The original version of this story appeared in Quanta Magazine.
Prochlorococcus bacteria are so small that you’d have to line up around a thousand of them to match the thickness of a human thumbnail. The ocean seethes with them: The microbes are likely the most abundant photosynthetic organism on the planet, and they create a significant portion—10 percent to 20 percent—of the atmosphere’s oxygen. That means that life on Earth depends on the roughly 3 octillion (or 3 × 1027) tiny individual cells toiling away.
Biologists once thought of these organisms as isolated wanderers, adrift in an unfathomable vastness. But the Prochlorococcus population may be more connected than anyone could have