Degradation of dibenzothiophene and carbazole by Arthrobacter sp. P1-1

Arthrobacter sp. P1-1 was isolated from a polycyclic aromatic hydrocarbon (PAH)-contaminated site in Hilo, HI, USA. This strain can degrade approximately 82% of dibenzothiophene (DBT) (40 mg l−1) and 57% of carbazole (CBZ) (40 mg l−1) in 14 days incubation. Dibenzothiophene-5,5′-dioxide was formed from sulfur oxidation of DBT. Dibenzothiophene diols that were transformed from 1,2- and 3,4-dioxygenations of DBT underwent ortho- and meta-ring cleavages to produce benzo[b]thiophene-2,3-dicarboxylic acid and hydroxyl-benzo[b]thiophene carboxylic acid, respectively. These products were converged into benzo[b]thiophene-2,3-diol, which was further transformed to 2,2′-dithiosalicylic acid via 2-mercaptobenzoic acid. These results indicate that strain P1-1 has diverse lateral dioxygenase systems and subsequent metabolic enzyme systems. The five detected CBZ metabolites by strain P1-1 were 4-(3-hydroxy-1H-indol-2-yl)-2-oxobut-3-enoic acid, 2-(2-carboxy-vinyl)-1H-indole-3-carboxylic acid, pyrido[1,2-a]indole-6,10-dione, indole-2,3-dicarboxylic acid, and 2-aminobenzoic acid. The results suggest that CBZ degradation underwent 3,4-dioxygenation followed by ortho- and meta-ring cleavage.