RECALCITRANCE OF 1,1-DICHLORO-2,2-BIS(P-CHLOROPHENYL)ETHYLENE TO DEGRADATION BY PURE CULTURES OF 1,1-DIPHENYLETHYLENE-DEGRADING AEROBIC-BACTERIA

1,1-Dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE) is the peri-chlorin ated derivative of 1,1-diphenylethylene (DPE). Biodegradation of DDE a nd DPE by bacteria has so far not been shown. Pure cultures of aerobic bacteria involved in biodegradation of styrene and polychlorinated bi phenyls (PCB) were therefore screened for their ability to degrade or cometabolize DPE and DDE. Styrene-metabolizing bacteria (Rhodococcus s trains S5 and VLB 150) grew with DPE as their sole source of carbon an d energy. Polychlorinated-biphenyl-degrading bacteria (Pseudomonas flu orescens and Rhodococcus globerulus) were unable to degrade DPE even i n the presence of an easily utilizable cosubstrate, biphenyl. This is the first report of the utilization of DPE as sole carbon and energy s ource by bacteria. All the tested bacteria failed to degrade DDE when it was provided as the sole carbon source or in the presence of the re spective degradable cosubstrates, DPE transformation could also be det ected in cell-free extracts of Rhodococcus S5 and VLB150, but DDE was not transformed, indicating that cell wall and membrane diffusion barr iers were not limiting biodegradation. The results of the present stud y show that, at least for some bacteria, the chlorination of DDE is th e main reason for its resistance to biodegradation by styrene and DPE- degrading bacteria.