Bioaugmentation with engineered endophytic bacteria improves contaminant fate in phytoremediation

Area of Science:

• Environmental Microbiology
• Bioremediation
• Plant Science

Background:

• Phytoremediation of volatile organic contaminants is limited by incomplete plant and microbial degradation.
• Plant evapotranspiration can re-release contaminants into the air, reducing remediation effectiveness.
• Endophytic bacteria show potential for enhancing in-plant degradation of contaminants.

Purpose of the Study:

• To assess the efficacy of in situ inoculation of poplar trees with an engineered endophytic bacterium for trichloroethylene (TCE) remediation.
• To evaluate the reduction in TCE evapotranspiration following bacterial bioaugmentation.
• To investigate the establishment and gene transfer of the engineered strain within the plant's endophytic community.

Main Methods:

• In situ inoculation of field-grown poplar trees with TCE-degrading Pseudomonas putida W619-TCE.
• Monitoring of TCE evapotranspiration rates before and after inoculation.
• Analysis of the establishment of P. putida W619-TCE and horizontal gene transfer within the native endophytic population.

Main Results:

• In situ bioaugmentation with P. putida W619-TCE reduced TCE evapotranspiration by 90% under field conditions.
• The engineered strain successfully established and enriched as a poplar root endophyte.
• Evidence of horizontal gene transfer of TCE metabolic activity to the endogenous endophytic population was observed.

Conclusions:

• In situ bioaugmentation with engineered endophytic bacteria is a promising strategy to enhance phytoremediation of TCE.
• Successful establishment and horizontal gene transfer of the engineered strain contribute to reduced contaminant release.
• The use of horizontally gene-transferred engineered strains circumvents GMO regulations in Europe, facilitating practical application.