Aerobic biodegradation of disulfides produced from dibenzothiophene metabolites

Dibenzothiophene (DBT) is a sulfur heterocycle in petroleum. When DBT is degraded through the Kodama pathway, the likely route of DBT biodegradation in petroleum-contaminated environments, three large disulfides are formed. 2-Oxo-2-(2-thiophenyl)ethanoic acid disulfide (disulfide C), 2-oxo-2-(2-thiophenyl)ethanoic acid 2-benzoic acid disulfide (disulfide D), and 2,2'-dithiosalicylic acid (disulfide E), can be detected using high performance liquid chromatography. Soil from near marigold roots contained microorganisms that degraded disulfide C, but the enrichments lost activity upon transfer. Two isolates, strains RM1 and RM6, were capable of degrading disulfide E in combination. Isolate RM1 likely provided vitamin B12 to isolate RM6. Benzoic acid was identified as a metabolite in the biodegradation of disulfide E by isolate RM6. Isolate RM6 was identified as a member of the genus Variovorax and mineralized disulfide E. Combining Variovorax sp. strain RM6 with Pseudomonas sp. strain BT1d, which degrades DBT through the Kodama pathway, did not release sulfate from DBT.