BI 127 Lab #18: Selective, Differential, and Enriched Media

MacConkey agar

Which differential medium is selective for Gram-negative bacteria and makes lactose-fermenting bacteria appear pink?

Gram-negative bacteria

MacConkey agar is selective for which type of bacteria?

Yes

Yes or no? MacConkey agar is a differential medium.

Pink or red bacterial growth

What would a positive result for lactose fermentation look like on a MacConkey agar plate?

Selective media

What type of media allow certain bacteria to grow while preventing other bacteria from growing?

Differential media

What type of media contain indicators that distinguish one bacterium from another?

Enriched media

What type of media contain extra nutrients and/or growth stimulants?

3

Which of the following is true of blood agar?

1. It is selective

2. It is enriched

3. It is both enriched and differential

4. It is differential

5. It is both differential and selective

Gram-positive bacteria

What organisms does MacConkey agar inhibit?

No

Yes or no? Blood agar is differential because different types of bacteria lyse red blood cells similarly.

a, b and d

Which of the following are true about mannitol salt agar (select all that apply).

a. It is selective

b. It is differential

c. It does not allow growth of Staphylococci

d. It has a pH indicator

6

MacConkey agar is selective because it contains:

1. mannitol and a pH indicator

2. lactose and a pH indicator

3. glucose and a pH indicator

4. low salt concentration

5. high salt concentration

6. bile salts and crystal violet

halotolerent bacteria

Salt is the component of mannitol salt agar that makes it selective for _______.

yellow; pink or red

Staphylococcus aureus will cause mannitol salt agar to be____(color), while most other Staphylococci will cause it to be______(color).