The team studied bacteria living in marine sediments that power themselves by oxidizing hydrogen sulfide. Cells at the bottom live in a zone that is poor in oxygen but rich in hydrogen sulfide, and those at the top live in an area rich in oxygen but poor in hydrogen sulfide. The solution? They form long chains that transport individual electrons from the bottom to the top, completing the chemical reaction and generating life-sustaining energy. “You have feeder cells on one end and breather cells on the other, allowing the whole living cable to survive,” El-Naggar said.