The decarboxylase media, used to identify bacteria's ability to decarboxylate amino acids, were first introduced by Moeller for detecting lysine and ornithine decarboxylase and arginine dihydrolase among bacteria belonging to Enterobacteriaceae. The Moeller's basal media contained peptone, beef extract, bromocresol purple, cresol red, pyridoxal and glucose. To test decarboxylase activity, 1% of the appropriate amino acid was added. The medium was poured in narrow tubes as a column of about 2 cm in height and autoclaved, after which a layer of about 5 mm sterile paraffin oil was poured in each tube. The decarboxylase activity was measured on the basis of a pH rise of the amino acid reagent that was made visible by an indicator. After incubation the color changes in the tubes were followed for up to 10 days.
