Rhizoremediation of trichloroethylene by a recombinant, root-colonizing Pseudomonas fluorescens strain expressing toluene ortho-monooxygenase constitutively.
Trichloroethylene (TCE) was removed from soils by using a wheat rhizosphere established by coating seeds with a recombinant, TCE-degrading Pseudomonas fluorescens strain that expresses the tomA+ (toluene o-monooxygenase) genes from Burkholderia cepacia PR1(23)(TOM23C). A transposon integration vector was used to insert tomA+ into the chromosome of P. fluorescens 2-79, producing a stable strain that expressed constitutively the monooxygenase at a level of 1.1 nmol/min.mg of protein (initial TCE concentration, 10 microM, assuming that all of the TCE was in the liquid) for more than 280 cell generations (36 days). We also constructed a salicylate-inducible P. fluorescens strain that degraded TCE at an initial rate of 2.6 nmol/min.mg of protein in the presence of 10 microM TCE [cf. B. cepacia G4 PR1(23) (TOM23C), which degraded TCE at an initial rate of 2.5 nmol/min.mg of protein]. A constitutive strain, P. fluorescens 2-79TOM, grew (maximum specific growth rate, 0.78 h-1) and colonized wheat (3 x 10(6) CFU/cm of root) as well as wild-type P. fluorescens 2-79 (maximum specific growth rate, 0.77 h-1; level of colonization, 4 x 10(6) CFU/cm of root). Rhizoremediation of TCE was demonstrated by using microcosms containing the constitutive monooxygenase-expressing microorganism, soil, and wheat. These closed microcosms degraded an average of 63% of the initial TCE in 4 days (20.6 nmol of TCE/day.plant), compared to the 9% of the initial TCE removed by negative controls consisting of microcosms containing wild-type P. fluorescens 2-79-inoculated wheat, uninoculated wheat, or sterile soil.
Yee
D C
DC
Department of Chemical and Biochemical Engineering, University of California, Irvine 92697-2575, USA.
Maynard
J A
JA
Wood
T K
TK
D001673:Biodegradation, Environmental; D016956:Burkholderia cepacia / Q000235:genetics; D002876:Chromosomes, Bacterial / Q000235:genetics; D004251:DNA Transposable Elements; D015870:Gene Expression; D006899:Mixed Function Oxygenases / Q000235:genetics* / Q000378:metabolism; D016254:Mutagenesis, Insertional; D018517:Plant Roots / Q000382:microbiology*; D010957:Plasmids; D011551:Pseudomonas fluorescens / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D011995:Recombination, Genetic; D015183:Restriction Mapping; D012639:Seeds / Q000382:microbiology; D012988:Soil Microbiology; D014241:Trichloroethylene / Q000378:metabolism*; D014908:Triticum / Q000382:microbiology
D004251:DNA Transposable Elements; D014241:Trichloroethylene; D006899:Mixed Function Oxygenases; C093480:toluene ortho-monooxygenase