125. Given below are two statements:
Statement I: MacConkey agar is a media used for recovery of Gram positive bacteria from mixed
bacterial culture.
Statement II: The bile salts and crystal violet in MacConkey agar inhibit growth of some bacteria.
In the light of the above statements, choose the correct answer from the options given below :
A. Both Statement I and II are true and Statement II is the correct explanation of Statement I
B. Both Statement I and II are true but Statement II is not the correct explanation of Statement I
C. Statement I is true but Statement II is false
D. Statement I is false but Statement II is true

Detailed Explanation:

Statement I:

“MacConkey agar is a media used for recovery of Gram-positive bacteria from mixed bacterial culture.”

This statement is false.

• MacConkey agar is a selective and differential medium designed primarily to isolate Gram-negative enteric bacteria, particularly members of the Enterobacteriaceae family.

• It inhibits the growth of Gram-positive bacteria, making it unsuitable for their recovery.

Statement II:

“The bile salts and crystal violet in MacConkey agar inhibit growth of some bacteria.”

This statement is true.

• Bile salts and crystal violet are added specifically to suppress Gram-positive organisms, enhancing the selectivity for Gram-negative bacteria.

• This makes the medium effective for detecting lactose fermenters, such as E. coli, which turn the medium pink due to acid production.

✅ Correct Answer:

D. Statement I is false but Statement II is true