EMB (Eosin Methylene Blue) Agar, Levine is a selective and differentiating medium for the isolation and identification of Gram-negativeEnterobacteriaceae. Pancreate Digest of Gelatin provides essential nutrients for bacterial growth and Dipotassium Phosphate is the pH buffer. Lactose is the fermentable carbohydrate. The dyes Eosin Y and Methylene Blue are toxic to most Gram-positive bacteria and serve as pH indicators. Rapid Lactose-fermenting microorganisms produce sufficient quantities of acid to shift the color of the pH indicators to dark purple.E.coliproduces a characteristic green metallic sheen. Non-fecal coliforms cannot ferment Lactose and form normally-colored or colorless colonies on this medium. Agar is the gelifying agent.