Biodegradation of dibenzothiophene and 4,6-dimethyldibenzothiophene by Sphingomonas paucimobilis strain TZS-7

Strain TZS-7, tentatively identified as Sphingomonas paucimobilis, was isolated from crude oil for its ability to degrade dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-dmDBT). This strain did not utilize DBT or 4,6-dmDBT as the sole source of sulfur. However, the degradative activity was induced by various aromatic compounds, including DBT, fluorene, anthracene, naphthalene and toluene. Three products formed from 4,6-dmDBT degradation were detected and two of these were proposed to be 7-methyl-3-hydroxy-2-formylbenzothiophene and 7-methylbenzothiophene-2,3-dione by gas chromatography-mass spectrometry analysis. These findings proved that 4,6-dmDBT is degraded through a ring-destructive pathway by resting cells of strain TZS-7.