Negative Effects of Copper Oxide Nanoparticles on Carbon and Nitrogen Cycle Microbial Activities in Contrasting Agricultural Soils and in Presence of Plants

Metal-oxide nanoparticles (NPs) such as copper oxide (CuO) NPs offer promising perspectives for the development of novel agro-chemical formulations of pesticides and fertilizers. However, their potential impact on agro-ecosystem functioning still remains to be investigated. Here, we assessed the impact of CuO-NPs (0.1, 1, and 100 mg/kg dry soil) on soil microbial activities involved in the carbon and nitrogen cycles in five contrasting agricultural soils in a microcosm experiment over 90 days. Additionally, in a pot experiment, we evaluated the influence of plant presence on the toxicity of CuO-NPs on soil microbial activities. CuO-NPs caused significant reductions of the three microbial activities measured (denitrification, nitrification, and soil respiration) at 100 mg/kg dry soil, but the low concentrations (0.1 and 1 mg/kg) had limited effects. We observed that denitrification was the most sensitive microbial activity to CuO-NPs in most soil types, while soil respiration and nitrification were mainly impacted in coarse soils with low organic matter content. Additionally, large decreases in heterotrophic microbial activities were observed in soils planted with wheat, even at 1 mg/kg for soil substrate-induced respiration, indicating that plant presence did not mitigate or compensate CuO-NP toxicity for microorganisms. These two experiments show that CuO-NPs can have detrimental effects on microbial activities in soils with contrasting physicochemical properties and previously exposed to various agricultural practices. Moreover, we observed that the negative effects of CuO-NPs increased over time, indicating that short-term studies (hours, days) may underestimate the risks posed by these contaminants in soils

Impact of soil fertilization with organic amendments on the dissemination of antibiotic resistance in cultivated soils

National audienc

Monitoring the impact of multi-stress contamination on an environmental opportunistic pathogen, <em>Stenotrophomonas maltophilia</em>: application to antibiotics and metals

National audienceStenotrophomonas maltophilia is a ubiquitous bacterial species known to be a soil and rhi- zospheric inhabitant as well as a human opportunistic pathogen. Multi-drug resistant strains are frequently found in hospitals because of its ability to acquire resistance genes through horizontal gene transfer and its possession of efflux pumps. Recent data also showed the link between antibiotic resistance and metal resistance among both clinical and environmen- tal strains. In this study, we evaluated over a 3 months study the impact of a cocktail of antibiotics (ciprofloxacin and sulfamethoxazole) and metals (Cu and Zn) on indigenous S. maltophilia in soil using an experimental design of soil columns exposed to manure contain- ing various concentrations of the cocktail. In parallel, the toxicant adsorption, distribution, and migration in the soil matrix were measured to interpret the observed biological response. Data showed that regardless of the concentration of the cocktail i.e. from low (1X PEC) to high (40X PEC) doses, no changes in population abundance were observed after 7 and 100 days of exposure. Genetic diversity (REP-profile) analysis among more than 650 isolates showed that metals were the dominant stressors. Antibiotic resistance gene abundance (sulfonamide and quinolone) was unaltered and no resistance gene transfer was observed. Finally, no changes were observed on the phenotypic (antibiotic resistance) properties at low or high antibiotic doses. These data suggest the lack of a dose/response effect as well as the lack of synergic effects between metals and antibiotics on the genotypic and phenotypic evolution of S. maltophilia populations

Role of micro-organisms in the leaching of critical metals from tungsten mine wastes: from the microscale to the field scale

