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Please use this identifier to cite or link to this item: http://hdl.handle.net/1942/10251

Title: Bacteria associated with oak and ash on a TCE-contaminated site: characterization of isolates with potential to avoid evapotranspiration of TCE
Authors: Weyens, Nele
Taghavi, Safiyh
Barac, Tanja
Van Der Lelie, Daniel
Boulet, Jana
Artois, Tom J.
Carleer, Robert
Vangronsveld, Jaco
Issue Date: 2009
Publisher: Springer
Abstract: Background, aim, and scope Along transects under a mixed woodland of English Oak (Quercus robur) and Common Ash (Fraxinus excelsior) growing on a trichloroethylene (TCE)-contaminated groundwater plume, sharp decreases in TCE concentrations were observed, while transects outside the planted area did not show this remarkable decrease. This suggested a possibly active role of the trees and their associated bacteria in the remediation process. Therefore, the cultivable bacterial communities associated with both tree species growing on this TCE-contaminated groundwater plume were investigated in order to assess the possibilities and practical aspects of using these common native tree species and their associated bacteria for phytoremediation. In this study, only the cultivable bacteria were characterized because the final aim was to isolate TCE-degrading, heavy metal resistant bacteria that might be used as traceable inocula to enhance bioremediation. Materials and methods Cultivable bacteria isolated from bulk soil, rhizosphere, root, stem, and leaf were genotypically characterized by amplified rDNA restriction analysis (ARDRA) of their 16S rRNA gene and identified by 16S rRNA gene sequencing. Bacteria that displayed distinct ARDRA patterns were screened for heavy metal resistance, as well as TCE tolerance and degradation, as preparation for possible future in situ inoculation experiments. Furthermore, in situ evapotranspiration measurements were performed to investigate if the degradation capacity of the associated bacteria is enough to prevent TCE evapotranspiration to the air. Results and discussion Between both tree species, the associated populations of cultivable bacteria clearly differed in composition. In English Oak, more species-specific, most likely obligate endophytes were found. The majority of the isolated bacteria showed increased tolerance to TCE, and TCE degradation capacity was observed in some of the strains. However, in situ evapotranspiration measurements revealed that a significant amount of TCE and its metabolites was evaporating through the leaves to the atmosphere. Conclusions and perspectives The characterization of the isolates obtained in this study shows that the bacterial community associated with Oak and Ash on a TCE-contaminated site, was strongly enriched with TCEtolerant strains. However, this was not sufficient to degrade all TCE before it reaches the leaves. A possible strategy to overcome this evapotranspiration to the atmosphere is to enrich the plant-associated TCE-degrading bacteria by in situ inoculation with endophytic strains capable of degrading TCE.
URI: http://hdl.handle.net/1942/10251
DOI: 10.1007/s11356-009-0154-0
ISI #: 000271398300007
ISSN: 0944-1344
Category: A1
Type: Journal Contribution
Validation: ecoom, 2010
Appears in Collections: Research publications

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