The Poplar Endophyte Pseudomonas putida W619 as a Key to a Successful Phytoremediation of Volatile Organic Contaminants
Frans J. de Bruijn
Daniel van der Lelie2,
Hasselt University, Agoralaan, Building D, 3590 Diepenbeek, Belgium.
Poplar cuttings were exposed to trichloroethylene (TCE) in three different experimental setups, more specifically a short-term (days) hydroponics experiment, a midlong-term (weeks) pot experiment, and finally in a long-term (months) field trial. In order to improve the phytoremediation efficiency, poplar cuttings were inoculated with the TCE-degrading root endophyte Pseudomonas putida W619. In the short-term hydroponics experiment, P. putida W619 colonized all plant parts except the leaves which resulted in a very significant plant growth-promoting effect and a slightly diminished (23%) TCE evapotranspiration. In case the cuttings were grown in pots filled with potting soil, a growth-promoting trend and a 41% decreased TCE evapotranspiration were observed after the roots and the stem were colonized by P. putida W619. In the field experiment, 3 months after inoculation, the inoculated root endophyte P. putida W619 could only be reisolated from the roots. However, also some natural abundant stem endophytes became equipped with the TCE metabolic activity by horizontal gene transfer. Although the inoculation did not significantly affect plant growth, a 90% reduced TCE evapotranspiration was achieved after inoculation. These results demonstrated that the endophyte P. putida W619 could be the key to both, increasing biomass production on marginal, nutrient-poor land and also to an optimized phytoremediation of volatile organic contaminants.
Keywoards: Pseudomonas putida; poplar; phytoremediation; field experiments.