Isn’t that neat? These bacteria, Shewanella and Geobacter, cut the middle-man, metabolism, and eat up energy directly from the electrons. As you know, metabolism is responsible for transforming food into sugars like glucose which is then used to power up our bodies. Ultimately, our need for energy can be summed up into one single fact: we get the energy from the same electrons these bacteria are feeding off, but we do it using the long way.
Extreme Tech explains how the metabolism works in a few neat sentences:
When it gets right down to it, everything you eat is ultimately converted or digested into single molecules of glucose. Without going into the complexities of respiration and metabolism (ATP!), these sugars have excess electrons — and the oxygen you breathe in really wants those electrons. By ferrying electrons from sugar to oxygen, a flow of electrons — i.e. energy — is created, which is then used to carry out various vital tasks around your body (triggering electrons, beating your heart, etc.)
It seems that life is able to always surprise us. If these bacteria seem so alien int he way they eat and poop electrons, how much stranger could real aliens be? Answer: possible not much more stranger as the laws of physics are the same everywhere. Good bacteria, good 😀