Ca. Lajoie et al., DEVELOPMENT OF FIELD APPLICATION VECTORS FOR BIOREMEDIATION OF SOILS CONTAMINATED WITH POLYCHLORINATED-BIPHENYLS, Applied and environmental microbiology, 59(6), 1993, pp. 1735-1741
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.