Microflora Involved in Phytoremediation of Polyaromatic Hydrocarbons

EPA Grant Number: R827015-01-0
Title: Microflora Involved in Phytoremediation of Polyaromatic Hydrocarbons
Investigators: David P. Nagle, John S. Fletcher
Institution: University of Oklahoma
EPA Project Officer: Bala Krishnan
Project Period: August 1, 2000 to July 31, 2001 (N/C Ext. August 1, 2001 to July 31, 2002)
Project Amount: $88,979
Research Category: Phytoremediation

Description:

RESEARCH GOAL:

Develop molecular techniques to monitor the presence and activity of polyaromatic-degrading communities of microorganisms in the rhizosphere.

WORK COMPLETED

(Sept. 1 to Nov. 30, 2000)
  1. The project was officially initiated on Sept. 1, 2000, the date marking the first expenditure of approved IPEC funds.
  2. The PI reviewed the chemical and microbial data that had been collected and analyzed on samples collected at the Union Carbide Texas City Plant between Jan. 1996 and Sept. 1, 2001. Additional statistical analyses of existing data was conducted with SPSS software program.
  3. Different DNA extraction methods were examined to recover DNA from soil samples.
  4. Different PCR primers were tested to amplify DNA coding for the nah genes, important in PAH and perhaps PCB degradation.
  5. Comparative analyses were conducted on microbial counts and preliminary PCR data collected on the same core samples removed from increasing depths in mulberry and Bermuda grass rooting zones.
  6. Initial efforts were made to develop a means to quantify PCR products.

RESULTS

  1. The total number of total bacteria in the root zone of mulberry and Bermuda grass is statistically the same.
  2. The number of PAH degrading bacteria in the root zone of mulberry on the average was 7-fold greater than that in the root zone of Bermuda grass.
  3. DNA coding for the nah genes has been extracted from the root zones of both mulberry and Bermuda grass and successfully used in PCR studies.
  4. The root zone of mulberry was a more plentiful source of nah genes in comparison to the root zone of Bermuda grass, a result that was consistent with the numbers of PAH-degrading organisms cultured from each root zone.

SIGNIFICANCE

To our knowledge this is the first research effort to use PCR technology to compare the enzymatic potential of rhizospheres of different plant species. Further development of this method with improved primers and better laboratory equipment should make it possible to conduct quantitative PCR analysis on field samples for different genes controlling the enzymatic degradation of PAHs and PCBs. Success in this regard will make it possible to quantify the total enzymatic potential of rhizosphere systems to degrade PAHs and/or PCBS over time, including microbes that have not to date been successfully cultured in the laboratory (>80% of soil species).

PUBLIC COMMUNICATION OF RESULTS

Four phytoremediation papers were presented a the IPEC Meeting held in Albuquerque, NM in Nov., 2000 by individuals from this laboratory.