Nanoscale Imaging of Microbial-Mineral Interactions (NIMMI)

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Microbial processes mediate the redox state of many metals and radionuclides, which in turn controls their mobility in the environment and the stability of a wide range of mineral phases. Organics are also influenced by these processes, acting either as electron donors for metal/mineral reduction, or as competing electron acceptors, for example in the case of chlorinated solvents. Advances in molecular ecology, genomics and post-genomic technologies have given us significant insight into the diversity of the organisms responsible for these important processes, and the underpinning physiology, often at a genetic level. In parallel, developments in nano-scale imaging and spectroscopy now offer the potential to reveal how these biological processes impact on the geosphere at an atomic-scale. The aim of this project is to gain a deeper understanding of key microbial-mineral interactions at the nano-scale using a combination of new state of the art synchrotron imaging techniques, including STXM, alongside microbiological, microscopy, geochemical and modelling approaches. Three complementary and interlinked systems of major environmental importance are the foci of this investigation. First, we will address the microbial reduction of insoluble Fe(III) oxyhydroxides, which plays a major role in many coupled biogeochemical processes in subsurface environments, to identify the nano-scale processes controlling this ubiquitous form of anaerobic respiration. Next, we will focus on the reductive mobilisation of As(V) sorbed onto Fe(III) oxyhydroxides, to identify the mechanism of this bioprocess thought to be catalysed by Fe(III)-reducing bacteria, and threatening the lives of tens of millions worldwide. Finally, the bioreduction of U(VI) in Fe(III)-reducing systems, which potentially limits uranium solubility, will also be studied as it has considerable relevance to the management of our existing soil contamination and our legacy nuclear waste, but is poorly understood at a mechanistic level.Through this programme, the applicants aim to obtain definitive evidence to help us understand the precise mechanisms of these important processes, which have been studied for more than a decade by many groups world-wide, but remain elusive. Impact will be across a broad scientific community, underpinning more robust conceptual and numerical models in very high profile areas including contaminant bioremediation, trace metal/metalloid biogeochemistry and the safe long-term stewardship of our legacy nuclear waste. Stakeholder engagement will be through strong links that already exist between Manchester and key centres involved in land and water quality and nuclear waste disposal, in the UK and worldwide. We will also enable the transfer of soft x-ray and STXM expertise from synchrotron facilities in North America and Europe to the UK Diamond synchrotron (beamline under construction), while training of key personal in the UK to make maximal use of these exciting and powerful new world-class facilities.