The 3M™ Petrifilm™ Aerobic Count (AC) Plate is a ready-made culture medium system that contains nutrients, a cold-water-soluble gelling agent, and an indicator dye that makes colonies easier to see. Petrifilm plates are manufactured with a grid background to facilitate counting colonies. Petrifilm AC plates can be used in place of standard nutrient media such as Luria broth agar plates, nutrient agar plates, or trypticase soya agar plates in many applications