International audienceThe availability of primary resources will continue to be a growing need to satisfy the increasing global demand for raw materials, with the consequence of the production of waste products from exploration and mining activities. An innovative approach is to consider tailings/wastes from mining in a circular economy concept, as secondary raw materials. The REVIVING project has been developed in this context, with coupled fundamental and applied approaches, with the objective of obtaining optimized experimental models for efficient recycling of critical metals from mining wastes, based on the manipulation of the indigenous tailing’s microbiome.We tested different leaching processes of metals of interest (Cu, Mn, Mg, Zn, W and Mo) from the mining waste of Panasqueira (Portugal). A first series of batch experiments was carried out with four bacteria isolated from this waste at increasing cell concentrations (107, 108 and 109 cells/ml) and under variable physiological conditions (live, dead, with nutrients...). Another batch reactor is also currently applied to evaluate the acidophilic leaching process via ferrooxidizing and sulfo-oxidizing micro-organisms enriched from the Panasqueira mine waste. Results from column reactors showed a limitation of the mobility of bacterial cells in the reactor due to the very small waste grain size leading to a strong filtration of the cells. The optimization of the cell transfer process is underway with a system dynamics approach in columns with different filling materials (waste, residues...) and experimental conditions (flow, saturation, geochemistry, microbiology...).The continuous monitoring of physico-chemical parameters (pH, O2, salinity and concentrations of metals and major ions...) and biological parameters (cell density by cytometry, qPCR and diversity by DNA-metabarcoding) will allow the identification of the dominant processes for a better understanding of the bioleaching phenomenon and therefore to design an efficient system for recycling metals from mining waste on a large scale

Monitoring the impact of multi-stress contamination on an environmental opportunistic pathogen, Stenotrophomonas maltophilia: application to antibiotics and metals

Stenotrophomonas maltophilia is a ubiquitous bacterial species known to be a soil and rhi- zospheric inhabitant as well as a human opportunistic pathogen. Multi-drug resistant strains are frequently found in hospitals because of its ability to acquire resistance genes through horizontal gene transfer and its possession of efflux pumps. Recent data also showed the link between antibiotic resistance and metal resistance among both clinical and environmen- tal strains. In this study, we evaluated over a 3 months study the impact of a cocktail of antibiotics (ciprofloxacin and sulfamethoxazole) and metals (Cu and Zn) on indigenous S. maltophilia in soil using an experimental design of soil columns exposed to manure contain- ing various concentrations of the cocktail. In parallel, the toxicant adsorption, distribution, and migration in the soil matrix were measured to interpret the observed biological response. Data showed that regardless of the concentration of the cocktail i.e. from low (1X PEC) to high (40X PEC) doses, no changes in population abundance were observed after 7 and 100 days of exposure. Genetic diversity (REP-profile) analysis among more than 650 isolates showed that metals were the dominant stressors. Antibiotic resistance gene abundance (sulfonamide and quinolone) was unaltered and no resistance gene transfer was observed. Finally, no changes were observed on the phenotypic (antibiotic resistance) properties at low or high antibiotic doses. These data suggest the lack of a dose/response effect as well as the lack of synergic effects between metals and antibiotics on the genotypic and phenotypic evolution of S. maltophilia populations

Role of micro-organisms in the leaching of critical metals from tungsten mine wastes: from the microscale to the field scale

International audienceThe availability of primary resources will continue to be a growing need to satisfy the increasing global demand for raw materials, with the consequence of the production of waste products from exploration and mining activities. An innovative approach is to consider tailings/wastes from mining in a circular economy concept, as secondary raw materials. The REVIVING project has been developed in this context, with coupled fundamental and applied approaches, with the objective of obtaining optimized experimental models for efficient recycling of critical metals from mining wastes, based on the manipulation of the indigenous tailing’s microbiome.We tested different leaching processes of metals of interest (Cu, Mn, Mg, Zn, W and Mo) from the mining waste of Panasqueira (Portugal). A first series of batch experiments was carried out with four bacteria isolated from this waste at increasing cell concentrations (107, 108 and 109 cells/ml) and under variable physiological conditions (live, dead, with nutrients...). Another batch reactor is also currently applied to evaluate the acidophilic leaching process via ferrooxidizing and sulfo-oxidizing micro-organisms enriched from the Panasqueira mine waste. Results from column reactors showed a limitation of the mobility of bacterial cells in the reactor due to the very small waste grain size leading to a strong filtration of the cells. The optimization of the cell transfer process is underway with a system dynamics approach in columns with different filling materials (waste, residues...) and experimental conditions (flow, saturation, geochemistry, microbiology...).The continuous monitoring of physico-chemical parameters (pH, O2, salinity and concentrations of metals and major ions...) and biological parameters (cell density by cytometry, qPCR and diversity by DNA-metabarcoding) will allow the identification of the dominant processes for a better understanding of the bioleaching phenomenon and therefore to design an efficient system for recycling metals from mining waste on a large scale