An investigation into the effects of nanoparticles on the bacterial diversity of freshwater and coastal marine sediments

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Nanoparticles (NPs) are very small particles in the size range of 1-100 nanometers. There is a rapidly expanding list of nano-products which have anti-bacterial properties, and these are used in medicine (sterile dressings, implants) and in domestic products (washing machines, easy-clean surfaces, clothing). Nano silver and titanium dioxide (TiO2) NPs are especially prevalent in these products, and biomedical studies have shown these materials to be antibacterial (with several modes of bacterial killing including oxidative stress). There are concerns that these materials will be released into the environment, especially from domestic use, and that these anti-bacterial properties will persist. We have already shown that TiO2 NPs are toxic to fish, and in this one-year project we are concerned about the microbial communities in marine and freshwater sediments. Bacterial communities play important roles in aquatic food webs, and are vital to the integrity and normal nutrient cycling, stability, and functional geochemistry of sediments. In this proposal we test the hypothesis that engineered NPs with known anti-bacterial properties could alter bacterial communities in aquatic sediments and the overlying water. Our approach is to use field-collected natural sediments and water from coastal marine and freshwater sites, and expose these to either nano silver or TiO2 NP in the laboratory. Bacterial diversity will be assessed using state-of-the-art molecular techniques involving DNA extractions from the sediments and overlying water. Particle characterisation will involve several recommended measurements, and chemical factors such as water pH or salinity will be monitored. The project brings together expertise on bacteria, sediment/metal chemistry, and the ecotoxicology of nanoparticles. The deliverables will include measured time courses of microbial diversity during controlled sediment and water exposures to silver and TiO2 NPs in separate experiments. This will provide the first vital 'proof of principle' as to whether or not NPs with anti-bacterial properties could also be harmful to microorganisms in the environment.