Grantee Research Project Results

Microbial Community Composition and Organic Carbon Cycling Processes of Permanently Cold Marine Sediments

EPA Grant Number: U915921
Title: Microbial Community Composition and Organic Carbon Cycling Processes of Permanently Cold Marine Sediments
Investigators: Powell, Sabrina N.
Institution: University of North Carolina at Chapel Hill
EPA Project Officer: Lee, Sonja
Project Period: January 1, 2001 through January 1, 2004
Project Amount: $81,715
RFA: STAR Graduate Fellowships (2001) RFA Text |  Recipients Lists
Research Category: Fellowship - Aquatic Ecology and Ecosystems , Fellowship - Oceanography , Academic Fellowships

Objective:

The objective of this research project is to use stable isotope probing to test the hypothesis that salicylate is an effective inducer of specific polycyclic aromatic hydrocarbon (PAH) degradation. Linking the identity of bacteria with their function in the natural environment constitutes a major challenge for environmental scientists. Recent advances in microbial ecology have coupled stable isotope abundance in biomarkers with molecular techniques to study microbially mediated processes in complex environmental samples. Stable isotope probing offers a new tool for investigating the relationship between structure and function in microbial communities. Growth on a ¹³C-labeled compound results in the labeling of cell biomass, including nucleic acids. Following separation of labeled DNA from unlabeled DNA by ultracentrifugation, molecular techniques give insight into the identities of the organisms using the labeled substrate.

Approach:

PAHs are pollutants commonly found at high concentrations in contaminated industrial sites, such as wood-treating facilities and petroleum processing plants. PAHs consist of fused benzene molecules, ranging from two to six rings. Several of the higher molecular weight (HMW) PAHs are carcinogens. Bioremediation is an attractive cleanup technique for contaminated sites because of its low cost. However, degradation rates of HMW PAHs often are extremely slow. The addition of salicylate, a compound which is both an inducer of biodegradative enzymes and a metabolic intermediate in many PAH degradation pathways, has been proposed as a mechanism to stimulate PAH biodegradation. ¹³C-labeled salicylate and PAHs (naphthalene and phenanthrene) are offered as growth substrates to a microbial community capable of degrading PAHs, resulting in DNA of salicylate utilizers and PAH degraders being labeled with ¹³C. Following ultracentrifugation, denaturing gradient gel electrophoresis and clone libraries are being used to characterize the organisms capable of utilizing each compound. If salicylate is found to be an effective inducer of PAH degradation (i.e., if the salicylate degraders found are substantially similar to the PAH degraders), future work will investigate the effects of long-term exposure to salicylate and optimize the method of salicylate addition.

Supplemental Keywords:

fellowship, polycyclic aromatic hydrocarbons, PAHs, organic carbon cycling, marine sediments, biodegradation, pollutants, bioremediation, naphthalene, phenanthrene, salicylate degraders, wood-treating facilities, petroleum processing plants.

Progress and Final Reports:

2001

2002

Final