Indigenous bacteria from poplar tree (Populus canadensis var. eugenei `Imperial Carolina') and southern California shrub rhizospheres, as well as two tree-colonizing Rhizobium strains (ATCC 10320 and ATCC 35645), were engineered to express constitutively and stably toluene o-monooxygenase (TOM) from Burkholderia cepacia G4 by integrating the tom locus into the chromosome. The poplar and Rhizobium recombinant bacteria degraded trichloroethylene at a rate of 0.8 to 2.1 nmol/min/mg of protein and were competitive against the unengineered hosts in wheat and barley rhizospheres for 1 month (colonization occurred at a level of 1.0 × 105 to 23 × 105 CFU/cm of root). In addition, six of these recombinants colonized poplar roots stably and competitively with populations as large as 79% ± 12% of all rhizosphere bacteria after 28 days (0.2 × 105 to 31 × 105 CFU/cm of root). Furthermore, five of the most competitive poplar recombinants (e.g., Pb3-1 and Pb5-1, which were identified as Pseudomonas sp. strain PsK recombinants) retained the ability to express TOM for 29 days as 100% ± 0% of the recombinants detected in the poplar rhizosphere expressed TOM constitutively.


Civil, Architectural and Environmental Engineering


E.I. du Pont de Nemours & Company
National Science Foundation (U.S.)

Keywords and Phrases

Indigenous Bacteria; Poplar and Rhizobium Recombinant Bacteria; Poplar tree; Southern California shrub rhizospheres; Toluene o-monooxygenase (TOM)

International Standard Serial Number (ISSN)


Document Type

Article - Journal

Document Version

Final Version

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© 2000 American Society for Microbiology, All rights reserved.

Publication Date

01 Nov 2000