Bacterial degradation of 1,1-dichloro-2,2-bis(4-chlorophenyl)ethylene (DDE) has been previously reported, however, its degradation enzyme system has not been characterized. In this study, a DDE-degrading bacterium, Janibacter sp. TYM3221, was isolated and characterized. Transformation of DDE was demonstrated by TYM3211 resting cells grown in LB in the presence and absence of biphenyl. Gas chromatography-mass spectrometry analysis revealed five metabolites of DDE containing a meta-ring cleavage product and 4-chlorobenzoic acid, suggesting that TYM3221 degrades DDE to 4-chlorobenzoic acid via a meta-ring cleavage product. A gene cluster, bphAaAbAcAd, which codes for biphenyl dioxygenase subunits, was cloned from TYM3221. A mutant strain with a bphAa-gene inactivation did not grow on biphenyl, and showed no DDE degradation activity. These results indicate that in strain TYM3221, the bphAa-coded biphenyl dioxygenase is involved not only in the metabolism of biphenyl but also in the degradation of DDE.
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