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 undergone 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.