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

Orange peels, eucalyptus leaves, pine needles and ivy leaves were added separately to soil spiked with Aroclor 1242 (100 mgkg(-1)). Polychorinated biphenyls (PCBs) disappeared after six months in all the amended soils, but not in unamended soils. Although biphenyl was not added to any of the soils, all four amended soils had much higher levels (10(8)/g) of biphenyl-utilizing bacteria than the unamended control (10(3)/g). Ten random isolates obtained from these soils were identified as coryneform bacteria. Five isolates, that were distinctly different, were studied further with respect to growth on pure terpenes and metabolism of PCBs. The most effective strains were Cellulomonas sp. T109 and R. rhodochrous T100, which metabolized 83% and 80% of Aroclor 1232, respectively, during a six day period of growth on cymene and limonene, respectively. The bphA gene, cloned as a 2.8 Kb Sa/I fragment of pAW6194 from cbpA (Walia et al. 1990) hybridized to total DNA of all coryneform isolates, and to the well-established PCB degrader Rhodococcus globerulus. In contrast, a 5 Kb XhoI-SmaI fragment of the bphA gene (Furukawa & Miyazaki 1986) did not show any homology to the genomic DNA of any of the isolates or to R. globerulus, but did hybridize to two other well-known PCB degraders Pseudomonas sp. LB400, and Alcaligenes eutrophus H850. The data presented herein indicate that terpenes may be natural substrates for biphenyl-degrading bacteria and may enhance substantial transformation of Aroclor 1242.