Eosin-methylene blue agar,or EMB,is a commonly used bacteriological medium in a lab,used to grow gram-negative bacteria.There are two dyes in it,eosin and methylene blue,as well as the sugar lactose.Eosin is a pH indicator that changes color when the medium is acidic,while methylene blue reduces the growth of most gram-positive bacteria.If an organism uses lactose,acid will be produced changing the pH of the medium and subsequently causing the bacterial colonies to change color.
Based upon this description,this medium is:

Question

Quizplus · Accepted Answer

EMB agar is both selective and differential. It is selective because it inhibits the growth of gram-positive bacteria, and it is differential because it distinguishes lactose fermenters, which change color due to acid production.

Eosin-Methylene Blue Agar,or EMB,is a Commonly Used Bacteriological Medium in a Lab,used