Potential of the TCE-degrading endophyte Pseudomonas putida W619-TCE to improve plant growth and reduce TCE phytotoxicity and evapotranspiration in poplar cuttings.
ABSTRACT The TCE-degrading poplar endophyte Pseudomonas putida W619-TCE was inoculated in poplar cuttings, exposed to 0, 200 and 400 mg l(-1) TCE, that were grown in two different experimental setups. During a short-term experiment, plants were grown hydroponically in half strength Hoagland nutrient solution and exposed to TCE for 3 days. Inoculation with P. putida W619-TCE promoted plant growth, reduced TCE phytotoxicity and reduced the amount of TCE present in the leaves. During a mid-term experiment, plants were grown in potting soil and exposed to TCE for 3 weeks. Here, inoculation with P. putida W619-TCE had a less pronounced positive effect on plant growth and TCE phytotoxicity, but resulted in strongly reduced amounts of TCE in leaves and roots of plants exposed to 400 mg l(-1) TCE, accompanied by a lowered evapotranspiration of TCE. Dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA), which are known intermediates of TCE degradation, were not detected.
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ABSTRACT: Over the past few decades there has been avid interest in developing in situ strategies for remediation of environmental contaminants. Major foci have been on persistent organic chemicals and metals. Phytoremediation, a strategy that uses plants to degrade, stabilize, and/or remove soil contaminants, has been extensively investigated. Rhizoremediation, a specific type of phytoremediation that involves both plants and their associated rhizosphere microbes, can occur naturally, or can be actuated by deliberately introducing specific microbes. These microbes can be contaminant degraders and/or can promote plant growth under stress conditions. Because initial phytoremediation research showed great promise as a cost-effective remedial strategy, considerable effort has been devoted to making the transition from the laboratory to commercialization. Despite our understanding of the mechanisms of remediation, and the success of studies in the laboratory and greenhouse, efforts to translate phytoremediation research to the field have proven challenging. Although there have been many encouraging results in the past decade, there have also been numerous inconclusive and unsuccessful attempts at phytoremediation in the field. There is a need to critically assess why remediation in the field is not satisfactory, before negative perceptions undermine the progress that has been made with this promising remedial strategy. Two general themes have emerged in the literature: (1) Plant stress factors not present in laboratory and greenhouse studies can result in significant challenges for field applications. (2) Current methods of assessing phytoremediation may not be adequate to show that contaminant concentrations are decreasing, although in many cases active remediation may be occurring. If phytoremediation is to become an effective and viable remedial strategy, there is a need to mitigate plant stress in contaminated soils. There is also a need to establish reliable monitoring methods and evaluation criteria for remediation in the field. This review will focus on the challenges and the potential of phytoremediation, particularly rhizoremediation, of organic contaminants from soils.Plant Science. 01/2009;
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ABSTRACT: For phytoremediation of organic contaminants, plants have to host an efficiently degrading microflora. To assess the role of endophytes in alkane degradation, Italian ryegrass was grown in sterile soil with 0, 1 or 2% diesel and inoculated either with an alkane degrading bacterial strain originally derived from the rhizosphere of Italian ryegrass or with an endophyte. We studied plant colonization of these strains as well as the abundance and expression of alkane monooxygenase (alkB) genes in the rhizosphere, shoot and root interior. Results showed that the endophyte strain better colonized the plant, particularly the plant interior, and also showed higher expression of alkB genes suggesting a more efficient degradation of the pollutant. Furthermore, plants inoculated with the endophyte were better able to grow in the presence of diesel. The rhizosphere strain colonized primarily the rhizosphere and showed low alkB gene expression in the plant interior.Environmental Pollution 09/2009; 157(12):3347-50. · 3.73 Impact Factor
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ABSTRACT: A promising field to exploit plant-endophyte partnerships is the remediation of contaminated soils and (ground) water. Many plant growth promoting endophytes can assist their host plant to overcome contaminant-induced stress responses, thus providing improved plant growth. During phytoremediation of organic contaminants, plants can further benefit from endophytes possessing appropriate degradation pathways and metabolic capabilities, leading to more efficient contaminant degradation and reduction of both phytotoxicity and evapotranspiration of volatile contaminants. For phytoremediation of toxic metals, endophytes possessing a metal-resistance/sequestration system can lower metal phytotoxicity and affect metal translocation to the above-ground plant parts. Furthermore, endophytes that can degrade organic contaminants and deal with or, even better, improve extraction of the metals offer promising ways to improve phytoremediation of mixed pollution.Current opinion in biotechnology 04/2009; 20(2):248-54. · 7.82 Impact Factor