Carbazole degradation by Pseudomonas sp LD2: Metabolic characteristics and the identification of some metabolites

A carbazole-degrading bacterium was isolated by enrichment from a creosote-contaminated soil. This organism, designated Pseudomonas sp. LD2, utilized carbazole as a sole source of carbon, nitrogen, and energy. When isolate LD2 was grown in nitrogen-free mineral medium with C-14-labeled carbazole, 43% was recovered as (CO2)-C-14 after 3 days of incubation. Numerous aromatic and heterocyclic compounds were tested as growth substrates for isolate LD2, but few supported the growth of this bacterium. Anthranilic acid and catechol served as growth substrates and were positively identified as intermediates of carbazole degradation by isolate LD2. In addition, 10 nitrogen-containing metabolites were observed in acidified extracts of LD2 culture supernatants, four of which were unequivocally identified. These included indole-3-acetic acid, 5-(2-aminophenyl)-5-oxopentanoic acid, and the cyclized products of 5-(2-aminophenyl)5--oxopent-3-enoic acid and 6-(2-aminophenyl)-2-hydroxy-6-oxohexa-2,4-dienoic acid.