International audience

International audience | Antibiotics and antibiotic resistance genes have shown to be omnipresent in the environment. In this study, we investigated the effect of vancomycin (VA) on denitrifying bacteria in river sediments of a Waste Water Treatment Plant, receiving both domestic and hospital waste. We exposed these sediments continuously in flow-through reactors to different VA concentrations under denitrifying conditions (nitrate addition and anoxia) in order to determine potential nitrate reduction rates and changes in sedimentary microbial community structures. The presence of VA had no effect on sedimentary nitrate reduction rates at environmental concentrations, whereas a change in bacterial (16S rDNA) and denitrifying (nosZ) community structures was observed (determined by polymerase chain reaction-denaturing gradient gel electrophoresis). The bacterial and denitrifying community structure within the sediment changed upon VA exposure indicating a selection of a non-susceptible VA population.

International audience | The neurological damages resulted by endosulfan poisoning is not completely elucidated, especially in cellular organelles such as mitochondria. In the present study, the pro-oxidant effect of endosulfan on brain mitochondria was first investigated. Gavages of endosulfan into rats at the dose of 2 mg/kg induced oxidative stress in this organelle since it provokes a significant reduction of catalase (CAT), superoxide dismutase (SOD), and glutathione (GSH) level. In addition, a significant increase in mitochondria swelling and malondialdehyde (MDA) levels were observed in neuronal mitochondria, indicating clearly an intense peroxidation within mitochondria. Second, the protective effect of quercetin (QE) (10 mg/kg) against endosulfan-induced oxidative stress in mitochondria was also assessed. Indeed, the pretreatment of rats with QE protects brain mitochondria from oxidative stress, lipid peroxidation, and mitochondria swelling induced by endosulfan. The activities of antioxidant enzymes and the mitochondrial content of GSH and MDA were returned to control values. Thus, although endosulfan can have neurotoxic effects in brain rats, this toxicity can be prevented by quercetin.

International audience | The neurological damages resulted by endosulfan poisoning is not completely elucidated, especially in cellular organelles such as mitochondria. In the present study, the pro-oxidant effect of endosulfan on brain mitochondria was first investigated. Gavages of endosulfan into rats at the dose of 2 mg/kg induced oxidative stress in this organelle since it provokes a significant reduction of catalase (CAT), superoxide dismutase (SOD), and glutathione (GSH) level. In addition, a significant increase in mitochondria swelling and malondialdehyde (MDA) levels were observed in neuronal mitochondria, indicating clearly an intense peroxidation within mitochondria. Second, the protective effect of quercetin (QE) (10 mg/kg) against endosulfan-induced oxidative stress in mitochondria was also assessed. Indeed, the pretreatment of rats with QE protects brain mitochondria from oxidative stress, lipid peroxidation, and mitochondria swelling induced by endosulfan. The activities of antioxidant enzymes and the mitochondrial content of GSH and MDA were returned to control values. Thus, although endosulfan can have neurotoxic effects in brain rats, this toxicity can be prevented by quercetin.

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Organic pollutants (OPs) are potentially present in composts, and the assessment of their content and bioaccessibility in these composts is of paramount importance to minimize the risk of soil contamination and improve soil fertility. In this work, integration of the dynamics of organic carbon (OC) and OPs in an overall experimental framework is first proposed and adopted to validate the applicability of the COP-Compost model and to calibrate the model parameters on the basis of what has been achieved with the COP-Compost model. The COP-Compost model was evaluated via composting experiments containing 16 US Environmental Protection Agency (USEPA) polycyclic aromatic hydrocarbons (PAHs) and the sorption coefficient (Kd) values of two types of OP: fluorenthene (FLT) and pyrene (PHE). In our study, these compounds are used to characterize the sequential extraction and are quantified as soluble, sorbed, and non-extractable fractions. The model was calibrated, and coupling the OC and OP modules improved the simulation of the OP behavior and bioaccessibility during composting. The results show good agreement between the simulated and experimental results describing the evolution of different organic pollutants using the OP module, as well as the coupling module. However, no clear relationship is found between the Kd and the property of organic fractions. Further estimation of parameters is still necessary to modify the insufficiency of this present research.

Organic pollutants (OPs) are potentially present in composts, and the assessment of their content and bioaccessibility in these composts is of paramount importance to minimize the risk of soil contamination and improve soil fertility. In this work, integration of the dynamics of organic carbon (OC) and OPs in an overall experimental framework is first proposed and adopted to validate the applicability of the COP-Compost model and to calibrate the model parameters on the basis of what has been achieved with the COP-Compost model. The COP-Compost model was evaluated via composting experiments containing 16 US Environmental Protection Agency (USEPA) polycyclic aromatic hydrocarbons (PAHs) and the sorption coefficient (Kd) values of two types of OP: fluorenthene (FLT) and pyrene (PHE). In our study, these compounds are used to characterize the sequential extraction and are quantified as soluble, sorbed, and non-extractable fractions. The model was calibrated, and coupling the OC and OP modules improved the simulation of the OP behavior and bioaccessibility during composting. The results show good agreement between the simulated and experimental results describing the evolution of different organic pollutants using the OP module, as well as the coupling module. However, no clear relationship is found between the Kd and the property of organic fractions. Further estimation of parameters is still necessary to modify the insufficiency of this present research.

International audience | Siderophores are chelators with a high selectivity for Fe(III) and a good affinity for divalent metals, including Cd(II) and Ni(II). Inoculation with siderophore-producing bacteria (SPB) has thus been proposed as an alternative to chelator supply in phytoremediation. Accurate assessments of the potential of this association require a dissection of the interaction of siderophores with metals at the soil–root interface. This study focuses on pyoverdine (Pvd), the main siderophore produced by Pseudomonas aeruginosa. We first assessed the ability of Pvd to coordinate Ni(II). The stability constant of Pvd–Ni(II) (log K L′Ni = 10.9) was found to be higher than that of Pvd–Cd(II) (log K L′Cd = 8.2). We then investigated the effect of a direct supply of Pvd on the mobilization, speciation, and phytoavailability of Cd and Ni in hydroponics. When supplied at a concentration of 50 μM, Pvd selectively promoted Ni mobilization from smectite. It decreased plant Ni and Cd contents and the free ionic fractions of these two metals, consistent with the free ion activity model. Pvd had a more pronounced effect for Ni than for Cd, as predicted from its coordination properties. Inoculation with P. aeruginosa had a similar effect on Ni phytoavailability to the direct supply of Pvd.