ex. 9 special media for isolating bacteria

Question 1

enrichment media

Answer 1

contain chemicals that enhance the growth of a desired bacterial species

Question 2

selective media

Answer 2

contain chemicals that inhibit the growth of unwanted while allowing the growth of the desired bacteria

Question 3

differential media

Answer 3

contain chemicals that cause bacterial colonies of the media itself to appear differently, depending on a particular characteristics of the bacteria species

Question 4

mannitol salt agar (MSA)

Answer 4

contains a high concentration of salt that inhibits the growth of most bacterial species, selecting for halotolerant (salt-tolerant) bacteria such as Staphylococcus species

Question 5

mannitol salt agar (MSA) contains what kind of mannitol and which ph indicator?

Answer 5

sugar mannitol

ph indicator phenol red

Question 6

if the halotolerant species growing on the manniol salt agar MSA plate can ferment mannitol what happens?

Answer 6

acid is produced, lowering the pH and causes indicator to turn the agar from red to yellow

Question 7

when can you NOT use mannitol salt agar (MSA)?

Answer 7

to determine if non-halotolerant bacteria can ferment mannitol because they cannot grow on the agar plate

Question 8

eosin methylene blue (EMB) contains what kind of lactose and dyes?

Answer 8

sugar lactose
dyes: eosin and methylene blue

Question 9

what do the dyes do in eosin methylene blue (EMB)

Answer 9

inhibit the growth of gram-positive bacteria thus selecting gram negative bacteria

Question 10

what happens if the gram negative can ferment lactose in eosin methylene blue (EMB)

Answer 10

the colonies will appear dark purpole, dark pink, or metallic green (according to the amount of acid produced)

Question 11

what happens if the gram negative does not ferment lactose in eosin methylene blue (EMB)

Answer 11

colonies appear colorless, creamy, or light pink

Question 12

what can you NOT determine using eosin methylene blue (EMB)

Answer 12

determine whether gram-positive bacteria ferment lactose because they cannot grow on the media

Question 13

for eosin methylene blue (EMB) you look at the color of the ______ to determine ____________

Answer 13

colonies
whether the gram negative bacteria can ferment lactose

Question 14

for mannitol salt agar (MSA) you look at the color of the _____ to determine _________

Answer 14

agar
whether the halotolerant bacteria can ferment mannitol