Recent GTI Advances in Phytoremediation of Polycyclic Aromatic Hydrocarbons

摘要

Recent GTI research into phytoremediation of PAH-contaminated soils has centered on two areas. The first of these seeks to understand the enzymatic basis of PAH degradation by plants themselves; the second is to identify bacteria which are capable of simultaneously degrading PAH and stimulating plant growth. It is our long-term goal to combine these two facets into a synergistic approach, to provide an inexpensive, easily-executed in situ treatment for PAH-contaminated soils. We have identified root-secreted peroxidases in several species of plants (including, for example, alfalfa and wheat) which are capable, under the proper conditions, of oxidizing most priority pollutant PAHs. Although the precise mechanisms are not yet fully clear, our results indicate that PAH transformation may be best catalyzed through reactions mediated by, lipid peroxidation. We have also developed a rapid system, based on the hydroponic growth of seedlings and plants, to assess which species are capable of high-level, sustained production of these enzymes. This is significant in that it will allow rational selection of species for phytoremediation of PAHs based on a phenotype which is readily measurable. In the second focus area of our research, we have identified several PAH-degrading bacteria, from the genera Burkholderia and Sphingomonas, which are able, when inoculated into soil seeded with alfalfa, to serve as promoters of plant germination, survival, and/or growth. The mechanism of this phenomenon is currently under study; data thus far indicates that the PAH-degrading bacteria may exert these effects by suppression of fungal attack on seeds and seedlings, and by production of siderophores, compounds which increase the availability of soil iron for uptake by the host plant. We will soon be testing these bacteria to ascertain whether they are also able to enhance the growth of other plant species as well.