Eosin-methylene blue agar, or EMB, is a commonly used bacteriological medium for growing gram-negative bacteria from complex environments.It contains two dyes, 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 inhibits the growth of most gram-positive bacteria.If an organism consumes lactose, acid will be produced, causing the bacterial colonies to change color. Based upon this description, this medium is ______.

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Eosin-methylene blue agar is both differential and selective. It is selective because it inhibits the growth of gram-positive bacteria through the use of methylene blue. It is differential because it allows the differentiation of lactose-fermenting (pink to red colonies) from non-lactose fermenting (colorless colonies) gram-negative bacteria through the use of eosin as a pH indicator.

Eosin-Methylene Blue Agar, or EMB, Is a Commonly Used Bacteriological