Terpene-utilizing isolates and their relevance to enhanced biotransformation of polychlorinated biphenyls in soil

Abstract

Orange peels, eucalyptus leaves, pine needles and ivy leaves were addedseparately to soil spiked with Aroclor 1242 (100 mgkg^-1.Polychorinated biphenyls (PCBs) disappeared after six months in all theamended soils, but not in unamended soils. Although biphenyl was not addedto any of the soils, all four amended soils had much higher levels(10⁸/g) of biphenyl-utilizing bacteria than the unamendedcontrol (10³/g). Ten random isolates obtained from these soilswere identified as coryneform bacteria. Five isolates, that were distinctlydifferent, were studied further with respect to growth on pure terpenes andmetabolism of PCBs. The most effective strains were Cellulomonas sp. T109and R. rhodochrous T100, which metabolized 83% and 80% ofAroclor 1242, respectively, during a six day period of growth on cymene andlimonene, respectively. The bphA gene, cloned as a 2.8 Kb Sa/I fragment ofpAW6194 from cbpA (Walia et al. 1990) hybridized to total DNA of allcoryneform isolates, and to the well-established PCB degrader Rhodococcusgloberulus. In contrast, a 5 Kb XhoI-SmaI fragment of the bphA gene(Furukawa & Miyazaki 1986) did not show any homology to the genomic DNAof any of the isolates or to R. globerulus, but did hybridize to two otherwell-known PCB degraders Pseudomonas sp. LB400, and Alcaligenes eutrophusH850. The data presented herein indicate that terpenes may be naturalsubstrates for biphenyl-degrading bacteria and may enhance substantialtransformation of Aroclor 1242.