 I'm Lyn McCaskey of the University of Birmingham. I'm Joe Renshaw from the University of Birmingham. Recent events at Fukushima have highlighted the need for effective, portable methods for radio-nuclide removal from contaminated waters. Actonites are problematic as they are long-lived, but a more immediate concern is vision products such as strontium and cesium. These are highly mobile in the environment and bioavailable. For example, strontium can be taken up into bone. Here at the University of Birmingham, we have been investigating the formation of biomunerals by bacteria as a method for removing radio-nuclides from contaminated groundwater and wastewater solutions. Our work has been focusing mainly on strontium and cesium because these are of more immediate impact in the aftermath of Fukushima. When we refer to biomineralisation as a way of removing radio-nuclides, it's possible to take these up into pre-formed metallic mineral deposits like metal phosphates, where they go into the biomineral by a process of iron exchange, which hoovers up the metals very appropriately from the waste. The problem is, of course, that when the material becomes full, it's saturated and it needs to be replenished. So, as an alternative approach, we've been looking at the concept of using biomineralisation as a way of removing radio-nuclides on a long-term basis. Of course, for this to be effective, the bacteria need to remain active for long periods in a radioactive situation. Hence, our first focus was on looking at the radio resistance of an enzymatic method for removing radio-nuclides. Now, this method, which is quite a good example, is the use of bacteria to liberate a phosphate from an organic phosphate donor molecule to make a biomineral precipitate of metal phosphate. Now, it's been known for some years that a species of Seratia can do this very effectively by making uranium phosphate out of uranium mine water, for example. Now, we wanted to look at the possibility of co-crystallising uranium, strontium and cesium by the activity of this bacterium. For this to be effective, it's not necessary for the bacteria to remain alive and viable, but it is essential for the mediating enzyme, which is a phosphatase, to remain active for long enough to deposit the minerals, that is, the uranium phosphate, together with cesium and strontium. So, the first series of experiments involved putting live cells in front of a gamma beam, a commercial irradiation gamma beam, in order to look at the effect of this treatment on both the cells and their phosphatase activity. And we also looked at purified phosphatase to see if it's possible to use an enzyme per se for this mineralisation reaction. What we found was that, as one would expect, the viability of the bacteria fell away very quickly and they were dead within eight hours. And likewise, the purified enzyme wasn't very radio stable. It lost activity within about the same period, eight to ten hours. But using whole cells, the activity of the enzyme was maintained for quite a long period at a total dose of more than 1,300 grey, and it still was fully active by the time and we'd finished the experiment. Now, actually, on its own, the enzyme was only about 80% active against the radio toxicity of the gamma source. But if it was supplemented with bacaptoethanol, that active does a radio protectant and gave complete radio resistance. So having established that the phosphatase enzyme is completely active in cells under irradiation to high dose, the next thing we did was to expose the cells to glycerol phosphate as the phosphate donor in the presence of uranium strontium and cesium. And it removed all of the elements, as one would expect, by incorporation of the strontium and cesium into the hydrogen urinal phosphate mineral matrix. The last set of experiments was to do this against a simulated waste containing radio-nuclide strontium and cesium, and those too were removed effectively into the biomuneral host hydrogen urinal phosphate. So taking these elements up into hydrogen urinal phosphate using real radioisotopes, the strontium was almost completely removed and the cesium was removed to the extent of about 50%, which saturated the hydrogen urinal phosphate host crystal, but of course that's being made continuously. So this approach has got the potential for long term decontamination on a continuous basis.