BIODEGRADATION OF DIBENZOTHIOPHENE BY A NODULATING ISOLATE OF RHIZOBIUM-MELILOTI

Rhizobium meliloti Orange 1 was isolated from aerobic sediments of a d rainage ditch receiving oil refinery leakage. This bacterium has been shown to be capable of growing on dibenzothiophene as the sole carbon and energy source. This strain can also efficaciously nodulate alfalfa plants. In cultures with dibenzothiophene, Orange 1 produces six degr adation intermediates. By means of analyses with UV-visible and CC-MS spectrometry, as well as nuclear magnetic resonance spectroscopy, thre e of these products were identified as 3-hydroxy-2-formyl-benzothiophe ne (product A), benzothienopyran-2-one (product B'), and dibenzothioph ene-5-oxide (product D). This suggests that R. meliloti Orange 1 metab olizes dibenzothiophene via oxidative cleavage of the aromatic ring wi th a mechanism analogous to that described for naphthalene degradation .