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Rôle des biofilms bactériens sur le devenir des nanoparticules manufacturées dans les sols

Over the last decades, the important increase in nanoparticles (NPs) production and use resulted in their release in the environment and raise important concerns regarding their potential to negatively impact ecosystems. In the environment, NPs are likely accumulated in soil where it is expected that they will interact with bacterial biofilm/mineral interfaces, one of the most reactive compartment. This complex interface exhibits highly specific physico-chemical properties that can control NPs fate and transformations (dissolution, aggregation…). During this PhD work, I was interested by the partitioning of NPs at this interface, the transformations that NPs can undergo and to physico-chemical parameters that control NPs behavior. To do so, Shewanella oneidensis MR-1 biofilms were grown on oriented single crystals -Al2O3 (1-102) and were exposed to silver nanoparticles and Quantum Dots. NPs partitioning and stability were mostly investigated using Long Period – X-ray Standing Waves – Fluorescence Yield spectroscopy and Grazing Incidence – X-ray Absorption Spectroscopy. This work allows to demonstrate that NPs partitioning at the interface is mostly controlled by the mineral surface. Nevertheless, biofilm is able to slow down NPs migration depending on NPs size and aggregation state, NPs surface charge and coating type ((in)organic, hydrophobic properties). When NPs migrate through biofilm thickness, they undergo transformation, and more specifically dissolution. This dissolution is partly controlled by microenvironments within biofilm thickness but also by the presence of thiol groups at EPS and cells surfaces as well as in molecules secreted by bacteria.Depuis 20 ans, les nanoparticules manufacturées (NPs) sont de plus en plus incorporées dans de nombreux produits de la vie courante (peinture, crème solaire). L’augmentation de leur production et de leur utilisation favorise la dissémination de ces objets nanométriques dans l’environnement et entraînent d’importantes inquiétudes quant à leur impact sur les écosystèmes. Les NPs sont notamment susceptibles de s’accumuler dans les sols où elles seront exposées à une interface hautement réactive. Cette dernière est constituée de biofilms bactériens à la surface des minéraux et est à même de contrôler leur devenir et leur transformation (dissolution, agrégation…). Durant cette thèse, je me suis intéressée à la distribution des NPs à l’interface, aux transformations qu’elles peuvent y subir et aux paramètres physico-chimiques qui contrôlent leur comportement. Pour répondre à ces problématiques, j’ai travaillé avec une interface, constitué d’un biofilm de Shewanella oneidensis MR-1 ayant poussé à la surface d’un cristal d’alumine (-Al2O3 (1-102)), exposée à des NPs d’argent et des Quantum Dots. La distribution et la stabilité des NPs à l’interface ont été étudiées principalement à l’aide des techniques des ondes stationnaires de rayons X et de la spectroscopie d’absorption en incidence rasante. Ce travail de thèse a permis de montrer que la distribution des NPs à l’interface est principalement contrôlée par la surface minérale, mais que le biofilm est capable de ralentir cette migration dépendamment de la taille des NPs, de leur état d’agrégation, de leur charge de surface et du type d’enrobage ((in)organique, hydrophobe). La migration des NPs dans l’épaisseur du biofilm favorise leurs transformations, et notamment la dissolution. Cette dissolution est en partie contrôlée par les microenvironnements présents dans l’épaisseur du biofilm et par la présence de groupements thiols à la surface des bactéries, et des EPS, ainsi que dans des molécules sécrétées par les bactéries pour se protéger

