[Mechanism of specific chromogenic reaction by Klebsiella spp. on nutrient medium with 5-aminosalicylic acid].

The nature of the factor and the mechanism of color reaction with 5-aminosalicylic acid (5-ASA) inherent in bacteria of the genus Klebsiella were investigated. The color reaction was shown to proceed in two stages. During the first stage, occurring in aerobic and anaerobic conditions, the tested strains of Klebsiella decarboxylize 5-ASA yielding CO2 and p-aminophenol, which is a colorless product. During the next strictly aerobic stage which proceeds without participation of bacteria or their exoenzymes, p-aminophenol is oxidized by the air oxygen forming the dark-brown polymers. The color reaction shows high substrate specificity. It is suggested that the color reaction is realized by a previously unknown lyase-type enzyme 5-aminosalicylate decarboxylase (5-aminosalicylate-carboxy-lyase) localized inside the Klebsiella cells.