A Rapid, Unequivocal Method for Detecting Glutamic Acid Decarboxylase in Primary Plate Cultures of Enterobacteriaceae

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Abstract
Summary: In a rapid technique for detecting L‐glutamic acid decarboxylase activity in lactose fermenting colonies growing on purple MacConkey's agar the colonies, after exposure to toluene vapour for 30 min, are removed from the agar surface with small filter paper discs and allowed to act on a buffered substrate containing 1% of L‐glutamic acid for 1 h. The amino acids are extracted from the disc with a small drop of water and separated by paper chromatography in 1–3 h. A considerable increase in decarboxylase activity was produced by exposing the cells to toluene vapour. Pyridoxal‐5‐phosphate in the substrate also stimulated activity to a lesser degree.