Title: Evaluation of PCDD/PCDF Biodegration Using Bacterial Isolates from Contaminated Soils Authors
Submitted to: Dioxin Meeting
Publication Type: Proceedings
Publication Acceptance Date: July 13, 2010
Publication Date: August 30, 2010
Citation: Shelver, W.L., Huwe, J.K., Caesar, T. 2010. Evaluation of PCDD/PCDF biodegration using bacterial isolates from contaminated soils. 30th International Symposium on Halogenated Persistent Organic Pollutants (POPs), September 12-17, 2010, San Antonio, TX. Available:http://www.xcdtech.com/dioxin2010/pdf/1034.pdf. Interpretive Summary: A promising area to search for bacteria that are capable of degrading dioxins or dioxin related compounds is within contaminated sites since bacteria in such sites could have made adaptations allowing them to use the dioxins as energy sources. We identified several sites in southeast North Dakota that contains increased chlorinated dioxin/dibenzofurans concentrations in the soils. The identities of the dominant soil bacterial isolates were profiled based in their fatty acids pattern, morphology, and enzymes. The ability of the bacterial isolates to use dibenzofuran as an energy source was determined since these might be capable of degrading dioxins. The bacterial isolates that were capable of using dibenzofuran were amended into soils that contain highest dioxin concentrations from our survey to measure any changes in the chlorinated dioxins/dibenofurans. We found that the results were inconclusive and required further work to discover a dioxin consuming bacteria.
Technical Abstract: There is a need to identify bacteria that can degrade environmental contaminants and a potentially fruitful place to identify such bacteria is within contaminated soil. Dioxins from adjacent to railroad tracts were isolated by sonicating in acetone/toluene followed by alumina, tri-phase silica, and carbon column cleanup. An isotope dilution method following EPA method 1613 using high-resolution gas chromatography-high resolution mass spectrometry demonstrated these soils to have elevated polychlorinated dibenzo-p-dioxins (PCDDs) or dibenzofurans (PCDFs) levels. The predominant bacteria from two sites with elevated PCDDs/PCDFs contamination were isolated from whole soil and identified by cellular fatty acid profiling. A high proportion of Pseudomonas veroni and Pseudomonas fluorescens (biotype A and B) were found in the high dioxin contaminated sites compared to the low dioxin contaminated sites where Fluorescens putida appeared to predominate. P. fluorescens biotype A, P. mucidolens, P. savastanoi, P. veronii were able to use dibenzofuran as sole carbon source while P. fluorescens biotype B and P. putida were able to propagate using dibenzofuran as sole carbon source. Measurements of PCDDs/PCDFs in amended soil containing bacterial inoculates did not show consistent trends indicating that little or no degradation of the contaminants occurred under the conditions of the study.