FORMATION OF INDIGO AND RELATED-COMPOUNDS FROM INDOLECARBOXYLIC ACIDSBY AROMATIC ACID-DEGRADING BACTERIA - CHROMOGENIC REACTIONS FOR CLONING GENES ENCODING DIOXYGENASES THAT ACT ON AROMATIC-ACIDS

The p-cumate-degrading strain Pseudomonas putida F1 and the m- and p-t oluate-degrading strain P. putida mt-2 transform indole-2-carboxylate and indole-3-carboxylate to colored products identified here as indigo , indirubin, and isatin. A mechanism by which these products could be formed spontaneously following dioxygenase-catalyzed dihydroxylation o f the indolecarboxylates is proposed. Indolecarboxylates were employed as chromogenic substrates for identifying recombinant bacteria carryi ng genes encoding p-cumate dioxygenase and toluate dioxygenase. Dioxyg enase gene-carrying bacteria could be readily distinguished as dark gr een-blue colonies among other colorless recombinant Escherichia coli c olonies on selective agar plates containing either indole-2-carboxylat e or indole-3-carboxylate.