DEVELOPMENT OF FIELD APPLICATION VECTORS FOR BIOREMEDIATION OF SOILS CONTAMINATED WITH POLYCHLORINATED-BIPHENYLS

Field application vectors (FAVs), which are a combination of a selecti ve substrate, a host, and a cloning vector, have been developed for th e purpose of expressing foreign genes in nonsterile, competitive envir onments in which the gene products provide no advantage to the host. S uch gene products are exemplified by the enzymes for the cometabolism of polychlorinated biphenyls (PCBs) through the biphenyl degradation p athway. Attempts to use highly competent PCB-cometabolizing strains in the environment in the absence of biphenyl have not been successful, while the addition of biphenyl is limited by its human toxicity and lo w water solubility. Broad-substrate-specificity PCB-degradative genes (bphABC) were cloned from a naturally occurring isolate, Pseudomonas s p. strain ENV307, into broad-host-range plasmid pRK293. The resulting PCB-degrading plasmids were transferred to the FAV host Pseudomonas pa ucimobilis 1IGP4, which utilizes the nontoxic, water-soluble, nonionic surfactant Igepal CO-720 as a selective growth substrate. Plasmid sta bility in the recombinant strains was determined in the absence of ant ibiotic selection. PCB-degrading activity was determined by resting ce ll assays. Treatment of contaminated soil (10, 100, or 1,000 ppm of Ar oclor 1242) by surfactant amendment (1.0% [wt/wt]Igepal CO-720 in wet soil) and inoculation with recombinant isolates of strain 1IGP4 (appro ximately 4 x 10(6) cells per g of soil) resulted in degradation of man y of the individual PCB congeners in the absence of biphenyl. Further improvements, including the use of non-antibiotic-resistance cloning v ectors, addition of the bphD gene, and chromosomal integration of the PCB-degradative genes, may ultimately result in FAVs useful for both r eactor-contained and in situ treatment of the partially dechlorinated PCBs often found in contaminated soils and sediments.