question 10

how is MAC selective?

Answer 10

selects for gram -
selects against gram +

Question 11

How is MSA differential? (fermentation?)

Answer 11

differential for mannitol fermentation

Question 12

how is EMB differential? (fermentation?)

Answer 12

differential for lactose fermentation

Question 13

how is MAC differential? (fermentation?)

Answer 13

differential for lactose fermentation

Question 14

how is MSA differential? (color changes?/type of bacteria)

Answer 14

fermenter: growth turns yellow (Staphylococcus aureus)
nonfermenter: growth remains red (Staphylococcus epidermidis)

Question 15

how is EMB differential? (color changes?/type of bacteria)

Answer 15

strong fermenter: growth turns shiny metallic green (Escherichia coli)
weak fermenter: growth turns pink around the edges of colonies (Enterobacter aerogenes)
nonfermenter: growth remains dark purple (Proteus vulgaris)

Question 16

how is MAC differential? (color changes?/types of bacteria)

Answer 16

strong fermenter: entire plate turns bright pink (Escherichia coli)
weak fermenter: growth turns light pink with precipitate and background turns light brown (Enterobacter aerogenes)
nonfermenter: entire plate turns brown (Proteus vulgaris)