Enzymatic Digest of Gelatin is the nitrogen source in EMB Agar, Levine. Lactose is the carbohydrate and Dipotassium
Phosphate is the buffer. Eosin Y and Methylene Blue are the indicators. Methylene Blue is also a selective agent. During
strong acidic conditions, the dyes impart a metallic sheen to certain lactose fermenters, such as E. coli.