Project R-3252

Endophyte-enhanced plant growth and phytoremediation: stability of the inoculated strain as the crucial step towards in situ application. (Research)

Pseudomonas putida W619-TCE is a growth promoting root endophyte of poplar containing the pTOM plasmid, coding for trichloroethylene (TCE) degradation. In situ inoculation of TCE-exposed poplar trees with this strain resulted in a 90% reduced TCE evapotranspiration, measured 3 months after inoculation. Before moving this concept towards long-term field applications, the stability of the inoculation needs to be investigated. As re-inoculation might be needed to obtain a long-term stability, at first, a re-inoculation strategy applicable in the field is optimized. Next, TCE-exposed and non-exposed poplar cuttings are inoculated and some re-inoculated after 6 months with P. putida W619-TCE. The effect of (re-)inoculation on the bacterial population is investigated every 3 months by comparing total bacterial communities using DGGE analysis. Observed differences are quantified using qRT-PCR and studied in depth by pyrosequencing. Next, the establishment/enrichment of the inoculated strain is confirmed using BOX-PCR DNA-fingerprinting. In the cultivable bacterial population, the horizontal gene transfer of the pTOM plasmid is investigated by identifying the members that received the plasmid and quantifying their expression of the genes coding for TCE degradation by qRT-PCR and their TCE degradation capacity by HPLC. The transfer of the pTOM plasmid to the non-cultivable community is quantified using qRT-PCR.

01 October 2011 - 30 September 2015