Micro Lab 3

Question 1

Selective Media

Answer 1

• allows the growth of some organisms

- inhibits the growth of others

Question 2

differential media

Answer 2

• differentiates between closely related organisms or groups
• based on biochem characteristics

Question 3

sheep blood agar

Answer 3

• differential

- for bacterial hemolysins

Question 4

TSA

Answer 4

• non-selective

- non-differential

Question 5

MacConkey

Answer 5

• selective for gram negatives

- differential for ability to ferment lactose

Question 6

how MacConkey selective for gram negatives?

Answer 6

• bile salts and crystal violet inhibit growth of gram positive bacteria

Question 7

fermenter of lactose color

Answer 7

• pink

Question 8

mannitol salt agar

Answer 8

• selective for Staph
• differential for pathogenic staph
  
  • ferment mannitol

Question 9

color of fermented mannitol

Answer 9

• yellow

Question 10

triple sugar iron

Answer 10

• tests for sugar fermentation, sulfur reduction, and gas production simultanously

Question 11

glucose fermentation TSI

Answer 11

• rapid glucose fermentation decreases pH and turn media yellow
• red stant, yellow butt
• K/A

Question 12

fermentation of glucose and lactose/sucrose TSI

Answer 12

• yellow slant and butt

- A/A

Question 13

sulfur reducers TSI

Answer 13

• results in black precipitate

Question 14

non sugar fermenter TSI

Answer 14

• red stand and red butt
• utilized peptones only
• K/K

Question 15

MIO

Answer 15

• motility
• ornithine decarboxylase
• indole

Question 16

motility

Answer 16

• growth away from stab line

Question 17

ornithine decarboxylase

Answer 17

• enzyme turns L-orthnitine to putrescine

- causes pH to rise

Question 18

ornithine decarboxylase positive

Answer 18

• will turn medium purple at bottom

Question 19

indole

Answer 19

• tests for tryptonphanase
• converts tryptophan to indole
• required Kovac’s reaggen

Question 20

indole positive

Answer 20

• turns top layer red

Question 21

citrate utilization

Answer 21

• metabolism increases pH

- expression of citrate permease

Question 22

positive citrate utilization

Answer 22

• green to blue color change

Question 23

urease test

Answer 23

• hydrolyzes urea to ammonia and CO2

- NH3 increases pH

Question 24

urease positive

Answer 24

• will turn pink