CC&E Spring 2017 Seminar Series – “Plants and their Associated Bacteria: Partners in Remediation of Contaminated Soils and Groundwater? General Considerations and Examples from the Field”

This Friday, March 3, 2017 the College of the Coast & Environment will be hosting Dr. Jaco Vangronsveld from Sofie Thijs and Nele Weyens Hasselt University, Centre for Environmental Sciences, Diepenbeek, Belgium. Dr. Vangronsveld’s topic for the seminar will be “Plants and their associated bacteria: partners in remediation of contaminated soils and groundwater? General considerations and examples from the field.” Please join us in the Dalton J. Woods Auditorium for this very informative talk.


Plants and their associated bacteria: partners in remediation of contaminated soils and groundwater? General considerations and examples from the field

Plants are colonised by microorganisms in cell densities that are far greater than the number of plant cells. Plants have an intense interaction with these microbes for numerous physiological functions. Microbial mediated functions that are important to enhance beneficial outcome include nutrient cycling, organic matter mineralisation, plant-growth promotion, disease resistance, and defence against abiotic stresses.

An essential supportive role played by plant-microbiota involves the degradation and detoxification of xenobiotic compounds. As soil microorganisms are the primary agents for the mineralisation of organic compounds and nutrient cycling, they may also convert contaminants to stable and/or less toxic products. This activity may be greater in the plant rhizosphere because plants provide microbial habitats and nutrients that are rapidly utilised by the microbes for growth. Microorganisms residing inside plant tissues (endophytes), or on aerial plant parts (phyllosphere) can help to stabilise and/or transform contaminants that have been translocated, which may reduce toxicity and the extent of volatilisation of pollutants to the environment.

Biodegradative microorganisms have to compete for resources with other inhabitants of the plant niche, and biodegradation can be independent of effects on plant growth. For each individual field case, many aspects of the plant-microbiome interactions should be thoroughly investigated and optimised to achieve the desired outcome.

Phytoremediation is a promising technology: driven by solar energy, plants are able to pump contaminations to their rhizosphere and even take them up. In the rhizosphere and during its transport throughout the plant, the present plant-associated micro-organisms can take care of the degradation of the organic contaminants.

Successful application of phytoremediation was demonstrated in several field cases (BTEX, diesel and TCE contamination). On these sites, poplar trees were planted in the contamination plume and groundwater concentrations and possible evapotranspiration to the atmosphere were monitored. Despite many successful field applications, phytoremediation is not yet routinely applied due to some constraints. At first, plants should tolerate the occurring contaminant levels. Further, the degradation capacity of the plant-associated microbes must be high enough to prevent phytotoxicity and evapotranspiration. To solve these constraints, a diversity of interesting characteristics of plant-associated bacteria can be exploited. To explore these characteristics, soil, rhizosphere, roots and shoots of hybrid poplars were sampled in order to isolate bacteria able to grow in the presence of and to biodegrade BTEX, diesel and TCE. All cultivable bacteria were tested for their capacity to produce various plant growth promoting traits. Strains with the highest degradation rates were selected for genome sequencing (Ion Torrent). The availability/uptake of many organics can be stimulated by bacteria producing e.g. surfactants, siderophores and organic acids. Bacteria equipped with the appropriate degradation pathway(s) can strongly improve the degradation efficiency.

On a TCE-contaminated site, poplar trees were in situ inoculated with TCE-degrading endophytes. Three months later, a 90%-reduced TCE evapotranspiration was observed. Further investigations revealed that this reduction was not only achieved by an enrichment of the inoculated strain, but also by of transfer of the degradation genes from the inoculated strain to strains from the natural abundant community.

Lunch will be provided immediately following the seminar in the conference room next to the auditorium.

Time: 11:30 a.m. – 12:15 p.m.
Where: Dalton J. Woods Auditorium
LSU Energy, Coast, and Environment Building