The dibenzothiophene (DBT) desulfurizing operon, dsz, was introduced into various benzothiophene (BT)-desulfurizing bacteria using a Rhodococcus-E. coli shuttle vector. Of the tested recombinant bacteria, only those from Rhodococcus sp. strain T09 grew with both DBT and BT as the sole sulfur source. These recombinant cells desulfurized not only alkylated BTs, but also various alkylated DBTs, producing alkylated hydroxybiphenyls as the desulfurized products. Recombinant strain T09 also desulfurized alkylated DBT in an oil-water, two-phase resting-cell reaction. The dsz operon had the same desulfurizing activity when inserted into the vector in either orientation, indicating that the promoter region of the operon was functional in strain T09.