Department of Environmental Sciences
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Seminar Abstracts
Environmental Sciences Seminar Abstract            

  ENVIRONMENTAL IMPACT OF HYDROXYLATED METABOLITES OF POLYCHLORINATED BIPHENYLS (PCBS)
Benoit Van Aken
Temple University

Hydroxylated PCBs (OH-PCBs) are key metabolites generated by a variety of organisms and they are increasingly considered as a new class of environmental contaminants. The toxicity and estrogenicity of 22 mono-hydroxylated PCBs and their parent compounds were tested using the Microtox(R) microbial bioluminescent assay and yeast estrogen screen (YES) assay. Microtox(R) assay results showed that all hydroxylated derivatives tested exhibited a recordable toxicity at the concentration of 50 mg L-1 although only three lesser-chlorinated parent PCBs exhibited a detectable toxicity at this concentration. Linear relationships were observed between the effective concentration 50% (EC50) and octanol-water partition coefficient (Kow) for different series of OH-PCBs. YES assay results showed that 17 OH-PCBs showed a recordable estrogenicity, while parent PCBs showed no or low estrogenicity.

The metabolism of selected OH-PCBs by the PCB-degrader Burkholderia xenovorans LB400 was investigated showing differential biodegradation rates depending on the position of the OH group. Of the three mono-hydroxylated isomers of 4-chlorobiphenyl (PCB3) tested, only 2'-OH-PCB3 was significantly transformed. Consistently with these results, gene expression experiments using reverse-transcriptase real-time PCR showed overexpression of biphenyl dioxygenase gene (bphA) upon exposure of strain LB400 to 2'-OH-PCB3, while other isomers resulted in downregulation of bphA. These findings may provide partial explanation for the persistence of PCBs in the environment.


Last updated: 10/25/2011