Impact of bacterial biofilm on nanoparticles fate in soil

Depuis 20 ans, les nanoparticules manufacturées (NPs) sont de plus en plus incorporées dans de nombreux produits de la vie courante (peinture, crème solaire). L’augmentation de leur production et de leur utilisation favorise la dissémination de ces objets nanométriques dans l’environnement et entraînent d’importantes inquiétudes quant à leur impact sur les écosystèmes. Les NPs sont notamment susceptibles de s’accumuler dans les sols où elles seront exposées à une interface hautement réactive. Cette dernière est constituée de biofilms bactériens à la surface des minéraux et est à même de contrôler leur devenir et leur transformation (dissolution, agrégation…). Durant cette thèse, je me suis intéressée à la distribution des NPs à l’interface, aux transformations qu’elles peuvent y subir et aux paramètres physico-chimiques qui contrôlent leur comportement. Pour répondre à ces problématiques, j’ai travaillé avec une interface, constitué d’un biofilm de Shewanella oneidensis MR-1 ayant poussé à la surface d’un cristal d’alumine (-Al2O3 (1-102)), exposée à des NPs d’argent et des Quantum Dots. La distribution et la stabilité des NPs à l’interface ont été étudiées principalement à l’aide des techniques des ondes stationnaires de rayons X et de la spectroscopie d’absorption en incidence rasante. Ce travail de thèse a permis de montrer que la distribution des NPs à l’interface est principalement contrôlée par la surface minérale, mais que le biofilm est capable de ralentir cette migration dépendamment de la taille des NPs, de leur état d’agrégation, de leur charge de surface et du type d’enrobage ((in)organique, hydrophobe). La migration des NPs dans l’épaisseur du biofilm favorise leurs transformations, et notamment la dissolution. Cette dissolution est en partie contrôlée par les microenvironnements présents dans l’épaisseur du biofilm et par la présence de groupements thiols à la surface des bactéries, et des EPS, ainsi que dans des molécules sécrétées par les bactéries pour se protéger.Over the last decades, the important increase in nanoparticles (NPs) production and use resulted in their release in the environment and raise important concerns regarding their potential to negatively impact ecosystems. In the environment, NPs are likely accumulated in soil where it is expected that they will interact with bacterial biofilm/mineral interfaces, one of the most reactive compartment. This complex interface exhibits highly specific physico-chemical properties that can control NPs fate and transformations (dissolution, aggregation…). During this PhD work, I was interested by the partitioning of NPs at this interface, the transformations that NPs can undergo and to physico-chemical parameters that control NPs behavior. To do so, Shewanella oneidensis MR-1 biofilms were grown on oriented single crystals -Al2O3 (1-102) and were exposed to silver nanoparticles and Quantum Dots. NPs partitioning and stability were mostly investigated using Long Period – X-ray Standing Waves – Fluorescence Yield spectroscopy and Grazing Incidence – X-ray Absorption Spectroscopy. This work allows to demonstrate that NPs partitioning at the interface is mostly controlled by the mineral surface. Nevertheless, biofilm is able to slow down NPs migration depending on NPs size and aggregation state, NPs surface charge and coating type ((in)organic, hydrophobic properties). When NPs migrate through biofilm thickness, they undergo transformation, and more specifically dissolution. This dissolution is partly controlled by microenvironments within biofilm thickness but also by the presence of thiol groups at EPS and cells surfaces as well as in molecules secreted by bacteria

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Chemical data for bioreactors.THIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV

How microbial biofilms impact the interactions of Quantum Dots with mineral surfaces?

International audienc

Dynamics of silver nanoparticles at the solution/biofilm/mineral interface

International audienceThe extensive use of silver nanoparticles (AgNPs) is likely to result in their significant environmental release, and thus raises important concerns regarding their impact to ecosystems. In soils, bacterial biofilms can be found as mineral coatings, forming a complex interface that exhibits highly specific physico-chemical properties. As a result, this environmental compartment is likely to partly control the AgNPs fate. However, the interaction modes undergone by nanoparticles at this solution/biofilm/mineral are not yet well constrained. The dynamics of AgNPs interactions at a Shewanella oneidensis MR-1 biofilm-corundum (α-Al2O3) interface were investigated by Long Period-X-Ray Standing Waves-Fluorescence Yield Spectroscopy. Three different nanoparticle coatings of various properties (PVP, SiO2 and SiO2-NH2) were tested, showing important differences in AgNPs partitioning and stability at this complex interface. The behavior of the two AgNPs coated by an organic layer, but of opposite charge (SiO2 and SiO2-NH2), indicates that at first-order, electrostatic interactions control the AgNPs partitioning at the solution/biofilm/mineral interface. In addition, the comparative study of the organic PVP-coated and the inorganic SiO2-coated AgNPs, both negatively charged, highlights the controls imposed by the nanoparticles size and hydrophobic properties on their interactions with this complex interface

How Microbial Biofilms Control the Environmental Fate of Engineered Nanoparticles?

