The nitrogen, vitamin, and carbon sources are provided by Beef Extract and Peptone in MYP Agar Base. D- Mannitol is the carbohydrate source, and fermentation is detected by the pH indicator Phenol Red. Bacteria that ferment Mannitol result in acid production and produce yellow colonies; B. cereus is typically Mannitol negative and result in pink colonies. Sodium Chloride maintains the osmotic environment. Agar is the solidifying agent. Supplementing with Egg Yolk Emulsion provides Lecithin. B. cereus produces Lecithinase which hydrolyzes the Lecithin from the Egg Yolk and forms a zone of white precipitation around the colonies (halo). Polymyxin B (50,000 IU) solution inhibits the growth of most other bacteria.