An ocean microbe may open a new frontier in the search for clean, renewable energy: In a sense, it makes hydrogen — a clean-burning fuel — out of the air.

The bug, a cyanobacterium called Cyanothece 51142, performs photosynthesis during the day and fixes nitrogen at night. Hydrogen is a byproduct of the nitrogen fixation process. And when you burn hydrogen, the main byproduct is water.