Degradation of dibenzothiophene sulphoxide and sulphone by Arthrobacter strain DBTS2

A natural isolate, Arthrobacter DBTS2, originally selected for growth on dibenzothiophene (DBT) sulphone was also able to grow on DBT-sulphoxide and less well on several other sulphur-containing aromatic compounds. Although it was unable to grow on naphthalene or biphenyl, the presence of either compound promoted the release of inorganic sulphur from DBT-sulphone. In addition, naphthalene induced oxygen uptake with DBT-sulphoxide as substrate, although it did not induce the oxidation of DBT-sulphone. The oxidation of DBT-sulphone was induced both by itself and by DBT-sulphoxide. The oxidation of these heterocyclic compounds by Arthrobacter DBTS2 was subject to catabolite repression by succinate or acetate, as is the case for other bacteria with an oxidatively oriented metabolism. Mutants of DBTS2 defective in growth on DBT-sulphone did not release inorganic sulphur from this compound, whereas mutants of DBTS2 defective in benzoate degradation released sulphur at rates similar to their parent.