Selective for the growth of gram negative bacteria. Inhibits the growth of gram positive bacteria via desoxycholate. Differential; the carbohydrates lactose, sucrose, and xylose are present. Organisms that ferment xylose will acidify the medium and turn it yellow. Organisms capable of removing the carboxyl group from L-lysine will produce alkaline products and turn the medium red. Organisms capable of reducing sulfur will produce a black precipitate due to H2S presence. Used to isolate Shigella and Providencia, which appear red on the medium. Salmonella would have a black precipitate.