studied. Perhaps of greater interest are biomineralisation and bioreduction -the immobilisation of uranium by conversion of soluble U VI O2 2+ to insoluble U VI O2 2+ (e.g. U VI O2 2+phosphate) and U IV (e.g. U IV O2) minerals respectively. These processes have typically been studied by liquid scintillation or assay-based techniques, which are limited to giving purely quantitative data on the concentration of uranium in solution. Further work has been carried out on these systems using EXAFS, to provide data on the coordination geometry of uranium, and various electron microscopy techniques, which can probe uranium distribution on the cellular level. These techniques, however, are not widely available and require significant sample preparation. Many questions remain to be answered on the mechanisms of potential bioremediation techniques, such as the nature of cell-surface species involved, as well as the role of uranium speciation and the influence of coordinating and competing ions in solution. The range of techniques used to study these processes must be expanded to allow real-time, in vivo monitoring in systems that better emulate environmental and geological conditions.