Degradation of Carboxydiphenyl Ether via Bioaugmentation
Rolf U. Halden, (S.M.ASCE),
Barbara G. Fischer,
Daryl F. Dwyer,
Two diphenyl ether-degrading bacteria, Pseudomonas pseudo-alcallgenes
strain POB31O and P. sp.
strain B13-D5, were inoculated into lake sediment to which 3-carboxydiphenyl ether (CDE, 10 ppm) had been added. B13-D5 was constructed from P. sp.
strain B13, a bacterium noted to survive in a variety of environments, by introduction of the genes that encode carboxydiphenyl ether dioxygenase. This enzyme is responsible for the initial cleavage of the ether bond of CDE; the genes were obtained from POB310 where they exhibit poor stability. Cell densities in lake sediments were periodically measured to assess bacterial survival; concurrently, concentrations of CDE were measured to determine whether the presence of either strain resulted in an increase in the rate and extent of removal of CDE. By comparison, viable B13-D5 persisted at higher densities over a longer period of time than did POB31O; in addition, CDE was removed more rapidly and to a greater extent in sediments to which B13-D5 had been introduced. On the basis of these results, we suggest that bacterial strains selected for survival and modified for stable expression of degradative functions (e.g.
strain B13-D5) may serve as better agents for in situ
bioremediation via bioaugmentation than naturally-occurring strains having the same degradative functions. Subject Headings: Bacteria
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