Casein Plates contain the major milk protein found in milk. Organisms were grown on Casien agar for 72 hours at 37o C to look for the presence of the exoenzyme proteases/caseases . (A): Pseudomonas aeruginosa, casein hydrolysis, as noted by a zone of clearing around the organism, as well as a green diffusable pigment pyocyanin. (B): Serratia marcesens, casein hydrolysis as well as red colony pigment prodigiosin (C): E. coli, growth but no casein hydrolysis. Pigment production is a characteristic of the organisms and not influenced by the casein media.