Now, I know what you scientists and chemists are going to say. The bacteria aren't actually powering the robot. It's the a chemical reaction between the the copper and zinc electrodes that is creating the electrical charge. The acidity of the sauerkraut created by the bacteria and the electrolytes in the brine just create an environment that allows that reaction to take place.
That is true, the bacteria are making the robots move no more than I am making people let go. But we are both creating an environment in which both moving and letting go are possible. And that is the important point because this is a symbolic act. It's a metaphor.
That being said, I left the robot connected to the sauerkraut overnight, and when I woke up it had moved a few inches across the page. Pretty cool huh!