International audiencePredicting the fate of engineered nanoparticles (ENPs) once they are released in the environment is essential to evaluate their impacts to ecosystems. Microbial biofilms, as highly reactive compartments in soils and sediments, have the potential to impose strong controls on ENPs life cycle in natural settings. However, information regarding impacts of biofilms toward ENPs environmental fate are not easily accessible, and such evidences are collected and discussed in this review, in order to identify common trends and to better constrain the role played by these microbial structures. Biofilms are reported to exhibit important ENPs accumulation capacities, and short to long-term ENPs immobilization can thus be expected. Mechanisms that govern such accumulation and ENPs migration within biofilms depend strongly on electrostatic and hydrophobic interactions, as well as biofilm structural properties, such as density and permeability. They are a combination of key parameters that include ENPs size and surface properties, mineral substrate reactivity, ability to develop organic corona around ENPs, or formation of aggregates within the biofilm thickness. In addition, these microbial structures exhibit highly reactive microenvironments, and are consequently able to impose major ENPs transformations such as dissolution, through ligand- or redox-mediated pathways, as well as passivation or stabilization processes. Interestingly, exposure to toxic ENPs can even trigger a response from micro-organisms biofilms which has the potential to strongly modify ENPs speciation. Promising approaches to investigate the role of microbial biofilms for ENPs cycling in realistic systems are introduced through the use of mesocosms, medium-size replicated ecosystems that allow to integrate the complexity of natural settings. Finally, biofilm-mediated nanoparticles synthesis in man-impacted systems is presented. This raises important questions regarding biofilms role as secondary sources of nanoparticles

Discovery and potential ramifications of reduced iron-bearing nanoparticles—magnetite, wüstite, and zero-valent iron—in wildland–urban interface fire ashes

The increase in fires at the wildland–urban interface has raised concerns about the potential environmental impact of ash remaining after burning. Here, we examined the concentrations and speciation of iron-bearing nanoparticles in wildland–urban interface ash. Total iron concentrations in ash varied between 4 and 66 mg g$^{−1}$. Synchrotron X-ray absorption near-edge structure (XANES) spectroscopy of bulk ash samples was used to quantify the relative abundance of major Fe phases, which were corroborated by transmission electron microscopy measurements. Maghemite ($γ$-(Fe$^{3+}$)$_2$O$_3$) and magnetite ($γ$-Fe$^{2+}$(Fe$^{3+}$)$_2$O$_4$) were detected in most ashes and accounted for 0–90 and 0–81% of the spectral weight, respectively. Ferrihydrite (amorphous Fe(III)–hydroxide, (Fe$^{3+}$)$_5$HO$_8$·4H$_2$O), goethite ($α$-Fe$^{3+}$OOH), and hematite ($α$-$^{3+}_2$O$_3$) were identified less frequently in ashes than maghemite and magnetite and accounted for 0–65, 0–54, and 0–50% of spectral weight, respectively. Other iron phases identified in ashes include wüstite (Fe$^{2+}$O), zerovalent iron, FeS, FeCl$_2$, FeCl$_3$, FeSO$_4$, Fe$_2$(SO$_4$)$_3$, and Fe(NO$_3$)$_3$. Our findings demonstrate the impact of fires at the wildland–urban interface on iron speciation; that is, fires can convert iron oxides (e.g., maghemite, hematite, and goethite) to reduced iron phases such as magnetite, wüstite, and zerovalent iron. Magnetite concentrations (e.g., up to 25 mg g$^{-1}$) decreased from black to gray to white ashes. Based on transmission electron microscopy (TEM) analyses, most of the magnetite nanoparticles were less than 500 nm in size, although larger particles were identified. Magnetite nanoparticles have been linked to neurodegenerative diseases as well as climate change. This study provides important information for understanding the potential environmental impacts of fires at the wildland–urban interface, which are currently poorly understood

New Insights into Lithium Hopping and Ordering in LiNiO2_2 Cathodes during Li (De)intercalation

In situ$_7$Li and ex situ$_6$Li nuclear magnetic resonance (NMR) spectroscopy is applied to monitor lithium mobility in a LiNiO$_2$ cathode during Li-ion (de)intercalation. In situ X-ray absorption spectroscopy and galvanostatic intermittent titration are also used to capture changes during the Li-ion deintercalation process. A considerable line broadening was first found by $^7$Li NMR spectroscopy. The Jahn–Teller distortion hinders the Li diffusion, thus broadening the NMR signal. The observed NMR shifts are compared to Li/vacancy ordering patterns described earlier by Arroyo y de Dompablo et al. Coupled motions of electrons and Li ions are also discovered by both in situ$_7$Li and ex situ$_6$Li NMR spectroscopy for the first time. They result in local Li environments with an enhanced number of Ni$^{3+}$ neighbors at highly charged states. This opens a new perspective for understanding the highly delithiated structure

Degradation of ZnGa2O4:Cr3+ luminescent nanoparticles in lysosomal-like medium

International audienc