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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.

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Authors: J Hidalgo, M Anza, L Epelde, JM Becerril, C Garbisu
Title: Zero-valent iron nanoparticles and organic amendment assisted rhizoremediation of mixed contaminated soil using Brassica napus
Journal: Environmental Technology & Innovation
Date: 2022

Authors: C Monterroso, M Balseiro-Romero, C Garbisu, PS Kidd, NP Qafoku, PC Baveye
Title: Searching for solutions to soil pollution: underlying soil-contaminant interactions and development of innovative land remediation and reclamation techniques
Journal: Frontiers in Environmental Science
Date: 2022

Authors: L Epelde, M Mendizabal, L Gutiérrez, A Artetxe, C Garbisu, E Feliu
Title: Quantification of the environmental effectiveness of nature-based solutions for increasing the resilience of cities under climate change
Journal: Urban Forestry & Urban Greening
Vol: 67, 127433 Date: 2022

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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.

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.