The environmental, microbiological and technological aspects of selenium is explored with the aim of assessing and identifying microorganisms capable of interacting with Se in the environment and forming functional 'bionanomaterials'. To determine the natural microbial response to high selenium concentrations, and to understand the role soil microorganisms play in transforming Se, a field site in Co. Meath, Ireland, was identified and sampled to determine the Se contents. Detailed examination of the soil profile showed toxic levels of Se up to 156ppm. The highest Se concentrations correlated with elevated concentrations of higher plant matter, inferring a phytoconcentration mechanism for Se within a post glacial fen, and Se was identified as a reduced organic species. Microcosm experiments were established to test whether the soil microbial community displayed increased resistance to Se. These revealed the Se present in the soil was recalcitrant to microbial degradation and Se(VI) enriched experiments were noted to cause drastic alterations in community structure, indicating elevated Se resistance was not widespread throughout the community. Despite this, amended Se(VI) was rapidly reduced to Se(0), as determined by XAS. Selenium, and the group 16 element tellurium, also display physico-chemical properties that make them ideal for a range of industrial, chemical and technological applications, including sequestration of hazardous wastes and as metal chalcogenide semiconducting 'quantum dots'. Se(0) and Te(0) bionanomaterials formed by 'resting cell' cultures of the model environmental isolate Geobacter sulfurreducens, despite low MIC values, were characterised and subsequently applied to the sequestration of Hg(0)v derived from Hg historically used to preserve herbarium specimens. This showed that the Hg can be sequestered by the Se(0) bionanoparticles in the form of HgSe and demonstrated increased stability over abiotic counterparts. Finally, the bacteria G. sulfurreducens, Shewanella oneidensis and Veillonella atypica were compared for Se(IV) reducing capabilities, and V. atypica was shown to be adept at the production of significant quantities of Se(II-) utilising the electron shuttle AQDS. Biogenic Se(II-) compared favourably with abiotic Se(II-) solutions in the formation of metal selenide quantum dots, displaying increased particle growth control as shown via a novel, time resolved XAS technique. Bacterial polymeric substances are inferred in controlling Se(II-) precursor stability. This research shows that bacteria represent an alternative, facile, 'green' synthetic method for the production of next-generation technological nanomaterials.

Protein nanofibres, commonly known as amyloid fibrils, are emerging as potential biological nanomaterials in a number of applications. Protein nanofibres are a highly ordered insoluble form of protein, which results when a normally soluble protein aggregates via a self-association process. However, researchers are currently faced with several challenges such as finding a cheap source of proteins that can be obtained without expensive purification and optimizing a scalable method of the manufacturing of protein nanofibres. This thesis has identified crude mixtures of fish lens crystallins as a cheap protein source and has optimized methods for large scale production of protein nanofibres of varying morphologies. Results show that by varying the conditions of fibre formation, individual protein fibres can be used as building blocks to form higher order structures. This ability to control the morphology and form higher ordered structures is a crucial step in bottom up assembly of bionanomaterials and opens possibilities for applications of protein nanofibres. The method of formation of protein nanofibres was optimized on a bench scale (1.5 mL Eppendorf tubes) and successfully scaled-up to 1 L volume. For larger scale-up volume (i.e. greater than 10 ml), internal surface area was important for the formation of protein nanofibres. The crude crystallin mixture prepared at 10 mg/mL was heated at 80oC in the presence of 10% v/v TFE at pH 3.8 for 24 hours and stored for an additional of 24 hours at room temperature for storage process. Aggregation and precipitation of proteins were observed as the protein solution was added to the pre-heated TFE. The resulting protein nanofibres were characterised using ThT dye binding, TEM and SEM. The TEM images show a network of long and criss-crossing protein nanofibres with individual fibres of approximately 10 to 20 nm in diameter and 0.5 to 1 μm long. These protein nanofibres were prepared in 1 mL centrifuge tubes and were left on the laboratory bench at room temperature. After 5 months, fresh TEM grids of the sample were prepared and visualized using TEM. Interestingly, TEM images show that a number of individual fibres had self-assembled in an intertwining fashion to form large bundles and higher order structures containing bundles of nanofibres up to 200 nm thick.