Phytoremediation, the use of plants to remove pollutants from the environment, holds great promise to reduce health risks associated with groundwater and soil contamination. It is widely recognized as an under utilized technology, and its successful application on a large scale will require continued input from basic research. Poplar trees could enhance site remediation via contaminant uptake and in-plant degradation, by minimizing off-site migration, or by enhancing microbial degradation in the rhizosphere. This project will characterize the microbial community beneath 7-year-old poplar trees. The hypothesis is that poplar roots exert selective pressure for the proliferation of microorganisms important to bioremediation. These include microorganisms capable of removing nitrate by denitrification, as well as microorganisms that can degrade carcinogens such as benzene or atrazine. Most Probable Number (MPN) techniques will be used to characterize and enumerate indigenous microorganisms with such specific traits. Viable plate techniques will be used to assess microbial diversity. Predominant microbial colonies will be isolated and identified using a BIOLOG system. Background soil will also be characterized to serve as a control for the root effect. Such information will contribute to the rational development of phytoremediation.