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Zero-valent iron nanoparticles and organic amendment assisted rhizoremediation of mixed contaminated soil using Brassica napus

Authors: June Hidalgo, Mikel Anza, Lur Epelde, José M. Becerril, Carlos Garbisu

Journal: Environmental Technology & Innovation

Soil is one of our most important natural resources. Regrettably, the expansion of human activities has resulted in the degradation of the soil resource due to contamination with a myriad of organic and inorganic compounds. The remediation of mixed contaminated soils, i.e. soils contaminated with both organic compounds and metals, is challenging as it requires actions to simultaneously decrease metal-induced risks and organic contaminant concentrations. Here, we evaluated the effect of the addition of zero-valent iron nanoparticles (nanoremediation) and organic amendments (biostimulation) on the rhizoremediation, using Brassica napus plants, of soil simultaneously contaminated with zinc (2,500 mg kg-1) and lindane (100 mg kg-1). We used a factorial design with three factors (amendment, nZVI, plant) to evaluate the impact of the applied remediation actions on lindane and extractable Zn concentrations, as well as on soil health recovery as manifested by the values of different soil microbial indicators. The studied microbial indicators were not negatively affected by nZVI application. The application of nZVI was the most effective factor regarding the targeted reduction in lindane concentration (51% average reduction in nZVI treated soils). The highest reduction in extractable Zn was achieved in the presence of B. napus, nZVI and organic amendments (99 and 95% reduction in horse manure-amended and sewage sludge-amended soils, respectively). The combination of the three factors led to the highest values of soil microbial indicators (although a significant triple interaction was not observed for all parameters), especially when combined with horse manure amendment: in this case, prokaryotic richness increased by 64%, respiration by 376%, eukaryotic abundance by 333%, and prokaryotic abundance by 437%, compared to untreated soils. The combination of remediation approaches (rhizoremediation with B. napus, nanoremediation with nZVI, biostimulation with organic amendments) can help overcome the limitations of each individual strategy.

Bioinocula and CROPping systems: an integrated biotechnological approach for improving crop yield, biodiversity and REsilience of Mediterranean agro-ecosystems (ReCrop; 2021-2024)

The Mediterranean economy is highly dependent on agriculture.
However, agricultural sustainability and productivity in this region are under serious threat due to climate change and depletion of water resources. This is worsened by poor management practices, such as the overuse of chemical fertilizers and pesticides, overgrazing, and monoculture farming. ReCROP aims to redesign Mediterranean agrosystems with improved resilience capacity and higher productivity, focusing on the development of sustainable agricultural production systems through the combined use of biotechnological tools and environmentally friendly agronomic practices. This will allow farming systems to face climate change trough the improvement of below and aboveground biodiversity, fertility, and water conservation. RECROP uses the novel approach of plant-microorganism management that relies on the increase of soils functions and health by using bioinocula, amendments, cropping systems, and climate-ready crops, to increase crop yields while providing ecological services, e.g., increasing carbon sequestration, organic matter, nutrient cycling and water conservation.

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Remediation of Organically Contaminated Soil Through the Combination of Assisted Phytoremediation and Bioaugmentation

Authors: Mikel Anza, Oihane Salazar, Lur Epelde, José María Becerril, Itziar Alkorta and Carlos Garbisu

Journal: Applied Sciences

Vol: 9, 4757; doi:10.3390/app9224757

Date: 2019

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Here, we aimed to bioremediate organically contaminated soil with Brassica napus and a bacterial consortium. The bioaugmentation consortium consisted of four endophyte strains that showed plant growth-promoting traits (three Pseudomonas and one Microbacterium) plus three strains with the capacity to degrade organic compounds (Burkholderia xenovorans LB400, Paenibacillus sp. and Lysinibacillus sp.). The organically contaminated soil was supplemented with rhamnolipid biosurfactant and sodium dodecyl benzenesulfonate to increase the degradability of the sorbed contaminants. Soils were treated with organic amendments (composted horse manure vs. dried cow slurry) to promote plant growth and stimulate soil microbial activity. Apart from quantification of the expected decrease in contaminant concentrations (total petroleum hydrocarbons, polycyclic aromatic hydrocarbons), the e ectiveness of our approach was assessed in terms of the recovery of soil health, as reflected by the values of di erent microbial indicators of soil health. Although the
applied treatments did not achieve a significant decrease in contaminant concentrations, a significant improvement of soil health was observed in our amended soils (especially in soils amended with dried cow slurry), pointing out a not-so-uncommon situation in which remediation e orts fail from the point of view of the reduction in contaminant concentrations while succeeding to recover soil health.

