Think of it as electronic photosynthesis.
A team of researchers made up of scientists from two American universities envisions using a strain of bacteria as a power source. Specifically, the bacteria strain is Shewanella oneidensis. Its utility comes from its waste, which is electrons. The bacteria eats metal and spits out the excess electrons.
The researchers, from both Rice University and the University of Southern California, envision attaching the bacteria to the anode inside a fuel cell, with the result being the increase in available electrons for that fuel cell.
The big picture, according to the research team, is to create a fuel cell that will power itself—in other words, a robot.