Impact and recovery of groundwater microbial communities exposed to manufactured nanomaterials (MNM).

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The overall objective of this study is to determine the impact of manufactured nano-material (MNM) exposure on the diversity and activities of natural microbial communities in groundwaters, including those responsible for the biodegrdation of organic co-contaminants. In order to address many of the key limitations of previous published exposure studies, we will take a more comprehensive (than previously reported studies), cross-disciplinary (environmental microbiologists and material scientists) and systematic approach to assessing MNM toxicity towards exposed groundater microbial communities. Firstly, batches of selected MNM will be synthesised and characterised, to confirm the nature (physical, chemical state and purity) of the starting material. This achieved by employing a range of standard methods, routinely used by the material scientists on site (Oxford Material Characterisation Service http://www-omcs.materials.ox.ac.uk), including including XPS,UOS, FTIR and TEM. The materials will then be introduced to laboratory microcosms, composed of freshly collected groundwater, historically contaminated with pesticide (isoproturon) and a common environmental/industrial contaminant (trichoroethene), and the response of the indigenous microbial community determined over a four-month exposure period. Changes in the relative abundance of microbial populations will provide insight into the impact of the communities to MNM exposure. Furthermore, changes in the communities' ability to biotransform groundwater contaminants will provide insights into the physiological state of the cells (activity), and shifts in the functional diversity of the community in response to MNM. Temporal samples will be taken and analysed using molecular microbial ecology and material science techniques, to determine the response of exposed microbial communities and chemical changes in the introduced MNM. This will include genetic fingerprinting of the whole microbial community to detect shifts in species composition and community structure; metabolic profiling, to determine changes in the ability of the community to undertake specific biochemical tasks; and monitoring attenuation rates of the pollutant. MNM assessment will include surface and interface analysis. In some studies MNM will be removed (in the case of Fe using magnets) and the recovery of the community caused by the removal of toxic stress examined. In addition, we will store the DNA to target key functional populations (in future studies) such as ammonium oxidisers, which play a vital role in nitrogen cycling, water quality and ecosystem functioning and are sensitive indicators of ecosystem health. This is a very specialist process and will require further funding via parallel and future grant applications. The programme of research outlined will be facilitated by input by staff on related projects, a current EU-funded studentship and in-kind support from OCMS. The information obtained will fill knowledge gaps in the evidence base for risk characterisation of MNM, a key requisite for the ENI programme. The project will significantly contribute to our understanding of how MNM chemistry influences microbial communities, and how MNM themselves will alter by their interaction with the environment and microbes themselves.