Selective Mediums

Question 1

What Temperature does the Autoclave reach?

Answer 1

121 C

Question 2

How does the Autoclave increase temp?

Answer 2

Hot Steam and Increased Pressure

Question 3

What does CFU stand for?

Answer 3

Colony Forming Unit

Question 4

What all should you label on a plate?

Answer 4

Medium Type, Date, Organism, Group Number, Section Number, Initials

Question 5

What does it mean for a medium to be Undefined?

Answer 5

Unknown exact recipe. Includes “digests”, “peptone”, “extracts”

Question 6

What does it mean for a medium to be Selective?

Answer 6

Medium will encourage some bacteria to grow and discourage/inhibit other bacterial growth. Can only tell you if an organism possesses a certain quality, can not identify an unknown organism.

Question 7

What does it mean for a medium to be Differential?

Answer 7

Medium can differentiate between two different organisms, can tell you what an unknown bacteria actually is.

Question 8

What does it mean for a medium to be Defined?

Answer 8

All chemical ingredients are known

Question 9

What are the 6 fundamental features of selective media?

Answer 9

1. Selective/Differential, Defined/Undefined
2. Nutritional Components
3. Inhibitors–make it selective
4. Substrates–make it differential
5. Indicators
6. Agar

Question 10

What kind of media is Phenylethyl Alcohol (PEA)?

Answer 10

Selective, Undefined

Question 11

What kind of organisms does PEA Media inhibit?

Answer 11

Inhibits Gram -

Selects for Gram +

Question 12

What part of PEA Media inhibits Gram - growth?

Answer 12

B-Phenylethyl Alcohol

Question 13

What kind of media is Mannitol Salt Agar (MSA)?

Answer 13

Selective, Differential, Undefined

Question 14

What kind of organisms does MSA Media grow?

Answer 14

Selects for Staphylococcus genus

Question 15

How is MSA Media selective?

Answer 15

High salt concentrations (Sodium Chloride). Staphylococcus is the only species that can survive in high salt concentration.

Question 16

How is MSA Media differential?

Answer 16

D-Mannitol is a Substrate. Staphylococcus aureus reacts with D-Mannitol and makes environment more acidic. The Phenol Red Indicator turns Yellow in Acidic environments. The Phenol Red Indicator stays Red in Basic environments.

Question 17

What kind of media is MaConkey Again (MAC)?

Answer 17

Selective, Differential, Undefined

Question 18

How is MAC Media Selective?

Answer 18

Bile Salts and Crystal Violet Dye Inhibit Gram + growth

Selects for Gram -

Question 19

How is MAC Media Differential?

Answer 19

Lactose is a Substrate. Lactose Fermentors will make the environment more Acidic. The Neutral Red Indicator is Colorless in Basic environments and Red in Acidic Environments.

Question 20

What kind of media is Eosin Methylene Blue Agar (EMB)?

Answer 20

Selective, Differential, Undefined

Question 21

What makes EMB Media Selective?

Answer 21

Eosin and Methylene Blue dyes encourage Gram - growth.

Question 22

What makes EMB Media Differential?

Answer 22

Lactose and Sucrose are Substrates. Fermentation makes environment more acidic, which changes color of Eosin and Methylene Blue. Shows Degree of Lactose use. How efficiently it ferments Lactose or Sucrose.

Question 23

Esherichia coli, Salmonella typhimurium, Enterobacter aerogenes

Answer 23

Gram -

Question 24

Staphylococcus aureus, Staphlococcus epidermitis, Enterococcus faecalis

Answer 24

Gram +