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MICROBIAL IMPACTS OF ENGINEERED NANOPARTICLES
Impact/Purpose:
Responsible usage of nanomaterials in commercial products and environmental applications, and prudent management of the associated risks, require an understanding of nanoparticle mobility, bioavailability and ecotoxicology. This project will elucidate processes governing the transport and microbial impacts of two classes of catalytic nanomaterials in soil-water systems: fullerenes and metallic nanoparticles (e.g., TiO2, ZnO and Fe(0)). Specific tasks include to: (1) characterize nanomaterials size, shape, functionality, reactivity, aggregation, deposition potential, and bioavailability; (2) screen nanomaterials of varying sizes and properties for bactericidal activity; (3) discern bacterial physiologic characteristics that confer resistance (or susceptibility) to catalytic nanomaterials; (4) evaluate the potential for fullerene biotransformation by reference bacteria and fungi; and (5) assess the impact of simulated nanomaterial releases on microbial diversity and community structure.
Description:
Reactivity at the nanometric scale is intimately linked to nanoparticle mobility and microbial sensitivity. Thus, first-order factors increasing nanoparticle reactivity should increase the rate of redox reactions with second-order effects on particle mobility and ecotoxicity. Sources of reactivity may include functionalization of nanoparticle surfaces, affinity for electron uptake and subsequent transfer to species in solution and interfacial phenomena ranging from ordered water effects such as clathrate formation around nanoparticle nuclei to adsorption of naturally occurring macromolecules. Regarding microbial impacts, we hypothesize that nanomaterials that generate reactive oxygen species or related free radicals will hinder heterotrophic and phytosynthetic activities and cause population shifts that reflect differential responses and diverse protective mechanisms used by dissimilar populations. Thus, aerobic bacteria with enzymes that destroy toxic oxygen species or with thicker cell walls may have a competitive advantage. Similarly, fermenting bacteria may be more resistant than respiring or phytosynthetic bacteria because the latter employ many biomolecules to transfer electrons during phosphorylation, which could interact with catalytic nanomaterials to generate harmful free radicals.