Numerous purified and characterized sulfate-reducing bacteria and bacterial communities isolated from oil-field production facilities were shown to convert dibenzothiophene (DBT) into biphenyl (BP). The maximum degree of conversion to biphenyl was 1.14% and 0.39% for purified sulfate-reducing bacteria and community bacteria, respectively. The purified sulfate-reducing bacteria and bacterial communities were identified by 16S rRNA ribotyping.