Molecular analysis of PCB-degradative gene expression induced by plant terpenes

초록

Polychlorinated biphenyls (PCBs) have been used widely for various industrial purposes but strictly regulated because of their potential toxicity (e. g.,. mutagenicity, endocrine disruption, etc.), An important aspect for effective bioremediation of PCBs is the induction of the catabolic pathway by natural substrates, instead of biphenyl which in itself is listed as a priority pollutant by the USEPA. Under aerobic conditions, two critical dioxygenases are important in cleavage of the benzene ring : biphenyl dioxygenation (encoded by bphA) and ring fission of dihydroxybiphenyl by dioxygenation (encoded by bphC). Recently, plant terpenes (e. g., carvone and limonene) were shown to stimulate PCB biodegradation. The following study was carried out to investigate the gene expression by PCB degraders under a terpene inducing condition. The result showed that both degraders induced by carvone appears to degrade 4, 4'-dichlorobiphenyl through ortho and meta ring cleavage pathways, respectively. The gene expression Alcaligenes sp. was monitored by reverse transcriptase polymerase chain reaction (RT-PCR) utilizing primers derived from bphC gene of Arthrobacter sp., in which mRNA of the bphC gene induced by carvone was observed. The gene expression in Arthrobacter sp., was also assayed using degenerate primers based upon a conserved bphC or A gene region. This molecular analysis technology will contribute to rapid monitoring an optimization of an effective PCB bioremediation process utilizing terpenes as a natural substrate that are readily available in the environment.