A tiny bacterium which feeds on polluted water to produce electricity has been discovered by scientists. A tablespoon of the bug generated more than half a volt in tests and researchers believe it could do even better. The bug, Shewanella putrifaciens IR -1, was found during the tests on bacteria that use metals as their source of the chemical energy to sustain life, reports The Sunday Telegraph.Dr. Byung Hong Kim of the Korea Institute of Science and Technology in Seoul, who led the research, said: "Metal-reducing bateria have gained attention only recently, though they have been widely observed in nature.