Phenylalanine Malonate Broth , Shaw and Clarke Medium

Phenylalanine Malonate Brot, Shaw and Clarke Medium is used for differentiation of members of Enterobacteriaceae on the basis of their ability to utilize malonate and produce pyruvic acid from phenylalanine. Organisms like Klebsiella and Salmonella arizonaeutilize malonate, produce an alkaline reaction and change the colour of the medium from light green to dark blue due to the pH indicator bromothymol blue. The colour of the medium remains light green if the organisms are malonate negative. Members of the group Proteus and Providencia are capable of deaminating phenylalanine to pyruvic acid.This reaction can be determined by the addition of few drops of 10% ferric chloride dissolved in acidified distilled water to a freshly grown culture. Deep green colour is formed due to production of pyruvic acid from phenylalanine.