Citrobacter freundii: can have concentrations of uranium in their bodies 300 times higher than in the surrounding environment.Courtesy CDC
Looking toward the day uranium mines become depleted, Dr Masao Tanada is working on a sponge like material that can extract uranium from the ocean currents passing by Japan.

The world's oceans contain an estimated 4.5 billion tons of uranium, around 1,000 times the amount that is known to exist in uranium mines.
Japan is drawing up innovative plans to extract uranium from seawater in an attempt to end the country's reliance on imports for nuclear power stations. Telegraph.co.uk

This link to Next Big Future illustrates two proposals for mining the ocean for $720 trillion worth of Uranium.