Avanzando en la aplicación de estrategias innovadoras de fitogestión en zonas contaminadas del espacio Sudoe (Phy2SUDOE; 2020-2023)

La fitogestión es una fitotecnología, surgida a partir de la fitorremediación, basada en el uso de plantas (árboles, arbustos, herbáceas) para controlar el riesgo asociado a la presencia de contaminantes en emplazamientos degradados, a la vez que: (i) se generan productos (e.g., madera, resina, aceites esenciales, bioenergía, ecocatalizadores) a partir de la biomasa cosechada; y (ii) se potencia el suministro de servicios ecosistémicos (e.g., secuestro de C, control de erosión, creación de hábitats).

Phy2SUDOE pretende valorizar emplazamientos contaminados con metales-metaloides y/o compuestos orgánicos en la región SUDOE mediante el empleo de estrategias de fitogestión encaminadas a la generación de productos y servicios ecosistémicos en dichos emplazamientos, a la vez que se minimiza el impacto ambiental que los contaminantes pudieran
ocasionar. Asimismo, este proyecto aspira a implantar estrategias de conservación de la biodiversidad endémica propia de algunos emplazamientos contaminados (e.g., flora metalícola, bacterias promotoras del crecimiento vegetal, etc.) por su valor intrínseco y utilitario (e.g., aplicaciones biotecnológicas).

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Type IV coupling proteins as potential targets to control the dissemination of antibiotic resistance

Authors: Álvarez-Rodríguez I, Arana L, Ugarte-Uribe B, Gómez-Rubio E, Martín-Santamaría S, Garbisu C, Alkorta I
Title: Type IV coupling proteins as potential targets to control the dissemination of antibiotic resistance
Journal:  Frontiers in Molecular Biosciences
Vol: 7, 201 Date: 2020

The increase of infections caused by multidrug-resistant bacteria, together with the loss of effectiveness of currently available antibiotics, represents one of the most serious threats to public health worldwide. The loss of human lives and the economic costs associated to the problem of the dissemination of antibiotic resistance require immediate action. Bacteria, known by their great genetic plasticity, are capable not only of mutating their genes to adapt to disturbances and environmental changes but also of acquiring new genes that allow them to survive in hostile environments, such as in the presence of antibiotics. One of the major mechanisms responsible for the horizontal acquisition of new genes (e.g., antibiotic resistance genes) is bacterial conjugation, a process mediated by mobile genetic elements such as conjugative plasmids and integrative conjugative elements. Conjugative plasmids harboring antibiotic resistance genes can be transferred from a donor to a recipient bacterium in a process that requires physical contact. After conjugation, the recipient bacterium not only harbors the antibiotic resistance genes but it can also transfer the acquired plasmid to other bacteria, thus contributing to the spread of antibiotic resistance. Conjugative plasmids have genes that encode all the proteins necessary for the conjugation to take place, such as the type IV coupling proteins (T4CPs) present in all conjugative plasmids. Type VI coupling proteins constitute a heterogeneous family of hexameric ATPases that use energy from the ATP hydrolysis for plasmid transfer. Taking into account their essential role in bacterial conjugation, T4CPs are attractive targets for the inhibition of bacterial conjugation and, concomitantly, the limitation of antibiotic resistance dissemination. This review aims to compile present knowledge on T4CPs as a starting point for delving into their molecular structure and functioning in future studies. Likewise, the scientific literature on bacterial conjugation inhibitors has been reviewed here, in an attempt to elucidate the possibility of designing T4CP-inhibitors as a potential solution to the dissemination of multidrug-resistant bacteria.