Rhizoremediation: a nature-based solution for soil restoration
- Nymphe
- Apr 30
- 3 min read
Soil pollution is one of the most persistent environmental challenges – especially in areas affected by long-term industrial activity. Traditional remediation methods are often costly, energy-intensive, and disruptive to ecosystems. What if, instead of fighting nature, we could work with it? One of the promising answers lies in rhizoremediation – a technology that harnesses the natural cooperation between plants and microorganisms. Developed within the NYMPHE project, this approach focuses on the dynamic interactions taking place in the rhizosphere.
Overview
Rhizoremediation is a technology based on the exploitation of plant-microbe interactions. As the name suggests, the approach focuses on the relationship established by the plant and beneficial microorganisms in the root system and its associated soil fraction (i.e., the rhizosphere).
The impact of this technology is related to its potential to be successfully implemented in large sites with historical contamination due to the occurrence of different classes of persistent organic pollutants. Indeed, for this type of sites, bioremediation approaches are more feasible and sustainable then physical and chemical remediation technologies from both from the ecological and the economical perspectives (e.g., restoration of soil quality, remediation management costs). Within the Nymphe project, rhizoremediation technology will be applied for the clean-up of historically polluted soils characterized by the presence of hydrocarbon concentrations above the safety threshold.
Technology description
Rhizoremediation is a process performed by two highly cooperating players, plants and microbes. Indeed, to survive in polluted soils, plants recruit microorganisms able to improve their fitness. This recruitment mechanism, based on root exudation of a specific array of compounds, is known as ‘cry-for-help’. The recruited beneficial microbes are involved in both the degradation of pollutants and plant growth promotion by nutrient provision and/or phytohormone production. On the other side, plants can favour the activity of the associated microbiome, including organic pollutant degradation pathways, by releasing from the roots a number of compounds exploited by microbes as signal molecules, transcriptional inducers or nutrient.
In this context, the rhizoremediation approach designed in Nymphe tackles hydrocarbon pollution in a historically contaminated site. The plant species selected for this purpose is sunflower, due to its ability to cope with the phytotoxicity level occurring in the target matrix. Sunflower has been exploited to enrich in the rhizosphere the most promising beneficial microorganisms naturally present in the contaminated soil. The microbial strains isolated from the rhizosphere represent indeed a valuable resource for the technology implementation. The proposed approach foresees the use of sunflower in the polluted site as biostimulant agent for the native microbial community endowed with hydrocarbon degrading capabilities. Plants will be in particular used in combination with the isolated hydrocarbon degrading microbes, aiming to boost soil remediation.
Ambitious
The ambitious of the Nymphe project is to rationally design rhizoremediation strategies by engineering the plant microbiome in highly hydrocarbon polluted soils. This could be achieved in different ways, all addressed within the Nymphe project.
The novel designed approaches comprise:
the selection of the best plant species in terms of recruitment of degrading population from the native soil microbiomes,
the administration to plants of additional biodegrading strains,
the use of compounds specifically released by plant roots under pollution stress.
All in all, these approaches are providing the advancement of scientific knowledge related to the power of ecological interactions in polluted soils. Setting up novel experimental protocols and combining multiple -omic approaches, Nymphe is disentangling the role of microbial populations and their interactions with the plant grown in the real polluted soil matrix, thus paving the way to site-tailored rhizoremediation interventions.
This technology has currently a TRL 4.
Results of technology development and implementation
The technology development led to the characterization of a large bacteria collection, that allowed the identification of different strains having hydrocarbon degrading ability. The most promising strains were selected and further tested creating microbial consortia to be administered to the sunflower plants cultivated in the polluted target soil. The supplementation of these consortia demonstrated they have a beneficial effect in promoting plant germination and growth in the phytotoxic soil.
Preliminary results indicated also that a higher hydrocarbon degradation occurred in the soil surrounding the roots of the inoculated plants compared to untreated control ones. Further experiment for the validation of the latter results will be performed at semi-field scale.
Furthermore, the conducted research identified different classes of chemical compounds released by sunflower roots under hydrocarbon induced stress. These metabolites may find future application as biostimulants of the native soil microbiome in polluted sites.
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