Phytoremedation is the use of plants and plant/microbe combinations to cheaply clean toxic spills through natural processes. We're working on a specific type of plant/microbe combination, the ectomycorrhizal symbiosis. Ectomycorrhizae are formed by the symbiotic relationship between certain groups of plants (for example California natives such as oaks, willows and pines) and fungi that evolved from those that break down wood, which is high in phenolic compounds. Our research is based on utilizing the natural ability of fungi in this symbiosis to oxidize contaminants based on phenol, such as polycyclic aromatic hydrocarbons (PAH) and polychlorinated benzenes (PCB), and also raw diesel. We have been answering 2 questions. A), how can we increase the efficiency of this naturally-occurring phenomenon? B), which microbes can we use that are specifically adapted to and grow well under chemical conditions created in contaminated soils? 

A) How can we quickly and easily increase the efficiency of naturally-occurring bioremedation agents? Ectomycorrhizae are produced by fungi that infiltrate plant roots. In this relationship, the plant gets its nitrogen from the fungus which breaks down phenolic-based compounds in the soils, and the fungus gets it's sugars from that are produced by photosynthesis. Neither partner can survive alone. Our rationale was that if the sugars from the plant were reduced by decreasing how much they could make through phtosynthesis, the fungi might increase their production of enzymes to get their sugars from the surrounding soil, which is very high in phenolic-based compounds. Our method of decreasing photosynthetic capacity was partial defoliation of the plant partner, in this case a pine tree. Our data indicate that we could indeed get the fungal partners to up-regulate their enzyme productions, by up to 10-fold in some cases. This increase occurs whether the defoliation is induced purposely (e.g.,1) or naturally through factors such as disease (e.g., 2). Because we are working in a natural ecosystem, not only do these studies provide fungi and fungal enzymes for remediation, but they also provide organisms that can be used in space flight for waste recycling. Further, our data changed the way we look at symbiosis in general, and provided new data for use in climate change models, Thus, this work is of interest to NASA Earth Sciences and Space Life Support and Sustainability, and also to the broader scientific community.

Applications At Ames: Our data provide a solution to soil contamination that is both cheap, and aesthetically pleasing, and also serves to restore Base habitat. This can be done through restoration of na�ve plant communities that naturally possess the proper microbial associations (such as oak or scrub oak) or through the utilization of ornamental plants already present on base (such as the pines) to act as the phytoremediation agents, in conjunction with increasing the rate of remediation by up to 10-fold by simply removing half the leaves or needles. Remediation will occur well beyond the range of the plant�s roots as the fungal structures (hyphae) can extend far beyond the roots. In fact, the largest living organism is a fungus, and the hyphae from a single individual can cover over 2000 acres. 

Using enzymes from fungi identified by our above experiments we are providing "parent enzymes" that can be used and/or engineered with greater efficiency under the conditions required for enzyme function in contaminated soil and water. The enzymes we purify in our NSF-funded study will be utilized in partnership with Chad Paavola in the SCB group at Ames, and with the Industrial Sustainable Design group of SCION, a Crown Research Institute of New Zealand to engineer enzymes and enzyme complexes with higher activity. One exciting project is to construct a protein/enzyme combination termed a Rosettasome (pictured) so named because of its Rosetta Stone quality. It is comprised of a protein base upon which different enzymes (in blue) can be placed. The type of enzymes and their physical arrangement can be custom fit to the contaminant of choice. Thus, this is a flexible platform with nearly endless application. It could be applied directly to soils or surfaces, or fixed to a filter through which contaminated groundwater could be pumped. Thus, it will have wide-ranging application to Ames, and to many contaminated systems. We have just submitted a proposal to NSF for further extramural funding for this project.